J/ApJ/920/152 Variable Stars in Local Group Galaxies. VI. (Neeley+, 2021)
Variable Stars in Local Group Galaxies.
VI. The Isolated Dwarfs VV 124 and KKr 25.
Neeley J.R., Monelli M., Marengo M., Fiorentino G., Vivas A.K., Walker A.,
Gallart C., Martinez-Vazquez C.E., Bono G., Cassisi S., Marconi M.,
Dall'Ora M., Sarajedini A.
<Astrophys. J., 920, 152 (2021)>
=2021ApJ...920..152N 2021ApJ...920..152N
ADC_Keywords: Galaxies, dwarf; Stars, variable; Photometry; Optical
Keywords: Dwarf galaxies ; Dwarf spheroidal galaxies ; Pulsating variable
stars ; RR Lyrae variable stars ; Cepheid variable stars ;
Anomalous Cepheid variable stars ; Population II Cepheid
variable stars
Abstract:
We present the discovery of variable stars in two isolated dwarf
galaxies in the outskirts of the Local Group, VV 124 and KKr 25, using
observations with the Hubble Space Telescope. VV 124 hosts stellar
populations with a wide range of ages (>10Gyr until the present) and
therefore we find all types of classical pulsators. In VV 124, we
detect a total of 771 variable stars, including 78 classical Cepheids,
10 anomalous Cepheids, one Type II Cepheid, 678 RR Lyrae stars, and
four eclipsing binaries. In KKr 25, we find 25 anomalous Cepheids, 46
RR Lyrae stars, and no classical Cepheids, thus the galaxy does not
have a strong young population. A comparison of the variables with
evolutionary tracks suggests that both galaxies may contain an
intrinsic spread in metallicity, but overall are fairly metal-poor. We
also present detailed simulations, which have been designed to
estimate the completeness of our variable catalog. Particularly in the
cases for which the observations are not deep enough to reach the
main-sequence turnoff, such as the more distant Local Group dwarf
galaxies, the techniques developed here can be used together with
relatively shallow color-magnitude diagrams to inform on the nature of
galactic populations over the full range of ages.
Description:
For this study, we obtained multi-epoch Hubble Space
Telescope/Advanced Camera for Surveys (HST/ACS) data of VV 124 and
KKr 25 (GO15244; PI Monelli). We obtained 14 (VV 124) and 16 (KKr 25)
exposures in each of the F475W and F814W filters, with a total time
baseline of ∼6 and ∼5days, respectively. The data were collected in
2019 January in the case of VV 124, and in July of the same year for
KKr 25.
Objects:
-----------------------------------------------
RA (2000) DE Designation(s)
-----------------------------------------------
09 16 02.01 +52 50 42.0 VV124 = EQ 0912+5303
16 13 47.50 +54 22 08.2 KKr 25= [KKR99] 25
-----------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 115 975 Summary of variables in KKr25 and VV124
fig3.dat 40 26141 Multi-epoch photometry of all confirmed and
candidate variable stars
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See also:
J/AJ/132/1361 : RR Lyrae variables in M33 (Sarajedini+, 2006)
J/ApJ/699/1742 : LCID project. I. Cetus and Tucana variables (Bernard+, 2009)
J/AJ/138/184 : RR Lyrae in 2 fields in M31 spheroid (Sarajedini+, 2009)
J/A+A/533/A37 : VI HST photometry of VV124 = UGC4879 (Bellazzini+, 2011)
J/ApJ/751/46 : Spectroscopic observations in VV124 (UGC4879) (Kirby+, 2012)
J/MNRAS/432/3047 : LCID project VIII. Cepheids of Leo A (Bernard+, 2013)
J/AcA/65/297 : OGLE4 LMC and SMC Cepheids (Soszynski+, 2015)
J/AcA/66/131 : VI light curves of SMC and LMC RR Lyrae (Soszynski+, 2016)
J/ApJ/850/137 : ISLAndS project. III. (Martinez-Vazquez+, 2017)
J/AJ/153/96 : Standard Galactic field RR Lyrae. I. Photo (Monson+, 2017)
J/AcA/67/297 : OGLE Galactic center Cepheids & RR Lyrae (Soszynski+, 2017)
J/AcA/68/89 : VI light curves of SMC type II Cepheids (Soszynski+, 2018)
J/MNRAS/496/5039 : Updated PA and PAC relations for Cepheids (De Somma+, 2020)
J/MNRAS/492/1061 : A DECam view of Crater II - Variable stars (Vivas+, 2020)
J/MNRAS/500/817 : Mid-infrared catalogue for LMC & SMC Cepheids (Chown+, 2021)
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Gal Name of galaxy
7- 10 A4 -- Star Variable name (1)
12- 14 A3 -- Class Variable class (2)
16- 17 A2 -- subtype variable mode or subclass (2)
19- 28 F10.6 deg RAdeg [138/244] Right ascension (J2000)
30- 38 F9.6 deg DEdeg [52/55] Declination (J2000)
40- 45 F6.4 [d] Per [0/9] log of the period in days
47- 52 F6.4 [d] e_Per [0.001/4]? error on the log of the period
54- 63 F10.4 d t0 [58490/58682] epoch of maximum
65- 69 F5.2 mag F475w [21.9/27.4] mean magnitude in the f475w filter
71- 74 F4.2 mag e_F475w [0.01/0.2]? error in F475w (3)
76- 79 F4.2 mag F475wamp [0.1/2] amplitude in the f475w filter
81- 84 F4.2 mag e_F475wamp [0.02/0.4]? error in F475wamp (3)
86- 89 F4.2 mag F475wsigma [0.01/0.32] standard deviation of the
residuals from template fit in f475w filter
91- 95 F5.2 mag F814w [21.9/27.4] mean magnitude in the f814w filter
97-100 F4.2 mag e_F814w [0.01/0.09]? error in F814w (3)
102-105 F4.2 mag F814wamp [0.1/1.23] amplitude in the f814w filter
107-110 F4.2 mag e_F814wamp [0.02/0.3]? error in f814wamp (3)
112-115 F4.2 mag F814wsigma [0.01/0.6] standard deviation of the residuals
from template fit in f814w filter
--------------------------------------------------------------------------------
Note (1): Stars named V** are confirmed variables. Stars named C** are
candidate variables, and their Parameters should be treated with
caution.
Note (2): Subtype column gives the pulsation mode for RR Lyrae stars (RRL),
Classical Cepheids (CEP), And Anomalous Cepheids (AC). For Type II
Cepheids (T2C) it gives the subclass, BL Herculis (BL) or W Virginis
(WV). Eclipsing binary stars (EB) give the subclass (EA, EW, or EB).
Stars where the period is Clearly longer than our baseline are marked LPV.
Note (3): Errors were calculated via simulations for each variable class.
Null errors are given when no simulations were performed (Eclipsing
Binaries) or no stars were reliably detected in the simulations (W
Virginis)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: fig3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 -- Gal Name of galaxy
7- 10 A4 -- Star Name of variable star (1)
12- 16 A5 -- Filt Filter of observation; F475W or F814W
18- 27 F10.4 d MJD [58490/58685] Modified Julian date of observation
JD-2400000.5
29- 34 F6.3 mag omag [20.9/28.5] Magnitude of observation in filter
36- 40 F5.3 mag e_omag [0.01/0.5] Photometric uncertainty of omag
--------------------------------------------------------------------------------
Note (1): Stars named V** are confirmed variables. Stars named C** are
candidate variables, and their Parameters should be treated with
caution.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
Martinez-Vazquez et al. Paper I : 2015MNRAS.454.1509M 2015MNRAS.454.1509M
Martinez-Vazquez et al. Paper II : 2016MNRAS.462.4349M 2016MNRAS.462.4349M Cat. J/MNRAS/462/4349
Monelli et al. Paper III : 2017ApJ...842...60M 2017ApJ...842...60M Cat. J/ApJ/842/60
Monelli et al. Paper IV : 2018MNRAS.479.4279M 2018MNRAS.479.4279M
Martinez-Vazquez et al. Paper V : 2021MNRAS.508.1064M 2021MNRAS.508.1064M
(End) Prepared by [AAS], Coralie Fix [CDS], 27-Feb-2024