TITLE:   GCN CIRCULAR
NUMBER:  20521
SUBJECT: LIGO/Virgo G270580: 10.4m GTC spectroscopic observations of PS17yt
DATE:    17/01/25 05:47:02 GMT
FROM:    Alberto J. Castro-Tirado at IAA-CSIC  <ajct@iaa.es>

A. J. Castro-Tirado, V. Casanova, B.-B. Zhang, J. C. Tello, Y. Hu 
(IAA-CSIC, Granada), M. D. Caballero-Garcia (ASU-CAS), V. V. Sokolov, V. 
V. Vlasjuk, A. F. Valeev (SAO-RAS), E. Pian (SNS-Pisa), S. Jeong (SKKU), 
S. R. Oates (Warwick), S. Geier and D. Pérez (GRANTECAN), report:

We observed the transient PS17yt (Chambers et al., LVC GCN 20512) with 
the 1.5m OSN telescope at Sierra Nevada (Spain) in imaging mode and with 
the 10.4m GTC telescope located at La Palma (Canary Islands, Spain) 
equipped with the OSIRIS spectrograph. The OSN images were gathered on 
Jan 24, 21:54 UT, whereas the spectroscopic observations were carried 
out starting on Jan 25, 00:50 UT. The PS17yt spectrum covering the range 
3700-10000 A shows that this transient is a type Ia SN about 1 week 
before maximum at a redshift z~0.026.

We acknowledge excellent support from the GTC staff.