J/MNRAS/463/296 PanSTARRS-1 slow-blue nuclear hypervariables (Lawrence+, 2016)
Slow-blue nuclear hypervariables in PanSTARRS-1.
Lawrence A., Bruce A.G., MacLeod C., Gezari S., Elvis M., Ward M.,
Smartt S.J., Smith K.W., Wright D., Fraser M., Marshall P., Kaiser N.,
Burgett W., Magnier E., Tonry J., Chambers K., Wainscoat R., Waters C.,
Price P., Metcalfe N., Valenti S., Kotak R., Mead A., Inserra C.,
Chen T.W., Soderberg A.
<Mon. Not. R. Astron. Soc., 463, 296-331 (2016)>
=2016MNRAS.463..296L 2016MNRAS.463..296L (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; QSOs ; Photometry, SDSS ; Equivalent widths
Keywords: accretion, accretion discs - gravitational lensing: micro -
galaxies: active - galaxies: nuclei - quasars: general
Abstract:
We discuss 76 large amplitude transients (Δm>1.5) occurring in
the nuclei of galaxies, nearly all with no previously known active
galactic nucleus (AGN). They have been discovered as part of the
Pan-STARRS1 (PS1) 3π survey, by comparison with Sloan Digital Sky
Survey (SDSS) photometry a decade earlier, and then monitored with the
Liverpool Telescope, and studied spectroscopically with the William
Herschel Telescope (WHT). Based on colours, light-curve shape, and
spectra, these transients fall into four groups. A few are
misclassified stars or objects of unknown type. Some are red/fast
transients and are known or likely nuclear supernovae. A few are
either radio sources or erratic variables and so likely blazars.
However the majority (∼66 per cent) are blue and evolve slowly, on a
time-scale of years. Spectroscopy shows them to be AGN at z ∼0.3-1.4,
which must have brightened since the SDSS photometry by around an
order of magnitude. It is likely that these objects were in fact AGN a
decade ago, but too weak to be recognized by SDSS; they could then be
classed as 'hypervariable' AGN. By searching the SDSS Stripe 82 quasar
database, we find 15 similar objects. We discuss several possible
explanations for these slow-blue hypervariables - (i) unusually
luminous tidal disruption events; (ii) extinction events; (iii)
changes in accretion state; and (iv) large amplitude microlensing by
stars in foreground galaxies. A mixture of explanations (iii) and (iv)
seems most likely. Both hold promise of considerable new insight into
the AGN phenomenon.
Description:
Our sample is based on Pan-STARRS1 and SDSS data, followed up with an
LT monitoring, and spectroscopy with the WHT. We begin by describing
each of these data sets, plus a small amount of additional data from
other sources.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 63 76 Basic sample properties
tablea2.dat 73 76 Cross-identifications for the sample
tablea3.dat 80 76 Host and transient photometry
tablea4.dat 107 76 Various quantities derived from the light
curves, spectra
tablea5.dat 89 37 Quantities measured from the WHT spectra
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See also:
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
II/314 : UKIDSS-DR8 LAS, GCS and DXS Surveys (Lawrence+ 2012)
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
J/ApJ/696/870 : Catalina Real-time Transient Survey (CRTS) (Drake+, 2009)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name Usual short name (G1)
9- 17 A9 --- Transient Transient ID
19- 20 I2 h RAh Right ascension (J2000.0)
22- 23 I2 min RAm Right ascension (J2000.0)
25- 29 F5.2 s RAs Right ascension (J2000.0)
31 A1 --- DE- Declination sign (J2000.0)
32- 33 I2 deg DEd Declination (J2000.0)
35- 36 I2 arcmin DEm Declination (J2000.0)
38- 41 F4.1 arcsec DEs Declination (J2000.0)
43- 52 A10 "date" FDate Date of flag
54- 63 A10 "date" WDate WHT Observation Date
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name Usual short name (G1)
9- 27 A19 --- SDSS SDSS ID (JHHMMSS.ss+DDMMSS.s)
29- 40 I12 --- UKIDSS ? UKIDSS ID (Lawrence et al.,
2007MNRAS.379.1599L 2007MNRAS.379.1599L, Cat. II/314)
41 A1 --- n_UKIDSS [oi] Note when no UKIDSS ID (1)
43- 49 I7 --- NVSS ? NVSS ID (Condon et al.,
1998AJ....115.1693C 1998AJ....115.1693C, Cat. VIII/65)
51- 73 A23 --- CRTS CRTS ID (Drake et al., 2009,
Cat. J/ApJ/696/870)
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Note (1): Note when no UKIDSS ID as follows:
o = object is outside the UKIDSS footprint
i = object is inside the UKIDSS footprint but not seen
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name Host galaxy name (G1)
9- 13 F5.2 mag gmag Host Galaxy g magnitude (1)
15- 18 F4.2 mag e_gmag rms uncertainty on gmag
20- 24 F5.2 mag u-g Host Galaxy u-g colour index (1)
26- 29 F4.2 mag e_u-g rms uncertainty on u-g
31- 35 F5.2 mag g-r Host Galaxy g-r colour index (1)
37- 40 F4.2 mag e_g-r rms uncertainty on g-r
42- 46 F5.2 mag r-i Host Galaxy r-i colour index (1)
48- 51 F4.2 mag e_r-i rms uncertainty on r-i
53- 57 F5.2 mag gmaxT Transient maximum g magnitude (2)
59 A1 --- l_u-gT Limit flag on u-gT
60- 64 F5.2 mag u-gT ?=- Transient u-g colour index (2)
66- 69 F4.2 mag e_u-gT ? rms uncertainty on u-gT
71- 75 F5.2 mag g-rT Transient g-r colour index (2)
77- 80 F4.2 mag e_g-rT rms uncertainty on g-rT
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Note (1): The host galaxy photometry uses the cmodel magnitudes from SDSS DR7.
Note (2): The transient magnitudes are 2 arcsec aperture photometry from the
Liverpool Telescope data.
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Byte-by-byte Description of file: tablea4.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name Usual short name (G1)
9 I1 --- ctype [1/3]? Colour type (1)
11- 14 F4.2 mag Ampg Transient amplitude in g band (2)
16- 19 F4.2 mag e_Ampg rms uncertainty on Ampg
21- 27 A7 --- SpType Spectral type
29- 34 F6.4 --- zsp ?=- Spectroscopic redshift
36- 40 F5.3 --- zph ? Photometric redshift, from SDSS DR7
42- 46 F5.3 --- e_zph ? rms uncertainty on sph
48- 54 F7.4 mag/month Slope Early decay rate
56- 61 F6.4 mag/month e_Slope rms uncertainty on Slope
63- 69 F7.4 --- SlopeAGN ? Slope in the AGN rest frame,
i.e. multiplied by 1=z
71-107 A37 --- Note Notes (3)
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Note (1): Colour type as follows:
1 = red
2 = blue
3 = ultra-blue
Note (2): SDSS magnitude minus PS1/LT magnitude at time of flag.
Note (3): DR7 and DR9 refer to SDSS releases. Objects are morphologically
classified as galaxy in both DR7 and DR9 except where noted.
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Byte-by-byte Description of file: tablea5.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name Usual short name (G1)
9- 15 F7.5 --- z Redshift
17- 22 F6.2 10-18W/m2 F(MgII) MgII flux
24- 27 F4.2 10-18W/m2 e_F(MgII) rms uncertainty on F(MgII)
29- 32 F4.2 10-18W/m2 F(MgIIc) Continuum MgII flux
34- 40 F7.3 0.1nm EW(MgII) AGN rest-frame MgII equivalent width
42 A1 --- l_F(OII) Limit flag on F(OII)
43- 47 F5.2 10-18W/m2 F(OII) ?=- OII flux
49- 53 F5.3 10-18W/m2 e_F(OII) ?=- rms uncertainty on F(OII)
55- 58 F4.2 10-18W/m2 F(OIIc) ?=- Continuum OII flux
60 A1 --- l_EW(OII) Limit flag on EW(OII)
61- 65 F5.3 0.1nm EW(OII) ?=- AGN rest-frame OII equivalent width
67 A1 --- l_F(OIII) Limit flag on F(OIII)
68- 72 F5.2 10-18W/m2 F(OIII) ?=- OIII flux
74- 77 F4.2 10-18W/m2 e_F(OIII) ?=- rms uncertainty on F(OIII)
79- 82 F4.2 10-18W/m2 F(OIIIc) ?=- Continuum OIII flux
84 A1 --- l_EW(OIII) Limit flag on EW(OIII)
85- 89 F5.2 0.1nm EW(OIII) ?=- AGN rest-frame OIII equivalent width
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Global notes:
Note (G1): Short version of the standard PS1 coordinate name,
used to cross-link tables
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 30-Apr-2018