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GCN Circular 28319

GRB 200826A
2020-08-30T07:28:22Z (4 years ago)
Barry Rothberg at Large Binocular Telescope Obs <>
B. Rothberg (LBTO/George Mason University), O. Kuhn (LBTO), C. Veillet
(LBTO), S. Allanson (LBTO).

We observed the optical afterglow of GRB 200826A  (Gupta et al. GCN Circ.
28288, Hurley et al., GCN Circ. 28291) using the Large Binocular Telescope
Observatory equipped with the Multi-Object Double Spectrographs (MODS).
Our spectra cover the wavelength range 0.38-1.0 microns. The observations
consist of 4 exposures of 900 seconds each in three of the four available
channels (MODS-1 Red, MODS-2 Blue, and MODS-2 Red).  The observation mid
time was 09:39 UT 28 Aug 2020.

In two 60 second acquisition images taken simultaneously wiith the g-sloan
and r-sloan filters we measure a magnitude of g=22.96 +/- 0.07 and r=22.15
+/- 0.07 (both ABmags). The photometry was calibrated against the DR12
catalog magnitudes of nearby stars (Alam et al. 2015, ApJS 219,12A). The
acquisition images were taken at 08:52:34 and 08:54:35 UT 28 Aug 2020.

The spectroscopic observations were taken at a Position Angle = 17 degrees
in order to cover both GRB 200826A and a possible nearby galaxy 15" NE. The
observations used a 1" wide slit and the spectra were extracted for both
sources using a 1" wide aperture. We clearly detect a continuum from
0.38-0.9 microns. From the detection of multiple emission features, which
we interpret as [OII], [NeIII], H-gamma, H-beta, [OIII]/4959, [OIII]/5007,
we calculate a redshift of 0.7481 +/-0.0003.

The nearby galaxy, 15" NE, is determined to be unrelated to GRB 200826A.
From the detection of multiple emission features which we interpret as
[OII]/5007, [NII]/6548, H-alpha, [NII]/6583, [SII]/6716, and [SII]/6730, we
infer a redshift of 0.1730 +/- 0.0003.

Additional spectroscopic observations are planned.

We acknowledge and heartily thank the rest of the LBTO staff for excellent
support in readying the telescope for nighttime on-sky activities during
these chaotic times.
B. Rothberg also acknowledges the assistance of R.T. Gatto.
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