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
Environmental monitoring of soil radon in a very tectonic area in south west ...Anax Fotopoulos
Abstract
This paper focuses on the investigation of the usefulness of measuring soil radon as a trace gas in the search of earthquake precursors. A multilevel approach was followed: (a) Detailed preparatory experimentation. (b) Set-up of methods and devices. (c) Active and passive radon measurements during a very active tectonic period in Peloponnese (Greece) on 2008. This period was combined with the occurrence of two very destructive earthquakes. (d) Detailed discussion and analysis of significant collected radon signals that included two very strong radon anomalies prior to the 8/6/2008 M=6.5 earthquake which occurred 29 km from the measuring site. The two detected strong radon disturbances could be possibly related only to the 8/6/2008 earthquake. (e) Discussion on the interpretation of the detected radon anomalies. The recent (2008) asperity model is proposed as a possible explanation of these anomalies. The paper concluded that the strong radon disturbances may be linked to strong earthquakes.
Environmental monitoring of soil radon in a very tectonic area in south west ...Anax Fotopoulos
Abstract
This paper focuses on the investigation of the usefulness of measuring soil radon as a trace gas in the search of earthquake precursors. A multilevel approach was followed: (a) Detailed preparatory experimentation. (b) Set-up of methods and devices. (c) Active and passive radon measurements during a very active tectonic period in Peloponnese (Greece) on 2008. This period was combined with the occurrence of two very destructive earthquakes. (d) Detailed discussion and analysis of significant collected radon signals that included two very strong radon anomalies prior to the 8/6/2008 M=6.5 earthquake which occurred 29 km from the measuring site. The two detected strong radon disturbances could be possibly related only to the 8/6/2008 earthquake. (e) Discussion on the interpretation of the detected radon anomalies. The recent (2008) asperity model is proposed as a possible explanation of these anomalies. The paper concluded that the strong radon disturbances may be linked to strong earthquakes.
Science with small telescopes - exoplanetsguest8aa6ebb
The search for extrasolar planets has become one of the most attractive problems in modern astrophysics. The biggest observatories in the world are involved in this task as well as little amateur instruments. There is also a huge variety of astronomical methods used for their investigation. Here I present the projects for searching for exoplanets by transit method and our observations of the planet WASP-2b. We observed a transit on 3/4 August 2008 with a 354 mm Schmidt-Cassegrain Celestron telescope and CCD SBIG STL 11000M camera. By precise photometry made using MaximDL software we obtained the light curve of the star system. Decrease of brightness by 0.02m is detected. Analyzing our data we estimate the radius of the planet and inclination of its orbit. Our results are in good correlation with the published information in literature.
We present spectroscopic observations of the nearby dwarf galaxy AGC 198691. This object is part
of the Survey of H I in Extremely Low-Mass Dwarfs (SHIELD) project, which is a multi-wavelength
study of galaxies with H I masses in the range of 106-107:2 M discovered by the ALFALFA survey.
We have obtained spectra of the lone H II region in AGC 198691 with the new high-throughput
KPNO Ohio State Multi-Object Spectrograph (KOSMOS) on the Mayall 4-m as well as with the Blue
Channel spectrograph on the MMT 6.5-m telescope. These observations enable the measurement of the
temperature-sensitive [O III]4363 line and hence the determination of a \direct" oxygen abundance
for AGC 198691. We nd this system to be an extremely metal-decient (XMD) system with an
oxygen abundance of 12+log(O/H) = 7.02 0.03, making AGC 198691 the lowest-abundance starforming
galaxy known in the local universe. Two of the ve lowest-abundance galaxies known have
been discovered by the ALFALFA blind H I survey; this high yield of XMD galaxies represents a
paradigm shift in the search for extremely metal-poor galaxies.
TEMPORAL EVOLUTION OF THE HIGH-ENERGY IRRADIATION AND WATER CONTENT OF TRAPPI...Sérgio Sacani
The ultracool dwarf star TRAPPIST-1 hosts seven Earth-size transiting planets, some of which could
harbour liquid water on their surfaces. UV observations are essential to measure their high-energy
irradiation, and to search for photodissociated water escaping from their putative atmospheres. Our
new observations of TRAPPIST-1 Ly-α line during the transit of TRAPPIST-1c show an evolution of
the star emission over three months, preventing us from assessing the presence of an extended hydrogen
exosphere. Based on the current knowledge of the stellar irradiation, we investigated the likely history
of water loss in the system. Planets b to d might still be in a runaway phase, and planets within the
orbit of TRAPPIST-1g could have lost more than 20 Earth oceans after 8 Gyr of hydrodynamic escape.
However, TRAPPIST-1e to h might have lost less than 3 Earth oceans if hydrodynamic escape stopped
once they entered the habitable zone. We caution that these estimates remain limited by the large
uncertainty on the planet masses. They likely represent upper limits on the actual water loss because
our assumptions maximize the XUV-driven escape, while photodissociation in the upper atmospheres
should be the limiting process. Late-stage outgassing could also have contributed significant amounts
of water for the outer, more massive planets after they entered the habitable zone. While our results
suggest that the outer planets are the best candidates to search for water with the JWST, they also
highlight the need for theoretical studies and complementary observations in all wavelength domains
to determine the nature of the TRAPPIST-1 planets, and their potential habitability.
Keywords: planetary systems - Stars: individual: TRAPPIST-1
EXTINCTION AND THE DIMMING OF KIC 8462852Sérgio Sacani
To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star
over a wide wavelength range from the UV to the mid-infrared from October 2015 through December
2016, using Swift, Spitzer and at AstroLAB IRIS. The star faded in a manner similar to the longterm
fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period
reported is 22.1 ± 9.7 milli-mag yr−1
in the Swift wavebands, with amounts of 21.0 ± 4.5 mmag in
the groundbased B measurements, 14.0 ± 4.5 mmag in V , and 13.0 ± 4.5 in R, and a rate of 5.0 ± 1.2
mmag yr−1 averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at
& 3 σ by three different observatories operating from the UV to the IR. The presence of long-term
secular dimming means that previous SED models of the star based on photometric measurements
taken years apart may not be accurate. We find that stellar models with Tef f = 7000 - 7100 K and
AV ∼ 0.73 best fit the Swift data from UV to optical. These models also show no excess in the
near-simultaneous Spitzer photometry at 3.6 and 4.5 µm, although a longer wavelength excess from
a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of
the fading favors a relatively neutral color (i.e., RV & 5, but not flat across all the bands) compared
with the extinction law for the general ISM (RV = 3.1), suggesting that the dimming arises from
circumstellar material
WHERE IS THE FLUX GOING? THE LONG-TERM PHOTOMETRIC VARIABILITY OF BOYAJIAN’S ...Sérgio Sacani
We present ∼ 800 days of photometric monitoring of Boyajian’s Star (KIC 8462852) from the AllSky
Automated Survey for Supernovae (ASAS-SN) and ∼ 4000 days of monitoring from the All Sky
Automated Survey (ASAS). We show that from 2015 to the present the brightness of Boyajian’s Star
has steadily decreased at a rate of 6.3 ± 1.4 mmag yr−1
, such that the star is now 1.5% fainter than it
was in February 2015. Moreover, the longer time baseline afforded by ASAS suggests that Boyajian’s
Star has also undergone two brightening episodes in the past 11 years, rather than only exhibiting a
monotonic decline. We analyze a sample of ∼ 1000 comparison stars of similar brightness located in
the same ASAS-SN field and demonstrate that the recent fading is significant at & 99.4% confidence.
The 2015 − 2017 dimming rate is consistent with that measured with Kepler data for the time period
from 2009 to 2013. This long-term variability is difficult to explain with any of the physical models
for the star’s behavior proposed to date
Science with small telescopes - exoplanetsguest8aa6ebb
The search for extrasolar planets has become one of the most attractive problems in modern astrophysics. The biggest observatories in the world are involved in this task as well as little amateur instruments. There is also a huge variety of astronomical methods used for their investigation. Here I present the projects for searching for exoplanets by transit method and our observations of the planet WASP-2b. We observed a transit on 3/4 August 2008 with a 354 mm Schmidt-Cassegrain Celestron telescope and CCD SBIG STL 11000M camera. By precise photometry made using MaximDL software we obtained the light curve of the star system. Decrease of brightness by 0.02m is detected. Analyzing our data we estimate the radius of the planet and inclination of its orbit. Our results are in good correlation with the published information in literature.
We present spectroscopic observations of the nearby dwarf galaxy AGC 198691. This object is part
of the Survey of H I in Extremely Low-Mass Dwarfs (SHIELD) project, which is a multi-wavelength
study of galaxies with H I masses in the range of 106-107:2 M discovered by the ALFALFA survey.
We have obtained spectra of the lone H II region in AGC 198691 with the new high-throughput
KPNO Ohio State Multi-Object Spectrograph (KOSMOS) on the Mayall 4-m as well as with the Blue
Channel spectrograph on the MMT 6.5-m telescope. These observations enable the measurement of the
temperature-sensitive [O III]4363 line and hence the determination of a \direct" oxygen abundance
for AGC 198691. We nd this system to be an extremely metal-decient (XMD) system with an
oxygen abundance of 12+log(O/H) = 7.02 0.03, making AGC 198691 the lowest-abundance starforming
galaxy known in the local universe. Two of the ve lowest-abundance galaxies known have
been discovered by the ALFALFA blind H I survey; this high yield of XMD galaxies represents a
paradigm shift in the search for extremely metal-poor galaxies.
TEMPORAL EVOLUTION OF THE HIGH-ENERGY IRRADIATION AND WATER CONTENT OF TRAPPI...Sérgio Sacani
The ultracool dwarf star TRAPPIST-1 hosts seven Earth-size transiting planets, some of which could
harbour liquid water on their surfaces. UV observations are essential to measure their high-energy
irradiation, and to search for photodissociated water escaping from their putative atmospheres. Our
new observations of TRAPPIST-1 Ly-α line during the transit of TRAPPIST-1c show an evolution of
the star emission over three months, preventing us from assessing the presence of an extended hydrogen
exosphere. Based on the current knowledge of the stellar irradiation, we investigated the likely history
of water loss in the system. Planets b to d might still be in a runaway phase, and planets within the
orbit of TRAPPIST-1g could have lost more than 20 Earth oceans after 8 Gyr of hydrodynamic escape.
However, TRAPPIST-1e to h might have lost less than 3 Earth oceans if hydrodynamic escape stopped
once they entered the habitable zone. We caution that these estimates remain limited by the large
uncertainty on the planet masses. They likely represent upper limits on the actual water loss because
our assumptions maximize the XUV-driven escape, while photodissociation in the upper atmospheres
should be the limiting process. Late-stage outgassing could also have contributed significant amounts
of water for the outer, more massive planets after they entered the habitable zone. While our results
suggest that the outer planets are the best candidates to search for water with the JWST, they also
highlight the need for theoretical studies and complementary observations in all wavelength domains
to determine the nature of the TRAPPIST-1 planets, and their potential habitability.
Keywords: planetary systems - Stars: individual: TRAPPIST-1
EXTINCTION AND THE DIMMING OF KIC 8462852Sérgio Sacani
To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star
over a wide wavelength range from the UV to the mid-infrared from October 2015 through December
2016, using Swift, Spitzer and at AstroLAB IRIS. The star faded in a manner similar to the longterm
fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period
reported is 22.1 ± 9.7 milli-mag yr−1
in the Swift wavebands, with amounts of 21.0 ± 4.5 mmag in
the groundbased B measurements, 14.0 ± 4.5 mmag in V , and 13.0 ± 4.5 in R, and a rate of 5.0 ± 1.2
mmag yr−1 averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at
& 3 σ by three different observatories operating from the UV to the IR. The presence of long-term
secular dimming means that previous SED models of the star based on photometric measurements
taken years apart may not be accurate. We find that stellar models with Tef f = 7000 - 7100 K and
AV ∼ 0.73 best fit the Swift data from UV to optical. These models also show no excess in the
near-simultaneous Spitzer photometry at 3.6 and 4.5 µm, although a longer wavelength excess from
a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of
the fading favors a relatively neutral color (i.e., RV & 5, but not flat across all the bands) compared
with the extinction law for the general ISM (RV = 3.1), suggesting that the dimming arises from
circumstellar material
WHERE IS THE FLUX GOING? THE LONG-TERM PHOTOMETRIC VARIABILITY OF BOYAJIAN’S ...Sérgio Sacani
We present ∼ 800 days of photometric monitoring of Boyajian’s Star (KIC 8462852) from the AllSky
Automated Survey for Supernovae (ASAS-SN) and ∼ 4000 days of monitoring from the All Sky
Automated Survey (ASAS). We show that from 2015 to the present the brightness of Boyajian’s Star
has steadily decreased at a rate of 6.3 ± 1.4 mmag yr−1
, such that the star is now 1.5% fainter than it
was in February 2015. Moreover, the longer time baseline afforded by ASAS suggests that Boyajian’s
Star has also undergone two brightening episodes in the past 11 years, rather than only exhibiting a
monotonic decline. We analyze a sample of ∼ 1000 comparison stars of similar brightness located in
the same ASAS-SN field and demonstrate that the recent fading is significant at & 99.4% confidence.
The 2015 − 2017 dimming rate is consistent with that measured with Kepler data for the time period
from 2009 to 2013. This long-term variability is difficult to explain with any of the physical models
for the star’s behavior proposed to date
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.
A rare case of FR I interaction with a hot X-ray bridge in the A2384 galaxy c...Sérgio Sacani
Clusters of varying mass ratios can merge and the process significantly disturbs
the cluster environments and alters their global properties. Active radio galaxies are
another phenomenon that can also affect cluster environments. Radio jets can interact
with the intra-cluster medium (ICM) and locally affect its properties. Abell 2384
(hereafter A2384) is a unique system that has a dense, hot X-ray filament or bridge
connecting the two unequal mass clusters A2384(N) and A2384(S). The analysis of its
morphology suggests that A2384 is a post-merger system where A2384(S) has already
interacted with the A2384(N), and as a result hot gas has been stripped over a ∼ 1
Mpc region between the two bodies. We have obtained its 325 MHz GMRT data,
and we detected a peculiar FR I type radio galaxy which is a part of the A2384(S).
One of its radio lobes interacts with the hot X-ray bridge and pushes the hot gas in
the opposite direction. This results in displacement in the bridge close to A2384(S).
Based on Chandra and XMM-Newton X-ray observations, we notice a temperature and
entropy enhancement at the radio lobe-X-ray plasma interaction site, which further
suggests that the radio lobe is changing thermal plasma properties. We have also
studied the radio properties of the FR I radio galaxy, and found that the size and
radio luminosity of the interacting north lobe of the FR I galaxy are lower than those
of the accompanying south lobe.
The gaia eso_survey_stellar_content_and_elemental_abundances_in_the_massive_c...Sérgio Sacani
Estudo sobre o conteúdo estelar e os elementos que estão presentes no aglomerado estelar aberto NGC 6705, também conhecido como Aglomerado do Pato Selvagem.
A higher efficiency_of_converting_gas_to_stars_push_galaxies_at_z_1_6_well_ab...Sérgio Sacani
Galáxias formando estrelas em taxas extremas a nove bilhões de anos atrás eram mais eficientes do que a média das galáxias atuais, descobriram os pesquisadores.
A maioria das estrelas acredita-se localizam-se na sequência principal onde quanto maior a massa da galáxia, mais eficiente ela é na formação de novas estrelas. Contudo, de vez em quando uma galáxia apresentará uma explosão de novas estrelas que brilham mais do que o resto. Uma colisão entre duas grandes galáxias é normalmente a causa dessas fases de explosões de formação de estrelas, onde o gás frio que reside nas grandes nuvens moleculares torna-se o combustível para sustentar essas altas taxas de formação de estrelas.
A questão que os astrônomos têm feito é se essas explosões de estrelas no início o universo foram o resultado de se ter um suprimento de gás abundante, ou se as galáxias convertiam o gás de maneira mais eficiente.
Um novo estudo, publicado no Astrophysical Journal Letters de 15 de Outubro, liderado por John Silverman, do Kavli Institute for Physics and Mathematics of the Universe, estudou o conteúdo do gás monóxido de carbono (CO) em sete galáxias de explosão de estrelas muito distantes, quando o universo tinha apenas 4 bilhões de anos de vida. Isso foi possível devido a capacidade do Atacama Large Millimiter/Submillimiter Array (ALMA), localizado no platô no topo da montanha no Chile, que trabalha para detectar as ondas eletromagnéticas no comprimento de onda milimétrico (importante para se estudar o gás molecular) e um nível de sensibilidade que só agora começa a ser explorado pelos astrônomos.
Os pesquisadores descobriram que a quantidade de gás CO emitido já tinha diminuído, mesmo apesar da galáxia continuar a formar estrelas em altas taxas. Essas observações são similares àquelas registradas para as galáxias de explosões de estrelas próximas da Terra atualmente, mas a quantidade da depleção de gás não foi tão rápida quanto se esperava. Isso levou os pesquisadores a concluírem que poderia haver um contínuo aumento na eficiência, dependendo em de quanto acima da taxa de se formar estrelas ela está da sequência principal.
The broad lined_type_ic_sn_2012_ap_and_the_nature_of_relatvistic_supernovae_l...Sérgio Sacani
Artigo mostra como os astrônomos deduziram que a supernova SN 2012ap, é o elo perdido que faltava para a construção completa da árvore genealógica das supernovas.
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.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 RpSérgio Sacani
Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical
mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed
as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple
groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this
planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the
target set, demonstrating the outflow extends at least 5.8 × 105 km or 7.5 Rp This detection is significantly longer
than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is
blueshifted by −23 km s−1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M⊕ Gyr−1
. Our
observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind.
However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or
differences in instrumental precision.
X-rays from a Central “Exhaust Vent” of the Galactic Center ChimneySérgio Sacani
Using deep archival observations from the Chandra X-ray Observatory, we present an analysis of
linear X-ray-emitting features located within the southern portion of the Galactic center chimney,
and oriented orthogonal to the Galactic plane, centered at coordinates l = 0.08◦
, b = −1.42◦
. The
surface brightness and hardness ratio patterns are suggestive of a cylindrical morphology which may
have been produced by a plasma outflow channel extending from the Galactic center. Our fits of the
feature’s spectra favor a complex two-component model consisting of thermal and recombining plasma
components, possibly a sign of shock compression or heating of the interstellar medium by outflowing
material. Assuming a recombining plasma scenario, we further estimate the cooling timescale of this
plasma to be on the order of a few hundred to thousands of years, leading us to speculate that a
sequence of accretion events onto the Galactic Black Hole may be a plausible quasi-continuous energy
source to sustain the observed morphology
GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
Accelerate your Kubernetes clusters with Varnish CachingThijs Feryn
A presentation about the usage and availability of Varnish on Kubernetes. This talk explores the capabilities of Varnish caching and shows how to use the Varnish Helm chart to deploy it to Kubernetes.
This presentation was delivered at K8SUG Singapore. See https://feryn.eu/presentations/accelerate-your-kubernetes-clusters-with-varnish-caching-k8sug-singapore-28-2024 for more details.
State of ICS and IoT Cyber Threat Landscape Report 2024 previewPrayukth K V
The IoT and OT threat landscape report has been prepared by the Threat Research Team at Sectrio using data from Sectrio, cyber threat intelligence farming facilities spread across over 85 cities around the world. In addition, Sectrio also runs AI-based advanced threat and payload engagement facilities that serve as sinks to attract and engage sophisticated threat actors, and newer malware including new variants and latent threats that are at an earlier stage of development.
The latest edition of the OT/ICS and IoT security Threat Landscape Report 2024 also covers:
State of global ICS asset and network exposure
Sectoral targets and attacks as well as the cost of ransom
Global APT activity, AI usage, actor and tactic profiles, and implications
Rise in volumes of AI-powered cyberattacks
Major cyber events in 2024
Malware and malicious payload trends
Cyberattack types and targets
Vulnerability exploit attempts on CVEs
Attacks on counties – USA
Expansion of bot farms – how, where, and why
In-depth analysis of the cyber threat landscape across North America, South America, Europe, APAC, and the Middle East
Why are attacks on smart factories rising?
Cyber risk predictions
Axis of attacks – Europe
Systemic attacks in the Middle East
Download the full report from here:
https://sectrio.com/resources/ot-threat-landscape-reports/sectrio-releases-ot-ics-and-iot-security-threat-landscape-report-2024/
JMeter webinar - integration with InfluxDB and GrafanaRTTS
Watch this recorded webinar about real-time monitoring of application performance. See how to integrate Apache JMeter, the open-source leader in performance testing, with InfluxDB, the open-source time-series database, and Grafana, the open-source analytics and visualization application.
In this webinar, we will review the benefits of leveraging InfluxDB and Grafana when executing load tests and demonstrate how these tools are used to visualize performance metrics.
Length: 30 minutes
Session Overview
-------------------------------------------
During this webinar, we will cover the following topics while demonstrating the integrations of JMeter, InfluxDB and Grafana:
- What out-of-the-box solutions are available for real-time monitoring JMeter tests?
- What are the benefits of integrating InfluxDB and Grafana into the load testing stack?
- Which features are provided by Grafana?
- Demonstration of InfluxDB and Grafana using a practice web application
To view the webinar recording, go to:
https://www.rttsweb.com/jmeter-integration-webinar
The Art of the Pitch: WordPress Relationships and SalesLaura Byrne
Clients don’t know what they don’t know. What web solutions are right for them? How does WordPress come into the picture? How do you make sure you understand scope and timeline? What do you do if sometime changes?
All these questions and more will be explored as we talk about matching clients’ needs with what your agency offers without pulling teeth or pulling your hair out. Practical tips, and strategies for successful relationship building that leads to closing the deal.
Neuro-symbolic is not enough, we need neuro-*semantic*Frank van Harmelen
Neuro-symbolic (NeSy) AI is on the rise. However, simply machine learning on just any symbolic structure is not sufficient to really harvest the gains of NeSy. These will only be gained when the symbolic structures have an actual semantics. I give an operational definition of semantics as “predictable inference”.
All of this illustrated with link prediction over knowledge graphs, but the argument is general.
Key Trends Shaping the Future of Infrastructure.pdfCheryl Hung
Keynote at DIGIT West Expo, Glasgow on 29 May 2024.
Cheryl Hung, ochery.com
Sr Director, Infrastructure Ecosystem, Arm.
The key trends across hardware, cloud and open-source; exploring how these areas are likely to mature and develop over the short and long-term, and then considering how organisations can position themselves to adapt and thrive.
"Impact of front-end architecture on development cost", Viktor TurskyiFwdays
I have heard many times that architecture is not important for the front-end. Also, many times I have seen how developers implement features on the front-end just following the standard rules for a framework and think that this is enough to successfully launch the project, and then the project fails. How to prevent this and what approach to choose? I have launched dozens of complex projects and during the talk we will analyze which approaches have worked for me and which have not.
Essentials of Automations: Optimizing FME Workflows with ParametersSafe Software
Are you looking to streamline your workflows and boost your projects’ efficiency? Do you find yourself searching for ways to add flexibility and control over your FME workflows? If so, you’re in the right place.
Join us for an insightful dive into the world of FME parameters, a critical element in optimizing workflow efficiency. This webinar marks the beginning of our three-part “Essentials of Automation” series. This first webinar is designed to equip you with the knowledge and skills to utilize parameters effectively: enhancing the flexibility, maintainability, and user control of your FME projects.
Here’s what you’ll gain:
- Essentials of FME Parameters: Understand the pivotal role of parameters, including Reader/Writer, Transformer, User, and FME Flow categories. Discover how they are the key to unlocking automation and optimization within your workflows.
- Practical Applications in FME Form: Delve into key user parameter types including choice, connections, and file URLs. Allow users to control how a workflow runs, making your workflows more reusable. Learn to import values and deliver the best user experience for your workflows while enhancing accuracy.
- Optimization Strategies in FME Flow: Explore the creation and strategic deployment of parameters in FME Flow, including the use of deployment and geometry parameters, to maximize workflow efficiency.
- Pro Tips for Success: Gain insights on parameterizing connections and leveraging new features like Conditional Visibility for clarity and simplicity.
We’ll wrap up with a glimpse into future webinars, followed by a Q&A session to address your specific questions surrounding this topic.
Don’t miss this opportunity to elevate your FME expertise and drive your projects to new heights of efficiency.
Let's dive deeper into the world of ODC! Ricardo Alves (OutSystems) will join us to tell all about the new Data Fabric. After that, Sezen de Bruijn (OutSystems) will get into the details on how to best design a sturdy architecture within ODC.
GraphRAG is All You need? LLM & Knowledge GraphGuy Korland
Guy Korland, CEO and Co-founder of FalkorDB, will review two articles on the integration of language models with knowledge graphs.
1. Unifying Large Language Models and Knowledge Graphs: A Roadmap.
https://arxiv.org/abs/2306.08302
2. Microsoft Research's GraphRAG paper and a review paper on various uses of knowledge graphs:
https://www.microsoft.com/en-us/research/blog/graphrag-unlocking-llm-discovery-on-narrative-private-data/
Builder.ai Founder Sachin Dev Duggal's Strategic Approach to Create an Innova...Ramesh Iyer
In today's fast-changing business world, Companies that adapt and embrace new ideas often need help to keep up with the competition. However, fostering a culture of innovation takes much work. It takes vision, leadership and willingness to take risks in the right proportion. Sachin Dev Duggal, co-founder of Builder.ai, has perfected the art of this balance, creating a company culture where creativity and growth are nurtured at each stage.
Connector Corner: Automate dynamic content and events by pushing a buttonDianaGray10
Here is something new! In our next Connector Corner webinar, we will demonstrate how you can use a single workflow to:
Create a campaign using Mailchimp with merge tags/fields
Send an interactive Slack channel message (using buttons)
Have the message received by managers and peers along with a test email for review
But there’s more:
In a second workflow supporting the same use case, you’ll see:
Your campaign sent to target colleagues for approval
If the “Approve” button is clicked, a Jira/Zendesk ticket is created for the marketing design team
But—if the “Reject” button is pushed, colleagues will be alerted via Slack message
Join us to learn more about this new, human-in-the-loop capability, brought to you by Integration Service connectors.
And...
Speakers:
Akshay Agnihotri, Product Manager
Charlie Greenberg, Host
Kubernetes & AI - Beauty and the Beast !?! @KCD Istanbul 2024Tobias Schneck
As AI technology is pushing into IT I was wondering myself, as an “infrastructure container kubernetes guy”, how get this fancy AI technology get managed from an infrastructure operational view? Is it possible to apply our lovely cloud native principals as well? What benefit’s both technologies could bring to each other?
Let me take this questions and provide you a short journey through existing deployment models and use cases for AI software. On practical examples, we discuss what cloud/on-premise strategy we may need for applying it to our own infrastructure to get it to work from an enterprise perspective. I want to give an overview about infrastructure requirements and technologies, what could be beneficial or limiting your AI use cases in an enterprise environment. An interactive Demo will give you some insides, what approaches I got already working for real.
Slack (or Teams) Automation for Bonterra Impact Management (fka Social Soluti...Jeffrey Haguewood
Sidekick Solutions uses Bonterra Impact Management (fka Social Solutions Apricot) and automation solutions to integrate data for business workflows.
We believe integration and automation are essential to user experience and the promise of efficient work through technology. Automation is the critical ingredient to realizing that full vision. We develop integration products and services for Bonterra Case Management software to support the deployment of automations for a variety of use cases.
This video focuses on the notifications, alerts, and approval requests using Slack for Bonterra Impact Management. The solutions covered in this webinar can also be deployed for Microsoft Teams.
Interested in deploying notification automations for Bonterra Impact Management? Contact us at sales@sidekicksolutionsllc.com to discuss next steps.
Mission to Decommission: Importance of Decommissioning Products to Increase E...
Aa17709 11
1. A&A 539, A157 (2012) Astronomy
DOI: 10.1051/0004-6361/201117709 &
c ESO 2012 Astrophysics
Lithium and sodium in the globular cluster M 4
,
Detection of a Li-rich dwarf star: preservation or pollution?
L. Monaco1 , S. Villanova2 , P. Bonifacio3 , E. Caffau4,3, , D. Geisler2 , G. Marconi1 ,
Y. Momany 1 , and H.-G. Ludwig4,3
1
European Southern Observatory, 19001 Casilla, Santiago, Chile
e-mail: lmonaco@eso.org
2
Universidad de Concepción, 160-C Casilla, Concepción, Chile
3
GEPI, Observatoire de Paris, CNRS, Univ. Paris Diderot, Place Jules Janssen, 92190 Meudon, France
4
Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Königstuhl 12, 69117 Heidelberg, Germany
Received 15 July 2011 / Accepted 27 January 2012
ABSTRACT
Context. The abundance inhomogeneities of light elements observed in globular clusters (GCs), and notably the ubiquitous Na-O
anti-correlation, are generally interpreted as evidence that GCs comprise several generations of stars. There is an on-going debate as
to the nature of the stars, which produce the inhomogeneous elements, and investigating the behavior of several elements is a way to
shed new light on this problem.
Aims. We aim at investigating the Li and Na content of the GC M 4, that is known to have a well defined Na-O anti-correlation.
Methods. We obtained moderate resolution (R = 17 000–18 700) spectra for 91 main sequence (MS)/sub-giant branch stars of M 4
with the Giraffe spectrograph at the FLAMES/VLT ESO facility. Using model atmospheres analysis we measured lithium and sodium
abundances.
Results. We detect a weak Li-Na anti-correlation among un-evolved MS stars. One star in the sample, # 37934, shows the remarkably
high lithium abundance A(Li) = 2.87, compatible with current estimates of the primordial lithium abundance.
Conclusions. The shallow slope found for the Li-Na anti-correlation suggests that lithium is produced in parallel to sodium. This
evidence, coupled with its sodium-rich nature, suggests that the high lithium abundance of star # 37934 may originate by pollution
from a previous generations of stars. The recent detection of a Li-rich dwarf of pollution origin in the globular cluster NGC 6397 may
also point in this direction. Still, no clear cut evidence is available against a possible preservation of the primordial lithium abundance
for star # 37934.
Key words. nuclear reactions, nucleosynthesis, abundances – stars: abundances – stars: Population II – galaxies: abundances –
globular clusters: individual: M4 – cosmology: observations
1. Introduction reactions, which may give rise to the observed anomalies (e.g.
the Na enrichment), that it became necessary to accept that
For many years astronomers have assumed Galactic globular multiple stellar populations have contributed to the present day
clusters (GCs) as an example of single stellar population, which chemical composition of GCs. Different scenarios and possible
constitutes the ideal test-bench for stellar evolution theories. polluters from which multiple populations in GCs may origi-
This view came about mainly by considering the narrow red nate have been proposed and, in this respect, gathering infor-
giant branches (RGB), which characterize the color–magnitude mation about different chemical species is crucial to consolidate
diagrams (CMDs) of such systems. A theoretical isochrone of a the observational framework and constrain the models (see, e.g.,
single metallicity and age, typically fits well the observed color- Decressin et al. 2007; Ventura & D’Antona 2010; D’Ercole et al.
magnitude diagrams. Disturbing information, such as the scatter 2010; Valcarce & Catelan 2011).
in Na abundances in M3 and M13 noted by Cohen (1978) or the
variation in CN or CH strengths (Norris 1981; Norris & Freeman Further evidence on the complex nature of GCs has been
1983) or other chemical inhomogeneities which emerged from accumulating in recent years. Besides the spectacular case of
spectroscopic analysis, were typically blamed on mixing pro- ω Cen (see, e.g., Villanova et al. 2007, and references therein),
cesses in the RGB stars. It was only when it was shown that which is now commonly considered as the remnant nucleus of an
chemical inhomogeneities persist down to turn-off stars (TO, accreted dwarf galaxy, recent high accuracy CMDs obtained us-
Hesser 1978; Cannon et al. 1998; Gratton et al. 2001), which ing ACS at HST data, have revealed that several among the most
in their centers have temperatures too low to allow the nuclear massive globular clusters (NGC 2808, NGC 1851, NGC 6388,
NGC 6441) present photometric evidence for multiple sequences
at the main sequence (MS) and/or sub-giant branch (SGB) level
Based on observations taken at ESO VLT Kueyen telescope (Cerro
Paranal, Chile, program: 085.D-0537A). (see Piotto 2008, for a review).
Table A.1 is available in electronic form at Globular Clusters are among the oldest objects in the uni-
http://www.aanda.org verse and, in spite of the mentioned chemical anomalies, the first
Gliese Fellow. generation (FG) of stars in GCs is, however, easily identified by
Article published by EDP Sciences A157, page 1 of 7
2. A&A 539, A157 (2012)
to M 4 stars, while 15 fibers were assigned to positions selected
for sky subtraction. Sky holes were selected at similar radial dis-
tances from the clusters center as the science targets and the aver-
age of the 15 sky fibers was subtracted from the science spectra.
The standard IRAF2 task fxcor was employed to measure the
stellar radial velocities by cross-correlating the spectra with syn-
thetic ones of similar atmospheric parameters. Corrections to the
heliocentric system were computed using the IRAF task rvcor-
rect and applied to the observed radial velocities. After being
reduced to rest frame, multiple spectra of the same target were
finally averaged. We obtain spectra with a signal-to-noise ratio
(S/N) in the range 72–152 and 19–65 at the Li resonance dou-
blet and the Na-D doublet, respectively. A sample of the obtained
spectra in the Li resonance doublet region is presented in Fig. 1
(right panel).
We obtain a cluster mean radial velocity and dispersion of
vhelio = 71.4 ± 0.4 km s−1 , σ = 3.7 ± 0.2 km s−1 , after excluding
three stars, deviating more than 3-σ from the mean, and five stars
presenting discordant T eff as estimated from the B − V and V − I
colors (see below). These values are in good agreement with the
recent measures by Marino et al. (2008) and Lovisi et al. (2010).
Fig. 1. Left panel: V vs. B − V M 4 color–magnitude diagram. Target
stars are marked by open circles. Filled triangles mark the location of 3. Abundance analysis
the target as projected on the cluster mean ridge line. Target # 37934 The cluster photometry we adopt in this contribution is based
is marked by the star symbol. Right panel: summed spectra for a
on data collected with the Wide Field Imager (WFI) mounted
subsample of the target stars.
at the 2.2 m telescope at the La Silla observatory, which was
reduced following Momany et al. (2003) and was first corrected
its low Na content. It is interesting in this context that all of the for differential reddening following the recipe by Sarajedini et al.
GCs studied so far (ω Cen, NGC 6752, NGC 6397, 47 Tuc, M 4, (2007). We derived the target stars effective temperatures (T eff )
see Monaco et al. 2010; Mucciarelli et al. 2011, and references from the B − V and V − I colors as projected on the mean cluster
therein), present – at least in their FG of stars – a Li content ridge line and using the Alonso et al. (1996) calibrations. We
comparable to that of warm metal-poor halo dwarfs, i.e. the so- adopted for the cluster a mean reddening of E(B − V) = 0.36
called Spite plateau (Spite & Spite 1982; Sbordone et al. 2010). (Harris 1996). The projection we applied is meant to provide
The simplest interpretation of the Spite plateau is that the lithium a more robust determination of the targets colors, particularly
observed in these old stars is the lithium produced during the given the presence of a significant differential reddening in the
Big Bang (Iocco et al. 2009). If this is the case, however, there cluster. Indeed, we obtain a good agreement between the T eff
is a “cosmological lithium problem”, because the level of the derived from the B−V and V−I colors and we eventually adopted
Spite plateau is a factor of three to five lower than the primordial their average. Five stars were excluded from the sample, because
lithium predicted by Standard Big Bang Nucleosynthesis and the of their discrepant positions in the V vs. B − V and V vs. V − I
baryonic density measured from the fluctuations of the Cosmic CMDs, which converted in temperatures derived from the B − V
Microwave Background (see, e.g., Monaco et al. 2010; Sbordone and V − I colors different by more than 100 K.
et al. 2010, and references therein). We also estimated the stellar T eff by fitting for each star the
In this paper, we report the results of our investigation of Hα line with synthetic profiles calculated using the SYNTHE
the lithium and sodium abundances in MS/SGB stars in the code (Sbordone et al. 2004; Sbordone 2005; Kurucz 2005). The
GC M 4, based on FLAMES-GIRAFFE/VLT spectra (Pasquini two temperature scales are in excellent agreement, with a mean
et al. 2002). difference of −6 ± 5 K (σΔ(T eff ) = 60 K). The accuracy of the
T eff determination using Hα line fitting is usually, however, of
2. Observations and data reduction the order of ∼150 K and is dominated by uncertainties in the
continuum normalization and/or in the correction of the blaze
We observed stars along the M 4 MS and SGB using the function of the spectrograph (Bonifacio et al. 2007; Sbordone
FLAMES/GIRAFFE spectrograph at ESO Paranal (open circles et al. 2010; Monaco et al. 2010). In the following we will adopt
in the left panel of Fig. 1). Observations were conducted in ser- 150 K as uncertainty on the T eff determination.
vice mode between April and July 2010 using the HR12 and Surface gravities were determined with the aid of theoretical
HR15N settings. The former covers the Na-D doublet at a reso- isochrones and vary in the range log g = 3.48–4.13. In order
lution of 18 700. The HR15N setting covers the Li i resonance to determine the stellar micro-turbulent velocity (ξ), stars were
doublet at 670.8 nm, as well as the Hα region at a resolution first grouped by T eff in four sub-samples. For each sub-sample,
of 17 000. The same plate configuration was used for both set- a high S/N mean spectrum was generated averaging together
tings. Each target was observed for ∼2.3 h and ∼10 h total in- all the spectra. ξ was then fixed, as usual, by minimizing the
tegration time in the two settings, respectively. Frames were
2
processed using version 2.13 of the FLAMES/GIRAFFE data IRAF is distributed by the National Optical Astronomy
reduction pipeline1. Ninety-nine medusa fibers were allocated Observatories, which is operated by the association of Universities for
Research in Astronomy, Inc., under contract with the National Science
1
http://girbldrs.sourceforge.net/ Foundation.
A157, page 2 of 7
3. L. Monaco et al.: Lithium and sodium in M 4
dependence of the derived abundances on the measured equiv-
alent widths (EWs), for a selected sample of iron lines. The
Marino et al. (2008) line-list was employed for this purpose and
EWs were measured by Gaussian fitting. The derived trend of ξ
as a function of T eff was used to assign individual ξ values to the
target stars.
We adopted the above atmospheric parameters to calculate
proper ATLAS–9 model atmospheres which we used, along with
the MOOG code (Sneden 1973), to derive the Fe and Na abun-
dances. For each star, iron abundances were measured using the
two lines at 6995.0 Å and 6678.0 Å. We obtain a mean [Fe/H] =
−1.31 ± 0.03 dex (Gaussian dispersion for 71 stars) for MS stars
at T eff > 5880 K. This value raises to [Fe/H] = −1.17 ± 0.03 dex
for the 10 brighter/cooler stars in our sample (T eff < 5600 K).
This latter value is in fair agreement (within 0.1 dex) with previ-
ous estimates for RGB/SGB stars (Ivans et al. 1999; Marino et al.
2008; Carretta et al. 2009; Mucciarelli et al. 2011). Although
compatible within the errors ( 0.10–0.15 dex for both studies),
the [Fe/H] we measure for MS stars is substantially lower than
the figure obtained by Mucciarelli et al. (2011, hereafter M11)
for TO stars ([Fe/H] = −1.08). This is likely due to the differ-
ent assumptions made about the stellar micro-turbulent veloc-
ities. The possible variation of the iron content with the evo-
Fig. 2. Measured lithium abundances for targets on the main
lutionary stage will be analyzed in a forthcoming contribution sequence/sub-giant branch as a function of the effective temperature
(Villanova et al., in prep.). Na abundances were determined from (upper panel) and the sodium content (lower panel, stars at T eff >
the EWs of the Na D lines at 5889.9 Å and 5895.9 Å and apply- 5880 K only). The primordial lithium level implied by WMAP mea-
ing the corrections tabulated by Gratton et al. (1999) for non- sures plus SBBN theory (shaded area) is also marked for reference. In
LTE (NLTE) effects. We have also asked S. Andrievsky and the lower panel, filled squares indicate the mean Li content for the Na-
S. Korotin to perform some test computations using their sodium rich/Na-poor sub-samples. The continuous line is a least square fit to
model atom (Korotin & Mishenina 1999) and version of the the individual data. In both panels, the big open star marks the position
multi code (Korotin et al. 1998, 1999b), as done in Andrievsky of star # 37934.
et al. (2007). Their computed NLTE corrections are very similar
to those we computed interpolating in the table of Gratton et al. with temperature is present among the stars of this sub-sample.
(1999). M11 derived A(Li) = 2.30 ± 0.10 dex for the 35 TO stars
We derived stellar lithium abundances from the equivalent in their sample having T eff > 5900 K. The two values are com-
patible with each other, particularly considering the different
width (EW) of the Li i resonance doublet at 6708 Å using the
T eff scales adopted, the spectral S/N, and the different CMD re-
Sbordone et al. (2010) formula B.13 , which takes into account
gions sampled. The iron content has an impact on the Li abun-
3D (CO5BOLD) and NLTE effects4 . We remark that the exact
dances derived through formula B.1. However, an increase of
value adopted for the stellar surface gravity, ξ, and iron abun-
Δ [Fe/H] = +0.25 dex would correspond to a negligible decrease
dance have minimal impact on the derived Li abundances, which
of the lithium abundance of Δ A(Li) = −0.003 dex.
are, instead dominated by the uncertainty in the adopted T eff and
in the measured EWs. We estimated the uncertainty for the lat-
ter according to the Cayrel formula (Cayrel 1988) to be 2–3 mÅ, 4. Discussion
corresponding to 0.06–0.09 dex (Bonifacio et al. 2007). Adding
in quadrature to the error implied by a variation of ΔT eff = Our main results are summarized in the lower panel of Fig. 2,
±150 K, i.e. an additional 0.09 dex, we end up with a total un- where we restrict our analysis to MS stars only (T eff > 5880 K,
certainty on the Li determination of the order of 0.11–0.13 dex, 71 stars). The cluster stars display a very mild Li-Na anti-
which we round up to a conservative 0.15 dex. We adopt the correlation. Compared to NGC 6752, in which a spread of
same error estimate for Fe and Na abundances as well. 0.6 dex in [Na/Fe] corresponds to a spread of 0.6 dex in A(Li)
The upper panel of Fig. 2 presents the derived Li abundances (Pasquini et al. 2005), the anti-correlation in M 4 is hardly
as a function of the stellar T eff . The Li content is relatively con- detectable, with a spread of 0.1 dex in A(Li) corresponding
stant at the hottest temperatures and decreases with the temper- to a spread of 0.6 dex in A(Na). The sample has, however, a
ature for SGB stars. The observed trend and mean abundances Spearman rank correlation coefficient of CS = −0.34, corre-
are compatible, within the quoted errors, to the M11 results. For sponding to a probability of 0.002 that the observed correlation
stars having T eff > 5880 K, and excluding # 37934 (70 stars), we is, in fact, spurious. This conclusion is also supported by an ad-
derive a mean lithium abundance of A(Li) = 2.13 ± 0.09 dex ditional non-parametric test (Kendall’s tau), as well as by para-
(Gaussian dispersion). No correlation of the lithium abundance metric ones. We consider the results of the non-parametric tests
as more robust since parametric tests hinge on the correctness of
3
IDL routines implementing the fitting formulas are available at: the underlying model – the assumed functional relationship be-
http://mygepi.obspm.fr/~sbordone/fitting.html tween the variables. On request of the referee, we nevertheless
4
We computed ad-hoc 3D-NLTE line profile for star # 37934, whose also provide the outcome of the parametric tests (see appendix).
EW is in the extrapolation regime of the formula. We found negligible Notice, however, that we detected a very shallow slope and the
differences (0.003 dex) with respect to the value computed with for- conclusion we draw below are thus equally applicable to the case
mula B.1. of a non detection of a Na-Li anti-correlation.
A157, page 3 of 7
4. A&A 539, A157 (2012)
It would be tempting to interpret the detected anti-correlation It is currently accepted that the constant Li abundance displayed
by a simple pollution scenario, by which varying quantities of by warm metal-poor stars, the so-called Spite plateau (Spite &
Na-rich/Li-poor material are mixed with “pristine” material. In Spite 1982), falls short by a factor of three to five of the pri-
the case of NGC 6752, it was already pointed out by Shen et al. mordial lithium abundance (see Sbordone et al. 2010, and ref-
(2010), however, that such a scenario would imply a slope of erences therein). With the exception of star # 37934, the picture
one in the A(Li)–A(O) correlation. The fact that the observed we are facing in M 4 is in fact similar to what we see among
slope is significantly different from unity implies that the ma- field stars (the mild Li-Na anti-correlation is hardly significant
terial is not totally depleted in Li, requiring a production of in this context, see also M11 and Monaco et al. 2010). Notice
some Li along with Na. In the same vein, we may argue that that the Robin et al. (2003) model predicts no Galactic stars over
the fact that clusters like NGC 6752 and M 4 show similar Na-O a one square degree area in the M 4 line of sight with color,
anti-correlations (Marino et al. 2008) but different Li-Na anti- magnitude, radial velocity and metallicity similar to # 37934,
correlations, suggests that these anti-correlations arise from the within ±0.1 mag, ±0.5 mag, ±3 σ and ±0.5 dex, in each variable,
operation of different nuclear reactions, which take place at dif- respectively.
ferent places, and possibly at different times. If Li were sim- Two metal-poor dwarf stars that lie significantly above the
ply destroyed along with Na production, we should always find Spite plateau are known, BD +23◦ 3912 (Bonifacio & Molaro
the same slope of the Li-Na anti-correlation. On the contrary, 1997) and HD 106038 (Asplund et al. 2006). These stars have
we need to postulate that Li is produced with different effi- lithium abundance differences with respect to the cosmological
ciency in different clusters, to explain the absence of a slope value similar as # 37934, but at abundances lower than the cos-
in NGC 6397 (Lind et al. 2009), the mild slope in M 4 and mological value (A(Li) = 2.72). The 1D-NLTE lithium abun-
the marked slope in NGC 6752. Notice also that the observed dances of the three stars are A(Li) = 2.83, 2.59 and 2.48 for
slopes do not change in direct correlation with the cluster metal- # 37934, BD +23◦ 3912 and HD 106038, respectively. Notice
licities. Indeed, D’Orazi & Marino (2010, hereafter D10) and that adopting the recent temperature calibrations by González
M11 reached similar conclusions based on the non-detection Hernández & Bonifacio (2009), we obtain a temperature 116 K
of a Li-Na/Li-O anti-correlation/correlation among a sample of hotter for star #37934 and a corresponding 1D-NLTE abun-
RGB/TO stars. The two groups of Na-poor/Na-rich stars (ar- dance of A(Li) = 2.92. Stars in this metallicity range could
bitrarily separated at [Na/Fe] = 0.25) have different dispersion already start to feel the effect of the Galactic enrichment in
around the mean of 0.06 and 0.10, respectively, to be compared lithium (Romano et al. 1999, 2003). The remarkable difference
with the 0.06 and 0.14 reported by D10. between star # 37934 and BD +23 3912 or HD 106038, is the gap
D’Ercole et al. (2010) presented a class of models capable of in Li abundance with respect to the reference population: it is
reproducing the Na-O and Mg-Al anti-correlations, using AGB ∼0.7 dex for star # 37934 but only ∼0.3 dex for the other two
stars of the first generation as “polluters”. In their model for M 4, stars. HD 106038 displays other chemical peculiarities, such as
lithium is produced in parallel to the sodium production. These overabundance of Be (Smiljanic et al. 2008), Si, Ni, Y and Ba.
models are quite successful, but depend on several parameters Smiljanic et al. (2008) invoke a hypernova to explain such pecu-
and thus have the possibility of producing the different correla- liarities, without however, explaining how a star may form from
tions found in the different clusters. A necessary and key ingre- the undiluted hypernova ejecta. It is clear that such an exotic
dient is the dilution with pristine gas (D’Ercole et al. 2011). A explanation is not applicable to the case of GC stars, since the
different class of models, in which the “polluters” are fast ro- hypernova explosion would expel all gas from the Cluster, thus
tating massive stars (FRMS) has been presented by Decressin stopping star-formation.
et al. (2007, 2010). In this case there is no lithium production Also in NGC 6752 and 47 Tuc (Shen et al. 2010; D’Orazi
and lithium is purely destroyed in the massive stars. The ob- et al. 2010) there is one star, which, within errors, has a Li abun-
served lithium is the result of dilution of Li-free matter with dance compatible with the primordial abundance. In those cases,
pristine material. In a case like that of M 4 the material must however, the star lies along a well defined Li-O correlation so
clearly be almost pristine, otherwise the variation in Li would be that there is a continuity of Li abundances from the highest to
much larger. The observations of the simultaneous, significant the lowest. Here the situation is totally different, as there is no
variation in the Na content might pose a problem to the viability star with a Li content within a factor of 3 of that of # 37934.
of such models for M 4. Notice, however, that the recent results The nature of this star can be interpreted in different ways.
by Villanova & Geisler (2011) support FRMS as likely polluters It is currently a matter of debate whether the Spite Plateau orig-
from which the second generation of stars formed in M 4 (see inate from a depletion mechanism, which is experienced by the
also Yong et al. 2008; Lind et al. 2011). stars in a uniform way. Star # 37934 might have escaped this
Figure 2 shows another remarkable fact: there is one star, depletion which, instead, experienced all the other stars we sam-
# 37934, that displays a lithium abundance, which is signifi- pled. In this case the high Li abundance of # 37934 would rep-
cantly higher than that of the others. This star has in fact a resent a case of preservation of the primordial Li abundance. On
lithium content, which is compatible with the primordial lithium the other hand, this star might have followed the same fate of the
abundance, as derived from the baryonic density deduced from other stars but might have been created with a higher Li abun-
the fluctuations of the cosmic microwave background and stan- dance. Its high lithium content would then constitute a case of
dard Big Bang nucleosynthesis (Cyburt et al. 2008, shaded area pollution.
in Fig. 2). The strong Li line of this star can also be appreci- We believe it is hard to rule out any of the two interpretations.
ated in Fig. 1. We have checked individual frames and the strong In the first case we should identify a mechanism, which uni-
Li line is detected in all of them. Observations were conducted formly depletes lithium in all the cluster stars and another mech-
over a long period, which implies observations with different anism, which suppresses this depletion for star # 37934. In the
plates and at different geocentric velocities. Hence, different second case, although it is relatively easy to envisage Li produc-
fibers were used and the star spectrum moved on the CCD. This tion mechanisms, it is not so easy to imagine mechanisms which
guarantees that the detection is not spurious. It is natural to pose would allow this single star to be so much more lithium-rich than
the question whether it is a case of preservation or production. the others. The small slope of the Li-Na anti-correlation supports
A157, page 4 of 7
5. L. Monaco et al.: Lithium and sodium in M 4
Li production taking place in parallel to Na production. Together References
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Pages 6 to 7 are available in the electronic edition of the journal at http://www.aanda.org
A157, page 5 of 7