GCN Circular 25494

Daniel A. Perley (LJMU), Yashvi Sharma (Caltech), Viraj Karambelkar 
(Caltech), Igor Andreoni (Caltech), and Mansi M. Kasliwal (Caltech) 
report on behalf of the GROWTH (Global Relay of Observatories Watching 
Transients Happen) collaboration

We obtained a spectrum of the host galaxy of the reported radio and 
optical transient AT2019osy
Not found
 
 
 (Stewart et al., GCN #25487; Andreoni et 
al., GCN #25488) using the Double Beam Spectrograph (Oke & Gunn 1982) on 
the Palomar 200-inch Hale Telescope. The spectrum was reduced using the 
pyraf-dbsp pipeline (Bellm & Sesar 2016).

The spectrum is dominated by red continuum that is likely primarily 
associated with the host galaxy; no obvious broad features are evident. 
We identify several narrow emission lines (H-alpha; [NII]6548,6583; 
[SII]6716,6731; possibly [OII]3727) at a common redshift of 0.0733, 
consistent within 2-sigma of the LVC distance constraint (LIGO/Virgo 
collaboration, GCN #25324).  H-beta and [OIII]5007 are not detected in 
the spectrum.

The flux ratio of the [NII] and H-alpha lines suggests AGN flux likely 
contributes to the emission lines, although this assessment is tentative 
since the line fluxes have not been corrected for any underlying stellar 
continuum features.  Further analysis is ongoing.

GROWTH is a worldwide collaboration comprising of 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; USyd, Australia; and SDSU, 
USA. GROWTH acknowledges generous support of the NSF under PIRE Grant No 
1545949.







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