TITLE: GCN CIRCULAR NUMBER: 25494 SUBJECT: LIGO/Virgo S190814bv: Palomar 200-in spectroscopic redshift and host galaxy properties of ASKAP source AT2019osy DATE: 19/08/27 20:05:29 GMT FROM: Daniel Perley at Liverpool JMU 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 (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. DisclaimerNone