Gamma-ray Burst 130606B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN Circular #14795
G. Vianello (Stanford University), J. Racusin (NASA/GSFC), Nicola Omodei (Stanford University) and M. Ohno (Hiroshima U.) report on behalf of the Fermi-LAT team:
At 11:55:33 UT on 06 June 2013, Fermi LAT detected high energy emission from GRB 130606B, which was also detected by Fermi-GBM (trigger 392212536 / 130606497). The brightness of the event in GBM triggered an autonomous repoint of the spacecraft. Unfortunately, the GBM flight software determined an unreliable position and the spacecraft slewed to that position.
We were nevertheless able to detect a very clear excess at the position:
(RA, Dec) = 218.574, -22.131 (J2000) with an error radius of 0.1 deg (68% containment radius, statistical errors only)
which was within the LAT field of view between T0 + 180 s and T0 + 1000 s. Using SOURCE class we detected > 10 events, with 4 events above 1 GeV, compatible with the position of the source during this time interval.
This source was about 91 deg from the LAT boresight at the time of the trigger and during the whole prompt emission (~100 s long), well outside the nominal field of view for the standard data analysis. However, we detected a strong signal using the non-standard LLE selection, most sensitive in the 10 MeV - 100 MeV energy range and featuring a broader acceptance. We detected an excess of more than 17 sigma in a time interval from 5 to 30 s after the trigger, composed of few hundreds events above the background level. The effective area of the LLE class is small at such high off-axis angle, therefore the strong excess indicates that this burst was exceptionally bright and hard.
A Swift TOO request has been submitted.
A GBM circular is forthcoming.
The Fermi LAT point of contact for this burst is Giacomo Vianello ( giacomov@stanford.edu).
The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
GCN Circular #14801
Subject: GRB 130606B: Fermi GBM observation
Hoi-Fung Yu (MPE) reports on behalf of the Fermi GBM Team:
"At 11:55:33.63 UT on 6 June 2013, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 130606B (trigger 392212536 / 130606497). The GBM on-ground location is consistent with the LAT position (Vianello et al., GCN 14795). The angle from the Fermi LAT boresight is 93 degrees.
The high peak flux from the GRB caused GBM to issue an autonomous rapid repoint (ARR) maneuver but to an unreliable sky position according to the flight software calculation.
This burst was also independently detected by INTEGRAL SPI-ACS.
The GBM light curve shows a multi-peaked feature with a duration (T90) of about 52 s (50-300 keV). The time-averaged spectrum from T0+0.003 s to T0+65.537 s is well fit by a Band function with Epeak = 435 +/- 11 keV, alpha = -1.14 +/- 0.01, and beta = -2.05 +/- 0.02.
The event fluence (10-1000 keV) in this time interval is (2.034 +/- 0.007)E-04 erg/cm^2. The 1.024 s peak photon flux measured starting from T0+9.15 s in the 10-1000 keV band is 62.14 +/- 0.58 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN Circular #14803
S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, report:
The long-duration intense hard-spectrum GRB 130606B (Fermi-LAT detection: Vianello et al., GCN 14795; Fermi-GBM detection: Yu, GCN 14801) triggered Konus-Wind at T0=3D42940.544s UT (11:55:40.544).
The light curve shows a bright hard pulse complex from ~T0 to ~T0+70 s, followed by a weak soft tail of emission out to ~T0+100s. The emission at the main phase is seen up to ~17 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB130606_T42940/ Periodic `dips' visible in the 64-ms light curve are due to the source occultation by the spacecraft.
As observed by Konus-Wind, the burst had a fluence of (4.3 =B1 0.1)x10-4 erg/cm2, and a 64-ms peak flux, measured from T0+8.064s, of (5.7 =B1 0.3)x10-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+67.328 s) is best fit in the 100 keV - 18 MeV range by the GRB (Band) function with the following model parameters: the low-energy photon index alpha =3D -1.25 =B1 0.15, the high energy photon index beta =3D -1.92 =B1 0.02, the peak energy Ep =3D 337 =B1 59 keV, chi2 =3D 120/81 dof.
The spectrum at the maximum count rate (measured from T0+7.680 to T0+8.704 s) is best fit in the 50 keV - 18 MeV range by the GRB (Band) function with the following model parameters: the low-energy photon index alpha =3D -0.92 =B1 0.18, the high energy photon index beta =3D -1.87 =B1 0.10, the peak energy Ep =3D 690 =B1 240 keV, chi2 =3D 96/90 dof.
All the quoted results are preliminary.
GCN Circular #14820
J. A. Kennea (PSU) reports on behalf of the Swift-XRT team:
We have analysed 3.1 ks of XRT data for the Fermi/LAT-detected burst: GRB 130606B, from 106.6 ks to 114.1 ks after the Fermi/LAT trigger. The data are entirely in Photon Counting (PC) mode. An X-ray source is detected within the Fermi/LAT error circle. Using 2899 s of PC mode data and 4 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 218.52931, -22.10229 which is equivalent to:
```
RA (J2000): 14h 34m 07.04s
Dec(J2000): -22d 06' 08.2"
```
with an uncertainty of 1.8 arcsec (radius, 90% confidence). This position is 181 arcsec from the Fermi/LAT position. the light curve is consistent with a constant source of mean count rate 8.0e-02 ct/sec.
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.3 (+/-0.4). The best-fitting absorption column is 2.0 (+1.0, -0.9) x 10^21 cm^-2, in excess of the Galactic value of 6.7 x 10^20 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.3 x 10^-11 (5.6 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     2.0 (+1.0, -0.9) x 10^21 cm^-2
Galactic foreground: 6.7 x 10^20 cm^-2
Excess significance: 2.5 sigma
Photon index:	     2.3 (+/-0.4)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00020283.
This circular is an official product of the Swift-XRT team.
GCN Circular #14822
Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB) J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UCSC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jos=E9 A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes=FAs Gonz=E1lez (UNAM), Carlos Rom=E1n-Z=FA=F1iga (UNAM), Neil Gehrels= (GSFC), and Harvey Moseley (GSFC) report:
We observed the field of GRB 130606B (Vianello et al., GCN Circular 14795) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astron=F3mico Nacional on Sierra San Pedro M=E1rtir from 2013/06 7.16 to 2013/06 7.25 UTC (15.97 to 18.08 hours after the BAT trigger), obtaining a total of 0.36 hours exposure in the r' and i' bands and 0.30 hours exposure in the Y and H bands.
For a source within the XRT error circle (Kennea et al., GCN Circular 14820), in comparison with USNO-B1 and 2MASS, we obtain the following 3-sigma upper limits:
```
r'    > 23.59
i'    > 23.61
Y     > 21.52
H     > 20.73
```
These magnitudes are in the AB system and not corrected for Galactic extinction in the direction of the GRB.
No further observations are planned.
We thank the staff of the Observatorio Astron=F3mico Nacional in San Pedr= o=20 M=E1rtir.
GCN Circular #14823
M. Marisaldi, F. Fuschino (INAF/IASF-Bo), F. Verrecchia, C. Pittori (ASDC and INAF/OAR), A. Giuliani (INAF/IASF-Mi), F. Longo (University of Trieste and INFN Trieste), F. Lucarelli (ASDC and INAF/OAR), E. Del Monte, F. Lazzarotto, I. Donnarumma, Y. Evangelista, M. Feroci, L. Pacciani, P. Soffitta, E. Costa, I. Lapshov, M. Rapisarda (INAF/IAPS Rome), G. Barbiellini, (INFN Trieste), A. Bulgarelli, F. Gianotti, M. Trifoglio, G. Di Cocco, C. Labanti, V. Fioretti, M. Galli (INAF/IASF-Bo), A. Chen, S. Mereghetti, F. Perotti, P. Caraveo (INAF/IASF-Mi), M. Cardillo, E. Striani, M. Tavani (INAF/IAPS Rome, and Univ. Roma Tor Vergata), A. Argan, G. Piano, S. Sabatini, V. Vittorini (INAF/IAPS Rome), G. Pucella (ENEA Frascati), A. Pellizzoni, A. Trois (INAF/OA Cagliari), M. Pilia (ASTRON), S. Vercellone (INAF/IASF-Pa), P. W. Cattaneo, A. Rappoldi (INFN Pavia), A. Morselli, P. Picozza (INFN Roma-2), M. Prest, E. Vallazza (Universita` dell'Insubria), S. Colafrancesco (INAF/OAR and WITS), P. Lipari, D. Zanello (INFN Roma-1), P. Giommi (ASI), and G. Valentini (ASI), on behalf of the AGILE Team, report:
"The long hard bright GRB 130606B, observed in gamma-rays by Fermi-LAT (Vianello et al., GCN 14795), Fermi-GBM (Yu et al., GCN 14801) and Konus-Wind (Golenetskii et al., GCN 14803), triggered AGILE-MCAL, sensitive in the range 0.4 - 100 MeV, at 11:55:33 UT (T0).
The light curve above 400 keV shows three main peaks between T0 and T0 + 20 s, followed by two less bright peaks at T0 + 40 s and T0 + 50 s. The time-integrated spectrum measured between T0 and T0 + 20 s can be fit in the energy range 0.5 - 20 MeV with a simple power law with photon index -2.15 +/- 0.03 and reduced chi-squared 1.67 (46 d.o.f). As observed by MCAL the burst fluence in the same energy range and time interval is (1.62 +/- 0.05)E-04 erg/cm^2. All quoted errors are at 90% confidence levels.
The burst was 118 degrees off-axis with respect to the AGILE GRID pointing direction at T0, from a sky region not accessible to the GRID. This measurement was obtained with AGILE observing a large portion of the sky in spinning mode."
GCN Circular #14855
C. A. Swenson (PSU) and D. Kocevski (NASA/GSFC/ORAU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 130606B 106.6 ks after the Fermi/LAT trigger (Vianello et al., GCN 14795). No optical afterglow consistent with the position of the potential X-ray candidate (Kennea, GCN 14820) is detected in the UVOT exposures. A preliminary 3- sigma upper limit using the UVOT photometric system (Breveld et al., 2011, AIP Conf. Proc. 1358, 373) for the initial exposures is:
```
Filter       T_start(s)     T_stop(s)       Exp(s)     Mag
------       ----------     ---------       ------     ---
White          106556        123017          4142     >22.6
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.10 in the direction of the burst (Schlegel et al. 1998)
GCN Circular #14892
Y. Ishida, M. Tashiro, Y. Terada, T. Yasuda, H. Ueno, S. Sugimoto (Saitama U.), M. Ohno, K. Takaki, T. Kawano, R. Nakamura, S. Furui, Y. Fukazawa (Hiroshima U.), M. Yamauchi, N. Ohmori, M. Akiyama (Univ. of Miyazaki), K. Yamaoka (Nagoya U.), S. Sugita (Ehime U.), Y. E. Nakagawa, M. Kokubun, T. Takahashi (ISAS/JAXA), W. Iwakiri (RIKEN), Y. Hanabata (ICRR), Y. Urata (NCU), K. Nakazawa, K. Makishima (Univ. of Tokyo) on behalf of the Suzaku WAM team, report:
The bright, long GRB 130606B (Fermi-LAT detection: G. Vianello, et al . 14795) triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at UT 11:55:35.360(=T0).
The observed light curve shows a multi-peaked structure starting at T0-3.5 s, ending at T0+63 s with a duration (T90) of about 43.7 seconds. The fluence in 100 - 1000 keV was 1.33 (-0.73, +0.02) *10^-4 erg/cm^2. The 1-s peak flux measured from T0+11.5 s was 20.64 (-4.72, +0.51) photons/cm^2/s in the same energy range.
Preliminary result shows that the time-averaged spectrum from T0-3 s to T0+63 s is well fitted by a GRB Band model as follows. the low-energy photon index alpha: -1.24 (-0.31, +0.79), the high-energy photon index beta: -2.08 (-0.16, +0.11), and the peak energy Epeak: 619 (-251, +396) keV, (chi^2/d.o.f = 17.1/13).
Due to the brightness of this burst, a 3% systematic error was added for low energy channels. All the quoted errors are at statistical 90% confidence level.
The light curves for this burst are available at: http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html
1501.0508 from 22 Jan 15
Yunguo Jiang et al.: GRB Spectra in the complex of synchrotron and Compton processes
Under the steady state condition, the spectrum of electrons is investigated by solving the continuity equation under the complex radiation of both the synchrotron and Compton processes. The resulted GRB spectrum is a broken power law in both the fast and slow cooling phases. On the basis of this electron spectrum, the spectral indices of the Band function in four different phases are presented. In the complex radiation frame, the detail investigation on physical parameters reveals that both the reverse shock photosphere model and the forward shock with strong coupling model can answer the $\alpha \sim -1$ problem. A possible marginal to fast cooling phase transition in GRB 080916C is discussed. The time resolved spectra in different pulses of GRB 100724B, GRB 100826A and GRB 130606B are investigated. We found that the flux is proportional to the peak energy in almost all pulses. The phases for different pulses are determined according to the spectral index revolution. We found the strong correlations between spectral indices and the peak energy in GRB 100826A, which can be explained by the Compton effect in the fast cooling phase. However, the complex scenario predicts a steeper index for the injected electrons, which challenges the acceleration mechanism in GRBs.
1505.05858 from 22 May 15
Bin-Bin Zhang et al.: Synchrotron Origin of the Typical GRB Band Function - A Case Study of GRB 130606B
We perform a time-resolved spectral analysis of GRB 130606B within the framework of a fast-cooling synchrotron radiation model with magnetic field strength in the emission region decaying with time, as proposed by Uhm & Zhang. The data from all time intervals can be successfully fit by the model. The same data can be equally well fit by the empirical Band function with typical parameter values. Our results, which involve only minimal physical assumptions, offer one natural solution to the origin of the observed GRB spectra and imply that, at least some, if not all, Band-like GRB spectra with typical Band parameter values can indeed be explained by synchrotron radiation.

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