[vsnet-grb-info 24642] LIGO/Virgo S200114f: Candidates from the Zwicky Transient Facility

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  26741
SUBJECT: LIGO/Virgo S200114f: Candidates from the Zwicky Transient Facility
DATE:    20/01/14 07:26:29 GMT
FROM:    Igor Andreoni at Caltech  <igor.andreoni at gmail.com>

Igor Andreoni (Caltech), Harsh Kumar (IITB), Michael W. Coughlin (Caltech), Tomas Ahumada (UMD), Shreya Anand (Caltech), Leo Singer (NASA/GSFC), Mansi M. Kasliwal (Caltech), Varun Bhalerao (IITB), Kishalay De (Caltech), Danny Goldstein (Caltech), Ariel Goobar (OKC), Matthew Graham (Caltech), Erik Kool (OKC), Jesper Sollerman (OKC), Dmitry Duev (Caltech), Brad Cenko (NASA GSFC)
on behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations

We observed the localization region of the unmodeled gravitational wave trigger S200114f (LVC, GCN #26734) 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 2020-01-14 03:39 UT, covering 77.7% of the integrated probability based on the cWB skymap (LVC, GCN #26734). Each exposure was 300s, reaching a g-band median depth of 21.9 mag and r-band median depth of 21.6 mag. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC (Masci et al. 2019).

We queried the ZTF alert stream using the Kowalski infrastructure (Duev et al., 2019). We required at least 2 detections separated by at least 15 minutes to select against moving objects. Furthermore, we cross-matched our candidates with the Minor Planet Center to flag known asteroids. We require no spatially coincident ZTF alert to be issued before the detection time of S200114f. The candidates within the 95% probability contour of S200114f that passed the automatic selection criteria and human vetting are presented in the table below.

+--------------+----------+-------------+--------------+--------+------+----------+-------+-------+
|     Name     | IAU Name |      RA     |     Dec      | filter | mag  |   MJD    | b_Gal | Notes |
+--------------+----------+-------------+--------------+--------+------+----------+-------+-------+
| ZTF20aafdytz | AT2020vr | 07:34:06.13 | +16:46:00.51 |   g    | 20.9 | 58862.15 | 16.8  | (a)   |
| ZTF20aafdzkn | AT2020vs | 07:24:28.50 | +16:12:45.85 |   g    | 21.4 | 58862.15 | 14.4  |       |
| ZTF20aafeoka | AT2020vu | 07:16:47.14 | +10:37:18.97 |   g    | 21.6 | 58862.15 | 10.4  |       |
| ZTF20aafeadg | AT2020vw | 07:05:49.02 | +13:52:13.91 |   g    | 21.2 | 58862.15 | 9.4   | (b)   |
| ZTF20aafdyru | AT2020vg | 07:10:12.71 | +16:06:25.50 |   g    | 21.6 | 58862.15 | 11.3  | (c)   |
| ZTF20aafeaqk | AT2020vx | 07:08:43.68 | +14:38:15.44 |   g    | 21.2 | 58862.15 | 10.3  | (c)   |
| ZTF20aafemum | AT2020vt | 07:30:09.34 | +19:51:37.81 |   g    | 21.6 | 58862.15 | 17.1  | (d)   |
| ZTF20aafeewx | AT2020vy | 07:35:17.49 | +10:04:45.13 |   g    | 21.2 | 58862.16 | 14.2  |       |
| ZTF20aafegdf | AT2020vz | 07:34:32.29 | +08:47:16.85 |   g    | 21.0 | 58862.16 | 13.5  | (b)   |
| ZTF20aafedbk | AT2020wa | 07:08:38.13 | +27:51:17.40 |   g    | 21.2 | 58862.16 | 15.7  | (b)   |
| ZTF20aafeccu | AT2020wc | 07:03:22.07 | +27:22:41.21 |   g    | 20.7 | 58862.16 | 14.5  | (d)   |
+--------------+----------+-------------+--------------+--------+------+----------+-------+-------+

(a) SDSS photoz = 0.193 +- 0.0502
(b) offset from possible host galaxy
(c) possible AGN based on WISE colors 
(d) possible host in Legacy Survey

We caution that the age of these candidates is not well constrained as our triggered ToO observations are deeper than the regular survey. We encourage follow-up.


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).