TITLE:   GCN CIRCULAR
NUMBER:  29033
SUBJECT: GRB 201015A: optical observations and supernova identification
DATE:    20/12/12 23:11:17 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

A. Pozanenko (IKI), S. Belkin (IKI, HSE), A. Volnova (IKI), A. Moskvitin 
(SAO RAS), O. Burhonov (UBAI), V. Kim (FAI),  M. Krugov (FAI),  V. 
Rumyantsev (CrAO), E. Klunko (ISTP), R. Ya. Inasaridze (AbAO), I. Reva 
(FAI), P. Minaev (IKI), N. Pankov (HSE), Sh. Ehgamberdiev (UBAI) report 
on behalf of GRB IKI FuN:

We observed the GRB 201015A  (D'Elia et al., GCN 28632) with ZTSh 2.6m 
telescope of CrAO observatory, AZT-33IK of Mondy observatory, AZT-20 of 
Assy observatory, AS-32 of Abastumani observatory, Zeiss-1000 of SAO 
RAS, AZT-22 of Maidanak observatory, and Zeiss-1000(E) of TSHAO.

The optical transient of GRB 201015A (Lipunov et al., GCN 28633; Kennea 
et al., GCN 28635; Malesani et al., GCN 28637; Ackley et al., GCN 28639; 
Hu et al., GCN 28645; Zhu et al., GCN 28653; Belkin  et al., 28656; 
Marshall et al., GCN 28662; Jelinek et al., GCN 28664; Belkin et al., 
GCN 28673; Grossan et al., GCN 28674; Rastinejad et al., GCN 28676; Zhu 
et al., GCN 28677; Kumar et al., GCN 28680; Kumar et al., GCN 28681; 
Moskvitin et al., GCN 28721) at redshift z=0.426 (de Ugarte Postigo et 
al., GCN 28649; Izzo et al., GCN 28661) is not spatially resolved in 
most of our images besides a few imaging in Maidanak observatory between 
Oct. 26 - Nov. 6 when observations were carried out under good weather 
conditions (FWHM = 0.8 - 0.9 arcsec). The finding chart of stacked image 
obtained in Maidanak observatory on Oct. 26, Nov. 4 and Nov. 6  is 
presented in the left panel of the Figure 1.

http://grb.rssi.ru/GRB201015A/GRB201015A_SN_imaging.png

(In all of the stacked images in the Figure 1 we subtracted nearby stars 
which positions are designated by white and green circles. The white 
circles denote the stars presented in PS DR1 catalogue, and the green 
circle denote the star is not presented in PS DR1. Stacked images of 
Zeiss-1000 of SAO RAS observations on 32 days (central panel) and 47 
days (right panel) are also presented in the Figure 1.)

Using the stacked image of Maidanak observations (left panel of the 
Figure 1, an upper limit of the image is R=24.6)  we obtained photometry 
of the nearby stars. The photometry of the stars is used for flux 
subtraction to obtain R-magnitudes of unresolved optical transient in 
all of observations, and a light curve of the optical transient is 
presented in Figure 2

http://grb.rssi.ru/GRB201015A/GRB201015A_SN_LC.png

The light curve is preliminary and represent the joint photometry of the 
optical transient and a possible host galaxy.

The source raised on in the left panel of the Figure 1 (red circle) 
coincides with an afterglow coordinates of GRB 201015A reported by NOT 
observation (Malesani et al., GCN 28637). We suggest the object clearly 
visible on Oct.26 - Nov.6 at the place of the afterglow is a supernova 
associated with GRB 201015A. The light curve in the Figure 2 suggests 
the supernova maximum between 12 and 20 days after GRB trigger.  The 
supernova identification rules out the GRB 201015A as a questionable 
short burst with extended emission (Markwardt  et al., GCN 28658)   and 
corroborates the  GRB 201015A as a long duration burst (Minaev et al., 
GCN 28668). The afterglow in the first two days after the trigger can be 
approximated by a power law with the index of -0.91 ± 0.03.

We apologize for late report due to  delay of Maidanak data which is 
critical for supernova identification.