GRB 130427A: A Nearby Ordinary Monster
MASELLI, Alessandro1, MELANDRI, Andrea1, NAVA, Lara1/2, MUNDELL, Carole G.3, KAWAI, Nobuyuki4/5
CAMPANA, Sergio1, COVINO, Stefano1, CUMMINGS, Jay R.6, CUSUMANO, Giancarlo1, EVANS, Philip A.7
GHIRLANDA, Giancarlo1, GHISELLINI, Gabriele1, GUIDORZI, Cristiano8, KOBAYASHI, Shiho3, KUIN, Paul M.9
LA PAROLA, Valentina1, MANGANO, Vanessa1/10, OATES, Samantha R.9, SAKAMOTO, Takanori11
SERINO, Motoko5, VIRGILI, Francisco3, ZHANG, Bin-Bin10, BARTHELMY, Scott D.12, BEARDMORE, Andrew P.7
BERNARDINI, Maria G.1, BERSIER, David3, BURROWS, David N.10, CALDERONE, Giorgio1/13
CAPALBI, Milvia1, CHIANG, James14, D'AVANZO, Paolo1, D'ELIA, Valerio1/15, DE PASQUALE, Massimiliano9
FUGAZZA, Dino1, GEHRELS, Neil12, GOMBOC, Andreja16/17, HARRISON, Richard M.3
HANAYAMA, Hidekazu18, JAPELJ, Jure16, KENNEA, Jamie A.10, KOPAC, Drejc16, KOUVELIOTOU, Chryssa12
KURODA, Daisuke18, LEVAN, Andrew J.19, MALESANI, Daniele20, MARSHALL, Francis E.12, NOUSEK, John A.10
O'BRIEN, Paul T.7, OSBORNE, Julian P.7, PAGANI, Claudio7, PAGE, Kim L.7, PAGE, Matthew9
PERRI, Matteo1/15, PRITCHARD, Tyler A.10, ROMANO, Patrizia1, SAITO, Yoshihiko4, SBARUFATTI, Boris1/10
SALVATERRA, Ruben1, STEELE, Iain3, TANVIR, Nial R.7, VIANELLO, Giacomo14, WIEGAND, Robert E.12
WIERSEMA, Klaas7, YATSU, Yoichi4, YOSHII, Taketoshi4, TAGLIAFERRI, Gianpiero1

1: Istituto Nazionale di Astrosica, 2: Astroparticle and Cosmology Laboratory, 3: Liverpool John Moores University, 4: Tokyo Institute ofTechnology, 5: RIKEN, 6: University of Maryland/NASA, 7: University of Leicester, 8: University of Ferrara, 9: University College London,
10: Pennsylvania State University, 11: Aoyama Gakuin University, 12: NASA, 13: Universita di Milano-Bicocca, 14: SLAC National Accelerator
Laboratory/Stanford University, 15: Agenzia Spaziale Italiana, 16: University of Ljubljana, 17: Centre of Excellence Space-si, 18: NAOJ, 19:
University of Warwick, 20: University of Copenhagen

The long-duration gamma-ray burst GRB 130427A,
detected on 27 April 2013, is the most powerful GRB(gamma-ray burst) at z < 0.9 with the luminosity of L ~ 3× 1053 erg s−1 and the redshift of z = 0.34. We performed
multiwavelength observations with the Swift satellite
and ground-based facilities (Liverpool telescope, Faulkes
Telescope North, and MITSuME Telescopes) just after
the trigger event, and studied the X-ray, UV, and opticallight curves and spectral energy distributions, including
γ-ray and radio data [1].
GRB 130427A was also detected by the Fermi
Gamma-ray Burst Monitor (GBM) aboard the Fermi
Gamma-ray Space Telescope, and the high energy γ-rayemission with the most energetic photon at 95 GeV wasdetected for 20 hours [2]. The Burst Alert Telescope(BAT) onboard the Swift satellite observed the highest
fluence for a GRB with a total fluence of 4.985 ± 0.002
× 10−4 erg cm−2 in the 15 – 150 keV band. In the X-ray
light curve, a break at 424 ± 8 s is detected between an
initially steep decay with index α0,x = 3.32 ± 0.17 anda flatter decay with index α1,x = 1.28 ± 0.01 (see Figure1). Then we found that a further break at 48 ± 22 ks isneeded to interpret a further steep decay with index α2,x =1.35 ± 0.02. In the optical and UV light curves, a break at
37 +4.7−4.0 ks is detected among a decay with index α1 = 0.96
± 0.01 and a further steep decay with index α2 = 1.36 +0.01−0.02 .
Assuming the break at 37 +4.7
−4.0 ks as a jet break, we canderive the opening angle of θj ~ 3° and the collimation
corrected energy of Eγ = 1051 erg.
It follows the spectral energy correlations between
the rest-frame peak energy Epeak(= 1028 ± 8 keV) andthe isotropic peak luminosity which are typically seenin the powerful GRBs at higher redshifts of z ~ 1–2 [3].
This suggests that these huge explosions are driven by
a common central engine from the early to the present

036

I Scientific Highlights

universe. Then, a broad-lined Type Ic supernova, SN
2013cq, associated with GRB 130427A was detected [4],which suggests the existence of supernovae associated withthe powerful and high-z GRBs.

Figure 1: Multiwavelength light curves of GRB 130427A [1]. γ-ray
data are from Fermi-LAT. X-ray data are from SwiftXRT and MAXI (Monitor of All-sky X-ray Image).
Optical data are from ground-based facilities, including
the Akeno Observatory (Tokyo Tech Akeno MITSuMETelescope), Okayama Astrophysical Observatory(NAOJ), and Ishigakijima Astronomical Observatory(Mizusawa VLBI Observatory, NAOJ). Radio data arefrom VLA (Karl G. Jansky Very Large Array) [5]. Solidlines represent the light curves predicted by the vanEerten et al. synchrotron model [6].
References[1] Maselli, A., et al.: 2014, Science, 343, 48.
[2] Ackermann, M., et al.: 2014, Science, 343, 42.
[3] Nava, L., et al.: 2012, MNRAS, 421, 1256.
[4] Xu, D., et al.: 2013, ApJ, 776, 98.
[5] Laskar, T., et al.: 2013, ApJ, 776, 119.
[6] van Eerten, H., et al.: 2012, ApJ, 749, 44.