A. S. Moskvitin, D. I. Makarov, A. F. Valeev, V. V. Sokolov (SAO-RAS,
Russia), A. J. Castro-Tirado, J. Gorosabel (IAA-CSIC, Spain),
E. S. Gorbovskoy, D. V. Denisenko, V. M.Lipunov (MASTER-team, Russia),
on behalf of a larger collaboration, report:
"Following the detection of GRB 140508A by Fermi (Yu et al. GCNC 16224) and
the IPN (Hurley et al. GCNC 16225), we have conducted BVRc imaging and
spectroscopy of the iPTF optical candidate (Singer et al. GCNC 16226) with
the 6m BTA telescope in Zelenchukskaia, starting at 19:47:56 UT (i.e. 16.7
hr after the trigger). The 20 minutes (noisy) spectrum, covering the range
3800-7200 A, displays no clear absorption features, i.e. a conservative
upper limit of z < 2.1 is derived.
The GRB OT magnitude was measured to have R = 18.7 +/- 0.05 during the BTA
observations spanning more than 1 hr. OT magnitudes calibrated against the
USNO-B1 star 1367-0290781 with R2 = 16.48.
MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru)
located in Kislovodsk also pointed to the GRB140508A (Yu et. al GCNC
16224, Hurley et. al. GCN 16224) ~17.5 h after trigger time at 2014-05-08
20:31:01.484 UT directly after sunset and weather conditions became
satisfactory. On the first (180s exposure) unfiltred image the iPTF
optical transient preliminary photometry is given below:
T_start T-T_trig FILTER Mag Err.Mag Exptime
2014-05-08 20:31:01 17h 28m C 18.7 0.3 180 s
2014-05-08 20:48:33 17h 45m R 18.7 0.3 180 s
2014-05-08 20:48:33 17h 45m V <19.0 0.3 180 s upper limit
2014-05-08 21:20:36 18h 17m R 18.9 0.3 540 s
2014-05-08 21:20:36 18h 17m V 19.9 0.4 540 s
"C" is unfiltred 0.8R+0.2B magnitude.
This message can be quoted."