VCV10 and Quaia samples IR-selec var. QSOs J/A+A/699/A52 ivo://CDS.VizieR/J/A+A/699/A52 doi:10.26093/cds/vizier.36990052 CDS Zaharieva E.A. Ivanov V.D. Ovcharov E.P. Stanchev O.I. 2025-08-11T20:02:14Z 2025-06-27T08:16:09Z CDS support team CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France cds-question@unistra.fr surveys quasars infrared-photometry Quasars are variable and their variability can both constrain their physical properties and help to identify them. We aim to look for ways to efficiently identify quasars exhibiting consistent variability over multi-year time-scales, based on a small number of epochs. Using infrared (IR) is desirable to avoid bias against reddened objects. We compare the apparent brightness of known quasars that have been observed with two IR surveys, covering up to a twenty-year baseline: the Two Micron All Sky Survey (2MASS; 1997-2001) and the VISTA Hemisphere Survey (VHS; 2009-2017). We look at the previous studies of the selected variable quasars to see if their variable behaviour is known and when available we use multi-epoch monitoring with the Zwicky Transient Facility (ZTF) to obtain a measure of optical variability of individual objects. We build a sample of nearly 2500 quasars that show statistically significant variability between the 2MASS and VHS. About 1500 of these come from the new Quaia sample based on Gaia spectra and about 1/3 of these have hardly been studied. The Quaia sample constitutes the main product of this work. Based on ensemble variability and structure function analysis we demonstrate that the selected objects in our sample are representative of the typical quasar population and show behaviour, consistent with other quasar samples. Our analysis strengthens previous results, for example that variability decreases with the rest-frame wavelength and that it exhibits peaks for certain absolute magnitudes of the quasars. Similarly, the structure function shows an increase in variability for rest-frame time lags below ~1500d and a decrease for longer lags, just like in previous studies. Our selection, even though it is based on two epochs only, seems to be surprisingly robust, showing up to ~11% contamination by quasars that show stable non-variable behaviour in ZTF. 2025A&A...699A..52Z https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/699/A52 Catalog Research IsServedBy TAP VizieR generic service IsServedBy Conesearch service related-to VII/258 : Quasars and Active Galactic Nuclei (13th Ed.) (Veron-Cetty+ 2010) https://cds.unistra.fr/vizier-org/licences_vizier.html https://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/699/A52 https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/699/A52 http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/699/A52 https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/699/A52 https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/699/A52 http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/699/A52 GET text/xml+votable https://tapvizier.cds.unistra.fr/TAPVizieR/tap Cone search capability for table J/A+A/699/A52/table2 (Variable quasars from VCV10 sample) https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/699/A52/table2? https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/699/A52/table2? http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/699/A52/table2? GET text/xml+votable 180.0 50000 true 28.8754167 -8.9511111 0.005555555555555556 Cone search capability for table J/A+A/699/A52/table3 (Variable quasars from Quaia sample) https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/699/A52/table3? https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/699/A52/table3? http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/699/A52/table3? 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Variable quasars from VCV10 sample recno Record number assigned by the VizieR team. Should Not be used for identification. meta.record int RAJ2000 Right ascension (J2000) pos.eq.ra;meta.main DEJ2000 Declination (J2000) pos.eq.dec;meta.main 2MASS 2MASS source identifier (JHHMMSSss+DDMMSSs) meta.id;meta.main char J2MASS 2MASS J-band magnitude mag phot.mag;em.IR.J float e_J2MASS Error in 2MASS J-band magnitude mag stat.error float K2MASS 2MASS K-band magnitude mag phot.mag;em.IR.K float e_K2MASS Error in 2MASS K-band magnitude mag stat.error float JVHS VHS J-band magnitude mag phot.mag;em.IR.J float e_JVHS Error in VHS J-band magnitude mag stat.error float KVHS VHS K-band magnitude mag phot.mag;em.IR.K float e_KVHS Error in VHS K-band magnitude mag stat.error float SNRJ Signal-to-noise ratio for J-band variability stat.snr float SNRK Signal-to-noise ratio for K-band variability stat.snr float SNRJK Mean signal-to-noise ratio (J and K bands) stat.snr;stat.mean float
J/A+A/699/A52/table3 Variable quasars from Quaia sample recno Record number assigned by the VizieR team. Should Not be used for identification. meta.record int RAJ2000 Right ascension (J2000) pos.eq.ra;meta.main DEJ2000 Declination (J2000) pos.eq.dec;meta.main 2MASS 2MASS source identifier (JHHMMSSss+DDMMSSs) meta.id;meta.main char J2MASS 2MASS J-band magnitude mag phot.mag;em.IR.J float e_J2MASS Error in 2MASS J-band magnitude mag stat.error float K2MASS 2MASS K-band magnitude mag phot.mag;em.IR.K float e_K2MASS Error in 2MASS K-band magnitude mag stat.error float JVHS VHS J-band magnitude mag phot.mag;em.IR.J float e_JVHS Error in VHS J-band magnitude mag stat.error float KVHS VHS K-band magnitude mag phot.mag;em.IR.K float e_KVHS Error in VHS K-band magnitude mag stat.error float SNRJ Signal-to-noise ratio for J-band variability stat.snr float SNRK Signal-to-noise ratio for K-band variability stat.snr float SNRJK Mean signal-to-noise ratio (J and K bands) stat.snr;stat.mean float