Gamma-ray Burst 990907

On September 7, 1999 a GRB was detected by the BeppoSAX GRBM and WFC instruments to 8 arcmin accuracy.

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none yet

• BeppoSAX GRB alert n. 99/24 and GCN notice #404
  A GRB (GB990907) was detected by the GRBM and WFC of BeppoSAX on Sep.7, around 17:34 UT. Preliminary coordinates from WFC are:

  R.A.(2000)=112.552
  DEC(2000)= -69.394
  

  Due a less-than-optimal attitude configuration the error radius is about 8'.
• BeppoSAX GRB alert n. 99/25 and GCN notice #405
  The refined WFC position of GRB990907 is:

  R.A.  =  112.699 degrees
  Decl. = -69.406 degrees
  

  (equinox 2000). The error radius is 6'. We are planning a follow-up with NFI.
  
• GCN notice #407
  K. Hurley, on behalf of the Ulysses GRB team, and M. Feroci, on behalf of the BeppoSAX GRB team, report:
  We have obtained a preliminary IPN annulus for GRB990907 (GCN 405). This annulus is centered at RA=156.6738 deg., Decl.=-13.6899 deg. (J2000), and has a radius of 62.1237 +/- 0.080 deg. (3 sigma). It intersects the BeppoSAX NFI error circle (GCN 373) to form an ~100 arcmin.^2 error box whose corners are:

  RA(2000)        Decl.(2000)
  07h 30m 37.7s   -69o 30' 18"
  07h 29m 39.6s   -69o 24' 14"
  07h 31m 55.0s   -69o 23' 22"
  07h 31m 09.7s   -69o 18' 41"
  

  A map may be found at ssl.berkeley.edu/ipn3/990907/. Only minor refinements to this annulus are expected.
• GCN notice #408
  Tim Axelrod, Jeremy Mould and Brian Schmidt (The Research School of Astronomy and Astrophysics, The Australian National University) report the following observations of GRB990907 and GRB990908. We have imaged the position of both GRB990907 and GRB990908 with the Mount Stromlo 50inch telescope + macho camera at multiple epochs in approximately 2.4" seeing. A differential image analysis of an area 21'x21' around the BeppoSAX position of GRB990907 (GCN 405) from two images taken 1999 Sep 8.56 and 1999 Sep 9.60 shows no variable sources with residuals brighter than a magnitude of m_v=20.3. A similar analysis of a 21'x21' field centered on the BeppoSAX position of GRB990908 (GCN 406) from images taken 1999 Sep 8.48 and 1999 Sep 9.59 shows a single variable stellar object (mag approx 18), fading by 0.3 magnitudes, present at both epochs, and present on the Digital Sky Survey (RA: 06:51:10.52 DEC: -75:02:17.3 J2000). This object is most likely a short period variable star within our own galaxy, but due to our poor seeing conditions, it is possible the host could be a compact galaxy, and is therefore worthy of further investigation. No other sources were seen with residuals brighter than m_v=20.3.
• GCN notice #409
  L. Piro (IAS/CNR), M. Capalbi, R. Ricci (BeppoSAX SDC), M. Dadina (IAS/CNR & BeppoSAX SOC), L. Di Ciolo (BeppoSAX SOC), C. De Libero (BeppoSAX OCC), R.C. Butler (ASI) report:
  A BeppoSAX follow-up observation of GRB990907 (GCN 405) started on Sept. 8, 4:32 U.T. Due to technical problems the observation lasted 20 minutes only, with an exposure time of 1070 s. in the MECS(1.6-10 keV). A previously unknown X-ray source 1SAXJ0731.2-6928 is detected within the WFC error box with a MECS count rate of (2.0+/-0.6)x10^-2 cts/s. The position (equinox 2000) is R.A.=7h 31m 12 s Decl=-69 28' 10", i.e. 4' away from the center of the WFC position (GCN #405). Due to the vicinity of the source to the support grid of the detector we estimate an error of 3' in radius and a flux (2-10 keV) between 1 and 2 x 10^-12 erg/cm^2/s. The probability that a serendipitous source with similar strength is found in the WFC error circle is about 3x10^-3. We conclude that 1SAXJ0731.2-6928 is likely the X-ray afterglow of GRB990907.
• GCN notice #413
  E. Palazzi, E. Pian, N. Masetti, F. Frontera (ITESRE, CNR, Bologna), P.M. Vreeswijk, E. Rol (U. of Amsterdam), H. Pedersen, J. Hjorth (CUO, Copenhagen), J. van Paradijs (U. of Amsterdam and U. of Alabama in Huntsville), C. Kouveliotou (NASA-MSFC/USRA), P. Leisy, A. Pizzella, E. Pompei (ESO-La Silla), R. Mennickent (Univ. de Concepcion, Chile), C.G. Tinney, F. Freeman, S. Lee, J. Hawthorn (AAO), R. McMahon, S. Maddox, C. Singleton (IoA, Cambridge), and H. Jones (RSAA), on behalf of the BeppoSAX and Amsterdam/Huntsville GRB optical follow-up teams, report:
  We obtained V band images of the GRB 990907 field (GCN #405 and GCN #409) at the Anglo Australian Telescope with Taurus + MITLL2, at the ESO 1.54m Danish telescope with DFOSC, and at the ESO VLT telescope with FORS1, beginning 24.9 hrs after the GRB event. Images in other bands (R and I) were also acquired as detailed in the following table:

    Telescope   Date (UT)     Filter   Exptime    Limit mag.   Seeing
                                                  (3-sigma)     
  
      AAT      Sep  8.7698      V      480 sec      23.2        1".4
     Danish    Sep  9.3736      V     1600 sec      23.0        2".6
     Danish    Sep  9.3755      R     1600 sec      23.0        2".6
     Danish    Sep  9.3854      I     1600 sec      22.5        3".5
      AAT      Sep 10.7806      V      800 sec      22.7        2".8
      VLT      Sep 10.4111      V      180 sec      23.5        1".1
      VLT      Sep 10.4153      R      180 sec      23.6        1".1
      AAT      Sep 18.3736      V      960 sec      23.2        2".2
  

  Photometric calibration was done using standard stars in the Landolt field PG0231+051. Comparisons were made among the V, R, and I band images with the Digital Sky Survey, between the two R and among the five V frames taken at different epochs. The comparison does not show any object with significant brightness variations larger than 0.3 mag.
• GCN notice #415
  Javier Gorosabel, LAEFF-INTA (Madrid) Alberto Castro-Tirado, LAEFF-INTA (Madrid) and IAA-CSIC (Granada) Ian Bond, Nick Rattembury and Phil Yock, University of Auckland Pam Kilmartin, University of Canterbury T. Sumi (Japan) Hernan Muriel, IATE (Cordoba) Enrico Costa, IAS (Frascati), on behalf of the BSAX team report:
  We have obtained three 10-minute exposures of the BeppoSAX position of GRB 990907 (Gandolfi et al. GCN 404, 405) with the 0.61-m Mount John University Observatory (MJUO) telescope. The images were taken on Sep 9.40 UT through a broad band filter (R + I bandpass). After a visual comparison with the Digital Sky Survey, no sources varying by more than 0.3 mag were seen to the DSS-2 limit within the BSAX NFI error box (GCN 409) in agreement with the negative results provided by Palazzi et al. (GCN 413).