TITLE: GCN CIRCULAR NUMBER: 18811 SUBJECT: LIGO/Virgo G211117: Gemini classification of 7 Pan-STARRS transients DATE: 16/01/03 21:29:22 GMT FROM: S. J. Smartt at Queens U Belfast K. C. Chambers, (IfA, University of Hawaii), T.-W. Chen (MPE), S. Smartt K. Smith, D. Wright, (Queen’s University Belfast), M. E. Huber, A. S. B. Schultz (IfA), M. Coughlin (Harvard), L. Denneau, H. Flewelling, A. Heinze, R. Kotak (QUB), E. A. Magnier, N. Primak, A. Rest (STScI), A. Sherstyuk (IfA), B. Stalder (IfA), C. W. Stubbs (Harvard), J. Tonry, C. Waters (IfA), D. Young (QUB) Further to GCN 18786, we report spectroscopic classification of 7 of the Pan-STARRS transients within the northern localisation region of G211117. Spectra were taken with GMOS on the Gemini North 8m telescope (program GN-2015B-Q-4, PI. K. Chambers), with the R150 grating, filter GG455, and 1 arcsec slit giving useful wavelength coverage 5000-9600 Angs. Typical exposure times were 600s, and the spectra are of high quality (S/N 20-100). The data were taken on the nights of 2015-12-30 and 2015-12-31 (with the MJDs of the exposures given in parentheses below) PS15dpn (57387.23) Has a very blue continuum, with three weak (but real) emission line features. These are tentatively identified as He I 5015.68, 5875.60 and H-alpha at z=0.175, although this is by no means certain as two of them coincide with the strong telluric absorptions. The transient was discovered on our first scan of the region on 2015-12-28 and is still rising, slowly (0.6 mag in 4 days, now at i=19.9). This is an unusual spectrum and further multi-wavelength observations are encouraged. Further spectra are planned by our team. PS15dow (57387.21): type Ib (z=0.05 +/- 0.01) at +9 (SN1999ex) to +30d (SN2008D) after maximum light. Therefore, explosion at least 20-40d before the GW trigger PS15dpc (57387.26): type II z=0.056, +15-25d after explosion. Therefore explosion 10-29d before the GW trigger. PS15dpl (57387.40): type Ia (z=0.03 +0.05/-0.015), at -8 to -11d before peak. Assuming 17+/-1 days for rise time of type Ia SNe, this suggests explosion 2015-12-21 to 2015-12-26. Which brackets the GW detection, within the uncertainties. However as an apparently normal SN Ia, it would appear unrelated. PS15dot (57386.30) : type II at z=0.149 (host galaxy redshift). The epoch is uncertain, but likely to be 10 to 20days after explosion. This is a bright type II at M_i ~ -18.5, but likely to have exploded 10 days before the GW detection. PS15dov (57386.32) : type II in UGC2836 (z=0.016702 host redshift). Fairly old and reddened type II, with prominent P-Cygni lines of H-alpha and Ca II. Likely more than 50 days old. Only 4-5 arcsec separation from the recorded coordinates (NED and CBET) for SN203ih and SN2001I. Exploded long before the GW trigger. PS15dpb (57386.43) : type II in UGC2828 (z=0.041045 host redshift).Fairly old type II, around 20-30 days after explosion. Therefore, a likely explosion epoch around 15-25d before G211117.