Please note that this running archive of the Circulars contains Circulars for BOTH 000301A and 000301C. The scripts that automatically update this archive file are not flexible enough to recognize the 'A' vs 'C' differences (when folded in with all the format variations people use in the subject-lines of their submissions). My apologies for the inconvenince for this rare dual burst situation. Please note that the convention for letter suffixing GRBs is upper case letters (not that people would be all that fooled by lower case). //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 567 SUBJECT: GRB000301A [IPN Position] DATE: 00/03/02 01:29:50 GMT FROM: Kevin Hurley at UCBerkeley/SSL K. Hurley, S. Barthelmy, T. Cline, E. Mazets, and M. Feroci, report: Ulysses, BATSE, NEAR, Konus, and the BeppoSAX GRBM observed this burst (BATSE #8005). Its Earth-crossing time was 02:33:55 UT. Its duration was ~6 s, and its 25-100 keV fluence was ~2 x 10^-6 erg/cm2. Preliminary triangulation gives an ~35 sq. arcmin. error box whose center and corners (3 sigma) are at: RA(2000) DEC(2000) 23 h 39 m 27.12 s 75 o 47 ' 12.86 " (CENTER) 23 h 38 m 13.41 s 75 o 53 ' 21.64 " (CORNER) 23 h 39 m 55.29 s 75 o 48 ' 43.78 " (CORNER) 23 h 38 m 59.05 s 75 o 45 ' 41.71 " (CORNER) 23 h 40 m 40.21 s 75 o 40 ' 59.86 " (CORNER) This error box can be refined considerably. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 568 SUBJECT: GRB000301C: RXTE/ASM and IPN localizations DATE: 00/03/02 19:25:31 GMT FROM: Don Smith at MIT GRB000301C D. A. Smith (MIT) reports on behalf of the ASM team at MIT and NASA/GSFC, and K. Hurley (UCB) and T. Cline (NASA/GSFC) report on behalf of the Ulysses and NEAR GRB teams: The ASM has detected a GRB at 03/01/2000 09:51:37 (UTC). The burst showed a single peak with a simple fast-rise, slow-decay structure. The three ASM energy channels showed the strongest response in the 5-12 keV band, reaching a peak flux of 3.7+-0.7 Crab (5-12 keV) in 1-s time bins. The event lasted approximately 10 seconds. The event was detected by a single ASM SSC, yielding an error box (90% confidence, including systematic and statistical error) 4.2 degrees long and 8.7 arcminutes wide, centered at R.A. = 16h 13m 14s and Decl. = 28o 37' 59.2" (J2000.0), with a position angle of -117.1 degrees. Ulysses and NEAR observed this burst. Preliminary triangulation gives an annulus 5' in full-width (3 sigma), centered at R.A. = 20h 34m 7.56s and Decl. = 20o 32' 19.62s (J2000.0), with a central radius of 57.520 degrees. This annulus may be refined. This annulus intersects the ASM error box at near-right angles to create a composite localization of a parallelogram of area ~50 sq. arcmin with the following corners (J2000.0): R.A. Decl. 16h 20m 30s +29o 30' 14.3" 16h 20m 08s +29o 27' 50.4" 16h 20m 13s +29o 19' 40.8" 16h 20m 35s +29o 22' 00.0" Figures and charts can be found at http://gx339.mit.edu/grb000301c/ This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 569 SUBJECT: Radio observations of the error box of GRB000301A DATE: 00/03/03 00:08:23 GMT FROM: Evert Rol at U.Amsterdam E. Rol (Univ. of Amsterdam), R. Strom (NFRA, UoA), P. Vreeswijk (UoA), C. Kouveliotou (USRA, NASA/MSFC), L. Kaper (UoA) report, on behalf of a larger collaboration: "We have observed the IPN error box of the GRB000301A (GCN #567) at 4.9 GHz with the Westerbork Synthesis Radio Telescope. We obtained a 6 hour observation, centered at March 2.64 UT. Within the error box, we detect only one source, at a flux level of 0.37 +- 0.055 mJy. The position of the source is (J2000): RA 23:39:47 Decl 75:46:15 with a conservative error of 2 arcseconds. At this point, we do not claim that this is the radio counterpart to GRB000301A. We are currently trying to find a catalogue for this wavelength to compare with. Observations of the error box will continue with the WSRT." This message may be cited //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 570 SUBJECT: GRB 000301C: Optical Candidate DATE: 00/03/03 08:05:32 GMT FROM: Brian Lindgren Jensen at U.of Copenhagen J. P. U. Fynbo (U. Of Aarhus), B. L. Jensen, J. Hjorth, H. Pedersen (U. of Copenhagen) and J. Gorosabel (DSRI, Copenhagen) on behalf of a larger European GRB Consortium report: "Using the ALFOSC on the 2.5m Nordic Optical Telescope, we have obtained I, R, B, and U-band imaging of the field of GRB 000301C (Smith et al., GCN #568) on 2000 March 3.14-3.28 UT. Comparing with DSS-2 plates we find an object which is notoriously absent from DSS-2 (red) and (blue). The coordinates of this object are: RA(J2000) : 16 20 18.6 Dec(J2000) : +29 26 36 (with an uncertainty of about 1") This object is detected in individual exposures of 900s, in all four colors. Preliminary USNO-A1.0-based magnitude is: R~20.3 +- 0.5 . The object appears bluer than most GRB OTs observed so far. Sections of the images will be made available at: http://www.astro.ku.dk/~brian_j/grb/grb000301c along with a DSS-2 finding chart." [GCN OPS NOTE (03Mar00 14:15 UT): The URL in the original posting of this circular had an error. This archived copy of the circular has been corrected.] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 571 SUBJECT: GRB000301C DATE: 00/03/03 09:54:49 GMT FROM: Adriano Guarnieri at O.A.di Bologna S.Bernabei, S.Marinoni, C.Bartolini, A.Guarnieri, A.Piccioni, Astronomical Observatory and Astronomy Department, Bologna University, and N.Masetti, ITeSRE-CNR, Bologna report: "A preliminary quick inspection of one single R image of the field of GRB 000301C (RXTE/ASM and IPN localization, Smith, Hurley and Cline, GCN 568) taken on March 3, starting at 04:27 UT (EEV-CCD,1000 sec exposure) with the 152 cm telescope of Loiano shows an object located at RA=16h 20m 18.5s, D=29`26'35" (Eq. 2000), which is not present on the Digital Sky Survey. It is roughly 1 mag brighter than the POSS limit and it is coincident with the object detected by Fynbo et al., GCN 570. Only new observation can decide if this object is the OT connected with GRB 000301C. This message may be cited //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 572 SUBJECT: GRB000301C, near-infrared observations DATE: 00/03/03 15:44:25 GMT FROM: Sylvio Klose at TLS Tautenburg B. Stecklum, S. Klose (Thueringer Landessternwarte Tautenburg), O. Fischer (Universitaets-Sternwarte Jena), C. Bailer-Jones, U. Thiele, A. Aguirre (Max-Planck-Institut fuer Astronomie, Heidelberg), F. J. Vrba, A. A. Henden, C. B. Luginbuhl, B. Canzian, S. E. Levine, H. H. Guetter, J. A. Munn (U.S. Naval Observatory, Flagstaff), D. H. Hartmann (Clemson University, Clemson), A. Castro-Tirado (LAEFF-INTA, Madrid, and IAA-CSIC, Granada), J. Greiner (AIP Potsdam), and J. Gorosabel (LAEFF-INTA, Madrid, and University of Amsterdam) report: The error box of the burst GRB 000301c reported by Smith et al. (GCN #568) was imaged with the Calar Alto 3.5-m telescope on March 3, 4:41 UT - 5:38 UT using the near-infrared camera Omega Cass. The frames were taken in the course of a project whose goal is to measure the degree of linear polarization of GRB afterglows. The limiting magnitude of the K'-band image is about K'=19 after adding all images taken at different position angles of the wire-grid polarizer. The potential optical transient reported by Fynbo et al. (GCN #570) is clearly detected. Based on the assumption that the B-R colour index of the star USNO 125_07686794 is representative for its spectral type, a preliminary estimate of the K'-band magnitude of the potential afterglow of 17.4 was derived. The image is posted on the Tautenburg Web page at http://www.tls-tautenburg.de/research/grb000301c.html. This message is quotable. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 573 SUBJECT: GRB000301C, optical observations DATE: 00/03/03 19:17:14 GMT FROM: Peter Garnavich at Center for Astrophysics P. Garnavich (Notre Dame), P. Barmby, S. Jha, K. Stanek (CfA) report: We imaged the ASM error box (GCN 568) of GRB000301C with the FLWO 1.2m telescope and R-band filter on 2000 Mar. 3.51 (UT) and detect the optical candidate reported by Fynbo et al. (GCN 570). Using Landolt standards taken during the night, we find a preliminary magnitude of R=20.28 +\- 0.05 mag. This is very close to the Fynbo et al. estimate taken some 7 hours earlier. However, given the quoted errors for the two measurements there is room for some variability over this time. Further observations are needed to confirm this source as the GRB afterglow. We have calibrated the following stars in R to use as comparisons: star Offset East Offset North R A -6" -1" 18.05 +/- 0.05 B -4 -89 18.48 C 70 -55 18.62 D -7 62 17.04 Offsets are in arcsec from the GRB candidate with positive offsets east and north. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 574 SUBJECT: GRB 000301A, Radio Observations DATE: 00/03/03 22:59:39 GMT FROM: Dale A. Frail at NRAO D. A. Frail and G. B. Taylor (NRAO) report: "We imaged the IPN error box of GRB000301A (GCN #567) with the VLA at frequencies of 4.86 GHz and 8.46 GHz, starting on March 3.86 UT. The radio source reported by Rol et al. (GCN #569) is visible. We obtain an improved position of (J2000) r.a.= 23 39 47.51 (+/-0.05), dec. = +75 46 14.5 (+/-0.2). The VLA flux density at 4.86 GHz is 408+/-61 microJy, consistent with that measured at WSRT 30 hrs earlier. The 8.46 GHz flux density is 432+/-68 microJy, and indicates a flat spectrum. A search of the NRAO All Sky Survey (NVSS; Condon et al. 1998, AJ, 115, 1693) shows that the VLA observed in this direction at a frequency of 1.4 GHz on 1993 October 20. At the position of the radio source there is a weak (2.5-sigma) NVSS source with a flux density of 1.1+/-0.45 milliJy. The absence of significant variability, the flat spectrum and the possible identification of a NVSS source at this position, makes it unlikely that the radio source is related to GRB 000301A." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 575 SUBJECT: GRB000301C: optical observations DATE: 00/03/03 23:09:35 GMT FROM: Christian Veillet at CFHT GRB000301c optical observations The candidate for the optical transient (OT) associated with the gamma ray burst GRB000301c has been observed in imaging mode with MOS on the 3.6-m CFH Telescope in the course of the French GRB follow-up program at CFHT (M. Boer, CESR, C. Veillet, CFHT). Relative photometry in B and R with respect to the reference star A (GCN573) is as following: delta B = 1.29 +/- 0.05 2000 March 3.50 (UTC) delta R = 2.19 +/- 0.05 2000 March 3.51 (UTC) The R magnitude inferred from star A magnitude determination in GCN573 is 20.24 +/-.07, in good agreement with the GCN 573 value of R = 20.28 +\- 0.05 measured at the same epoch. B and R images can be found at http://www.cfht.hawaii.edu/~veillet/grb.html B calibrations will be made tonight if no multicolor photometry is made available for reference stars in the field. D. Elbaz and H. Flores are acknowledged for their help in these observations. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 576 SUBJECT: GRB 000301C: OT confirmed DATE: 00/03/03 23:21:41 GMT FROM: Brian Lindgren Jensen at U.of Copenhagen J. P. U. Fynbo (U. of Aarhus), B. L. Jensen, J. Hjorth, H. Pedersen (U. of Copenhagen), J. Gorosabel (DSRI, Copenhagen) on behalf of a large European GRB Consortium report: "In response to Garnevich et al., (GCN #573), we have carried out photometry of stars A-D of GCN #573 and of the OT proposed by Fynbo et al., (GCN #570). This photometry has been performed on our combined 2000, March 3, 3x900s NOT R-band image of the GRB-field. Using the stars A-D of Garnevich et al. as reference, we derive an R-band magnitude for the OT at UT_mean = March 3.17 of R = 19.94+-0.04. Hence, the candidate OT is fading and we thus propose it as being the optical counterpart to GRB 000301C. The implied power-law decay index from this magnitude and the magnitude measured by Garnevich et al. is rather steep : -1.8 (with this rate, a magnitude of R:20.8 is predicted for March 4.17 UT)." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 577 SUBJECT: GRB000301C, near-infrared observations (JHK' photometry) DATE: 00/03/03 23:39:15 GMT FROM: Naoto Kobayashi at SUBARU, NAOJ Naoto Kobayashi (Subaru Telescope, National Astronomical Observatory of Japan), Miwa Goto, Hiroshi Terada (Kyoto University), Alan T. Tokunaga (Institute for Astronomy, University of Hawaii), on behalf of SUBARU Telescope team and SUBARU IRCS team On 3 March, 12:48 UT - 13:54 UT, we observed the candidate optical counterpart to GRB 000301C that was reported by Fynbo et al. (GCN Circular #570). We used the Subaru 8m Telescope on Mauna kea with a new instrument IRCS (Infrared Camera and Spectrograph for the Subaru Telescope) during its first engineering run. Near-infrared J,H,K' filters were used. The candidate optical transient (OT) was clearly detected in all three bands. We have performed preliminary photometry with 2-arcsecond aperture using Persson standards taken during the night. The resultant magnitude of the candidate OT was K'=17.6+-0.1 mag. For reference, the magnitude of the near-by star, USNO 125_07686794, was estimated at K'=16.0+-0.05 mag. Comparing to the estimated K' magnitude of 17.4 (at 4:41 UT - 5:38 UT) reported by Stecklum et al (GCN Circular #572), our photometry may suggest that the brightness decreased by roughly 0.2 mag during 8 hours. However, given the possible systematic errors for the two estimates (e.g., photometric system is different), further observations are necessary to confirm this OT candidate as the GRB afterglow. This message is quotable in publications. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 578 SUBJECT: GRB 000301C, Optical Observation DATE: 00/03/04 01:33:27 GMT FROM: Jules Halpern at Columbia U. J. P. Halpern, N. Mirabal, & S. Lawrence (Columbia U.) report on behalf of the MDM Observatory GRB follow-up team: "We imaged the location of GRB 000301C as determined by the intersection of the RXTE All-Sky Monitor error box and the Ulysses/NEAR annulus (Smith, Hurley, & Cline, GCN #568) in the R band on March 3.51 UT using the MDM 1.3m telescope. The optical transient found by Fynbo et al. (GCN #570,576) is measured at R = 20.24 +/- 0.05, referenced to the comparison stars of Garnavich et al. (GCN #573). This is consistent with measurements by Garnavich et al. and Veillet (GCN #575) that were obtained contemporaneously. The implied power-law decay index is still rather uncertain. Using our magnitude and that measured by Fynbo et al. (GCN #576), we find alpha = -1.56 +/- 0.30. This predicts R = 20.90 +/- 0.18 on March 4.51 UT. We measure the position of the optical transient to be (J2000) RA 16:20:18.550, Dec +29:26:35.96 relative to 30 USNO-A2.0 stars having a dispersion of 0".31 in radius. CCD images are posted at http://www.astro.bio2.edu/grb/ This message may be cited." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 579 SUBJECT: GRB 000301C R-band observation DATE: 00/03/04 02:51:37 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia Alberto J. Castro-Tirado, IAA-CSIC (Granada) Holger Bock, Landesternwarte (Heidelberg) Jochen Greiner, AIP (Potsdam) Sylvio Klose, TLS (Tautenburg) Jose Maria Castro Ceron, ROA (San Fernando) Felipe Hoyo, CAHA (Almeria) Javier Gorosabel, DSRI (Copenhagen) on behalf of a larger European GRB collaboration report: "We have just obtained a 15-minute R-band exposure centred at the GRB 000301C error box (Smith et al. GCN#568) starting at 01:15 UT on 4 March 2000 with the 1.23 m telescope at the German-Spanish Calar Alto Observatory (CAHA). Using the stars A-D of Garnavich et al. (GCN #573) we derive R = 20.46 +/- 0.09 for the optical counterpart reported by Fynbo et al. (GCN #570). When combining this value with the measurements by Fynbo et al. (GCN #576) and Halpern et al. (GCN #578) the power-law decline exponent becomes alpha = -1.27 +/- 0.20." This message is quotable. [GCN OPS NOTE (03Mar00): The Felipe Hoyo author was added to the archive copy.] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 580 SUBJECT: GRB000301C 250 GHz detection DATE: 00/03/04 13:50:36 GMT FROM: Frank Bertoldi at MPIFR/Bonn Frank Bertoldi (MPIfR Bonn) reports: The likely afterglow of GRB 000301C (Smith et al., GCN 568) was detected at 250 GHz (1.2 mm) with the 37 channel Max-Planck Millimeter Bolometer (MAMBO) array (80 GHz bandwidth, 10.7 arcsec HPBW) at the IRAM 30 m telescope on Pico Veleta, at the position reported by Fynbo et al. (GCN 570) and Halpern et al. (GCN 578). The object was observed on 4 March 2000 from UTC 7 to 11:30, in standard on-off mode, under good weather conditions (stable atmosphere with opacity slowly rising from 0.21 to 0.26), and good pointing accuracy (<2"). The total on plus off target integration time was 7800 seconds. A source is clearly detected with flux density f(250 GHz) = 1.9 +- 0.3 mJy We hope to continue monitoring its flux. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 581 SUBJECT: GRB000301C, optical observations DATE: 00/03/04 21:16:26 GMT FROM: Peter Garnavich at Center for Astrophysics P. Garnavich (Notre Dame), P. Barmby, S. Jha, K. Stanek (CfA) report: We again imaged the candidate optical counterpart of GRB000301C with the FLWO 1.2m telescope and R-band filter on 2000 Mar. 4.38 (UT) and estimated its magnitude based on the calibration stars given in GCN 573. We find R=20.56 +/- 0.05 which suggests a rather slow decline rate. Using the magnitude estimates from Veillet (GCN 575), Fynbo et al. (GCN 576), Halpern et al. (GCN 578) and Castro-Tirado et al. (GCN 579) we find the data best fit a single power-law index of -1.07+\-0.13 . However, using data taken since Mar 3.5 (UT) gives an even more shallow slope of -0.8 +\-0.2 and suggests a possible flattening of the decay rate. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 582 SUBJECT: GRB 000301C, Optical Observation DATE: 00/03/04 21:31:36 GMT FROM: Jules Halpern at Columbia U. J. P. Halpern, N. Mirabal, & S. Lawrence (Columbia U.) report on behalf of the MDM Observatory GRB follow-up team: "We reobserved GRB 000301C in the R band on March 4.50 UT using the MDM 1.3m telescope, measuring R = 20.61 +/- 0.04, referenced to the comparison stars of Garnavich et al. (GCN #573). The power-law decay derived from this and previous measurements (GCNs #575,576,578,579) is slower than previously indicated. We find alpha = -1.07 +/- 0.09. This predicts R = 20.95 on March 5.50 UT. The decay curve and a new CCD image are posted at http://www.astro.bio2.edu/grb/ This message may be cited." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 583 SUBJECT: GRB 000301C, UBVRI field photometry DATE: 00/03/05 00:04:18 GMT FROM: Arne A. Henden at USNO/USRA A. Henden (USRA/USNO) reports on behalf of the USNO GRB team: We have acquired preliminary UBVRcIc all-sky photometry for the field of GRB000301C with the USNOFS 1.0-m telescope on one photometric night. This 11x11arcmin field covers the IPN error box, contains the proposed optical counterpart, and extends fainter than R=20. The file includes the Garnavich, et. al. (GCN 573) R-band comparison stars with similar magnitudes within errors. We have placed the photometric data on our anonymous ftp site: ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb000301c.dat This file will be updated as soon as the weather improves. The current photometry has a potential external zero-point error of about two percent. Negative errors are Poisson only; positive errors are standard deviation of two or more measures. The astrometry in this file is based on linear plate solutions with respect to USNO-A2.0. The internal errors are less than 100mas. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 584 SUBJECT: GRB000301C, Optical Spectroscopy DATE: 00/03/05 02:01:45 GMT FROM: Mike Eracleous at PSU, Astro.Dept. M. Eracleous (Penn State), M. Shetrone (Mc Donald Obs.), S. Sigurdsson, P. Meszaros (Penn State), J. C. Wheeler, and L. Wang (U. Texas) on behalf of the Hobby-Eberly telescope GRB follow-up team: "We obtained a spectrum of GRB 000301C with the Low-Resolution Spectrograph on the Hobby-Eberly Telescope on March 4.410. The spectrum, which was taken under non-ideal weather and seeing conditions, covers the range 4100-8000 A. We detect no obvious emission or absorption features. The flux density per unit frequency interval (f-nu) appears to increase monotonically toward the red." This message may be quoted. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 585 SUBJECT: GRB 000301C, Optical Color DATE: 00/03/05 04:12:03 GMT FROM: Jules Halpern at Columbia U. J. P. Halpern, N. Mirabal, & S. Lawrence (Columbia U.) report on behalf of the MDM Observatory GRB follow-up team: "We also obtained B-band images of GRB 000301C on March 4.52 UT using the MDM 1.3m telescope. By employing the Henden et al. (GCN #583) photometry of the comparison stars A and D of Garnavich et al. (GCN #573), we measure B = 21.41 +/- 0.04, and we determine that B-R = 0.77 +/- 0.06 at this time. Correcting for the Schlegel et al. (1998) Galactic extinction at this location, A_B = 0.23 and A_R = 0.14, we find an intrinsic B-R = 0.68 +/- 0.06, which corresponds to a spectral slope beta = -0.87 +/- 0.14. This value, together with the temporal decay slope alpha = -1.07 +/- 0.09 (GCN #581,582), is consistent within the errors with the canonical alpha = (3/2)beta behavior of a spherical afterglow in an uniformly dense medium. Little intrinsic extinction is required to explain the color. The B-band image is posted at http://www.astro.bio2.edu/grb/ This message may be cited." [GCN OPS NOTE (05Mar00 04:25 UT): This archived copy has the typo "B-R = 0.68 +/- 0.6," fixed to correctly read "B-R = 0.68 +/- 0.06,".] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 586 SUBJECT: GRB 000301C near-IR observations DATE: 00/03/05 05:48:25 GMT FROM: James Rhoads at STScI James Rhoads and Andy Fruchter (STScI) report: We observed the proposed afterglow of GRB 000301c with the NASA IRTF + NSFCam in K' band (2.1 microns) on March 4.640, and in J band (1.25 microns) on March 4.652. The data were photometrically calibrated by observations of UKIRT faint standard 27. Seeing was approximately 0.85" in K' and 0.95" in J. We find K'=17.65 +- 0.04 and J=19.10 +- 0.05 (statistical error only) for the candidate afterglow. Aperture photometry was performed using a 0.9" (3 pixel) radius aperture, corrected to an effective aperture of 2.7" radius using aperture corrections derived from the brighter star 5.7" W and 1" S of the proposed OT. For reference, this star had magnitudes K'=15.96 +- 0.02 and J=16.63 +- 0.01. No correction was made for atmospheric extinction or color terms; however, these are expected to be small. (The standard was observed at airmass 1.09, and the GRB field at airmass 1.02.) We detect a faint object, quite possibly a galaxy, approximately 2" N and 1" E of the candidate OT; this could be the host galaxy if the OT is real. This object has approximate magnitudes K'=19.8, J=20.8. This K' flux shows no significant decline from the earlier reported observations (Stecklum et al, GCNC 572; Kobayashi et al, GCNC 577), while it would be expected to decay by 0.44 magnitudes from Kobayashi's data point for a t^-1.0 power law. This relative constancy of the near-IR flux, despite optical fading, is difficult to reconcile with GRB afterglow models, especially if it persists for more than a day. We note that many classes of variable objects (other than afterglows) show stronger variability at bluer wavelengths. The weak or nonexistent variability in the K' filter is therefore a cause for concern, and we urge continued followup at both optical and IR wavelengths. We thank the staff of the IRTF for help with these service observations. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 587 SUBJECT: GRB000301C, near-infrared observations (JHK' imaging) DATE: 00/03/05 14:33:36 GMT FROM: Naoto Kobayashi at SUBARU, NAOJ Naoto Kobayashi (Subaru Telescope, National Astronomical Observatory of Japan), Miwa Goto, Hiroshi Terada (Kyoto University), Alan T. Tokunaga (Institute for Astronomy, University of Hawaii), on behalf of SUBARU Telescope team and SUBARU IRCS team We report an improved near-infrared photometry of the proposed OT for GRB000301C in our J,H,K' images taken with IRCS (InfraRed Camera and Spectrograph) on the SUBARU Telescope on March 3.55 UT. Photometry was performed on co-added image (18-min total exposure time) while quick photometry of one K' frame (2-min exposure) was reported in GCNC #577. Seeing was approximately 0.45" in K' and 0.50" in J/H throughout the observation. The OT magnitudes were determined with about 0.01 mag statistical accuracy in all bands. Relative magnitudes of the OT to the near-by bright star (5.7" W and 1" S) were derived and compared to the results by Rhoads & Fruchter (GCN #586) to examine possible near-infrared decay of the OT. The results are as follows: relative magnitude(OT-Star) Reference J H K' UT 3.55 March 2.27 2.18 1.56 this work UT 4.64 March 2.47 ---- 1.69 GCNC #586 decay/day 0.20 ---- 0.13 Since we expect the uncertainty of relative photometry is quite small (e.g., 0.01 mag), these results suggest that the OT is actually fading in the near-infrared. The near-infrared decay rate is smaller compared to the R-band decay rate (~0.4-mag/day) of the same period. The slightly larger decay in J compared to K' may suggest that the decay rate is smaller in longer wavelengths. The possible host galaxy reported by Rhoads & Fruchter (GCN #586) is also detected in our images. It looks slightly extended (FWHM=0".6-0".7) in our K'-images of 0".45 seeing, which suggests that this source is actually a galaxy. This message is quotable in publications. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 588 SUBJECT: GRB000301C optical observations DATE: 00/03/05 17:27:05 GMT FROM: Christian Veillet at CFHT GRB000301c optical observations The candidate for the optical transient (OT) associated with the gamma ray burst GRB000301c has been observed in imaging mode with MOS on the 3.6-m CFH Telescope in the course of the French GRB follow-up program at CFHT (M. Boer, CESR, C. Veillet, CFHT). An R image has been taken with a good seeing (better then 0.8 arcsecond). Relative photometry with respect to the reference star A (GCN573) using GCN583 photometry is as following R = 20.86 +/- 0.04 2000 March 5.63 (UTC) It is significantly different from the prediction based on a temporal decay slope alpha = -1.07 +/- 0.09 (GCB581) and seems to confirm the flattening of the decay rate suggested in the same circular. More data would be welcome though! The relative photometry in B and R published in GCN575 becomes, using GCN583 data: B = 21.11 +/- 0.04 2000 March 3.50 (UTC) R = 20.27 +/- 0.04 2000 March 3.51 (UTC) and B-R = 0.84 +/- 0.06 at the same date, to be compared with 0.77 +/- 0.06 on March 4.52 (GCN585). D. Elbaz and H. Flores are acknowledged for their help in these observations. This message may be cited. ************************************************************ Dr. Christian Veillet, CFHT Senior Resident Astronomer Phone: (808) 885-3161 http://www.cfht.hawaii.edu/~veillet/ ************************************************************ //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 589 SUBJECT: GRB000301C, Radio observations DATE: 00/03/05 18:21:09 GMT FROM: Edo Berger at Caltech E. Berger (Caltech) and D. A. Frail (NRAO) report on behalf of a larger collaboration: "Beginning on March 5.67 UT we used the VLA to observe a field centered at the position of the optical transient reported by J. P. U. Fynbo, et al, and S.Bernabei, et al (GCN 570 and 571). We detect a 300 microJy radio source at 8.46 GHz, located at the position of the optical transient. Absolute flux calibration is not yet available. Continued observations at a broad range of frequencies are underway." This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 590 SUBJECT: GRB000301C, Radio observations DATE: 00/03/05 18:25:27 GMT FROM: Edo Berger at Caltech E. Berger (Caltech) and D. A. Frail (NRAO) report on behalf of a larger collaboration: "Beginning on March 5.67 UT we used the VLA to observe a field centered at the position of the optical transient reported by J. P. U. Fynbo, et al, and S.Bernabei, et al (GCN 570 and 571). We detect a 300 microJy radio source at 8.46 GHz, located at the position of the optical transient. Absolute flux calibration is not yet available. Continued observations at a broad range of frequencies are underway." This message may be cited. [GCN OPS NOTE (05Mar00 18:30 UT): This Circular (#590) is a duplicate of Circular 589. The duplication is a result of a failure in the initial submission and the nearly simultaneous second submission with a change in the submittor's entry in the distribution list to allow the submitor to use his new address. Please use Circular 589 for all references.] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 591 SUBJECT: Optical observations of GRB000301C DATE: 00/03/05 18:45:28 GMT FROM: SG Bhargavi at Indian Inst of Astrophysics S.G.Bhargavi and R.Cowsik (Indian Institute of Astrophysics,Bangalore, India 560034) report: We imaged the field of GRB000301c (GCN #568) using the 2.34m Vainu Bappu Telescope at Kavalur, India from March 2nd to March 4th, 2000 with clear sky conditions. date UT filter & total exposure ----------------------------------------------- 2, Mar 22.46 -23.8 UT B(20min), R(45min) 3, Mar 22.08 -23.96 UT R(70min),I(45min) 4, Mar 21.23 -23.966 UT R(60min),I(30min),B(50min) ------------------------------------------------------ Since the internet is down I am unable to view the images reported in various GCN circulars. However, referring to the offset positions of reference stars by Garnavich et al (GCN #573) and a FAX of DSS picture the object proposed to be the counterpart of GRB000301c (GCN #570,576) is identified in all our images. The data reduction is in progress. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 592 SUBJECT: GRB000301C - Host galaxy not detected in R (?) DATE: 00/03/05 20:12:30 GMT FROM: Christian Veillet at CFHT The candidate for the optical transient (OT) associated with the gamma ray burst GRB000301c has been observed in imaging mode with MOS on the 3.6-m CFH Telescope in the course of the French GRB follow-up program at CFHT (M. Boer, CESR, C. Veillet, CFHT). The R image mentioned in GCN588 has been examined for a possible detection of the galaxy observed in the near IR (GCN586-587). Nothing is detected at the reported position (1"E 2"N). The detection limit in this area of the field is at R~25. The OT itself has no significant elongation compared to nearby stars. "Something" is detected at -1"E 2"N though. It was not visible on the previous R image taken on March 3.5 due to a much poorer seeing (~1.5"). Its magnitude (if real) is 24.7 +/- .3 . Should I add that more deep imaging is needed?... Image available at http://www.cfht.hawaii.edu/~veillet/grb.html D. Elbaz and H. Flores are acknowledged for their help in these observations. This message may be cited. ************************************************************ Dr. Christian Veillet, CFHT Senior Resident Astronomer Phone: (808) 885-3161 http://www.cfht.hawaii.edu/~veillet/ ************************************************************ //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 593 SUBJECT: GRB000301C OT candidate optical observations DATE: 00/03/05 22:05:02 GMT FROM: Elia Leibowitz at Wise Obs, Tel Aviv U A. Gal-Yam, E. Ofek, D. Maoz and E.M. Leibowitz, Wise Observatory, Tel Aviv University, Israel, report: Using the Wise Observatory 1-m telescope and the observatory new SiTe CCD camera, we obtained on March 4 two 900 sec and one 1800 sec exposures through an R filter, and one 1800 sec V exposure, of the GRB000301C OT candidate. The mean UT of the 3 R exposures is March 4.0799. The weighted mean R magnitude, measured relative to stars A-D of Garnavich et al. (GCN 573), is 20.573 +/- .06. The UT of the V image is March 4.1121, and the OT-ref* magnitude differences, with respect to stars A,B,C and D, are, respectively (+/-0.12): 2.356, 1.635, 1.342 and 3.683. This message is quotable in publications. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 594 SUBJECT: GRB 000301C: K' Observations DATE: 00/03/06 06:53:23 GMT FROM: Andrew S. Fruchter at STScI A. Fruchter and J. Rhoads (STScI) report: The field of the presumed afterglow of GRB 000301C was re-oberved with the NASA IRTF and NSFCam in the K' band (2.1) microns on UT March 5.61. We use our calibration from GCN 586 and comparison to the brighter star ~6" to the W for photometry. We find that the presumed OT is now fainter than the reference star by 2.04 mag, so that K'=18.00. The formal error from photon statistics is 0.05 mag. The total error on the relative magnitude might be as large as 0.07 mag, and the total error on the absolute magnitude as large as 0.10 mag. Relative photometry of five other sources in the field shows no variation with respect to the bright star greater than 1.5 sigma. The transient has therefore declined by 0.35 +- 0.08 mag in K' between UT 4.64 March and 5.61 March. This is in contrast with a decline of 0.13 +/- 0.05 mags between 3.55 and 4.64 March (GCN 586 and 587). The slow-down in the rate of decline in the R band over the same time span (Veillet GCN 588) suggests a remarkable decoupling of the optical and near-infrared behavior of this transient. The candidate host is 1" W (not E as incorrectly reported in GCN 586) and 2"N of the OT. It is the same object reported by Veillet in GCN 592. This galaxy has colors of order R-K'=5, J-K'=1; however, the color must be considered highly uncertain until better comparison of the optical and infrared images can be made. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 595 SUBJECT: GRB 000301C Optical Observations DATE: 00/03/06 08:01:20 GMT FROM: Vijay Mohan at U.P.State Observatory Nainital V. Mohan, A.K. Pandey, S.B. Pandey, R. Sagar, UPSO, Nainital and Alberto J. Castro-Tirado, IAA-CSIC (Granada) report on behalf of a larger European GRB collaboration : "We have observed the field of GRB 000301C on March 3 and March 5 using the 1-metre telescope of U.P. State Observatory and 2k x 2k CCD. The R magnitudes calibrated using stars A and D of Garnavich et al. (GCN #573) come out to be as follows: Mar 3.93 UT 20.53 +/- 0.05 Mar 5.96 UT 21.18 +/- 0.05 Using all R band observations reported so far the value of alpha comes out to be 1.02 while excluding the R magnitude reported in #GCN 588, alpha comes out to be 1.12 +/- 0.1. " //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 596 SUBJECT: GRB 000301c: K' observations DATE: 00/03/07 04:23:14 GMT FROM: James Rhoads at STScI James Rhoads and Andy Fruchter (STScI) report: We observed the candidate counterpart of GRB 000301c for a third time with the NASA-IRTF + NSFCam on March 6.595. The magnitude of the transient relative to the reference star 6" west has decayed to +2.60 +- 0.12, giving K'=18.56 +- 0.12 (statistical error only). This is a decay of 0.56 magnitudes since our preceding observation (on March 5.61 UT), and so the decay of the 2.1 micron flux continues to accelerate. The K' band light curve is a considerably worse fit to any power law than the R band light curve. This unusual behavior warrants closer investigation, and further followup at all wavelengths (especially the near-IR) is encouraged. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 597 SUBJECT: GRB 000301C, Optical Observation DATE: 00/03/07 13:31:02 GMT FROM: Sergej Zharikov at OAN IA UNAM GRB 000301C, Optical Observation R. Mujica, V. Chavushyan, INAOE; S. Zharikov, G. Tovmassian, OAN IA UNAM, Mexico, report: We observed GRB 000301C optical counterpart in the R band on March 4.458 UT using the 2.1m telescope of the "Guillermo Haro" Observatory in Cananea, Sonora, Mexico with the Landessternwarte Faint Object Spectrograph and Camera (LFOSC). Using reference stars A-D of Garnevich et al. (GCN 573), we derive R-band magnitude of R = 20.54+\-0.06 for the OT at 2000 March 4.458 UT. This magnitude is in a good agreement with other observations that were obtained approximately at the same time (GCN #581, 582, 593). This message may be cited. [GCN OPS NOTE: This submission was delayed several hours because of a change in the submitor's address.] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 598 SUBJECT: GRB000301c - R photometry and nearby faint source confirmation DATE: 00/03/07 22:57:59 GMT FROM: Christian Veillet at CFHT The candidate for the optical transient (OT) associated with the gamma ray burst GRB000301c has been observed in imaging mode with MOS on the 3.6-m CFH Telescope in the course of the French GRB follow-up program at CFHT (M. Boer, CESR, C. Veillet, CFHT). The OT has the following magnitude, using star A (GCN573) photometry (GCN583): R = 21.70 +/- 0.07 2000 March 7.65 (UTC) This value does not fit very well with the the R magnitudes published in the previous GCN, in particular by Mohan(595), if we assume a power law common to all observations. In fact, the best fit of the data published so far is obtained with a linear magnitude decay of 0.32 +/- 0.02 mg/day... The acceleration in the decay in K (GCN596) seems also to be seen in R. More data, as well as a careful reanalysis of the existing images, are clearly needed! The faint source found on March 5 (GCN592), recognized in GCN594 as identical to the one detected in IR at NASA IRTF, is definitely there also on the March 7 image. A composite of the two images is available at http://www.cfht.hawaii.edu/~veillet/grb.html . Its R magnitude is measured as 24.3 +/- 0.3 , to be refined with further analysis. S. Lilly is acknowledged for his help in this observation. This message may be cited. ************************************************************ Dr. Christian Veillet, CFHT Senior Resident Astronomer Phone: (808) 885-3161 http://www.cfht.hawaii.edu/~veillet/ ************************************************************ //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 599 SUBJECT: GRB000301C, optical R-band observations DATE: 00/03/08 15:20:28 GMT FROM: Nicola Masetti at ITeSRE,CNR,Bologna S. Bernabei (Astron. Obs., Bologna), C. Bartolini, L. Di Fabrizio, A. Guarnieri, A. Piccioni (Dip. Astronomia, Univ. of Bologna), and N. Masetti (ITeSRE/CNR, Bologna) report: "We have imaged the proposed optical counterpart (GCN #570) of GRB000301C (GCN #568) on March 3, 4, 6, 7 and 8, 2000, in the R band with the 152 cm Loiano telescope (plus EEV CCD) of the Observatory of Bologna. Using the R magnitudes of the four comparison stars quoted by Garnavich et al. (GCN #574) we obtain the following figures: Date exptime seeing R mag. --------------------------------------------------- Mar. 3.191 1000 s 2".0 20.11 +- 0.05 Mar. 4.178 2200 s 3".0 20.22 +- 0.2 Mar. 6.145 1800 s 1".7 21.60 +- 0.2 Mar. 7.135 1800 s 1".7 21.63 +- 0.15 Mar. 8.157 1800 s 1".5 21.63 +- 0.1 The R magnitudes of the first two days, albeit the measurement of March 4 was acquired under bad weather conditions (thick cirrus), seem to confirm the deviations of the decay of this object from the typical power-law trend seen in GRB afterglows, as already pointed out by other authors (see GCN #581 and #586). The present data also agree with the result reported by Boer & Veillet (GCN #598) and indicate a "standstill" of the optical candidate. Thus, either we are already seeing the host galaxy of this GRB (in this case it would not be the object at 1" W, 2" N of the transient; see GCN #592, #594, #598), or the optical transient associated to GRB000301C has a definitely peculiar behaviour, or this is not the optical counterpart of GRB000301C. We also obtained B and I images which are now entering the reduction stage. This message is quotable.". //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 600 SUBJECT: GRB 000301c: K' observations DATE: 00/03/09 15:02:12 GMT FROM: James Rhoads at STScI James Rhoads and Andy Fruchter (STScI) report: We observed the candidate counterpart of GRB 000301c again on March 8.590 in the K' filter using the NASA IRTF + NSFCam. The magnitude of the transient relative to the reference star 6" west has decayed further to +3.32 +- 0.09, giving K'=19.28 +- 0.09 (statistical error only). This is a decay of 0.72 magnitudes in the two days since our preceding observation (on March 6.595 UT). This continued decay is in marked contrast to the "standstill" of the optical flux reported by Bernabei et al (GCNC 599), and leads us to believe that the source most likely is the transient counterpart of GRB 000301c despite its erratic behavior. The near-IR flux showed a comparable "standstill" behavior earlier (GCNC 572, 577, 586, 587) and then entered a steeper decline. The total decay to date in K' has been 1.76 magnitudes, and during the 72 hours preceding this observation the K' flux decayed approximately as t**(-2.2). Extrapolation of this object's light curve from earlier data appears fraught with difficulty. Further observation is therefore strongly urged at all wavelengths. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 602 SUBJECT: GRB 000301C: HST/STIS CCD Imaging of the field DATE: 00/03/09 23:15:11 GMT FROM: Andrew S. Fruchter at STScI A. Fruchter (STScI), A. Smette (GSFC), T. Gull (GSFC), R. Gibbons, H. Ferguson, L. Petro, K. Sahu (STScI) for a larger HST GRB Collaboration. We have imaged the field of GRB 000301C with HST using the STIS CCD 50LP (open) mode. The observations were performed on the 6.22 March 2000 UT with a total exposure time of 1440s. We easily detect the transient believed to be associated with GRB 000301C (Fynbo et al GCN 570, Bernabei et al. GCN 571). We find a source magnitude of R=21.5 +/- 0.15 or V=21.9 +/- 0.15, where the error is dominated by the wide bandpass of the STIS detector and the uncertainty in the color of the transient (Halpern et al. GCN 585). The OT is relatively well represented by a point source: any underlying galaxy would have to have R >~ 24, or be unusually compact for it to avoid detection in our data. We therefore believe that the apparent flattening of the light curve in the R band reported by many observers is not due to an underlying host galaxy but rather is intrinsic to transient. The red galaxy to the north east of the transient reported by Rhoads and Fruchter (GCN 586) is detected in our image; however, there is no apparent bridge of emission between these two objects. We therefore now believe it is quite likely that they are unrelated. The image is available at http://www.stsci.edu/~fruchter/GRB/000301C //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 603 SUBJECT: GRB 000301C: HST/STIS-PRISM NUV-MAMA spectroscopy DATE: 00/03/09 23:39:49 GMT FROM: Alain Smette at NASA-GSFC A. Smette (NASA/GSFC,NOAO,FNRS), A. Fruchter (STScI), T. Gull (NASA/GSFC), K. Sahu, H. Ferguson, L. Petro (STScI), and D. Lindler (ACC) report for the HST GRB collaboration and the Danish discovery team: The proposed optical counterpart of GRB 000301C (Fynbo et al GCN 570, Bernabei et al. GCN 571) was observed with HST/STIS-PRISM mode during four orbits totaling 8000s from 6.26 to 6.49 March 2000 (UT). The MAMA NUV detector with sensitivity from 1175A to 3400A was used. Data reductions were performed with STIS GTO IDL tools using prelaunch spectral dispersion constants and on-orbit sensitivity calibrations. A spectrum is detected with a peak S/N ~ 10 beginning at ~2650A, extending to ~3250A with an average flux of ~4.6+/-0.2E-18 ergs/cm2/sec. The emission is 2.2 pixels FWHM (0.055 arcseconds) along the slit indicating a point source with no obvious diffuse extension. The spectrum appears relatively flat (in f_lambda) from 3200A to 2750A and then presents a sharp drop at about 2700A. Within the present calibration uncertainties, the observed spectrum is well fitted by a model using the power-law spectral index determined by Halpern et al. (GCN 585), the observed V = 21.9 magnitude from the STIS CCD images obtained on 6.2 March (Fruchter et al. GCN 602) a moderate amount of extinction in the restframe of the OT, and a Lyman limit break at ~2700A. Assuming the Lyman break is caused by neutral hydrogen in the host galaxy, the redshift of GRB 000301C is 1.95 +/- 0.1 where the large error bar is due almost entirely to the present uncertainty in the STIS UV prism calibration. We expect a more accurate calibration shortly. We encourage ground-based observations at a predicted Lyman alpha wavelength of 3585+-120A. H alpha would be at ~1.95 microns. The spectrum is available at http://www.stsci.edu/~fruchter/GRB/000301C [GCNOPS NOTE (09 Mar 00 23:50 UT): The last line of this circular listing the URL for the spectrum as was added.] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 604 SUBJECT: GRB 000301C, Optical Observation DATE: 00/03/10 02:52:21 GMT FROM: Jules Halpern at Columbia U. J. P. Halpern & J. Kemp (Columbia U.) report on behalf of the MDM Observatory GRB follow-up team: "We reobserved GRB 000301C in the R band on March 9.52 UT using the MDM 1.3m telescope, measuring R = 22.28 +/- 0.09 referenced to the comparison stars of Garnavich et al. (GCN #573). Seeing was 1."4. If we restrict our attention to those GCN reported magnitudes that have error bars less than or equal to 0.1 mag, then the light curve is reasonably well described by a power-law decay of alpha = -0.90 +/- 0.04 until 4 days after the burst, followed by a power-law decay of alpha = -1.93 +/- 0.12. An updated decay curve and a new CCD image are posted at http://www.astro.bio2.edu/grb/000301Ca This message may be cited." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 605 SUBJECT: GRB 000301C: A Precise Redshift Determination DATE: 00/03/10 09:41:17 GMT FROM: George Djorgovski at Caltech/Palomar GRB 000301C: A Precise Redshift Determination S. M. Castro, A. Diercks, S. G. Djorgovski, S. R. Kulkarni, T. J. Galama, J. S. Bloom, F. A. Harrison (Caltech), and D. A. Frail (NRAO), report on behalf of the Caltech-CARA-NRAO GRB collaboration: Moderately high resolution spectra (FWHM ~ 1 Ang) of the optical transient (OT) associted with GRB 000301C (Fynbo et al., GCN 570) were obtained on UT 2000 March 04, by W. L. W. Sargent, A. Boksenberg, and M. Rauch, using the ESI Echelle spectrograph on the Keck-II 10-m telescope on Mauna Kea, Hawaii. Two exposures of 1800 sec each were obtained, over an effective wavelength range from ~3800 Ang, to ~10800 Ang. The OT continuum is well detected. No strong absorption systems were found in the spectrum. However, a number of possible weak lines are present. We identify a subset of them with the following lines: Fe II 2260, 2344, 2374, 2382, 2586, and 2600, and Mg II 2796 and 2803; and a less reliable set of O I 1302, C II 1334, Si IV 1393, Si II 1526, C IV 1550, Fe II 1608, Al II 1670. The weighted mean absorption redshift of this 16-line system is z = 2.0335 +- 0.0003. This is fully consistent with the redshift estimate from the HST spectroscopy, z = 1.95 +- 0.1 (Smette et al., GCN 603), based on the ostensible Lyman break. We thus consider our redshift determination to be secure, and interpret it as the redshift of the GRB host galaxy, with no intervening foreground systems. The restframe equivalent widths of the absorption lines are in the range of interstellar medium in the host galaxy. Assuming z = 2.0335, and a simple Friedmann cosmology with H_0 = 65 km/s/Mpc, Omega_0 = 0.2, and Lambda_0 = 0, the luminosity distance is D_L = 5.11e28 cm, the distance modulus is (m-M) = 49.1 mag, and the relativistic (1+z)**4 surface brightness dimming factor is 4.8 mag. This may account for the lack of a detection of the host galaxy in the HST images (Fruchter et al., GCN 602). This note can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 606 SUBJECT: GRB 000301C: Optical Spectrum and Redshift DATE: 00/03/10 13:52:14 GMT FROM: Lifan Wang at U.Texas Feng, M., Wang, L., and Wheeler, J. C., University of Texas at Austin report: We obtained a low resolution (resolving power about 70) spectrum of GRB 000301c with the 2.7 meter telescope at McDonald Observatory on 2000 March 3.47. The total exposure time was 3900 seconds with wavelength coverage from 318 nm to 589 nm. The low S/N (about 2-4) spectrum can be fitted with a power law of spectral index beta = -1.1 witn no obvious breaks after correcting for interstellar extinction assuming R = 3.1, E(B-V) = 0.05 (cf GCN 585). The flux level is around 2.5E-17 ergs/cm2/sec/A. This puts any possible Lyman break at wavelengths shorter than 318 nm. The object is thus at a redshift lower than 2.5. This is consistent with the report by Smette et al. (GCN 603). The spectrum may reveal two absorption features at 336.0 nm and 352.2 nm. If identified with Lyman alpha, the redshifts of these features are 1.76 and 1.89. The data also show another absorption feature at 367.1 nm, but with even lower confidence level. This feature yields a redshift of 2.02 if identified with Lyman alpha. Another possible feature is an absorption at 405.8 nm which might be identified with C II 133.5 nm at a redshift of 2.04. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 607 SUBJECT: GRB 000301C: Optical Spectrum and Redshift DATE: 00/03/10 13:58:33 GMT FROM: Lifan Wang at U.Texas The resolution in my previous email was wrong. The corrected version is given below. Feng, M., Wang, L., and Wheeler, J. C., University of Texas at Austin report: We obtained a low resolution (resolving power about 500) spectrum of GRB 000301c with the 2.7 meter telescope at McDonald Observatory on 2000 March 3.47. The total exposure time was 3900 seconds with wavelength coverage from 318 nm to 589 nm. The low S/N (about 2-4) spectrum can be fitted with a power law of spectral index beta = -1.1 witn no obvious breaks after correcting for interstellar extinction assuming R = 3.1, E(B-V) = 0.05 (cf GCN 585). The flux level is around 2.5E-17 ergs/cm2/sec/A. This puts any possible Lyman break at wavelengths shorter than 318 nm. The object is thus at a redshift lower than 2.5. This is consistent with the report by Smette et al. (GCN 603). The spectrum may reveal two absorption features at 336.0 nm and 352.2 nm. If identified with Lyman alpha, the redshifts of these features are 1.76 and 1.89. The data also show another absorption feature at 367.1 nm, but with even lower confidence level. This feature yields a redshift of 2.02 if identified with Lyman alpha. Another possible feature is an absorption at 405.8 nm which might be identified with C II 133.5 nm at a redshift of 2.04. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 610 SUBJECT: GRB000301C - R photometry DATE: 00/03/11 19:13:11 GMT FROM: Christian Veillet at CFHT The candidate for the optical transient (OT) associated with the gamma ray burst GRB000301C has been observed in imaging mode with OSIS on the 3.6-m CFH Telescope in the course of the French GRB follow-up program at CFHT (M. Boer, CESR, C. Veillet, CFHT). The OT has the following magnitude, using star A (GCN573) photometry (GCN583): R = 23.02 +/- 0.10 2000 March 11.63 (UTC) The power-law decay observed lately (after 4 days after the burst, as described by Halpern et al. GCN604) can now be described with alpha = 2.1 +/- 0.1. Note that alpha is dependent on the choice of the start of the "new decay" and on the inclusion or not of some of the measurements from Bernabei et al.(GCN599). In case you read the introduction too fast, the instrument used is no longer MOS, but OSIS. The detector is the same though (STIS2). The new image is available at http://www.cfht.hawaii.edu/~veillet/grb.html . M. Pakkul is acknowledged for his help in this observation. This message may be cited. ************************************************************ Dr. Christian Veillet, CFHT Senior Resident Astronomer Phone: (808) 885-3161 http://www.cfht.hawaii.edu/~veillet/ ************************************************************ //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 611 SUBJECT: GRB000301C - B and R photometry DATE: 00/03/14 23:57:10 GMT FROM: Christian Veillet at CFHT The candidate for the optical transient (OT) associated with the gamma ray burst GRB000301C has been observed in imaging mode with OSIS on the 3.6-m CFH Telescope in the course of the French GRB follow-up program at CFHT (M. Boer, CESR, C. Veillet, CFHT). The OT has the following magnitude, using star A (GCN573) photometry (GCN583): R = 23.82 +/- 0.10 2000 March 14.60 (UTC) (two 30mn exposures) B = 24.83 +/- 0.12 2000 March 14.60 (UTC) (one 55mn exposure) The power-law decay described with alpha = -2.1 +/- 0.1 (GCN610) is not sufficient to account properly for the last four measurements (GCN598, 604, 610 and this GCN), which are better fit with alpha = -2.7 +/- 0.1 . The first phase of the decay would cover the first four days after the burst, with alpha = -0.91 +/- 0.08. A graph with these two consecutive power laws, as well at the new images, are at http://www.cfht.hawaii.edu/~veillet/grb.html As for the apparent B-R, the error bars are large enough to make it close to the value determined using MOS on March 3.5 (0.86 +/- 0.06) or the one published by Halpern (0.77 +/- 0.06 in GCN585 a week ago). As the GRB is still steadily decaying, it's unlikely to have the underlying galaxy contributing significantly to the measured flux. This galaxy should probably be fainter than R = 24.5, confirming the comment by Fruchter et al. (GCN602) from HST imaging data (R >~ 24). A 20 micron camera will be installed on the telescope today for 10 nights. No new data on this GRB will be acquired during this period. Aloha from Hawaii! I. Gable is acknowledged for his help in this observation. This message may be cited. ************************************************************ Dr. Christian Veillet, CFHT Senior Resident Astronomer Phone: (808) 885-3161 http://www.cfht.hawaii.edu/~veillet/ ************************************************************ //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 623 SUBJECT: GRB000301C - R magnitude lower limit DATE: 00/04/05 01:33:30 GMT FROM: Christian Veillet at CFHT The candidate for the optical transient (OT) associated with the gamma ray burst GRB000301C has been observed using the CFH12K CCD mosaic camera at the prime focus of the 3.6-m CFH Telescope in the course of the French GRB follow-up program at CFHT (M. Boer, CESR, C. Veillet, CFHT). Three 12 mn exposures with moderate seeing (image quality around 0.9") have been coadded. There is nothing visible at the location of the OT. The nearby galaxy (thought to be the host for some time before the HST observations) has a magnitude of R= 24.5 +-0.1, confirming the previous determinations (GCN592 - GCN598). The faintest objects detected in the neighborhood are at around R=26. We can infer the following lower limit: R > 26.0 on 2000 April 4.6 It is compatible with the alpha = -2.7 power law decay given in GCN611, and not with alpha = -2.1 given earlier, which would lead to R~25.6 at the same epoch. Further imaging is planned if the seeing gets better. Jean-Charles Cuillandre is acknowledged for his help in this observation. This message may be cited. ************************************************************ Dr. Christian Veillet, CFHT Senior Resident Astronomer Phone: (808) 885-3161 http://www.cfht.hawaii.edu/~veillet/ ************************************************************ //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 624 SUBJECT: GRB000301C - Addendum to GCN 623 DATE: 00/04/05 01:58:59 GMT FROM: Christian Veillet at CFHT A composite image of the GRB field without anything at the location of the OT is posted at http://www.cfht.hawaii.edu/~veillet/grb.html An obvious consequence of the magnitude limit given in GCN623 is that the host galaxy is fainter than R=26 ... I should have included that in the previous GCN. Sorry! ************************************************************ Dr. Christian Veillet, CFHT Senior Resident Astronomer Phone: (808) 885-3161 http://www.cfht.hawaii.edu/~veillet/ ************************************************************ //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 627 SUBJECT: GRB 000301C: Late-Time HST/STIS CCD Imaging of the field DATE: 00/04/10 01:38:58 GMT FROM: Andrew S. Fruchter at STScI A. Fruchter (STScI), A. Smette (GSFC), T. Gull (GSFC), H. Ferguson, L. Petro, J. Rhoads, and K. Sahu (STScI) for a larger HST GRB Collaboration: We have re-imaged the field of GRB 000301C with HST using the STIS CCD in both 50CCD (open) and LP (long-pass) mode. The observations were centered about 3.9 April 2000 UT with total exposure times of 2280s in both filters. We detect a bright source on a fainter extended object at the position of the optical transient (OT). The position of the peak of emission from the object agrees with that of the OT on previous HST images taken on 6 March 2000 (see GCN 602) to better than 0."01, based on astrometry relative to other objects visible in both HST images. We believe therefore we are observing continued emission from the OT of GRB 000301c, as well as from its host galaxy. One cannot give a precise magnitude for the OT without knowing a priori the surface brightness profile of the host. However, what we consider the best point source subtraction implies an OT magnitude of R=26.9; in any case, the point source is no brighter than R=26.7. The total magnitude of the OT plus host is 26.5 +/- 0.15 on 3.9 April 2000. Although no upper limit to the magnitude of the OT can truly be given without knowledge of the host, we note that R=26.9 is within 0.1 mag of the value predicted for this date by the fit to earlier R band data given in Rhoads and Fruchter (astro-ph/0004057). This provides some further confidence that our best estimate of the OT strength is not far off. If this value is used for the magnitude of the OT, then the host galaxy has a magnitude R = 27.8 +/- 0.25. The STIS filter set only gives limited color information, however, our observations agree well with the spectral index of -0.9 reported by Halperin (GCN 585). A change to a spectral index of -3, as has been seen in the late time spectra of some other GRBs, would most likely have been detected. The HST images of GRB 000301c are available at: http://www.stsci.edu/~fruchter/GRB/000301C //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 630 SUBJECT: GRB000301c results DATE: 00/04/10 09:28:01 GMT FROM: SG Bhargavi at Indian Inst of Astrophysics SG Bhargavi and R Cowsik (IIA, Bangalore) report the results of optical data on GRB000301c observed between Mar 2-4, 2000 (GCN-591): Mar 2.9618UT R=20.02 \pm 0.03, B-R=0.97 \pm 0.2 Mar 4.9087UT R=20.58 \pm 0.05, B-R=0.734 \pm 0.14 Mar 3.9976UT R=20.49 \pm 0.10 The R-band magnitudes from VBT along with other values from various GCN circulars have been plotted. The numbers marked on the graph correspond to the serial number of entries in the table. Two solid lines are fit by \alpha = -0.722 +/- 0.05 and \alpha=-2.9 +/- 0.017, which seems to be a better fit than the dotted lines where the power law index is \alpha = -0.97+/- 0.07 and /alpha= -1.99 +/- 0.19 respectively. (Mid-expoure time for B-R is 2.975UT and 4.9375UT respectively; this combined with B-R values in GCN \#588, 585 shows that B-R is falling as -0.25mag/day) The table as well as the graph (post-script file) are available at our anonymous FTP server: narmada.iiap.ernet.in change directory to bhargavi/GRB000301c/ This message may be cited. ------------------------------------------ PS: this mail has bounced back many times..giving my last trail [GCN OPS NOTE: The reference to the bounced email problems was discussing a problem with the e-mail servers and network at the India end, and not with the processing at the GCN end.] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 701 SUBJECT: GRB 000301C: Further Late-Time HST/STIS observations DATE: 00/06/13 23:06:57 GMT FROM: Andrew S. Fruchter at STScI A. Fruchter, M. Metzger and L. Petro report for a larger collaboration: The field of GRB 000301c was reobserved by the Hubble Space Telescope using the STIS camera in open (50CCD) mode on the 19 April 2000. The optical transient is still visible with an R magnitude of 27.9 +/- 0.15, where the error is dominated by uncertainties in the calibration of STIS and the need to assume the shape of the spectrum across the wide bandpass of the detector. The OT therefore is continuing the steep decline reported in the previous GCN and remains consistent with the late-time power-law reported in Rhoads and Fruchter (astro-ph/0004057). We find no evidence of a host galaxy underlying the GRB, to a magnitude of at least 28.5. We believe the apparently extended emission reported in our previous GCN is due to substantial, and larger than expected, variability in the PSF. Although we have not yet been able to fully reproduce the emission about the point source in our 3 April 2000 observations, we suspect this is due to very rapid variability in the PSF. Further analysis of our data has now shown residuals in PSF subtraction comparable in magnitude to that seen in the 3 April observation, even when using PSFs from the same star taken in quick succession. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 766 SUBJECT: GRB000301C, UBVI optical observations DATE: 00/08/03 04:01:59 GMT FROM: Krzysztof Z. Stanek at CfA K. Z. Stanek (CfA), P. Garnavich (Notre Dame), P. Barmby, S. Jha (CfA) report: Given the microlensing interpretation of GRB000301C (Garnavich, Loeb & Stanek 2000b: astro-ph/0008049) and the importance of any additional data for this burst, we reduced several additional frames of the optical counterpart of GRB000301C obtained with the FLWO 1.2m telescope and UBVI filters on 2000 Mar. 4 (UT). Our measurements are based on the comparison star A of Garnavich et al. (2000a: GCN 573), calibrated by Henden (2000: GCN 583) (magnitudes given by Jensen et al. 2000: astro-ph/0005609). We obtain the following values: Mar. 4.5097 UT U=20.89 \pm 0.13 Mar. 4.499 UT B=21.49 \pm 0.05 Mar. 4.478 UT V=20.98 \pm 0.05 Mar. 4.485 UT I=20.28 \pm 0.07 As discussed by Garnavich et al. (2000b), to take full advantage of this unique burst a uniform reduction of all CCD data available would be most desired. To encourage such an endeavor, we make all our CCD data (seven 1kx1k frames; see also GCN 573 and 581) publicly available through the anonymous ftp at ftp://cfa-ftp.harvard.edu/pub/kstanek/GRB000301C/ Please contact K. Z. Stanek (kstanek@cfa.harvard.edu) if you have any questions concerning the data. This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1063 SUBJECT: GRB000301C: Late-time HST/STIS observation DATE: 01/05/29 19:48:38 GMT FROM: Andrew S. Fruchter at STScI A. Fruchter and P. Vreeswijk report for a larger collaboration: The field of GRB 000301c was reobserved by the Hubble Space Telescope using the STIS camera in open (50CCD) mode on the 25 Feb 2001, or nearly one year after outburst. Twelve dithered exposures were combined to produce a final image with an exposure time of 7031s. No source is immediately visible at the position of the GRB. However, when the image is convolved with gaussians or boxcars with characteristic sizes from that of the PSF, 0."08, to 0."2, an extended object appears to be visible under the position of the GRB and to its NE. Although extended light from both a nearby bright star, and the larger galaxy to the NW of the GRB make an exact determination of the significance of this object difficult, we believe this is approximately a 3-4 sigma detection. The probable host has an estimated magnitude of R = 28.0 +/- 0.3. This magnitude is just consistent with the estimates of an underlying host from our earlier imaging, GCN 627 and 701. It is, furthermore, about two magnitudes brighter than we would expect the OT to have been at this time, had it continued to decline with a temporal power-law steeper than -2 (c.f. GCN 701 and Rhoads and Fruchter, ApJ 2001, 546, 177). If this is indeed a detection of a host, then in all cases where we have obtained a deep HST image and an OT is well localized (to ~0."1), a host has been found under the GRB. However, again, due to the scattered and extended light in this region of the image, the detection must be considered tentative. The image can be seen at http://www.stsci.edu/~fruchter/GRB/000301C