//////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 665 SUBJECT: RXTE/ASM and IPN localization of GRB 000508B DATE: 00/05/09 22:03:52 GMT FROM: Don Smith at MIT D. A. Smith and A. M. Levine (MIT), K. Hurley (UCB), and S. Barthelmy (NASA/GSFC) report on behalf of the RXTE/ASM teams at MIT and NASA/GSFC and the IPN collaboration: The RXTE All-Sky Monitor has detected emission we associate with GRB 000508B (BATSE #8098). One camera of the ASM was advantageously placed to observe the field around the BATSE LOCBURST position within 200 seconds of the trigger time (19:10:50.88 UTC). A dramatic rise in intensity occured over approximately 10 s, to a peak of ~1.5 Crab (2-12 keV) at roughly 19:13:44, 75 s into a 90-s ASM observation. Analysis of the position histogram data shows evidence for a previously unknown X-ray source in this and the next sequential observation, after the camera was rotated through six degrees. Localizations of these two detections yields an error box in the shape of a long, thin parallelogram centered at R.A. = 253.498d, Decl. = -20.504d (J2000). This position is confirmed by an annulus derived via the IPN through detections by BATSE and Ulysses. The preliminary annulus is 9.67' in width (3sigma), with a radius of 76.512 deg, centered at R.A. = 309.088, Decl. = 35.112 (J2000.0). This annulus intersects the above diamond at the following points, creating a joint error box with area ~46 sq. arcmin.: 253.700d {16h 54m 48s} -20.432d {-20d 25' 55"} 253.643d {16h 54m 34s} -20.380d {-20d 22' 48"} 253.483d {16h 53m 56s} -20.456d {-20d 27' 22"} 253.5383 {16h 54m 09s} -20.511d {-20d 30' 40"} The time of the increase in the count rate in the first ASM observation is consistent with the estimated time that the best-fit location for the GRB rose from behind the Earth's limb, so we attribute the characteristics of the rise and the lack of detectable emission prior to this time to Earth occultation, not to any intrinsic properties of the GRB source. See the web page at http://xte.mit.edu/grb000508b/ for images and further commentary. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 667 SUBJECT: GRB000508B, BVR field photometry DATE: 00/05/10 17:56:33 GMT FROM: Arne A. Henden at USNO/USRA A. Henden (USRA/USNO) reports on behalf of the USNO GRB team: We have acquired preliminary shallow BVRc all-sky photometry for an 11x11 arcmin field that covers the error box for GRB000508B with the USNOFS 1.0-m telescope on one photometric night. Stars brighter than V=12 are saturated and should be used with care. We have placed the photometric data on our anonymous ftp site: ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb000508b.dat The current photometry has a potential external zero-point error of about two percent. The astrometry in this file is based on linear plate solutions with respect to USNO-A2.0. The internal errors are less than 100mas. Further calibration of this field will be performed if an optical afterglow is identified. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 668 SUBJECT: GRB000508B, optical photometry DATE: 00/05/10 22:57:10 GMT FROM: Krzysztof Z. Stanek at CfA K. Z. Stanek (CfA), P. M. Garnavich (Notre Dame), P. J. Groot, S. Jha (CfA) and M. Hicks (JPL) report: We have observed most of the RXTE/ASM-IPN error-box of GRB 000508B (GCN 665) using the FLWO 1.2-meter telescope on Mt. Hopkins and the KPNO 2.1m telescope. The center of the GRB 000508B error-box is located at Galactic coordinates (l,b)=(0.48 deg,14.38 deg), and the Schlegel et al. (1998) Galactic reddening toward this direction is E(B-V)=0.51 (A_V=1.7 mag). Due to the proximity to the Galactic plane the stellar field is fairly dense. At KPNO we obtained four 600 sec R-band images, the first two at UT May 10 07:30 and the second two at UT May 10 11:33. At FLWO we obtained two 600 sec R-band images, first one at UT May 10 06:39 and the second one at UT May 10 09:14. In addition, at FLWO we have obtained UBVI images for the field. Using DAOPHOT-II (Stetson 1992) on the FLWO 1.2-meter R-band image we detect about 5,000 objects with R<22.5 in 11x11 arcmin field. Visual comparison with the POSS-II red plate reveals no obvious ``new'' objects. Employing the image subtraction code ISIS-2 (Alard 1999) between the two epochs taken at each telescope reveals four possible variable objects located in the error-box, with the following coordinates and magnitudes from Henden et al. (GCN 667): V1) RA=253.58616 DEC=-20.41683 V=16.75 V2) RA=253.54913 DEC=-20.46479 V=17.33 V3) RA=253.53600 DEC=-20.43531 V=17.72 V4) RA=253.60865 DEC=-20.42111 V=18.24 All of these objects are easily identified on the POSS-II plate, so most likely NONE of these objects is the optical counterpart to GRB 000508B. Further observations are planned at FLWO. This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 670 SUBJECT: Re: GRB000508B : Optical observations DATE: 00/05/16 21:54:56 GMT FROM: Brian Lindgren Jensen at U.of Copenhagen GRB 000508B: Optical observations B. L. Jensen, H. Pedersen, J. Hjorth (U. of Copenhagen), J. P. U. Fynbo (U. of Aarhus/ESO), J. Gorosabel, N. Lund (DSRI,Copenhagen), H. Kjeldsen, F. Grundahl (U. of Aarhus), C. Zurita, J. Casares (IAC,Tenerife), C. Sanchez-Fernandez and A.J. Castro-Tirado (LAEFF, Madrid) report on behalf of a larger European GRB collaboration: "We have obtained images of the RXTE/IPN error box reported by Smith et al. (GCN #665) with the 2.56-m Nordic Optical Telescope (NOT+ALFOSC) on La Palma, and the 1.54-m Danish Telescope (DK-1.54m+DFOSC) at La Silla, as follows: Telescope Date Filter/Exp t. FWHM NOT 2000 May 10.14 UT (t+32h); I:5x300s; FWHM=0.8" DK-1.54m 2000 May 10.17 UT (t+33h); R:3x420s; FWHM=1.5" DK-1.54m 2000 May 10.38 UT (t+38h); R:3x420s; FWHM=1.5" DK-1.54m 2000 May 12.25 UT (t+83h); R:4x420s; FWHM=1.3" We have visually compared the combined May 10 2520s R-band image with red POSS-II exposure. The three sets of May 10 images have been compared internally, both visually and using automated routines based on DAOPHOT II/ALLSTAR PSF-photometry. Additionally, we have compared the combined May 10 and May 12 R-band images, visually and through automated routines. We do not, in any of the comparisons, find any significantly variable objects down to a 3-sigma mag limit of R~22.5. We do not find significant variability in the objects noted by Stanek et al. (GCN #668). An image of the error-box is posted at http://www.astro.ku.dk/~brian_j/grb/grb000508B "