J/ApJ/859/8 SDSS J120414.37+351800.5 quasar optical photometry (Liu+, 2018)
A candidate tidal disruption event in a quasar at z=2.359 from abundance ratio
variability.
Liu X., Dittmann A., Shen Y., Jiang L.
<Astrophys. J., 859, 8 (2018)>
=2018ApJ...859....8L 2018ApJ...859....8L
ADC_Keywords: Photometry, SDSS; QSOs
Keywords: accretion, accretion disks; black hole physics; galaxies: abundances;
galaxies: active; galaxies: nuclei
Abstract:
A small fraction of quasars show an unusually high nitrogen-to-carbon
ratio (N/C) in their spectra. These "nitrogen-rich" (N-rich) quasars
are a long-standing puzzle because their interstellar medium implies
stellar populations with abnormally high metallicities. It has
recently been proposed that N-rich quasars may result from tidal
disruption events (TDEs) of stars by supermassive black holes. The
rapid enhancement of nitrogen and the depletion of carbon due to the
carbon-nitrogen-oxygen cycle in supersolar mass stars could naturally
produce high N/C. However, the TDE hypothesis predicts that the N/C
should change with time, which has never hitherto been observed. Here
we report the discovery of the first N-rich quasar with rapid N/C
variability that could be caused by a TDE. Two spectra separated by
1.7yrs (rest-frame) show that the NIII]λ1750/CIII]λ1909
intensity ratio decayed by ∼86%±14% (1σ). Optical (rest-frame
UV) light-curve and X-ray observations are qualitatively consistent
with the TDE hypothesis; though, the time baseline falls short of a
definitive proof. Putting the single-object discovery into context,
statistical analyses of the ∼80 known N-rich quasars with high-quality
archival spectra show evidence (at a 5σ significance level) of a
decrease in N/C on timescales of >1 year (rest-frame) and a constant
level of ionization (indicated by the CIII]λ1909/CIVλ1549
intensity ratio). If confirmed, our results demonstrate the method of
identifying TDE candidates in quasars via abundance ratio variability,
opening a new window of TDE observations at high redshift (z>2) with
upcoming large-scale time-domain spectroscopic surveys.
Description:
Figure 1 shows the two archival spectra of SDSS J120414.37+351800.5.
The SDSS spectrum was taken on 05-08-2005, whereas the BOSS spectrum
was taken on 03-01-2011, i.e., 1.7 years (in the quasar's rest frame)
after the SDSS spectrum.
The optical (rest-frame UV) light curves of SDSS J1204+3518 are
qualitatively consistent with the tidal disruption event (TDE)
hypothesis, although the baseline falls short of a proof. Figure 3
shows the heterogenous set of archival data spanning photometric
epochs from 2002 to 2013, encompassing the two spectroscopic epochs.
SDSS J1204+3518 has available light-curve data from the Catalina
Real-time Transient Survey (CRTS; Drake+ 2009, J/ApJ/696/870 ; V band),
the Palomar Transient Factory (PTF; Law+ 2009PASP..121.1395L 2009PASP..121.1395L ; R band),
and the SDSS (u, g, r, i, and z bands for only one epoch). We provide
all the available photometry data in the literature in Table 2.
Objects:
------------------------------------------------------------------------
RA (ICRS) DE Designation(s)
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12 04 14.37 +35 18 00.5 SDSS J1204+3518 = SDSS J120414.37+351800.5
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 92 397 Optical photometry from the literature
for SDSS J120414.37+351800.5
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See also:
IX/10 : ROSAT All-Sky Bright Source Catalogue (1RXS) (Voges+ 1999)
VIII/59 : the FIRST Survey, version 1999Jul (White+ 1999)
VII/252 : SDSS-DR5 quasar catalog (Schneider+, 2007)
VII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010)
J/ApJS/166/470 : SDSS-Spitzer type I QSOs IR photometry (Richards+, 2006)
J/ApJ/658/815 : Radio loudness of active galactic nuclei (Sikora+, 2007)
J/ApJ/685/773 : X-ray-UV relations in SDSS DR5 QSOs (Gibson+, 2008)
J/ApJ/679/962 : Quasars with strong nitrogen emission lines (Jiang+, 2008)
J/ApJ/696/870 : Catalina Real-time Transient Survey (CRTS) (Drake+, 2009)
J/ApJ/699/800 : Mass functions of active black holes (Vestergaard+, 2009)
J/ApJS/183/17 : The SDSS DR5/XMM-Newton quasar survey (Young+, 2009)
J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)
J/ApJ/753/125 : NIR spectroscopy follow-up of 60 SDSS-DR7 QSOs (Shen+, 2012)
J/ApJ/793/38 : Palomar Transient Factory phot. observations (Arcavi+, 2014)
J/MNRAS/463/3813 : ASASSN-15oi UBVI M2W1W2 light curves (Holoien+, 2016)
J/MNRAS/455/2918 : Phot. & line luminosities for ASASSN-14li (Holoien+, 2016)
J/ApJ/819/154 : SDSS-DR7 QSOs with X-ray and UV luminosities (Lusso+, 2016)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 8 F8.2 d MJD [53108.2/56449.3] Modified Julian Date
10- 14 F5.2 mag Vmag [18/19.5]?=-1 CRTS V-band Vega magnitude
16- 20 F5.2 mag e_Vmag [0.1/0.4]?=-1 The 1σ uncertainty in Vmag
22- 26 F5.2 mag Rmag [18.7/19.8]?=-1 PTF R-band Vega magnitude
28- 32 F5.2 mag e_Rmag [0.04/0.3]?=-1 The 1σ uncertainty in Rmag
34- 38 F5.2 mag umag [19.34]?=-1 SDSS u-band AB magnitude
40- 44 F5.2 mag e_umag [0.03]?=-1 The 1σ uncertainty in umag
46- 50 F5.2 mag gmag [18.84]?=-1 SDSS g-band AB magnitude
52- 56 F5.2 mag e_gmag [0.01]?=-1 The 1σ uncertainty in gmag
58- 62 F5.2 mag rmag [18.74]?=-1 SDSS r-band AB magnitude
64- 68 F5.2 mag e_rmag [0.01]?=-1 The 1σ uncertainty in rmag
70- 74 F5.2 mag imag [18.75]?=-1 SDSS i-band AB magnitude
76- 80 F5.2 mag e_imag [0.01]?=-1 The 1σ uncertainty in imag
82- 86 F5.2 mag zmag [18.48]?=-1 SDSS z-band AB magnitude
88- 92 F5.2 mag e_zmag [0.03]?=-1 The 1σ uncertainty in zmag
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 03-Apr-2019