J/ApJS/274/27 Robust statistics of var. for Gaia CRF3 sources (Makarov, 2024)
Optical variability of Gaia CRF3 sources with robust statistics and the 5000
most variable quasars.
Makarov V.V.
<Astrophys. J. Suppl. Ser., 274, 27 (2024)>
=2024ApJS..274...27M 2024ApJS..274...27M
ADC_Keywords: QSOs; Active gal. nuclei; Photometry; Optical; Colors
Keywords: Quasars ; Gaia ; Light curves ; Astrometry ; Blazars
Abstract:
Using the light-curve time-series data for more than 11.7 million
variable sources published in the Gaia Data Release 3, the average
magnitudes, colors, and variability parameters have been computed for
0.836 million Gaia CRF objects, which are mostly quasars and active
galactic nuclei (AGNs). To mitigate the effects of occasional flukes
in the data, robust statistical measures have been employed: namely,
the median, median absolute deviation, and Spearman correlation. We
find that the majority of the CRF sources have moderate amplitudes of
variability in the Gaia G band just below 0.1 mag. The heavy-tailed
distribution of variability amplitudes (quantified as robust standard
deviations) does not find a single analytical form, but is closer to
Maxwell distribution with a scale of 0.078 mag. The majority of CRF
sources have positive correlations between G magnitude and GBP-GRP
colors, meaning that these quasars and AGNs become bluer when they are
brighter. The variations in the GBP and GRP bands are also mostly
positively correlated. Dependencies of all variability parameters with
cosmological redshift are fairly flat for the more accurate estimates
above redshift 0.7, while the median color shows strong systematic
variations with redshift. Using a robust normalized score of magnitude
deviations, a sample of the 5000 most variable quasars is selected and
published. The intersection of this sample with the ICRF3 catalog
shows a much higher rate of strongly variable quasars (mostly blazars)
in ICRF3.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 112 5033 Robust variability parameters of 5033 most
variable Gaia Celestial Reference Frame (CRF)
quasars and AGNs
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See also:
I/323 : International Celestial Reference Frame 2, ICRF2 (Ma+, 2009)
I/325 : Radio-optical reference frame link (Zacharias+ 2013)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
I/358 : Gaia DR3 Part 4. Variability (Gaia Collaboration, 2022)
J/A+A/525/A37 : Var. indexes of QSOs in SDSS Stripe 82 (Meusinger+, 2011)
J/A+A/552/A98 : Optical monitoring of extragalactic sources (Taris+, 2013)
J/ApJS/224/19 : The KepVIM catalog (Makarov+, 2016)
J/A+A/587/A112 : Long term R and V band monitoring of AGN (Taris+, 2016)
J/ApJ/835/L30 : Dislodged AGNs (Makarov+, 2017)
J/ApJS/229/21 : VRI monitoring of the QSO 3C 273 in 2005-2016 (Xiong+, 2017)
J/ApJ/880/32 : Opt/γ-ray flares for Fermi blazars (Liodakis+, 2019)
J/ApJ/873/132 : ICRF3 radio-loud quasars with Gaia DR2 data (Makarov+, 2019)
J/A+A/644/A159 : The third realization of the ICRF, ICRF3 (Charlot+, 2020)
J/ApJ/888/73 : Varstrometry of SDSS QSOs with Gaia DR2 data (Hwang+, 2020)
J/AJ/162/21 : PS1 photometry of 2863 ICRF3 quasars (Berghea+, 2021)
J/A+A/651/A64 : Position difference vectors and of the jets (Lambert+, 2021)
J/A+A/649/A3 : Gaia EDR3 photometric passbands (Riello+, 2021)
J/ApJS/260/46 : Milky Way Mira variable stars from OGLE (Iwanek+, 2022)
J/MNRAS/510/1791 : Blazars study with ZTF DR6 and Roma-BZCAT (Negi+, 2022)
J/A+A/674/A41 : Composite quasar spectra from Gaia DR3 (Gaia Coll., 2023)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR3 Gaia DR3 source identifier
21- 33 F13.9 deg RAdeg Mean Right Ascension (ICRS) at Epoch=2016.0
(1)
35- 47 F13.9 deg DEdeg Mean Declination (ICRS) at Epoch=2016.0 (1)
49- 54 F6.3 mag GmagMed [13.48/20.2] Median G magnitude, Equation 1
56- 60 F5.3 mag GmagsMAD [0.029/1.6] Scaled median absolute deviation
in G, Equation 2
62- 68 F7.3 --- Zp [8.5/313] Analog to normalized variability
score, Equation 3 (2)
70- 72 I3 --- NepG [11/155] Number of single-epoch G band
measurements
74- 79 F6.3 mag BP-RPMed [0.07/5.4]?=-9 Median BP-RP color, Equation 1
81- 86 F6.3 mag BP-RPsMAD [0.01/2]?=-9 Scaled median absolute
deviation, BP-RP color
88- 93 F6.3 mag BPmagsMAD [0.006/1.7]?=-9 Scaled median absolute
deviation, BP magnitude
95- 100 F6.3 mag RPmagsMAD [0.01/1.8]?=-9 Scaled median absolute
deviation, RP magnitude
102- 106 F5.2 --- rho1 [-0.91/1]?=-9 Spearman's rank correlation,
(G,BP-RP)
108- 112 F5.2 --- rho2 [-0.12/1]?=-9 Spearman's rank correlation,
(BP,RP)
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Note (1): From the Gaia Celestial Reference Frame catalog (Cat. I/355;
see the gcrf3xm table).
Note (2): A robust analog of the normalized variability score, which is
computed as:
Zp=median(|Gmed-Gi|*fi/(1.086*ei)), i=1,...,nG
where fi is the tabulated measured flux in G, and ei is
its formal error; Gmed is the median G magnitude.
See Section 3.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 12-Feb-2025