WHT optical spectroscopy of Swift J1922.7-1716
ATel #3740; K. Wiersema (Leicester), A. Levan (Warwick), N. Tanvir (Leicester) and K. Tibbetts-Harlow (Leicester)
on 6 Nov 2011; 18:57 UT
Credential Certification: Klaas Wiersema (kw113@star.le.ac.uk)
Subjects: Optical, Binary, Transient
We observed the optical counterpart of Swift J1922.7-1716, motivated by the recent trigger of Swift BAT by this source (GCN circular 12522, Barthelmy et al. 2011), using the ISIS spectrograph on the 4.2m William Herschel Telescope (La Palma, Spain). We obtained 4 x 300 seconds exposures, starting at 19:55 UT on November 4th 2011. We used R300B and R158R grisms, in the blue and red arm of ISIS.
The source spectrum shows broad emission lines of hydrogen (Balmer lines) and He II, all at redshift 0. In addition, a strong Bowen blend emission feature is visible. These lines identify the source as a X-ray binary.
We thank the staff of the WHT, in particular Fiona Riddick and Ovidiu Vaduvescu, for obtaining these observation on a Service night.