This file contains both GRB 070419A and 070419B. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6302 SUBJECT: GRB 070419: Swift detection of a burst DATE: 07/04/19 10:30:53 GMT FROM: David Palmer at LANL M. Stamatikos (NASA/ORAU), D. N. Burrows (PSU), S. Campana (INAF-OAB), G. Cusumano (INAF-IASFPA), P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), C. Gronwall (PSU), C. Guidorzi (Univ Bicocca&INAF-OAB), V. La Parola (INAF-IASFPA), W. B. Landsman (NASA/GSFC), V. Mangano (INAF-IASFPA), C. B. Markwardt (GSFC/UMD), P. T. O'Brien (U Leicester), D. M. Palmer (LANL), A. M. Parsons (GSFC), P. Romano (Univ. Bicocca & INAF-OAB), B. Sbarufatti (INAF-IASFPA), G. Stratta (ASDC), S. D. Vergani (DIAS-DCU) and H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team: At 09:59:26 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 070419 (trigger=276205). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 182.714, +39.908 which is RA(J2000) = 12h 10m 51s Dec(J2000) = +39d 54' 30" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve suggests emission from T-10 to T+20 with a peak count rate of ~500 counts/sec (15-350 keV), at ~4 sec after the trigger. However, as for most image triggers, the TDRSS light curve data is noisy and we will require the Malindi pass data for a more definitive analysis. The XRT began observing the field at 10:01:18 UT, 113 seconds after the BAT trigger. XRT found a bright, fading and uncatalogued X-ray source. The on ground calculated position is RA, Dec 182.7462, +39.9245 which is RA(J2000) = 12h 10m 59.1s Dec(J2000) =39d 55' 28.2" with an uncertainty of 7.0 arcseconds (radius, 90% containment). The given uncertainty takes into account the presence of a nearby CCD bad column. This location is 110 arcseconds from the BAT on-board position, within the BAT error circle. The initial flux in the 2.5s image was 3.7e-09 erg/cm2/s (0.2-10 keV). UVOT took a finding chart exposure of 400 seconds with the V filter starting 115 seconds after the BAT trigger. No 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 18.5 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 18.0 mag. No correction has been made for the expected extinction of about 0.1 magnitudes. We note there is a 7th magnitude star 3 arcminutes from the XRT position. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6303 SUBJECT: GRB 070419A: ROTSE-III Optical Limits DATE: 07/04/19 10:33:32 GMT FROM: Brad Schaefer at LSU B. E. Schaefer (Louisiana State), F. Yuan (U Mich), S.A. Yost (U Mich), report on behalf of the ROTSE collaboration: ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 070419A (Swift trigger 276205), producing images beginning 6.3 s after the GCN notice time. An automated response took the first image at 10:00:47.3 UT, 81.2 s after the burst, under excellent conditions. We took 10 5-sec, 10 20-sec and 20 60-sec eposures, with further exposures still continuing. These unfiltered images are calibrated relative to USNO A2.0 (R). There is a bright star in the BAT error circle, but this is well removed from the XRT position. Comparison to the DSS (second epoch) reveals no new sources within the 3-sigma XRT error circle, for both single images and coadding into sets of 10; the field is not crowded. Individual images have limiting magnitudes ranging from 15.2-17.6; we set the following specific limits. start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------- 10:00:47.3 10:00:52.3 5 16.0 81.2 N 10:00:47.3 10:01:54.4 67 17.8 81.2 Y //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6304 SUBJECT: GRB 070419 optical afterglow candidate DATE: 07/04/19 10:46:06 GMT FROM: Ryan Chornock at UC Berkeley R. Chornock, W. Li, A. V. Filippenko, and the KAIT GRB team (UC Berkeley) report: A faint (mag~19) optical source is present in Katzman Automatic Imaging Telescope (KAIT) images at coordinates (J2000) 12:10:58.82 +39:55:33.9 The first detection was in a 45sec unfiltered image starting at 10:05:19 UT. This position is consistent with the XRT position (GCN 6302) and the source does not appear to be present in DSS images. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6305 SUBJECT: GRB 070419B: Swift detection of a burst DATE: 07/04/19 11:12:05 GMT FROM: David Burrows at PSU/Swift A. M. Parsons (GSFC), D. N. Burrows (PSU), M. Capalbi (ASDC), P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), C. Gronwall (PSU), C. Guidorzi (Univ Bicocca&INAF-OAB), W. B. Landsman (NASA/GSFC), C. B. Markwardt (GSFC/UMD), F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester), D. M. Palmer (LANL), M. Perri (ASDC), P. Romano (Univ. Bicocca & INAF-OAB), E. Troja (INAF-IASFPA) and H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team: At 10:44:05 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 070419B (trigger=276212). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 315.719, -31.267 which is RA(J2000) = 21h 02m 52s Dec(J2000) = -31d 15' 59" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows multiple peaks, with a duration of about 160 seconds. The peak count rate was ~2500 counts/sec (15-350 keV), at ~0 sec after the trigger. We note that this burst is distinct from GRB 070419A (trigger 276206). The XRT began observing the field at 10:45:26 UT, 81 seconds after the BAT trigger. XRT found a bright, fading and uncatalogued X-ray source located at RA, Dec 315.7067, -31.2635 which is RA(J2000) = 21h 02m 49.6s Dec(J2000) = -31d 15' 48.6" with an uncertainty of 5 arcseconds (radius, 90% containment). This location is 40 arcseconds from the BAT on-board position, within the BAT error circle. The initial flux in the 2.5s image was 1.5e-08 erg/cm2/s (0.2-10 keV). UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 89 seconds after the BAT trigger. No 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 18.5 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 extinction. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6306 SUBJECT: GRB 070419: P60 Confirmation of Optical Afterglow DATE: 07/04/19 11:16:54 GMT FROM: S. Bradley Cenko at Caltech S. B. Cenko (Caltech) and D. B. Fox (Penn State) report on behalf of a larger collaboration: We have imaged the field of GRB070419 (Stamatikos et al., GCN 6302) with the automated Palomar 60-inch telescope. The candidate identified by Chornock et al. (GCN 5304) is visible in our images and variable; we therefore confirm it is the optical afterglow of GRB070419. Specifically, we measure the following R-band magnitudes: Mean Date Time Since Burst Magnitude -------------------------------------------------------------------------- 10:05:18 5.87 min 19.7 10:10:31 11.08 min 18.7 The above magnitudes were calculated assuming a magnitude of R=15.22 for the the USNO-B reference star located at 12:10:57.57, +39:55:40.2. Further observations are planned. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6308 SUBJECT: GRB 070419A: Kiso Optical observation DATE: 07/04/19 13:29:46 GMT FROM: Yuji Urata at Saitama U S. Nishiura, H. Tomita, Y. Urata and K.Y. Huang report on behalf of EAFON team "We have imaged the GRB 070419A field (Stamatikos et al. #6302) with the Kiso 1.05m Schmidt telescope. The optical afterglow reported by Chornock et al (#6304) and Cenko et al. (#6306) is visible in our B and R band images. We also confirmed the decaying during our observation. The afterglow brightness at 51 min after the burst is R~20.1 mag." Further observations and analysis are in progress. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6309 SUBJECT: Infrared detection of GRB070419A with UKIRT DATE: 07/04/19 14:10:53 GMT FROM: Evert Rol at U.Leicester E. Rol, N. Tanvir (U. of Leicester), T. Kerr (JAC), report for a larger collaboration: We observed the field of GRB070419A with UKIRT-WFCAM, starting 39 minutes after the GRB trigger (Stamatikos et al., GCN 6302). We find the following magnitudes for the infrared counterpart of GRB070419A: T filter magn error(magn) (hours post trigger) -------------------------------------------------- 0.654 J 18.27 0.08 0.734 H 17.83 0.13 0.814 J 18.56 0.09 0.896 K 17.26 0.18 1.665 K 18.30 0.18 The magnitudes are calibrated with respect to the 2MASS catalogue. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6310 SUBJECT: GRB070419A, optical observation DATE: 07/04/19 14:30:54 GMT FROM: Eri Sonoda at U of Miyazaki/Japan R. Hara, E.Sonoda, S.Maeno, H. Tanaka, N. Ohmori, M.Yamauchi (University of Miyazaki) We have observed the field covering the error circle of GRB070419A (GCN 6302, M. Stamatikos et al.) with the unfiltered CCD camera on the 30-cm telescope at University of Miyazaki. The observation was started 10:24:34 UT, ~25 min after the Swift trigger time. We have compared our data of 30 sec exposures with the USNO-A2.0 catalog, the upper limits are as follows: -------------------------------------------------------------- Start(UT) End(UT) Num. of frames Limit (mag.) -------------------------------------------------------------- 10:42:40 10:43:10 1 ~16.2 10:42:40 10:53:36 10 ~17.7 --------------------------------------------------------------- //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6311 SUBJECT: GRB 070419A: Lulin Optical observation DATE: 07/04/19 14:41:04 GMT FROM: Yuji Urata at Saitama U K.J. Fu, Y.H. Lee, K.Y. Huang and Y. Urata report on behalf of EAFON "We observed the optical afterglow of GRB070419A (Stamatikos et al #6302, Chornock et al #6304, Cenko et al #6306, Nishiura et al. #6308 and Rol et al #6309) with the Lulin One-meter Telescope started from 11:49 UT. The afterglow at 2.0 hours after the burst is visible in our R-band combined image with R = 21.8+/-0.3 (compared with USBO-B1.0 catalogue)." Further observations and analysis are in progress. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6312 SUBJECT: GRB 070419B: optical afterglow candidate DATE: 07/04/19 14:43:37 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia P. Tristram (MOA, Univ. of Canterbury), A. J. Castro-Tirado, A. de Ugarte Postigo (IAA-CSIC Granada), A. Gilmore, P. Kilmartin (Univ. of Canterbury), J. Gorosabel, M. Jelínek and R. Cunniffe (IAA-CSIC Granada), report: "Following the detection by Swift of the GRB 070419B (Parson et al. GCNC 6305), we have obtained R & I -band images at the 0.6m B&C telescope at the Mt. John Observatory on Lake Tekapo, New Zealand. They were taken starting on Apr 19.537 UT (i.e. 2.17 hr post-burst). The single frames (300s in R) reveal a point-like source with R ~ 20 consistent with the Swift/XRT error box which is not present in the DSS-2 red. Preliminary coordinates (+/- 1") yield: AR(2000): 21:02:49.80 Dec(2000): -31:15:49.23 Observations are ongoing. More details will be given on forthcoming GCN Circular." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6313 SUBJECT: GRB 070419A: Optical and IR observations with KANATA DATE: 07/04/19 14:46:36 GMT FROM: Makoto Uemura at Hiroshima U M. Uemura, A. Arai, and T. Uehara (Hiroshima Univ.), report on behalf of the KANATA GRB team: We took optical and IR images of the field of GRB070419A (GCN 6302) at 11:01-11:12 UT 19 Apr. using TRISPEC attached to the KANATA 1.5-m telescope at Higashi-Hiroshima Observatory, Japan. We obtained 10 sets of V, J, and Ks-band images with a 63, 60, and 48-s exposure times under thin clouds. No new object was significantly detected in the combined image (19.46322 Apr. 2007 UT). Limit magnitudes are 20.0, 17.2, and 15.0 mag in V-, J-, and Ks-band, respectively, using the USNO A2.0 and 2MASS catalog. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6314 SUBJECT: GRB 070419B optical afterglow candidate DATE: 07/04/19 15:19:16 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia P. Tristram (MOA, Univ. of Canterbury), A. J. Castro-Tirado, A. de Ugarte Postigo (IAA-CSIC Granada), A. Gilmore, P. Kilmartin (Univ. of Canterbury), J. Gorosabel, M. Jelínek and R. Cunniffe (IAA-CSIC Granada), report: "Following the detection by Swift of the GRB 070419B (Parson et al. GCNC 6305), we have obtained R & I -band images at the 0.6m B&C telescope at the Mt. John Observatory on Lake Tekapo, New Zealand. They were taken starting on Apr 19.537 UT (i.e. 2.17 hr post-burst). The single frames (360s in R) reveal a point-like source with R ~ 20 consistent with the Swift/XRT error box which is not present in the DSS-2 red. Preliminary coordinates (+/- 1") yield: AR(2000): 21:02:49.80 Dec(2000): -31:15:49.23 More details will be given on forthcoming GCN Circular." This message can be quoted. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6315 SUBJECT: GRB 070419A: Faulkes Telescope North Optical Observations DATE: 07/04/19 15:38:29 GMT FROM: James Smith at ARI,Liverpool John Moors U R.J. Smith, C.G. Mundell, S.N. Fraser, I.A. Steele, C.J. Mottram, A. Melandri, D.F. Bersier, M.F. Bode (Liverpool JMU), C. Guidorzi (Uni-Bicocca/INAF-OAB), A. Gomboc (Ljubljana), P. O'Brien, E. Rol, N. Bannister (U. Leicester) report on behalf of the RoboNet GRB collaboration The 2-m Faulkes North Telescope (Hawaii) reacted to the Swift burst GRB070419A (Stamatikos et al. GCN 6302). Observations were delayed by scheduled engineering work and only started about 37 min after the trigger time. BRi observations continued until 104min after the trigger. We detect the optical transient reported by Chornock et al (GCN 6304) in R and i' band filters and measure a power law decay index of ~ 1.5 throughout the hour of observation. UTC minutes_since_trigger Mag 10:49:46.5 50.36 g' > 19.8 (limit only) 10:51:20.8 51.91 r' = 20.37 10:53:07.9 53.70 i' = 20.22 Magnitudes are based on comparison with SDSS magnitudes of the adjacent star SDSS J121057.55+395539.9. The target has set and further observations are not currently ongoing with this telescope. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6316 SUBJECT: GRB 070419A: NAYUTA Optical Observation DATE: 07/04/19 16:21:08 GMT FROM: Ryo Iizuka at NHAO R. Iizuka, K. Matsuda, H. Naito and F. Tsumuraya report on behalf of NHAO. We observed the field of GRB 070419A (GCN 6302) with MINT on the 2.0-m NAYUTA telescope at Nishi-Harima Astronomical Observatory, Japan. We took images for a total of 100 sec in R-band filter on 2007 Apr 19 10:55 UT (56 minutes after the burst). The afterglow was detected with 20.1 mag relative to USNO-B stars. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6317 SUBJECT: GRB 070419A: SARA observations DATE: 07/04/19 17:31:41 GMT FROM: Adria C. Updike at Clemson U A. C. Updike, D. H. Hartmann (Clemson University) and K. Rumstay (Valdosta University) report on behalf of the Clemson GRB Follow-Up Team: We imaged the field of GRB 070419A (GCN 6302, Stamatikos et al.) beginning 54 minutes after the trigger (276205) with the SARA 0.9m at Kitt Peak under good weather conditions. In 16 minutes of stacked images, we see a faint object near our detection limit at the location of the afterglow (GCN 6304, Charnack et al.). We estimate the R-band magnitude to be 20 +/- 0.5 based on calibration to 5 USNO B1.0 stars. The Clemson University GRB Response Site may be found at: http://people.clemson.edu/~kgarime/burst/index.php The SARA Homepage can be found at: http://saraobservatory.org This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6318 SUBJECT: GRB070419 - SDSS Pre-Burst Observations DATE: 07/04/19 17:39:28 GMT FROM: Richard J. Cool at U.of AZ/Steward Obs Richard J. Cool (Arizona), Daniel J. Eisenstein (Arizona), David W. Hogg (NYU), Michael R. Blanton (NYU), David J. Schlegel (LBNL), J. Brinkmann (APO), Donald Q. Lamb (Chicago), Donald P. Schneider (PSU), and Daniel E. Vanden Berk (PSU) report: The Sloan Digital Sky Survey (SDSS) imaged the field of burst GRB070419 prior to the burst. As these data should be useful as a pre-burst comparison and for calibrating photometry, we are supplying the images and photometry measurements for this GRB field to the community. Data from the SDSS, including 5 FITS images, 3 JPGS, and 3 files of photometry and astrometry, are being placed at http://mizar.as.arizona.edu/~grb/public/GRB070419 We supply FITS images in each of the 5 SDSS bands of a 8'x8' region centered on the GRB position (ra=182.714 (12:10:51.4), dec=39.9080 (39:54:28.8); Swift-BAT TRIGGER 276205), as well as 3 gri color-composite JPGs (with different stretches). The units in the FITS images are nanomaggies per pixel. A pixel is 0.396 arcsec on a side. A nanomaggie is a flux-density unit equal to 10^-9 of a magnitude 0 source or, to the extent that SDSS is an AB system, 3.631e-6 Jy. The FITS images have WCS astrometric information. In the file GRB070419_sdss.calstar.dat, we report photometry and astrometry of 163 bright stars (r<20.5) within 15' of the burst location. The magnitudes presented in this file are asinh magnitudes as are standard in the SDSS (Lupton 1999, AJ, 118, 1406). Beware that some of these stars are not well-detected in the u-band; use the errors and object flags to monitor data quality. In the files GRB070419_sdss.objects_flux.dat and GRB070419_sdss.objects_magnitudes.dat, we report photometry of 415 objects detected within 6' of the GRB position. We have removed saturated objects and objects with model magnitudes fainter than 23.0 in the r-band. The fluxes listed in GRB070419_sdss.objects_flux.dat are in nanomaggies while the magnitudes listed in GRB070419_sdss.objects_magnitudes.dat are asinh magnitudes. All quantities reported are standard SDSS photometry, meaning that they are very close to AB zeropoints and magnitudes are quoted in asinh magnitudes. Photometric zeropoints are known to about 2% rms. None of the photometry is corrected for dust extinction. The Schlegel, Finkbeiner, and Davis (1998) predictions for this region are A_U=0.143 mag, A_g=0.105 mag, A_r = 0.076 mag, A_i=0.058 mag, and A_z=0.041 mag. The file GRB070419_sdss.spectro.dat contains a list of the 1 objects with SDSS spectroscopy within 6 arcminutes of the GRB position. In addition to the redshift and 1-sigma error for each object, this file also lists the object spectroscopic classification. SDSS astrometry is generally better than 0.1 arcsecond per coordinate. Users requiring high precision astrometry should take note that the SDSS astrometric system can differ from other systems such as those used in other notices; we have not checked the offsets in this region. More detailed information pertaining to our SDSS GRB releases can be found in our initial data release paper (Cool et al. 2006, PASP 118, 733). See the SDSS DR4 documentation for more details: http://www.sdss.org/dr5. These data have been reduced using a slightly different pipeline than that used for SDSS public data releases. We cannot guarantee that the values here will exactly match those in the data release in which these data are included. In particular, we expect the photometric calibrations to differ by of order 0.01 mag. This note may be cited, but please also cite the SDSS data release paper, Adelman-McCarthy et al. (2006, ApJS, 162, 38), when using the data or referring to the technical documentation. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6320 SUBJECT: GRB 070419A, Optical observations DATE: 07/04/19 19:36:25 GMT FROM: Shashi Bhushan Pandey at ARIES, INDIA S. B. Pandey, Rupak Roy and Saurabh Sharma (ARIES Nainital), on behalf of larger Indian GRB collaboration Optical afterglow candidate (GCN 6304) of GRB 070419A, localized by SWIFT (GCN 6302, trigger 276205), was monitored from ARIES Nainital, India using 1-m telescope in R_c and I_c filters around 4 hours after the burst. The total exposure given in R_c filter was 300sec*6 in good sky conditions. Photometry of the stacked R_c frame poses an upper limit of ~22 mag (around 4.3 hours after the burst) at the location of OT in comparison to nearby USNO-B1.0 star (GCN 6306). This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6321 SUBJECT: GRB 070419B: optical afterglow confirmation DATE: 07/04/19 20:08:51 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia A. de Ugarte Postigo, M. Jelínek (IAA-CSIC Granada), P. Tristram (MOA, Univ. of Canterbury), I. Bond (Massey Univ.), Ph. Yock (Univ. of Auckland), J. Hearnshaw (Univ. of Christchurch) and A. J. Castro- Tirado (IAA-CSIC), on behalf of a larger collaboration, report: "We have continued the BVRI optical monitoring of the proposed optical afterglow (Tristram et al. GCNC 6312) to GRB 070419B (Parson et al. GCNC 6305) with the 0.6m B&C telescope at the Mt. John Observatory on Lake Tekapo. We confirm the detection in the VRI -bands and a derive a complex lightcurve (preliminary analysis shows a steep decline up to T0 + 0.2 days and a plateau phase lasting until the end of our observations at T0 + 0.3 days with R ~ 21.0). A more accurated astrometry (+/- 0.5") yields: AR(2000): 21:02:49.78 Dec(2000): -31:15:48.8 A finding chart is posted at: http://www.iaa.es/~deugarte/GRBs/070419B/GRB070419B.gif Spectroscopic and photometric observations are encouraged." This message can be quoted. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6322 SUBJECT: GRB 070419: Keck/LRIS Absorption Redshift DATE: 07/04/19 21:54:28 GMT FROM: S. Bradley Cenko at Caltech S. B. Cenko, S. Gezari, T. Small (Caltech), D. B. Fox (Penn State), and E. Berger (Carnegie) report on behalf of a larger collaboration: We have obtained a spectrum of the optical afterglow of GRB070419A (Chornock et al., GCN 6304) with the Low-Resolution Imaging Spectrometer mounted on the 10-m Keck I telescope. Observations consisted of 2 x 900 s spectra taken at a mean epoch of approximately 11:36 19 April UT (~ 1.62 hr after the burst). We identify a single strong absorption system, including Mg II, Fe II, Mn II, and Fe I features, at a preliminary redshift of z = 0.97. Coupled with the lack of Lyman-alpha absorption down to ~ 3500 A, we consider this system is likely from the host galaxy of GRB070419A. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6323 SUBJECT: GRB 070419B: Swift XRT refined analysis DATE: 07/04/19 22:41:38 GMT FROM: Giulia Stratta at ASDC We have analyzed the first 3 orbits of Swift-XRT data on GRB 070419B (Parsons et al. GCN 6305), with a total exposure of 276 s in Windowed Timing (WT) mode and of 4.5 ks in Photon Counting (PC) mode. This provides a refined XRT position at RA,DEC=315.70654,-31.26381 which is: RA(J2000)=21 02 49.57 Dec(J2000)=-31 15 49.7 with an estimated error radius of 3.5 arcseconds (90% confidence). This position is 32 arcseconds from the BAT position (Parsons et al. GCN 6305), 1.2 arcseconds from the initial XRT position (Parsons et al. GCN 6305) and 3.0 arcseconds from the optical candidate (Tristram et al. GCN 6314). The 0.3-10 keV X-ray light curve presents a flaring behavior starting from 88 s up to about 350 s after the burst, with three flares. The second and third orbits data taken in PC mode show marginal evidence of a flat decay between 3.8 ks and 6.0 ks after the trigger, followed by a fading decay behavior that can be fit with a power law model with decay index 1.3+/-0.1 The X-ray spectrum from the XRT/WT data from 88 s to about 350 s can be fit by an absorbed power law with a photon index of 1.88+/-0.03 and a total column density of NH=(0.22+/-0.01)e22 cm**-2. We note that the Galactic column density in the direction of the source is 6.7e20 cm**-2 (Dickey & Lockmann 1990). Assuming the X-ray emission continues to decline at the same rate, we predict a 0.3-10.0 keV XRT count rate of 7.5e-2 count/s at T+24h and 3.1e-2 at T+48h. This circular is an official product of the Swift Team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6324 SUBJECT: GRB 070419A: RAPTOR Detection of Early Emission DATE: 07/04/19 23:42:20 GMT FROM: James Wren at LANL J. Wren, W.T. Vestrand, P.R. Wozniak, R. White, J. Pergande of Los Alamos National Laboratory report: Our Raptor telescopes responded to Swift trigger 276205 (Stamatikos et al., GCN 6302) at 10:00:49.8 UT, 83.7 s after the trigger and 7.8 s after receiving the GCN packet. We detect optical emission from the counterpart reported by the KAIT team (Chornock et al., GCN 6304). Our observations show that the counterpart brightened from below magnitude 18.8 to 18.44 (+- .15) at a mid-exposure time of 10:09:27.9 UT (60s duration). The counterpart then began a slow decline but remained detectable in our images until we interrupted our observing sequence at 10:47:17 UT for Swift trigger 276212. Our unfiltered images were calibrated using the R-band magnitudes from the USNO B1.0 catalog. This information is also being transmitted via VOEvent on the VOEventNet. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6325 SUBJECT: GRB070419B: Confirmation of Optical Transient DATE: 07/04/20 00:31:53 GMT FROM: Brian Schmidt at RSAA, ANU (MSSSO) B. Schmidt (ANU) and G. Mackie (Swinburne) report on behalf of a larger collaboration We have obtained R and I photometry of GRB070419B (Parson et al. GCN 6305) with the ANU 1m telescope + WFI at Siding Spring observatory. I images taken Apr 19.737-19.748 and R images taken at Apr 19.753-19.757 confirm the source of Tristram et al. (GCN 6312) at a position RA (2000): 21:02:49.82 DEC(2000): -31:15:49.3 with a position uncertainty +/- 0.1" referenced to the UCAC2 catalog. The R and I magnitudes are estimate to be ~ I=20.7, R=22.1 referenced to the UCAC2/2Mass star located at 21:02:59.34 -31:18:13.4 with mag ~I=14.75, R=15.25. This is significantly fainter than observed by Tristram et al., and suggests strongly that this object is associated with GRB07419B. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6326 SUBJECT: GRB 070419A Swift-BAT Refined Analysis DATE: 07/04/20 01:10:41 GMT FROM: Michael Stamatikos at GSFC M. Stamatikos (GSFC/ORAU), L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), J. Tueller (GSFC) on behalf of 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 070419A (trigger #276205) (Stamatikos, et al., GCN Circ. 6302). The BAT ground-calculated position is RA, Dec = 182.755, 39.903 deg which is RA(J2000) = 12h 11m 1.1s Dec(J2000) = 39d 54' 11.0" with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment). The coding fraction was 1. This position is ~1.5 arcmin from the position of the optical afterglow candidate reported by Chornock et al. (GCN Circ 6304), which was further confirmed by Cenko et al. (GCN Circ 6306). The mask-weighted light curve has a nearly symmetric, smooth profile, although a tail of emission extends to about T+160 sec. The T90 (15-350 keV) is ~116 +- 6 sec (estimated error including systematics). The time-averaged spectrum, from T-35 to T+93, is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.35 +- 0.25. The fluence in the 15-150 keV band is 5.6 +- 0.8 x 10^-7 erg/cm^2. The 1-sec peak photon flux measured from T-1.12 sec in the 15-150 keV band is 2.8 x 10^-2 ph/cm^2/sec. All the quoted errors are at the 90% confidence level. Under a Lambda Cold Dark Matter cosmological model, with Ho ~ 65 km/Mpc/s, Omega_M ~ 0.30, and Omega_Lambda ~ 0.70, the preliminary Keck absorption redshift of 0.97, reported by Cenko et al. (GCN Circ 6322), when coupled to the BAT fluence reported above, results in a preliminary isotropic energy emission estimate of ~ 1.60 x 10^+51 ergs in the 15-150 keV observed (30-296 keV GRB rest frame) band pass. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6327 SUBJECT: GRB 070419B, Swift-BAT refined analysis DATE: 07/04/20 02:39:09 GMT FROM: Ann M. Parsons at NASA/GSFC/Swift D. Palmer (LANL), L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), and J. Tueller (GSFC) on behalf of the Swift-BAT team: Using the data set from T-239.9 to T+602.1 sec from the recent telemetry downlink, we report further analysis of BAT GRB 070419 (trigger #276212) (Parsons, et al., GCN Circ. 6305). The BAT ground-calculated position is RA, Dec = 315.709, -31.266 deg which is RA(J2000) = 21h 2m 50.2s Dec(J2000) = -31d 15' 58.3" with an uncertainty of 1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 66%. The mask-weighted light curve exhibits 4 main peaks at ~T+0 s,T+25s, T+35s, and T+60s and its duration T90 (15-350 keV) is 236.5 +-12 sec (estimated error including systematics). The time-averaged spectrum from -11.7 to 314.8 s is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.70 +- 0.05. The fluence in the 15-150 keV band is 7.5 +- 0.2 x 10^-6 erg/cm2.The 1-sec peak photon flux measured from T-0.28 sec in the 15-150 keV band is 1.4 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6328 SUBJECT: GRB 070419A: Early Super-LOTIS Observations DATE: 07/04/20 04:03:14 GMT FROM: Grant Williams at Steward Observatory G. G. Williams (MMTO) and P. A. Milne (Steward Observatory), on behalf of the Super-LOTIS Collaboration, report: The robotic 0.6-m Super-LOTIS telescope began observing the error box of GRB 070419A (Swift Trigger 276205, Stamatikos et al. GCN 6302) at 10:01:08.1 UT, 102 seconds after the trigger. Our initial observations include 5 x 10s exposures, 5 x 20s exposures, and 30 x 60s exposures, all in the R-band. We detect the afterglow reported by Chornock et al. (GCN 6304) in our third (and subsequent) 60 second exposure which began at 10:07:01.8 UT, 456 seconds after the trigger. We do not detect the afterglow in early single exposures or early summed exposures. This is evidently related to the brightening reported by Cenko et al. & Wren et al. (GCN 6306 & 6324). Using the USNO-B star at RA=12:10:57.57, Dec=+39:55:40.2 with R=15.22 (Cenko et al. GCN 6306), we calculate the following R-band magnitudes and 5-sigma upper limits: t_start (UT) exp t_tot (s) Nsum t_start-t_0 (s) R Mag ---------------------------------------------------------------- 10:01:08.1 10 1 102 R > 17.71 10:01:08.1 50 5 102 R > 18.58 10:02:33.1 20 1 187 R > 18.24 10:02:33.1 100 5 187 R > 19.19 10:04:47.9 60 1 322 R > 18.60 10:07:01.8 60 1 456 R = 18.49 +/- 0.22 Additional observations followed our initial set and analysis are ongoing. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6329 SUBJECT: GRB 070419A: MITSuME Okayama Observations DATE: 07/04/20 06:48:04 GMT FROM: Michitoshi Yoshida at Okayama Astrophysical Obs M. Yoshida, K. Yanagisawa, Y. Shimizu, S. Nagayama (OAO, NAOJ) and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We performed optical imaging observation (g', Rc, and Ic) of the field of GRB 070419A (Stamatikos et al. GCN 6302) with 50cm MITSuME telescope at Okayama Astrophysical Observatory from UT 10:53 to UT 13:06 on Apr.19 2007. We coadded 106 CCD frames for each band. Exposure time of each frame is 1 minute. We made flux calibration using a USNO B1.0 star close to the XRT position (12:10:57.57, +39:55:40.2, B=16.14, R=15.22, I=14.37; see Williams et al. GCN 6328, Cenko et al. GCN 6306). We detected a faint source in g' band at the position of the optical transient reported by Chornock et al. (GCN 6304). The g' band magnitude and three sigma limiting magnitudes for Rc and Ic bands of this source are listed below. --------------------------------------------------------------- band mid-UT exp.time brightness g' Apr. 19 12:00 106 x 1 min. 20.9 +- 0.2 mag Rc Apr. 19 12:00 106 x 1 min. > 21.5 mag (upper limit) Ic Apr. 19 12:00 106 x 1 min. > 19.4 mag (upper limit) --------------------------------------------------------------- //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6333 SUBJECT: GBR 070419A: Swift/XRT refined analysis DATE: 07/04/20 12:09:03 GMT FROM: Matteo Perri at ISAC/ASDC M. Perri, G. Stratta (ASDC), P.A. Evans, M.R. Goad (LU), D.N. Burrows (PSU) and M. Stamatikos (GSFC/ORAU) report on behalf of the Swift/XRT team: We have analysed the first 5 orbits of Swift XRT data on the BAT GRB 070419A (Stamatikos et al., GCN Circ. 6302, GCN Circ. 6326). Using a 0.9 ks Photon Counting mode image we find an astrometrically corrected refined XRT position (by matching the UVOT images with the USNO-B1 catalogue) at RA, DEC=182.74480, 39.92567, which is: RA(J2000) = 12h 10m 58.80s Dec(J2000) = +39d 55' 32.4" with an uncertainty of 2.2" (90% containment). This is 1.4' away from the centre of the refined BAT position (Stamatikos et al. GCN Circ. 6326), 5.4" away from the initial XRT position (Stamatikos et al., GCN Circ. 6302) and 1.5" away from the optical position (Chornock et al., GCN Circ. 6304). The 0.3-10 keV X-ray light curve during the first orbit from T+120s up to about T+1ks shows a rapid decay. Starting from T+1ks (last bin of first orbit) to T+46ks the curve is well fit by a power-law decline with a decay index of -1.4 (+0.2)(-0.4). The X-ray spectrum covering the time period from T+120s to T+310s is well fit by an absorbed power-law with a photon index of 2.46+/-0.09 and column density of (1.9+/-0.2)e21 cm**-2. We note the Galactic column density in the direction of the source is 2.0e20 cm**-2. The observed 0.3-10 keV flux for this spectrum is 2.1e-9 erg/cm**2/s. Assuming the X-ray emission continues to decline at the same rate, we predict a 0.3-10 keV XRT count rate of 3e-4 count/s at T+24hr, which corresponds to an observed 0.3-10 keV flux of about 3e-14 erg/cm**2/s. This circular is an official product of the Swift XRT Team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6339 SUBJECT: GRB 070419A: MARGE Observations DATE: 07/04/20 19:12:03 GMT FROM: Heather Swan at U.of Michigan/ROTSE H. Swan (U Mich), I. Smith (Rice), C. Akerlof (U Mich), E. Rykoff (U Mich), and M. Skinner (Boeing) report on behalf of the MARGE collaboration: The AEOS Burst Camera (ABC) on the AEOS telescope, located at the Maui Space Surveillance System on Haleakala, observed the fading counterpart to GRB070419A (Swift trigger 276205 (GCN 6302)). The images are unfiltered 10s exposures which started at 10:57:41 UT (~58 minutes after the trigger) and ended at 11:53:52 UT. After coadding our images in sets of 10, we detect the OT first identified by Chornock et al (GCN 6304). A preliminary analysis gives a magnitude of approximately 20.5+/-0.2 at a mid time of 10:59:11 UT. Using the SDSS data provided by Cool et al. (GCN 6318), we calibrate the OT to the r band magnitude of the nearby 20.434 mag star located at (J2000) RA = 182.73852, DEC = 39.93033. We find that the ABC data fades as a power law decay with index ~-1.1, consistent with the detections reported by Nishiura et al. (GCN 6308), Smith et al. (GCN 6315), Updike et al. (GCN 6317), Iizuka et al. (6317) (prior the ABC observations) and Fu et al. (GCN 6311) (after the ABC observations). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6340 SUBJECT: GRB070419a: Swift UVOT observations DATE: 07/04/20 21:57:46 GMT FROM: Wayne Landsman at GSFC/SSAI W. Landsman and M. Stamatikos (NASA/GSFC) report on behalf of the Swift/UVOT team The Swift/UVOT began settled observations of GRB 070419A 115 seconds after the BAT trigger (Stamatikos et al., GCN 6302). The afterglow first detected by Chornock et al. (GCN 6304) is weakly detected on the UVOT V-band image. Photometry is difficult due to the presence of a diffraction spike from a 7th magnitude star 3' distant. The bright star also precluded use of the UVOT broad-band white filter. Estimated magnitudes and 3-sigma upper limits are given below: Filter Start(s) End(s) Exposure(s) Magnitude ----------------------------------------------------------------- V 115 515 394 20.2 ± 0.3 V 869 1204 330 20.0 ± 0.3 B 594 739 19 >18.7 U 569 861 58 >19.1 The magnitudes are not corrected for the Galactic reddening of E(B-V)=0.03 The V band magnitudes are consistent with a brightening noted in previous reports (Williams et al. 6328, Wren et al. 6324, Cenko et al. 6306). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6341 SUBJECT: GRB070419A: Kuiper Optical detection DATE: 07/04/20 23:23:49 GMT FROM: Peter A. Milne at Super-LOTIS P.A. Milne and G.G. Williams (U Arizona) report on behalf of the Super-LOTIS team: The 1.54m Kuiper telescope began R and V-band observations of the error region of GRB070419A (Swift trigger 276205) at 10:26:37 UT, 27 minutes after the burst. The OT detected by Chornock et al. (GCN 6304) and observed by Cenko et al., Urata et al., Rol et al., Smith et al., Updike et al., Wren et al., Williams et al., Yoshida et al., Swan et al. (GCN 6306/6322, 6308/6311, 6309, 6315, 6317, 6324, 6328, 6329, 6339) is clearly visible in the first image and all subsequent images until 11:36:36 UT. We used the USNO-B star at RA=12:10:57.57, Dec=+39:55:40.2 to derive the R and V magnitudes. For the R-band magnitude, we use R=15.22 (Cenko et al. GCN 6306). For the V-band magnitude, we used the g=15.866 and r=15.447 magnitudes from Cool et al. (GCN 6318), and derived a V magnitude of V=15.61 using the transformation equations of Jester et al. (2005). The R-band magnitude of the afterglow in the first image is: UT Time delta Time R magnitude error 10:26:37 60.0 s 19.12 0.09 The V-band magnitude of the afterglow in the first V-band image is: UT Time delta Time V magnitude error 10:35:35 60.0 s 19.66 0.14 This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6348 SUBJECT: GRB070419B: Suzaku WAM observation of the prompt emission DATE: 07/04/25 03:33:11 GMT FROM: Kazutaka Yamaoka at Aoyama Gakuin U T. Enoto, R. Miyawaki, K. Nakawaza, K. Makishima (Univ. of Tokyo), Y. E. Nakagawa, S. Sugita, K. Yamaoka (Aoyama Gakuin U.), M. Ohno, T. Takahashi, T. Uehara, C. Kira, Y. Fukazawa (Hiroshima U.), Y. Urata, K. Onda, M. Suzuki, K. Morigami, N. Kodaka, M. Tashiro (Saitama U.), M. Suzuki, T. Tamagawa, Y. Terada (RIKEN), S. Hong (Nihon U.), M. Kokubun, T. Takahashi (ISAS/JAXA), E. Sonoda, M. Yamauchi (Univ. of Miyazaki), and the Suzaku WAM team report: The long GRB 070419B (Swift/BAT trigger #276212 ; Parsons et al., GCN 6305; Palmer et al., GCN 6327), was detected at 10:44:01 UT (=T0) by the Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV. The observed light curve shows two separate peak structures with a duration (T90) of about 71 seconds. The fluence in 100-1000 keV was (1.1 +/-0.2) X 10^-5 erg/cm^2. The 1-s peak flux was 0.9 +/-0.1 photons/cm^2/s in the same energy range. Preliminary result shows that time-averaged spectrum from T0-5 to T0+83 sec is well fitted by a single power law with a photon index of 1.7 +/-0.2. All the quoted errors are at statistical 90% confidence level, in which the systematic uncertainties are not included. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6406 SUBJECT: GRB 070419A, Deep LBT photometry DATE: 07/05/10 22:17:25 GMT FROM: Peter Garnavich at U of Notre Dame P. Garnavich (Notre Dame), X. Fan, (U Ariz), X. Dai, J. Prieto, K. Z. Stanek (Ohio State), J. Hill (LBTO/UAz), J. Bechtold (U Ariz), R. M. Wagner (LBTO/OSU), J. Rhoads (Ariz State) report: The Large Binocular Telescope (LBT) imaged the position of the GRB 070419A afterglow (Stamatikos et al, GCN 6302; Chornock et al. GCN 6304) with the LBC-blue CCD camera (http//lbc.mporzio.astro.it) and 8.4-m SX mirror on 2007 April 23.15 (UT). Ten dithered, 200 second exposures were obtained with the Sloan-r filter in 1.2" seeing. The combined image shows a faint source at J2000 12:10:58.80 39:55:33.71 +/-0.2 arcsec which is coincident with the Chornock et al. coordinates. Assuming the star at RA = 182.73852, DEC = 39.93033 J2000 has a Sloan r MODEL magnitude of 20.394 mag (Swan et al. GCN 6339; Cool et al. GCN 6318), we find the source at the position of the afterglow to be r=24.75 +/- 0.18 mag at 3.7 days after the burst. Observations less than an hour after the burst by Smith et al. (GCN 6315) and Swan et al. (GCN 6339) compared with our photometry imply a power-law decay index of 0.9+/-0.1 over nearly 4 days. This is consistent with the initial decline index of 1.1 (Swan et al. GCN 6339) and suggests that either no break in the light curve had occurred or the host galaxy is contributing to the measured LBT flux. The LBT image can be found at: http://www.nd.edu/~pgarnavi/grb070419a/grb070419a_LBT.jpg The LBT is an international collaboration among institutions in the United States, Italy and Germany. The LBT Corporation partners are: * The University of Arizona on behalf of the Arizona university system * Istituto Nazionale di Astrofisica, Italy * LBT Beteiligungsgesellschaft, Germany, representing the Max Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University * The Ohio State University * The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota and University of Virginia This message may be cited //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6407 SUBJECT: GRB070419A: optical observations DATE: 07/05/13 20:24:58 GMT FROM: Alexei Pozanenko at IKI, Moscow A. Pozanenko (IKI), A. Shulga, A. Volnova (SAI MSU), B. Hafizov, I. Asfandiyarov, M. Ibrahimov (MAO) on behalf of larger GRB follow up collaboration report: We observed optical afterglow of GRB070419A (Stamatikos et al, GCN 6302; Chornock et al. GCN 6304) with 1.5m telescope of Maidanak observatory (MAO). Several exposures in R-band in seeing ~1 arcsec were obtained on Apr. 17 between (UT) 15:20 - 16:25. In a combined image the source at (J2000) RA= 12 10 58.83 DEC= +39 55 34.06 with an error in both coordinates of 0.15" is compatible with the coordinates of Chornock et al. (GCN 6304) and Garnavich et al. (GCN 6406). A photometry of the afterglow using USNO-A2.0 stars is following: T0+ , Exposure, R_mag 0.245 d 11x300 s 22.4 +/- 0.3 Our observation is compatible with global power law decay index 0.9 (Garnavich et al. GCN 6406) suggesting no host galaxy contribution in epoch of our observation. The combined image can be found at http://grb.rssi.ru/GRB070419A/GRB070419A_AZT22_R.jpg This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6486 SUBJECT: GRB 070419A, deep LBT photometry and possible supernova detection DATE: 07/06/04 18:36:29 GMT FROM: Peter Garnavich at U of Notre Dame J. Hill (LBTO/UAz), P. Garnavich (Notre Dame), O. Kuhn (LBTO/UAz), N. Bouche, P. Buschkamp (MPE), X. Fan, (U Ariz), X. Dai, J. Prieto, K. Z. Stanek (Ohio State), P. Milne, J. Bechtold (U Ariz), R. M. Wagner (LBTO/OSU), J. Rhoads (Ariz State) report: The Large Binocular Telescope (LBT) continued to image the position of the GRB 070419A afterglow (Stamatikos et al, GCN 6302; Chornock et al. GCN 6304; Garnavich et al. GCN 6406) with the LBC-blue CCD camera (http//lbc.mporzio.astro.it) and 8.4-m SX mirror. Data were obtained 2007 May 10.18 (UT) and May 20.22 (UT) which are 20.8 and 30.8 days after the burst. Using the calibration assumed by Garnavich et al. (GCN 6406), we estimate the brightness of the source at the position of the afterglow using point-spread-function fitting photometry as follows: UT Date Age (days) Exposures Seeing r mag Error ----------------------------------------------------------- Apr 23.15 3.7 10x200s 1.2" 24.75 0.18 (GCN 6406) May 10.18 20.8 25x200s 0.96" 25.29 0.05 May 20.22 30.8 15x200s 0.73" 25.71 0.13 The decay between 4 days (LBT observation from GCN 6406) and 20 days after the burst is very slow and corresponds to a power-law index of 0.3. This could indicate host galaxy contamination, but the images remain unresolved. Extrapolating the decline to 30 days post-burst predicts the afterglow should be 30% brighter than the actual observed magnitude. This increased fading rate is inconsistent with a host galaxy dominating the flux and suggests light from a GRB progenitor supernova may be powering the late-time light curve. The Sloan-r filter has an effective wavelength of 623 nm which maps to a rest-frame UV wavelength near 316 nm at a redshift of 0.97 (Cenko et al. GCN 6322). The U-band light curve of SN 1998bw peaked 13 to 15 days after GRB 980425 (Galama et al. 1998, Nature, 395, 670) and possibly earlier at short wavelengths. Some supernovae associated with GRB such as SN 2001dh/011121 (Garnavich et al. 2003, ApJ, 582, 924) and 2006aj/060218 (Modjaz et al. 2006, ApJ, 645, 21) have peaked earlier than SN 1998bw, so the decay seen at 16 rest-frame days is consistent with a supernova interpretation. Extrapolating the spectrum of SN 1998bw near maximum (Patat et al. 2001, ApJ, 555, 900) out to UV wavelengths, we estimate a peak brightness of R=25.4 when viewed at z=0.97, which is also consistent with the LBT observations. A plot of the light curve can be found at: http://www.nd.edu/~pgarnavi/grb070419a/grb070419a_lc.jpg The LBT is an international collaboration among institutions in the United States, Italy and Germany. The LBT Corporation partners are: * The University of Arizona on behalf of the Arizona university system * Istituto Nazionale di Astrofisica, Italy * LBT Beteiligungsgesellschaft, Germany, representing the Max Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University * The Ohio State University * The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota and University of Virginia This message may be cited