J/MNRAS/491/4925 Changing-state quasars with CRTS (Graham+, 2020)
Understanding extreme quasar optical variability with CRTS.
II. Changing-state quasars.
Graham M.J., Ross N.P., Stern D., Drake A.J., McKernan B., Ford K.E.S.,
Djorgovski S.G., Mahabal A.A., Glikman E., Larson S., Christensen E.
<Mon. Not. R. Astron. Soc., 491, 4925-4948 (2020)>
=2020MNRAS.491.4925G 2020MNRAS.491.4925G (SIMBAD/NED BibCode)
ADC_Keywords: Black holes ; QSOs ; Spectra, optical ; Photometry, infrared
Keywords: methods: data analysis - techniques: photometric - surveys -
quasars: general
Abstract:
We present the results of a systematic search for quasars in the
Catalina Real-time Transient Survey exhibiting both strong photometric
variability and spectroscopic variability over a decadal baseline. We
identify 111 sources with specific patterns of optical and
mid-infrared photometric behaviour and a defined spectroscopic change.
These 'changing-state' quasars (CSQs) form a higher luminosity sample
to complement existing sets of 'changing-look' AGNs and quasars in the
literature. The CSQs (by selection) exhibit larger photometric
variability than the changing-look quasars (CLQs). The spectroscopic
variability is marginally stronger in the CSQs than CLQs as defined by
the change in Hβ/[OIII] ratio. We find 48 sources with declining
Hβ flux and 63 sources with increasing Hβ flux, and discover
8 sources with z>0.8, further extending the redshift arm. Our CSQ
sample compares to the literature CLQ objects in similar distributions
of Hβ flux ratios and differential Eddington ratios between high
(bright) and low (dim) states. Taken as a whole, we find that this
population of extreme varying quasars is associated with changes in
the Eddington ratio and the time-scales imply cooling/heating fronts
propagating through the disc.
Description:
The Catalina Real-time Transient Survey (CRTS; Drake et al.
2009ApJ...696..870D 2009ApJ...696..870D, Cat. J/ApJ/696/870) represents the best data
currently available with which to systematically define sets of
quasars with particular temporal characteristics. The CRTS archive
(http://catalinadata.org) contains the Catalina Sky Survey data
streams from three telescopes - the 0.7m Catalina Sky Survey (CSS)
Schmidt and 1.5m Mount Lemmon Survey (MLS) telescopes in Arizona and
the 0.5m Siding Springs Survey (SSS) Schmidt in Australia.
We use MIR W1 (3.4µm) and W2 (4.6µm) WISE data from the
beginning of the mission in 2010 January through 2017 December,
corresponding to the fourth year of NEOWISE operations
(http://irsa.caltech.edu/wise).
The Million Quasars (MQ) catalogue (http://quasars.org/milliquas.htm)
v5.2 contains all spectroscopically confirmed type 1 QSOs, AGNs, and
BL Lacs in the literature up to 2017 August 5. We cross-matched MQ
against the CRTS data set with a 3" matching radius and find that
1411364 sources are covered by the full CRTS. We remove sources with
less than 10 observations and blazars, obtaining a sample of 1139438
sources.
After applying the optical variability constraints and the MIR
variability constraint described in Section 3, our sample is reduced
to 47451 sources. Of these 14412 have z<0.95 and multi-epoch SDSS
spectra with at least 100 (500)d between epochs are available for 466
(266) objects.
Finally, over the past 3yr, we have obtained second epoch spectra (all
at least >500d after the initial SDSS epoch) for an additional 426
candidates using either the Double Spectrograph (DBSP) on the Hale
200" telescope at Palomar Observatory, the Low Resolution Imaging
Spectrometer (LRIS) spectrograph, or the Echellette Spectrograph and
Imager (ESI), both on the Keck I telescope at the W. M. Keck
Observatory (see Table B1). Table 2 gives details of the 111 objects
for which the Hβ/[OIII] ratio changes by >30 per cent.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 73 111 CSQs selected in CRTS and associated features
tablea1.dat 76 61 CLQs reported in the literature with CRTS
coverage and associated features
tableb1.dat 93 111 Spectroscopic observations of CSQ candidates
--------------------------------------------------------------------------------
See also:
J/ApJ/696/870 : Catalina Real-time Transient Survey (CRTS)
V/154 : Sloan Digital Sky Surveys (SDSS), Release 16 (DR16)
(Ahumada+, 2020)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 A23 --- Name Quasar name (SDSS JHHMMSS.s+DDMMSS.s)
25- 29 F5.2 mag Vmagmed Median CRTS magnitude
31- 35 F5.3 --- z Redshift
37- 39 F3.1 [Msun] logMBH ? Logarithm of the quasar mass
41- 45 F5.2 [10-7W] logLV Logarithm of the quasar luminosity
47- 50 F4.2 mag Amp Optical amplitude
52- 57 F6.3 mag DBB Bayesian block change ΔBB
59- 62 F4.1 --- SWV1 Slepian wavelet variance measure
64- 67 F4.2 mag DW1 ? Absolute change in W1 |ΔW1|
69- 73 F5.2 --- D(Hb/[OIII]) Change in flux ratio of Hβ to [OIII]
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 22 A22 --- Name Quasar name (SDSS JHHMMSS.s+DDMMSS except
for WISE J105203.5+151929 and
WISEA J142846.7+172353)
24 A1 --- f_Name [*] Flag on Name (1)
26- 35 A10 --- Tran Transition (Disappear or Appear) (2)
37- 41 F5.2 mag Vmagmed Median CRTS magnitude
43- 47 F5.3 --- z Redshift
49- 51 F3.1 [Msun] logMBH ? Logarithm of the quasar mass
53- 56 F4.2 mag Amp Optical amplitude
58- 61 F4.2 mag DW1 Absolute change in W1 |ΔW1|
63- 67 F5.2 mag DBB Bayesian block change ΔBB
69- 73 F5.1 --- SWV1 Slepian wavelet variance measure
75- 76 I2 --- Ref References (3)
--------------------------------------------------------------------------------
Note (1): Flag as follows:
* = Source with multi-epoch spectra in the public domain
Note (2): Indicates the disappearce or appearance of the Hβ broad emission
line
Note (3): References as follows:
1 = MacLeod et al. (2016MNRAS.457..389M 2016MNRAS.457..389M)
2 = Ruan et al. (2016ApJ...826..188R 2016ApJ...826..188R)
3 = LaMassa et al. (2015ApJ...800..144L 2015ApJ...800..144L)
4 = Runnoe et al. (2016MNRAS.455.1691R 2016MNRAS.455.1691R)
5 = Gezari et al. (2017ApJ...835..144G 2017ApJ...835..144G)
6 = Yang et al. (2018ApJ...862..109Y 2018ApJ...862..109Y)
7 = Runco et al. (2016ApJ...821...33R 2016ApJ...821...33R, Cat. J/ApJ/821/33)
8 = Assef et al. (2018ApJS..234...23A 2018ApJS..234...23A, Cat. J/ApJS/234/23)
9 = Stern et al. (2018ApJ...864...27S 2018ApJ...864...27S)
10 = Wang, Xu & Wei (2018ApJ...852...26W 2018ApJ...852...26W)
11 = Ross et al. (2018MNRAS.480.4468R 2018MNRAS.480.4468R)
12 = MacLeod et al. (2019ApJ...874....8M 2019ApJ...874....8M, Cat. J/ApJ/874/8)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tableb1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 A23 --- Name Quasar name (SDSS JHHMMSS.s+DDMMSS.s)
25- 31 A7 d MJD1 First epoch spectra from SDSS
33- 93 A61 d MJDsub Subsequent epoch spectra from SDSS, Palomar
(DBSP), and Keck (LRIS, ESI)
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
Graham et al., Paper I 2017MNRAS.470.4112G 2017MNRAS.470.4112G
(End) Ana Fiallos [CDS] 22-Feb-2023