SOAR optical spectroscopy of the Wolf-Rayet star WR96 during the dimming event
ATel #12511; S. K. Sarbadhicary, E. Aydi, J. Strader, L. Chomiuk, K. V. Sokolovsky, L. Shishkovsky, K. Dage, A. Kawash (MSU), T. Jayasinghe, K. Z. Stanek, C. S. Kochanek, P. Vallely, J. V. Shields, T. A. Thompson (OSU), B. J. Shappee (Univ. of Hawaii)
on 17 Feb 2019; 15:53 UT
Credential Certification: Elias Aydi (eaydi@saao.ac.za)
Subjects: Optical, Star, Variables
We report on optical spectroscopic observations of the Galactic Wolf-Rayet star WR96, which showed dramatic dimming as reported in ATels #12488 and #12492. We confirm that the dimming is caused by dust formation in the wind of the star and not by a failed supernova/direct collapse event. The latest ASAS-SN photometry shows that the brightness of WR96 is starting to recover.
We obtained a 300 s low-resolution spectrum of WR96 with the Goodman Spectrograph on the SOAR telescope on 2019-02-11.35 UT. The spectrum is dominated by emission lines of C, He, and O (see below for a full list of the line identification), with the strongest C lines having a FWHM of ~1400 +\-50 km/s. The C IV lines are weaker than the C III lines, consistent with a WC9 classification. The spectrum shows a red continuum and strong O III (5592 A) compared to the C IV and He II lines. This is unlike dust-free WC9 stars and may be indicative of dust formation (Williams et al. 2015 MNRAS, 449, 1834). We encourage further observations, particularly in the infra-red, and also making
comparisons with any previously unpublished data.
Emission line identifications:
C II: 6580, 6780, 8196, and 8337 A.
C III: 5134, 5253, 5274, 5696, 5811, 6740, 7037, 8500, and 8664 A.
C IV: 5020 and 5471 A.
O III: 5992 A.
He I: 5876, 6678 and 7065 A.
He II: 4895 and 5411 A.
Unidentified lines: 4942, 5305, 5340, 5653, 6100, 6150, 6208, 6260, 6460, 6871, 7115, 7725, and 7790 A.
