Neil Gehrels

Time-Domain Astronomy with Swift, Fermi and Lobster

The dynamic transient gamma-ray sky is revealing many interesting results, largely due to findings by Fermi and Swift . The list includes new twists on gamma-ray bursts (GRBs), a GeV flare from a symbiotic star, GeV flares from the Crab Nebula, high-energy emission from novae and supernovae, and, within the last year, a new type of object discovered by Swift —a jetted tidal disruption event. In this review we present highlights of these exciting discoveries. A new mission concept called Lobster is also described; it would monitor the X-ray sky at order-of-magnitude higher sensitivity than current missions can.

Suzaku‐WAM, Konus‐Wind, and Swift‐BAT observations of the prompt emission of the highest redshift GRB 050904

We present the results of the highest redshift GRB 050904 from joint spectral analyses among Swift/BAT, Konus‐Wind and Suzaku‐WAM covering a wide energy range of 15–5000 keV. The peak energy was first measured at 338−93+168 keV, corresponding to 2465−678+1225 keV in the source frame. This is one of the highest value that has been ever meaured. The derived spectral and energetic parameters are consisitent with the Amati relation, but not with the Ghirlada relation. This implies that the circumburst density of this burst might be larger than the nominal value, as suggested by other wavelength observations. We also found that the burst could be an outlier in Yonetoku relation.

GRBs in the Era of Rapid Response Telescopes

NASAs Swift and Fermi satellites continue to chase gamma-ray bursts (GRBs) and make ground-breaking discoveries. The resulting science has been greatly enhanced by follow-up studies and coincident event searches from a variety of observatories, including RAPTOR, Watcher, REM, Pi of the Sky, MASTER, iPTF, GROND, GTC, RATIR, DCT, Asiago, Nanshan, Liverpool Robotic Telescope, KAIT, NOT, Gemini, Magellan, Keck, VLT, VLA, ACTA, ALMA, AMI, WSRT, GMRT, CARMA, LOFAR, HAWC, VERITAS, MAGIC, HESS, IceCube, ANTARES, LIGO, HST, Chandra, Spitzer, Fermi, AGILE, INTEGRAL, NuSTAR, IPN, MAXI, CALET, and AstroSAT. These observatories have added to our knowledge of the early-time behavior of GRBs, such as the short-lived reverse-shock which has been seen now in a small handful of the brightest bursts. The emphasis on longer term optical observations, days to weeks after the burst, has increased with the prospects in a few years for multiple active gravitational wave observatories providing good localizations for compact object mergers, and the potential for seeing the isotropic kilonova emission if one of the objects is a neutron star.

Disco very of an extraordinary luminous and soft X-ray transient MAXI J0158744

Mikio Morii1, Hiroshi Tomida2, Masaki Kimura2, Fumitoshi Suwa3, Hitoshi Negoro3, Motoko Serino4, Jamie A. Kennea5, Kim L. Page6, Peter A. Curran7, Frederick M. Walter8, N. Paul. M. Kuin9, Tyler Pritchard5, Satoshi Nakahira2, Kazuo Hiroi10, Ryuichi Usui1, Nobuyuki Kawai1, Julian P. Osborne6, Tatehiro Mihara4, David N. Burrows5, Neil Gehrels11, Mitsuhiro Kohama2, Masaru Matsuoka4, Motoki Nakajima12, Peter W. A. Roming13, Kousuke Sugimori1, Mutsumi Sugizaki4, Yohko Tsuboi14, Hiroshi Tsunemi15, Yoshihiro Ueda10, Shiro Ueno2 and Atsumasa Yoshida16 1Department of Physics, Tokyo Institute of Technology, Ookayama 2-12-1, Meguro-ku, Tokyo 152-8551, Japan. 2ISS Science Project Office, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 2-1-1 Sengen, Tsukuba, Ibaraki 305-8505, Japan. 3Department of Physics, Nihon University, 1-8-14 Surugadai, Chiyoda, Tokyo 101-8308, Japan. 4MAXI team, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. 5Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Laboratory, University Park, Pennsylvania 16802, USA. 6Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK. 7International Centre for Radio Astronomy Research / Curtin University, GPO Box U1987, Perth, WA 6845, Australia. 8Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800, USA. 9Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK. 10Department of Astronomy, Kyoto University, Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan. 11NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA. 12School of Dentistry at Matsudo, Nihon University, 2-870-1 Sakaecho-nishi, Matsudo, Chiba 271-8587, Japan. 13Southwest Research Institute, Space Science and Engineering Division, PO Drawer 28510, San Antonio, Texas 78228-0510, USA. 14Department of Physics, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan. 15Department of Earth and Space Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan. 16Department of Physics and Mathematics, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan.

All-Sky Monitoring of Variable Sources with Fermi GBM

Using the Gamma ray Burst Monitor (GBM) on Fermi, we monitor the transient hard X-ray/soft gamma ray sky. The twelve GBM NaI detectors span 8 keV to 1 MeV, while the two BGO detectors span 150 keV to 40 MeV. We use the Earth occultation technique to monitor a number of sources, including X-ray binaries, AGN, and solar flaring activity. Our monitoring reveals predictable and unpredictable phenomena such as transient outbursts and state changes. With GBM we also track the pulsed flux and spin frequency of accretion powered pulsars using epoch-folding techniques. Searches for quasi-periodic oscillations and X-ray bursts are also possible with GBM all-sky monitoring. Highlights from the Earth Occultation and Pulsar projects will be presented including our recent surprising discovery of variations in the total flux from the Crab. Inclusion of an all-sky monitor is crucial for a successful future X-ray timing mission.

Gamma ray burst optical counterpart search experiment (GROCSE)

GROCSE (Gamma-Ray Optical Counterpart Search Experiments) is a system of automated telescopes that search for simultaneous optical activity associated with gamma ray bursts in response to real-time burst notifications provided by the BATSE/BACODINE network. The first generation system, GROCSE 1, is sensitive down to Mv {approximately} 8.5 and requires an average of 12 seconds to obtain the first images of the gamma ray burst error box defined by the BACODINE trigger. The collaboration is now constructing a second generation system which has a 4 second slewing time and can reach Mv {approximately} 14 with a 5 second exposure. GROCSE 2 consists of 4 cameras on a single mount. Each camera views the night sky through a commercial Canon lens (f/1.8, focal length 200 mm) and utilizes a 2K x 2K Loral CCD. Light weight and low noise custom readout electronics were designed and fabricated for these CCDs. The total field of view of the 4 cameras is 17.6 x 17.6 {degree}. GROCSE II will be operated by the end of 1995. In this paper, the authors present an overview of the GROCSE system and the results of measurements with a GROCSE 2 prototype unit.