J/A+A/678/A104 M80 anomalous variable stars (Molnar+, 2023)
To grow old and peculiar: Survey of anomalous variable stars in M80 with age
determination using K2 and Gaia.
Molnar L., Plachy E., Bodi A., Pal A., Joyce M., Kalup Cs., Johnson C.I.,
Dencs Z., Meszaros Sz., Netzel H., Kinemuchi K., Kollmeier J.A.,
Prieto J.L., Derekas A.
<Astron. Astrophys. 678, A104 (2023)>
=2023A&A...678A.104M 2023A&A...678A.104M (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, variable ; Photometry ;
Spectra, optical
Keywords: globular clusters: individual: M80 - stars: variables: RR Lyrae -
stars: variables: general - asteroseismology - stars: evolution
Abstract:
The globular cluster Messier 80 was monitored by the Kepler space
telescope for 80 days during the K2 mission. Continuous,
high-precision photometry of such an old, compact cluster allows us to
study its variable star population in unprecedented detail. We extract
light curves for 27 variable stars using differential-image
photometry. A search for new variables in the images led to the
discovery of two new variable stars: an RR Lyrae and a variable red
giant star, respectively. Analysis of the RR Lyrae population reveals
multiple RRc stars with additional modes and/or peculiar modulation
cycles. We newly classify star V28 as a spotted extreme horizontal
branch variable. Despite their faintness, we clearly detect the three
SX Phe stars but we did not find new pulsation modes beyond the known
ones in them. Spectra taken with the VLT and Magellan Clay telescopes,
as well as absolute color-magnitude diagrams of the cluster based on
Gaia and Pan-STARRS observations confirm the classification of the
peculiar modulated variables as bona-fide RRc stars. We propose that
they highlight a subgroup of overtone stars that may have been
overlooked before. We fit MESA isochrones to the CMDs to estimate the
age and metallicity of the cluster. We confirm that M80 is old and
metal-poor, but show that isochrone fitting to old populations comes
with numerous uncertainties.
Description:
Corrected K2 photometry of the variable stars in M80.
We obtained spectra from two telescopes for selected targets.
Observations were collected with the LDSS3 (Low Dispersion Survey
Spectrograph) instrument installed on the 6.5 m Magellan Clay
telescope at Las Campanas Observatory. Five RRc stars (V3, V4, V13,
V14, and V16) were observed on May 20, 2017.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea5.dat 136 27 Gaia absolute magnitudes, dereddened colors and
zeropoint-corrected parallaxes of sample stars
list.dat 90 5 List of fits spectra
fits/* . 5 Individual fits spectra
tablea1.dat 67 96519 M80 light curves
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See also:
J/AcA/63/91 : V-band light curves of variables in M80 (Kopacki, 2013)
Byte-by-byte Description of file: tablea5.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Type Type of variable (other for other variable)
8- 23 A16 --- ID Variable ID as in table A1
25- 43 I19 --- GaiaDR3 Gaia DR3 ID
45- 50 F6.3 mag GMAG Absolute G magnitude
52- 57 F6.3 mag (BP-RP)0 ?=- Dereddened BP-RP colour index
59- 63 F5.3 mag e_GMAG Absolute G magnitude error
65- 69 F5.3 mag e_(BP-RP)0 ?=- Dereddened BP-RP colour index error
71- 76 F6.3 mas plx ?=- Zeropoint-corrected parallax
78- 82 F5.3 mas e_plx ?=- Zeropoint-corrected parallax error
84-103 A20 --- Name Variable name
105-106 I2 h RAh Simbad right ascension (J2000)
108-109 I2 min RAm Simbad right ascension (J2000)
111-115 F5.2 s RAs Simbad right ascension (J2000)
117 A1 --- DE- Simbad declination sign (J2000)
118-119 I2 deg DEd Simbad declination (J2000)
121-122 I2 arcmin DEm Simbad declination (J2000)
124-127 F4.1 arcsec DEs Simbad declination (J2000)
129-136 F8.6 d Per ? Period (from table A2)
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- ID Identification of the star
5- 6 I2 h RAh Simbad right ascension (J2000)
8- 9 I2 min RAm Simbad right ascension (J2000)
11- 15 F5.2 s RAs Simbad right ascension (J2000)
17 A1 --- DE- Simbad declination sign (J2000)
18- 19 I2 deg DEd Simbad declination (J2000)
21- 22 I2 arcmin DEm Simbad declination (J2000)
24- 27 F4.1 arcsec DEs Simbad declination (J2000)
29- 32 I4 --- Nx Number of pixels along X-axis
34 I1 --- Ny ? Number of pixels along Y-axis
36- 45 A10 "datime" Obs.date Observation date
47- 50 I4 0.1nm bLAMBDA Lower value of wavelength interval
52- 55 I4 0.1nm BLAMBDA Upper value of wavelength interval
57- 58 I2 Kibyte size Size of FITS file
60- 71 A12 --- FileName Name of FITS file, in subdirectory fits
73- 90 A18 --- Title Title of the FITS file
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- ID Identification of the star
16- 26 F11.6 d BJD Kepler Barycentric Julian Date (BJD-2454833.0)
28- 35 F8.5 mag Kpmag Brightness in the Kepler passband
37- 43 F7.5 mag e_Kpmag Brightness uncertainty
45- 59 F15.3 e/s Flux Measured flux in the Kepler passband
61- 67 F7.3 e/s e_Flux Flux uncertainty
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Acknowledgements:
Laszlo Molnar, molnar.laszlo(at)csfk.org
(End) Patricia Vannier [CDS] 21-Sep-2023