The H-alpha measurement of Swift J1626.6-5156 with the Southern African Large Telescope (SALT)

ATel #14489; Monageng I. M. (UCT/SAAO); Buckley D. A. H. (SAAO)
on 27 Mar 2021; 16:07 UT
Credential Certification: Itumeleng Monageng (itu@saao.ac.za)

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Observations performed with the MAXI/GSC nova alert system on 11 March 2021 revealed an X-ray enhancement at the location of the Be X-ray binary Swift J1626.6-5156 (ATel #14454). Follow-up observations performed with NICER (ATel #14457), SRG/ART-XC and NuSTAR (ATel #14462) confirmed the new outburst from Swift J1626.6-5156, its first after 15 years of quiescence. We obtained an optical spectrum of Swift J1626.6-5156 on 24 March 2021 at 23:46 UT using the Southern African Large Telescope (SALT) under the transients program (2018-2-LSP-001). A spectrum covering a wavelength range 6000 - 7250 Angstroms was obtained using the Robert Stobie Spectrograph (RSS) with the PG1800 grating (2.4 Angstroms resolution) at an exposure time of 600 seconds. The H-alpha line is seen in emission and shows a single-peaked profile. The measured FWHM of the H-alpha line is 8.58 ± 0.40 Angstroms and the EW is -38.1 ± 1.8 Angstroms, which is below the maximum ever reported value for the system (Reig et al. 2011), suggesting that the Be disc is still growing.