J/MNRAS/481/307 Gaia Nuclear Transient (GNT) cand. (Kostrzewa-Rutkowska+, 2018)
Gaia transients in galactic nuclei.
Kostrzewa-Rutkowska Z., Jonker P.G., Hodgkin S.T., Wyrzykowski L.,
Fraser M., Harrison D.L., Rixon G., Yoldas A., Van Leeuwen F., Delgado A.,
Van Leeuwen M., Koposov S.E.
<Mon. Not. R. Astron. Soc., 481, 307-323 (2018)>
=2018MNRAS.481..307K 2018MNRAS.481..307K (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Active gal. nuclei ; Supernovae
Keywords: surveys - galaxies: nuclei - supernovae: general
Abstract:
The high spatial resolution and precise astrometry and photometry of
the Gaia mission should make it particularly apt at discovering and
resolving transients occurring in, or near, the centres of galaxies.
Indeed, some nuclear transients are reported by the Gaia Science
Alerts (GSA) team, but not a single confirmed tidal disruption event
(TDE) has been published. In order to explore the sensitivity of GSA,
we performed an independent and systematic search for nuclear
transients using Gaia observations. Our transient search is driven
from an input galaxy catalogue (derived from the Sloan Digital Sky
Survey Release 12). We present a candidate detection metric that is
independent from the existing GSA methodology, to see if Gaia Alerts
are biased against the discovery of nuclear transients, and in
particular which steps may have an impact. Our technique does require
significant manual vetting of candidates, making implementation in the
GSA system impractical for daily operations, although it could be run
weekly, which for month-to-year long transients would make a
scientifically valuable addition. Our search yielded 480 nuclear
transients, 5 of which were alerted and published by GSA. The list of
(in some cases ongoing) transients includes candidates for events
related to enhanced accretion on to a super-massive black hole and
TDEs. An implementation of the detection methodology and criteria used
in this paper as an extension of GSA could open up the possibility for
Gaia to fulfil the role as a main tool to find transient nuclear
activity as predicted in the literature.
Description:
The list of Gaia Nuclear Transient (GNT) candidates. The source list
provides the GNT source name, the SDSS galaxy ID, the coordinates RA
and Dec from Gaia in decimal degrees, the SDSS r-band brightness, the
Gaia G-band median brightness, the Gaia G-band peak brightness, the JD
at the time of the peak, the skewness parameter, the von Neumann
parameter (see the text on how these are calculated), and the SDSS
spectral classification with redshift (if available).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 144 482 List of GNT candidates
table3.dat 83 5 The GNT candidates previously alerted and
published by GSA pipeline
table4.dat 274 9 An overview of optical spectroscopy of the targets
and instrumental set-ups used to classify the
most recent nuclear transient candidates
table6.dat 48 15 The GNT candidates detected by GSA AlertPipe but
not published due to subsequent filtering
lc/* . 482 Individual light curves
sp/* . 23 Individual spectra
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- GNT GNT ID (GNTJHHMMSS.ss+DDMMSS.ss)
25- 48 A24 --- SDSS SDSS galaxy ID (SDSSJHHMMSS.ss+DDMMSS.ss)
50- 58 F9.5 deg RAdeg Right ascension (J2000)
60- 68 F9.5 deg DEdeg Declination (J2000)
70- 74 F5.2 mag rmag SDSS r-band brightness
76- 79 F4.2 mag e_rmag SDSS r-band brightness error
81- 85 F5.2 mag Gmag Gaia G-band median brightness
87- 90 F4.2 mag e_Gmag Gaia G-band median brightness error
92- 96 F5.2 mag Gmagp Gaia G-band peak brightness
98-101 F4.2 mag e_Gmagp Gaia G-band peak brightness error
103-109 F7.2 d JD JD at the time of the peak (JD-2456000)
111-115 F5.2 --- gamma Skewness parameter
117-120 F4.2 --- eta von Neumann parameter
122-128 A7 --- Class SDSS class
130-136 F7.5 --- z ?=9.99999 SDSS redshift
138-144 F7.5 --- e_z ?=9.99999 SDSS redshift error
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- GSA GSA ID (GaiaNNaaa)
11- 33 A23 --- GNT GNT ID (GNTJHHMMSS.ss+DDMMSS.ss)
35- 58 A24 --- SDSS SDSS galaxy ID (SDSSJHHMMSS.ss+DDMMSS.ss)
60- 70 A11 "date" ADate Alerting date by GSA
72- 82 A11 "date" JDpeak JD at the time of the peak
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- GNT GNT ID (GNTJHHMMSS.ss+DDMMSS.ss)
25- 35 A11 "date" Date Observation date
37- 40 A4 --- Inst Instrument (All spectra were taken with WHT)
42- 53 A12 --- Grating Grating
55- 57 F3.1 arcsec Slit Slit width
58 A1 --- --- [/]
59- 61 F3.1 arcsec Seeing1 Seeing, or lower value of Seeing interval
62 A1 --- --- [-]
63- 65 F3.1 arcsec Seeing2 ? Upper value of Seeing interval
67- 70 I4 0.1nm Range1 Lower value of wavelenght range
71 A1 --- --- [-]
72- 75 I4 0.1nm Range2 Upper value of wavelenght range
77- 80 I4 s Texp Exposure time
81 A1 --- --- [x]
82 I1 --- NExp Number of exposure
84-130 A47 --- FileName1 First spectrum file name in subdirectory sp
132-178 A47 --- FileName2 Second spectrum file name in subdirectory sp
180-226 A47 --- FileName3 Third spectrum file name in subdirectory sp
228-274 A47 --- FileName4 Fourth spectrum file name in subdirectory sp
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- GNT GNT ID (GNTJHHMMSS.ss+DDMMSS.ss)
25- 48 A24 --- SDSS SDSS galaxy ID (SDSSJHHMMSS.ss+DDMMSS.ss)
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Byte-by-byte Description of file (#): lc/*
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Bytes Format Units Label Explanations
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1- 7 F7.2 d JD Julian date (JD-2456000)
9- 13 F5.2 mag Gmag Gaia G magnitude
15- 18 F4.2 mag e_Gmag rms uncertainty on Gmag
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Byte-by-byte Description of file (#): sp/*
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Bytes Format Units Label Explanations
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1- 12 E12.7 0.1nm lambda Wavelength
13- 25 E13.7 10-2W/m2/nm sp Spectrum background fit, weights variance,
clean no (erg/cm2/s/Å)
26- 38 E13.7 10-2W/m2/nm raw Raw background fit, weights none, clean no
(erg/cm2/s/Å)
39- 51 E13.7 10-2W/m2/nm bkg Background background fit (erg/cm2/s/Å)
53- 64 E12.7 10-2W/m2/nm sigma Sigma background fit, weights variance,
clean no (erg/cm2/s/Å)
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Acknowledgements:
Zuzanna Kostrzewa-Rutkowska, z.p.kostrzewa(at)sron.nl
(End) Zuzanna Kostrzewa-Rutkowska [SRON, NL], Patricia Vannier [CDS] 14-Dec-2018