//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5880 SUBJECT: GRB 061201: Coincidence with a Galaxy Cluster DATE: 06/12/01 16:23:13 GMT FROM: Josh Bloom at UC Berkeley J. S. Bloom (UC Berkeley) notes: "We note that this apparent short burst GRB (Swift trigger 241840) was localized to within 10 arcmin of a known cluster of galaxies (J2000 center = 22h09m34s, -74d27.3m, Abell 995; Abell et al. ApJS, 1989). Though no redshift is known for this galaxy cluster and the GRB has not (as of yet) been associated with a member of this cluster, we suggest, tentatively, that GRB 061201 has arisen from what is likely a relatively low redshift (z < 0.3). The XRT position appears consistent with the outskirts of a faint galaxy detected in the DSS." This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5881 SUBJECT: GRB 061201: Swift detection of a short hard burst DATE: 06/12/01 16:24:30 GMT FROM: David Palmer at LANL F. E. Marshall (NASA/GSFC), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), O. Godet (U Leicester), S. T. Holland (GSFC/USRA), J. A. Kennea (PSU), H. A. Krimm (GSFC/USRA), W. B. Landsman (NASA/GSFC), V. Mangano (INAF-IASFPA), C. B. Markwardt (GSFC/UMD), K. M. McLean (LANL/UTD), A. Moretti (INAF-OAB), D. M. Palmer (LANL), S. B. Pandey (UCL-MSSL), A. M. Parsons (GSFC), T. Sakamoto (NASA/ORAU), R. L. C. Starling (U Leicester) and D. E. Vanden Berk (PSU) report on behalf of the Swift Team: At 15:58:36 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 061201 (trigger=241840). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 331.972, -74.600 which is RA(J2000) = 22h 07m 53s Dec(J2000) = -74d 36' 01" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak with some sub-structure and total duration of about 2 sec. The peak count rate was ~20000 counts/sec (15-350 keV), at ~1 sec after the trigger. This is also a very hard burst with ~8000 counts/sec in the highest energy bin (100-350 keV) and ~1000 counts/sec in the lowest energy bin (15-25 keV). The XRT began taking data at 15:59:58 UT, 81 seconds after the BAT trigger. The XRT on-board centroid algorithm did not find a source in the image and no prompt position is available. Down-linked data show a variable source at position: RA(J2000) = 22h 08m 32.07s DEC(J2000) = -74d 34' 47.0" with 3.8" of uncertainty (90% confidence). This position lies 170 arcseconds from the BAT position. UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 86 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.08. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5882 SUBJECT: GRB 061201, Swift-BAT refined analysis of the SHB DATE: 06/12/01 21:30:20 GMT FROM: Scott Barthelmy at NASA/GSFC C. Markwardt (GSFC/UMD), L. Barbier (GSFC), S.D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), F.E. Marshall (NASA/GSFC), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC) on behalf of the Swift-BAT team: Using the data set from T-239 to T+366 sec from the recent telemetry downlink, we report further analysis of BAT GRB 061201 (trigger #241840) (Marshall, et al., GCN Circ. 5881). The BAT ground-calculated position is RA, Dec = 332.079, -74.569 deg which is RA(J2000) = 22h 08m 19.0s Dec(J2000) = -74d 34' 6.6" with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 48%. The mask-weighted lightcurve shows two main peaks separated by ~0.7 sec, the first starting at T+0 sec, and the second ending at T+1.1 sec. A visual scan of the lightcurve (from T+2 to T+300 sec) places an upper limit of 0.01 ph/cm2/sec for any extended emission. T90 (15-350 keV) is 0.8 +- 0.1 sec (estimated error including systematics). The time-averaged spectrum from T+0.0 to T+0.9 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 0.81 +- 0.15. The fluence in the 15-150 keV band is 3.3 +- 0.3 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.05 sec in the 15-150 keV band is 3.9 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The burst shows significant hard to soft spectral evolution. A fit to the first peak (T+0.0 to T+0.7) gives a simple power law index of 0.57 +/- 0.15, while a fit to the second peak (T+0.7 to T+0.9) has a power law index of 2.10 +/- 0.35. Similarly, the light curve shows that the emission in the 15-25 keV channel extends to T+1.5 sec, while emission in the 100-350 keV channel lasts only until ~T+0.6 sec. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5883 SUBJECT: GRB 061201: Initial UVOT Observations DATE: 06/12/01 23:43:24 GMT FROM: Stephen Holland at USRA/NASA/GSFC/SSC S. T. Holland (CRESST/GSFC/USRA) and F. Marshall (GSFC) report on behalf of the Swift team: UVOT took a finding chart exposure of 98 seconds with the White filter (160-650 nm) filter starting 86 seconds after the BAT trigger. There is a possible faint source in the XRT error circle (Marshall et al. GCN Circ. 5881) at RA(J2000) = 22:08:32.21 DEC(J2000) = -74:34:47.3 with a 1-sigma error radius of about 1.0 arc sec. The possible source has a preliminary White magnitude of 20.9 +/- 0.6 and is detected at the 2.5-sigma significance level. No correction has been made for the expected Milky Way extinction corresponding to E(B-V) of 0.08 mag. This possible source is also detected in a 197 s White exposure starting 6202 s after the BAT trigger with a significant of 3.1-sigma and a preliminary White magnitude of 20.9 +/- 0.4. Since the source is not fading, it is unlikely to be the optical afterglow of GRB 061201, but it may be the host galaxy. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5884 SUBJECT: GRB 061201: VLT optical observations DATE: 06/12/02 02:19:07 GMT FROM: Paolo D'Avanzo at INAF-OAB P. D'Avanzo (INAF-OAB & Univ. Insubria), S. Piranomonte (INAF-OAR), G. Chincarini (INAF.OABr & Univ. Milano-Bicocca), & L. Stella (INAF-OAR), on behalf of the MISTICI collaboration, report: We observed the field of the short GRB061201 (Marshall et al., GCN 5881, Markwardt et al. GCN 5882) with the VLT equipped with the FORS2 camera. Our observations started on Dec 02.014 UT (8.38 hr after the GRB). We took 10 I-band images, for a total exposure of 900 s. An object is clearly visible in the resulting average of our set of images at the following coordinates (J2000): R.A.=22:08:32.090 Dec.=-74:34:47.08 with an uncertainty of 0.2 arcsecs. This position is consistent with the one reported by Holland and Marshall (GCN 5883). We measure I ~ 22.3 based on the zeropoints reported on the ESO web pages. Given the different adopted filter and the large error in the UVOT measurement, it is difficult to assess variability between the two epochs. We note that the object does not seem to be extended. We also clearly resolve a galaxy 17" NW of the XRT position. Further analysis is in progress. We thank the excellent support of the ESO staff, in particular Paola Amico and Chris Lidman. This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5885 SUBJECT: GRB 061201: Swift XRT Team refined analysis DATE: 06/12/02 03:20:58 GMT FROM: Matteo Perri at ISAC/ASDC M. Perri, G. Stratta, M.L. Conciatore (ASDC), D. N. Burrows (PSU) and F. E. Marshall (NASA/GSFC) report on behalf of the Swift XRT team: We have analysed the first 4 orbits of Swift XRT data on the GRB 061201 (Marshall et al., GCN Circ. 5881). A 2.7 ks photon counting mode image provides a refined XRT position: RA(J2000) = 22h 08m 32.21s Dec(J2000) = -74d 34m 47.6" with an uncertainty of 3.6 arcsec (90% containment). This position is 0.8 arcsec away from the first XRT position quoted in Marshall et al. (GCN Circ. 5881), 0.3 arcseconds from the UVOT optical source (Holland et al., GCN Circ. 5883) and 0.7 arcseconds from the object reported by D'Avanzo et al. (GCN Circ. 5884). The 0.3-10 keV X-ray light curve between 86s and 18.1ks after the trigger can be fit with a broken power-law with an initial decay slope of -0.56+/-0.15, a break at 1835+1178-1139s, and a post-break slope of -1.6+/-0.4. The X-ray spectrum covering the time period from T+99s to T+729s is well fit by an absorbed power-law with a photon index of 1.5+/-0.2 and column density of (1.2+/-0.6)e21 cm**-2. We note the Galactic column density in the direction of the source is 5.0e20 cm**-2. Assuming the X-ray emission continues to decline at the same rate, we predict a 0.3-10 keV XRT count rate of 0.002 count/s at T+24hr, which corresponds to an observed 0.3-10 keV flux of 1.1e-13 erg/cm**2/s. This circular is an official product of the Swift XRT Team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5890 SUBJECT: Konus-Wind observation of GRB 061201 DATE: 06/12/02 17:42:07 GMT FROM: Valentin Pal'shin at Ioffe Inst S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and T. Cline on behalf of the Konus-Wind team report: The short hard GRB 061201 (Swift-BAT trigger #241840; Marshall et al., GCN 5881; Markwardt et al., GCN 5882) triggered Konus-Wind at T0=57514.558 s UT (15:58:34.558). As observed by Konus-Wind it had a duration of ~0.6 s, fluence 5.33(-4.44, +0.70)x10^-6 erg/cm2, the 16-ms peak flux measured from T0+0.528 3.19(-2.72, +0.72)x10^-5 erg/cm2/s (both in the 20 keV - 3 MeV energy range). The time-integrated spectrum of the GRB (from T0 to T0+8.448 s) is well fitted (in the 20 keV - 3 MeV range) by a power law with exponential cutoff model: dN/dE ~ E^(-alpha) * exp(-(2-alpha)*E/Ep) with alpha = 0.36(-0.65, +0.40) and Ep = 873(-284, +458) keV (chi2 = 79/67 dof). All the quoted errors are at the 90% confidence level. The Konus-Wind light curve of this GRB is available at http://www.ioffe.rssi.ru/LEA/GRBs/GRB061201_T57514/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5895 SUBJECT: GRB 061201: SOAR Confirmation of Candidate Afterglow DATE: 06/12/03 20:55:46 GMT FROM: Josh Haislip at U.North Carolina J. Haislip, A. LaCluyze, D. Reichart, S. Heathcote, P. Ugarte, A. Alvares, R. Baptista, & M. Nysewander report on behalf of the UNC team of the FUN GRB Collaboration: We observed the localization of the short/hard GRB 061201 (Marshal et al., GCN 5881) with SOAR/OSIRIS in JKs beginning 10.2 hours after the burst. We detect the source identified by Holland et al. (GCN 5883) and D'Avanzo et al. (GCN 5884). We reobserved the field in J beginning 33.6 hours after the burst. The source appears to have faded by at least 1.3 mag (3 sigma) and is no longer detected. Consequently, this source appears to be the afterglow. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5896 SUBJECT: GRB 061201: VLT optical decay DATE: 06/12/03 22:58:20 GMT FROM: Paolo D'Avanzo at INAF-OAB P. D'Avanzo (INAF-OABr & Univ. Insubria) and S. Piranomonte (INAF-OAR) report on behalf of the MISTICI collaboration: We continued monitoring the afterglow of the short GRB061201 (Marshall et al., GCN 5881) with the VLT equipped with the FORS2 camera. Observations were carried out in the I filter. From a comparison with a set of nearby field stars we conclude that the object detected in our previous images (D'Avanzo et al. GCN 5884; see also Holland et al. GCN 5883) faded in the I-band by about 1.8 mag between Dec 2.025 UT and Dec 3.045 UT (0.359 and 1.379 days after the burst, respectively). The inferred decay index is thus ~ 1.2. We note a discrepancy of about 0.7 mag in the absolute calibration during the two nights, based on observations of Landolt standard fields. We thus warn that the absolute calibration is still preliminary. The decay slope is however independent of this and thus robust. We thus fully confirm that the object proposed by Holland et al. (GCN 5883) and D'Avanzo et al. (GCN 5884) is the optical afterglow of GRB 061201, as already found by Haislip et al. (GCN 5895). We thank the support of the ESO staff. This message can be cited. [GCN OPS NOTE(03dec06): Per author's request, the missing phrase "is the optical afterglow of GRB 061201" was added to the 3rd paragraph.] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5898 SUBJECT: GRB 061201: UVOT Observations of a Fading Optical Afterglow DATE: 06/12/05 14:14:05 GMT FROM: Stephen Holland at USRA/NASA/GSFC/SSC S. T. Holland (CRESST/GSFC/USRA) and F. E. Marshall (NASA/GSFC) report on behalf of the Swift team: UVOT observed the field of GRB 061201 during the first 19972 s after the BAT trigger (Marshall et al., GCN Circ. 5881). We detect the source seen by D'Avanzo (2006, GCN Circ. 5884) at the 4.2-sigma level in the White filter (160-650 nm) and at the 4.5-sigma level in a coadded image of all the UV filters. The coordinates of the source in the White image are: RA(J2000) = 22:08:32.06 DEC(J2000) = -74:34:47.9 with a 1-sigma error radius of about 0.5 arcsec, consistent with the VLT source. Our magnitudes and 3-sigma upper limits for all the UVOT filters are: Filter Start Stop Exposure Mag Err Significance V 191 12,136 1118 20.8 3-sigma upper limit B 669 6197 206 20.9 3-sigma upper limit U 645 5992 216 20.7 0.4 2.6 UVW1 621 17,926 519 20.7 0.5 2.9 21,392 58,442 11,555 22.9 0.5 2.5 86,427 160,471 19,972 23.0 3-sigma upper limit UVM2 5384 15,948 676 20.5 0.5 2.7 UVW2 697 6512 122 19.8 0.5 2.5 White 86 6402 304 20.8 0.3 4.2 Comb. UV 621 17,926 1337 20.8 0.4 4.5 The magnitude in the combined UV exposure (coadded UVW1, UVM2, and UVW2) between 621 sand 17,926 s is 20.8 +/- 0.4, assuming that the source has equal magnitude in each of these filters. Since the source is detected in the UVW2 filter, we estimate an upper limit to the redshift of about 1.7. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5909 SUBJECT: GRB061201, VLT optical decay: correction DATE: 06/12/12 15:00:46 GMT FROM: Paolo D'Avanzo at INAF-OAB P. D'Avanzo (INAF-OABr & Univ. Insubria) and S. Piranomonte (INAF-OAR) report on behalf of the MISTICI collaboration: A careful inspection and re-analysis of our VLT I-band images of the short GRB061201 (D'Avanzo & Piranomonte, GCN 5896) reveals that in our second epoch of observations (carried out 1.379 days after the burst) no object is clearly visible at the position of the optical counterpart (Holland et al. GCN 5883, Haislip et al. GCN 5895, D'Avanzo et al. GCN 5884) down to I > 23.6 mag (3sigma confidence level). So, with respect to our first epoch of observation (D'Avanzo et al. GCN 5884) the afterglow clearly faded, but we can only constrain the decay index to be > 0.8. This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5944 SUBJECT: GRB 061201: Magellan Redshift of nearby Abell cluster DATE: 06/12/20 07:42:22 GMT FROM: Josh Bloom at UC Berkeley S. Blondin, G. Narayan (Harvard/CfA), J. S. Bloom (UC Berkeley), H- W. Chen (U Chicago), R. P. Kirshner, P. Challis, M. Hicken, M. Modjaz, A. Friedman, M. Wood-Vasey (Harvard/CfA), and J. X. Prochaska (UC Santa Cruz) report on behalf of a larger collaboration: "The final X-ray afterglow position (Perri et al. 2006; GCN 5885) of the short-hard GRB 061201 (Marshall et al. 2006; GCN 5881) lies 8.5 arcmin from the center of the rich Abell cluster 995 (Bloom 2006; GCN 5880). On 13 December 2006 UT, we obtained several spectra of bright apparent cluster members with the LDSS-3 instrument mounted on the Magellan Clay 6.5m Telescope in Chile. We find the following redshifts based upon a preliminary inspection of the spectra: RA (J2000) DEC(J2000) =========================== object A: z=0.239 22:08:32.1 -74:34:47 object B: z=0.235 22:09:37.1 -74:26:39 object D: z=0.238 22:09:05.3 -74:29:29 Based on this, we claim a redshift of z=~0.237 for Abell 995 and note that while the GRB is not yet definitively associated with a cluster member galaxy, this redshift (and hence the implied energetics of the event) are very similar to the putative redshifts of short-hard GRBs 050509b (z=0.225), 050724 (z=0.258), and 060502b (z=0.287)." This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5945 SUBJECT: GRB 061201: Correction to GCN 5944 DATE: 06/12/20 18:19:35 GMT FROM: Josh Bloom at UC Berkeley J. S. Bloom (UC Berkeley) notes: "The coordinates for one of the galaxies observed in the Abell cluster 995 was given incorrectly in GCN 5944. The correct coordinates are: object A: z=0.239 22:09:51.9 -74:31:11 We thank Paolo D'Avanzo for pointing out the error." This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5952 SUBJECT: GRB 061201: Magellan redshift of nearby galaxy DATE: 06/12/21 21:13:16 GMT FROM: Edo Berger at Carnegie Obs E. Berger (Carnegie) reports: "Starting on 2006 Dec. 21.07 UT we used LDSS3 on Magellan to obtain an 1800 sec spectrum of the galaxy located 17 arcsec NW of the optical afterglow of the short GRB 061201 (see also GCN #5884). This is the nearest bright galaxy (R~19 mag) to the GRB position. We detect several emission lines, which we identify as H-beta, [OIII], H-alpha, [NII], and [SII] at a redshift of z=0.111. At this redshift the projected offset of the burst is about 34 kpc, significantly smaller than about 1.9 Mpc relative to the center of Abell 995 (GCN #5944)." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5995 SUBJECT: GRB 061201: Nearby Galaxy Cluster Abell 995 is at z=0.0865 DATE: 07/01/04 23:39:54 GMT FROM: Edo Berger at Carnegie Obs E. Berger (Carnegie Observatories) reports: "On December 21.06 UT we used LDSS3 on the Magellan/Clay 6.5-m telescope to obtain spectra of nine apparent members of the galaxy cluster Abell 995 located 8.5 arcmin away from the position of the short GRB 061201 (GCN 5880). Three of these galaxies have been previously observed by Blondin et al. leading to a proposed redshift of z~0.237 for the cluster (GCN 5944). Based on our spectra, which cover the range of about 4000-9500A, we find instead the following redshifts for the nine cluster members: Redshift RA Dec -------------------------------------------- z=0.0866 22:09:43.735 -74:26:28.92 z=0.0877 22:09:37.067 -74:26:39.84 *(object B) z=0.0873 22:09:05.248 -74:29:29.55 *(object D) z=0.0849 22:09:51.790 -74:31:11.06 *(object A) z=0.0843 22:08:34.675 -74:26:20.81 z=0.0864 22:09:40.015 -74:26:53.18 z=0.0866 22:09:48.052 -74:28:26.22 z=0.0876 22:09:25.530 -74:29:50.85 z=0.0872 22:09:32.120 -74:27:35.99 These redshifts are based on absorption features corresponding to CaII H&K, G-band, Mg b, E-band, and Na D, as well as H-alpha emission in four of the nine objects. We therefore conclude that the redshift of Abell 995 is z=0.0835. The previously claimed redshift of z~0.237 is likely based on a mis-identification of the Na D feature at lambda_rest ~ 5893A as Mg b at lambda_rest ~ 5174A. At the correct redshift of the cluster, the projected offset of GRB 061201 is about 0.8 Mpc from the center of the cluster. To cover this distance over a period of about 10 Gyr, the kick velocity would have to be >80 km/sec. Finally, we re-iterate the presence of a z=0.111 galaxy about 17 arcsec from the optical position of GRB 061201, corresponding to a significantly smaller offset of about 34 kpc (GCN 5952)." *Objects A,B,D refer to the designation in GCN 5944