[vsnet-grb-info 24952] LIGO/Virgo S200213t: Candidates from the Zwicky Transient Facility

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27051
SUBJECT: LIGO/Virgo S200213t: Candidates from the Zwicky Transient Facility
DATE:    20/02/13 07:32:59 GMT
FROM:    Mansi M. Kasliwal at Caltech/Carnegie  <mansikasliwal at gmail.com>

Mansi M. Kasliwal (Caltech), Daniel Perley (LJMU), Harsh Kumar (IITB), Igor
Andreoni (Caltech), Kishalay De (Caltech), Viraj Karambelkar (Caltech),
Varun Bhalerao (IITB), Erik Kool (OKC), Jesper Sollerman (OKC), Ana
Carracedo (OKC), Michael Coughlin (U Minn), Eric Bellm (UW), Leo Singer
(NASA GSFC), Shreya Anand (Caltech), Tomas Ahmuda (UMd)

on behalf of the ZTF and GROWTH collaborations

We observed the localization region of the gravitational wave trigger
S200213t (LVC, GCN #27042) with the Palomar 48-inch telescope equipped with
the 47 square degree Zwicky Transient Facility camera (ZTF, Bellm et al.
2019, Graham et al. 2019).

The tiling was optimally determined and triggered using the GROWTH Target
of Opportunity marshal (Coughlin et al. 2019a, Kasliwal et al. 2019b). We
started obtaining target-of-opportunity observations in the g-band and
r-band beginning at 2020-02-13 04:36 UT, targeting ~77% of the enclosed
probability based on the bayestar skymap (LVC, GCN #27042). Each exposure
was 120s with a median depth of ~20.7 mag.

The images were processed in real-time through the ZTF reduction and image
subtraction pipelines at IPAC to search for potential counterparts (Masci
et al. 2019). Alert filtering and follow-up coordination was undertaken by
the GROWTH Marshal system (Kasliwal et al. 2019). The ZTF alert stream was
also queried using the Kowalski infrastructure (Duev et al., 2019). We
required at least 2 detections separated by at least 30 minutes to select
against moving objects. Furthermore, we cross-matched our candidates with
the Minor Planet Center to flag known asteroids. Candidates that passed our
selection are:

+--------------+----------+-------------+--------------+--------+------+----------+-------+
|     Name     | IAU Name |      RA     |     Dec      | filter | mag  |
MJD    | Notes |
+--------------+----------+-------------+--------------+--------+------+----------+-------+
| ZTF20aamvqxl |    AT2020ciy    | 01:56:57.10 | +53:40:07.97 |   r    |
20.1 | 58892.22 | Offset from Host Galaxy |
| ZTF20aamvnth |    AT2020cjb    | 01:13:21.05 | +49:38:43.94 |   g    |
20.4 | 58892.20 | Offset from Host Galaxy      |
| ZTF20aamvoxx |    AT2020cjg    | 02:37:35.78 | +26:55:14.22 |   g    |
20.0 | 58892.21 | SDSS phot-z 0.110 +/- 0.008      |
| ZTF20aamvtip |    AT2020cje    | 02:32:19.81 | +27:48:36.34 |   r    |
20.6 | 58892.24 | SDSS phot-z 0.22 +/- 0.06 |
| ZTF20aamvnat |    AT2020ciz    | 01:48:57.49 | +56:21:16.49 |   g    |
19.0 | 58892.21 | Faint Red Counterpart in PS1      |
| ZTF20aamvmzj |    AT2020cja    | 01:48:45.41 | +51:25:49.73 |   g    |
20.6 | 58892.20 | Hostless       |
| ZTF20aamvoeh |    AT2020cjc    | 02:14:00.48 | +38:56:10.74 |   g    |
20.6 | 58892.21 | Nuclear/Stellar?       |
| ZTF20aamvodd |    AT2020cjf    | 02:29:55.77 | +50:19:09.94 |   g    |
19.7 | 58892.20 | Faint Red Counterpart in PS1      |
+--------------+----------+-------------+--------------+--------+------+----------+-------+

We encourage follow-up to classify the candidates. We caution that these
candidates are low Galactic latitude and the magnitudes reported are not
extinction corrected.

ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC,
USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY,
Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan;
IITB, India; IIA, India; LJMU, UK; TTU, USA; SDSU, USA and USyd, Australia.
ZTF acknowledges the generous support of the NSF under AST MSIP Grant No
1440341. GROWTH acknowledges generous support of the NSF under PIRE Grant
No 1545949. Alert distribution service provided by DIRAC at UW (Patterson et
al. 2019). Alert filtering and follow-up coordination is being undertaken
by the GROWTH marshal system (Kasliwal et al. 2019). Alert database
searches are done with using the Kowalski infrastructure (Duev et al.,
2019) and with AMPEL (Nordin et al. 2019).