GCN Circular 23023

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

D. Buckley,
South African Astronomical Observatory (SAAO)

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

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)

MASTER-Amur robotic telescope (MASTER-Net: http://observ.pereplet.ru, 
Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in 
Russia (Blagoveschensk State Pedagogical University) was pointed to the 
Swift GRB180720B (Siegel et al., GCN Circ #22973) 113 sec after trigger 
time at 2018-07-20 14:23:37 UT.
So as the GRB was 4.6 degrees above the horizont, the good observations 
started on 2018-07-20 15:21:50UT.

Galaxy latitude b = -63.07 degree.
The moon (58 % bright part) is 9 degrees above the horizon. The distance 
between  moon and  object was 143.
The sun  altitude  was -17.19 degree.
The object observed till 2018-07-20 15:47:58

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 
GRB180720B 27260 sec after trigger time at 2018-07-19 20:56:09 UT as 
MASTER's LAT (Bissaldi et al GCN22980
Not found
 
 
)alert inspection with polarization 
filters.

MASTER-SAAO auto-detection system ( Lipunov et al., "MASTER Global Robotic 
Net", Advances in Astronomy, 2010, 30L )
  discovered bright OT source at (RA, Dec) = 00h 02m 06.92s -02d 55m 05.6s 
on  2018-07-19 20:56:09  UT.

The OT  magnitude is ~16.8m .

There is no minor planet at this place.
We have reference image on 2016-05-04.12293 UT with  unfiltered mlim =  18.1m.


The observations made on zenit distance = 16.7 degrees, galaxy latitude b 
= -74.37 degree. The moon (61 % bright part) was 24 degrees above the 
horizon.The sun  altitude  was -63.7 degree.

MASTER-SAAO reobserved this area on 2018-07-21 22:28:10-22:54:51UT as 
MASTER's MAXI (Negoro et al GCN 22993
Not found
 
 
)  alert inspection  with mlim=20.2 
and unfiltered m_OT~19.1

The discovery and reference images are 
http://master.sai.msu.ru/static/OT/MASTERGRB180720B.jpg


MASTER-Kislovodsk robotic telescope (MASTER-Net: 
http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, 
vol. 2010, 30L) located in Russia (Pulkovo Solar Station) was pointed to 
the GRB180720B (Siegel et al., GCN Circ #22973) 27457 sec after trigger 
time at 2018-07-20 21:59:21 UT .
On our first (180s exposure)  set MASTER-Kislovodsk auto-detection system 
discovered OT with m_OT~17.0,  automatical  mlim~17.6.

The observations made on zenit distance = 25.66 degrees, galaxy latitude b 
= -63.07 degree.
The moon (61 % bright part) is below the horizon(The altitude of Moon is 
-8). The distance between  moon and  object is 138
The sun  altitude  is -24.87 degree.
The object observed till 2018-07-20 22:19:52

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 GRB180720B (Siegel et 
al., GCN Circ #22973) 44691 sec after trigger time at 2018-07-21 02:46:35 
UT . On our first (60s exposure)  MASTER-IAC auto-detection system 
discovered  optical transient within Swift error-box  with automatical 
magnitude ~18.0.

The observations made on zenit distance = 43.01 degrees, galaxy latitude b 
= -63.07 degree.
The moon (63 % bright part) is below the horizon(The altitude of Moon is 
-15). The distance between  moon and  object is 136
The sun  altitude  is -36.01 degree.
The object observed till 2018-07-21 03:03:36

The visibility GRB error box (coord:0.5279, -2.9170 error_box: 0.05)
at trigger time at different MASTER sites:

obj: -47.70 sun:  29.73 - Tavrida (Crimea, Russia)
obj: -41.62 sun:  72.28 - IAC, Teide, (Tenerife, Spain)
obj: -54.25 sun:  15.39 - SAAO (Sutherland, SA)
obj: -46.85 sun:  23.59 - Kislovodsk (Russia)
obj: -29.98 sun:  15.28 - Ural(Kourovka, Russia)
obj: -10.74 sun: -8.46  - Tunka (near Baykal Lake, Russia)
obj:  4.55  sun: -17.19 - Amur(Blagoveschensk)
obj:  6.72  sun:  27.64 - OAFA (Argentina)


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