The Interplanetary Network K

Gamma-ray Bursts: 15 Years of GRB Afterglows A.J. Castro-Tirado, J. Gorosabel and I.H. Park (eds) EAS Publications Series, 61 (2013) 459–464

THE INTERPLANETARY NETWORK K. Hurley 1,I.G.Mitrofanov2,D.Golovin2,M.L.Litvak2,A.B.Sanin2, W. Boynton 3, C. Fellows 3,K.Harshman3,R.Starr3,S.Golenetskii4, R. Aptekar 4, E. Mazets 4,V.Pal’shin4,D.Frederiks4,D.Svinkin4, D.M. Smith 5,W.Hajdas6,A.vonKienlin7,X.Zhang7,A.Rau7, K. Yamaoka 8, T. Takahashi 8, M. Ohno 9, Y. Hanabata 9,Y.Fukazawa9,M.Tashiro10, Y. Terada 10,T.Murakami11,K.Makishima12,13,T.Cline14,15,S.Barthelmy14, J. Cummings 24,16,N.Gehrels14,H.Krimm25,17,D.Palmer18,J.Goldsten19, E. Del Monte20,M.Feroci20,M.Marisaldi21, V. Connaughton 22,M.S.Briggs22 and C. Meegan23

1 U.C. Berkeley Space Sciences Laboratory, 7 Gauss Way, Berkeley, CA 94720-7450, USA 2 Institute for Space Research, Profsojuznaja 84/32, Moscow 117997, Russian Federation 3 University of Arizona, Lunar and Planetary Laboratory, Tucson, AZ 85721, USA 4 Ioﬀe Physico-Technical Institute of the Russian Academy of Sciences, St. Petersburg 194021, Russian Federation 5 Department of Physics and Santa Cruz Institute for Particle Physics, U.C. Santa Cruz, CA 95064, USA 6 Paul Scherrer Institute, 5232 Villigen PSI, Switzerland 7 Max-Planck-Institut f¨ur extraterrestrische Physik, Giessenbachstrasse, Garching, 85748 Germany 8 Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan 9 Department of Physics, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan 10 Department of Physics, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama-shi, Saitama 338-8570, Japan 11 Department of Physics, Kanazawa University, Kadoma-cho, Kanazawa, Ishikawa 920-1192, Japan 12 Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan 13 Makishima Cosmic Radiation Laboratory, The Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan 14 NASA Goddard Space Flight Center, Code 661, Greenbelt, MD 20771, USA 15 Emeritus 16 Joint Center for Astrophysics, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA 17 Universities Space Research Association, 10211 Wincopin Circle, Suite 500, Columbia, MD 21044, USA 18 Los Alamos National Laboratory, PO Box 1663, Los Alamos, NM 87545, USA 19 Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723, USA 20 INAF/IASF-Roma, via Fosso del Cavaliere 100, 00133 Roma, Italy 21 INAF/IASF-Bologna, via Gobetti 101, 40129 Bologna, Italy 22 University of Alabama in Huntsville, NSSTC, 320 Sparkman Drive, Huntsville, AL 35805, USA 23 Universities Space Research Association, NSSTC, 320 Sparkman Drive, Huntsville, AL 35805, USA 24 UMBC/CRESST/NASA Goddard Space Flight Center, Code 661, Greenbelt, MD 20771, USA 25 CRESST/NASA Goddard Space Flight Center, Code 661, Greenbelt, MD 20771, USA

c EAS, EDP Sciences 2013 DOI: 10.1051/eas/1361074 460 Gamma-ray Bursts: 15 Years of GRB Afterglows

Abstract. We describe the current, 9-spacecraft Interplanetary Net- work (IPN). The IPN detects about 325 gamma-ray bursts per year, of which about 100 are not localized by any other missions. We give some examples of how the data, which are public, can be utilized.

1 Introduction

The current IPN consists of one or more experiments on nine missions: AGILE, Fermi, RHESSI, Suzaku,andSwift, in low-Earth orbit; INTEGRAL, in a high apogee Earth orbit; Konus-Wind,atL1, ∼5.5 light-seconds from Earth; and MESSENGER and Odyssey, in orbit around Mercury and Mars, respectively. This conﬁguration is an ideal one in many respects. The 5 low-Earth orbit missions assure that virtually every burst is detected by at least one Earth-orbiting mission, providing an important vertex for triangulation. The two planetary missions give long baselines which make precise localizations possible. And INTEGRAL and Konus assure redundancy and overdetermination of the localizations in many cases. Indeed, even without the planetary missions, the mini-network of 5 low- Earth orbiters, plus INTEGRAL and Konus, often make it possible to obtain relatively small error boxes for many bursts. Figure 1 shows the conﬁguration of the IPN, which is an all-sky, full-time monitor not only of GRBs, but also of magnetar bursts, and other high-energy phenomena.

Fig. 1. The 9-spacecraft IPN. The near-Earth mini-network often produces small error boxes in the absence of detections by distant spacecraft. K. Hurley et al.: The Interplanetary Network 461

Fig. 2. A Venn diagram showing the relation between the number of bursts per year detected by the IPN, Swift,andFermi. Swift observes an average of 162 bursts per year, counting those both inside (∼100) and outside (∼62) the coded ﬁeld of view. Fermi observes a total of 245, and the IPN observes a total of 325. Of the 325 IPN bursts, 190 are also detected by Fermi, and 125 are also detected by Swift (of which ∼77 are inside the coded ﬁeld of view). 73 bursts per year are detected by the IPN, Swift, and Fermi. 100 IPN bursts per year are not detected by either Swift or Fermi.

Figure 2 shows the relation between bursts detected by the IPN and bursts detected by Swift and Fermi. Roughly 100 IPN GRBs/year are not detected by those missions. Moreover, about 70 of the 190 GRBs/year which are detected by the IPN and Fermi can be localized by the IPN to error box areas which are several orders of magnitude smaller than those of Fermi alone. Finally, Figure 3 shows the sensitivity of the IPN as a function of GRB peak ﬂux. Another measure of sensitivity is to consider the redshifts of IPN bursts, which range from 0.7 to 4.5.

2SomeusesofIPNdata

2.1 Reﬁning Fermi GBM and LAT localizations

IPN error boxes are typically orders of magnitude smaller than Fermi GBM error circles. Indeed, they are comparable in size to, or often smaller than, LAT error circles. Figure 4 shows one example. Reﬁning these error circles helps the GBM team understand their systematic uncertainties, and aids the LAT team in identifying bursts with high-energy emission.

2.2 GRBs from optically detected energetic supernovae

The optical signatures of energetic Type Ib/c supernovae are frequently found in GRB afterglow lightcurves. But can GRBs be identiﬁed by searching at the times and positions of optically-discovered energetic supernovae? IPN searches have now been conducted for 23 supernovae, from SN1997dq to SN2012ap (Hurley & Pian 2008; Sanders et al. 2012; Corsi et al. 2011; Soderberg et al. 2012; Margutti et al. 2012; Walker et al. 2013). The advantage of the IPN in these searches is its all-sky, full-time coverage. The negative results to date constrain the beaming and energetics of these SNe; the search is continuing. 462 Gamma-ray Bursts: 15 Years of GRB Afterglows

Fig. 3. The IPN sensitivity to GRBs as a function of their peak ﬂux. The peak ﬂux is measured by the Swift BAT in the 15 − 150 keV energy range over 1 second. The dashed line shows the probability that any two or more IPN spacecraft will detect the burst. The solid line shows the probability that any two or more widely separated IPN spacecraft will detect it; the latter bursts can be localized to some extent.

Fig. 4. Fermi GBM, LAT, and IPN localizations of GRB 090323. The two IPN annuli intersect to form the error box shaded in green. A zoom of this region shows the LAT error circle and the location of the optical afterglow (asterisk) in more detail (Hurley et al. 2009; Ohno et al. 2009; Updike et al. 2009). K. Hurley et al.: The Interplanetary Network 463

2.3 Non-electromagnetic emission from GRBs The IPN provided a large number of GRBs to the AMANDA project for searches for neutrino emission (Achterberg et al. 2008), and continues to collaborate with the IceCube project, where a search involving over 100 bursts is in progress. The LIGO and Virgo collaborations are looking at ∼380 IPN bursts which occurred during Science Run 5 (2005–2007), and ∼525 IPN bursts which occurred during Science Run 6 (2009–2010, preliminary results in Abadie et al. 2012). These are the most extensive searches for GRB-related gravitational radiation to date. The unique aspect of the IPN data is that there are ∼100 events/year that are not observed by Swift or Fermi, and, in addition, that the bursts tend to be the more nearby and/or energetic ones.

2.4 Some other projects IPN localizations are being used to search for polarization using the GAP po- larimeter on the Japanese IKAROS mission, and to derive the energy spectra of bursts observed by the Suzaku HXD WAM. By reﬁning Fermi GBM localizations, the IPN is useful to the MAGIC and HAWC projects, which are searching for very high energy gamma-ray emission from bursts. IPN observations are also useful for determining the nature of candidate orphan afterglows.

3 Short bursts

Since its inception, the IPN has had a high detection rate of short-duration GRBs. The ﬁrst precise localization (∼800 sq. arcsec.) of a short GRB was published in Laros et al. (1981), and deep searches (magnitude 23.5) by Chevalier et al. (1981) revealed objects that were “probably distant galaxies unrelated to the burst source”. Today, the detection rate is about 20/year (Pal’shin et al. 2013). Although it is not possible to localize these bursts with the speed that Swift achieves, they nevertheless play an important role in many projects, particularly the LIGO/Virgo searches.

4 The IPN database

IPN data are public. The IPN database (www.ssl.berkeley.edu/ipn3/index. html) contains, among other things:

1. An 11,000 publication GRB bibliography (1972–2012),

2. A list of 25,000 events (mainly cosmic, SGR, and solar), giving the dates and times of bursts, and a list of which spacecraft detected them (1990–2012), and

3. 7000 GRB localizations (1990–2012). 464 Gamma-ray Bursts: 15 Years of GRB Afterglows

These lists are growing constantly. Some parts of the database are updated on a roughly daily basis, while others are updated less frequently. Work is underway to provide a user interface to search the localizations, which consist of annuli, more eﬃciently. Potential users are urged to contact [email protected] to make sure that the database is fully populated for their projects. This applies particularly to the localizations, where the database is incomplete simply due to a lack of manpower.

5Thefuture

The missions which are currently part of the IPN are expected to continue op- erating at least through 2013, and many of them will probably operate for much longer, with lifetimes limited mainly by funding. New missions which can be in- corporated into the network include, but are not limited to, the Japanese Astro-H (2013 launch) and ESA’s Bepi-Colombo (2015).

Support for the IPN has been provided in the US by NASA grants NNX09AU03G (Fermi ), NNX08AX95G (INTEGRAL), NNX09AO97G (Swift), NNX09AV61G (Suzaku), NNX07AR71G (MESSENGER), and by JPL Contract Y503559 (Odyssey). The Konus-Wind experiment is supported by a Russian Space Agency Contract and by RFBR grant 11-02-12082-oﬁ-m.

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