{
  "bibcode": "2018GCN.22419....1L",
  "body": "A. Y. Lien (GSFC/UMBC), J. A. Kennea (PSU),\nS. D. Barthelmy (GSFC), A.P. Beardmore (U. Leicester),\nP. A. Evans (U Leicester), H. A. Krimm (NSF/USRA),\nD. Malesani (DARK/NBI), C. B. Markwardt (GSFC),\nD. M. Palmer (LANL), K. L. Page (U Leicester),\nT. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL)\nreport on behalf of the Swift team:\n\nUsing the data set from the recent telemetry downlink,\nwe report further analysis of Swift J1658.2-4242 (trigger #810300)\n(Barthelmy et al., GCN Circ. 22416).\n\nUsing the BAT data from T+210 to T+963 sec, the BAT ground-calculated position is\nRA, Dec = 254.537, -42.712 deg which is\n   RA(J2000)  =  16h 58m 08.8s\n   Dec(J2000) = -42d 42' 42.1\"\nwith an uncertainty of 3.0 arcmin, (radius, sys+stat, 90% containment).\nThe partial coding was 78%.\n\nThe BAT mask-weighted light curve shows a continuous weak emission\nthat starts before and ends after the event data range from T+210 s to T+963 s.\nData from the BAT transient monitor (Krimm et al. 2013) show the source\nstarts flaring around Feb. 14, 2018, and has reached a brightness of ~ 70 mCrab\n(15-50 keV). This is generally consistent with the detections reported by INTEGRAL\n(Grebenev et al., ATEL 11306).\n\nThe BAT time-averaged spectrum from T+210.00 to T+963.02 sec is best fit by a simple\npower-law model.  The power law index of the time-averaged spectrum is\n1.98 +- 0.28.  The fluence in the 15-150 keV band is 2.2 +- 0.4 x 10^-6 erg/cm2.\nAll the quoted errors are at the 90% confidence level.\n\nSwift/XRT began observation of the transient at 06:54 UT and observed the target\nin a mixture of Windowed Timing and Photon Counting mode for a total of 3.1 ks.\nIn XRT data we localize the transient, utilizing UVOT to reduce the systematics\non astrometry, to the following coordinates: RA/Dec(J2000) = 254.55266, -42.69845,\nwhich is equivalent to:\n\nRA(J2000) = 16h 58m 12.64s,\nDec(J2000) = -42d 41m 54.4s,\n\nwith an estimated uncertainty of 1.6 arc-seconds radius (90% confidence). We note\nthat this position lies 0.4 arc-seconds from the IR source VVV J165812.62-424154.78,\nfrom the VISTA Variables DR2 catalog (Minniti et al., 2017), which has magnitudes\nH=16.2 and K=15.252. In addition G343.2514+00.0537, a source in the GLIMPSE catalog,\nis also consistent with the XRT localization.\n\nSpectral fits to the PC and WT data are consistent, although as WT data are unaffected\nby pile-up we report that fit here. The spectrum is well fit by a highly absorbed\npower-law model, with NH = 1.9 +/- 0.5  10^23 cm-2, and photon index = 1.7 +/- 0.5.\nThe average flux, corrected for absorption, is ~1.6 x 10^-9 erg/s/cm2 (0.3 - 10 keV).\nThe light-curve shows some evidence of fading during the observed period, although\nplanned later observations of the new transient will be required to determine any fading.\n\nWe find no evidence of pulsations or QPOs in the XRT data, although as the data are mainly\ntaken in PC mode and suffer from pile-up, this does not place strong constraints on\nthe presence of any periodicities in the data.\n\nThe results of the batgrbproduct analysis are available at\nhttp://gcn.gsfc.nasa.gov/notices_s/810300/BA/\n\nThe results of the BAT transient monitor are available at\nhttps://swift.gsfc.nasa.gov/results/transients/weak/SwiftJ1658.2-4242/",
  "circularId": 22419,
  "createdOn": 1518806560000,
  "email": "amy.y.lien@nasa.gov",
  "subject": "Swift J1658.2-4242: Swift BAT and XRT refined analysis",
  "submitter": "Amy Lien at GSFC  <amy.y.lien@nasa.gov>"
}