TITLE:   GCN CIRCULAR
NUMBER:  26810
SUBJECT: LIGO/Virgo S200105ae: More candidates from the Zwicky Transient Facility
DATE:    20/01/18 03:33:23 GMT
FROM:    Tomas Ahumada at U. of Maryland  <tahumada@astro.umd.edu>

Tomas Ahumada (UMD), Igor Andreoni (Caltech), Viraj Karambelkar (Caltech),
Gaurav Waratkar (IITB), Harsh Kumar (IITB), Shreya Anand (Caltech), Michael
W. Coughlin (Caltech), Leo Singer (NASA GSFC), Mansi M. Kasliwal (Caltech),
Simeon Reusch (DESY), Robert Stein (DESY), Matthew Graham (Caltech), Jesper
Sollerman (OKC)
on behalf of the Zwicky Transient Facility (ZTF) and Global Relay of
Observatories Watching Transients Happen (GROWTH) collaborations

We serendipitously observed the localization region of the gravitational
wave trigger S200105ae (LVC, GCN #26640) 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) during the regular ZTF survey (i.e.,
without triggering further ToO observations in addition to those described
in Anand et al, GCN #26662). 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 Kowalski (Duev et al., 2019) and
AMPEL (Nordin et al., 2019), requiring 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 that no spatially coincident ZTF alert has been
issued before the detection time of S200105ae. New candidates were found
within the 95% probability contour of S200105ae, in addition to those
reported by Stein et al. (GCN #26673). The new transient candidates are
presented in the table below.

+--------------+-----------+-------------+--------------+--------+------+----------+-----------+
|     Name     |  IAU Name |      RA     |     Dec      | filter | mag  |
MJD    | Notes     |
+--------------+-----------+-------------+--------------+--------+------+----------+-----------+
| ZTF20aaexpwt | AT2020adi | 06:26:01.30 | +11:33:38.85 |   r    | 19.8 |
58864.31 | (a)(d)    |
| ZTF20aaertil | AT2020pu  | 14:52:25.86 | +31:01:18.50 |   g    | 19.7 |
58863.45 | (b)(c)(1) |
| ZTF20aaevbzl | AT2020adf | 13:26:41.27 | +30:52:30.68 |   g    | 20.3 |
58864.44 | (d)       |
| ZTF20aagiipi | AT2020adl | 15:33:24.61 | +42:02:36.70 |   r    | 20.1 |
58864.52 | (e)(2)    |
| ZTF20aagijez | AT2020adm | 15:04:13.18 | +27:29:04.19 |   r    | 19.9 |
58864.52 | (e)(3)    |
| ZTF20aagiiik | AT2020abl | 16:19:09.94 | +53:45:38.26 |   r    | 20.3 |
58864.52 | (e)(b)    |
| ZTF20aafexle | AT2020adn | 04:20:31.22 | -09:30:28.20 |   r    | 19.9 |
58862.19 | (e)       |
| ZTF20aaflndh | AT2020xz  | 01:22:38.14 | -06:49:34.31 |   g    | 19.2 |
58863.12 | (c)       |
| ZTF20aafduvt | AT2020ado | 03:36:28.54 | -07:49:34.52 |   g    | 20.1 |
58862.14 | (e)       |
| ZTF20aafefxe | AT2020adt | 07:47:24.18 | +14:42:23.82 |   r    | 20.9 |
58863.41 | (d)       |
| ZTF20aafkkoy | AT2020adp | 13:40:59.99 | +40:48:49.03 |   r    | 19.3 |
58862.4  | (d)       |
| ZTF20aafaoki | AT2020adq | 05:13:13.80 | +05:09:56.55 |   r    | 19.6 |
58861.19 | (d)       |
| ZTF20aafujqk | AT2020adg | 17:57:00.41 | +10:32:20.31 |   r    | 18.6 |
58863.57 | (e)       |
| ZTF20aafksha | AT2020adr | 13:43:54.45 | +38:25:13.82 |   g    | 20.0 |
58862.5  | (e)(4)    |
| ZTF20aagjemb | AT2020adh | 14:51:25.85 | +45:20:41.18 |   r    | 20.3 |
58864.48 | (c)(5)    |
| ZTF20aafdxkf | AT2020ads | 03:42:07.08 | -03:11:39.05 |   r    | 20.2 |
58862.2  | (d)       |
| ZTF20aafukgx | AT2020adj | 18:23:21.44 | +17:49:31.65 |   r    | 19.2 |
58863.58 | (a)(e)    |
| ZTF20aafanxk | AT2020adk | 05:35:36.04 | +11:46:15.31 |   r    | 19.4 |
58861.2  | (a)(e)    |
+--------------+-----------+-------------+--------------+--------+------+----------+-----------+
(a) Galactic latitude (|b_gal| < 15)
(b) first reported by ALeRCE
(c) close to the center of an apparently small galaxy
(d) hostless
(e) offset from the center of the possible host

(1) photoz = 0.0745 (SDSS)
(2) photoz = 0.127 (SDSS)
(3) specz = 0.061 (SDSS) - on a star-forming galaxy
(4) specz = 0.167 (SDSS)
(5) photoz = 0.299 (SDSS)


Additional comments:
ZTF20aafexle has red color g-r~0.5 mag
ZTF20aaevbzl is fading in g-band about ~0.15 mag per day.
ZTF20aafkkoy is a hostless transient rising in r-band.

Future observations are planned and 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 the generous support of the NSF under PIRE
Grant No 1545949. Alert distribution service provided by DIRAC@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 using the Kowalski infrastructure (Duev et al.,
2019) and with AMPEL (Nordin et al. 2019).