Gamma-ray Burst 130623A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #14921
  J. R. Cummings reports on behalf of the Swift-BAT team:
  At 11:42:44.7 UTC, the time of Fermi-GBM trigger 393680570, Swift was executing a pre- planned slew. BAT photon detection event data was recorded during this slew. In ground analysis in a mosaic image, a significant source was found in found at RA, Dec 20.723, -77.784, which is:

  RA (J2000)   01h 22m 53.5s
  Dec (J2000) -77d 47m 04s
  

  with an estimated 90% confidence radius of 4 arcmin. The burst was a long GRB with 3 distinct peaks. T90 was about 15 +/- 2 sec.
  The spectrum from T0 to T0+15 sec is best fit by a simple powerlaw with a photon index of 1.8 +/- 0.2. The fluence from T0 to T+15 was (5.4 +/- 1.1) x 10^-0.7 ergs/cm^2. The 1-second peak flux from T+0.6 sec was 1.4 +/- 0.3 photons/cm^2/sec.
  A Swift TOO request has been approved.
• GCN Circular #14926
  Dirk Grupe (PSU), Phil Evans (Leicester), Jackie S. Linevsky (PSU/CBHS), and Mike Siegel (PSU) report on behalf of the Swift team:
  We have analyzed 5.0 ks of XRT data for the Swift/BAT-detected burst: GRB 130623A (Cummings, GCN circ. 14921), from 100.4 ks to 119.3 ks after the Swift/BAT trigger. The data are entirely in Photon Counting (PC) mode. An X-ray source is detected within the Swift/BAT error circle. The refined XRT position is RA, Dec = 20.85346, -77.77338 which is equivalent to:

  RA (J2000): 01 23 24.83
  Dec(J2000): -77 46 24.2
  

  with an uncertainty of 4.5 arcsec (radius, 90% confidence). This position is 106 arcsec from the Swift/BAT position. This source has a count rate in the XRT of (2.7+3.1-1.9)e-3 counts/s which is equivalent of an X-ray flux of 1.4e-13 erg/s/cm2 assuming a standard X-ray afterglow spectrum. We cannot determine at the present time whether the source is fading.
  The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00020284.
  Swift UVOT observed the field of GRB 130623A for 4611s. There is no source at the X-ray position in the white image. The 3sigma upper limit is 22.6 mag in the Vega system. This magnitude is not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.05 in the direction of the burst (Schlegel et al. 1998).
  This circular is an official product of the Swift team.
• GCN Circular #14940
  D. Byrne (UCD), A. von Kienlin (MPE) and W. Paciesas (UAH) report on the behalf of the Fermi GBM Team:
  "At 11:42:47.05 UT on 23 June 2013, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 130623A (trigger 393680570 / 130623488), which was also detected by the Swift/BAT (J. R. Cummings 2013, GCN 14921). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 46 degrees.
  The GBM light curve consists of four peaks within 30s of the trigger time with a duration (T90) of about 21 s (50-300 keV).
  The time-averaged spectrum from T0-6.144s to T0+24.576s is well fit by a power law function with an exponential high-energy cutoff. The power law index is -1.03 +/- 0.53 and the cutoff energy, parameterized as Epeak, is 26.11 +/- 4.67 keV.
  The event fluence (10-1000 keV) in this time interval is (2.63 +/- 0.20)E-06 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0+13.568 s in the 10-1000 keV band is 5.07 +/- 0.25 ph/s/cm^2.
  The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
• GCN Circular #14964
  Dirk Grupe (PSU) reports on behalf of the Swift team:
  Swift reobserved the field of the ground-detected GRB 130623A (Cummings, GCN circ. 14921) again on 2013-June-30 for 10.25 ks. The source reported initially in Grupe et al. (circular 14926) seems to have faded. We do not detect the source anymore and can only measure a 3 sigma upper limit at a level of 1.9e-3 counts/s in the XRT. This measurement suggests that the source reported in Grupe et al. (circular 14926) is may be the X-ray afterglow of GRB 130623A.
  The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00020284.
  This circular is an official product of the Swift XRT team.
• GCN Circular #15080
  K. Varela (MPE Garching), A.C. Updike (Roger Williams University), J. Elliott (MPE Garching), J. Greiner (MPE Garching) and D.A. Kann (TLS Tautenburg) report on behalf of the GROND team:
  We observed the field of GRB 130623A (Cummings et al., GCN #14921) simultaneously in g'r'i'z'JHKs with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla Observatory (Chile).
  The first epoch observation started at 09:15 UT on 25 June 2013, 33.7 hrs after the GRB trigger. They were performed at an average seeing of 1."5 and at an average airmass of 1.6. We find a single point source at the edge of the 4."5 Swift-XRT error circle reported by Grupe et al. (GCN #14926) at

  RA  (J2000.0) = 01:23:26.17 = 20.859063
  DEC (J2000.0) = -77:46:24.0 = -77.773361
  

  with an uncertainty of 0.3" in each coordinate.
  Based on a total exposure of 50 minutes in g'r'i'z' and 40 minutes in JHK, we estimate preliminary magnitudes (all in AB) of

  g' = 22.5 +/- 0.1 mag,
  r' = 22.4 +/- 0.1 mag,
  i' = 22.2 +/- 0.1 mag,
  z' = 21.9 +/- 0.1 mag,
  J = 21.3 +/- 0.3 mag,
  H = 20.5 +/- 0.3 mag, and
  K > 20.2 mag.
  

  The second epoch observations started at 08:29 UT on 05 August 2013, 42 days after the GRB trigger. They were performed at an average seeing of 1."3 and at an average airmass of 1.5. The source found in the first epoch is not detected anymore: Based on a total exposure of 75 minutes in g'r'i'z' and 60 minutes in JHK, we estimate preliminary upper limits (all in AB) of

  g'  > 25.7
  r'  > 25.2
  i'  > 24.3
  z'  > 24.0
  J  > 21.8
  H  > 20.9
  Ks > 20.4
  

  The fading by nearly 3 mag in the r'-band proves it to have been the afterglow of GRB 130623A. The clear detection down to the g'-band implies a redshift smaller than 3.
  Given magnitudes are calibrated against GROND zeropoints as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.05 mag in the direction of the burst (Schlegel et al. 1998).