This page is update automatically -- hit your RELOAD biutton often. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 304 SUBJECT: GRB 990510: Final BeppoSAX-WFC Coordinates DATE: 99/05/10 13:49:47 GMT FROM: Luigi Piro at IAS/CNR Frascati Luigi Piro, on behalf of the BeppoSAX team, report: A GRB (GRB 990510) was detected by the GRBM and WFC of BeppoSAX on May 10, around 8:49 U.T. Final coordinates from WFC are: R.A.(2000)=204.5248 DEC(2000)=-80.4925 The error radius is 3'. A follow-on with NFI is being done. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 309 SUBJECT: IPN localization of GRB990510 DATE: 99/05/10 20:19:19 GMT FROM: Kevin Hurley at UCBerkeley/SSL K. Hurley, on behalf of the Ulysses GRB team, and S. Barthelmy, on behalf of the GCN GRB team, report: We have obtained a preliminary IPN annulus for GRB990510 (BeppoSAX GRB ALERT GRB990510, BATSE 7560) using coarse time resolution BATSE/GCN and Ulysses data. The annulus is centered at RA(2000)= 144.801 degrees, Decl(2000)=-7.236 degrees, and has a radius of 78.074 +/- 0.034 degrees (3 sigma). It intersects the BeppoSAX refined WFC error circle and reduces its area. The intersection defines an ~4' x 6 ' error box whose corners are: RA(2000) DEC(2000) 13 h 38 m 51 s -80 o 31 ' 54 " 13 h 39 m 18 s -80 o 29 ' 51 " 13 h 37 m 05 s -80 o 31 ' 14 " 13 h 38 m 08 s -80 o 26 ' 33 " An image may be found at http://ssl.berkeley/edu/ipn3/990510. The IPN annulus can be refined considerably. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 310 SUBJECT: GRB 990510 optical observations DATE: 99/05/10 20:35:55 GMT FROM: Titus Galama at U.Amsterdam P.M. Vreeswijk, T.J. Galama, E. Rol (U. of Amsterdam), K. Pollard (U. of Canterbury), J. Menzies (SAAO), P. Sackett (U. of Groningen), K. Sahu (STScI), J. van Paradijs (U. of Amsterdam and U. of Alabama in Huntsville), and C. Kouveliotou (USRA/MSFC) report on behalf of the PLANET microlensing team and the Amsterdam/Huntsville GRB optical follow-up team: "We have observed the error box of GRB 990510 (Dadina et al. 1999; IAU Circular 7160) with the Sutherland 1.0m telescope (South Africa) in B and R (several exposures of 1200 sec) on May 10.72 UT. Comparison of the images with the DSS (2nd Epoch Survey of the UK Schmidt; RG610 filter) reveals a bright object at RA 13:38:07.62, DEC -80:29:48.8 (J2000; estimated positional uncertainy of about 2"), which is not detected in the DSS. By comparison with a couple of USNO stars we estimate R = 19.2 +- 0.3. We strongly urge further observations to be made of this possible GRB counterpart." A finding chart can be found at http://www.astro.uva.nl/~titus/grb990510.html This message is citeable. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 311 SUBJECT: GRB990510: NFI X-ray source DATE: 99/05/10 21:38:12 GMT FROM: Luigi Piro at IAS/CNR Frascati Luigi Piro (BeppoSAX Mission Scientist on behalf of the BeppoSAX team) report: BeppoSAX MAIL n. 99/8: GRB990510: possible X-ray afterglow A BeppoSAX follow-up of GRB990510 started about 8 hr after the burst. Preliminary analysis of the first two orbits of the MECS data at SOC shows a previously unknown strong source in the center of the WFC error circle. Preliminary coordinates are: R.A.(2000)= 204.605 DEC(2000)= -80.490 The error radius is 1.5' Considering its strength, this X-ray source is likely the X-ray afterglow of GB990510. BeppoSAX is continuing its observation. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 312 SUBJECT: Galactic extinction towards GRB 990510 DATE: 99/05/10 22:21:11 GMT FROM: Krzysztof Z. Stanek at CfA K. Z. Stanek (Harvard-Smithsonian CfA) notices: The proposed optical counterpart to GRB990510 (Vreeswijk et al., GCN #310) lies at the Galactic coordinates of l=305.1175, b=-18.0990. According to the all-sky reddening map of Schlegel et al. (1998; ApJ, 500, 525), at this position the expected E(B-V) reddening due to the Galactic foreground is E(B-V)=0.227, i.e. rather considerable. This corresponds to expected values of Galactic extinction A_U=1.13, A_B=0.98, A_V=0.74, A_R=0.60 and A_I=0.44, for the Landolt CTIO filters and standard reddening curve. This might influence planned optical follow-up of GRB990510. This message is citeable. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 313 SUBJECT: GRB 990510 optical observations DATE: 99/05/11 02:15:39 GMT FROM: Titus Galama at U.Amsterdam T.J. Galama, P.M. Vreeswijk, E. Rol (U. of Amsterdam), N. Tanvir (Institute of Astronomy, Cambridge, UK), E. Palazzi, E. Pian, N. Masetti, F. Frontera (ITESRE, CNR, Bologna), K. Pollard (U. of Canterbury), J. Menzies (SAAO), P. Sackett (U. of Groningen), K. Sahu (STScI), J. van Paradijs (U. of Amsterdam and U. of Alabama in Huntsville), and C. Kouveliotou (USRA/MSFC) report on behalf of the PLANET microlensing team, and the Bologna and Amsterdam/Huntsville GRB optical follow-up teams: Comparison of European Southern Observatory 2.2m and SAAO Sutherland 1.0m telescope (South Africa) R-band observations, of the error box of GRB 990510 (Dadina et al. 1999; IAU Circular 7160), shows that the proposed optical counterpart to GRB 990510 (Vreeswijk et al., GCN #310) is decaying in brightness. We obtain the following magnitudes (measured with respect to the USNO star at RA = 13:38:00.82, DEC=-80:29:11.7, for which we have assumed R = 17.2): R mag err May (UT) Telescope 19.11 0.02 10.73 SAAO 1m 19.17 0.02 10.76 SAAO 1m 19.25 0.02 10.79 SAAO 1m 19.61 0.01 10.99 ESO 2.2m The absolute uncertainty in the calibration is not included. The decay is consistent with a power law, with temporal decay index -0.85 +- 0.04. The light curve can be found at http://www.astro.uva.nl/~titus/grb990510.html This message is citeable. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 314 SUBJECT: GRB 990510 optical observations DATE: 99/05/11 05:31:52 GMT FROM: Krzysztof Z. Stanek at CfA J. Kaluzny (Warsaw Univ. Obs.), P. M. Garnavich, K. Z. Stanek (Harvard-Smithsonian CfA), W. Pych (Warsaw Univ. Obs.) and I. Thompson (Carnegie Obs.) report: We measured the object at RA 13:38:07.64, Decl -80:29:48.8 (J2000) (coordinates based on the GSC catalog), reported by Vreeswijk et al. (GCN 310) to be a possible optical counterpart to GRB 990510 in our R-band images taken with the 1.0-meter Swope telescope at the Las Campanas Obs. We find that the object declined by 0.34 mag over 4.6 hours beginning May 10.995 (UT) in the R-band. The data is consistent with a power-law decline with decay index of 0.89, obtained by fitting combined data of Galama et al. (GCN 313) and ours. The comparison star (end figures of 00.82, 11.7) assumed by Galama et al. to be R=17.2 is actually given in the USNO A2.0 catalog as R=16.5. We find the R magnitudes in this region of the USNO catalog to be of dubious quality, especially fainter than 16.5. It is important to obtain an independent photometric calibration for this field. Adding seven 300s exposures in R with approximately 1" seeing reveals an object 1.8" south of the OT and about 3 magnitudes fainter which may be the host galaxy. Compared to nearby field stars, the OT appears significantly bluer by approximately 0.4 mag in V-R color. The R-band lightcurve and the combined image of the field are available at http://cfa-www.harvard.edu/~peterg/grb.html. This message is citeable. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 315 SUBJECT: GRB990510 DATE: 99/05/11 12:56:04 GMT FROM: Brian Schmidt at Australian Nat. U. Tim Axelrod, Jeremy Mould, and Brian Schmidt (Research School of Astronomy and Astrophysics, The Australian National University) report the following optical photometry of GRB990510 using the Mount Stromlo 50inch + Macho Camera (measured with respect to the USNO star at RA = 13:38:00.82, DEC=-80:29:11.7 for which we have assumed R = 17.2, cf. Galama et al GCN 313). The following observations are Macho R (effective lambda = 700nm), but transform almost identically to R_c. R mag err May (UT) Telescope 18.24 0.02 10.514 MSO 50inch 18.31 0.02 10.522 MSO 50inch 18.30 0.02 10.529 MSO 50inch 19.23 0.07 10.775 MSO 50inch 19.31 0.07 10.783 MSO 50inch 19.25 0.04 10.791 MSO 50inch The absolute uncertainty in the calibration is not included. The decay is consistent with a power law, with temporal decay index -0.88 +- 0.03. Simultaneous observations in Macho-B (effective lambda = 510nm) show a powerlaw decay of index -0.94 +- 0.04. This message is citeable. [GCN OP NOTE: This circular was received at 20:26 11 May 99 UT, but was delayed in distribution due to not having a prior vetting account.] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 316 SUBJECT: GRB990510 optical observations DATE: 99/05/11 13:06:28 GMT FROM: Andrzej Udalski at Warsaw U. Observatory G. Pietrzynski and A. Udalski (Warsaw University Observatory) report on behalf of the OGLE microlensing survey team: We monitored the optical counterpart of GRB 990510 (Vreeswijk et al. 1999, GCN 310) starting on May 10.992 UT, 1999 with the 1.3-m Warsaw telescope at the Las Campanas Observatory (Chile). In total 17 V-band, 21 I-band frames were collected, covering about 10.25 hours. Exposure time was 900 sec and 600 sec for the V and I-band frames, respectively. The object is apparently variable -- its brightness faded by about 0.6 mag in the course of the night: from 19.45. to 20.05 in the V band and 18.50 to 19.15 in the I-band. Standard VI photometry of three, well separated nearby constant stars (uncertainty +/-0.03 mag) is: Delta X Delta Y \alpha_2000 \delta_2000 V I from GRB position Star 1 33.4"E 43.9"S 13:38:20.56 -80:30:31.9 15.617 14.636 Star 2 59.8"W 21.0"N 13:37:43.48 -80:29:26.7 16.203 15.161 Star 3 16.5"W 36.7"N 13:38:00.82 -80:29:11.5 17.014 16.094 Photometry of the optical counterpart of GRB 990510 and light curves are available from the OGLE Internet archive: http://www.astrouw.edu.pl/~ftp/ogle [GCN OP NOTE: This circular was received at 12:42 11 May 99 UT, but was not distributed due to not having a prior vetted account.] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 317 SUBJECT: GRB 990510: BeppoSAX/GRBM observations DATE: 99/05/11 19:35:50 GMT FROM: Filippo Frontera at ITESRE CNR L. Amati, F. Frontera (ITESRE/CNR, Bologna), E. Costa, M. Feroci (IAS/CNR, Rome), on behalf of the BeppoSAX/GRBM team, report: GRB990510 was detected by the BeppoSAX Gamma Ray Burst Monitor (see also IAUC #7160) as a bright, complex gamma-ray burst composed by two well separated and multi-peaked pulses with a total duration of about 75 s. The GRB fluence in the 40-700 keV energy range is (1.9 +/- 0.2) x 10E-5 erg cmE-2, while its peak flux (integrated on 1 s, same energy band) is (2.4 +/- 0.2) x 10E-6 erg cmE-2 sE-1. For comparison, the peak flux in the 2-28 keV range as measured by the BeppoSAX/WFC N. 2 (IAUC #7160) is 1.4 x 10E-7 erg cmE-2 sE-1. The fluence of the event is the highest, among the BeppoSAX localized events, after GRB990123, GRB980329, and GRB970111. The burst shows typical hard-to soft spectral evolution with an average power law photon index of 1.8 +/- 0.1 in the 70-650 keV energy band. This message is citeable. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 318 SUBJECT: GRB 990510 optical observations DATE: 99/05/12 03:20:47 GMT FROM: Krzysztof Z. Stanek at CfA K. Z. Stanek, P. M. Garnavich (Harvard-Smithsonian CfA), J. Kaluzny, W. Pych (Warsaw Univ. Obs.) and I. Thompson (Carnegie Obs.) report: We continued R-band observations with the 1.0-meter Swope telescope at the Las Campanas Obs. of the optical transient associated with the GRB 990510 on May 12.0 (UT). We find the OT declined by 1.4 mag since May 11.0, consistent with a power-law decay index of -1.36, considerably steeper than the index of -0.86 found from observations between May 10.7 and 11.0 (Galama et al. GCN 313; Axelrod et al. GCN 315). Compared to the star at RA 13:38:00.82 Dec -80:29:11.7 assumed to be R=16.5 (USNO A2.0 catalog), we find the OT to be R=20.3 on May 12.0 (UT). An updated light curve is available at http://cfa-www.harvard.edu/~peterg/grb.html. This message is citeable. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 319 SUBJECT: GRB 990510, BVI photometry DATE: 99/05/12 12:47:54 GMT FROM: Andrzej Udalski at Warsaw U. Observatory G. Pietrzynski and A. Udalski (Warsaw University Observatory) report on behalf of the OGLE microlensing survey team: Observations of the optical counterpart of GRB 990510 collected with the 1.3-m Warsaw telescope at the Las Campanas Observatory (Chile) on May 11/12, 1999 indicate that the object faded smoothly to V=21.2 and I=20.3 on May 12.4 UT. Single observation in the B-band collected on May 11.3607 UT yields the following colors of the GRB990510 counterpart: B=20.47+/-0.05, B-V=0.54+/-0.06 and V-I=0.88+/-0.04. This indicates significantely different spectral distribution as compared to regular stars. The nearby galaxy, mentioned by Kaluzny et al 1999 GCN #314, is clearly visible on collected frames. Updated photometry of the optical counterpart of GRB 990510 and light curves are available from the OGLE Internet archive: http://www.astrouw.edu.pl/~ftp/ogle [GCN OP NOTE (12May99): Due to a problem in processing this Circular, the NUMBER was erroneously assigned to be 318, when in fact it should have been 319. The archive copies have been fixed.] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 320 SUBJECT: GRB 990510 Optical Observations DATE: 99/05/12 14:43:50 GMT FROM: Jens Hjorth at U.Copenhagen GRB 990510 Optical Observations J. Hjorth (Copenhagen), I. Burud (Liege), A. Pizzella (ESO Chile), H. Pedersen (Copenhagen), A. O. Jaunsen (Oslo), B. Lindgren (Copenhagen) report: "Thirty-one 300-sec R-band images of the optical transient (OT) related to GRB 990510 (GCN #310, 312, 313) were obtained with the DFOSC at the Danish 1.54-m telescope on La Silla between 11.14 May and 11.37 May 1999 UT. The seeing FWHM ranged from 1.2" to 1.6". An astrometric plate solution (USNO-A2.0) yielded the OT coordinates RA = 13:38:07.11, Dec = -80:29:48.2 (J2000) with an uncertainty of +- 0.44". Photometry was carried out using the deconvolution code described by Magain, Courbin & Sohy (ApJ, 494, 452, 1998). Simultaneous deconvolution of the 31 images resulted in a light curve with an rms scatter of 0.016 mag. The lightcurve is consistent with a power law decay with index -1.27 in this small interval. The combined lightcurve including data from Axelrod et al. (GCN #315), Galama et al. (GCN #313) and Pietrzynski & Udalski (GCN #316) is inconsistent with a single power law. Our results thus confirm the steepening of the light curve noted by Stanek et al. (GCN #318). The faint object 2.05" south and 0.56" east of the OT is clearly seen on the deconvolved image. The object does not appear extended towards the OT. Images, deconvolved images and light curves are posted at http://www.astro.ku.dk/~jens/grb990510/ ." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 321 SUBJECT: GRB990510: optical observation DATE: 99/05/12 15:43:02 GMT FROM: Gabriele Ghisellini at Obs.Astro. di Brera S. Covino, D. Fugazza, G. Ghisellini, D. Lazzati, of the Observatory of Brera (Milan, Italy) report: We have obtained R=18.96+-0.02 for the OT of GRB990510, observed with 3x10 second exposures of VLT-FORS1 at May 11.0468. This estimate is based on the USNO star at RA = 13:38:00.82, DEC=-80:29:11.7, for which we have assumed R = 16.5. The faint object 2" south of the OT is also visible, with approximately R=21.9+-0.2 (see GCN 314). This message is citeable. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 322 SUBJECT: GRB 990510: BATSE Observations DATE: 99/05/12 22:10:44 GMT FROM: R. Marc Kippen at BATSE/UAH/MSFC R. M. Kippen (University of Alabama in Huntsville) reports on behalf of the BATSE GRB team: GRB 990510 was detected by BATSE on 1999 May 10.367434 as trigger number 7560. The event was strong and consisted of a complex series of pulses with two major episodes lasting >100 s, with significant spectral evolution. The T50 and T90 durations are 32.64 (-/+ 0.45) s and 67.58 (-/+ 1.86) s, respectively. The burst's peak flux (50-300 keV; integrated over 1.024 s) and fluence (>20 keV) are 8.16 (-/+ 0.08) photons cmE-2 sE-1 and 2.56 (-/+ 0.09) x 10E-5 erg cmE-2, respectively---ranking it in the top 4% (9%) of the BATSE burst flux (fluence) distribution. The average spectral hardness of the burst, as estimated by the ratio of 100-300 keV counts to those in the 50-100 keV range, is H32 = 0.764 (-/+ 0.008), which is average among BATSE bursts of this duration. The BATSE burst location is consistent with those measured by BeppoSAX (GCN 304,311) and the IPN (BATSE/Ulysses; GCN 309), and with the proposed optical transient counterpart (GCN 310, 313-321). A location sky-map and lightcurve for this event (and other notable bursts) are available at the BATSE Rapid Burst Response world-wide-web site: http://www.batse.msfc.nasa.gov/~kippen/batserbr/ This notice is citeable. -eof- //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 323 SUBJECT: GRB 990510: Broad Band Break DATE: 99/05/13 05:12:06 GMT FROM: Shri Kulkarni at Caltech J. S. Bloom, S. R. Kulkarni and S. Djorgovski California Institute of Technology; D. A. Frail, NRAO; T. S. Axelrod, J. R. Mould, B. P. Schmidt The Australian National University report: We have observed a number of Landolt Stars on May 11 under photometric condition with the MSO 50inch. Based on these observations we report the following magnitudes for the secondary stars discussed in GCN 316: Offset from GRB RA (J) Dec (J) R V sig Star 1 33.4"E 43.9"S 13:38:20.56 -80:30:31.9 15.09 15.58 0.03 Star 2 59.8"W 21.0"N 13:37:43.48 -80:29:26.7 15.62 16.19 0.03 Star 3 16.5"W 36.7"N 13:38:00.82 -80:29:11.5 16.50 16.99 0.03 At the time of these observations, the OT and these stars have very similar colors and we have transformed both MachoR and MachoV to standard R_C and V magnitudes from color transformations determined from the Landolt Standard stars. The corrections from VM->V and RM->R_C are less than 0.02 magnitudes in all cases, and are invariant in time, because the color of the OT is not varying significantly. Star 3 is the reference star used by Galama et al. (GCN 313) and we note that our new determination is 0.7 mag brighter than the value assumed by Galama et al. and Axelrod et al. (GCN 315). Our analysis reported below takes into account this new calibration. We report the following new measurements: DATE (UT) V Verr R Rerr May 11.508 20.11 0.09 19.67 0.07 May 11.512 20.01 0.08 19.71 0.06 May 11.516 20.06 0.07 19.76 0.09 As noted earlier (GCN #318; GCN #320) analysis of the R-band light curve shows steepening of the initially observed power law decay. We model the flux in each band with the following analytic 4-parameter function: F_nu(t) = [f_* x (t/t_*)^alpha1] x [1 - exp(-J)]/J where J(t,t_*,alpha1,alpha2) = (t/t_*)^(alpha1 - alpha2). The principal virtue of this formulation is that the asymptotic power law indices are alpha1 (at early times) and alpha2 (at late times). We have fitted this function to the MSO V and R band data of May 10 and May 11 and the R and I band data reported in earlier GCNs. Remarkably, the flux in V, R, I-bands are all consistent with same set of shape parameters, differing only by the flux normalization f_*: alpha1 = -0.88 (+/- 0.02) alpha2 = -2.5 (+/- 0.3) t_* = 1.55 days (+/- 0.05) The consistency of alpha1, alpha2 and t_* between the different bands means that the break is wide band. This is the first clear observation of a wide band break. A break due to electron cooling is strongly chromatic and the expected difference in asymptotic slopes would be small: alpha1 - alpha2 = 0.25. The simplest interpretation is that we are seeing evidence for a spreading jet. We assume that the optical band is below the cooling frequency given the relatively flat spectrum (see below). If so, application of standard afterglow models (Sari, Piran & Halpern 1999; astroph/9903339) we deduced from the measured alpha1 that the electron energy spectral index is p=2.2. In the simplest models for spreading jets (Rhoads 1999, astroph/9903399; Sari, Piran, Halpern 1999), we expect alpha2 = p. The observed value of alpha2 is consistent with this expectation. Future observations of the flux will define alpha2 better and the consistency between alpha2 and p can be tested more rigorously. However, as with the case of GRB 990123, the frequency spectral index is not consistent with theoretical expectations. After correcting for Galactic extinction (GCN 312) the spectral index in the optical (V,R) is nearly 0 on May 11." This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 324 SUBJECT: VLT spectrum of GRB990510 DATE: 99/05/13 20:50:38 GMT FROM: Paul Vreeswijk at U of Amsterdam P.M. Vreeswijk, T.J. Galama, E. Rol, B. Stappers (U. of Amsterdam), E. Palazzi, E. Pian, N. Masetti, F. Frontera (ITESRE, CNR, Bologna), J. van Paradijs (U. of Amsterdam and U. of Alabama in Huntsville), C. Kouveliotou (USRA/MSFC) and H. Boehnhardt (ESO) report on behalf of the Amsterdam/Huntsville and BeppoSAX GRB optical follow-up teams: Three 10-min red grism and three 10-min blue grism low resolution spectra covering 3300-11000 Angstrom, were taken of the optical counterpart to GRB 990510 (Vreeswijk et al.; GCN #310) with the European Southern Observatory (ESO) VLT-UT1 telescope, starting May 11.21 UT. We identified the following ultraviolet absorption lines: Fe II (2344 and 2600 Angstrom), Mg II (blend of 2796 and 2803). These lines are redshifted by z = 1.619 +- 0.002 (this may be a lower limit to the redshift of the GRB source). On the basis of this redshift we also find some weaker features, such as Al III (1863), Cr II/Zn II (2062), and Mg I (2852). No strong emission lines were detected. Assuming isotropic emission, z = 1.619, H0 = 70 km/s/Mpc and Omega0=0.3, we find a (> 20 keV) energy output of 1.4x10^{53} ergs, based on the BATSE fluence (Kippen et al.; GCN #322). This message is citeable. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 325 SUBJECT: GRB 990510: optical observation DATE: 99/05/14 00:45:00 GMT FROM: Gabriele Ghisellini at Obs.Astro. di Brera D. Lazzati, S. Covino and G. Ghisellini, of the Observatory of Brera (Milan, Italy) report: In the 600 s VLT-FORS1 image taken at May 11.13509 with 1.2" seeing, the faint source 2.1" south of the OT of GRB990510 is completely consistent with being a pointlike object, 2.86+-0.02 mag (in the R band) fainter than the source located 3.9" north, 0.8" west of the OT. At this time the latter source and the OT had the same magnitude, R=19.10+-0.02 (assuming R=16.5 for the USNO star at RA = 13:38:00.82, DEC=-80:29:11.7). This suggests that the faint source is not the host galaxy of the GRB. See in http://www.merate.mi.astro.it/~lazzati/GRB990510/ the original image, the image with the OT subtracted, and the residuals after having subtracted also the faint object, assuming it is a point source. This message is citeable. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 326 SUBJECT: GRB990510: X-ray afterglow DATE: 99/05/14 02:55:53 GMT FROM: Erik Kuulkers at SRON E. Kuulkers, J. Heise (SRON, Utrecht), L.A. Antonelli (Osservatorio Astronomico di Roma), E. Costa, L. Piro (IAS, CNR, Rome), M.R. Daniele, S. Rebecchi (SDC, Telespazio, Rome), G. Scotti (SOC, Telespazio, Rome), G. Gennaro (OCC, Telespazio, Rome), F. Frontera (University of Ferrara, Ferrara), report: The BeppoSAX NFIs observed the region of GRB990510 (see also GCN 311) from May 10.70 to May 12.22 UT, i.e. 8 to 44.5 hours after the BATSE trigger, with a total MECS on source exposure time of 68 ksec. We confirm that the strong X-ray source reported in GCN 311 is the X-ray afterglow, and is designated as 1SAX J1338.1-8030. The position as derived from the MECS observations (RA = 13 38 11, Dec = -80 29 58, J2000, 1 arcmin error radius) is consistent with both the WFC GRB position (IAUC 7160) and that for the optical afterglow source (GCN 310). The X-ray afterglow decay light curve is not unlike that seen in previous X-ray afterglow decays. We note that a previously uncatalogued weak (constant) X-ray source lies about 3 arcmin away from the X-ray afterglow source, with coordinates RA = 13 37 51, Dec = -80 26 53 (J2000, 1 arcmin error radius), which we designate 1SAX J1337.8-8027. This message may be cited. [GCN OP NOTE: This circular was delayed in distribution due to an improper vetting account. It was received at 22:42 UT. E.Kuulker's account has been updated to reflect his new affiliation.] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 328 SUBJECT: GRB990510, VI observations DATE: 99/05/14 15:02:30 GMT FROM: Andrzej Udalski at Warsaw U. Observatory G. Pietrzynski and A. Udalski (Warsaw University Observatory) report on behalf of the OGLE microlensing survey team: We continued VI-band observations of the optical counterpart of GRB 990510 on May 12/13, 1999 (seeing about 1.8") and May 13/14, 1999 (seeing about 1.1") with the 1.3-m Warsaw telescope at the Las Campanas Observatory (Chile). We report the following brightness of the object as measured in images composed of a few 600 sec exposures: UT JDhel. No of 600s Band Magnitude Error May 1999 -2450000 exposures 13.3423 1311.84493 3 I 21.05 0.13 13.3684 1311.87104 3 V 21.86 0.08 13.9980 1312.49533 3 I 21.17 0.13 14.0267 1312.52935 5 V 22.41 0.06 14.1854 1312.68804 4 I 21.35 0.07 14.2294 1312.73198 4 V 22.46 0.05 We confirm that the object located about 2" south from the optical counterpart of GRB990510 is rather a regular star (cf Lazzati et al, GCN, #325) than the host galaxy. Its point-like character is clearly seen in summed images and its photometry yields: V=22.54+/-0.06 and I=21.33+/-0.07. Updated photometry of the optical counterpart of GRB 990510 and light curves are available from the OGLE Internet archive: http://www.astrouw.edu.pl/~ftp/ogle //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 329 SUBJECT: GRB 990510: optical observations DATE: 99/05/16 23:26:57 GMT FROM: Gabriele Ghisellini at Obs.Astro. di Brera G. Marconi and G.L. Israel (Observ. of Rome, Italy), D. Lazzati, S. Covino and G. Ghisellini (Observ. of Brera, Milan, Italy) report: A 30 min exposure taken at ESO-NTT-SUSI2 1999, May 16.10984, with a seeing of 1.8" shows the OT of GRB990510 at the magnitude R=23.0+-0.1 (assuming R=16.5 for the USNO star at RA = 13:38:00.82, DEC=-80:29:11.7). The faintest detected objects in the field have R=24.5. No candidate host galaxy can be seen. We have collected all available photometric data in V, R and I. The light curve in the three bands can be fitted by the following 4 parameters formula (similar to that given by Bloom et al. in GCN 323): F_nu(t) = k t^(-al1) / [1+ (t/t_*)^(al2-al1)] where k is a normalization constant, such that the magnitude is given by m(t)=-2.5*log(F_nu). This formula fits very well the light curve in the 3 bands varying only k. We find: al1 = 0.85, al2 = 2.6, t_* = 1.8e5 sec = 2.08 days. The collection of data together with the above fit and the NTT image are posted at: http://www.merate.mi.astro.it/~gabriele/990510/ This message is citeable. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 330 SUBJECT: GRB 990510: optical linear polarization DATE: 99/05/17 11:51:55 GMT FROM: Gabriele Ghisellini at Obs.Astro. di Brera S. Covino, D. Lazzati, G. Ghisellini, P. Saracco, S. Campana, G. Chincarini (Observ. of Brera, Milan, Italy); S. Di Serego, A. Cimatti (Observ. of Arcetri, Florence, Italy); L. Vanzi, L. Pasquini (ESO, Garching, Munich, Germany); F. Haardt (Univ. of Insubria, Como, Italy); M. Vietri (Univ. of Rome III, Italy); L. Stella (Observ. of Monte Porzio, Rome, Italy); R. Falomo (Observ. of Padua, Italy); H. Boehnhardt, F. Bresolin, P. Moller, G. Rupprecht (ESO-VLT service team), report: We made imaging polarimetry of the optical transient associated to GRB 990510 at ESO-VLT-FORS1 on 1999 May 11.13509, in the R band, when the R-magnitude of the object was 19.1+/-0.02. We found linear polarization at the level of 1.7+/-0.2 per cent with position angle 12+/-4 degrees, relative to the stars in the field. This message is citeable. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 331 SUBJECT: GRB990510: photometric and spectroscopic observations with the VLT DATE: 99/05/18 17:23:27 GMT FROM: Klaus Beuermann at Goettingen Obs, Ger K. Beuermann, K. Reinsch, F.V. Hessman (Goettingen Observatory) report: Further photometry and spectroscopy performed by K. Reinsch with the ESO VLT and the FORS1 instrument as part of the FORS Consortium Guaranteed Time Observations have revealed the nature of objects close to the optical transient. The two objects 3 and 12 arcsec north of the OT with V = 20.0 and V = 23.7 are cool foreground stars of spectral types dM0 and about dM3. The object 2 arcsec south of the OT with V = 22.7 is probably a star of somewhat earlier spectral type. A spectrum of the OT taken on May 14.25 is noisy but showed no obvious features. A V-band image taken on May 18.36 with the VLT under 0.9arcsec seeing shows the OT at magnitude 24.5 with no evidence so far of the host galaxy (http://www.uni-sw.gwdg.de/~hessman/GRB/). This message is citeable. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 332 SUBJECT: GRB 990510: optical observations DATE: 99/05/18 22:10:54 GMT FROM: Gabriele Ghisellini at Obs.Astro. di Brera G. Marconi and G.L. Israel (Observ. of Rome, Italy), D. Lazzati, S. Covino and G. Ghisellini (Observ. of Brera, Milan, Italy) report: A 40 min exposure taken at ESO-NTT-SUSI2 1999, May 17.1066, with a seeing of 1.2" shows the OT of GRB990510 at the magnitude R=23.4+-0.1 (assuming R=16.5 for the USNO star at RA = 13:38:00.82, DEC=-80:29:11.7). A 50 min exposure taken on May 18.1306 (1" seeing) shows the OT at R=23.7+\-0.1. No obvious candidate host galaxy can be seen. The NTT images are posted at: http://www.merate.mi.astro.it/~gabriele/990510/ This message is citeable. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 346 SUBJECT: Late Afterglows of GRBs 990510, 990123 DATE: 99/05/27 23:17:04 GMT FROM: Arnon Dar at Technion-Israel Inst. of Tech Gravitational collapse of neutron stars (NS) to (di)quark stars (QS) due to phase transition or mass accretion are expected to generate highly relativistic jets plus a mildly relativistic spherical explosion (e.g., Dar 1999a,b). The jets, when pointing in our direction, produce GRBs, and afterglows that decline with time like F(t)\sim t^{-\alpha}/[1+(t/t_0)^{\beta-\alpha}] The spherical explosion is expected to add to it an afterglow like that of GRB 980425/SN 1998bw (Galama et al 1998; , time-dilated and redshifted by 1+z. Assuming ``a standard explosion'' = 1998bw at redshift 1+z: F(t)\sim t^{-\alpha}/[1+(t/t_0)^{\beta-\alpha}]+ SN1998bw[1+z] For GRB 990510, \alpha= 0.76, \beta=2.4, and t_0=1.57 days is the time when the jet begins to spread. The spherical explosion is expected to produce an up turn in the time-decline of the afterglow of GRB 990510 in the R band before the end of May, reach a maximum with R magnitude m=26.7\pm 0.3 between early and mid June, decline fastly by two additional magnitudes by mid August and then decline exponentially with a much smaller rate, with a half time (1+z)=2.62 longer than that of GRB 980425/SN 1998bw, i.e., t(half)=140 days. An identical behavior is expected from the late afterglow (t>20 days after explosion) of GRB 990123 (z=1.61, Kulkarni et al. 1999). [The above behavior explains better the behavior of the afterglow of GRB 970228 (z=0.69; Kulkarni 1999), t_max=20 days, m(max)=25 in the R band) than a single power-law and consistent with all the other measured GRB afterglows]. HST is urged to conduct observations of GRBs 990510 and 990123 in order to test these predictions and verify/falsify the proposed NS-->QS origin of GRBs. Dar, A. 1999a, A\&A, in press (astro-ph/9902017) Dar, A. 199b astro-ph/9905315 Galama, T. J. et al. 1998, Nature 395, 670 Kulkarni, S. R. et al 1999a, Nature, 398, 389 McKenzie, E. H. \& Schaefer, B. E. 1999 astro-ph/9904397 Stanek, K. Z. 1999, astro-ph/9905304 Vreeswijk, P. M. et al. 1999 GCN Circ. No. 324 //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 386 SUBJECT: Late-time HST/STIS Observations of GRB 990510 DATE: 99/07/12 23:05:53 GMT FROM: Andrew S. Fruchter at STScI A. Fruchter, H. Ferguson, J. Pepper, R. Gibbons, K. Sahu (STScI) and E. Pian (ITESRE-CNR, Bologna) report for the HST GRB collaboration: The field of GRB 990510 was imaged by HST on 8.1 June 1999 (UT) and 17.9 June 1999 (UT) during one and two orbits, respectively, with the STIS/CCD camera in Open Filter (50CCD) mode. The OT of GRB 990510 was detected in both cases. Assuming the color of the OT has not changed from the first few days when it could be modeled as f(nu) = nu^{-0.6} passing through a Galactic extinction of E(B-V)=0.22 (Stanek et al. 1999, Harrison et al. 1999), we find magnitudes of V = 27.0 +/- 0.2 on 8.1 June and 27.8 +/- 0.3 on 17.9 June. The STIS CCD in open filter mode is sensitive to wavelengths between 300 and 900 nm, and therefore both the conversion from counts to flux density, and the estimated PSF (which is diffraction limited) depend strongly on the assumed spectrum of the observed emission. This is of particular concern in the 17.9 June observation, where we observe some sign of extended emission about the PSF. Even though the extended emission appears to be asymmetric, subtracting a red PSF (rather than the relatively blue PSF implied by the early color) largely removes this emission. In any event, the GRB does not have a host galaxy brighter than V~28. The fits of Stanek et al. and Harrison et al. to the early time light curve predict, at both epochs, an OT fainter than observed by at least several tenths of a magnitude. However, the excess counts above predicted are between a factor of three (first epoch) to seven (second epoch) less than would exist were a supernova Type Ic of the luminosity of SN1998bw at the probable redshift of the GRB (z=1.6, Vreeswijk et al. 1999) superposed on the decaying power-law light curve. Sections of the images in gif format can be retrieved from http://www.stsci.edu/~fruchter/GRB/990510 . References: Harrison, F.A. et al. 1999, astro-ph/9905306. Stanek, K., Garnavich, P.M., Kaluzny, J., Pych, W. and Thompson, I. 1999, Ap. J. (Letter,submitted), astro-ph/990534. Vreeswijk, P. et al. 1999, GCN 324. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 756 SUBJECT: GRB 990510 Host Galaxy Discovery DATE: 00/07/30 00:32:12 GMT FROM: Josh Bloom at CIT GRB 990510 Host Galaxy Discovery J. S. Bloom, on behalf of the larger Caltech-NRAO-CARA GRB Collaboration, reports: "We have discovered a faint extended source nearly coincident with the position of GRB 990510. This source, which we identify as the host galaxy of GRB 990510, is visible in new HST/STIS imaging taken on 29 April 2000 as part of the HST proposal #8189 (see Fruchter et al. GCN #386) and made public on 28 July 2000. The total integration time is 5840 s taken in 8 individual exposures. Registration of the early epoch (17 June 1999) where the OT was bright reveals the OT occurred (0.064" +/- 0.009") West and (0.015" +/- 0.012") North of the center of the host galaxy. This amounts to a significant displacement of (66 +/- 9) mas or ~600 pc at a distance of z=1.62 (Galama et al. 1999), though the OT does appear to reside within the detectable light of the galaxy. The galaxy extension is PA=80.5 +/- 1.5 deg with an ellipticity of about ~0.5. Preliminary magnitude estimates reveal that V_host = 28.5 +/- 0.5 mag (referenced to star C of Beuermann et al. 1999). The host does appear to be marginally detected in the July 1999 imaging as well (although see GCN #386)." An image of the field from both epochs as well as a close-up of the host and the 3-sigma location of the GRB can be found at: http://astro.caltech.edu/~jsb/grb990510-host.ps This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 757 SUBJECT: GRB 990510: Possible detection of a host galaxy DATE: 00/07/30 04:57:38 GMT FROM: Andrew S. Fruchter at STScI A. Fruchter (STScI), R. Hook (ST-ECF), E. Pian (ITESRE-CNR, Bologna) report for a larger HST GRB collaboration: The field of GRB 990510 was imaged by HST for a third time on 29 April 2000 using the STIS/CCD camera in Open Filter (50CCD) mode, as part of our program to study this GRB (see GCN 386 for earlier results. A total exposure time of 5840 s, divided between 8 dithered observations was obtained. Based on our previous observations, we would expect the GRB to be well below the threshold of detectability -- which is for this image a V=29 point source. As predicted the OT was not detected. However, our June 1999 image had suggested the possible presence of an underlying host galaxy (see GCN 386). We therefore convolved the image with a gaussian of FWHM ~ 0."3, which is roughly comparable to the typical size of galaxies in other deep fields near the detection limit of the image for an extended source (V~28). The convolved image reveals a >3 sigma source lying under the position of the OT, with its peak lying ~0."075 East of the position of the OT. This we believe to most likely be the host of the GRB. Although the formal significance of the object is above 3 sigma, it lies in a region of significant scattered light from bright nearby stars and it is difficult to quantify the possible errors in the sky subtraction. We therefore regard the detection of this host as tentative. Our best estimate for the host's magnitude, assuming its correct identification, is V=28 +/-0.3. Deeper integrations, particularly ones taken at different roll angles, would be able to unambiguously determine the reality of this detection. The images of the field of GRB 990510 giving a clear idea of the significance of the detection can be found at: http://www.stsci.edu/~fruchter/GRB/990510