Gamma-ray Burst 081025

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN/BACODINE POSITION NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Sat 25 Oct 08 16:55:39 UT
  NOTICE_TYPE:     Swift-BAT Slew GRB Position
  ID_NUM:          21
  GRB_RA:          245.300d {+16h 21m 12s} (J2000),
                   245.334d {+16h 21m 20s} (current),
                   245.107d {+16h 20m 26s} (1950)
  GRB_DEC:         +60.470d {+60d 28' 12"} (J2000),
                   +60.449d {+60d 26' 58"} (current),
                   +60.587d {+60d 35' 12"} (1950)
  GRB_ERROR:       1.93 [arcmin radius, statistical only]
  GRB_INTEN:       1357110 [cnts]    Image_Peak=0 [image_cnts]
  TRIGGER_DUR:     89.800 [sec] 
  TRIGGER_INDEX:   10     Criteria: S(15-50) > 4.0 sigma  AND  H(50-150) > 4.0 sigma
  ENERGY_RANGE:    15-150 keV
  BKG_INTEN:       0 [cnts]
  BKG_TIME:        0.00 SOD {00:00:00.00} UT
  BKG_DUR:         0 [sec]
  GRB_DATE:        14764 TJD;   299 DOY;   08/10/25
  GRB_TIME:        30196.18 SOD {08:23:16.18} UT
  SOLN_STATUS:     0x13
  RATE_SIGNIF:     0.00 [sigma]
  IMAGE_SIGNIF:    0.00 [sigma]
  SUN_POSTN:       210.45d {+14h 01m 48s}  -12.39d {-12d 23' 28"}
  SUN_DIST:         77.97 [deg]   Sun_angle= -2.3 [hr] (East of Sun)
  MOON_POSTN:      173.85d {+11h 35m 23s}   -0.86d {-00d 51' 19"}
  MOON_DIST:        81.75 [deg]
  MOON_ILLUM:      11 [%]
  GAL_COORDS:       91.42, 41.62 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      197.45, 77.53 [deg] ecliptic lon,lat of the burst (or transient)
  COMMENTS:        SWIFT-BAT Slew GRB Coordinates.  
  COMMENTS:        A point_source was found.  
  COMMENTS:        This does not match any source in the ground catalog.  
  COMMENTS:        This is a GRB.  
  COMMENTS:        Extremely high confidence of reality (gold-plated).  
  COMMENTS:        This Notice was ground-processed from flight-data.  
  COMMENTS:          
  

• red DSS finding chart ps-file
  
  
• GCN Circular #8409
  A. Copete, J. Grindlay (Harvard) J. Cummings, S. Barthelmy, C. Markwardt, N. Gehrels (NASA/GSFC)
  We report the detection of a GRB candidate by the BAT Slew Survey (BATSS) in the slew that started at 08:22:02 UT. The ground-calculated position is RA, Dec = 245.298 +60.466 deg, which is

    RA (J2000) =  16h 21m 11s
    Dec(J2000) = +60d 27' 58"
  

  with an uncertainty of 2.87 arcmin (90% confidence, including systematic error). The detection was triggered by simultaneous independent detections of 12.9 sigma and 13.7 sigma from imaging in the 15-50 keV and 50-150 keV energy bands, respectively. The burst profile shows a series of 4 main peaks starting at T+63sec, which a measured T90 = 23sec and T50 = 17sec, and the burst leaves the BAT field-of-view at T+120.
  A follow-up Swift ToO observation has been scheduled to begin on 10/26/08 at 04:58 UT, 20.6 hours after the burst.
• GCN Circular #8411
  J. Mao, C. Guidorzi, R. Margutti (INAF-OAB) report on behalf of the Swift-XRT team:
  Swift began observing the field of the Swift-BATSS GRB 081025 (Copete et al., GCN Circ. 8409) 74.5 ks after the trigger. In 2.9 ks of Photon Counting mode data, we detect a single uncatalogued source within the BAT error circle at a position of RA, Dec = 245.36626, 60.47428, which is equivalent to

  RA(J2000):   16 21 27.90
  Dec(J2000): +60 28 27.4
  

  with an uncertainty of 6.7 arcsec (radius, 90% containment). The source lies 125 arcsec from the BAT centroid and has a count rate of ~3e-3 counts/s during this observation.
  It is not possible to determine whether this source is fading given the current statistics.
  This circular is an official product of the Swift-XRT team.
• GCN Circular #8412
  S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, P. Oleynik, D. Svinkin, M. Ulanov and T. Cline, on behalf of the Konus-Wind team report:
  The long Swift-BATSS GRB 081025 (Copete et al., GCN 8409) triggered Konus-Wind at T0=30186.316 s UT (08:23:06.316).
  The burst light curve shows a multipeaked structure with a total duration of ~25 s.
  As observed by Konus-Wind the burst had a fluence of 5.37(-0.82, +0.96)x10^-6 erg/cm2, and a 256-ms peak flux measured from T0-0.224 s of 8.90(-2.62, +2.75)x10^-7 erg/cm2/s (both in the 20 keV - 1 MeV energy range).
  The time-integrated spectrum of the burst (from T0 to T0+24.832 s) is well fitted (in the 20 keV-1 MeV range) by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.67(-0.33, +0.43) , and Ep = 222(-46, +81) keV (chi2 = 55.5/60 dof). Fitting by GRBM (Band) model yields only an upper limit on the high energy photon index: beta < -2.07.
  All the quoted errors are at the 90% confidence level.
  The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB081025_T30186/
• GCN Circular #8414
  P. Schady (MSSL/UCL) and J. Mao (INAF-OAB) report on behalf of the Swift UVOT team.
  The Swift UltraViolet/Optical Telescope (UVOT) began ToO observations of the Swift-BATSS GRB 081025 (Copete et al., GCN Circ. 8409), 20.7 hours after the trigger. We do not detect any new source at the XRT position reported in GCN Circ. 8411 (Mao et al.) in any of the individual or co-added images down to the following 3-sigma upper limits:

  Filter  Tstart(hrs)  Exp(s)  3-sigma UL
  b        21.2        130     > 19.44
  u        20.9        885     > 20.18
  uvw1     20.7        1015    > 20.60
  uvm2     22.2        886     > 20.63
  

  The values quoted above are on the UVOT Photometric System (Poole et al, 2008, MNRAS 383,627). They are not corrected for the expected Galactic extinction corresponding to a reddening of E(B-V)=0.02 mag in the direction of the burst (Schlegel et al. 1998).
• GCN Circular #8415
  J. R. Cummings (GSFC/UMBC), A. Copete (Harvard), J. Grindlay (Harvard), S. D. Barthelmy (GSFC), N. Gehrels (GSFC), C. Guidorzi (INAF-OAB)
  Using the data set from T+9 to T+129 sec (T0 is here defined as the beginning of the Swift slew manuever), we report further analysis of BATSS GRB 081025 (Copete, et al., GCN Circ. 8409).
  Using the the previously reported position, the partial coding averaged over the event was 70%. This is 2.1 arcmin from the XRT afterglow candidate (Mao et al. GCN Circ. 8411).
  The mask-weighted lightcurve features a main peak starting at T+63 sec lasting 12 sec, followed in succession by 3 peaks, a 1.4 sec long peak at T+77 sec, a 4.2 sec long peak at T+83sec, and a 2.2 sec long peak at T+88sec. T90 (15-350 keV) is 23 +- 2 sec (estimated error including systematics).
  The time-averaged spectrum from T+63 to T+89 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.12 +- 0.05. The fluence in the 15-150 keV band is (1.9 +- 0.2) x 10-06 erg/cm2. The 1-sec peak photon flux measured from T+68 sec in the 15-150 keV band is 1.3 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
  The results of the analysis will be available (in a few days) at http://gcn.gsfc.nasa.gov/notices_s/BATS0021/BA/
• GCN Circular #8418
  I. Khamitov (TUG), N. Aleksandrovich, R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), I. Bikmaev, N. Sakhibullin (KSU/AST), Z. Eker (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.)
  report:
  We observed the field of the Swift-BATSS GRB 081025 (Copete et al., GCN8409) with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National Observatory, Turkey), starting at 25 Oct, 19:51 UT, i.e. approximately 11.5 hours after the burst, using Andor CCD.
  We made 3x300s exposures in sdss-g filter, at high zenith distance (~70 degree) and with bad seeing ~ 3". We do not detect any new source inside the XRT error circle (Mao et al., GCN8411) as compared to DSS plates. Using photometric solution from previous nights we estimated the limiting magnitude of combined image as m_g ~ 22.
• GCN Circular #8420
  D. A. Kann, S. Schulze, C. Hoegner, S. Klose (TLS Tautenburg) and J. Greiner (MPE Garching) report:
  We observed the BAT Slew GRB 081025 (A. Copete et al., GCN 8409) with the TLS Tautenburg 1.34m Schmidt telescope. Observations were initialized in RRM mode (S. Klose et al., GCN 3609) as the BAT_SLEW_POSITION had been received at dusk. After obtaining 2 x 120 sec Ic-band images, we realized the large time delay and switched to deeper imaging. We further obtained 2 x 600 sec Ic-band images and one 600 sec Rc-band image.
  At the position of the X-ray afterglow candidate (J. Mao et al., GCN 8411), we do not detect any source. We find the following upper limits in comparison with the USNOB1.0 star at (catalog position, J2000) R.A. = 16:21:28.125, Dec. = +60:28:42.35, which has R2 = 18.61, I = 17.84:

  dt	exp		Filter	upper limit (2 sigma)
  
  0.38672	2x120+2x600	Ic	21.5
  
  0.40047	1x600		Rc	22.5
  

  These limits are in agreement with the g-band limit of Khamitov et al. (GCN 8418).
  We point out the existence of the galaxy cluster NSC 2162144+602602 at z=0.3903 (accoriding to SIMBAD) to the southeast of the afterglow position. The nearest galaxy (about 100" distant) seems to be a massive elliptical, possible a cD galaxy.
  No further observations are planned.
  This message may be cited.
• GCN Circular #8445
  C. Kira, Y. Hanabata, T. Uehara, T. Takahashi, Y. Fukazawa(Hiroshima U.), T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo), S. Sugita, K. Yamaoka (Aoyama Gakuin U.), M. Ohno, M. Kokubun, M. Suzuki, T. Takahashi (ISAS/JAXA), Y.E. Nakagawa, T. Tamagawa (RIKEN), M. Tashiro, Y. Terada, Y. Urata, A. Endo, K. Onda, N. Kodaka, K. Morigami, T. Sugasahara, W. Iwakiri (Saitama U.), E. Sonoda, M. Yamauchi, H. Tanaka, R. Hara, N. Ohmori, K. Kono, H.Hayashi, (Univ. of Miyazaki),S. Hong (Nihon U.), on behalf of the Suzaku WAM team, report:
  The long GRB 081025 (Copete et al., GCN 8409) triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at 2008-10-25 08:23:07 UT (=T0). The observed light curve shows a multi-peaked structure starting at T0-0.5s, ending at T0+21.5s, with a duration (T90) of about 22 seconds. The fluence in 100 - 1000 keV was 3.8(-0.7, +0.5)*10^-06 erg/cm^2. The 1-s peak flux measured from T0 was 1.5 +/- 0.2 photons/cm^2/s in the same energy range.
  Preliminary result shows that the time-averaged spectrum from T0-0.5s to T0+21.5s is well fitted by a single power-law with a photon index of 1.93 (-0.25, +0.29) (chi^2/d.o.f = 10/9).
  All the quoted errors are at statistical 90% confidence level, in which the systematic uncertainties are not included.
  The light curves for this burst are available at: http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html
• GCN Circular #8483
  A. von Kienlin (MPE) and E. Bissaldi (MPE) report on behalf of the Fermi GBM Team:
  "At 08:23:05.29 UT on 25 October 2008, the Fermi GBM triggered and located GRB 081025 (trigger 246615786 / 081025349) which was also detected by the SWIFT-BAT Slew Survey (A. Copete et al. 2008, GCN 8409) and followed up by SWIFT-XRT (J. Mao et al. 2008, GCN 8411). The GBM on-ground location is consistent with the Swift position.
  The GBM light curve shows a multipeaked structure with a duration (T90) of about 45 s (8-1000 keV). The time-averaged spectrum from T0-1.536 s to T0+24.064 s is best fit by an exponentially cutoff power law model with Epeak = 251 +/- 25 keV, and index -0.35 +/- 0.13 (chi squared 736 for 700 d.o.f.). The event fluence (8-1000 keV) in this time interval is (7.1 +/- 0.5)E-06 erg/cm^2. The 1-sec photon flux measured from T+2.56 sec in the 8-1000 keV band is 4.50 +/- 0.22 ph/cm2/sec. A Band function fit the spectrum equally well (chi squared 732 for 699 d.o.f.) with Epeak= 200 +/- 33 keV, alpha = 0.15 +/- 0.22 and beta = -2.05 +/- 0.25.
  The spectral analysis results presented above are preliminary; final results
  will be published in the GBM GRB Catalog."
• GCN Circular #8514
  J. Mao (INAF-OAB) on behalf of the Swift-XRT team reports:
  Swift-XRT re-observed the Swift-BATSS GRB 081025 (Copete et al., GCN 8409) from 12.9 days after the burst with an exposure time of 6.9 ks.
  We did not detect any source in the field. The 3-sigma upper limit is 1.7e-3 count/s. We compared this result with the previous observation (Mao et al., GCN 8411). Thus we confirm that XRT observed the fading afterglow of GRB 081025.
  This circular is an official product of the Swift-XRT team.
• GCN Report 175.1
  GCN_Report 175.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_175_1.pdf by J. Mao at INAF-OAB titled: "Final Swift report on GRB 081025"