TITLE: GCN CIRCULAR NUMBER: 25356 SUBJECT: LIGO/VIRGO S190814bv: No candidates from Pan-STARRS and non-detection of AT2019nme DATE: 19/08/15 23:15:05 GMT FROM: Stephen Smartt at Queen's U/Belfast M. Huber (IfA, Univ. of Hawaii), K. W. Smith (QUB), K. Chambers, A. Schulz (IfA), S. Smartt, D. R. Young, O. McBrien, J. Gillanders. S. Srivastav, D. O'Neil, P. Clark, S. Sim (QUB), T. de Boer, J. Bulger, J. Fairlamb, M. Huber, C.-C. Lin, T. Lowe, E. Magnier, R. J. Wainscoat, M. Willman (IfA, Univ. of Hawaii), T.-W, Chen (MPE), A. Rest (STScI), C. Stubbs (Harvard) We report observations of the LALInference skymap of the NSBH event S190814bv (The LIGO Scientific Collaboration and the Virgo Collaboration, 25333, 25324) with the Pan-STARRS1 telescope (Chambers et al. 2016, arXiv:1612.05560C). Images were taken in the PS1 i and z bands (Tonry et al. 2012, ApJ 750, 99). Beginning at 2019-08-15 12:40:37 UT (58710.5282) or 15.5hrs after the detection of S190814bv, observations started in the i-band. We used the updated LALInference.v1.fits.gz map for pointing coverage. Observations finished at 2019-08-15 15:13:38 UT. At each pointing position a dithered sequence of 45 sec i-band and z-band images were taken. These were combined into a single night stack, covering the GPC1 camera chip gaps. These dithered sequences were repeated, with overlaps, to map 18 square degrees of the LALInference.v1.gz map 90% credible region, corresponding to a summed probability 89% of the skymap. We did not cover the smaller probability blob to the south east at DEC=-32. Conditions were somewhat affected by clouds, and moon, seeing was around 1.2 - 1.3 arcsec. 5-sigma limiting magnitudes were around i ~ 20.8 and z ~ 20.3. The images were processed with the IPP (Magnier et al. 2016, arXiv:1612.05240) and difference images were produced using the Pan-STARRS1 Science Consortium 3Pi images as reference frames. Transient candidates were run through our 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), and already reported transients in the TNS before S190814by. After removing these, and requiring detections in BOTH i and z-band stacks, we were left with two transients. Both of which we discount as possible counterparts. Name | TNS Name | RA (J2000) | Dec (J2000) | Disc MJD | i Mag err | z Mag err PS19epf | AT2019noq | 00 48 47.88 | -25 18 23.4 | 58710.58 | 19.93 0.11 | 20.17 0.16 PS19eph | AT2019nor | 00 49 51.99 | -24 16 17.7 | 58710.59 | 19.69 0.07 | 19.55 0.07 PS19epf is within the inner 20% contour. It is located 0.46"S 3.96"E from the centre of the galaxy PSO J012.1980-25.3064 (r = 18.3 Kron mag). The host has no measured photometric or spectroscopic redshift. However there are 4 separate, single night detections in the ZTF public stream, from Lasair (Smith et al. 2019; https://lasair.roe.ac.uk/object/ZTF19abkhnce/), across the last 12 days. Hence it is most probably a SN exploding before the GW. PS19eph is within the inner 10% contour. However it is coincident with the core of the B=18.67 galaxy 6dF J0049520-241618 at z = 0.436522 from NED, and hence is not likely related to S190814bv. We do not recover desgw-190814b (AT2019nme). Reported at i=19.33 z=19.39, (58710.278) by Soares-Santos et al. GCN 25336. This is on the edge of our stack, but we estimate a 3-sigma limit of i~20.6 z~20.2. If it is real, it implies a very fast fade in i-band of 1 mag in about 8hrs. Deeper follow-up is required, and confirmation from the DECam team if it is real.