//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18499 SUBJECT: GRB 151027B: Swift detection of its 1000-th burst DATE: 15/10/27 22:56:57 GMT FROM: Scott Barthelmy at NASA/GSFC T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), A. D'Ai (INAF-IASFPA), N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), A. Maselli (INAF-IASFPA), K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/PSU) and R. L. C. Starling (U Leicester) report on behalf of the Swift Team: At 22:40:40 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 151027B (trigger=661869). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 76.238, -6.427, which is RA(J2000) = 05h 04m 57s Dec(J2000) = -06d 25' 35" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a peak with a duration of about 50 sec. The peak count rate was ~1000 counts/sec (15-350 keV), at ~40 sec after the trigger. The XRT began observing the field at 22:44:04.0 UT, 203.4 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 76.21944, -6.45010 which is equivalent to: RA(J2000) = 05h 04m 52.67s Dec(J2000) = -06d 27' 00.4" with an uncertainty of 3.9 arcseconds (radius, 90% containment). This location is 106 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 9.43 x 10^20 cm^-2 (Willingale et al. 2013). The initial flux in the 2.5 s image was 5.37e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 209 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 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 0.25. Burst Advocate for this burst is T. N. Ukwatta (tilan.ukwatta AT gmail.com). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18501 SUBJECT: GRB 151027B: NOT optical afterglow candidate DATE: 15/10/28 00:19:30 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst Daniele Malesani (DARK/NBI), Nial R. Tanvir (Univ. Leicester), Dong Xu (NAOC/CAS), Jussi Harmanen (NOT and Univ. Turku), Thomas Reynolds (NOT and Turku Univ.), and Pere Blay Serrano (IAC/NOT), report on behalf of a larger collaboration: We observed the field of the #1000 Swift GRB 151027B (Ukwatta et al., GCN 18499) with the Nordic Optical Telescope equipped with the StanCam imager. Observations started on 2015 Oct 27.988 UT (1.04 hr after the GRB trigger), as soon as the field was observable from La Palma. In our first 5-minute image taken in the R band, we detect a single source consistent with the XRT position (Ukwatta et al., GCN 18499), at coordinates (J2000): RA = 05:04:52.69 Dec = -06:27:00.8 with an uncertainty of 0.5". Calibrating the image against nearby USNO stars, we measure for this object R = 18.44 +- 0.05 (Vega). While we have not yet any variability information, the positional consistency with the XRT error circle and the lack of any object in the DSS at this location suggest that this is the optical afterglow of GRB 151027B. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18504 SUBJECT: GRB 151027B: Enhanced Swift-XRT position DATE: 15/10/28 03:56:46 GMT FROM: Phil Evans at U of Leicester J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 1168 s of XRT Photon Counting mode data and 3 UVOT images for GRB 151027B, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 76.21941, -6.45016 which is equivalent to: RA (J2000): 05h 04m 52.66s Dec (J2000): -06d 27' 00.6" with an uncertainty of 1.8 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18505 SUBJECT: GRB 151027B: VLT/X-shooter redshift DATE: 15/10/28 06:34:50 GMT FROM: Nial Tanvir at U.Leicester D. Xu (NAOC/CAS), N. R. Tanvir (U. Leicester), D. Malesani, J. Fynbo (DARK) report: We observed the optical afterglow of GRB 151027B (Ukwatta et al. GCN 18499, Malesani et al. GCN 18501) with the VLT X-shooter spectrograph covering a spectral range 3400A to 18000A. Observations began at 2015 Oct 28 03:50 UT, approximately 5h09m post-burst. The spectrum shows a clear continuum in the red, with a strong break corresponding to Ly-alpha at a redshift of z=4.063. This is supported by detection of absorption lines of Si II 1259/1260, Si II* 1265, CII 1335, CII* 1336, OI 1302, SiII 1304, S IV 1394/1403, CIV 1548/1551, FeII 1608 and Al II 1671 at that redshift. We therefore propose this as the redshift of the 1000th Swift GRB. We thank the staff at Paranal, particularly T. Rivinius, for their support in obtaining these observations. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18507 SUBJECT: GRB 151027B: GROND Optical/NIR Afterglow Detection DATE: 15/10/28 07:40:47 GMT FROM: Philip Wiseman at MPE/Swift P. Wiseman, J. Greiner (both MPE Garching) report on behalf of the GROND team: We observed the field of GRB 151027B (Swift trigger 661869; (Ukwatta et al., GCN 18499) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile). Observations started at 06:24 UT on 28/10/2015, 7 hrs 45 mins after the GRB trigger, and are continuing. They were performed at an average seeing of 0.9" and at an average airmass of 1.1. We found a single point source within the enhanced 1.8" Swift-XRT error circle reported by Evans et al. (GCN 18504), common with that reported by Malesani et al. (GCN 18501) and Xu et al. (GCN 18505). Based on 6.6 min of total exposures in g'r'i'z'JHK at a mid time of 06:33:39 UT, we estimate preliminary magnitudes (all in AB system) of g' > 22.4 mag, r' = 20.8 +/- 0.08 mag, i' = 20.1 +/- 0.07 mag, z' = 20.1 +/- 0.07 mag, J = 20.1 +/- 0.4 mag, H = 19.1 +/- 0.3 mag, and K > 18.3 mag. A clear g'-band drop out in the SED leads to a photo-z of 4.3 + 0.3,-0.2, consistent with the redshift derived from the X-shooter spectrum (Xu et al., GCN 18505). The source appears to be fading relative to the NOT report (Malesani et al., GCN 18501), and has continued to do so during our observations. Given magnitudes are calibrated against GROND zeropoints (g'r'i'z') as well as 2MASS field stars (JHK) and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.2 mag in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18509 SUBJECT: GRB 151027B: Swift-XRT refined Analysis DATE: 15/10/28 10:57:09 GMT FROM: Phil Evans at U of Leicester V. D'Elia (ASDC), A. D'ai (INAF-IASFPA), A. Maselli (INAF-IASFPA), L.M. McCauley (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester) and T.N. Ukwatta report on behalf of the Swift-XRT team: We have analysed 12 ks of XRT data for GRB 151027B (Ukwatta et al. GCN Circ. 18499), from 191 s to 32.5 ks after the BAT trigger. The data comprise 61 s in Windowed Timing (WT) mode (the first 8 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 18504). The light curve can be modelled with an initial power-law decay with an index of alpha=5.7 (+/-0.6), followed by a break at T+332 s to an alpha of 0.66 (+0.05, -0.06). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.81 (+0.14, -0.13). The best-fitting absorption column is 4.1 (+2.5, -2.2) x 10^22 cm^-2, at a redshift of 4.063, in addition to the Galactic value of 9.4 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.8 x 10^-11 (4.8 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Galactic foreground: 9.4 x 10^20 cm^-2 Intrinsic column: 4.1 (+2.5, -2.2) x 10^22 cm^-2 at z=4.063 Photon index: 1.81 (+0.14, -0.13) If the light curve continues to decay with a power-law decay index of 0.66, the count rate at T+24 hours will be 0.026 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.9 x 10^-13 (1.2 x 10^-12) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00661869. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18511 SUBJECT: GRB 151027B: MASTER-NET early OT detection DATE: 15/10/28 13:24:39 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs D.Buckley, S. Potter, A.Kniazev, M.Kotze South African Astronomical Observatory R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias E. Gorbovskoy, V. Lipunov, N.Tyurina, V.Kornilov, P.Balanutsa, A.Kuznetsov, D.Kuvshinov, D. Vlasenko, E.Popova Lomonosov Moscow State University, Sternberg Astronomical Institute K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik Kislovodsk Solar Station of the Pulkovo Observatory V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov Blagoveschensk Educational State University, Blagoveschensk V.Krushinski, I.Zalozhnih Ural Federal University, Kourovka Hugo Levato and Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) Claudio Mallamaci, Carlos Lopez and Federico Podest Observatorio Astronomico Felix Aguilar (OAFA) Two MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in SAAO and IAC was pointed to the GRB151027B (Ukwatta et. al GCN 18499) 25 sec after notice time and 156 sec after trigger time at 2015-10-27 22:43:19 UT. On our first (30s exposure) set we haven`t found optical transient (Malesani et. al. GCN 18501, Xu et. al. GCN 18505, Wiseman et. al GCN 18507) within SWIFT error-box. The 2-sigma upper limit has been about 17.7 mag. The observations were significantly complicate the closest distance to the Moon (~ 35 d). The Moon background light is picked up the sky background on our cameras more than 10 times. Therefore, we could not get deep enough image. Nevertheless, we detect OT on a several coadd images in consequent time in SAAO. The first time we see OT 475 seconds after the trigger with magnitude ~ 18.9. OT had a slight brightening 1736 seconds after the trigger to 18.5 mag. The preliminary photometry available at table below. Table 1. GRB151027B MASTER-SAAO Early photometry. T-Ts T-Tm Exptime Mag.(P/+P\) Coadd 159 174 2 x 30 >17.7 1 201 221 2 x 40 >18.0 1 252 277 2 x 50 >18.3 1 313 343 2 x 60 >18.3 1 384 424 2 x 80 >18.4 1 159 311 2 x 260 >19.0 5 475 842 2 x 690 18.9 5 1235 1736 2 x 900 18.5 5 2264 3280 2 x 1800 18.9 10 3499 4515 2 x 1800 19.1 10 T - is trigger time, Ts - exposure start time, Tm - exposure middle time. We see OT in separate polarizations on s/n~5 confidence lewel. Table 1 shows the averaged data from two mutually perpendicular polarization. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18512 SUBJECT: GRB 151027B: RATIR Observations DATE: 15/10/28 14:10:19 GMT FROM: Nat Butler at UC berkeley Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (GSFC/STScI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid Georgiev (UNAM), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report: We observed the field of GRB 151027B (Ukwatta et al., GCN 18499) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir from 2015/10 28.26 to 2015/10 28.51 UTC (7.46 to 13.55 hours after the BAT trigger), obtaining a total of 3.51 hours exposure in the r, i, and z bands. We detect a source at 05:04:52.69 -06:27:00.8 (J2000, +/-0.05), within the Swift-XRT error circle. In comparison with the USNO-B1 and 2MASS catalogs, we obtain the following detections: r = 20.83 +/- 0.05 i = 20.18 +/- 0.04 z = 19.49 +/- 0.21 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. This source coincides with the source reported by Malesani et al. (GCN 18501), Xu et al. (GCN 18505), Wiseman et al. (GCN 18507), and Buckley et al. (GCN 18511). The source appears to have faded since these earlier observations and furthermore fades by about 0.5 mag in i over the course of our observations. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18514 SUBJECT: GRB 151027B: Swift-BAT refined analysis DATE: 15/10/28 14:29:31 GMT FROM: Amy Lien at GSFC T. Sakamoto (AGU), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 151027B (trigger #661869) (Ukwatta, et al., GCN Circ. 18499). The BAT ground-calculated position is RA, Dec = 76.188, -6.428 deg which is RA(J2000) = 05h 04m 45.0s Dec(J2000) = -06d 25' 40.2" with an uncertainty of 2.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 17%. The mask-weighted light curve shows a complex structure with several overlapping peaks that starts at ~T0 and ends at ~T+100 s. T90 (15-350 keV) is 80.00 +- 35.78 sec (estimated error including systematics). The time-averaged spectrum from T+1.00 to T+97.00 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.83 +- 0.27. The fluence in the 15-150 keV band is 1.5 +- 0.3 x 10^-6 erg/cm2. The 1-s peak photon flux is unconstrained due to the weakness of the burst. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/661869/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18517 SUBJECT: GRB 151027B: Swift/UVOT Upper Limits DATE: 15/10/28 15:45:21 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (UCL-MSSL) and T. N. Ukwatta (LANL) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 151027B 210 s after the BAT trigger (Ukwatta et al., GCN Circ. 18499). No optical afterglow consistent with the XRT position (Osborne et al. GCN Circ. 18504) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 210 359 147 >20.0 white 210 4545 344 >20.5 v 366 4956 216 >18.8 b 4141 5737 354 >20.6 u 3935 5571 393 >20.4 w1 415 5366 397 >20.4 m2 4961 5161 197 >19.1 w2 4551 4751 197 >19.9 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.25 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18520 SUBJECT: GRB 151027B: LCOGT FTN afterglow observations DATE: 15/10/28 20:13:07 GMT FROM: Simone Dichiara at Ferrara U/Italy S. Dichiara (U. Ferrara, ICRANet), D. Kopac (U. Ljubljana), C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), A. Gomboc (U. Ljubljana) on behalf of a larger collaboration report: The 2-m Faulkes Telescope North in Hawaii began observing Swift GRB 151027B (Ukwatta et al., GCN 18499) on October 28, 12:18:25 UT, i.e., ~ 13.6 hours after the burst trigger, with the r' and i' filters. Although we did not detect the optical counterpart (Malesani et al., GCN 18501; Xu et al., GCN 18505; Wiseman et al., GCN 18507; Buckley et al., GCN 18511; Watson et al., GCN 18512) in the r' filter (R > 20.3), the source is detected in the i' filter with I = 19.6 +/- 0.3 mag at a mid time of 13.9 hours post burst (total exposure in i' of 600 s). The magnitude is calibrated against nearby USNO-B1 stars. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18529 SUBJECT: GRB 151027B: Swift UVOT detection DATE: 15/10/29 15:34:43 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (UCL-MSSL) and T. N. Ukwatta (LANL) report on behalf of the Swift/UVOT team: In Swift/UVOT followup observations of GRB 151027B (Ukwatta et al., GCN Circ. 18499) a source is found in the summed up V filter exposures at a position consistent with the XRT (Osborne et al., GCN Circ. 18504) and the optical/NIR counterparts reported by Malesani et al. GCN Circ. 18501, Xu et al. GCN Circ. 18505, Wiseman and Greiner GCN Circ. 18507, Buckley et al. GCN Circ. 18511, Watson et al. GCN Circ. 18512, and Dichiara et al. GCN Circ. 18520. A preliminary detection using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for V data taken in the first and second segment is: Filter T_start(s) T_stop(s) Exp(s) Mag v 191 28529 1986 20.8 ± 0.3 The magnitudes in the table are not corrected for the strong Galactic extinction due to the reddening of E(B-V) = 0.25 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18543 SUBJECT: GRB 151027B: RATIR Late-Time Upper Limits DATE: 15/10/31 15:12:21 GMT FROM: Nat Butler at UC berkeley Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (GSFC/STScI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid Georgiev (UNAM), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report: We observed the field of GRB 151027B (Ukwatta, et al., GCN 18499) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir from 2015/10 31.23 to 2015/10 31.52 UTC (78.85 to 85.85 hours after the BAT trigger), obtaining a total of 5.20 hours exposure in the r, i, and z bands. We no longer detect the optical afterglow (Malesani et al., GCN 18501). In comparison with the USNO-B1 and 2MASS catalogs, we obtain the following upper limits (3-sigma): r > 23.45 i > 23.39 z > 18.57 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir.//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18548 SUBJECT: GRB 151027B: ATCA radio detection DATE: 15/11/01 07:01:04 GMT FROM: Jochen Greiner at MPI J. Greiner (MPE), M. Wieringa (CSIRO), P. Wiseman (MPE) report for a larger consortium: We observed the field of GRB 151027B (Swift trigger 661869; Ukwatta et al., GCN 18499) simultaneously at 5.5 and 9 GHz with the Australia Telescope Compact Array (ATCA), beginning at October 30.54 UT for 3.3 hrs. At a mean frequency of 9 GHz (with 2 GHz bandwidth) we detect a source at ~67+/-10 microJy at the position of the optical afterglow (Malesani et al., GCN 18501; Wiseman et al., GCN 18507). At the redshift of z=4.063 (Xu et al., GCN 18506) this is among the most luminous GRB radio afterglows. We are grateful to P. Edwards for scheduling this observation.