J/A+A/677/A137 Stellar variability in Gaia DR3 (Maiz Apellaniz+, 2023)
Stellar variability in Gaia DR3.
I. Three-band photometric dispersions for 145 million sources.
Maiz Apellaniz J., Holgado G., Pantaleoni Gonzalez M., Caballero J.A.
<Astron. Astrophys. 677, A137 (2023)>
=2023A&A...677A.137M 2023A&A...677A.137M (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Magellanic Clouds ; Stars, variable ; Photometry ;
Optical
Keywords: stars: variables: general - techniques: photometric -
Galaxy: general - Magellanic Clouds
Abstract:
The unparalleled characteristics of Gaia photometry in terms of
calibration, stability, time span, dynamic range, full-sky
coverage, and complementary information make it an excellent choice to
study stellar variability.
To measure the photometric dispersion in the G+GBP+GRP bands of the
145677450 third Gaia data release (DR3) fiveparameter sources with
G≤17mag and GBP-GRP between ∼1.0 and 8.0mag. To use that unbiased
sample to analyze stellar variability in the Milky Way (MW), LMC, and
SMC.
For each band we convert from magnitude uncertainties to observed
photometric dispersions, calculate the instrumental component as a
function of apparent magnitude and color, and use it to transform the
observed dispersions into the astrophysical ones: SG, SGBP, and
SGRP. We give variability indices in the three bands for the whole
sample indicating whether the objects are nonvariable, marginally
variable, or clearly so.We use the subsample of Rimoldini et al. with
light curves and variability types to calibrate our results and
establish their limitations.
The position of an object in the dispersion-dispersion planes can be
used to constrain its variability type, a direct application of these
results.We use information from the MW, LMC, and SMC color-absolute
magnitude diagrams (CAMDs) to discuss variability across the
Hertzsprung-Russell diagram. White dwarfs and B-type subdwarfs are
more variable than main sequence (MS) or red clump (RC) stars, with a
flat distribution in SG up to 10mmag and with variability decreasing
for the former with age. The MS region in the Gaia CAMD includes a
mixture of populations from the MS itself and from other evolutionary
phases. Its SG distribution peaks at low values (∼1-2mmag) but
it has a large tail dominated by eclipsing binaries, RR Lyr stars, and
young stellar objects. RC stars are characterized by little
variability, with their sG distribution peaking at 1 mmag or less. The
stars in the pre-main-sequence (PMS) region are highly variable, with
a power law distribution in sG with slope 2.75 and a cuto for values
lower than 7mmag. The luminous red stars region of the Gaia CAMD has
the highest variability, with its extreme dominated by AGB stars and
with a power law in sG with slope 2.2 that extends from there to a
cuto of 7mmag. We show that our method can be used to search for LMC
Cepheids. We analyze four stellar clusters with O stars (Villafranca
O-016, O-021, O-024, and O-026) and detect a strong difference in SG
between stars that are already in the MS and those that are still in
the PMS.
Description:
We present the Gaia DR3 three-band photometric dispersions for
the 145 million sources brighter than G=17mag, normal colors, and
5-parameter astrometric solutions.
The published Gaia DR3 magnitudes are the weighted averages
of a large number of individual measurements. Two measurements of the
same star are not identical due to a combination of instrumental and
astrophysical (or intrinsic) variability. The first one can be
approximated as a Gaussian distribution, keeping in mind the
possibility of outliers (an issue we come back to below). As for the
astrophysical variability, the measured magnitudes can have quite
different distributions, from symmetrical but non-Gaussian in cases
such as ellipsoidal variables to asymmetrical in most eclipsing
binaries or bursting sources. However, under the reasonable assumption
that both are independent, the relationship between the observed
dispersion sX;0 and the astrophysical SX and instrumental SX,ins
dispersions for a band X (G, GBP, or GRP) is given by:
SX,02 = SX2 + SX,ins2
where SX,0 itself is the product of the listed magnitude uncertainty
σX) by SQRT(NX-1). NX is the number of observations used
for photometry, as X is the (weighted) standard deviation of the mean
of the distribution (Eqn. 5 in Riello et al., 2021A&A...649A...3R 2021A&A...649A...3R).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 403 145677450 Gaia DR3 three-band photometric dispersions
catalog
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/A+A/619/A180 : Gaia DR2 photometric sensitivity curves (Maiz Apellaniz+ 2018)
J/A+A/649/A3 : Gaia Early Data Release 3 photometric passbands (Riello+ 2021)
J/A+A/674/A25 : Gaia DR3. spurious signals (Holl+, 2023)
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 28 A28 --- Name Gaia DR3 name (ID)
30- 44 F15.11 deg RAdeg Gaia DR3 right ascension (ICRS) at Ep=2016.0
(RA)
46- 60 F15.11 deg DEdeg Gaia DR3 declination (ICRS) at Ep=2016.0 (DEC)
62- 69 F8.5 mag Gmag Gaia DR3 G magnitude (G)
71- 79 F9.6 mag BP-RP Gaia DR3 BP-RP colour (BPMRP)
81- 90 F10.6 --- Cstar Photometric contamination parameter
(CSTAR) (1)
92-100 F9.5 mas plx Corrected Gaia DR3 parallax (PICOR)
102-109 F8.6 mas e_plx Corrected Gaia DR3 parallax uncertainty
(SPICOR)
111-120 F10.6 mag GMAG ?=99.999001 Gaia DR3 absolute G magnitude
(GABS)
122 A1 --- Gal [MLS] Galaxy (M = Milky Way, L = LMC, S = SMC)
(GAL)
124-134 F11.6 --- SG0 Observed dispersion for band G, SG,0 (SG0)
136-146 F11.6 --- SG Astrohpysical dispersion for band G,
SG (SG)
148-156 F9.6 --- SSG Astrophysical dispersion uncertainty
for band G, σSG (SSG)
158-165 F8.5 --- SIG Instrumental dispersion for band G,
SG,i (SIG)
167-177 F11.6 --- SBP0 Observed dispersion for band GBP,
SBP,0 (SBP0)
179-189 F11.6 --- SBP Astrohpysical dispersion for band GBP,
SBP (SBP)
191-199 F9.6 --- SSBP Astrophysical dispersion uncertainty
for band GBP, σSBP (SSBP)
201-209 F9.6 --- SIBP Instrumental dispersion for band GBP,
SBP,i (SIBP)
211-221 F11.6 --- SRP0 Observed dispersion for band GRP,
SRP,0 (SRP0)
223-233 F11.6 --- SRP Astrohpysical dispersion for band GRP,
SRP (SRP)
235-243 F9.6 --- SSRP Astrophysical dispersion uncertainty
for band GRP, σSRP (SSRP)
245-253 F9.6 --- SIRP Instrumental dispersion for band GRP,
SRP,i (SIRP)
255-267 A13 --- Var Gaia DR3 photometric variability flag (VAR)
269 A1 --- EpPhot [T/F] Gaia DR3 has epoch photometry flag
(EPPHOT)
271-296 A26 --- VarClass Gaia DR3 variability class (VARCLASS)
298-300 A3 --- VarF [BNMV] Variability flag for G, GBP and GRP
bands (VARF) (2)
302-336 A35 --- SimId Simbad ID (on february 2023) (SIM_ID)
338-372 A35 --- SimSpType Simbad spectral type (on february 2023)
(SIM_SPTY)
374-386 A13 --- SimVar Simbad variability flag (on february 2023)
(SIM_VAR)
388-403 A16 --- SimPer Simbad period (on february 2023) (SIM_PER)
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Note (1): Photometric contamination parameter defined by Eqn. 6 of
Riello et al. (2021A&A...649A...3R 2021A&A...649A...3R) that measures the possible
discrepancy between G on the one hand and GBP and GRP on the other.
That parameter is expected to be close to zero for uncontaminated
stars without significant emission lines or anomalous extinction,
as the combination of temperature differences and normal extinction
defines a stellar locus in Gaia two-color diagrams that is nearly
one-dimensional (Figs. 10 and 11 in Maiz Apellaniz & Weiler.
2018A&A...619A.180M 2018A&A...619A.180M). Stars with C*≥0.1 (Fig. 18 in Riello et al.
2021A&A...649A...3R 2021A&A...649A...3R) are likely to be (partially) blended sources or
contaminated by nebulosity (Holl et al., 2023A&A...674A..25H 2023A&A...674A..25H).
Note (2): Variability flag as follows:
B = bad, assigned for the small number of cases where
SX,0 < SX,i - 3σSX,i
N = non-variable, assigned if SX < σSX
M = marginal, assigned if σSX ≤ SX < 3σSX
V = variable, assigned if SX ≥ 3σSX
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Acknowledgements:
Jesus Maiz Apellaniz, jmaiz(at)cab.inta-csic.es
(End) Patricia Vannier [CDS] 09-Aug-2023