{
  "bibcode": "2019GCN.26501....1O",
  "body": "S. R. Oates (U. of Birmingham), P. A. Evans (U. Leicester), A. A. Breeveld (MSSL-UCL), N. P. M. Kuin \n(UCL-MSSL), F. E. Marshall (NASA/GSFC), P. Brown (TAMU), M. De Pasquale (Istanbul U.), C. Gronwall \n(PSU), M. J. Page (UCL-MSSL),  M. H. Siegel (PSU), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), S. \nD. Barthelmy (NASA/GSFC), A. P. Beardmore (U. Leicester), D. N. Burrows (PSU), S. Campana \n(INAF-OAB), S. B. Cenko (NASA/GSFC), G. Cusumano (INAF-IASF PA), V. D���Elia (ASDC), P. Giommi (ASI), \nD. Hartmann (Clemson U.), K. L. Page (U.Leicester), J. A. Kennea (PSU), N. J. Klingler (PSU), H. A. \nKrimm (NSF), A. Y. Lien (GSFC/UMBC), D. B. Malesani (DTU Space), A. Melandri (INAF-OAB), J. A. \nNousek (PSU), P. T. O'Brien (U. Leicester), J. P. Osborne (U. Leicester), C. Pagani (U. Leicester), \nD.M. Palmer (LANL), M. Perri (ASDC), J. L. Racusin (NASA/GSFC),  T. Sakamoto (AGU), B. Sbarufatti \n(INAF-OAB/PSU), G. Tagliaferri (INAF-OAB), A. Tohuvavohu (U Toronto), and E. Troja (NASA/GSFC/UMCP) \nreport on behalf of the Swift team:\n\nWe report Swift/UVOT and XRT follow-up observations of PS19hgw (AT2019wxt; McBrien et al., GCN Circ. \n26485) found during the search for the EM counterpart of the LVC event S191213g (LIGO/VIRGO \nCollaboration GCN Circ. 26402).\n\nThis object has also been observed by MASTER (Lipunov et al., GCN Circ. 26497), TNG (D'Avanzo et \nal., GCN Circ. 26499) and SEDM (Fremling et al., GCN Circ. 26500) and spectroscopically by ePESSTO \n(M��ller Bravo et al., GCN Circ. 26494), HCT (Dutta et al., GCN Circ. 26490), NOT (Izzo et al., GCN \nCirc. 26491) and LT (Srivastav et al., GCN Circ. 26493), indicating this transient is at z = 0.037.\n\nSwift/UVOT and XRT observations began 5.7 days after the LIGO/VIRGO trigger (LIGO/VIRGO \nCollaboration GCN Circ. 26402). Photometry is complicated by the host galaxy, however, in the Swift \narchive a pre-explosion image is available for the u filter. Comparing the u band images we measure \na ~0.8 mag enhancement in flux. For all filters, we have attempted to subtract the host by measuring \nthe host flux at a position offset from PS19hgw, but of a similar brightness as  the location of \nPS19hgw in the pre-explosion image.\n\nIn the following we give preliminary magnitudes using the UVOT photometric system (Breeveld et al. \n2011, AIP Conf. Proc. 1358, 373):\n\nFilter   T_start(s)   T_stop(s) Exp(s)     Mag\n\nv          489252       494253   157     18.53 +\\- 0.34\nb          488842\t493844   157\t 19.30 +\\- 0.32\nu          488758\t493759   157\t 18.45 +\\- 0.24\nw1         488594\t493675   315\t 18.37 +\\- 0.23\nm2         489336\t494468   1163\t 19.31 +\\- 0.32\nw2         488928\t494169   629\t 18.82 +\\- 0.27\n\nWe have checked the reliability of our host subtraction by determining the host subtracted u band \nmagnitude using the host flux measured at the location of PS19hgw in the pre-explosion image. This \nmethod results in a u filter magnitude for PS19hgw of 18.49 +\\- 0.21, consistent with the u \nmagnitude in the table above.\n\nThe magnitudes in the table are not corrected for the Galactic extinction due to the reddening of \nE(B-V) = 0.06 in the direction of the burst (Schlegel et al. 1998).\n\nIn XRT, no source was found at the location of AT2019wxt in 2.6 ks of exposure, starting 5.65 d \nafter the GW trigger. The 3-sigma upper limit is 4.74e-3 ct s^-1. This corresponds to a 0.3-10 keV \nflux upper limit of 2.04e-13 erg cm^2 s^-1, assuming a power-law spectrum with NH=3e20 cm^-2 and \nGamma=1.7.\n\nThis circular is an official product of the Swift team.",
  "circularId": 26501,
  "createdOn": 1576753996000,
  "email": "a.breeveld@ucl.ac.uk",
  "subject": "LIGO/Virgo S191213g: Swift UVOT/XRT observations of Pan-STARRS1 candidate: PS19hgw",
  "submitter": "Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>",
  "eventId": "LIGO/Virgo S191213g"
}