GCN Circular 23113

N.Tiurina, V. Lipunov, E. Gorbovskoy,
V.Kornilov, A.Kuznetsov, V.Chazov, I.  Gorbunov,
D.Zimnukhov, D.Kuvshinov, P.Balanutsa, V.Vladimirov, D. Vlasenko
Lomonosov Moscow State University,SAI

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias (IAC)

D. Buckley,
South African Astronomical Observatory (SAAO)

A. Tlatov, V.Senik, D. Dormidontov
Kislovodsk Solar Station of the Pulkovo Observatory

R. Podesta, F. Podesta, C. Lopez, C.Francile
Observatorio Astronomico Felix Aguilar (OAFA)

H.Levato,
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

O. Gres, N.M.Budnev , Yu.Ishmuhametova
Irkutsk State University (ISU)

A. Gabovich, V. Yurkov, Yu. Sergienko
Blagoveschensk Educational State University (BSPU)


We have already reported the observation of the optical transient GRB 
180809B (Moss et al., GCN # 23105) by one of the telescopes of the MASTER 
Global Network (Lipunov et al., GCN 23109
Not found
 
 
).

Here we report on the triple independent, automatic detection of the 
optical transient (also found by Swift UVOT (Moss et al., GCN 23105
Not found
 
 
)). The 
relatively later guidance of the three MASTER robotic telescopes is due to 
the fact that the first socket message did not indicate the time of the 
trigger. As a result, everyone went to the CALET Alert (trig 
number 1217881726) with poor defined coordinates. 
Nevertheless, we were able to obtain detailed light curves 
with a maximum in 4 polarizations.


MASTER-SAAO robotic telescope (MASTER-Net: http://observ.pereplet.ru, 
Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in 
South Africa (South African Astronomical Observatory) was pointed to the 
GRB180809.85 16 sec after notice time and 111 sec after trigger time at 
2018-08-09 20:30:39 UT. On our 1-th (10s exposure)  set in two 
polarizations (/\), obtained 111 
sec after tigger time at 2018-08-09 20:30:39 UT, we  found 1 optical transient 
within SWIFT error-box (ra=299.7 dec=-15.2989 r=0.05) brighter then 17.4.


  T-Tmid      Date   Time       Expt.        Ra                Dec        Mag
    s                 UT         s
-------|--------------------|-------|-----------------|---------------|-------
   116    2018-08-09 20:30:39    10    (19h 58m 48.0s , -15d 17m 57.1s)   16.5

The 5-sigma upper limit has been about 17.9 mag


The observations started on zenit distance = 21 deg., galactic latitude b 
= -22 deg. The moon ( 4 % bright part) was below the horizon (The altitude 
of the  Moon = -75 deg ). The sun  altitude  = -56.3 degree. The object 
can be observed till 2018-08-10 04:03:58 UT.


MASTER-Tavrida robotic telescope (MASTER-Net: http://observ.pereplet.ru, 
Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in 
Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the 
GRB180809.85 35 sec after notice time and 133 sec after trigger time at 
2018-08-09 20:31:01 UT. On our first (10s 
exposure)  set we  found 1 optical transient within SWIFT error-box
(ra=299.7 dec=-15.2989 r=0.05) brighter then 17.9:


T-Tmid   Date      Time       Expt.        Ra                Dec           Mag
   s                UT         s
------|--------------------|-------|-----------------|-----------------|-------
  138    2018-08-09 20:31:01    10    ( 19h 58m 48.0s , -15d 17m 56.5s)    16.8

The 5-sigma upper limit has been about 17.9 mag


The observations made on zenit distance = 60 degrees, galaxy latitude b = -22 degree.
The moon ( 4 % bright part) below the horizon (The altitude of the Moon is 
-25 degree ). The sun  altitude  is -27.0 degree.
The object can be observed till 2018-08-10 01:29:20.


MASTER-IAC robotic telescope (MASTER-Net: http://observ.pereplet.ru, 
Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in 
Spain (IAC Teide Observatory) was pointed to the  GRB180809.85 120 sec 
after notice time and 147 sec after trigger time at 2018-08-09 20:31:15 
UT in two polarizations (|-). 
On our first  set, obtained   we  found 1 optical transient within SWIFT 
error-box (ra=299.7 dec=-15.2989 r=0.05):


  T-Tmid      Date      Time       Expt.        Ra                Dec           Mag
---------|---------------------|-------|-----------------|-----------------|-------
   152      2018-08-10 20 31 15     20   ( 19h 58m 43.3s , -15d 20m 37.9s)     15.5

The 5-sigma upper limit has been about 16.0 magThe message may be cited.

The observations made on zenit distance = 44 degrees, galaxy latitude b = 
-22 degree. The moon ( 3 % bright part) below the horizon (The altitude of 
the Moon is  -41 degree ). The sun  altitude  is  -9.1 deg.
The object can be observed till 2018-08-10 05:19:05 UT.


The message may be cited.