ANTARES high energy neutrino Alert150901.32 Error-box X-ray, B, V, R optical observations and Possible Candidate to Neutrino Source

ATel #8000; 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)
on 5 Sep 2015; 05:20 UT
Credential Certification: Nataly Tyurina (tiurina@sai.msu.ru)

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MASTER-SAAO robotic telescope (MASTER­ Net http://observ.pereplet.ru ) located in Sutherland received ANTARES neutrino alert (Dornic et al., ATel #7987) in 16s after trigger time at sunrise.

MASTER-SAAO automatically started Inspect survey on the ANTARES neutrino Alert150901.32 error-­box (ATel #7987) 35107 sec after notice time and 35123 sec after trigger time (2015-09-01 07:38:24.99, sunrise) at 2015­09­01 17:23:48 UT. Observations were up to 2015-09-01 20:25:18(very cloudy), see conditions in Table.

Observatory Observation time, UT Band, limits and exposition

  
MASTER-SAAO  from 2015-­09­-01 17:23:48   unfiltered (w=0.2B+0.8R USNOB1 calibrated) 
             up to 2015-09-01 20:25:18  18.5-19.8 (180s),20.6 (540s) 
      
MASTER-SAAO  from 2015-09-03 17:13:59    m_B_lim=19.1(180s), 19.6(540s) 
             up to 2015-09-03 21:21:59   m_V_lim=19.3(180s), 19.9sum(540s) 
                                         m_R_lim=18.4-19.0(60-180s), 19.7-20.3(540s-1800s) 
                                         m_I_lim=17.5-18.0(180s), 18.5(540s) 
 
MASTER-IAC    from 2015-09-01 21:02:44   unfiltered m_lim=18.7-19.2(180s), 19.8(540s) 
              up to 2015-09-01 21:17:34  
 
MASTER-IAC    from 2015-09-03 20:08:40   m_B_lim=19.8(180s) 
              up to 2015-09-03 22:09:12  m_V_lim=18.6(180s)  

MASTER auto-detection system didn't find any real optical transient inside the neutrino error-box.
Two MASTER telescopes (Tunka and Kislovodsk) do not recieved good images because high object zenit distance (GCN #18240).
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, 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_-12 erg/sm₂/s . MASTER-SAAO observations of USNO-B1.0 0626-0501169 in January, May and September 2015 show that unfiltered magnitude is m_w=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 3percents. 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 < 3percents. Consequently, F_x < 7 10-11 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 ( GCN #18236 , ATEL #7994 , ATel #7992 , ATel #7993 ).

There is Globular Cluster M4 (NGC621) with millisecond pulsar (Lyne et al., 1988, Nature, 332, 45-47) and possible massive (~10³ 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 Antares (!) star 1.3 degrees from center of ANTARES error box.

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

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