Support ATel At Patreon

[ Previous | Next | ADS ]

Pan-STARRS search for optical counterparts to the ANTARES neutrino detection

ATel #8027; S. J. Smartt, K. W. Smith (Queen's University Belfast), M. Huber, K. C. Chambers, H. Flewelling, M. Willman, N. Primak, A. Schultz, B. Gibson, E. Magnier, C. Waters, J. Tonry, R. J. Wainscoat (IfA, Hawaii), D. Wright, D. Young (QUB)
on 9 Sep 2015; 14:55 UT
Credential Certification: Stephen Smartt (s.smartt@qub.ac.uk)

Subjects: Optical, Neutrinos, Cataclysmic Variable, Supernovae, Transient

Referred to by ATel #: 8034, 8124

Dornic et al. (ATel#7987) reported a detection of a neutrino by ANTARES and the discovery of an uncatalogued and variable x-ray source within the error ANTARES neutrino box. The x-ray source is coincident within the uncertainties with the bright R=12.6 star USNO-B1.0 0626-0501169. The historical variability of this source has been catalogued by MASTER photometry (Dornic et al. ATel#8000) and many spectra have been taken since the announcement (e.g. ATels #7993, #7994, #7995, #7998) indicating an flaring star or possible x-ray binary.

Assuming that this x-ray source is unrelated to the neutrino, we observed the field with the Pan-STARRS telescope on 2015-09-05.25 UT to search for other optical transients (within a 1.15 degree radius). We took 8x240s i-band exposures and combined them into a single texp=1920s stack in the same process as for the PS1 Medium Deep Survey (e.g. Rest et al. 2014, McCrum et al. 2015). A reference i-band stack from the PS1 3Pi survey (built up between 2009-2013) was used to make a difference image.

A number of optical transients were found in the field, which are listed below in order of distance from the estimated neutrino position reported by Dornic et al (ATel #7987) (RA= 16h 25m 42s DEC = -27d 23m 24s J2000). Only one transient object was found to lie within the error radius of 18 arcmin (50% containment). This is likely a CV, flare star or large amplitude variable and is coincident with a stellar source in the Pan-STARRS1 i-band stack. This object is also catalogued in UKIDSS as the stellar source UGCS J162553.48-273731.9 at J=17.7. Five more transients are coincident with stellar sources (marked ''star'' in table below).

The faintest object is coincident with a slightly extended source which appears to be a compact galaxy. It is classed as a galaxy in UKIDSS (UGCS J162418.33-275030.0 H=17.1), but is not well resolved. The other three have no host galaxy or star, but are probable faint stellar variables.

All these objects are entirely consistent with the typical transient population found in routine operations of the PS1 Medium Deep field surveys (e.g. described in Rest et al. 2014, Drout et al. 2014, McCrum et al. 2015). They are likely faint stellar variables, plus possibly one supernova at z >~ 0.1. In summary, the Pan-STARRS i-band image of the 3.3 diameter field centred on the neutrino position contains no obvious optical transients that look unusual and would be considered candidates for a counterpart to the putative ANTARES neutrino.

 
Object                    RA          DEC        i   ierr  r(')  host object 
PSOJ 246.473-27.6255  16:25:53.46 -27:37:31.8  17.74 0.01  14.36 star 
PSOJ 246.085-26.9832  16:24:20.39 -26:58:59.4  20.78 0.10  30.42  
PSOJ 246.076-27.8417  16:24:18.33 -27:50:29.9  21.79 0.21  32.83 galaxy  
PSOJ 246.814-26.4892  16:27:15.40 -26:29:21.1  20.48 0.07  57.92  
PSOJ 246.274-28.5681  16:25:05.69 -28:34:05.3  18.80 0.02  71.14 star 
PSOJ 246.022-28.6159  16:24:05.30 -28:36:57.3  21.69 0.21  76.59 star 
PSOJ 246.827-28.6759  16:27:18.42 -28:40:33.3  21.66 0.21  80.04 star 
PSOJ 245.109-28.0829  16:20:26.20 -28:04:58.4  21.50 0.22  81.31 star 
PSOJ 245.327-26.4130  16:21:18.56 -26:24:46.6  19.97 0.06  82.98  
PSOJ 246.490-28.9444  16:25:57.56 -28:56:39.8  21.38 0.23  93.33 star