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SALT spectroscopy of the optical counterpart to GRB180728Aстатья
- Авторы: Buckley, Potter D.A.H.;, Lipunov S.B.;
- Журнал: The Astronomer’s Telegram
- Том: 11897
- Номер: 1
- Год издания: 2018
- Первая страница: 1
- Аннотация: We report on SALT spectroscopy of the optical counterpart to GRB180728A, which was discovered by the Neil Gehrels Swift Observatory (Starling et al., GCN#23046) and for which an optical transient was detected by the MASTER-SAAO transient detection facility (Lipunov et al., GCN#23048, GCN#23050) and spectra obtained by the ESO VLT UT2 using X-Shooter (Rossi et al., GCN#23055). A 1600 s exposure spectrum was obtained with the SALT Robert Stobie Spectrograph (RSS) on 2018 July 28 at 21:43:21 UT (mid exposure time) using the 300 l/mm grating covering 3900-9000Å at an average resolving power of R = 350. We attempted a spectroscopic classification with the SNID code (Blondin & Tonry 2007, ApJ, 666, 1024), with the best match being a SN Type Ic, five days before maximum, at a redshift of z=0.042, although the match is quite poor. While the major humps in the continuum occur close to their predicted wavelengths, there are significant flux residuals. We clearly detect both the rest frame interstellar Ca II 3933/3970Å and Na I 5890/5896Å doublets. Two absorption features seen at 4393 & 4434Å are identified as the Ca II doublet at a redshift of z = 0.117, consistent with the determination of Rossi et al.(GCN#23055). Simultaneous optical photometry with the SAAO 1-m telescope using the high-speed SHOC EM-CCD camera in white-light showed GRB180728A to only slowly fade over the period 00:46 to 02:47 UT, by approximately half a magnitude. SALT spectrum of GRB180728A on 2018 July 28 21:43:21 UT
- Добавил в систему: Липунов Владимир Михайлович