LIGO/VIRGO S190814bv: No candidates from Pan-STARRS and non-detection of AT2019nme
Abstract
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.
- Publication:
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GRB Coordinates Network
- Pub Date:
- August 2019
- Bibcode:
- 2019GCN.25356....1H