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GCN Circular 25215

Subject
LIGO/Virgo S190728q: Optical Counterpart Candidates from DECam-GROWTH
Date
2019-07-29T06:55:42Z (5 years ago)
From
Daniel Goldstein at Caltech <danny@caltech.edu>
Danny Goldstein (Caltech), Igor Andreoni (Caltech),  Mansi M. Kasliwal (Caltech), Shreya Anand (Caltech), Erik Kool (OKC), Sara Webb (Swinburne), Ashot Bagdasaryan (Caltech), Dmitry Duev (Caltech), Dougal Dobie (U Syd.)

On behalf of the Global Relay of Observatories Watching Transients Happen (GROWTH) collaboration

The DES-GW team conducted target-of-opportunity observations (NOAO PID 2019A-0235; PI Soares-Santos) of the localization region (GCN 25208; LALInference) of the gravitational wave trigger S190728q (GCN 25187) with the 4-m Victor M. Blanco telescope, equipped with the 3 square degree Dark Energy Camera.

The data were made immediately public. We downloaded the data in real-time and processed them through a custom pipeline designed to search for optical counterparts to gravitational wave events in DECam images (Goldstein, Andreoni et al. 2019; Andreoni, Goldstein et al. 2019), using reference images from the DECam Legacy Survey DR7 (Dey et al. 2019). We applied standard filtering criteria including rejecting stellar sources and moving objects and applying machine learning algorithms (Goldstein et al. 2015).

We report the discovery of the following objects, and to aid in prioritizing follow-up, we give the probability contour of the latest sky map (GCN 25208) that they lie within.

+---------------------------------------------------------------------------------------------+
|Internal Name | RA (deg)    | DEC (deg)   | Filter | Mag   |  Magerr | TNS Name  | Within    |
+--------------+-------------+-------------+--------+-------+---------+-----------+-----------+
|DG19rxclb     | 314.455468  | +9.251135   | r      | 21.5  |  0.35   | AT2019jvb | 50% reg.  |
|DG19blknb     | 318.492802  | +14.786966  | r      | 20.0  |  0.25   | AT2019lvt | 50% reg.  |
|DG19arsob     | 313.646387  | +7.566747   | r      | 22.0  |  0.25   | AT2019lvw | 50% reg.  |
|DG19tfmlb     | 315.728720  | +12.515448  | r      | 21.1  |  0.30   | AT2019lvv | 90% reg.  |
|DG19zrjmb     | 311.437716  | +7.919455   | r      | 20.6  |  0.30   | AT2019lvx | 90% reg.  |
|DG19jufnb     | 317.097475  | +14.326338  | r      | 20.6  |  0.20   | AT2019lvu | 50% reg.  |
|DG19bfhpb*    | 316.494483  | +9.978795   | r      | 21.0  |  0.30   | AT2019lvy | 90% reg.  |
+---------------------------------------------------------------------------------------------+

* Has previous detections in ZTF.

We will continue to report additional candidates via TNS and GCN. Additional analysis and continued follow-up is in progress and encouraged.

GROWTH is a worldwide collaboration 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; IIT-B, India; IIA, India; LJMU, UK; TTU, 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.
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