This research summarizes an investigation into the evolutionary status of the enigmatic star RZ Piscium. The researchers searched for comoving companions to help determine if RZ Piscium is a pre-main sequence or post-main sequence star. They identified one candidate companion, J0109+2758, which has properties of an old M dwarf star. New spectroscopic observations from the Keck telescope found that J0109+2758 has a radial velocity inconsistent with RZ Piscium, ruling it out as a comoving companion. This provides further evidence that RZ Piscium is likely a young, pre-main sequence star.

1. RESEARCH POSTER PRESENTATION DESIGN © 2015
www.PosterPresentations.com
This research was supported in part by NASA Astrophysics Data Analysis program grant NNX16AG13G to RIT as well as funding from the National Science Foundation (NSF)
Award Number: 135936. Based on observations at Kitt Peak National Observatory, National Optical Astronomy Observatory (as part of the WIYN Consortium), which is operated
by the Association of Universities for Research in Astronomy (AURA) under cooperative agreement with the National Science Foundation. The authors are honored to be permitted
to conduct astronomical research on Iolkam Du'ag (Kitt Peak), a mountain with particular significance to the Tohono O'odham.1. In addition to Dr. Kastner and Kristina Punzi for
their extraordinary mentorship, we would like to thank Dr. Roger Dube of RIT for organizing the REU grant which allowed us to conduct this research.
OBJECTIVES AND METHODS
REFERENCES
BREAKING NEWS
ACKNOWLEDGEMENTS
Tori Knapp[1]
, Lydia Gingerich[2]
, Kristina Punzi[3]
, Joel Kastner[3]
, Carl Melis[4]
, Ben Zuckerman[5]
1) Ithaca College; 2) Haverford College; 3) Rochester Institute of Technology; 4) UC San Diego; 5) UCLA
The Evolutionary Status of the Enigmatic Field Star RZ Piscium:
A Search for Comoving Companions
Figure 1. Images showing RZ Psc and candidate J0109+2758. From L to R: WIYN (442 nm); 2MASS (1.235 microns); WISE (3.4 microns); XMM-PN (0.15-15 nm)
Figure 2. Isochrone tracks obtained using Z=0.0152, tracks shown are
between 3Myr-500Myr (isochrones downloaded from
"http://stev.oapd.inaf.it/cmd")[4]
. The x-axis and y-axis represent the
log(Teff
) and log(L/Lo
) respectively. RZ Psc and J0109+2758 are modeled at
150pc and 400pc (stars).
Figure 4. Proper Motions in RZ Psc Field within 30 arcmin – The x-axis
and y-axis represent the RA and DEC components (respectively) of proper
motion in milliarcsec. Point size is inversely proportional to distance from
RZ Psc (not including J0109+2758). J0109+2758 (blue and red diamonds)
is 2.3 arcmin from RZ Psc (blue and red stars). The largest circle (with PM
components +24, -6.4 mas) represents a star that is 9.5 arcmin from RZ
Psc; the second largest circle (PM components +17.8, -1 mas) represents
a star that is 19.9 arcmin from RZ Psc.
Table 1. Characteristics of Candidate J0109+2758 and RZ Psc
• Search of XMM-Newton images for X-ray bright sources in the field of
RZ Psc (search radius 15 arcminutes)
– Match candidates to objects in BVRI-band data, 2MASS and WISE
catalogues
– Conduct multi-aperture photometry in B, V, R, and I on optical
images obtained with the WIYN 0.9m telescope for candidate stars
• Fit Spectral Energy Distribution (SED) models[4]
to X-ray selected objects
in the visual to mid-infrared range (Figure 3)
• Compare cataloged field star proper motions to that of RZ Psc (Figure 4)
• Estimate Lx
/Lbol
for "surviving" (comoving) candidates
CLASSIFYING THE CANDIDATE
● Spectrum and velocity for J0109+2758 obtained from the
Echellette Spectrograph and Imager (ESI) on the 10m Keck
telescope on 18th
of November 2016.
○ Spectrum confirms J0109+2758 has a dwarf M star spectral
class (Figure 6); weak H-alpha emission (Figure 7) and no
detectable Li absorption (Figure 8) that would be indicative of
young star status.
○ J0109+2758’s RV measured as -33.5 +/- 1.5 km/s; RZ Psc
has a measured RV near 0 km/s (Punzi et al. in prep and refs.
therein)
● This finding rules out J0109+2758 as a comoving companion to
RZ Psc.
● Evidence is pointing more strongly at pre-main-sequence status
(see K. Punzi talk this meeting, abstract number 230.01).
● Gaia parallax (expected late 2017) will pin down the distance,
hence status, of RZ Psc:
○ predict D ~150 pc if pre-MS
○ predict D > 400 pc if post-MS
Figure 5. X-ray light curve for J0109+2758, using XMM-Newton EPIC PN
camera; wavelengths 0.15-15nm
[1] Punzi, et al. in prep..
[2] Potravnov, I. S., Grinin, V. P., Ilyin, I. V., & Shakhovskoy, D. N. 2014, A&A, 563, A139
[3] Kaminski ̆i, B. M., Kovalchuk, G. U., & Pugach, A. F. 2000, Astronomy Reports, 44, 611
[4] Bressan et al. (2012), MNRAS, 427, 127 + Chen et al. (2014, 2015), MNRAS, 444, 2525 +
MNRAS, 452, 1068 + Tang et al. (2014), MNRAS, 445, 4287
[5] Castelli and Kurucz’s 2004 Atlas of Stellar Atmosphere Models:
http://www.stsci.edu/hst/observatory/crds/castelli_kurucz_atlas.html
[5] Zuckerman, B., Melis, C., Song, I., et al. 2008, ApJ, 683, 1085
OVERVIEW
● RZ Psc: pre-main sequence or
post-main sequence?
○ optical "dropouts", IR excess, Li
absorption, large Lx
/Lbol
→ pre-main
sequence
○ no moving association/cluster →
post-main sequence
● To break degeneracy we used X-ray,
optical and IR imagery to identify late-type
field stars that could potentially be
comoving with RZ Psc
● Our search isolated a solitary late-type
M star with the potential of being a
comoving companion
● Newly obtained Keck Telescope
spectroscopy confirms spectral type but
yields a radial velocity inconsistent with
that of RZ Psc
● Evidence now supports RZ Psc’s
evolutionary status as a young (pre-main
sequence) star (see K. Punzi talk 230.01,
this meeting)
● Initial survey produced 7 candidates
● All seven were point matched within 2 arcsec in visible, near
IR, mid IR, and X-ray images (Figure 1)
● Multi-aperture photometry provided flux values to produce
SEDs
● Fluxes fit to stellar models with following results
○ A-type star
○ 2 G-type stars
○ K-type star
○ M-type star (Figure 3)
○ AGN
○ Confused star + AGN source
COMOVING FIELD STAR SEARCH: RESULTS
● Stellar photosphere model fit to photometric
data for J0109+2758 indicates its status as
an old M1 field star (Table 1)
● X-ray emission from J0109+2758 detected
in the form of a ~10 ks duration flare (Figure
4)
● If truly a comoving companion to RZ Psc,
then RZ Psc would likely be an evolved
giant
RZ Psc
J0109
Figure 6. Normalized spectrum of J0109+2753
from Keck/ESI observation confirming dwarf M
star spectral class
Figure 7. Normalized spectrum of J0109+2753
from Keck/ESI observation showing weak
H-alpha emission
Figure 8. Normalized spectrum of J0109+2753
from Keck/ ESI observation showing no Li
absorption
Figure 3. Comoving Candidate SED
(Model used for M stars with
temperature 3500 K, from Castelli
and Kurucz’s 2004 Atlas of Stellar
Atmosphere Models)[5]