[vsnet-grb-info 20077] Pan-STARRS follow-up of IceCube-171106A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22173
SUBJECT: Pan-STARRS follow-up of IceCube-171106A
DATE:    17/11/28 12:57:11 GMT
FROM:    O. McBrien at QUB  <omcbrien02 at qub.ac.uk>

O. McBrien, K. W. Smith, S.J. Smartt, D. R. Young (Queen's University
Belfast), M. Huber, K. C. Chambers, H. Flewelling, M. Willman, A.
Schultz, E. Magnier, C. Waters, J. Bulger, R. J. Wainscoat (IfA,
Hawaii), D. Wright, (Univ. of Minnesota),

Further to the detection of the Extremely High Energy neutrino event
IceCube-171106A (see GCN #22105), we report Pan-STARRS1 imaging of the
field and the search for optical transients.

We observed the field of the neutrino event at RA=340.0 degrees and
DEC=+7.4 degrees (J2000) from MJD 58065.34 (2017-11-08 08:09:36.0
UTC), 37.44 hrs following the IceCube detection with the Pan-STARRS1
telescope in both the i-band and z-band filters (Chambers et al.
arXiv:1612.05560). Difference imaging with respect to the Pan-STARRS1
3Pi stacked reference sky reached 5-sigma limiting magnitudes of
around i~22.5. Observations were repeated on 10 subsequent nights.

Similar to Lipunov et al. (GCN 22104), we find no bright transient
source (i,z < 20) in the field. We found 7 fainter transients, which
are not known AGN or variable stars, within 1.3 degrees of the
estimated position of the neutrino (RA: 340.00, Dec: +7.40). These are
all detected over multiple nights. None of them appear to be rising or
have a lightcurve that points at a possible temporal coincidence with
IceCube-171106A, though two are contained within a 0.7 degree (42
arcmin) radius of the neutrino detection. Three are supernova like
candidates, and four are coincident with galaxy cores. These nuclear
transients are probably real, but difficult to distinguish between low
level nuclear variability and a true transient source. We report the
discovery magnitudes, dates and sky locations of the transients for
the transients in the 0.7 degree (42 arcmin) radius and those outside
it separately as follows.

Within 0.7 degree of IceCube-171106A 

PS Name | RA (J2000)  | Dec (J2000) | Ang. Separation (arcmin) |  Disc. Date  | Disc. Mag. | Notes
PS17fcc   | 22 41 58.64 | +07 46 53.8  | 37.3                                  |  20171108  |  21.54 i       |  (1)
PS17eym | 22 39 22.13 | +07 16 36.4  | 11.9                                  |  20171108  |  21.48 i       |  (2)


Outside 0.7 degree of IceCube-171106A, but within PS1 footprint 


PS Name | RA (J2000)   | Dec (J2000) | Ang. Separation (arcmin) |  Disc. Date  | Disc. Mag. | Notes
PS17fcd   | 22 44 01.84  | +08 13 27.6 | 77.7                                   |  20171109  |  21.53 z     |  (3)
PS17eyn  | 22 42 24.63  | +06 55 02.7 | 46.1                                   |  20171108  |  21.64 I      |  (4)
PS17fem  | 22 42 19.31  | +06 42 38.0 | 53.9                                   |  20171110  |  21.95 I      |  (5)
PS17eyo  | 22 40 40.92  | +06 26 29.6 | 58.4                                   |  20171108  |  22.16 I      |  (6)
PS17eyl   | 22 39 02.90  | +06 25 26.3 | 60.2                                   |  20171108  |  21.23 i      |  (7)


(1) Nuclear transient candidate located 0.59 arcsec N, 0.28 arcsec W
of host galaxy (SDSS J224158.66+074653.2). Transient is within 42
arcmin of neutrino detection. 

(2) SN-like candidate associated
with galaxy SDSS J223922.20+071638.0, located 1.80 arcsec S, 0.97
arcsec W from galactic centre, with a host photometric redshift 0.38
+/- 0.11. Transient is within 42 arcmin of neutrino detection. 

(3) Nuclear transient candidate located 0.37 arcsec N, 0.13 arcsec W
of host galaxy (SDSS J224401.85+081327.5). Difference imaging shows
positive and negative net flux, implying some galactic core activity.


(4) Nuclear transient candidate located 0.58 arcsec N, 0.84 arcsec E
of host galaxy (SDSS J224224.58+065502.1). 

(5) Nuclear transient candidate located 0.57 arcsec N, 0.41 arcsec E
of host galaxy (SDSS J224219.29+064237.5).

(6) SN-like candidate not matched with catalogued galaxy. 

(7) SN-like candidate associated with galaxy SDSS J223902.90+062526.6,
located 0.28 arcsec S, 0.04 arcsec E from galactic centre, with a host
photometric redshift 0.24 +/- 0.10.