Gamma-ray Burst 140623A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #16444
  V. B. Bhalerao (IUCAA), L. P. Singer (Caltech), M. M. Kasliwal (Carnegie Observatories/Princeton), S. B. Cenko (NASA/GSFC), A. Horesh (Weizmann Institute) and D. A. Perley (Caltech) report on behalf of the intermediate Palomar Transient Factory (iPTF) collaboration:
  Fermi GBM reported trigger 425193729 at 2014-06-23 05:22:06.600 UT. Starting 2014-06-23 05:33:07.776 UT (JD 2456831.73134, 11 min after trigger), we began our search for optical counterparts using the Palomar 48-inch Oschin telescope (P48). Based on the automated Fermi ground localization, we selected 10 fields covering an area of 74 deg^2.
  The final Fermi localization, available 2.6 hours after the trigger, differed in position by 13.4 deg. Based on the final localization and an empirical description of the systematic errors of the GBM localization (Paciesas et al. 2012, http://dx.doi.org/10.1088/0067-0049/199/1/18), we estimate a 4% chance that these fields contain the true location of the source.
  Sifting through candidate transient sources using image subtraction and standard intermediate Palomar Transient Factory vetting procedures, we detected several optical transients. The fastest fading transient was iPTF14cyb, at the coordinates:

    RA(J2000)  =  15h 01m 53.42s  (225.472574 deg)
    Dec(J2000) = +81d 11' 29.1"   (+81.191410 deg)
  

  We note that the position of 1PTF 14cyb is consistent with both the iniital ground and final localizations.

  Measured R magnitudes of iPTF14cyb are
     JD          R
  2456831.73527 18.0
  2456831.75906 19.3
  2456831.78167 19.7
  

  These are consistent with a power-law decay with index -0.93 +- 0.17.
  We observed iPTF14cyb with the Gemini Multi-Object Spectrograph mounted on the 8m Gemini North telescope beginning at 08:10 UT on 2014 June 23 (~ 2.8 hr after the GBM trigger). Two 900 s spectra were obtained, covering the wavelength range from 4000-9300 A. Super-imposed on a relatively flat continuum, we detect a number of strong absorption features, including Mg II, Fe II, Al II, Si II, Al III, C I, and C IV, at a common redshift of z = 1.92. The lack of Ly-alpha absorption in the spectrum suggests that this is the redshift of the Fermi GBM GRB. In addition, we detect strong absorption features (Mg II, Fe II) from an intervening system at a redshift of z = 1.06.
  The diagram http://www.its.caltech.edu/~lsinger/iptf/Fermi425193729.pdf shows the locations of the afterglow and the 10 P48 fields in relation to the Fermi GBM 1- and 2-sigma statistical+systematic contours.
  We have triggered follow-up observations with Swift, EVLA and CARMA. We encourage follow-up observations to confirm the nature of the source.
  We thank GoGo Inflight Wifi for internet at 10,000 feet.
• GCN Circular #16450
  A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team:
  "At 05:22:06.60 UT on 23 June 2014, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 140623A (trigger 425193729 / 140623224), which was observed by the intermediate Palomar Transient Factory beginning 11 minutes after trigger time, and was reported in GCN 16425 (Bhalerao et al. 2014) as iPTF14cvb.
  The on-ground calculated location, using the GBM trigger data, is RA = 202.8, DEC = 75.8 (J2000 degrees, equivalent to 13h 31m, 75d 48'), with an uncertainty of 5.6 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). The angle from the Fermi LAT boresight is 32 degrees.
  The GBM light curve shows a multiple-peak structure with a duration (T90) of about 110 s (50-300 keV). The time-averaged spectrum from T0-49.2 s to T0+73.7 s is well fit by a power law function with an exponential high-energy cutoff. The power law index is -1.46 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 350(+220/-100) keV
  The event fluence (10-1000 keV) in this time interval is (6.8 +/- 0.6)E-06 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0-3.65 s in the 10-1000 keV band is 1.9 +/- 0.2 ph/s/cm^2.
  The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
• GCN Circular #16451
  V. D'Elia (ASDC), F. E. Marshall (NASA/GSFC), L. Izzo (URoma/ICRA) & D. Malesani (DARK/NBI) report on behalf of the Swift team:
  Following the report of a potential optical afterglow iPTF14cyb (Bhalerao et al., GCN Circ. 16442) to the Fermi/GBM-detected burst GRB 140623A (von Kienlin, GCN Circ. 16450), Swift began a follow-up observation of the iPTF field.
  We have analyzed all the 3.0 ks of XRT data for GRB 140623A, from 38.7 ks to 49.6 ks after the Fermi/GBM trigger. The data are entirely in Photon Counting (PC) mode. An X-ray source is detected at a position consistent with the candidate optical afterglow (Bhalerao et al., GCN Circ. 16442) within the Fermi/GBM error circle.
  Using 1153 s of PC mode data and 1 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 225.47927, +81.19049 which is equivalent to:

  RA (J2000): 15h 01m 55.02s
  Dec(J2000): +81d 11' 25.7"
  

  with an uncertainty of 5.8 arcsec (radius, 90% confidence). This position is 5.0 arcsec from the the optical counterpart iPTF14cyb, and consistent with it. 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/00020388.
  The Swift/UVOT began settled observations of the field of GRB 140423A 38708 s after the GBM trigger. No optical afterglow consistent with the optical position (Bhalerao et al. GCN Circ. 16442) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) are:

  Filter         T_start(s)   T_stop(s)      Exp(s)         Mag
  
  u                38708        44173          925         >22.0
  white            38926        44863          851         >21.9
  

  The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.037 in the direction of the burst (Schlegel et al. 1998).
  This circular is an official product of the Swift team.
• GCN Circular #16464
  V. D'Elia (ASDC), L. Izzo (URoma/ICRA) report on behalf of the Swift-XRT team:
  We report further Swift-XRT observations of GRB 140623A (A. von Kienlin, GCN Circ 16450; Bhalerao et al., GCN Circ. 16442). A new exposure of 5 ks has been secured 285 ks after the Fermi/GBM detection. The X-ray counterpart detected by D'Elia et al. (GCN Circ. 16451) is no longer present down to a three sigma upper limit of 2.2E-3 cts/s.
  We thus conclude that the source reported in D'Elia et al. (GCN Circ. 16451) is the X-ray afterglow of GRB 140623A.
  This circular is an official product of the Swift-XRT team.