J/ApJ/918/63 Fast-transients confirmed by ZTFReST & LCs (Andreoni+, 2021)
Fast-transient searches in real time with ZTFReST: identification of three
optically discovered gamma-ray burst afterglows and new constraints on the
kilonova rate.
Andreoni I., Coughlin M.W., Kool E.C., Kasliwal M.M., Kumar H.,
Bhalerao V., Carracedo A.S., Ho A.Y.Q., Pang P.T.H., Saraogi D., Sharma K.,
Shenoy V., Burns E., Ahumada T., Anand S., Singer L.P., Perley D.A., De K.,
Fremling U.C., Bellm E.C., Bulla M., Crellin-quick A., Dietrich T.,
Drake A., Duev D.A., Goobar A., Graham M.J., Kaplan D.L., Kulkarni S.R.,
Laher R.R., Mahabal A.A., Shupe D.L., Sollerman J., Walters R., Yao Y.
<Astrophys. J., 918, 63-63 (2021)>
=2021ApJ...918...63A 2021ApJ...918...63A (SIMBAD/NED BibCode)
ADC_Keywords: Photometry; Optical; Redshifts; GRB; Novae; Transient
Keywords: Transient detection; Transient sources; Optical astronomy;
Gamma-ray bursts; Neutron stars
Abstract:
The most common way to discover extragalactic fast transients, which
fade within a few nights in the optical, is via follow-up of gamma-ray
burst and gravitational-wave triggers. However, wide-field surveys
have the potential to identify rapidly fading transients independently
of such external triggers. The volumetric survey speed of the Zwicky
Transient Facility (ZTF) makes it sensitive to objects as faint and
fast fading as kilonovae, the optical counterparts to binary neutron
star mergers, out to almost 200 Mpc. We introduce an open-source
software infrastructure, the ZTF REaltime Search and Triggering,
ZTFReST, designed to identify kilonovae and fast transients in ZTF
data. Using the ZTF alert stream combined with forced
point-spread-function photometry, we have implemented automated
candidate ranking based on their photometric evolution and fitting to
kilonova models. Automated triggering, with a human in the loop for
monitoring, of follow-up systems has also been implemented. In
13 months of science validation, we found several extragalactic fast
transients independently of any external trigger, including two
supernovae with post-shock cooling emission, two known afterglows with
an associated gamma-ray burst (ZTF20abbiixp, ZTF20abwysqy), two known
afterglows without any known gamma-ray counterpart (ZTF20aajnksq,
ZTF21aaeyldq), and three new fast-declining sources (ZTF20abtxwfx,
ZTF20acozryr, ZTF21aagwbjr) that are likely associated with
GRB200817A, GRB201103B, and GRB210204A. However, we have not found any
objects that appear to be kilonovae. We constrain the rate of
GW170817-like kilonovae to R<900Gpc-3/yr (95% confidence). A
framework such as ZTFReST could become a prime tool for kilonova and
fast-transient discovery with the Vera Rubin Observatory.
Description:
Since 2020 September 21, we have been running the Zwicky Transient
Facility REaltime Search and Triggering (ZTFReST) every day. We
validated the output of the pipeline by running it first on 265 days
of ZTF archival data, from 2020 January 1 to 2020 September 20, and
blindly scanning for candidates; from then on, new data was processed
daily. A summary of the confirmed extragalactic fast transients (along
with one yet unclassified source) identified during science validation
can be found in Table 1.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 100 13 Afterglows found with ZTFReST during science
validation
fig347.dat 58 239 Forced PSF photometry light curves of the 5 fast
transients (from Figures 3, 4 and 7)
--------------------------------------------------------------------------------
See also:
VII/281 : GLADE v2.3 catalog (Dalya+, 2018)
J/ApJ/746/156 : Radio afterglow observations of GRBs (Chandra+, 2012)
J/ApJS/200/8 : AGES: the AGN and Galaxy Evolution Survey (Kochanek+, 2012)
J/ApJ/806/52 : 8 Fermi GRB afterglows follow-up (Singer+, 2015)
J/ApJ/818/110 : Short GRBs with Fermi GBM and Swift BAT (Burns+, 2016)
J/ApJ/828/36 : GRB light-curve decay indices with Swift (Del Vecchio+, 2016)
J/A+A/593/A68 : PTF12os & iPTF13bvn spectra and light curves (Fremling+, 2016)
J/ApJ/848/L29 : Opt. follow-up of GW170817 counterpart (Diaz+, 2017)
J/ApJ/880/7 : The Local Universe survey. I. CLU-Halpha (Cook+, 2019)
J/ApJ/884/L55 : Opt. follow-up of gal. within S190814bv region (Gomez+, 2019)
J/A+A/631/A147 : Transient processing and analysis using AMPEL (Nordin+, 2019)
J/ApJ/886/152 : ZTF early observations of Type Ia SNe. I. LCs (Yao+, 2019)
J/A+A/643/A113 : iz photometry of S190814bv ctp candidates (Ackley+, 2020)
J/ApJ/890/131 : Follow-up of cand. counterparts of S190814bv (Andreoni+, 2020)
J/ApJ/904/155 : gri photometry for 32 kilonovae with ZTF (Andreoni+, 2020)
J/ApJ/905/58 : The local universe with ZTF. I. Transients (De+, 2020)
J/ApJ/895/32 : Zwicky Transient Facility BTS. I. (Fremling+, 2020)
J/ApJ/905/98 : Keck/LRIS optical spectrum of ZTF20aajnksq (Ho+, 2020)
J/ApJ/905/145 : ZTF cand. counterparts to 13 GW follow-up (Kasliwal+, 2020)
http://www.wis-tns.org/ : Transient Name Server home page
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- Name ZTF name of the source
14- 16 A3 --- f_Name Flag(s) on Name (1)
18- 27 A10 --- TNS Transient Name Server denomination
29- 30 I2 h RAh Hour of right ascension (J2000)
32- 33 I2 min RAm Minute of right ascension (J2000)
35- 39 F5.2 s RAs Second of right ascension (J2000)
41 A1 --- DE- Sign of declination (J2000)
42- 43 I2 deg DEd Degree of declination (J2000)
45- 46 I2 arcmin DEm Arcminute of declination (J2000)
48- 52 F5.2 arcsec DEs Arcsecond of declination (J2000)
54- 58 F5.1 deg GLAT [-41.5/71.9] Galactic latitude
60- 75 A16 --- Class Classification, or associated GRB when known
77- 81 F5.3 --- z [0.03/2.9]? Redshift
83- 84 A2 --- TW Discovery reference (This work)
86- 89 A4 --- Ref Other discovery reference(s) (2)
91- 94 F4.2 --- gFade [0.29/2.01]? Fade rate at the time of discovery
in the g band (3)
96-100 F5.2 --- rFade [0.28/17.56]? Fade rate at the time of
discovery in the r band (3)
--------------------------------------------------------------------------------
Note (1): Flag as follows:
a = archival searches (see Section 3.1)
r = real-time (see Section 3.2)
n = new, confirmed afterglow discovered by ZTFReST
Note (2): Reference as follows:
1 = Ho et al. (2020, J/ApJ/905/98);
2 = Ho et al. (2020GCN.27799....1H 2020GCN.27799....1H);
3 = Ahumada et al. (2020GCN.28295....1A 2020GCN.28295....1A)
4 = Andreoni et al. (2020ATel13978....1A 2020ATel13978....1A)
5 = Taguchi et al. (2020ATel14204....1T 2020ATel14204....1T)
6 = Coughlin et al. (2020GCN.28841....1C 2020GCN.28841....1C)
7 = U. C. Fremling et al. 2021, in preparation
8 = Milisavljevic et al. (2021ATel14320....1M 2021ATel14320....1M)
9 = Ho et al. (2021GCN.29305....1H 2021GCN.29305....1H)
10 = Kool et al. (2021GCN.29405....1K 2021GCN.29405....1K)
11 = Andreoni et al. (2021GCN.29446....1A 2021GCN.29446....1A)
12 = Andreoni et al. (2021TNSAN..89....1A 2021TNSAN..89....1A).
Note (3): In particular, the highest fade rates measured using ZTF alerts,
forced photometry, and nightly stacked forced photometry are reported.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: fig347.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- Name ZTF name of the source
14- 21 A8 --- Inst Instrument used (1)
23- 32 A10 "Y/M/D" Obs.date Observed UTC date, ISO 8601 (2)
34- 38 A5 "h:m" Obs.time Observed UTC time, ISO 8601 (2)
40- 44 F5.2 mag omag [17.16/23.95]? Observed AB magnitude in Filt
46- 50 F5.2 mag e_omag [0.03/0.4]? Uncertainty in omag
52- 56 F5.2 mag LimOmag [17.3/25.6]? Limiting magnitude, AB system
58 A1 --- Filt [griJ] Filter
--------------------------------------------------------------------------------
Note (1): Instrument as follows:
ZTF = the Zwicky Transient Facility (217 occurrences)
Sinistro = the LCO + 1m Sinistro imager; Programs NOAO2020B-005,
PI: Coughlin; TOM2020A-008, PI: Andreoni (11 occurrences)
GIT = the GROWTH-India Telescope (5 occurrences)
LRIS = the Low Resolution Imaging Spectrometer at W. M. Keck Observatory
(2 occurrences)
WaSP = the NIR with Palomar 200 inch (P200) equipped with the
Wafer-Scale Imager for Prime (PI: Kulkarni; 2 occurrences)
IO:O = the Liverpool Telescope (LT) with IO:O (1 occurrence;
see Section 4.2.)
WIRC = the NIR with Palomar 200 inch (P200) telescope equipped with
the Wide Field Infrared Camera (1 occurrence; see Section 4.1.1)
Note (2): For ZTF20acozryr (AT2020yxz), one measurement, acquired on
2020-11-13 07:25 UT, was removed because an obviously spurious excess
of flux was present at the transient location.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 13-Jan-2023