This document summarizes the analysis of Kepler photometry data for the exoplanet Kepler-7b. Key findings include:
1) The occultation depth is measured to be 44±5 ppm, translating to a Kepler geometric albedo of 0.32±0.03, the most precise value measured for an exoplanet.
2) The planetary orbital phase lightcurve is characterized with an amplitude of 42±4 ppm.
3) Atmospheric modeling finds it unlikely that the high albedo is due to a dominant thermal component. Two possible explanations are proposed: excess reflection from clouds/hazes, or depleted atmospheric sodium and potassium allowing Rayleigh scattering to dominate.
The absorption spectrum of cerium-doped calcium fluoride (CaF2:Ce2+) was observed at several temperatures. At low temperatures, the spectrum consists of transitions from the ground state to levels of the 4f configuration. A crystal field calculation shows that in CaF2's strong crystal field, the ground state of Ce2+ is a T2 level of the 4f5d configuration rather than the 4f configuration of the free ion. Measurements of the Zeeman effect confirm the T2 character of the ground state. The calculated energies and intensities of transitions from the ground state to 4f levels agree well with the observed optical absorption spectrum, especially in the near-infrared region.
X ray emission-from_strongly_asymmetric_circumstellar_material_in_the_remnant...Sérgio Sacani
This document summarizes a study of X-ray emission from circumstellar material (CSM) in the remnant of Kepler's supernova. The researchers used a statistical technique to isolate X-ray emission from CSM versus ejecta based on spectral characteristics. They found that most CSM is distributed along the bright north rim, but substantial amounts are also projected against the center, indicating a disk-like distribution of CSM from the progenitor system before the supernova. Hydrodynamic simulations support an AGB star companion as the origin of the asymmetric CSM. Quantitative analysis of magnesium emission identifies CSM and requires Kepler to have originated from a close binary system.
1) Astronomers observed comet Hale-Bopp at 30.7 AU from the Sun using the ESO 2.2m telescope in Chile on December 4, 2010.
2) They detected the comet with a total brightness of R=23.3 mag, corresponding to an absolute brightness of R(1,1,0)=8.3 mag.
3) The profile of the comet was star-like without any evidence of an extended coma or tail, indicating a cessation of matter production from the comet. However, the measured brightness corresponds to a reflecting surface area nine times smaller than three years prior, suggesting some low-level activity may still be occurring.
Modulations in the_radio_light_curve_of_the_typeiib_supernova_2001igSérgio Sacani
This document summarizes radio observations of the Type IIb supernova SN 2001ig made with the Australia Telescope Compact Array and Very Large Array over 700 days. The observations found periodic deviations from the standard model of radio light curves that are consistent with recurring density modulations in the circumstellar medium with a period of around 150 days. This provides evidence that the progenitor was a Wolf-Rayet star in a binary system with an eccentric 100 day orbit, causing regular build-up of circumstellar material. Such binary systems are thought to produce Type Ib/c supernovae through envelope stripping, linking these events to Type IIb supernovae.
1. The spectrum of the bright Kuiper Belt object 2005 FY9 is dominated by methane absorption features in the near-infrared region. However, the methane absorption lines are significantly broader than seen on any other solar system body, indicating unusually long optical path lengths through methane grains on 2005 FY9, estimated to be around 1 cm in size.
2. In addition to methane, the spectrum also shows clear evidence for ethane, which is expected to form from UV photolysis of methane. No evidence is found for nitrogen or carbon monoxide, both known to be present on Pluto.
3. The differences between 2005 FY9's spectrum and those of Pluto and 2003 UB313 are suggested
Bimolecular chemical reaction in two-dimensional Navier-Stokes flowFarid Ait-Chaalal, PhD
1) The document summarizes a PhD defense presentation on modeling bimolecular chemical reactions in two-dimensional fluid flows as a simplified model of chemical mixing in the stratosphere.
2) The presentation examines an infinitely fast chemical reaction between chemicals A and B to form C, which is controlled by diffusion.
3) Numerical simulations are conducted for various diffusion coefficients in a periodic flow domain to study how the chemical production depends on tracer diffusion and can be related to the Lagrangian straining properties of the flow.
This document is a sample question paper for Class XII Physics Theory Term II Session 2021-22. It has 3 sections - Section A has 2 mark questions, Section B has 3 mark questions, and Section C has a 5 mark case study based question. The paper tests concepts related to semiconductor physics, Bohr model, photoelectric effect, devices, electromagnetic waves, optics, spectroscopy, and more. Students are required to attempt all questions in the allotted 2 hours while using log tables but not calculators.
This document summarizes star forming regions in the constellation of Cepheus. It describes several giant molecular cloud complexes located at various distances from the Sun, ranging from clouds within 500 pc to regions associated with the Perseus spiral arm at 2-3 kpc. Key regions discussed include the Cepheus Flare clouds below 500 pc, three OB associations (Cep OB2, Cep OB3, Cep OB4) located 600-900 pc away, and the well-known high mass star forming region S 140 located at 900 pc. Tables list molecular clouds and young stars identified in the Cepheus region. Maps show the distribution of clouds, extinction, and pre-main sequence stars across Cepheus.
The absorption spectrum of cerium-doped calcium fluoride (CaF2:Ce2+) was observed at several temperatures. At low temperatures, the spectrum consists of transitions from the ground state to levels of the 4f configuration. A crystal field calculation shows that in CaF2's strong crystal field, the ground state of Ce2+ is a T2 level of the 4f5d configuration rather than the 4f configuration of the free ion. Measurements of the Zeeman effect confirm the T2 character of the ground state. The calculated energies and intensities of transitions from the ground state to 4f levels agree well with the observed optical absorption spectrum, especially in the near-infrared region.
X ray emission-from_strongly_asymmetric_circumstellar_material_in_the_remnant...Sérgio Sacani
This document summarizes a study of X-ray emission from circumstellar material (CSM) in the remnant of Kepler's supernova. The researchers used a statistical technique to isolate X-ray emission from CSM versus ejecta based on spectral characteristics. They found that most CSM is distributed along the bright north rim, but substantial amounts are also projected against the center, indicating a disk-like distribution of CSM from the progenitor system before the supernova. Hydrodynamic simulations support an AGB star companion as the origin of the asymmetric CSM. Quantitative analysis of magnesium emission identifies CSM and requires Kepler to have originated from a close binary system.
1) Astronomers observed comet Hale-Bopp at 30.7 AU from the Sun using the ESO 2.2m telescope in Chile on December 4, 2010.
2) They detected the comet with a total brightness of R=23.3 mag, corresponding to an absolute brightness of R(1,1,0)=8.3 mag.
3) The profile of the comet was star-like without any evidence of an extended coma or tail, indicating a cessation of matter production from the comet. However, the measured brightness corresponds to a reflecting surface area nine times smaller than three years prior, suggesting some low-level activity may still be occurring.
Modulations in the_radio_light_curve_of_the_typeiib_supernova_2001igSérgio Sacani
This document summarizes radio observations of the Type IIb supernova SN 2001ig made with the Australia Telescope Compact Array and Very Large Array over 700 days. The observations found periodic deviations from the standard model of radio light curves that are consistent with recurring density modulations in the circumstellar medium with a period of around 150 days. This provides evidence that the progenitor was a Wolf-Rayet star in a binary system with an eccentric 100 day orbit, causing regular build-up of circumstellar material. Such binary systems are thought to produce Type Ib/c supernovae through envelope stripping, linking these events to Type IIb supernovae.
1. The spectrum of the bright Kuiper Belt object 2005 FY9 is dominated by methane absorption features in the near-infrared region. However, the methane absorption lines are significantly broader than seen on any other solar system body, indicating unusually long optical path lengths through methane grains on 2005 FY9, estimated to be around 1 cm in size.
2. In addition to methane, the spectrum also shows clear evidence for ethane, which is expected to form from UV photolysis of methane. No evidence is found for nitrogen or carbon monoxide, both known to be present on Pluto.
3. The differences between 2005 FY9's spectrum and those of Pluto and 2003 UB313 are suggested
Bimolecular chemical reaction in two-dimensional Navier-Stokes flowFarid Ait-Chaalal, PhD
1) The document summarizes a PhD defense presentation on modeling bimolecular chemical reactions in two-dimensional fluid flows as a simplified model of chemical mixing in the stratosphere.
2) The presentation examines an infinitely fast chemical reaction between chemicals A and B to form C, which is controlled by diffusion.
3) Numerical simulations are conducted for various diffusion coefficients in a periodic flow domain to study how the chemical production depends on tracer diffusion and can be related to the Lagrangian straining properties of the flow.
This document is a sample question paper for Class XII Physics Theory Term II Session 2021-22. It has 3 sections - Section A has 2 mark questions, Section B has 3 mark questions, and Section C has a 5 mark case study based question. The paper tests concepts related to semiconductor physics, Bohr model, photoelectric effect, devices, electromagnetic waves, optics, spectroscopy, and more. Students are required to attempt all questions in the allotted 2 hours while using log tables but not calculators.
This document summarizes star forming regions in the constellation of Cepheus. It describes several giant molecular cloud complexes located at various distances from the Sun, ranging from clouds within 500 pc to regions associated with the Perseus spiral arm at 2-3 kpc. Key regions discussed include the Cepheus Flare clouds below 500 pc, three OB associations (Cep OB2, Cep OB3, Cep OB4) located 600-900 pc away, and the well-known high mass star forming region S 140 located at 900 pc. Tables list molecular clouds and young stars identified in the Cepheus region. Maps show the distribution of clouds, extinction, and pre-main sequence stars across Cepheus.
This document summarizes the final results from the HERMES experiment on hadronization in nuclear environments. Key findings include:
- Hadron multiplicity ratios increase with the kinematic variable ν and decrease with higher z values, showing a strong dependence on atomic mass number.
- Analyses were performed in one and two dimensions as functions of variables like ν, z, pT2, and Q2. Nuclear broadening of pT2 was observed, related to the Cronin effect.
- Nuclear attenuation was found to depend substantially on an estimation of hadron formation length, decreasing as formation length increased.
- The results provide insights into parton energy loss and hadron formation mechanisms in nuclear matter
The first hyper_luminous_infrared_galaxy_discovered_by_wiseSérgio Sacani
This document summarizes the discovery of WISE J181417.29+341224.9 (WISE 1814+3412), the first hyper-luminous infrared galaxy (LIR > 1013 L⊙) discovered by the Wide-field Infrared Survey Explorer (WISE). Follow-up images of WISE 1814+3412 revealed four nearby sources - a QSO, two Lyman Break Galaxies at z=2.45, and an M dwarf star. The brighter LBG dominates the bolometric emission of WISE 1814+3412 and has a star formation rate of ~300M⊙ yr−1, accounting for <10% of the total luminosity. An obscured
Helen Cleugh_Near-real-time measurement of carbon dioxide, water and energy f...TERN Australia
This document discusses using flux tower and other observational data to constrain land surface models and determine carbon and water budgets across Australia. It describes how the OzFlux network provides carbon dioxide and water flux measurements from different ecosystems. These flux measurements have been used to test and improve land surface models and reduce uncertainty in estimates of net primary production for Australia. Integrating these observational constraints into the BIOS2 modeling framework has provided insights into Australia's dynamic carbon and water cycles at continental scales.
Investigating the nuclear_activity_of_ngc1672Sérgio Sacani
1) The document investigates the nuclear activity of the barred spiral galaxy NGC 1672 using X-ray data from Chandra and XMM-Newton, as well as optical data from Hubble and infrared data from Spitzer.
2) It detects 28 X-ray sources within NGC 1672, with nine being ultraluminous X-ray sources located at the ends of the galaxy's bar.
3) For the first time, it shows NGC 1672 possesses a hard nuclear X-ray source surrounded by an X-ray bright circumnuclear star-forming ring, which dominates the central X-ray emission of the galaxy. The data indicates the nuclear source is a low-luminosity active gal
This document discusses two key materials issues in semiconductor quantum dots: 1) The local nano-chemistry of quantum dot molecules (QDMs), specifically that pit bases within QDMs have the highest germanium concentration at 58% germanium based on auger electron spectroscopy measurements. 2) The structural damage and recovery from focused ion beam (FIB) implantation in silicon, finding that FIB implantation causes more damage than broad beam implantation but allows for better recovery upon annealing.
Assessment of Activity Concentration of The Naturally Occurring Radioactive M...IOSR Journals
The activity concentrations of potassium, Radium and thorium in soil samples from a mining site in yankandutse, Kaduna north western Nigeria were measured using gamma ray spectroscopy method. Activity concentration of potassium, Radium and thorium were determined. The activity concentrations of 40K, 226Ra and 232Th, respectively in Bq kg-1 in the soil samples ranged as follows: K-40 196.11±2.02 to 553.03±1.08 with average of 382.01, Ra-226 .1506±.03 to 5.67±.03 with average of 2.08 and Th-232 18.13±3.19 to 73.09±1.59 with average activity concentrations of 47.23 .The mean activity concentration of potassium and radium are below average but for thorium the activity concentration is above average.
This document discusses using advanced computational methods beyond density functional theory (DFT) to more accurately model electron-phonon coupling (EPC) in graphene. It finds that the GW approximation provides a better description of phonon dispersions and EPC than DFT. Hybrid functionals can also reproduce GW results if the amount of nonlocal exchange is tuned. The EPC is found to decrease with doping as screening becomes stronger. Experimental evidence generally agrees with the computational results.
The document summarizes research analyzing amino acids extracted from the Murchison meteorite. Key findings include:
1) Individual amino acids from Murchison were enriched in the heavy nitrogen isotope 15N, confirming an extraterrestrial source for the previously observed excess of left-handed amino acid enantiomers in the meteorite.
2) The d15N values of most amino acids analyzed fell outside the range typically seen in terrestrial organic matter, further supporting an extraterrestrial origin.
3) Differences in d15N values between some amino acids suggest they may have had distinct precursor sources or undergone unique formation or decomposition processes.
4) Overall, the results provide strong evidence that the observed asymmetry in
Solid-state electrolytes exhibit good safety and stability, and are promising to replace current organic liquid electrolytes in rechargeable battery applications. In this talk, we will present our efforts at developing scalable first principles techniques to design novel solid-state electrolytes. Using the recently discovered Li10GeP2S12 lithium super ionic conductor as an example, we will discuss how various properties of interest in a solid-state electrolyte can be predicted using first principles calculations. We will show how the application of these first principles techniques has suggested two chemical modifications, Li10SiP2S12 and Li10SnP2S12, that retains the excellent Li+ conductivity of Li10GeP2S12 at a significantly reduced cost. These modifications have recently been synthesized, and the measured Li+ conductivities are in excellent agreement with our first principles predictions. We will conclude with a demonstration of how relatively expensive first principles calculations can be intelligently scaled and combined with topological analysis to be a useful screening tool for novel solid-state electrolytes.
1) Wavelength shifters are fluorescent chemicals that can absorb ultraviolet Cherenkov photons and re-emit them at longer wavelengths detectable by photomultiplier tubes, improving light yield.
2) The document studies potential wavelength shifters for use in the Sudbury Neutrino Observatory heavy water Cherenkov detector to increase detection efficiency.
3) It tests several water-soluble wavelength shifter candidates, measuring their optical properties, stability, and compatibility with detector materials to find suitable options for deploying in the detector to boost the Cherenkov signal.
The document summarizes research analyzing amino acids extracted from the Murchison meteorite. Key findings include:
1) Amino acids from the meteorite were enriched in the heavy nitrogen isotope 15N, indicating an extraterrestrial source rather than terrestrial contamination.
2) Individual amino acid enantiomers had similar d15N values, implying a single homogeneous source, possibly interstellar clouds.
3) The findings provide further evidence that the excess of left-handed amino acids in the meteorite, and potentially on the early Earth, had an extraterrestrial origin.
High resolution image_of_a_cometary_globule_in_helix_nebulaSérgio Sacani
This document summarizes high-resolution observations of a cometary globule in the Helix Nebula made using the IRAM interferometer and SOFI infrared camera. The observations image the globule in the CO J=1-0 line and H2 v=1-0 S(1) line. They reveal that the head of the globule appears as a narrow peak in CO emission outlined by limb-brightened H2 emission facing the central star. Emission from both molecules extends into the tail region, providing new constraints on globule structure and evolution.
Rings in the_haloes_of_planetary_nebulaeSérgio Sacani
This document presents the discovery of ring structures in the haloes of eight planetary nebulae, tripling the number known to have such rings. The rings are analyzed using image processing techniques to enhance their visibility. They find ring spacings range from less than 0.01 pc to 0.06 pc. This suggests ring spacing increases with time after the asymptotic giant branch phase. The properties of the rings support predictions of dust-driven wind instability models of mass loss but do not rule out other models. Analyzing the new detections provides insights into mass modulation processes late in stellar evolution.
1) Laser operation was achieved in a neodymium-doped scandium silicate (Nd:SSO) crystal based on the 4F3/2→4I9/2 transition of Nd3+ ions. Pumped by an 808 nm laser diode, laser emission at 914 nm was obtained with an output power of 581 mW.
2) Spectroscopic measurements of the Nd:SSO crystal found absorption and emission cross sections of 1.69×10-20 cm2 and 1.13×10-20 cm2 respectively at relevant wavelengths. The gain cross section was estimated to allow lasing inversion at β=0.25.
3) Compared to other
Keck ii observations_of_hemispherical_differences_in_h2o2_on_europaSérgio Sacani
This summary analyzes observations from the Keck II telescope that detected varying amounts of hydrogen peroxide on Europa's surface. Observations over four nights found comparable amounts (~0.13%) of H2O2 on the leading hemisphere, lower amounts (~0.04%) on the anti-Jovian and sub-Jovian hemispheres, and almost none on the trailing hemisphere. This suggests the maximum concentration is found on the leading side, with lower amounts elsewhere, requiring revisions to estimates of Europa's total oxidant abundance and delivery to its subsurface ocean.
This document summarizes Hubble Space Telescope ultraviolet spectroscopy of four white dwarfs known to accrete planetary debris. The spectra reveal absorption lines from a variety of metals including carbon, oxygen, aluminum, silicon, phosphorus, sulfur, chromium, iron, and nickel. Combined with optical data, between five and eleven different metals are detected in each white dwarf, indicating substantial chemical diversity in the accreted planetary debris. The abundances observed provide insights into the composition and origin of the debris, with some debris resembling bulk Earth composition and others showing evidence of melting and differentiation.
This document summarizes the key findings from fitting experimental data on radiation-induced absorption in optical fibers to fractal kinetic models. The models provide better fits than classical kinetic solutions, with fitting parameters suggesting a transition from classical to fractal behavior at lower dose rates. Specifically:
1) Fractal kinetic models with stretched exponential solutions provided excellent fits to the data over four orders of magnitude in dose rate.
2) Parameters like the rate coefficient and saturation value varied with dose rate as predicted by the fractal models, indicating a transition from classical to fractal kinetics.
3) Including additional defect populations improved fits and supported the fractal kinetics interpretation of the data.
Structural aspect on carbon dioxide capture in nanotubesIJRES Journal
In this work we reported the carbon dioxide adsorption (CO2) in six different nanostructures in order
to investigate the capturing capacity of the materials at nanoscale. Here we have considered the three different
nanotubes including zinc oxide nanotube (ZnONT), silicon carbide nanotube (SiCNT) and single walled carbon
nanotube (SWCNT). Three different chiralities such as zigzag (9,0), armchair (5,5) and chiral (6,4) having
approximately same diameter are analyzed. The adsorption binding energy values under various cases are
estimated with density functional theory (DFT). We observed CO2 molecule chemisorbed on ZnONT and
SiCNT’s whereas the physisorption is predominant in CNT. To investigate the structural aspect, the tubes with
defects are studied and compared with defect free tubes. We have also analyzed the electrical properties of tubes
from HOMO, LUMO energies. Our results reveal the defected structure enhance the CO2 capture and is
predicted to be a potential candidate for environmental applications.
Supermassive black holes do not correlate with galaxy disks or pseudobulgesSérgio Sacani
The document summarizes research finding that supermassive black holes do not correlate with galaxy disks or pseudobulges. It finds that black hole mass correlates strongly with classical bulges, which are indistinguishable from elliptical galaxies, but correlates little or not at all with pseudobulges or disks. This suggests two different modes of black hole feeding - rapid growth driven by mergers for classical bulges, and slower local growth for pseudobulges and disks.
The document summarizes the first observations of the magnetic Kelvin-Helmholtz instability in the solar corona using high-resolution imaging from NASA's Solar Dynamics Observatory. The instability was detected on the northern flank of a fast coronal mass ejection, appearing as substructures or waves against the darker coronal background. Analysis found the observed phase speed of the waves to be about half the speed of the ejecta front, validating theories of the non-linear dynamics of this instability in magnetized plasma environments. The findings provide new insights into fundamental plasma processes in the solar atmosphere and solar-terrestrial system.
Zero outward flow velocity for plasma in a heliosheath transition layeSérgio Sacani
The document summarizes recent findings from Voyager 1, which has been traveling through the heliosheath region between the solar wind termination shock and the heliopause boundary. Key findings include:
1) The radial velocity of plasma detected by Voyager 1 has decreased nearly linearly from 70 km/s to 0 km/s over the past 3 years and has remained at 0 km/s for the past 8 months, indicating Voyager 1 has entered a transition layer with zero radial flow.
2) This transition layer was not predicted by models and contradicts expectations of an abrupt discontinuity at the heliopause.
3) Analysis of plasma velocity measurements suggests Voyager 1 may have crossed the he
This document summarizes the final results from the HERMES experiment on hadronization in nuclear environments. Key findings include:
- Hadron multiplicity ratios increase with the kinematic variable ν and decrease with higher z values, showing a strong dependence on atomic mass number.
- Analyses were performed in one and two dimensions as functions of variables like ν, z, pT2, and Q2. Nuclear broadening of pT2 was observed, related to the Cronin effect.
- Nuclear attenuation was found to depend substantially on an estimation of hadron formation length, decreasing as formation length increased.
- The results provide insights into parton energy loss and hadron formation mechanisms in nuclear matter
The first hyper_luminous_infrared_galaxy_discovered_by_wiseSérgio Sacani
This document summarizes the discovery of WISE J181417.29+341224.9 (WISE 1814+3412), the first hyper-luminous infrared galaxy (LIR > 1013 L⊙) discovered by the Wide-field Infrared Survey Explorer (WISE). Follow-up images of WISE 1814+3412 revealed four nearby sources - a QSO, two Lyman Break Galaxies at z=2.45, and an M dwarf star. The brighter LBG dominates the bolometric emission of WISE 1814+3412 and has a star formation rate of ~300M⊙ yr−1, accounting for <10% of the total luminosity. An obscured
Helen Cleugh_Near-real-time measurement of carbon dioxide, water and energy f...TERN Australia
This document discusses using flux tower and other observational data to constrain land surface models and determine carbon and water budgets across Australia. It describes how the OzFlux network provides carbon dioxide and water flux measurements from different ecosystems. These flux measurements have been used to test and improve land surface models and reduce uncertainty in estimates of net primary production for Australia. Integrating these observational constraints into the BIOS2 modeling framework has provided insights into Australia's dynamic carbon and water cycles at continental scales.
Investigating the nuclear_activity_of_ngc1672Sérgio Sacani
1) The document investigates the nuclear activity of the barred spiral galaxy NGC 1672 using X-ray data from Chandra and XMM-Newton, as well as optical data from Hubble and infrared data from Spitzer.
2) It detects 28 X-ray sources within NGC 1672, with nine being ultraluminous X-ray sources located at the ends of the galaxy's bar.
3) For the first time, it shows NGC 1672 possesses a hard nuclear X-ray source surrounded by an X-ray bright circumnuclear star-forming ring, which dominates the central X-ray emission of the galaxy. The data indicates the nuclear source is a low-luminosity active gal
This document discusses two key materials issues in semiconductor quantum dots: 1) The local nano-chemistry of quantum dot molecules (QDMs), specifically that pit bases within QDMs have the highest germanium concentration at 58% germanium based on auger electron spectroscopy measurements. 2) The structural damage and recovery from focused ion beam (FIB) implantation in silicon, finding that FIB implantation causes more damage than broad beam implantation but allows for better recovery upon annealing.
Assessment of Activity Concentration of The Naturally Occurring Radioactive M...IOSR Journals
The activity concentrations of potassium, Radium and thorium in soil samples from a mining site in yankandutse, Kaduna north western Nigeria were measured using gamma ray spectroscopy method. Activity concentration of potassium, Radium and thorium were determined. The activity concentrations of 40K, 226Ra and 232Th, respectively in Bq kg-1 in the soil samples ranged as follows: K-40 196.11±2.02 to 553.03±1.08 with average of 382.01, Ra-226 .1506±.03 to 5.67±.03 with average of 2.08 and Th-232 18.13±3.19 to 73.09±1.59 with average activity concentrations of 47.23 .The mean activity concentration of potassium and radium are below average but for thorium the activity concentration is above average.
This document discusses using advanced computational methods beyond density functional theory (DFT) to more accurately model electron-phonon coupling (EPC) in graphene. It finds that the GW approximation provides a better description of phonon dispersions and EPC than DFT. Hybrid functionals can also reproduce GW results if the amount of nonlocal exchange is tuned. The EPC is found to decrease with doping as screening becomes stronger. Experimental evidence generally agrees with the computational results.
The document summarizes research analyzing amino acids extracted from the Murchison meteorite. Key findings include:
1) Individual amino acids from Murchison were enriched in the heavy nitrogen isotope 15N, confirming an extraterrestrial source for the previously observed excess of left-handed amino acid enantiomers in the meteorite.
2) The d15N values of most amino acids analyzed fell outside the range typically seen in terrestrial organic matter, further supporting an extraterrestrial origin.
3) Differences in d15N values between some amino acids suggest they may have had distinct precursor sources or undergone unique formation or decomposition processes.
4) Overall, the results provide strong evidence that the observed asymmetry in
Solid-state electrolytes exhibit good safety and stability, and are promising to replace current organic liquid electrolytes in rechargeable battery applications. In this talk, we will present our efforts at developing scalable first principles techniques to design novel solid-state electrolytes. Using the recently discovered Li10GeP2S12 lithium super ionic conductor as an example, we will discuss how various properties of interest in a solid-state electrolyte can be predicted using first principles calculations. We will show how the application of these first principles techniques has suggested two chemical modifications, Li10SiP2S12 and Li10SnP2S12, that retains the excellent Li+ conductivity of Li10GeP2S12 at a significantly reduced cost. These modifications have recently been synthesized, and the measured Li+ conductivities are in excellent agreement with our first principles predictions. We will conclude with a demonstration of how relatively expensive first principles calculations can be intelligently scaled and combined with topological analysis to be a useful screening tool for novel solid-state electrolytes.
1) Wavelength shifters are fluorescent chemicals that can absorb ultraviolet Cherenkov photons and re-emit them at longer wavelengths detectable by photomultiplier tubes, improving light yield.
2) The document studies potential wavelength shifters for use in the Sudbury Neutrino Observatory heavy water Cherenkov detector to increase detection efficiency.
3) It tests several water-soluble wavelength shifter candidates, measuring their optical properties, stability, and compatibility with detector materials to find suitable options for deploying in the detector to boost the Cherenkov signal.
The document summarizes research analyzing amino acids extracted from the Murchison meteorite. Key findings include:
1) Amino acids from the meteorite were enriched in the heavy nitrogen isotope 15N, indicating an extraterrestrial source rather than terrestrial contamination.
2) Individual amino acid enantiomers had similar d15N values, implying a single homogeneous source, possibly interstellar clouds.
3) The findings provide further evidence that the excess of left-handed amino acids in the meteorite, and potentially on the early Earth, had an extraterrestrial origin.
High resolution image_of_a_cometary_globule_in_helix_nebulaSérgio Sacani
This document summarizes high-resolution observations of a cometary globule in the Helix Nebula made using the IRAM interferometer and SOFI infrared camera. The observations image the globule in the CO J=1-0 line and H2 v=1-0 S(1) line. They reveal that the head of the globule appears as a narrow peak in CO emission outlined by limb-brightened H2 emission facing the central star. Emission from both molecules extends into the tail region, providing new constraints on globule structure and evolution.
Rings in the_haloes_of_planetary_nebulaeSérgio Sacani
This document presents the discovery of ring structures in the haloes of eight planetary nebulae, tripling the number known to have such rings. The rings are analyzed using image processing techniques to enhance their visibility. They find ring spacings range from less than 0.01 pc to 0.06 pc. This suggests ring spacing increases with time after the asymptotic giant branch phase. The properties of the rings support predictions of dust-driven wind instability models of mass loss but do not rule out other models. Analyzing the new detections provides insights into mass modulation processes late in stellar evolution.
1) Laser operation was achieved in a neodymium-doped scandium silicate (Nd:SSO) crystal based on the 4F3/2→4I9/2 transition of Nd3+ ions. Pumped by an 808 nm laser diode, laser emission at 914 nm was obtained with an output power of 581 mW.
2) Spectroscopic measurements of the Nd:SSO crystal found absorption and emission cross sections of 1.69×10-20 cm2 and 1.13×10-20 cm2 respectively at relevant wavelengths. The gain cross section was estimated to allow lasing inversion at β=0.25.
3) Compared to other
Keck ii observations_of_hemispherical_differences_in_h2o2_on_europaSérgio Sacani
This summary analyzes observations from the Keck II telescope that detected varying amounts of hydrogen peroxide on Europa's surface. Observations over four nights found comparable amounts (~0.13%) of H2O2 on the leading hemisphere, lower amounts (~0.04%) on the anti-Jovian and sub-Jovian hemispheres, and almost none on the trailing hemisphere. This suggests the maximum concentration is found on the leading side, with lower amounts elsewhere, requiring revisions to estimates of Europa's total oxidant abundance and delivery to its subsurface ocean.
This document summarizes Hubble Space Telescope ultraviolet spectroscopy of four white dwarfs known to accrete planetary debris. The spectra reveal absorption lines from a variety of metals including carbon, oxygen, aluminum, silicon, phosphorus, sulfur, chromium, iron, and nickel. Combined with optical data, between five and eleven different metals are detected in each white dwarf, indicating substantial chemical diversity in the accreted planetary debris. The abundances observed provide insights into the composition and origin of the debris, with some debris resembling bulk Earth composition and others showing evidence of melting and differentiation.
This document summarizes the key findings from fitting experimental data on radiation-induced absorption in optical fibers to fractal kinetic models. The models provide better fits than classical kinetic solutions, with fitting parameters suggesting a transition from classical to fractal behavior at lower dose rates. Specifically:
1) Fractal kinetic models with stretched exponential solutions provided excellent fits to the data over four orders of magnitude in dose rate.
2) Parameters like the rate coefficient and saturation value varied with dose rate as predicted by the fractal models, indicating a transition from classical to fractal kinetics.
3) Including additional defect populations improved fits and supported the fractal kinetics interpretation of the data.
Structural aspect on carbon dioxide capture in nanotubesIJRES Journal
In this work we reported the carbon dioxide adsorption (CO2) in six different nanostructures in order
to investigate the capturing capacity of the materials at nanoscale. Here we have considered the three different
nanotubes including zinc oxide nanotube (ZnONT), silicon carbide nanotube (SiCNT) and single walled carbon
nanotube (SWCNT). Three different chiralities such as zigzag (9,0), armchair (5,5) and chiral (6,4) having
approximately same diameter are analyzed. The adsorption binding energy values under various cases are
estimated with density functional theory (DFT). We observed CO2 molecule chemisorbed on ZnONT and
SiCNT’s whereas the physisorption is predominant in CNT. To investigate the structural aspect, the tubes with
defects are studied and compared with defect free tubes. We have also analyzed the electrical properties of tubes
from HOMO, LUMO energies. Our results reveal the defected structure enhance the CO2 capture and is
predicted to be a potential candidate for environmental applications.
Supermassive black holes do not correlate with galaxy disks or pseudobulgesSérgio Sacani
The document summarizes research finding that supermassive black holes do not correlate with galaxy disks or pseudobulges. It finds that black hole mass correlates strongly with classical bulges, which are indistinguishable from elliptical galaxies, but correlates little or not at all with pseudobulges or disks. This suggests two different modes of black hole feeding - rapid growth driven by mergers for classical bulges, and slower local growth for pseudobulges and disks.
The document summarizes the first observations of the magnetic Kelvin-Helmholtz instability in the solar corona using high-resolution imaging from NASA's Solar Dynamics Observatory. The instability was detected on the northern flank of a fast coronal mass ejection, appearing as substructures or waves against the darker coronal background. Analysis found the observed phase speed of the waves to be about half the speed of the ejecta front, validating theories of the non-linear dynamics of this instability in magnetized plasma environments. The findings provide new insights into fundamental plasma processes in the solar atmosphere and solar-terrestrial system.
Zero outward flow velocity for plasma in a heliosheath transition layeSérgio Sacani
The document summarizes recent findings from Voyager 1, which has been traveling through the heliosheath region between the solar wind termination shock and the heliopause boundary. Key findings include:
1) The radial velocity of plasma detected by Voyager 1 has decreased nearly linearly from 70 km/s to 0 km/s over the past 3 years and has remained at 0 km/s for the past 8 months, indicating Voyager 1 has entered a transition layer with zero radial flow.
2) This transition layer was not predicted by models and contradicts expectations of an abrupt discontinuity at the heliopause.
3) Analysis of plasma velocity measurements suggests Voyager 1 may have crossed the he
Brazil has a long history in astronomy dating back to the 17th century when the first astronomical observatory was founded in Recife. Astronomy grew slowly over the centuries and accelerated in recent decades due to new funding, graduate programs, and infrastructure like the OPD telescope. Brazil now participates in international observatories like Gemini, SOAR, and CFHT to give its astronomers access to a wide range of telescopes. The national astronomical community has grown rapidly to over 650 scientists spread across 46 institutions nationwide. Brazil also develops astronomical instrumentation through organizations like LNA and INPE.
A closely packed system of low mass, low-density planets transiting kepler-11Sérgio Sacani
The document summarizes the discovery of six transiting exoplanets orbiting the star Kepler-11. Photometry from the Kepler spacecraft revealed periodic dips in the star's brightness consistent with multiple transiting planets. Six planetary candidates were identified, with orbital periods ranging from 10 to 47 days for the inner five planets. Radial velocity measurements confirmed the planetary nature of the five inner planets and allowed for mass estimates. The outermost sixth planet was also validated as a planet. Analysis of the transit times, durations and depths provided insights into the properties, dynamics, and stability of this unique six-planet system.
Titan is a moon of Saturn with a dense nitrogen-methane atmosphere that allows for organic chemistry on its surface. The Cassini mission and Huygens probe provided data about Titan's surface, which appears to have liquid methane and ethane at some point in its history. Evidence suggests Titan has an internal liquid water layer that allows geological activity like cryovolcanism, and that ammonia plays a key role in maintaining this layer and Titan's evolution.
A mechanism for the present day creation of a new class of black holesSérgio Sacani
This document proposes a mechanism for the formation of new classes of black holes with masses less than 2 solar masses (substellar mass dwarf black holes or DBHs) in the expanding gases of astrophysical phenomena like supernovae. It presents a heuristic method for determining gravitational instability and collapse in non-spherical matter distributions, which could allow detection of regions in simulation data that form DBHs. Applying this method to a Type II supernova simulation, the authors found regions with densities and masses close to what is needed to form DBHs. Future work will estimate the mass spectrum and abundances of ejected and bound DBHs.
Polarized gamma ray emission from the galactic black hole cygnus x-1Sérgio Sacani
Polarized gamma-ray emission was measured from the black hole binary system Cygnus X-1 using the INTEGRAL/IBIS telescope. Spectral modeling revealed two emission components: 250-400 keV emission consistent with Compton scattering and weakly polarized; 400 keV - 2 MeV emission from a power law component that is strongly polarized at 67%, likely from synchrotron emission in the jet. The polarization angle of 140° is significantly different than the radio jet angle, as seen in other jet sources.
MUSE sneaks a peek at extreme ram-pressure stripping events. I. A kinematic s...Sérgio Sacani
- MUSE observations of the galaxy ESO137-001 reveal an extended gaseous tail over 30 kpc long traced by H-alpha emission, providing evidence of an extreme ram pressure stripping event as the galaxy falls into the massive Norma galaxy cluster.
- Analysis of the H-alpha kinematics and stellar velocity field show that ram pressure has removed the interstellar medium from the outer disk while the primary tail is still fed by gas from the galaxy center, with gravitational interactions not appearing to be the main mechanism of gas removal.
- The stripped gas retains evidence of the disk's rotational velocity out to around 20 kpc downstream, indicating the galaxy is moving radially along the plane of the sky, while
A massive protocluster of galaxies at a redshift of z<5.3Sérgio Sacani
This document describes the discovery of a massive protocluster of galaxies located approximately 1 billion years after the Big Bang (redshift of z=5.3). The protocluster contains overdense regions of massive galaxies extending over 13 megaparsecs. It contains an extremely luminous starburst galaxy with large molecular gas reserves and a luminous quasar. Together, these objects place a minimum total mass of over 4×1011 solar masses in this early cluster, consistent with cosmological simulations of the earliest galaxy clusters. This discovery provides evidence for the hierarchical formation of massive structures in the early universe.
The extremely high albedo of LTT 9779 b revealed by CHEOPSSérgio Sacani
Optical secondary eclipse measurements of small planets can provide a wealth of information about the reflective properties
of these worlds, but the measurements are particularly challenging to attain because of their relatively shallow depth. If such signals
can be detected and modeled, however, they can provide planetary albedos, thermal characteristics, and information on absorbers in
the upper atmosphere.
Aims. We aim to detect and characterize the optical secondary eclipse of the planet LTT 9779 b using the CHaracterising ExOPlanet
Satellite (CHEOPS) to measure the planetary albedo and search for the signature of atmospheric condensates.
Methods. We observed ten secondary eclipses of the planet with CHEOPS. We carefully analyzed and detrended the light curves using
three independent methods to perform the final astrophysical detrending and eclipse model fitting of the individual and combined light
curves.
Results. Each of our analysis methods yielded statistically similar results, providing a robust detection of the eclipse of LTT 9779 b
with a depth of 115±24 ppm. This surprisingly large depth provides a geometric albedo for the planet of 0.80+0.10
−0.17, consistent with
estimates of radiative-convective models. This value is similar to that of Venus in our own Solar System. When combining the eclipse
from CHEOPS with the measurements from TESS and Spitzer, our global climate models indicate that LTT 9779 b likely has a super
metal-rich atmosphere, with a lower limit of 400× solar being found, and the presence of silicate clouds. The observations also reveal
hints of optical eclipse depth variability, but these have yet to be confirmed.
Conclusions. The results found here in the optical when combined with those in the near-infrared provide the first steps toward
understanding the atmospheric structure and physical processes of ultrahot Neptune worlds that inhabit the Neptune desert.
Inference of homogeneous_clouds_in_an_exoplanet_atmosphereSérgio Sacani
1) New visible and infrared observations of the exoplanet Kepler-7b were analyzed to determine its atmospheric properties and detect the presence of clouds.
2) The observations found a westward shift in Kepler-7b's optical phase curve and placed upper limits on its thermal emission that remained undetected in Spitzer bandpasses.
3) The data suggests Kepler-7b has optically thick, high-altitude clouds located west of the substellar point, composed possibly of silicates. The clouds help explain Kepler-7b's unusually high geometric albedo and visible flux that cannot be attributed to thermal emission or molecular hydrogen scattering alone.
Did a short gamma ray burst cause the AD 774-5 carbon spike?maltesk
Something happened on Earth between 774-775 AD that caused increased levels of carbon-14 in the atmosphere. This could have been caused by a short gamma-ray burst from the merger of two neutron stars or black holes within a few thousand light years. It is also possible it was caused by an unusually powerful solar flare or coronal mass ejection from the Sun, around 100 times stronger than anything observed today but within the range of possible flares seen on other stars. Determining the exact cause would help understand the rates of these events and prepare for the possibility of similar occurrences in the future.
The central star_of_the_planetary_nebula_ngc_6537Sérgio Sacani
1) HST images of the planetary nebula NGC 6537 fail to detect its central star, placing an upper limit on its magnitude of fainter than 22.4.
2) This limit is used to derive a lower limit for the star's temperature of at least 500,000 K based on Zanstra temperature analysis.
3) The energy balance temperature method, which does not require direct observation of the star, yields a temperature consistent with 500,000 K, as does the ionization state of the nebula.
First discovery of_a_magnetic_field_in_a_main_sequence_delta_scuti_star_the_k...Sérgio Sacani
Coralie Neiner do Laboratory for Space Studies and Astrophysics Instrumentation, LESIA (CNRS/Observatoire de Paris/UPMC/Université Paris Diderot) e Patricia Lampens (Royual OIbservatory of Belgium), descobriram a primeira estrela magnética do tipo delta Scuti, através de observações espectropolarimétricas, realizadas com o telescópio CFHT. As estrelas do tipo delta Scuti, são estrelas pulsantes, sendo que algumas delas mostram assinaturas atribuídas para um segundo tipo de pulsação. A descoberta mostra que isso é na verdade a assinatura de um campo magnético. Essa descoberta tem importantes implicações para o entendimento do interior das estrelas.
Dois tipos de estrelas pulsantes existem entre as estrelas com massa entre 1.5 e 2.5 vezes a massa do Sol: as estrelas do tipo delta Scuti e as estrelas do tipo gamma Dor. A teoria nos diz que as estrelas com temperatura entre 6900 e 7400 graus Kelvin podem ter ambos os tipos de pulsação. Essas são então chamadas de estrelas híbridas. Contudo, o satélite Kepler da NASA tem detectado um grande número de estrelas híbridas com temperaturas maiores ou menores do que esse limite pensado anteriormente. A existência dessas estrelas híbridas com temperaturas maiores é algo muito controverso, já que desafia o nosso entendimento sobre as estrelas pulsantes do tipo delta Scuti e gamma Dor.
3d modeling of_gj1214b_atmosphere_formation_of_inhomogeneous_high_cloouds_and...Sérgio Sacani
Uma equipe de cientistas da Universidade de Washington e da Universidade de Toronto foram os primeiros a simular nuvens exóticas em 3D na atmosfera de um exoplaneta.
O objeto em questão, é o GJ 1214b, um exoplaneta chamado de mini-Netuno que foi descoberto, seis anos atrás pelos astrônomos no Harvard-Smithsonian Center for Astrophysics.
Também conhecido como Gliese 1214b, esse mundo tem cerca de 2.7 vezes o diâmetro da Terra e uma massa quase 7 vezes maior que a massa do nosso planeta. Ele está localizado a cerca de 52 anos-luz de distância na constelação de Ophiuchus.
O planeta orbita a estrela anã vermelha, GJ 1214, a cada 38 horas, a uma distância de 1.3 milhões de milhas.
De acordo com estudos prévios, o planeta tem uma atmosfera rica em água ou hidrogênio com extensas nuvens.
“Deve existir altas nuvens ou uma névoa orgânica na atmosfera – como nós observamos em Titã. Sua temperatura atmosférica excede o ponto de fusão da água”, disse o Dr. Benjamin Charnay, um dos membros da equipe da Universidade de Washington.
Extended x ray emission in the h i cavity of ngc 4151- galaxy-scale active ga...Sérgio Sacani
The document summarizes the discovery of diffuse soft X-ray emission extending about 2 kpc from the active nucleus of NGC 4151, filling the cavity of H i material. The X-ray emission has a luminosity of about 1039 erg s-1 and can be fit with either a thermal plasma model with a temperature of around 0.25 keV, or a photoionized model. This interaction between the AGN and interstellar medium implies the last episode of high nuclear activity occurred relatively recently, around 104 years ago.
This document summarizes a study of lithium and sodium abundances in stars in the globular cluster M4. The authors obtained spectra for 91 main sequence and subgiant branch stars using the FLAMES spectrograph on the VLT. They detected a weak anti-correlation between lithium and sodium abundances among unevolved main sequence stars. Notably, one star, #37934, showed an unusually high lithium abundance, comparable to estimates of the primordial lithium abundance. This high lithium abundance, coupled with the star's sodium-rich nature, suggests the lithium may have come from pollution by a previous generation of stars, though preservation of the primordial abundance cannot be ruled out. The detection provides new evidence that globular clusters
This document describes the discovery and characterization of CFBDSIR2149, a late T dwarf found to have an unusually red J-K color and enhanced K-band flux. Spectroscopy with X-Shooter revealed it has a T7 spectral type with low surface gravity features, indicating it is a young substellar object. Comparison to atmospheric models suggests it has a temperature of 650-750K, surface gravity of logg=3.75-4.0, and a mass in the planetary regime of 4-7 Jupiter masses. An analysis of its proper motion finds an 87% probability it is a member of the young AB Doradus moving group, which would make it a free-floating planet with an
The BEER algorithm identified Kepler-76b, a hot Jupiter orbiting an F star, from its Kepler light curve. The light curve showed evidence of the beaming, ellipsoidal, and reflection effects consistent with a planetary companion. Follow-up spectroscopy confirmed Kepler-76b with a mass of 2.0 ± 0.26 MJup and orbital period of 1.5449 days. Analysis of the light curve effects provided evidence that Kepler-76b exhibits atmospheric superrotation, or an eastward jet stream that shifts the hottest atmospheric region.
The exceptional soft_x_ray_halo_of_the_galaxy_merger_ngc6240Sérgio Sacani
The document summarizes a recent 150-ks Chandra observation of the galaxy merger NGC 6240. Extended soft X-ray emission is detected over a 110x80 kpc region around NGC 6240. Spectral analysis finds the emission comes from hot gas with a temperature of around 7.5 million K and a total mass of about 10^10 solar masses. The gas properties suggest widespread star formation over the past 200 Myr rather than a recent nuclear starburst. The fate of the diffuse hot gas after the galaxy merger is uncertain but it may be retained and evolve into the halo of an elliptical galaxy.
Alma observations of_feeding_and_feedback_in_nearby_seyfert_galaxies_outflow_...Sérgio Sacani
ALMA observations of the Seyfert 2 galaxy NGC 1433 reveal a nuclear gaseous spiral structure within a nuclear ring encircling a nuclear stellar bar. Near the nucleus, there is intense high-velocity CO emission interpreted as an AGN-driven molecular outflow. The outflow involves a molecular mass of 3.6 million solar masses and a flow rate of about 7 solar masses per year. Continuum emission at the center is likely thermal dust emission from a molecular torus expected in this Seyfert 2 galaxy. The observations probe gas dynamics within 24 parsecs of the active galactic nucleus.
The Large APEX Bolometer Camera (LABOCA) is a new 295-bolometer submillimeter camera operating at 870 μm that has been commissioned for use on the 12 m Atacama Pathfinder Experiment (APEX) telescope. LABOCA offers unprecedented mapping capabilities for submillimeter continuum emission due to APEX's efficiency and the excellent atmospheric transmission at the site. LABOCA is designed to map large areas of the sky rapidly without the need for a chopping secondary mirror by using fast scanning techniques and correlating signals across the array to remove atmospheric contributions.
1. This document describes a multiwavelength campaign on the Seyfert 1 galaxy Mrk 509 using five satellites and two ground-based facilities.
2. The campaign aims to study several open questions about active galactic nuclei (AGN), including the location and physics of outflows from AGN, the nature of continuum emission, the geometry and physical state of the X-ray broad emission line region, and the Fe-K line complex.
3. The observations cover more than five decades in frequency, from 2 μm to 200 keV, and include a simultaneous set of deep XMM-Newton and INTEGRAL observations over seven weeks. This allows the authors to disentangle different components and study time variability
This document summarizes the discovery and analysis of a Type Ia supernova (SN Ia) at a redshift of 1.71, the most distant spectroscopically confirmed SN Ia at the time. The Hubble Space Telescope was used to obtain spectroscopy and photometry of the supernova. Analysis of the spectroscopy confirms it as a SN Ia with 92% confidence. The photometry is used to determine the supernova's distance, which agrees with the predictions of the ΛCDM cosmological model. This distant supernova helps improve constraints on the nature and behavior of dark energy in the early universe.
Modeling extrasolar planetary atmospheres discusses techniques for modeling exoplanet atmospheres including:
1) 1D radiative models that reconstruct atmospheric temperature structures and simulate thermal emission and reflected light.
2) 2D and 3D global circulation models that simulate atmospheric winds and temperature distributions driven by stellar irradiation and planetary rotation.
3) Advanced 3D models that combine radiative transfer with hydrodynamics to model atmospheric chemistry, clouds, and winds. These simulations produce synthetic spectra and light curves for comparison to observations.
Alma observations of_feed_and_feedback_in_nearby_seyfert_galaxiesSérgio Sacani
The ALMA observations of NGC 1433 reveal a nuclear gaseous spiral structure within the central kpc. This spiral winds up into a pseudo-ring at ~200 pc from the center. Near the nucleus, there is intense high-velocity CO emission up to 200 km/s that is interpreted as an outflow, involving 3.6 million solar masses of molecular gas and a flow rate of ~7 solar masses per year. The outflow could be driven by both the central star formation and AGN through its radio jets. Continuum emission at 0.87 mm is detected only at the very center and likely comes from thermal dust emission from the molecular torus expected in this Seyfert 2 galaxy.
This document summarizes star forming regions in the constellation of Cepheus. It describes several giant molecular cloud complexes located at various distances from the Sun, ranging from clouds within 500 pc to regions associated with the Perseus spiral arm at 2-3 kpc. Key regions discussed include the Cepheus Flare clouds below 500 pc, three OB associations (Cep OB2, Cep OB3, Cep OB4) located 600-900 pc away, and the well-known high mass star forming region S 140 located at 900 pc. Tables list molecular clouds and young stars identified in the Cepheus region. Maps show the distribution of clouds, extinction, and pre-main sequence stars across the constellation.
Uma equipe de astrofísicos usando o Observatório W. M. Keck no Havaí mediu com sucesso a galáxia mais distante já registrada e o mais interessante, capturou sua emissão de hidrogênio vista quando o universo tinha menos de 600 milhões de anos de vida. Adicionalmente, o método pelo qual a galáxia EGSY8p7 foi detectada dá uma ideia importante sobre como as primeiras estrelas no universo se acenderam depois do Big Bang.
Usando o poderoso espectrógrafo infravermelho do Observatório Keck, chamado MOSFIRE, a equipe datou a galáxia detectando sua linha de emissão Lyman-alpha – uma assinatura do gás hidrogênio quente, aquecido pela forte emissão ultravioleta de estrelas recém-nascidas. Embora, frequentemente seja possível detectar essa assinatura em galáxias próximas da Terra, a detecção da emissão Lyman-alpha nessas grandes distâncias é inesperada, já que ela é facilmente absorvida pelos numerosos átomos de hidrogênio que acredita-se existam no espaço entre as galáxias no nascer do universo. O resultado dá uma nova ideia sobre a reionização cósmica, o processo pelo qual nuvens escuras de hidrogênio foram partidas em seus prótons constituintes e elétrons pelas primeiras gerações de galáxias.
“Nós frequentemente observamos a linha de emissão Lyman-alpha do hidrogênio em objetos próximos já que eles são um dos traçadores mais confiáveis da formação de estrelas”, disse o astrônomo Adi Zitrin, do Instituto de Tecnologia da Califórnia, o Caltech, principal autor do estudo. “Contudo, à medida que penetramos mais fundo no universo, e então voltamos a tempos remotos, o espaço entre as galáxias continha um grande número de nuvens escuras de hidrogênio que absorviam esse sinal”.
An almost dark galaxy with the mass of the Small Magellanic CloudSérgio Sacani
This document describes the discovery and characterization of an almost dark galaxy named Nube. Deep imaging with GTC revealed Nube has an extremely low surface brightness of 26.7 mag/arcsec^2 and a stellar mass of 4x10^8 solar masses. Follow-up observations with GBT detected HI emission from Nube, suggesting it is located 107 Mpc away. At this distance, Nube has a large half-mass radius of 6.9 kpc and low effective stellar density, making it the most extended low-surface brightness galaxy found. Its properties are difficult to reproduce in CDM simulations but are consistent with an ultra-light dark matter particle model.
Similar to The high albedo of the hot jupiter kepler 7 b (20)
Compositions of iron-meteorite parent bodies constrainthe structure of the pr...Sérgio Sacani
Magmatic iron-meteorite parent bodies are the earliest planetesimals in the Solar System,and they preserve information about conditions and planet-forming processes in thesolar nebula. In this study, we include comprehensive elemental compositions andfractional-crystallization modeling for iron meteorites from the cores of five differenti-ated asteroids from the inner Solar System. Together with previous results of metalliccores from the outer Solar System, we conclude that asteroidal cores from the outerSolar System have smaller sizes, elevated siderophile-element abundances, and simplercrystallization processes than those from the inner Solar System. These differences arerelated to the formation locations of the parent asteroids because the solar protoplane-tary disk varied in redox conditions, elemental distributions, and dynamics at differentheliocentric distances. Using highly siderophile-element data from iron meteorites, wereconstruct the distribution of calcium-aluminum-rich inclusions (CAIs) across theprotoplanetary disk within the first million years of Solar-System history. CAIs, the firstsolids to condense in the Solar System, formed close to the Sun. They were, however,concentrated within the outer disk and depleted within the inner disk. Future modelsof the structure and evolution of the protoplanetary disk should account for this dis-tribution pattern of CAIs.
Signatures of wave erosion in Titan’s coastsSérgio Sacani
The shorelines of Titan’s hydrocarbon seas trace flooded erosional landforms such as river valleys; however, it isunclear whether coastal erosion has subsequently altered these shorelines. Spacecraft observations and theo-retical models suggest that wind may cause waves to form on Titan’s seas, potentially driving coastal erosion,but the observational evidence of waves is indirect, and the processes affecting shoreline evolution on Titanremain unknown. No widely accepted framework exists for using shoreline morphology to quantitatively dis-cern coastal erosion mechanisms, even on Earth, where the dominant mechanisms are known. We combinelandscape evolution models with measurements of shoreline shape on Earth to characterize how differentcoastal erosion mechanisms affect shoreline morphology. Applying this framework to Titan, we find that theshorelines of Titan’s seas are most consistent with flooded landscapes that subsequently have been eroded bywaves, rather than a uniform erosional process or no coastal erosion, particularly if wave growth saturates atfetch lengths of tens of kilometers.
SDSS1335+0728: The awakening of a ∼ 106M⊙ black hole⋆Sérgio Sacani
Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a ∼ 106M⊙ black hole (BH) that is currently in the process of ‘turning on’. Aims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728. Methods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra. Results. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1−W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux ∼ 3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region. Conclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a ∼ 106M⊙ AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGNobserved in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour. Key words. galaxies: active– accretion, accretion discs– galaxies: individual: SDSS J133519.91+072807.4
Discovery of An Apparent Red, High-Velocity Type Ia Supernova at 𝐳 = 2.9 wi...Sérgio Sacani
We present the JWST discovery of SN 2023adsy, a transient object located in a host galaxy JADES-GS
+
53.13485
−
27.82088
with a host spectroscopic redshift of
2.903
±
0.007
. The transient was identified in deep James Webb Space Telescope (JWST)/NIRCam imaging from the JWST Advanced Deep Extragalactic Survey (JADES) program. Photometric and spectroscopic followup with NIRCam and NIRSpec, respectively, confirm the redshift and yield UV-NIR light-curve, NIR color, and spectroscopic information all consistent with a Type Ia classification. Despite its classification as a likely SN Ia, SN 2023adsy is both fairly red (
�
(
�
−
�
)
∼
0.9
) despite a host galaxy with low-extinction and has a high Ca II velocity (
19
,
000
±
2
,
000
km/s) compared to the general population of SNe Ia. While these characteristics are consistent with some Ca-rich SNe Ia, particularly SN 2016hnk, SN 2023adsy is intrinsically brighter than the low-
�
Ca-rich population. Although such an object is too red for any low-
�
cosmological sample, we apply a fiducial standardization approach to SN 2023adsy and find that the SN 2023adsy luminosity distance measurement is in excellent agreement (
≲
1
�
) with
Λ
CDM. Therefore unlike low-
�
Ca-rich SNe Ia, SN 2023adsy is standardizable and gives no indication that SN Ia standardized luminosities change significantly with redshift. A larger sample of distant SNe Ia is required to determine if SN Ia population characteristics at high-
�
truly diverge from their low-
�
counterparts, and to confirm that standardized luminosities nevertheless remain constant with redshift.
Evidence of Jet Activity from the Secondary Black Hole in the OJ 287 Binary S...Sérgio Sacani
Wereport the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in the blazar OJ287. In the binary black hole model, it is associated with an impact of the secondary black hole on the accretion disk of the primary. Our multifrequency observing campaign was set up to search for such a signature of the impact based on a prediction made 8 yr earlier. The first I-band results of the flare have already been reported by Kishore et al. (2024). Here we combine these data with our monitoring in the R-band. There is a big change in the R–I spectral index by 1.0 ±0.1 between the normal background and the flare, suggesting a new component of radiation. The polarization variation during the rise of the flare suggests the same. The limits on the source size place it most reasonably in the jet of the secondary BH. We then ask why we have not seen this phenomenon before. We show that OJ287 was never before observed with sufficient sensitivity on the night when the flare should have happened according to the binary model. We also study the probability that this flare is just an oversized example of intraday variability using the Krakow data set of intense monitoring between 2015 and 2023. We find that the occurrence of a flare of this size and rapidity is unlikely. In machine-readable Tables 1 and 2, we give the full orbit-linked historical light curve of OJ287 as well as the dense monitoring sample of Krakow.
Candidate young stellar objects in the S-cluster: Kinematic analysis of a sub...Sérgio Sacani
Context. The observation of several L-band emission sources in the S cluster has led to a rich discussion of their nature. However, a definitive answer to the classification of the dusty objects requires an explanation for the detection of compact Doppler-shifted Brγ emission. The ionized hydrogen in combination with the observation of mid-infrared L-band continuum emission suggests that most of these sources are embedded in a dusty envelope. These embedded sources are part of the S-cluster, and their relationship to the S-stars is still under debate. To date, the question of the origin of these two populations has been vague, although all explanations favor migration processes for the individual cluster members. Aims. This work revisits the S-cluster and its dusty members orbiting the supermassive black hole SgrA* on bound Keplerian orbits from a kinematic perspective. The aim is to explore the Keplerian parameters for patterns that might imply a nonrandom distribution of the sample. Additionally, various analytical aspects are considered to address the nature of the dusty sources. Methods. Based on the photometric analysis, we estimated the individual H−K and K−L colors for the source sample and compared the results to known cluster members. The classification revealed a noticeable contrast between the S-stars and the dusty sources. To fit the flux-density distribution, we utilized the radiative transfer code HYPERION and implemented a young stellar object Class I model. We obtained the position angle from the Keplerian fit results; additionally, we analyzed the distribution of the inclinations and the longitudes of the ascending node. Results. The colors of the dusty sources suggest a stellar nature consistent with the spectral energy distribution in the near and midinfrared domains. Furthermore, the evaporation timescales of dusty and gaseous clumps in the vicinity of SgrA* are much shorter ( 2yr) than the epochs covered by the observations (≈15yr). In addition to the strong evidence for the stellar classification of the D-sources, we also find a clear disk-like pattern following the arrangements of S-stars proposed in the literature. Furthermore, we find a global intrinsic inclination for all dusty sources of 60 ± 20◦, implying a common formation process. Conclusions. The pattern of the dusty sources manifested in the distribution of the position angles, inclinations, and longitudes of the ascending node strongly suggests two different scenarios: the main-sequence stars and the dusty stellar S-cluster sources share a common formation history or migrated with a similar formation channel in the vicinity of SgrA*. Alternatively, the gravitational influence of SgrA* in combination with a massive perturber, such as a putative intermediate mass black hole in the IRS 13 cluster, forces the dusty objects and S-stars to follow a particular orbital arrangement. Key words. stars: black holes– stars: formation– Galaxy: center– galaxies: star formation
JAMES WEBB STUDY THE MASSIVE BLACK HOLE SEEDSSérgio Sacani
The pathway(s) to seeding the massive black holes (MBHs) that exist at the heart of galaxies in the present and distant Universe remains an unsolved problem. Here we categorise, describe and quantitatively discuss the formation pathways of both light and heavy seeds. We emphasise that the most recent computational models suggest that rather than a bimodal-like mass spectrum between light and heavy seeds with light at one end and heavy at the other that instead a continuum exists. Light seeds being more ubiquitous and the heavier seeds becoming less and less abundant due the rarer environmental conditions required for their formation. We therefore examine the different mechanisms that give rise to different seed mass spectrums. We show how and why the mechanisms that produce the heaviest seeds are also among the rarest events in the Universe and are hence extremely unlikely to be the seeds for the vast majority of the MBH population. We quantify, within the limits of the current large uncertainties in the seeding processes, the expected number densities of the seed mass spectrum. We argue that light seeds must be at least 103 to 105 times more numerous than heavy seeds to explain the MBH population as a whole. Based on our current understanding of the seed population this makes heavy seeds (Mseed > 103 M⊙) a significantly more likely pathway given that heavy seeds have an abundance pattern than is close to and likely in excess of 10−4 compared to light seeds. Finally, we examine the current state-of-the-art in numerical calculations and recent observations and plot a path forward for near-future advances in both domains.
Anti-Universe And Emergent Gravity and the Dark UniverseSérgio Sacani
Recent theoretical progress indicates that spacetime and gravity emerge together from the entanglement structure of an underlying microscopic theory. These ideas are best understood in Anti-de Sitter space, where they rely on the area law for entanglement entropy. The extension to de Sitter space requires taking into account the entropy and temperature associated with the cosmological horizon. Using insights from string theory, black hole physics and quantum information theory we argue that the positive dark energy leads to a thermal volume law contribution to the entropy that overtakes the area law precisely at the cosmological horizon. Due to the competition between area and volume law entanglement the microscopic de Sitter states do not thermalise at sub-Hubble scales: they exhibit memory effects in the form of an entropy displacement caused by matter. The emergent laws of gravity contain an additional ‘dark’ gravitational force describing the ‘elastic’ response due to the entropy displacement. We derive an estimate of the strength of this extra force in terms of the baryonic mass, Newton’s constant and the Hubble acceleration scale a0 = cH0, and provide evidence for the fact that this additional ‘dark gravity force’ explains the observed phenomena in galaxies and clusters currently attributed to dark matter.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Climate extremes likely to drive land mammal extinction during next supercont...
The high albedo of the hot jupiter kepler 7 b
1. Accepted for publication in ApJL
Preprint typeset using L TEX style emulateapj v. 8/13/10
A
THE HIGH ALBEDO OF THE HOT JUPITER KEPLER-7 B
Brice-Olivier Demory , Sara Seager1 , Nikku Madhusudhan2 , Hans Kjeldsen3 , Jørgen Christensen-Dalsgaard3 ,
1
Micha¨l Gillon4 , Jason F. Rowe5 , William F. Welsh6 , Elisabeth R. Adams7 , Andrea Dupree7 , Don McCarthy8 ,
e
Craig Kulesa8 , William J. Borucki5 , David G. Koch5 and the Kepler Science Team
Accepted for publication in ApJL
ABSTRACT
arXiv:1105.5143v1 [astro-ph.EP] 25 May 2011
Hot Jupiters are expected to be dark from both observations (albedo upper limits) and theory (alkali
metals and/or TiO and VO absorption). However, only a handful of hot Jupiters have been observed
with high enough photometric precision at visible wavelengths to investigate these expectations. The
NASA Kepler mission provides a means to widen the sample and to assess the extent to which hot
Jupiter albedos are low. We present a global analysis of Kepler-7 b based on Q0-Q4 data, published
radial velocities, and asteroseismology constraints. We measure an occultation depth in the Kepler
bandpass of 44±5 ppm. If directly related to the albedo, this translates to a Kepler geometric albedo
of 0.32±0.03, the most precise value measured so far for an exoplanet. We also characterize the
planetary orbital phase lightcurve with an amplitude of 42±4 ppm. Using atmospheric models, we
find it unlikely that the high albedo is due to a dominant thermal component and propose two solutions
to explain the observed planetary flux. Firstly, we interpret the Kepler-7 b albedo as resulting from
an excess reflection over what can be explained solely by Rayleigh scattering, along with a nominal
thermal component. This excess reflection might indicate the presence of a cloud or haze layer in
the atmosphere, motivating new modeling and observational efforts. Alternatively, the albedo can be
explained by Rayleigh scattering alone if Na and K are depleted in the atmosphere by a factor of
10-100 below solar abundances.
Subject headings: planetary systems - stars: individual (Kepler-7, KIC 5780885, 2MASS
19141956+4105233) - techniques: photometric
1. INTRODUCTION visible, two orders of magnitude less than mid-infrared
More than 30 hot Jupiters benefit from observations signatures.
of their emitted radiation from near to mid-infrared, To date, eleven planets have an upper limit constraint
where the measurement of their thermal emission is on their geometric albedo : τ Boo b (Charbonneau et al.
the most favorable. Spitzer made a significant con- 1999; Leigh et al. 2003a; Rodler et al. 2010), υAnd b
tribution by producing a flurry of results allowing us (Collier Cameron et al. 2002), HD75289A b (Leigh et al.
to derive general properties of hot-Jupiter atmospheres 2003b; Rodler et al. 2008), HD209458b (Rowe et al.
(Deming & Seager 2009). Those planets are strongly 2008), CoRoT-1b (Alonso et al. 2009; Snellen et al.
irradiated by their host stars and their equilibrium 2009), CoRoT-2b (Alonso et al. 2010; Snellen et al.
temperatures were early estimated to be above 1000K 2010), HAT-P-7b (Christiansen et al. 2010; Welsh et al.
(Seager & Sasselov 2000). Those observations confirm 2010), Kepler-5b (Kipping & Bakos 2011; Desert et al.
that hot Jupiters efficiently reprocess the incident stellar 2011), Kepler-6b (Kipping & Bakos 2011; Desert et al.
flux into thermal reemission, exhibiting low flux at vis- 2011), Kepler-7b (Kipping & Bakos 2011) and
ible wavelengths (Marley et al. 1999; Seager et al. 2000; HD189733b (Berdyugina et al. 2011).
Sudarsky et al. 2003). Eight of them corroborate early theoretical predic-
Characterization of transiting hot-Jupiter reflected tions: with Ag < 0.3 (3σ upper limit) hot Jupiters
light suffers from the scarcity of observations. The plan- are dark in the visible. However Collier Cameron et al.
etary to stellar flux ratio is of the order of 10−5 in the (2002) determined Ag < 0.42 (3σ) from spectroscopy
in the 380-650nm range for υAnd b, Kipping & Bakos
1 Department of Earth, Atmospheric and Planetary Sciences, (2011) reported Ag = 0.38 ± 0.129 for Kepler-7 b and
Massachusetts Institute of Technology, 77 Massachusetts Ave., Berdyugina et al. (2011) determined a V -band albedo of
Cambridge, MA 02139, USA. demory@mit.edu
2 Department of Astrophysical Sciences, Princeton University,
Ag = 0.28 ± 0.16 for HD189733b from polarimetry, sug-
gesting dominance of reflected light over thermal emis-
Princeton, New Jersey 08544, USA.
3 Department of Physics and Astronomy, Aarhus University, sion.
DK-8000 Aarhus C, Denmark. Solar system giant planets have geometric albedos of
4 Institut d’Astrophysique et de G´ophysique, Universit´ de
e e 0.32 (Uranus) to 0.50 (Jupiter) in a bandpass similar to
Li`ge, All´e du 6 Aoˆt, 17, Bat. B5C, Li`ge 1, Belgium.
e e u e Kepler ’s (Karkoschka 1994). Those objects harbor bright
5 NASA Ames Research Center, Moffett Field, CA 94035,
USA. cloud decks made of ammonia and water ice that are
6 Astronomy Department, San Diego State University, San highly reflective at visible wavelengths. In contrast to the
Diego, CA 92182, USA. solar system giant planets, atmosphere models show that
7 Smithsonian Astrophysical Observatory, 60 Garden St.,
Cambridge, MA 02138, USA
8 Steward Observatory, University of Arizona, 933 N. Cherry 9 Determined in the Kepler bandpass, which has a >5% response
Ave, Tucson, AZ 85721, USA between 423 and 897 nm (Koch et al. 2010)
2. 2
the presence of alkali metals in hot-Jupiter atmospheres Spectrograph) observations and applied to both transit
(Na and K) as well as TiO and VO (at the hotter range) and occultation photometry.
causes significant absorption at visible wavelengths. The excellent sampling of the transit lightcurve moti-
We report in this letter the characterization of the hot vated us to fit for the limb-darkening (LD) coefficients.
Jupiter Kepler-7 b (Latham et al. 2010), based on Kepler For this purpose, we assumed a quadratic law and used
Q0-Q4 data. We present the photometry and data anal- c1 = 2u1 + u2 and c2 = u1 − 2u2 as jump parameters,
ysis in Sect. 2, while corresponding results are shown in where u1 and u2 are the quadratic coefficients.
Sect. 3. Discussion and atmospheric analysis are finally The MCMC has the following set of jump parameters:
presented in Sect. 4. the planet/star flux ratio, the impact parameter b, the
2. OBSERVATIONS AND DATA ANALYSIS
transit duration from first to fourth contact, the time of
√
minimum light, the orbital period, K = K 1 − e2 P 1/3 ,
2.1. Kepler photometry where K is the radial-velocity semi-amplitude, the occul-
Kepler-7 b belongs to the first set of new planets pub- tation depth, the√ LD combinations c1 and c2 and the
two √
lished by the Kepler science team in early 2010. Kepler- two parameters e cos ω and e sin ω. A uniform prior
7 b is a 4.8-day period hot Jupiter orbiting a V =13.04 distribution is assumed for all jump parameters.
sub-giant G star with M = 1.347 ± 0.07M and R =
1.843 ± 0.07R (Latham et al. 2010). Like all objects lo- 2.2.1. Model and systematics
cated in the Kepler field, Kepler-7 benefits from nearly The transit and occultation photometry are modeled
continuous photometric monitoring since mid-2009. with the Mandel & Agol (2002) model, multiplied by a
We base our analysis on the Q0-Q4 quarters, which second order polynomial accounting for stellar and in-
represent nearly one year of observations. Data recorded strumental variability. Baseline model coefficients are
during each quarter are differentiated in short- and long- determined for each lightcurve with the SVD method
cadence timeseries, that are binnings per 58.84876s and (Press et al. 1992) at each step of the MCMC. Correlated
29.4244min respectively of the same CCD readouts. Five noise was accounted for following Winn et al. (2008);
long-cadence (Jenkins et al. 2010) and six short cadence Gillon et al. (2010), to ensure reliable error bars on the
(Gilliland et al. 2010) datasets are used as part of this fitted parameters. For this purpose, we compute a scal-
study, representing 272,719 photometric datapoints and ing factor based on the standard deviation of the binned
311.68 effective days of observations, out of which 175.37 residuals for each lightcurve with different time bins. The
days have also been recorded in short cadence. We used error bars are then multiplied by this scaling factor. We
the raw photometry for our purpose. obtained a mean scaling factor of 1.04 for all photometry,
Kepler-7 is a photometrically quiet star: apart from the denoting a negligible contribution from correlated noise.
4.88-day period transit signals, no evidence of significant The mean global photometric RMS per 30-min bin is 96
stellar variability is apparent in the data. parts per million (ppm).
2.2. Data analysis
2.2.2. Asteroseismology
For the purpose of this global analysis, we used
the implementation of the Markov Chain Monte-Carlo The data series for Kepler-7 contains 9 months of
(MCMC) algorithm presented in Gillon et al. (2009, data at a cadence of 1 minute. The power spectrum
2010). MCMC is a Bayesian inference method based on shows a clear excess of power near 1.05mHz. The
stochastic simulations that samples the posterior prob- asteroseismic analysis of the data was performed us-
ability distributions of adjusted parameters for a given ing the pipeline developed at the Kepler Asteroseis-
model. Our MCMC implementation uses the Metropolis- mic Science Operations Center as described in detail by
Hastings algorithm to perform this sampling. Our nom- Christensen-Dalsgaard et al. (2008, 2010); Huber et al.
inal model is based on a star and a transiting planet on (2009); Gilliland et al. (2011). Using the matched fil-
a Keplerian orbit about their center of mass. ter approach we determine a value for the large separa-
Our global analysis was performed using 199 transit tion of 56µHz. Locating the asymptotic frequency struc-
and occultation lightcurves in total, out of which 70 ture in the folded power allows a robust identification of
were acquired in short cadence mode. We discarded 13 13 individual p-mode frequencies and an estimate of the
lightcurves because of discontinuities due to spacecraft scatter on those frequencies (0.9µHz). The frequencies
roll, change of focus, pointing offsets or safe mode events. resulting from this analysis were fitted to stellar models
Input data also include the 9 radial velocity points in the same manner as in Christensen-Dalsgaard et al.
obtained from NOT/FIES (FIber-fed Echelle Spectro- (2010), using also the effective temperature and metal-
graph) that were published in Latham et al. (2010). licity ([Fe/H]) determined by Latham et al. (2010). The
As the focus of this study is on using the transits models did not include diffusion and settling. Models
and occultations to refine the system parameters, for the were computed without overshoot from the convective
model fitting we use only the photometry near the eclipse core, as well as with overshoot of 0.1Hp and 0.2Hp , where
events. Windows of width 0.6 days (12.3% of the or- Hp is the pressure scale height at the edge of the convec-
bit) surrounding eclipses were used to measure the local tive core. The observed frequencies and effective temper-
out-of-transit baseline, while minimizing the computa- ature were fitted to the models in a least-squares sense,
tion time. A dilution of 2.7±0.5% was determined from resulting in a weighted average of the stellar properties.
MMT/ARIES10 (ARizona Infrared imager and Echelle Interestingly, only models with overshoot provided ac-
ceptable fits to the frequencies within the observed range
10 MMT is a joint facility of the Smithsonian Institution and
of the effective temperature.
University of Arizona. We used the resulting stellar density (see Table 1) as
3. 3
a Bayesian prior in the MCMC and the corresponding to 0.9 µm. Albedo values reported in this paper for
stellar mass to derive the system’s physical parameters. Kepler-7 b are averaged over this spectral domain. For
the highly irradiated exoplanets, a significant part of the
2.2.3. Phase curve
thermal emission leaks into the red end of this bandpass,
About 312 days of Kepler-7 observations are covered making the occultation depth larger. With a 4.9-d long
in Q0-Q4 data. This motivated us to search for the orbit, Kepler-7 b would not be expected to be one of the
planetary phase signature. We first removed the tran- hottest giant planets found to date. However, its host
sits and fitted the long and short cadence data to re- star with a Teff =5933K, 1.4 M and 2.0 R , is about
move temporal linear trends. Stellar and instrumental in- 4.5 times more luminous than the Sun. These compen-
duced modulation on the photometry was then removed sating factors make it necessary to estimate the relative
by pre-whitening the raw data using Period04 software contributions of thermal emission and reflected light to
(Lenz & Breger 2005). This step allowed us to filter out the occultation depth.
all frequencies below the orbital frequency and those that The possible relative contributions of thermal emis-
are not connected with the planetary orbit period. sion and reflected light to the observed flux in the Ke-
3. RESULTS pler bandpass are shown in Fig. 3. The thermal emis-
sion is represented by an effective brightness tempera-
We present Kepler-7 b’s system parameters in Table ture (TB ), and the reflected light by the geometric albedo
1. Each value is the median of the marginal posterior (Ag ). Also shown are the dayside equilibrium tempera-
distribution obtained for the relevant parameter. Error tures corresponding to atmosphere with efficient versus
bars are the corresponding 68.3% probability interval. inefficient energy redistribution (dotted lines). The de-
Figure 1 shows the phase-folded transit photometry of generacy between TB and Ag is evident. The observed
Kepler-7 b. occultation depth allows for geometric albedos as high
Our results confirm the very low density of Kepler- as 0.35 for TB = 1500K in the Kepler bandpass. On
7 b. The external constraint from asteroseismology mod- the other hand, allowing for a zero geometric albedo re-
eling causes the planet radius to significantly increase as quires an extremely high TB of 2500-2600K, which is ∼
compared to the discovery paper (Latham et al. 2010). 400K higher than the maximum equilibrium tempera-
Our MCMC analysis yields a planetary radius of RP = ture. Completely breaking the degeneracy between Ag
1.61 ± 0.02RJup and a mass of MP = 0.44 ± 0.04MJup , and TB requires additional observations in the visible
which gives a surprisingly low density of ρP = 0.14±0.01 and near-infrared. However, tentative constraints can be
g cm−3 . Interestingly, Kepler-7b’s properties are close placed on the various sources of opacity and scattering
to WASP-17b’s (Anderson et al. 2010), the least dense using a physical model atmosphere.
transiting planet discovered so far with ρP = 0.12±0.06 g The thermal and reflection spectra of the planetary
cm−3 . Both planets are of similar mass and orbit evolved atmosphere depend on the various atomic and molec-
stars. ular opacities, sources of scattering, and the temper-
We find a marginal orbital eccentricity of e = 0.001 ± ature structure, all of which constitute a large num-
0.001. ber of free parameters under-constrained by the single
We determine an occultation depth of 44±5 ppm. The data point available. Nevertheless, the precise mea-
corresponding phase-folded lightcurve is shown on bot- surement allows us to constrain regions of the param-
tom panel of Fig. 2. eter space, given plausible assumptions about energy
Finally we find an orbital phase curve of 42±4 ppm am- balance and atmospheric chemistry. We use the exo-
plitude that is consistent with the occultation depth and planet atmospheric modeling and retrieval technique of
phased with Kepler-7 b’s transits and occultations. We Madhusudhan & Seager (2009). The model computes
model the phase curve assuming a Lambert law phase- line-by-line radiative transfer in a plane-parallel atmo-
dependent flux-ratio (Sobolev 1975) : sphere, with the assumption of hydrostatic equilibrium
Rp
2
sin(α) + (π − α) cos(α) and global energy balance, and parametrized chemical
φ(α) = Ag composition and temperature structure. A key aspect
a π of the model is the flexibility to explore a wide range of
where α is the orbital phase, Ag is the geometric albedo, molecular abundances and pressure-temperature (P -T )
Rp is the planetary radius and a is the orbital semi- profiles, without any assumptions of chemical or radia-
major axis. A value of Ag = 0.31 ± 0.03 is deduced tive equilibrium. We consider all the major sources of
from the phase curve using Rp and a values from Ta- opacity in the visible and near-infrared: H2 -H2 collision-
ble 1. Although a perfectly reflecting Lambertian sphere induced absorption, Na, K, Rayleigh scattering, TiO and
has Ag = 2 , the Lambert law can represent a scatterer VO (with a condensation curve), H2 O, CO, CH4 and
3
which takes on a lower Ag value for an atmosphere with CO2 (Christiansen et al. 2010; Madhusudhan & Seager
some absorption (Seager 2010). The resulting lightcurve 2010, 2011). However, given the availability of the Ke-
is shown on top panel of Fig. 2, with the best-fit model pler observation alone in the present work, the number
superimposed. No ellipsoidal variations are detected of free parameters far exceed the single data point. Con-
(−1 ± 3ppm). sequently, we explore a range of 1-D P -T profiles and
chemical composition to explore possible explanations of
4. THE HIGH ALBEDO OF KEPLER-7 B the observed flux in the Kepler bandpass.
If directly related to the albedo, the measured occul- Our results indicate that a high geometric albedo is
tation depth of 44±5 ppm translates to a 0.32±0.03 geo- the most plausible explanation of the observed eclipse
metric albedo as measured by Kepler. The Kepler band- depth. The major sources of opacity in the Kepler band-
pass encompasses a large range of wavelengths, from 0.4 pass are atomic Na and K, molecular TiO and VO where
4. 4
Fig. 1.— Top : Kepler-7 b phase-folded transit lightcurve with best-fit model superimposed. Binned per 15min. Error bars are smaller
than the plotted datapoints. Bottom : residuals.
Fig. 2.— Top : Kepler-7 b orbital phase curve with best-fit model (see text) superimposed. Transits are omitted. Bottom : Kepler-7 b
phase-folded occultation lightcurve with best-fit model. Binned per 15min.
5. 5
TABLE 1
Kepler-7 system parameters
Parameters Value
Jump parameters
Planet/star area ratio (Rp /Rs )2 0.006772+0.000018
−0.000021
b = a cos i/R [R ] 0.5565+0.0060
−0.0063
Transit width [d] 0.21777+0.00023
−0.00021
T0 - 2450000 [HJD] 4967.27599+0.00019
−0.00020
Orbital period P [d] 4.8854830+0.0000042
−0.0000041
RV K [m s−1 d1/3 ] 73.1+6.7
−6.8
√
e cos ω 0.0376+0.0143
−0.0153
√
e sin ω −0.0016+0.0026
−0.0022
c1 = 2u1 + u2 0.922+0.011
−0.011
c2 = u1 − 2u2 −0.143+0.022
−0.022
Occultation depth 0.000044+0.000005
−0.000006
Deduced stellar parameters
u1 0.344+0.007
−0.007
u2 0.232+0.009
−0.009
Density ρstar [g cm−3 ] 0.231+0.004
−0.004
Surface gravity log g∗ [cgs] 3.960+0.005
−0.005
Mass M [M ] 1.36+0.03
−0.03
Radius R [R ] 2.02+0.02
−0.02
Asteroseismic parameters
Density ρstar [g cm−3 ] 0.252 ± 0.003
Mass Mstar [M ] 1.359 ± 0.031
Radius Rstar [R ] 1.966 ± 0.013
Stellar age [Gyr] 3.3 ± 0.4
Surface gravity log g∗ [cgs] 3.984 ± 0.006
Deduced planet parameters
RV K [m s−1 ] 43.1+3.9
−4.0
btransit [R ] 0.557+0.006
−0.006
boccultation [R ] 0.556+0.006
−0.006
Toccultation - 2450000 [HJD] 4974.6086+0.0040
−0.0028
Orbital semi-major axis a [AU] 0.06246+0.00046
−0.00046
Orbital inclination i [deg] 85.18+0.076
−0.074
Orbital eccentricity e 0.001+0.001
−0.001
Argument of periastron ω [deg] 357.1+4.4
−2.8
Density ρP [g cm−3 ] 0.14+0.01
−0.01
+0.04
Surface gravity log gP [cgs] 2.62−0.04
Mass MP [MJ up ] 0.443+0.041
−0.042
Radius RP [RJ up ] 1.614+0.015
−0.015
6. 6
contributions from thermal emission and Rayleigh scat-
tering (with a geometric albedo of 0.17). However, two
problems confront this scenario. Firstly, requiring such
a high thermal flux implies that all the stellar incident
flux on the dayside of the planet must be reradiated on
the same side, with almost no energy recirculation to the
night side. The Kepler phase curve of Kepler-7 b, shown
in Fig. 2, could support this scenario if all the flux were
purely due to thermal emission. However, because there
is still a 50% contribution due to Rayleigh scattering
required to explain the net flux at occultation, the Ke-
pler phase curve cannot be interpreted as solely due to
a large day-night temperature contrast. Furthermore,
at the high pressures (P ∼ 1 bar) probed by the Ke-
pler bandpass, the temperature should be homogenized
across day and night side, exhibiting small thermal or-
bital phase variation. Secondly, at the high tempera-
Fig. 3.— Model-independent domain of allowed geometric albedo ture of ∼2600K probed by Kepler, it seems unlikely that
Ag (reflected light) and brightness temperature TB (thermal emis- TiO/VO can be depleted by factors of 103 below chemical
sion) combinations, constrained by the observed Kepler occultation equilibrium at ∼ 1 bar pressure, although the difficulty
depth. The shaded area represents the 1σ confidence domain found
using a Kurucz spectrum for the star and blackbody emission for of sustaining TiO/VO at high altitudes (P 10−3 bar)
the planet. The dotted lines depict the equilibrium temperature has been reported in literature (Spiegel et al. 2009).
assuming full redistribution (left) and no redistribution (right). In our final scenario, we investigate if Rayleigh scat-
tering alone can contribute dominantly to the observed
flux. The strongest absorbers of Rayleigh scattered light,
temperatures are higher than the condensation tempera- as shown in the first two panels of Fig. 4, are atomic Na
ture, Rayleigh scattering, and any possible contribution and K. We find that if we allow depletion of Na and K
due to clouds and/or hazes. Consequently, we examine by a factor of 10-100 of the equilibrium composition, the
the constraints on each of these opacity sources due to observed flux in the Kepler bandpass can be fit extremely
the Kepler point. We assume all other molecules (H2 O, well with a geometric albedo of 0.32 from Rayleigh scat-
CO, CH4 and CO2 ) to be in chemical equilibrium, assum- tering alone along with a nominal contribution due to
ing solar abundances. We find that the observed Kepler thermal emission. The resultant model also yields effi-
flux can be explained under three scenarios, shown in the cient day-night energy circulation.
three panels of Fig. 4. We finally note that the large planetary radius and
In a first scenario, we consider a model where all the very low density would make appealing the hypothe-
major absorbers, i.e. Na, K, TiO, and VO, are in chem- sis of Kepler-7 b being a very young planet that would
ical equilibrium with solar abundances, and we nomi- still be in its cooling phase. However, the asteroseismol-
nally vary only the P -T profile to find a close match to ogy results presented in Sect. 2 produce a stellar age of
the data. In this scenario, we find that the observed 3.3±0.4Gyr, which argues for a planetary evolutionary
flux cannot be accounted for by thermal emission and state beyond the collapsing phase (Fortney et al. 2005),
Rayleigh scattering alone, both of which together provide and a negligible contribution from internal heat to the
a net flux contrast of ∼ 20 ppm, with Rayleigh scatter- occultation depth.
ing contributing a geometric albedo of 0.15. In principle,
one might expect that hotter temperature profiles might 5. CONCLUSIONS
lead to greater thermal emission which could contribute Given the three scenarios described in Sect. 4, we in-
to the observed flux. However, warmer P -T profiles in- terpret the Kepler observed planetary flux as due to a
tercept longer absorption columns of TiO/VO which fur- combination of Rayleigh scattering and the presence of
ther lower the emergent thermal flux. Therefore, under clouds or a haze layer (e.g., Lecavelier Des Etangs et al.
the assumption of solar abundances of all species, excess 2008; Sing et al. 2009) in the atmosphere of Kepler-7 b,
flux in the form of reflected light, potentially from clouds yielding an averaged geometric albedo of ∼ 0.3 in the
and/or hazes, is required to explain the observed Kepler Kepler bandpass. A detailed cloud or haze model is be-
flux, implying a net geometric albedo of ∼ 0.3. yond the scope of the present work. Our results motivate
In a second scenario, we investigate if thermal emission new modeling and observational efforts to investigate the
can be a predominant contributor to the observed Kepler nature of clouds and hazes that might be possible in a
flux. The strongest absorber in the redder regions of the low gravity atmosphere such as that of Kepler-7 b.
Kepler bandpass, where thermal emission dominates, is
TiO, followed by VO. As discussed in the equilibrium
scenario above, TiO absorption precludes high bright- Authors thank the Kepler Giant Planet Working
ness temperatures due to thermal emission in the Kepler Group, P.-O. Quirion, M. Holman, D. Ragozzine, J.
bandpass. Conversely, we find that thermal emission can Jenkins, J.-M. D´sert, B. Benneke and D. Latham for
e
contribute substantially to the observed flux, if TiO and useful discussions. We thank E. Dunham, W. Cochran
VO are assumed to be depleted by over 103 in the lower and the referee for helpful comments that improved the
atmosphere (P ∼ 0.1 − 1 bar). Such a scenario just man- manuscript. B.-O.D. acknowledges support from the
ages to fit the data at the lower error bar, with equal Swiss NSF and thanks kindly R. Stewart, P.L. Vidale
7. 7
Fig. 4.— Model spectra of Kepler-7 b in the Kepler bandpass. Each panel corresponds to each scenario (1 to 3, left to right) described in
Sect.4. The Kepler data point is shown in red. In each panel, the black solid curve shows the net emergent spectrum. The net emergent
flux integrated in the Kepler bandpass is shown in green. The cyan and purple curves show the contributions of thermal emission and
reflected light to the emergent spectrum. The black dashed line shows a black body spectrum of the planet at 2550K, divided by a Kurucz
model spectrum for the star. The relevant Pressure-Temperature profiles are shown for each atmospheric model in the insets, with the TiO
condensation curve in dotted line.
and A. Verhoef from the University of Reading (UK), support from NASA Kepler Participating Science Pro-
where part of this work has been carried out. M.G. gram NNX10AD67G. Funding for this Discovery Mission
is Belgian FNRS Research Associate. We acknowledge is provided by NASA’s Science Mission Directorate.
Facilities:Kepler,MMT
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