The Interplanetary Network Supplement to the BeppoSAX Gamma-ray Burst Catalogs

Abstract

Between 1996 July and 2002 April, one or more spacecraft of the interplanetary network detected 786 cosmic gamma-ray bursts that were also detected by the Gamma-Ray Burst Monitor and/or Wide-Field X-Ray Camera experiments aboard the BeppoSAX spacecraft. During this period, the network consisted of up to six spacecraft, and using triangulation, the localizations of 475 bursts were obtained. We present the localization data for these events.

Full text

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arXiv:1004.1650v1 [astro-ph.HE] 9 Apr 2010
The Interplanetary Network Supplement to the BeppoSAX
Gamma-Ray Burst Catalogs
K. Hurley
Space Sciences Laboratory, University of California, 7 Gauss Way, Berkeley,
CA 94720-7450, U.S.A.
khurley@ssl.berkeley.edu
C. Guidorzi, F. Frontera1, E. Montanari2, F. Rossi
University of Ferrara, Physics Department, Via Saragat, 1, 44100 Ferrara, Italy
M. Feroci
INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica, via Fosso del
Cavaliere, Rome, I-00133, Italy
E. Mazets, S. Golenetskii, D. D. Frederiks, V. D. Pal’shin, R. L. Aptekar
Ioffe Physico-Technical Institute of the Russian Academy of Sciences, St.
Petersburg, 194021, Russian Federation
T. Cline3, J. Trombka, T. McClanahan, R. Starr
NASA Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A.
J.-L. Atteia, C. Barraud, A. P´ elangeon
Laboratoire d’Astrophysique, Observatoire Midi-Pyr´ er´ ees, 14 avenue E. Belin,
31400 Toulouse, France
1INAF/Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101,
I-40129 Bologna, Italy
2Istituto IS Calvi, Finale Emilia (MO), Italy
3Emeritus

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M. Bo¨ er
Observatoire de Haute-Provence, 04870 Saint Michel l’Observatoire, France
R. Vanderspek, G. Ricker
Kavli Institute for Astrophysics and Space Research, Massachusetts Institute
of Technology, 70 Vassar Street, Cambridge, MA 02139, U.S.A.
I. G. Mitrofanov, D. V. Golovin, A. S. Kozyrev, M. L. Litvak, A. B. Sanin
Space Research Institute, 84/32, Profsoyuznaya, Moscow 117997, Russian
Federation
W. Boynton, C. Fellows, K. Harshman
University of Arizona, Department of Planetary Sciences, Tucson, Arizona
85721, U.S.A.
J. Goldsten, R. Gold
Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723,
U.S.A.
D.M. Smith
Physics Department and Santa Cruz Institute for Particle Physics, University
of California, Santa Cruz, Santa Cruz, CA 95064, U.S.A.
C. Wigger, W. Hajdas
Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
Received
;accepted

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Date: 8 April 2010
1.Introduction
Between 1996 July and 2002 April, the Wide Field X-Ray Camera (WFC) and
Gamma-Ray Burst Monitor (GRBM) aboard the BeppoSAX mission detected 62 and
1092 cosmic gamma-ray bursts, respectively, and localized many of them to accuracies
which ranged from arcminutes to tens of degrees (Vetere et al. 2007; Frontera et al. 2009);
instrument descriptions may be found in Feroci et al. (1997), Frontera et al. (1997), and
Jager et al. (1997). These detections were used to initiate searches through the data of the
spacecraft comprising the interplanetary network (IPN). In 475 cases localizations could
be obtained by triangulation, and successful multiwavelength counterpart searches were
initiated for some of them. The IPN contained between 4 and 6 spacecraft during this
period. They were, in addition to BeppoSAX : Ulysses, in heliocentric orbit at distances
between 670 and 3180 light-seconds from Earth (Hurley et al. 1992); Konus-Wind , in
various orbits up to around 4 light-seconds from Earth (Aptekar et al. 1995); HETE-II -
FREGATE , in low Earth orbit (Ricker et al. 2003; Atteia et al. 2003); the Near-Earth
Asteroid Rendezvous mission (NEAR), at distances up to 1300 light-seconds from Earth
(Trombka et al. 1999); Mars Odyssey, launched in 2001 April and in orbit around Mars
starting in 2001 October, up to 1250 light-seconds from Earth (Hurley et al. 2006a); the
Compton Gamma-Ray Observatory (the Burst and Transient Source Experiment, BATSE -
Fishman et al. (1992); and the Ramaty High Energy Solar Spectroscopic Imager (RHESSI)
both in low Earth orbit (Smith et al. 2002). Their timelines are presented in figure 1. In
this paper, we present the localization data obtained by the IPN for these bursts.
At least three other spacecraft recorded GRB detections during this period, although
they were not used for triangulation and therefore were not, strictly speaking, part of the

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IPN. The Rossi X-Ray Timing Explorer (RXTE) All Sky Monitor detected and localized
some BeppoSAX bursts (Smith et al. 1999). It operated in the low energy X-ray range,
where the light curves of gamma-ray bursts differ significantly from the high energy range
where the other IPN instruments operate. The Defense Meteorological Satellite Program
(DMSP) (Terrell et al. 1996, 1998, 2004) and the Stretched Rohini Satellite Series (SROSS)
(Marar et al. 1994) spacecraft detected, but did not localize bursts.
2.Observations
For each gamma-ray burst detected by BeppoSAX , a search was initiated in the data
of the IPN spacecraft. For the spacecraft within a few light-seconds of Earth, the search
window was centered on the BeppoSAX trigger time, and its duration was somewhat greater
than the event duration. For the spacecraft at interplanetary distances, the search window
was twice the light-travel time to the spacecraft if the event arrival direction was unknown,
which was the case for most events. If the arrival direction was known, even coarsely, the
search window was defined by calculating the expected arrival time at the spacecraft, and
searching in a window around it. Of the approximately 3300 events detected by one or more
IPN spacecraft while BeppoSAX was operational, 787 were also detected by BeppoSAX ;
these are listed in table 1, with the following abbreviations: DMS: Defense Meteorological
Satellite Program, HET: HETE-II, Kon: Konus-Wind, MO: Mars Odyssey, NEA: Near
Earth Asteroid Rendezvous mission, RHE: Ramaty High Energy Solar Spectroscopic Imager,
SRS: Stretched Rohini Satellite Series, Uly: Ulysses, XTE: Rossi X-Ray Timing Explorer.
Table 2 shows the number of events observed by each spacecraft in the IPN, and table
3 gives the number of bursts that were detected by a total of N spacecraft, where N is
between 2 and 6 (detections by RXTE, DMSP, and SROSS have been counted).

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3.Localizations
When a GRB arrives at two spacecraft with a delay δT, it may be localized to an
annulus whose half-angle θ with respect to the vector joining the two spacecraft is given by
cosθ =cδT
D
(1)
where c is the speed of light and D is the distance between the two spacecraft. (This
assumes that the burst is a plane wave, i.e. that its distance is much greater than D.) The
annulus width dθ, is
dθ = cσ(δT)/Dsinθ (2)
where σ(δT) is the uncertainty in the time delay. σ(δT) is generally of the order of 100 ms or
more, when both statistical and systematic uncertainties are considered; thus triangulation
between two near-Earth spacecraft, for which D/c is at most ∼40 ms, does not constrain
the burst arrival direction significantly. When D/c is of the order of several light-seconds
(e.g., the distance between Konus-Wind and a near-Earth spacecraft), annuli with widths
of several degrees or less can be obtained; when D/c is several hundred light-seconds or
more (i.e. an interplanetary spacecraft and a near-Earth spacecraft), annulus widths of
the order of arcminutes or less are possible. When two interplanetary spacecraft and a
near-Earth spacecraft observe a GRB, a small error box can be obtained. Table 4 gives the
number of events observed by 0, 1, and 2 interplanetary spacecraft.
475 bursts could be localized by the method above; table 5 gives the localization
information for them. Triangulation annuli are given in the 4 IPN columns: these are the
right ascension and declination of the annulus center α,δ, the annulus radius R, and the
uncertainty in the radius δR. One or two annuli are specified. In addition to triangulation
annuli, several other types of localization information are included in this catalog. The
3 BATSE columns give the right ascension, declination, and 1 σ (statistical only) error
radius of the BATSE localizations. These are taken from the current catalog on the BATSE

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website (http://www.batse.msfc.nasa.gov/batse/grb/catalog/current/), as well as from
the BATSE untriggered burst catalogs (Stern et al. 2001; Kommers et al. 2000). 3 SAX
columns give the right ascension, declination, and 90 % confidence radius of the BeppoSAX
localization, either from the GRBM (Frontera et al. 2009) or the WFC (Vetere et al. 2007),
or from the IAU and GCN Circulars. The 3 HETE columns give the right ascension,
declination, and radius of the Wide Field X-Ray Monitor error circle (Vanderspek et al.
2010). Combining these error circles with the IPN annuli often results in smaller error
regions. IPN localizations for almost all bursts with a BATSE or HETE error circle have
appeared in a previous catalog and are repeated here only for completeness.
The two Ecliptic columns give the ecliptic latitudes of the bursts, measured northward
(positive) from the ecliptic plane towards the north ecliptic pole. These are derived
by comparing the count rates of the two Konus-Wind detectors (Aptekar et al. 1995).
Planet-blocking is specified by the right ascension and declination of the planet’s center
and its radius, in the 3 Planet columns. When a spacecraft in low Earth or Mars orbit
observes a burst, the planet blocks up to ≈ 3.7 sr of the sky. This is often useful for
deciding which of two annulus intersections is the correct one, or for eliminating portions
of a single annulus. Finally, the Other column gives the right ascension, declination, and
radius of any other localization region, which may be obtained in one of several ways. In
some cases, the burst was observed by four spacecraft which were separated by large enough
distances to give 3 triangulation annuli, whose intersections are consistent with a single
error box. In other cases, the anisotropic response of one of the IPN experiments allows the
ambiguity to be resolved. In still other cases, a region may be derived from planet-blocking
by a second spacecraft in addition to the data in the Planet column. In this case the error
circle given is the complement of the planet-blocking circle, that is, a circle whose RA is
the RA of the planet plus 180 degrees, whose declination is the negative of the planet’s
declination, and whose radius is 180 degrees minus the planet’s angular radius. The units

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of all entries in table 5 are degrees, and all coordinates are J2000. For some events, no
triangulation was possible, but coarse constraints on the burst arrival direction can be
derived from planet-blocking, ecliptic latitudes, or both. This information is not given here,
but information on these events, as well as the ones in this catalog, may be found at the
IPN website: ssl.berkeley.edu/ipn3/index.html. Figures 2 and 3 show examples of
coarse and fine IPN localizations.
As for BATSE, the BeppoSAX GRBM localizations are derived by comparing the count
rates of various detectors aboard these spacecraft. These localizations are affected by Earth
albedo and absorption by spacecraft materials, among other things, and their shapes are in
general complex. The error circles are approximations to these shapes. They are centered at
the point which is the most likely arrival direction for the burst, and their radii are defined
so that their areas are equal to the 1 σ (BATSE) or 90 % confidence (BeppoSAX GRBM)
statistical-only true error regions. Therefore in some cases, indicated by a footnote, the
IPN annuli do not cross the error circles. This occurs for 25 of the 133 BeppoSAX GRBM
localizations in this catalog. We have examined the true BeppoSAX error regions in all of
these cases and have verified that they are indeed consistent with the IPN annuli. In some
of these cases, an error circle has been defined in the “Other” column which limits the IPN
annulus or annuli to a region which, from a consideration of all the available data, is known
to define the arrival direction. Thus for those bursts where the GRBM error circle does not
intersect the IPN annulus, the “Other” circle should be used in place of the GRBM circle.
Table 6 gives the approximate localization area in square degrees for each of the bursts
in table 5. This is the area of the region which is common to all the localizations given in
table 5. For bursts where the BeppoSAX or BATSE error circle does not intersect the IPN
annulus, the area given is that of the annulus alone.

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4. Comments on specific events
GRB960916 at 03:56:20 is GRB960916B in the BeppoSAX catalog (Frontera et al.
2009). GRB960916A occurred 312 s earlier, at 03:51:08, and it was detected by Konus-Wind
, but not by Ulysses . This non-detection is consistent with the fact that the earlier event
was weaker. The Konus ecliptic latitudes for these two events are consistent with a single
origin, i.e. a very long burst.
GRB970315 at 22:09:19 (GRB970315B in Frontera et al. (2009) may be from the same
source as BATSE 6125 at 22:13:42 (http://www.batse.msfc.nasa.gov/batse/grb/catalog/current/).
The IPN annulus passes through the BATSE error circle, and the duration of the BATSE
event is given as 1307 s. BeppoSAX entered the SAA at 22:10:09, so it could not observe
the BATSE event, and the BATSE position of the event was Earth-occulted to BATSE
at the time of the BeppoSAX event. If these are indeed from a single source, the total
duration would have been around 1570 s. Ulysses did not observe any emission which would
be consistent with the BATSE burst, but this is consistent with its lower intensity.
GRB970415 was observed as a very weak event by Ulysses , and reliable triangulation
of it is not possible.
GRB970518 has a duration of approximately 370 s. The GRBM observed only the
later part of the event, at 07:12:12. However, the burst started at 07:06:23, and this is the
time given in tables 1, 5, and 6.
GRB971228B at 14:53:52 was observed as a very weak event by Ulysses , and reliable
triangulation of it is not possible.
GRB990516A at 20:55:15 was observed as a very weak event by Ulysses , and reliable
triangulation of it is not possible.
GRB990905 at 22:38:55 was observed as a very weak event by Ulysses , and reliable

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triangulation of it is not possible.
GRB991026 has an IPN localization which is inconsistent with the final BeppoSAX
WFC localization in Vetere et al. (2007). The minimum distance between the IPN
annulus and the WFC position is about 4.8 degrees (no uncertainty is given for the WFC
localization). The WFC position given is from in’t Zand (private communication, 2004).
GRB991030 has an IPN localization which is inconsistent with the BeppoSAX WFC
localization in Vetere et al. (2007). The minimum distance between the IPN annulus and
the WFC position is about 5.9 degrees (no uncertainty is given for WFC localization). The
WFC position given is from in’t Zand (private communication, 2004).
GRB000629 does not appear in the BeppoSAX catalog, because it was initially thought
to be solar. Analysis of the Konus-Wind data, however, points to a likely cosmic origin.
GRB011221 triggered the GRBM just prior to entry into the South Atlantic Anomaly.
All GRBM data were lost, and this burst does not appear in the BeppoSAX catalog.
5.Conclusions
This is the eleventh in a continuing series of IPN catalogs (Hurley et al. 1999a,b,
2000a,b,c, 2005, 2006b; Laros et al. 1997, 1998; Hurley et al. 2009); the localization data
for all of them can be found in electronic form at the IPN website. The IPN is, in
effect, a full-time, all-sky monitor, when the duty cycles and viewing constraints of all its
instruments are considered. Its fluence and flux thresholds for 50% detection efficiency are
about 6 × 10−7ergcm−2and1photoncm−2s−1, respectively. Over the BeppoSAX mission,
787 bursts were detected by the GRBM and/or the WFC and at least one other IPN
instrument and 475 of them could be localized to some extent by triangulation. The more
precise and/or rapid localizations were announced in over 50 IAU and GCN Circulars

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(in 1997, and in 1998 – 2002, respectively), resulting in multiwavelength counterpart
searches. Regardless of precision and speed of the localizations, however, burst data such
as this are useful for numerous studies, such as searching for indications of activity from
previously unknown soft gamma repeaters, associating supernovae with bursts, or searching
for neutrino and gravitational radiation associated with bursts.
6. Acknowledgments
Support for the interplanetary network came from the following sources: JPL Contracts
958056 and 1268385 (Ulysses); MIT Contract SC-R-293291 and NASA NAG5-11451
(HETE); NASA NNX07AH52G (Konus); NASA NAG5-13080 (RHESSI); NASA NAG5-
11451 and JPL Contract 1282043 (Odyssey); NASA NAG5-7766, NAG5-9126, NAG5-10710,
and the U.S. SAX Guest Investigator program (BeppoSAX ); and NASA NAG5-9503
(NEAR). C.G., F.F., and E.M. acknowledge financial support from the ASI-INAF contract
I/088/06/0. In Russia, this work was supported by the Federal Space Agency of Russia and
RFBR grant 09-02-00166a.

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Fig. 1.— The timelines of the missions comprising the interplanetary network between 1996
and 2002. During the period when BeppoSAX was operational, there were a minimum of 3
and a maximum of 5 other missions in the network. There were two interplanetary spacecraft
in operation for most of the BeppoSAX mission, Ulysses and either NEAR or Odyssey .

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15:00
16:00
17:00
18:00
10°
20°
30°
40°
50°
Ecliptic latitude 1
Ecliptic latitude 2
GRBM
Ulysses-Konus annulus
Right Ascension
Declination
0°
Fig. 2.— Localizations of GRB970203. The arrival direction is defined by the intersection
of the 33 degree radius GRBM error circle, the 0.16 degree wide IPN annulus, and the 20
degree wide Konus ecliptic latitude band.

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BATSE-Ulysses annulus
WFC
Right Ascension
08:35:40 08:36:0008:36:20
08:36:40
08:37:00
-19° 00´
-19° 05´
-18° 55´
-18° 50´
-18° 45´
Declination
Fig. 3.— Localizations of GRB980326. The arrival direction is defined by the intersection of
the 0.133 degree radius WFC error circle and the .092 degree wide BATSE-Ulysses annulus.
The initial WFC and IPN localizations were announced in Celidonio et al. (1998) and Hurley
et al. (1998). The optical counterpart, indicated by an asterisk, was found by Groot et al.
(1998).

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