THIS FILE CHANGES WITH TIME -- HIT THE RELOAD BUTTON NOW! ///////////////////////////////////////////////////////////////////// GRB 980703 04:22:56 UT SOD=15776 sec TJD=10997 DOY=184 BATSE trigger = 6891. Seen by SAX. ///////////////////////////////////////////////////////////////////// TITLE: GCN/RXTE_ASM BURST POSITION NOTICE NOTICE_DATE: Fri 03 Jul 98 15:51:12 UT NOTICE_TYPE: RXTE-ASM Initial TRIGGER_NUM: 6891 GRB_DATE: 10997 TJD; 184 DOY; 98/07/03 GRB_TIME: 15776.00 SOD {04:22:56.00} UT POSITION_TYPE: Box GRB_RXTE_RA: 359.770d {+23h 59m 05s} (J2000), 359.751d {+23h 59m 00s} (current), 359.130d {+23h 56m 31s} (1950) GRB_RXTE_DEC: +8.560d {+08d 33' 36"} (J2000), +8.552d {+08d 33' 06"} (current), +8.282d {+08d 16' 54"} (1950) GRB_ERROR_RA1: 359.830d {+23h 59m 19s} (J2000) GRB_ERROR_DEC1: 8.620d {+08d 37' 12"} (J2000) GRB_ERROR_RA2: 359.710d {+23h 58m 50s} (J2000) GRB_ERROR_DEC2: 8.620d {+08d 37' 12"} (J2000) GRB_ERROR_RA3: 359.710d {+23h 58m 50s} (J2000) GRB_ERROR_DEC3: 8.500d {+08d 30' 00"} (J2000) GRB_ERROR_RA4: 359.830d {+23h 59m 19s} (J2000) GRB_ERROR_DEC4: 8.500d {+08d 30' 00"} (J2000) GRB_RXTE_ERROR: 0.067 [deg radius (stat+sys), 90%] GRB_RXTE_INTEN: 1700 [mCrab] SUN_POSTN: 102.03d {+06h 48m 06s} +22.98d {+22d 58' 43"} SUN_DIST: 97.79 [deg] MOON_POSTN: 205.93d {+13h 43m 43s} -6.33d {-06d 19' 41"} MOON_DIST: 153.95 [deg] COMMENTS: RXTE-ASM GRB Coordinates. COMMENTS: The error box is small enough to be approximated COMMENTS: by a circle of radius 4 arc min (including an COMMENTS: estimate of systematic error). The corners are COMMENTS: listed to satisfy the GCN format, but are close COMMENTS: in size to our estimated circle. COMMENTS: Better intensity data, durations, will be COMMENTS: reported later. [GCN Operator's Note: This copy of the notice in the GCN archive file has been modified from what was distributed. The message the ASM team sent to the GCN system had the intensity in units of "Crab" when the the GCN message importing demon was expecting/assuming "mCrab". This archive copy plus the web page table has been corrected to the proper units.] ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 123 SUBJECT: GRB980703 optical followup DATE: 98/07/04 18:56:25 GMT FROM: James Rhoads at KPNO James Rhoads, Ron Downes, and Jennifer Christensen report on behalf of the Kitt Peak Gamma Ray Burst followup team: Ron Downes and Jennifer Christensen observed the error box of GRB 980703 in R band with the Kitt Peak National Observatory 0.9m telescope. Total integration time was 1 hour, beginning at 980704 09:51 UT. The field of view is 23 arcminutes, and so includes the entire RXTE and BeppoSAX error boxes for the gamma ray burst. The seeing was poor but the weather was otherwise good. We compared our images with the digitized POSS II image of the field. Our image is considerably deeper than the POSS II, and so contained many objects not visible there. However, none of these was clearly brighter than the POSS II limiting magnitude, which we can therefore take as the upper limit for any GRB afterglow in this field (approximately R ~ 20, based on flux measurements in our image for marginal detections on the POSS II). One moving source with R ~ 19.5 was detected, presumably a main belt asteroid (the ecliptic latitude of the field is about 7 degrees), which was travelling towards the east northeast at (very roughly) 27 arcseconds per hour. We estimate that this object was in the RXTE error box from about 0400 to 1600 UT, near the center of the RXTE error box around 1000 UT, and near the center of the BeppoSAX error circle (cf. BeppoSAX GRB Mail n. 98/22) around 1600 UT on 980704. Based on the RMS noise in our image and a rough photometric calibration from standard stars in the Mark A field, we estimate a 4 sigma limiting magnitude in a 4" diameter aperture between R=23.0 and R=23.2. We will provide further details and a link to our final image at http://www.noao.edu/noao/grb/980703.html . You are welcome to use this data as a comparison epoch in counterpart searches. We request that we (Ron Downes, Jennifer Christensen, and James Rhoads) be included as authors on any afterglow detection or upper limit that you arrived at using this image. This message can be cited. James Rhoads jrhoads@noao.edu Ron Downes downes@stsci.edu Jennifer Christensen christen@stsci.edu ///////////////////////////////////////////////////////////////////// Circular No. 6966 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions) BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science) URL http://cfa-www.harvard.edu/iau/cbat.html Phone 617-495-7244/7440/7444 (for emergency use only) GRB 980703 A. Levine, E. Morgan, and M. Muno, Massachusetts Institute of Technology (MIT), report on behalf of the RXTE ASM team at MIT and Goddard Space Flight Center: "A gamma-ray burst that occurred on about July 3.182 UT (BATSE trigger 6891) was in the field-of-view of two ASM cameras. The resulting detection yielded a position of R.A. = 23h59m05s, Decl. = +8o33'.6 (equinox 2000.0), with an uncertainty of about 4' radius (90-percent confidence). The burst peak intensity was roughly 1.7 Crab (2-12 keV)." (C) Copyright 1998 CBAT 1998 July 4 (6966) Daniel W. E. Green ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 125 SUBJECT: GRB980703 DATE: 98/07/06 20:11:29 GMT FROM: Kevin Hurley at UCBerkeley/SSL K. Hurley, on behalf of the Ulysses GRB team, and C. Kouveliotou, on behalf of the BATSE team, report: We have triangulated the position of GRB980703 (BATSE 6891). The preliminary annulus is centered at (J2000) R.A.=331.648 degrees, Decl.=-9.065 degrees; its radius is 33.200 +/- 0.156 degrees. The position of the SAX NFI fading X-ray source (BeppoSAX GRB MAIL N. 98/23) is consistent with this annulus. A map may be found at http://ssl.berkeley.edu/ipn3/980703. This message may be cited. ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 126 SUBJECT: GRB 980703: ASM Position & Intensity DATE: 98/07/06 22:01:04 GMT FROM: Don Smith at MIT D. A. Smith, A. M. Levine, and M. Muno on behalf of the RXTE/ASM teams at MIT and NASA/GSFC, report: "The ASM detected emission from GRB 970803 (BATSE trigger #6891) in the crossed fields of view of two of its cameras. Each camera confined the position to a long, thin box at 90% confidence (including systematic & statistical error). The intersection of these error boxes yielded a diamond shaped region with corners at (R.A., Decl.; J2000): (359.873d, +8.653d), (359.742d, +8.573d), (359.664d, +8.459d), and (359.795d, +8.540d). This analysis refines and supercedes the circle of radius 4' reported in IAUC 6966. The burst showed a slow (~40 s) rise to a peak of 1.4+-0.4 Crab (2-12 keV). The intensity began to rise 18 s before the BATSE trigger time of 04:22:45 UTC. At 04:23:07 UTC, the ASM rotated such that the burst moved to the edge of one camera's FOV, and out of the FOV of the second camera. This rotation lasted six seconds. Binning the GRB flux during the second 90-s observation into 9-s bins shows a roughly linear decrease from ~750 mCrab at a rate of ~7 mCrab/s." ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 127 SUBJECT: BeppoSAX NFI observations of GRB 980703 DATE: 98/07/06 22:25:08 GMT FROM: Titus Galama at U.Amsterdam T.J. Galama (U. of Amsterdam), J. van Paradijs (U. of Amsterdam and U. of Alabama in Huntsville), L.A. Antonelli (Astronomical Observatory of Rome and SAX-SDC, Rome), P. Vreeswijk (U. of Amsterdam), C. Kouveliotou (USRA/MSFC), V. Torroni (SAX-SOC Rome), and C. Pastor (Dataspazio, Rome), on behalf of a larger collaboration, report: "We have observed the RXTE/ASM error box of GRB980703 with the BeppoSAX Narrow Field Instruments (NFI) starting about 22 hr after the burst in the period July 4.096-5.084 UT. Preliminary analysis of the data shows a previously unknown X-ray source 1SAX J2359.1+0835 in the LECS and MECS at RA = 23h59m07s, Dec = +08d35'33" (equinox 2000.0), with an error radius of 50" (inside the refined RXTE/ASM error box; GCN/RXTE_ASM note July 6 1998). In the first 8200 sec of the observation the average count rate was (1.14 +- 0.16)x10^-2 cts/s in the combined data of MECS 2 and 3, corresponding to a flux of 7.5 x 10^-13 ergs cm^-2 s^-1. In the last 30000 sec the average count rate was reduced to (7.3 +- 0.7)x10^-3 cts/s corresponding to a flux of 4.8 x 10^-13 ergs cm^-2 s^-1. In addition the field contains the sources 1SAX J2359.9+0834 at RA = 23h59m59s, Dec= +08d34'03" and 1SAX J0000.1+0817 at RA = 00h00m04s Dec=+08d17'14". Both these sources are outside the RXTE/ASM error box, do not show any significant variability and are coincident with ROSAT sources, 1RXS J235959.1+083355 and 1RXS J000007.0+081653, respectively. A new follow-up observation will be performed with the BeppoSAX NFI." This message is citeable. ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 128 SUBJECT: GRB980703: radio source/optical transient DATE: 98/07/06 23:08:34 GMT FROM: Dale A. Frail at NRAO D. A. Frail, (NRAO), J. P. Halpern (Columbia), J. S. Bloom (CIT), S. R. Kulkarni (CIT), S. G. Djorgovski and the BeppoSAX GRB Team report: We observed the entire RXTE error circle of GRB 980703 (IAU Circ. 6966, GCN #126) with the VLA on 1998 July 4.4 UT at a wavelength of 6 cm. A single, weak radio source is detected coincident within the 50 arcsec radius error circle of a fading X-ray source seen by BeppoSAX (GCN #127). The 6-cm flux density is 135 microJy and the rms noise is 26 microJy/beam, with a 1.6 arcsec beam. The approximate position of this source is 23h59m6.67s, +08d35'6.7" (equinox J2000). Further radio observations are planned and to test for any variability. Keck II images obtained by J. B. Oke (DAO) and K. D. Horne (U. St Andrews) on 1998 July 6.60 UT in B and R with 0.5 arcsecond seeing reveals a point-like object at position RA = 23:59:06.69, Decl = +08:35:07.26 (J2000, uncertainty 0.4"), consistent with the position of the radio source. Comparison with images obtained at the Palomar 60in by R. O. Marzke (Carnegie) and D. R. Patton (U. Victoria) on July 4.48 UT show the object to have faded by 0.7 mag in R based on differential photometry with respect to nearby stars. An approximate photometric calibration can be made assuming that a nearby star at RA = 23:59:05.94, Decl = +08:34:57.4 has R = 16.5 as listed in the USNO A1.0 catalog. In this system, the optical transient faded from R = 21.2 on July 4.48 to R = 21.9 on July 6.60. This suggests a power-law decay constant of 0.75 between these dates. A finding chart can be found at http://astro.caltech.edu/~jsb/grb980703_find.ps" This report can be cited. ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 130 SUBJECT: GRB980703 (optical R observations) DATE: 98/07/07 02:39:52 GMT FROM: Alberto Castro-Tirado at LAEFF-INTA GRB 980703. NEW OPTICAL OBSERVATIONS ------------------------------------ M.R. Zapatero Osorio (Instituto de Astrofisica de Canarias, IAC, E-38200 La Laguna, Tenerife, Spain) A. Castro-Tirado (Laboratorio de Astrofisica Espacial y Fisica Fundamental, LAEFF-INTA, Madrid) J. Gorosabel (LAEFF) A. Oscoz, S. Kemp (IAC) F. Frontera, L. Nicastro (on behalf of the BeppoSAX team) Report: Images in the R-band have been obtained at the 0.8-m IAC80 telescope (Teide Observatory) on July 4 and 6 including the BeppoSAX error box for the X-ray source 1SAX J235907+0835 presumably related to GRB980703 which was detected by both BATSE and RXTE. These data reveal an object located at RA = 23h 59m 6.7s DEC = 8d 35' 7'' (+/- 2'', Eq. J2000) which has faded by about 1.5 mag at this wavelength. A preliminary photometric analysis allows us to determine R = 20.6 +/- 0.1 (July 4.123 UT) and 22.1 +/- 0.2 (July 6.137 UT). No other objects varying by more than 0.2 mag are seen down to a limiting magnitude of R = 22.5. A finder chart is available via anonymous ftp to ftp.ll.iac.es (cd publong/grb980703/). ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 131 SUBJECT: GRB 980703 H-band Observations DATE: 98/07/07 04:08:44 GMT FROM: Arne A. Henden at USNO/USRA The U. S. Naval Observatory GRB team (A. A. Henden, F. J. Vrba, C. B. Luginbuhl, H. H. Guetter, B. Canzian, S. E. Levine, J. A. Munn), D. H. Hartmann (Clemson Univ.), and M. C. Jennings (IGPP, UCR visitor) report the H-band detection of the GRB 980703 optical candidate proposed by Frail, et. al. (GCN #128). Observations were obtained with the USNO Flagstaff Station 1.55-m telescope and IRCAM (Rockwell/NICMOS HgCdTe) camera on UT 1998 July 4.458 under photometric conditions. The H-band object was at RA 23:59:06.70, DEC +08:35:07.1 (J2000), consistent with the position by Frail, et. al. Based on a nearby standard, we measure the source to have H = 17.55 +/ 0.20. Using Frail, et. al.'s rough calibration of R = 20.2 for their July 4.48 observation of the optical candidate, implies R-H = 3.6 +/- 0.3 if the USNO-A photometric error is about +/- 0.2 mag. For further information contact Arne A. Henden at aah@nofs.navy.mil or by telephone at (520) 779-5132. This GCN note can be cited. ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 132 SUBJECT: GRB980703 (I band observations) DATE: 98/07/07 13:14:54 GMT FROM: Paul Vreeswijk at U of Amsterdam P.M. Vreeswijk, T.J. Galama, (U. of Amsterdam); Y. Lipkin, E. Leibowitz (Wise Observatory, Tel Aviv University, Israel); C. Lidman, V. Doublier (ESO, Chile); J. van Paradijs (U. of Amsterdam and U. of Alabama in Huntsville); C. Kouveliotou, C. Robinson (NASA-MSFC/USRA) on behalf of a larger collaboration, report: "We obtained I band images with the ESO NTT and the Wise Observatory 1-m telescope that cover the RXTE error circle of GRB980703 (IAU Circ. 6966, GCN #126). We find the following magnitudes for the optical transient proposed by Frail et al. (GCN #128; see also GCN #130 and GCN #131): UT date I telescope July 4.06 20.1 +/- 0.2 Wise 1-m July 4.37 20.6 +/- 0.2 NTT July 5.05 20.9 +/- 0.3 Wise 1-m July 6.44 21.3 +/- 0.2 NTT No other sources in the entire RXTE error circle are found to be variable by more than 0.4 magnitude between the two NTT epochs down to I=22.6. This message is citeable. ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 133 SUBJECT: GRB 980703 DATE: 98/07/07 15:23:11 GMT FROM: Adriano Guarnieri at O.A.di Bologna GRB 980703 C. Bartolini, S. Bernabei, A. Guarnieri, N. Masetti, A. Piccioni and G. Valentini, University of Bologna, F. Frontera (on behalf of the BeppoSAX Team) communicate: "A preliminary analysis of two 30 min CCD frames of the error box of GRB 980703 in R band obtained with the 1.5-m telescope of the Bologna University and the Bologna Astronomical Observatory on 1998 July 5.06 and 6.06 UT shows no variable object within 0.3 mag. The seeing was 2".7 on July 5, 2".3 on July 6; the measurable limiting magnitude was R ~ 21 in both nights. However, in the position indicated in GCN 128 and GCN 130 a faint object is barely visible." This message may be cited. ///////////////////////////////////////////////////////////////////// Circular No. 6967 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions) BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science) URL http://cfa-www.harvard.edu/iau/cbat.html Phone 617-495-7244/7440/7444 (for emergency use only) GRB 980703 M. R. Zapatero Osorio, Instituto de Astrofisica de Canarias (IAC); A. Castro-Tirado and J. Gorosabel, Laboratorio de Astrofisica Espacial y Fisica Fundamental; A. Oscoz and S. Kemp, IAC; and F. Frontera and L. Nicastro, on behalf of the BeppoSAX team, report: "Images in the R band have been obtained at the 0.8-m IAC80 telescope at Teide Observatory on July 4 and 6 of the field including the BeppoSAX error box for the x-ray source 1SAX J2359.1+0835 (cf. GCN 127) that is presumably related to GRB 980703, which was detected by both BATSE and RXTE. These data reveal an object located at R.A. = 23h59m06s.7, Decl. = +8o35'07" (equinox 2000.0; +/- 2"), which has faded by about 1.5 mag at this wavelength. A preliminary photometric analysis yields R = 20.6 +/- 0.1 on July 4.123 UT and 22.1 +/- 0.2 on July 6.137. No other objects varying by > 0.2 mag are seen down to a limiting magnitude of R = 22.5. A finder chart is available via anonymous ftp to ftp.ll.iac.es (cd publong/grb980703/)." (C) Copyright 1998 CBAT 1998 July 7 (6967) Daniel W. E. Green ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 135 SUBJECT: GRB980703: LOTIS observation at early times DATE: 98/07/07 23:25:03 GMT FROM: Hye-Sook Park at LLNL H. S. Park(LLNL), R. A. Porrata(LLNL), and G. G. Williams (Clemson Univ.) report on behalf of the LOTIS collaboration: R. Bionta, E. Ables, L. Ott, E. Parker (LLNL) S. Barthelmy, N. Gehrels, T. Cline (NASA/GSFC) D. Hartmann (Clemson Univ.) C. Kouveliotou, G. Fishman, C. Meegan (NASA/MSFC) D. Band (U.C. San Diego) K. Hurley (U. C. Berkeley) D. Ferguson (Cal State, Hayward) R. Nemiroff (Michigan Technological University) LOTIS obtained images in the field of GRB980703 within 5.03 hours after the burst began (July 3.39 UT). LOTIS resumed its automatic observation program after a recent upgrade incorporating thermoelectric cooling to its four CCD cameras. The upgrade increased the sensitivity from the non-cooled apparatus by at least three magnitudes. LOTIS is capable of responding to GRB events as soon as 10 s after a burst localization by utilizing the BATSE real-time trigger to initiate the fast slewing mount. The telescope has a 17.4 x 17.4 degree wide field-of-view which can cover a large portion of the BATSE error box for real-time triggers. The GRB980703 trigger came at 9:20 PM local time while there was still day light in California. In addition, the reported OT location (GCN #128) was below the horizon when the sky monitoring began that night. Therefore, LOTIS could not cover this event in real-time. However, our all-sky patrol program eventually imaged the GRB980703 field 5 hours after the burst. We also have the sky patrol data from the previous and the following nights. The integration time used for these images was 30 s. We have analyzed the images taken at July 2.39, 2.47, 3.39, 3.47, 4.39, 4.47 and 6.47 UT by comparing them to each other and with the Digital Sky Survey images. No flaring or fading sources were observed at mV~15 with a 5 sigma detection threshold. The LOTIS images of this event can be viewed at http://hubcap.clemson.edu/~ggwilli/LOTIS/GRB980703.html. This message may be cited. ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 136 SUBJECT: GRB980703 Transient Optical Follow-Up DATE: 98/07/08 01:09:23 GMT FROM: Josh Bloom at CIT GRB 980703 Transient Optical Follow-Up J. S. Bloom, S. J. Djorgovski, S. R. Kulkarni (CIT) and D. A. Frail (NRAO) report on behalf of the Caltech-NRAO GRB collaboration: "In the GRB 980703 field (IAUC #6966; GCN #126; GCN #127) of the radio/optical transient discovered by Frail et al. (GCN #128), R-band images (10 min) were obtained at the Palomar 60 inch on July 4,5 by R. O. Marzke (Carnegie) and D. R. Patton (U. Victoria) and at the Keck-II 10-m on LRIS by J. B. Oke (DAO), K. D. Horne (U. St Andrews), and R. Gomer. Photometry, based on an approximate LRIS zero-point (which is uncertain to ~0.2 mag), results in the following derived magnitudes for the transient: Date (UT) Intr Mag OT Rc ----------------------------------- Jul 4.477 P60 21.3 +/- 0.2 Jul 5.482 P60 21.8 +/- 0.3 Jul 6.607 LRIS 22.03 +/- 0.02 (+ zero point uncertainty 0.2mag for all three points) The zero-point may change with expected calibrations but the slope will not. The fading a power-law decline of -0.74, consistent with the I-band fading (-0.84) found from data in Vreeswijk et al. (GCN 132), would make this OT the slowest fading counterpart to a GRB yet. However, since the decay appears somewhat stronger at earlier epochs, we believe that the light may be contaminated by an underlying host. If true, the light curve should show even more flattening. This hypothesis appears corroborated by the fact that the spectral indices derived from the I/R/H-band data are not consistent with a simple fireball model prediction from the decay constant. A summary light curve with all reported I/R-band data may be found at http://astro.caltech.edu/~jsb/grb980703_ltcurve.ps" This message is citeable. ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 137 SUBJECT: GRB980703: Spectrum of the proposed optical counterpart DATE: 98/07/08 01:14:18 GMT FROM: George Djorgovski at Caltech/Palomar GRB 980703: Spectrum of the proposed optical counterpart S. G. Djorgovski, S. R. Kulkarni (Caltech), R. Goodrich (WMKO), D. A. Frail (NRAO), and J. S. Bloom (Caltech), report on behalf of the Caltech GRB collaboration: Spectra of the proposed optical/radio counterpart of GRB 980703 (see GCN Circ. 128) were obtained by R. Goodrich at the Keck-II telescope on July 7.6 UT. The object has a very blue continuum, one strong emission line at approximately 7330 A, and several absorption features in the blue part of the spectrum. If the emission line is identified as [O II] 3727, then the redshift is 0.967. The line cannot be Ly alpha, since there is no sign of intergalactic absorption blueward of it. No broad emission lines are seen at this stage of reductions; the spectrum is thus unlike that of a quasar or a BL Lac, and it is consistent with a young, compact, unobscured starburst. (We note however that the object is unresolved in our images obtained in half-arcsec seeing.) Further analysis of these and other observations is in progress. This note can be cited. [GCN Operator's Note: The originally submitted copy of this circular contained an error in the Subject. This archive copy has been corrected.] ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 139 SUBJECT: GRB 980703: Spectrum of the proposed optical counterpart DATE: 98/07/08 08:03:20 GMT FROM: George Djorgovski at Caltech/Palomar GRB 980703: Spectrum of the proposed optical counterpart S. G. Djorgovski, S. R. Kulkarni (Caltech), R. Goodrich (WMKO), D. A. Frail (NRAO), and J. S. Bloom (Caltech), report on behalf of the Caltech GRB collaboration: Analysis of the spectra of the proposed optical/radio counterpart of GRB 980703 (see GCN Circ. 128, 136, 137) gives the following results: The strong emission line is definitively identified as [O II] 3727 at the redshift z_em = 0.9660 +- 0.0002. It has the equivalent width of 90 +- 2 Angstroms (observed), or 45.7 +- 1 A in the restframe. This is somewhit higher than typical for galaxies at comparable redshifts and magnitudes. After correcting for the as-yet unknown contribution of the GRB afterglow to the continuum flux, these numbers will be higher. The observed line flux is 2.7e-16 erg/cm2/s. There are several absorption features identified as Fe II (2344, 2374, 2383, 2587, and 2600 A) and Mg II (2796 and 2803) lines, with the mean redshift z_abs = 0.9653 +- 0.0007, superposed on an otherwise featureless UV continuum. This too is typical of actively star-forming galaxies at similar redshifts. We also see the 4000-Angstrom break. The observed spectrophotometric magnitude at the epoch of these observations (July 7.6 UT) are: B = 23.3, V = 22.65, and R = 21.9 mag, with the zero-point uncertain by a few tenths of a magnitude, due to the unknown slit losses. The UV continuum blueward of the [O II] line can be described with a power-law F_nu ~ nu**alpha, with alpha = -1.5 +- 0.2, possibly indicative of a modest extinction. Assuming a Friedmann cosmology with H_0 = 65 km/s/Mpc, Omega_0 = 0.2, and Lambda_0 = 0, the luminosity distance at this redshift is 1.9208e28 cm. Our observed [O II] line flux then translates to the restframe line luminosity of 1.25e42 erg/s. Assuming the conversion from Kennicutt (1992), the implied star formation rate is about 63 M_sun/yr, even without any extinction or slit-loss corrections. We thus conclude that the host galaxy of GRB 980703 is a compact starburst object. This gives some support to the models which associate origins of GRBs with massive star formation. Further observations of the object are in progress. This note can be cited. ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 140 SUBJECT: GRB980703 H-band Observations DATE: 98/07/09 00:02:42 GMT FROM: Arne A. Henden at USNO/USRA GRB980703 H-band Observations The U. S. Naval Observatory GRB team (A. A. Henden, F. J. Vrba, C. B. Luginbuhl, H. H. Guetter, B. Canzian, S. E. Levine, J. A. Munn), D. H. Hartmann (Clemson Univ.), and M. C. Jennings (IGPP, UCR visitor) report: Observations were obtained with the USNO Flagstaff Station 1.55-m telescope and IRCAM (Rockwell/NICMOS HgCdTe) camera centered on UT 1998 July 8.459. A total integration time of 40 minutes was achieved, with a limiting magnitude of approximately H = 19.4. No object was detected at the proposed optical transient position reported by Frail, et. al. (GCN #128). For further information contact Arne A. Henden at aah@nofs.navy.mil or by telephone at (520) 779-5132. This GCN note can be cited. ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 141 SUBJECT: GRB980703: Radio transient DATE: 98/07/09 02:10:20 GMT FROM: Dale A. Frail at NRAO D. A. Frail, (NRAO), S. R. Kulkarni (CIT), J. S. Bloom (CIT), S. G. Djorgovski and the BeppoSAX GRB Team report: The radio source identified as a possible afterglow in GCN #128 has brightened considerably and is exhibiting short-timescale variability. During a 3.5 hour VLA run on 1998 July 7 the flux density at 4.86 GHz varied from 1.1 mJy to 0.75 mJy. Variations are also present at 8.46 GHz but they are smaller than those at 4.86 GHz. Similar fluctuations have been seen at early times toward previous radio afterglows and were attributed to interstellar scintillation. Start Date 1.43GHz flux 4.86GHz flux 8.46GHz flux (microJy) (microJy) (microJy) --------------------------------------------------------- Jul. 4.4 UT -- 137 -- Jul. 7.3 UT -- 910 890 Jul. 8.5 UT 120 635 965 --------------------------------------------------------- On 1998 July 8 the spectrum rises with higher frequencies. Such behavior is uncommon in most extragalactic radio sources but it has been seen in the early spectra of previous radio afterglows and attributed to synchrotron self absorption. The radio source appears unpolarized, with a 3-sigma limit on linear polarization at 4.8 GHz and 8.46 GHz of ~8%. An improved position is R.A.=23h59m6.666s, Dec.=+08d35'7.07" (equinox J2000). The position error is approximately +/-0.05". The strong [OII] line emission seen toward GRB980703 (GCN#139) raises the possibility of detecting the host galaxy from radio radiation produced by ongoing star formation (Condon An.Rev.A&A, 30, 575, 1992). For the assumed distance and star formation rate given in GCN#139 we estimate that the host galaxy will be 105, 40 and 25 microJy at 1.43, 4.86 and 8.46 GHz, respectively. Thus the measurement at 1.43 GHz could contain a significant contribution from the host galaxy. We note that a redshift of z=0.966 (GCN #137) along with the average fluxes reported by Galama et al. (GCN #127) implies a lower limit to the X-ray afterglow isotropic energy release of 9.5e49 ergs over the course of the 10.6 hour BeppoSAX NFI pointing. Consistent with this (though it is difficult to translate BATSE count rates to flux and fluence) the total fluence of the GRB is likely ~0.5 -- 1 x 10^-5 erg/cm^2 implying a total isotropic energy release of ~2 -- 5 x 10^52 erg; this falls between the implied energies of GRB 970508 (Metzger et al. Nature 387, 878) and GRB 981214 (Kulkarni et al. Nature, 293, 35). This report may be cited. ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 142 SUBJECT: GRB980703 optical observations DATE: 98/07/09 13:14:21 GMT FROM: Holger Pedersen at Copenhagen U Obs H.Pedersen, Copenhagen University Observatory, H.Korhonen, Nordic Optical Telescope, La Palma, A.O.Jaunsen, Institute for Theoretical Astrophysics, Oslo, I.Ilyin & R.Duemmler, University of Oulu, and F.Frontera, Inst.TeSTRE, Bologna (on behalf of the BeppoSAX team), report: On July 4, 5, 6, and 7 we obtained R band images (600 sec each, seeing 0.75"-1.0" FWHM) of the GRB980703-field using the 2.56-m Nordic Optical Telescope. The field-of-view was 3' x 3' and all images were acquired under good photometric conditions. Images taken during the first three nights were centered on the position initially reported from RXTE by Levine et al. (IAUC 6966) and missed the radio- and optical transient (Frail et al., GCN #128) by ~8 arcsec. Intercomparing these images we found one variable star. Its position is R.A. 23:59:03.7, Dec. +08:33:51.3 (J2000). An approximate R-band zero-point is determined from the USNO catalogue entry U0975_21757527 (a star 15" SW of the OT), which has R=16.5. This gives the following photometry for the new variable: UT Var 1998 July 04.101 R= 21.0 +/- 0.2 04.149 R= 21.1 +/- 0.2 04.194 R= 21.6 +/- 0.2 05.086 R= 21.5 +/- 0.2 05.146 R= 21.2 +/- 0.2 05.195 R= 21.1 +/- 0.2 06.188 R= 21.1 +/- 0.2 An image centered on the RT/OT was taken on July 7. For the OT we find the following R-band magnitude (using the already mentioned standard star): 1998 July 07.163 R= 22.45 +/- 0.2 The errors reflect a conservative estimate of the uncertainty in the determination of the zero-point. Our result is consistent with a power-law decline as reported by Bloom et al. (GCN #136) when comparing to other reported R-band values. Further information can be found on http://vega.uio.no/~ajaunsen/grb980703 This message can be cited. ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 143 SUBJECT: GRB 980703: BATSE Observations DATE: 98/07/09 15:45:26 GMT FROM: R. Marc Kippen at BATSE/UAH/MSFC GRB 980703: BATSE Observations R. M. Kippen (University of Alabama in Huntsville) reports on behalf of the BATSE GRB team: GRB 980703 was detected by BATSE on July 3.182468 UT as trigger number 6891. The event consisted of two pulses, each lasting approximately 100 s, with a total duration of about 400 s. The first pulse had significant sub-structure, whereas the second, weaker, episode was relatively smooth. The burst's peak flux (50-300 keV; integrated over 1 s) and fluence (>20 keV) are 2.42 (-/+ 0.06) photons cmE-2 sE-1 and 4.59 (-/+ 0.42) x 10E-5 erg cmE-2, respectively---ranking it in the top 20% (5%) 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 = 1.05 (-/+ 0.02), which is average for events of this long duration. The BATSE burst location is consistent with those measured by RXTE-ASM (GCN/XTE Notices) and BeppoSAX (GCN 127). 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 message is citeable. ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 144 SUBJECT: GRB980703 optical photometry DATE: 98/07/12 06:03:58 GMT FROM: James Rhoads at KPNO James Rhoads, Ron Downes, and Jennifer Christensen report on behalf of the Kitt Peak Gamma Ray Burst followup team: Using images we obtained on July 4.433 (see GCN Circ. 123), we have measured the R band magnitude of the proposed optical counterpart to GRB 980703 (GCN Circ. 128, 130). We have also measured R band magnitudes of local comparison stars to facilitate photometric calibration of other data. We converted instrumental to standard magnitudes using observations of Landolt standard stars in the fields SA 109 and Mark A. We fitted for the zero point and color term of the photometric transformation. Our standard star fields and the first GRB frame were all taken at essentially the same airmass, so we did not fit for an airmass correction term. All magnitudes for standard stars were measured in 14 arcsecond diameter apertures, to match the procedure of Landolt (1992 AJ 104, 340). Magnitudes for objects in the GRB frame were measured in several apertures and corrected to the equivalent 14 arcsecond aperture magnitude using a curve of growth derived from stars near the GRB. The GRB measurements themselves were based on 2.7 to 4.1 arcsecond diameter apertures. Our results, based on our combined final image (60 minutes integration with the KPNO 0.9m telescope), are summarized below: ID x y d(RA) d(Dec) R dR (1998 July 04.433 UT) OT 896.4 1051.6 0.0 0.0 21.287 0.083 V 1004.6 1119.4 -46.1 -73.6 21.185 0.079 1 891.5 1248.5 -133.9 3.4 18.815 0.015 2 837.5 1195.1 -97.6 40.1 20.132 0.035 3 939.3 1157.7 -72.2 -29.2 19.807 0.026 4 889.9 1077.4 -17.6 4.4 20.392 0.040 5 909.6 1068.6 -11.6 -9.0 16.642 0.015 6 927.0 1064.1 -8.5 -20.8 20.717 0.049 7 887.4 1043.7 5.3 6.1 22.662 0.219 8 919.9 977.6 50.3 -16.0 19.109 0.017 9 857.0 974.5 52.4 26.8 16.492 0.010 10 248.5 1246.8 -132.8 440.5 15.842 0.016 11 748.8 1718.7 -453.7 100.3 16.045 0.004 12 395.5 1731.0 -462.0 340.6 18.174 0.021 13 375.8 1728.4 -460.3 354.0 17.824 0.024 14 1633.4 1604.2 -375.8 -501.1 17.069 0.006 15 1683.8 941.1 75.1 -535.5 17.175 0.005 16 1691.3 1273.4 -150.9 -540.5 16.843 0.012 17 1565.7 1440.8 -264.7 -455.1 15.617 0.005 18 1500.5 1245.5 -131.9 -410.8 17.774 0.015 19 1495.4 448.3 410.2 -407.3 15.787 0.009 20 504.0 529.4 355.0 266.8 15.579 0.010 (x,y) are coordinates in our image. d(RA) and d(Dec) are approximate offsets in arcseconds from the location of the transient, uncorrected for field rotation. R and dR are the measured R band magnitude and the statistical uncertainty in that magnitude (determined using the IRAF tasks "phot" and "mkapfile"). The uncertainty in the photometric zero point is an additional 0.010 magnitudes. The color term was (-0.001 +- 0.018)(V-R) and so will add a small additional uncertainty ( < 0.02 mag for objects of normal color) to the R band magnitudes since we have no color information for most objects in the field. The ID entries are mostly arbitrary numbers. "OT" refers to the optical transient. "V" refers to the variable star reported by Pedersen et al (GCN Circ. 142). None of the objects tabulated above shows photometric variations substantially above 1 sigma random errors in a comparison of our three exposures (each 20 minutes long, beginning on 980704 UT 09:51:16, 10:13:40, and 10:35:40). Individual magnitude measurements for the optical transient and for Pedersen et al's variable are as follows: UT R(OT) dR(OT) R(V) dR(V) 1998 July 04.418 21.168 0.118 21.010 0.098 1998 July 04.433 21.353 0.114 21.114 0.093 1998 July 04.448 21.218 0.101 21.170 0.099 (Here "UT" is the UT of mid-exposure.) Our star number 5 is the USNO catalog entry used by Frail et al (GCN Circ 128) to calibrate their optical photometry. Applying a correction of +0.142 magnitudes to their photometry based on our calibration implies magnitudes for the transient of 21.34 on July 4.48 and 22.04 on July 6.60. This agrees with the zero point of Bloom et al (GCN Circ 135) to much better than their reported accuracy of 0.2 mag. Comparing our measurement to the July 4.458 H band magnitude from Henden et al, we find R-H = 3.75 +- 0.22 . Comparing to the July 4.37 I band measurement of Vreeswijk et al (GCN Circ 132) yields R-I = 0.64 +- 0.22 . In both cases we have corrected the colors for differences between the observation epochs by assuming an achromatic t^(-0.75) decay of the flux. James Rhoads rhoads@noao.edu Ron Downes downes@stsci.edu Jennifer Christensen christen@stsci.edu ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 145 SUBJECT: GRB 980703 (NFI observations) DATE: 98/07/17 16:59:48 GMT FROM: Paul Vreeswijk at U of Amsterdam T.J. Galama, P.M. Vreeswijk (U. of Amsterdam), J. van Paradijs (U. of Amsterdam and U. of Alabama in Huntsville), C. Kouveliotou (USRA/MSFC), L.A. Antonelli (Astronomical Observatory of Rome and SAX-SDC, Rome), V. Torroni (SAX-SOC Rome), and C. Pastor (Dataspazio, Rome), on behalf of a larger collaboration, report: "We have analyzed a second BeppoSAX NFI observation of the RXTE/ASM error box (Smith et al. GCN #126) of GRB 980703 made July 7.779-8.706 UT. Preliminary analysis of the combined MECS 2 and 3 data shows that the variable X-ray source 1SAX J2359.1+0835 (Galama et al. GCN #127), positionally coincident with the radio counterpart (Frail et al. GCN #128) decayed by a factor 5.5 +- 1.5 between July 4 and 8. Assuming a power law light curve we find a decay index of 1.33 +- 0.25" This message is citeable. ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 146 SUBJECT: GRB980703 - BeppoSAX/GRBM detection DATE: 98/07/17 20:30:24 GMT FROM: Filippo Frontera at ITESRE CNR L. Amati, F. Frontera (ITeSRE-CNR, Bologna), E. Costa, M. Feroci, (IAS-CNR, Rome) report: GRB980703 (BATSE trigger 6891) also triggered the BeppoSAX/GRBM units 1 and 4 on July 3 at 04:22:55.3 UT. On the basis of the RXTE/ASM position of the GRB (BACODINE 6891), the GRB incoming direction on the GRBM units is at large angles, 62 degrees and 105 degrees, from units 4 and 1 axis, respectively. The event is visible for 90 s in both units and presents a double peak morphology. The 1 sec peak flux in the 40 - 700 keV energy range is 208 +/- 43 counts/s in unit 1 and 189 +/- 41 counts/s in unit 4. The estimated photon peak flux is 4.7 +/- 0.9 photons cmE-2 sE-1 corresponding to (2.1 +/- 0.4) x 10E-6 erg cmE-2 sE-1. The fluence in the same energy band is (3 +/- 1) x 10E-5 erg cmE-2. This message is citeable. ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 147 SUBJECT: GRB980703, Host galaxy multicolor photometry DATE: 98/07/28 12:43:21 GMT FROM: Vladimir Sokolov at SAO RAS On 1998 July 25.01 UT we obtained B (480 sec), V (420 sec), Rc (300 sec) and Ic (360 sec) band images of the proposed host galaxy of GRB980703 (GCN #137, 139) with the 6-m BTA telescope of SAO-RAS. We reliably detected an extended object - the GRB host galaxy - in all 4 bands. Conditions were photometric with seeing of 1.15 arcsec. Photometric calibration were performed using Landolt's star PG2336+004 and PG2331+055. Photometry of the GRB980703 host galaxy on 4 arcsec diameter aperture gave: B = 23.04+/-0.09 V = 23.02+/-0.10 Rc= 22.43+/-0.08 Ic= 22.10+/-0.18 As already reported (GCN #137), the host galaxy is blue. Images and broadband spectrum of will be posted at http://www.sao.ru/~zhar/home/GRB/980703.html This message can be cited. V. Sokolov (SAO RAS), S. Zharikov (SAO RAS), I. Panthenko (SAI) and the SAX GRB team ///////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 152 SUBJECT: GRB980703 Very Long Baseline Interferometry DATE: 98/08/27 15:49:28 GMT FROM: Greg Taylor at NRAO GRB 980703 Very Long Baseline Interferometry Observations G. B. Taylor, D. A. Frail, A. J. Beasley (NRAO) and S. R. Kulkarni (CIT) report: Using the Very Long Baseline Array (VLBA) we have detected the radio source identified as the afterglow from GRB 980703 (GCN #128). During a 5 hour VLBA run on 1998 Aug 2 the radio source was found to have a flux density of 580 +/- 60 microJy at 8.4 GHz. The source is unresolved by these observations with a size less then 0.3 mas (size < 2 pc given the redshift of 0.9660 reported by Djorgovski et al. in GCN #139). The position of GRB 980703 is R.A.=23h59m06.6661s, Dec.=+08d35'07.09390" (equinox J2000) with an uncertainty of approximately +/-0.0005" in each coordinate. This measurement is consistent with that given by Frail et al. (GCN #141) with errors of +/- 0.05". Given the accuracy of the VLBA position for the afterglow (0.5 mas = 4 pc), it would be of interest to register the afterglow on subarcsecond resolution observations of the host galaxy. Accurate absolute astrometry at other wavebands are encouraged. This report can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 702 SUBJECT: The Hosts of GRB 980703 and GRB 971214 DATE: 00/06/15 01:42:09 GMT FROM: Josh Bloom at CIT The Hosts of GRB 980703 and GRB 971214 J. S. Bloom and S. R. Kulkarni report on behalf of the larger Caltech-NRAO-CARA GRB Collaboration: "The Hubble Space Telescope (HST) has recently observed the hosts of GRB 971214 and GRB 980703 with STIS as part of the Survey of the Host Galaxies of Gamma-Ray Bursts (see S. Holland, B. Thomsen, H. Hjorth et al. GCN #698). Here we present our data reduction of this public data and relate the new STIS images to our previously obtained ground-based data and space-based data. GRB 980703: This remains one of the brightest GRB host galaxies at R~22.8 and the inferred GRB energy release is at the high end of the GRBs energy distribution. The optical astrometry tie from Bloom et al. (1998, ApJL 508, 21) revealed the GRB to be nearly coincident with its host galaxy. The GRB host was observed for a total of 5264 s with the STIS long-pass filter (central wavelength ~ 7230 Ang and FWHM 2720 Ang) beginning 12.42 June 2000 UT. The galaxy is compact (though resolved) and has a low ellipticity (~12%). The effective seeing of the drizzled image is 85 milliarcsec (FWHM) as measured from a bright star in the image and the host has a FWHM diameter of 250 milliarcsec. This is consistent with our report in Bloom et al. of an unresolved source in 0.5 arcsec seeing on July 18 (when the host was thought to dominate the total light of the source). At a redshift of z=0.966 (Djorgovski et al. ApJL 508, 17, 1998), this implies a half-light radius of ~1.1 kpc (assuming H_0 = 65 km/s/Mpc, Omega_0 = 0.3, Omega_lam = 0.7). For photometric zero-pointing of the HST image, we compared two compact objects in common to our deep Keck images from 18 July 1998 in V, R, I. We find the host galaxy has R = 22.8 +/- 0.3 and I = 22.6 +/- 0.3. The error is dominated by the uncertainty in the color correction. These magnitudes are both within 1-sigma of those predicted for the host galaxy in Bloom et al. from the light curve data. We conclude therefore there is no evidence for the presence of a second light source (e.g. a supernova component) in the early time light curve. GRB 971214: At z=3.418, this burst and its host remains the furthest of GRBs with spectroscopically confirmed redshifts and also had an implied energy release at the high end of the GRB energy distribution (Kulkarni et al. 1998, Nature, 393, 35). Using STIS imaging from 13 April 1998 we previously reported (Odewahn et al. 1998 ApJL, 509, 5) the host as compact core with an irregular envelope (half-light radius of 1.3 kpc). Morphologically and in all other observed physical properties the host is rather typical Lyman break galaxy at comparable redshifts. Further, we found a small but significant offset of the GRB from the nucleus of the galaxy. The GRB host was observed for 8599s using STIS clear mode beginning 12.21 Jun 2000 UT. The final image has achieved approximately the same depth as our previous STIS clear imaging. A visual comparison of the two epochs reveals no obvious new or fading component. Our conclusions about the nature of the host and its relation to the GRB remain unchanged from Odewahn et al." Our final reduced images can be obtained in .fits format at http://astro.caltech.edu/~jsb/GRB/Host/ This message may be cited.