GCN Circular 24850
V. Cunningham (U of Maryland), J. D. Neill (Caltech), S. B. Cenko (NASA GSFC), and R. Walters (Caltech) report on behalf of the SEDM team: We observed the optical counterpart to GRB 190613A (Ambrosi et al., GCN 24798) with the Spectral Energy Distribution Machine (SEDM) on the 60 inch telescope at Palomar Observatory. The SEDM is a low resolution (R ~ 100) integral field unit spectrometer with a multi-band (ugri) rainbow camera imager (see Blagorodnova et al. 2018, PASP, 130, 035003, and Rigault et al. 2019, astro-ph/1902.08526). The SEDM began observing the optical counterpart at 04:18:22 UTC (8.75 minutes after the burst trigger time). We performed an 1800 s exposure over the wavelength range 3800-9200 A. The continuum emission is well-fit by a power law spectrum with index alpha = 0.56 (f_nu ~ nu^-alpha). We detect an absorption line at an observed wavelength of ~ 4597 A. We tentatively identify this line as due to Lyman alpha at z = 2.78 - however due to the lack of corroborating features we consider this redshift tentative currently.