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
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