[vsnet-grb-info 22412] LIGO/Virgo S190510g: Spectroscopic Classification of DECam-GROWTH and DES-GW Candidate DG19fqqk/desgw-190510c with Magellan

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  24511
SUBJECT: LIGO/Virgo S190510g: Spectroscopic Classification of DECam-GROWTH and DES-GW Candidate DG19fqqk/desgw-190510c with Magellan 
DATE:    19/05/12 21:49:07 GMT
FROM:    Sebastian Gomez at Harvard U  <sgomez at cfa.harvard.edu>

S. Gomez (Harvard), P. S. Cowperthwaite (Carnegie), G. Hosseinzadeh (Harvard), E. Berger (Harvard), P. K. Blanchard (Harvard), M. R. Drout (Carnegie/U. Toronto), T. Eftekhari (Harvard), M. Nicholl (Edinburgh), L. Patton (Harvard), A. L. Piro (Carnegie), V. A. Villar (Harvard), P.K.G. Williams (Harvard), P. Goudfrooij (STScI), and T. Puzia (PUC, Chile)


We report on spectroscopic observations conducted with the IMACS Spectrograph on the 6.5m Magellan-Baade telescope of a candidate optical counterpart to the gravitational wave event S190510g (The LIGO Scientific Collaboration and the Virgo Collaboration, GCN 24442). The counterpart was identified during difference image processing of public DECam observations (Andreoni et al. GCN 24443, Andreoni et al. GCN 24467, Soares-Santos et al. GCN 24480).

Lists of promising counterparts were identified on the basis of factors such as their brightness, colors, and possible host galaxy association. We were able to obtain deep spectroscopy of DG19fqqk/desgw-190510c, which is an interesting source as it was flagged by a light curve classifier trained to identify kilonovae (KN-Classify, GCN 24480).

Target                                   | Reference                         | Classification                     
----------------------------------------------------------------------------------------------------------------
DG19fqqk/desgw-190510c  | GCN 24467, GCN 24480  | Type II (phase = +6 days)

DG19fqqk/desgw-190510c shows a broad feature consistent with H-alpha at a redshift of 0.06 and template matching using Superfit (Howell et al. 2005, ApJ, 634, 1190) suggests a good match to a Type II SNe approximately one week after peak brightness. This candidate was also observed by KMTNet (GCN #24493) and showed no significant fading over ~1 day.

We conclude that the transient is not associated with the gravitational wave event S190510g.

We thank Paul Goudfrooij and Thomas Puzia for taking these observations.