TITLE: GCN CIRCULAR NUMBER: 24210 SUBJECT: LIGO/Virgo S190425z: Pan-STARRS observations and transients in the skymap DATE: 19/04/26 05:33:19 GMT FROM: Ken Smith at Queen's University Belfast K. W. Smith, D. R. Young, O. McBrien, J. Gillanders. S. Srivastav, S. J. Smartt, D. O'Neil, P. Clark, S. Sim (QUB), K. C. Chambers , M. Huber, E. Magnier, A. Schultz, (IfA, Univ. Hawaii), L. Denneau, H. Flewelling, A. Heinze, J. Tonry, H. Weiland, A. Rest (STScI), B. Stalder (LSST), C. Stubbs (Harvard) We report observations of the BAYESTAR skymap of the BNS event S190425z (The LIGO Scientific Collaboration and the Virgo Collaboration, GCN 24168) with the Pan-STARRS1 telescope (Chambers et al. 2016, arXiv:1612.05560C). Images were taken in the PS1 i-band (Tonry et al. 2012, ApJ 750, 99) and at each pointing position a dithered sequence of 4 x 45 sec was taken. These dithered sequences were repeated, with overlaps, to map 1258.10 square degrees of the bayestar map 90% credible region and covered a sky region totalling of 28.1% of the event's localisation likelihood. We began taking data at 2019-04-25 09:39:48 (UTC). The images were processed with the IPP (Magnier et al. 2016, arXiv:1612.05240) and difference images for the co-added stacks were produced using the Pan-STARRS1 Science Consortium 3Pi data to detect transient objects. Standard filtering procedures, combined with a machine learning algorithm (Wright et al. 2015, MNRAS, 449, 451) were applied and all candidates were spatially cross- matched with known minor planets, and major star, galaxy, AGN and multi- wavelength catalogues (as described in Smartt et al. 2016, MNRAS, 462 4094). We report the following transients (bPC denotes the probability contour within which the transient is found according to the bayestar.fits map). Name | PS Name | RA (J2000) | Dec (J2000) | z | Disc Mag | bPC | Notes AT2019ebu | PS19pp | 14 19 49.43 | +33 00 21.7 | | 20.77 i | 30 | AT2019ebw | PS19pq | 15 02 17.02 | +31 14 51.6 | | 20.92 i | 10 | AT2019ebv | PS19pr | 15 02 41.20 | +29 12 01.7 | | 20.98 i | 70 | AT2019eby | PS19ps | 15 10 15.68 | +33 04 17.6 | | 20.22 i | 10 | AT2019ebz | PS19pv | 15 25 41.74 | +32 19 42.9 | | 20.01 i | 10 | AT2019ecc | PS19pw | 15 26 29.53 | +31 39 47.5 | | 20.10 i | 10 | AT2019ecb | PS19px | 15 32 23.52 | +31 04 19.2 | 0.066 | 21.15 i | 10 | (1) AT2019ece | PS19py | 15 32 54.55 | +33 29 00.8 | 0.083 | 20.33 i | 20 | (2) AT2019ecg | PS19qa | 15 35 02.10 | +31 08 02.6 | | 21.56 i | 10 | AT2019ecf | PS19qb | 15 37 22.53 | +31 35 24.5 | | 20.67 i | 10 | AT2019ech | PS19qd | 15 41 53.81 | +26 59 12.9 | | 20.67 i | 10 | AT2019eck | PS19qe | 15 44 24.53 | +32 41 11.0 | | 20.81 i | 20 | AT2019ecj | PS19qf | 15 45 42.22 | +31 32 42.5 | | 20.67 i | 20 | AT2019ecl | PS19qg | 15 48 11.85 | +29 12 07.1 | | 20.51 i | 10 | AT2019ebr | PS19qj | 16 35 26.48 | +22 21 36.4 | 0.152 | 19.79 i | 20 | (3) AT2019ebo | PS19qn | 16 54 54.71 | +04 51 31.5 | | 20.02 i | 10 | AT2019ebp | PS19qo | 16 59 57.74 | +12 06 18.3 | 0.045 | 20.29 i | 20 | (4) AT2019ebq | PS19qp | 17 01 18.33 | -07 00 10.4 | | 20.40 i | 10 | AT2019ebs | PS19qq | 17 09 58.27 | +07 35 44.6 | | 20.81 i | 20 | AT2019ebt | PS19qr | 17 11 35.79 | +09 48 05.6 | | 20.07 i | 40 | NOTES (1) Probable host is 2MASX J15322384+3104169 at 286 Mpc (NED) (2) Probable host is 2MASS J15325460+3328553 at 365 Mpc (NED) (3) Coincident with the core of 2MASX J16352643+2221368 at 700 Mpc (NED) (4) Probable host is 16595787+1206238 at 199 Mpc (GLADE)