GCN Circular 18240

D. Dornic (CPPM), V.Lipunov (Lomonosov MSU),  S. Basa (LAM), P. A. Evans (U. 
Leicester), J. A. Kennea (PSU), E.Gorbovskoy and N. Tyurina (Lomonosov MSU), D. 
Buckley (SAAO), R. Rebolo (IAC)

MASTER-SAAO robotic telescope (MASTER��Net: http://observ.pereplet.ru) located 
in Sutherland received Antares neutrino alert at 2015-09-01 07:38:24.99UT 
(sunrise) in 16s after trigger time. So and we start observations at nearest 
available time.

MASTER-SAAO automatically started Inspect ��survey on the Antares neutrino 
Alert150901.32 error��box (ra=16 25 42 dec=��27 23 24 r=1.726600) 35107 sec after 
notice time and 35123 sec after trigger time (2015-09-01 07:38:24.99, sunrise) 
at 2015��09��01 17:23:48 UT. Observations were up to 2015-09-01 20:25:18 (very 
cloudy) . MASTER auto-detection system didn���t find any real transient inside 
the neutrino error box, the unfiltered optical limit on single images is 
18.5-19.8 (180s), the sum limit is 20.6 (540s).

Observations were continuing on 2015-09-03 17:13:59 (sunset) up to 2015-09-03 
21:21:59 (the weather disappeared). We observed in parallel MASTER twin tubes 
in different filters BV, RI. ��The optical limit in B filter on single images 
was m_B_lim=19.1 (180s), 19.6 on sum (540s) in V filter: m_V_lim=19.3(180s), 
19.9 on the sum(540s). The optical limit n R is m_R_lim=18.4-19.0 on single 
images(60-180s), m_R_lim=19.7-20.3 on sum (540s-1800s). The limit in I was 
m_I_lim=17.5-18.0 on single images(180s), 18.5 on sum (540s).

MASTER-IAC robotic telescope automatically started Inspect observations on 
2015-09-01 21:02:44, observed up to 2015-09-01 21:17:34, unfiltered 
��(W=0.2B+0.8R, USNOB1 calibrated) limit m_lim=18.7-19.2 (180s exposition), 
19.8(540s). Observations were continuing in B and V on 2015-09-03 20:08:40 up 
to 2015-09-03 22:09:12 with limit up to 19.8 in B(180s) and 18.6 in V (180s). 
No optical transient inside the neutrino error box.

The Swift location 16h 26m 02.1s -27d 18m 14s ��is difficult for observations 
from Nothern hemisphere (MASTER-Kislovodsk, -Tunka, -Ural, -Amur). It can be 
observed at sunset near the horizon.

MASTER-Kislovodsk: 02 of Sept there was rain at this observatory at sunset. 
MASTER-Kislovodsk robotic telescope automatically started Inspect survey on 
Antares Alert Alert150901.32 on 2015-09-03 16:39:11 UT, at sunset (Object: 
Altitude: 14.85, Sun: Altitude: -10.65), and were continuing up to 2015-09-03 
18:04:47 when the objects��� set. The first hour we have 7 ��of 30-s expositions 
��with bad weather condition, the optical�� limit in V is 12.0-14.1. Unfiltered 
observations ��starts from 2015-09-03 17:21:39 (Object���s Altitude: 11.01)with 
optical limit 17.8 on single images (60s expositions), 18.4 on sum (180s). No 
optical transients detected by MASTER auto-detection system inside ANTARES 
error-box.

MASTER-Tunka robotic telescope started observations of this alert at sunset at 
2015-09-03 12:40:59. The Object���s Altitude was 6.86 , the Sun: Altitude: -8.12. 
Very close to horizon, the object goes under it, 16 expositions of 60s in V,R , 
no OT inside ANTARES error-box..

MASTER-SAAO optical light curve of bright star USNO-B1.0 0626-0501169 inside 
Swift XRT error box �� in B,V,R and I bands (top diagram) and color diagram 
(bottom)�� represented here:

http://master.sai.msu.ru/static/master_antares_alert_150901.png
The source is stable in all four band as well as its color. The average color 
is:

B-V = 0.93 +- 0.06

R-I�� = 1.07 +- 0.03


  A few words about  association USNO-B1.0 0626-0501169  and X-ray Swift source 
(Dornic et al. GCN 18231
Not found
 
 
, ATel #7987 ).  Following Swift XRT observation the 
X-ray flux is changing from 5e-13 to  4e-12 erg/cm2/s (in 0.3-10keV). Full 
optical flux in MASTER system calibrates as:  15 mag correspond 6.4 
10<sub>-12</sub> erg/sm<sub>2</sub>/s .  MASTER-SAAO observations of USNO-B1.0 
0626-0501169 in January, May and September 2015 show that unfiltered magnitude 
is m (unfiltered) = 12.36 +-0.03 (Jan); 12.32+- 0.03(May) and 12.32+-0.04 
(Sep). Thus it can be argued that the brightness of the star has not changed by 
more than 3%. Since the X-ray emission occurs near the stellar photosphere, so 
due to the heating effect of its brightness should slightly increase. The 
observed brightness of the star persistence restricts the change in X-ray flux 
in September compared with a May and January: F_x/ F_opt  < 3 %. Consequently, 
F_x < 7 e-11 erg/s.  This means that the X-ray heating can  not cause optical 
variability more than  0.003 magnitude.
  It seems the X-ray is result of the X-ray flare activity of the star (de 
Ugarte Postigo et al. GCN 18236
Not found
 
 
, ATel #7994; Smartt et al. ATel 7992; Dichiara 
et al. ATel#7993 ).

There is Globular Cluster M4 (NGC621) with millisecond pulsar (Lyne et al., 
1988, Nature, V.332, 45-47) and possible massive (~10e3  Solar Mass) black hole 
inside ANTARES alert 3-sigma error box (the MASTER images of the Antares  error 
box is available at http://master.sai.msu.ru/static/Antares_alert_Image.jpeg

By the way there is star Antares (1.3 degrees from center ANTARES error box, 
but outside! ).

So, we propose M4 (with relativistic objects inside) is the possible source of 
the neutrino, which created after cosmic partical acceleration. The follow up 
millisecond pulsars observations request.

  The message may be cited.