93 research outputs found
Interplanetary Network Localization of GRB991208 and the Discovery of its Afterglow
The extremely energetic (~10^-4 erg/cm^2) gamma-ray burst (GRB) of 1999
December 8 was triangulated to a ~14 sq. arcmin. error box ~1.8 d after its
arrival at Earth with the 3rd interplanetary network (IPN), consisting of the
Ulysses, Near Earth Asteroid Rendezvous (NEAR), and WIND spacecraft. Radio
observations with the Very Large Array ~2.7 d after the burst revealed a bright
fading counterpart whose position is consistent with that of an optical
transient source whose redshift is z=0.707. We present the time history, peak
flux, fluence, and refined 1.3 sq. arcmin. error box of this event, and discuss
its energetics. This is the first time that a counterpart has been found for a
GRB localized only by the IPN.Comment: Revised version, accepted for publication in the Astrophysical
Journal Letter
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Detection and characterization of 0.5â8 MeV neutrons near Mercury: Evidence for a solar origin
Data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) Neutron Spectrometer (NS) have been used to identify energetic neutrons (0.5â8âMeV energy) associated with solar events that occurred on 4 June 2011. Multiple lines of evidence, including measurements from the NS and the MESSENGER Gamma-Ray Spectrometer, indicate that the detected neutrons have a solar origin. This evidence includes a lack of time-coincident, energetic (>45âMeV) charged particles that could otherwise create local neutrons from nearby spacecraft material and a lack of proton-induced gamma rays that should be seen if energetic protons were present. NS data cannot rule out the presence of lower-energy ions (<30âMeV) that can produce local neutrons. However, the ion spectral shape required to produce the measured neutron count rate locally is softer than any known ion spectral shape. The neutron energy spectrum shows a relative enhancement in the energy range 0.8â3âMeV compared with cosmic-ray-generated neutrons from the spacecraft or Mercury. The spectral shape of the measured neutron fluence spectrum is consistent with a previously modeled fluence spectrum of neutrons that originate at the Sun and are propagated through the MESSENGER spacecraft to the NS. These measurements provide strong evidence for a solar origin of the detected neutrons and suggest that a large number of low-energy threshold ion evaporation reactions were taking place on the Sun during the neutron event
Multi-Wavelength Studies of the Optically Dark Gamma-Ray Burst 001025A
We identify the fading X-ray afterglow of GRB 001025A from XMM-Newton
observations obtained 1.9-2.3 days, 2 years, and 2.5 years after the burst. The
non-detection of an optical counterpart to an upper limit of R=25.5, 1.20 days
after the burst, makes GRB 001025A a ``dark'' burst. Based on the X-ray
afterglow spectral properties of GRB 001025A, we argue that some bursts appear
optically dark because their afterglow is faint and their cooling frequency is
close to the X-ray band. This interpretation is applicable to several of the
few other dark bursts where the X-ray spectral index has been measured. The
X-ray afterglow flux of GRB 001025A is an order of magnitude lower than for
typical long-duration gamma-ray bursts. The spectrum of the X-ray afterglow can
be fitted with an absorbed synchrotron emission model, an absorbed thermal
plasma model, or a combination thereof. For the latter, an extrapolation to
optical wavelengths can be reconciled with the R-band upper limit on the
afterglow, without invoking any optical circumburst absorption, provided the
cooling frequency is close to the X-ray band. Alternatively, if the X-ray
afterglow is due to synchrotron emission only, seven magnitudes of extinction
in the observed R-band is required to meet the R-band upper limit, making GRB
001025A much more obscured than bursts with detected optical afterglows. Based
on the column density of X-ray absorbing circumburst matter, an SMC gas-to-dust
ratio is insufficient to produce this amount of extinction. The X-ray tail of
the prompt emission enters a steep temporal decay excluding that the tail of
the prompt emission is the onset of the afterglow (abridged).Comment: 32 pages, 8 figures, ApJ in pres
The very red afterglow of GRB 000418 - further evidence for dust extinction in a GRB host galaxy
We report near-infrared and optical follow-up observations of the afterglow
of the Gamma-Ray Burst 000418 starting 2.5 days after the occurrence of the
burst and extending over nearly seven weeks. GRB 000418 represents the second
case for which the afterglow was initially identified by observations in the
near-infrared. During the first 10 days its R-band afterglow was well
characterized by a single power-law decay with a slope of 0.86. However, at
later times the temporal evolution of the afterglow flattens with respect to a
simple power-law decay. Attributing this to an underlying host galaxy we find
its magnitude to be R=23.9 and an intrinsic afterglow decay slope of 1.22. The
afterglow was very red with R-K=4 mag. The observations can be explained by an
adiabatic, spherical fireball solution and a heavy reddening due to dust
extinction in the host galaxy. This supports the picture that (long) bursts are
associated with events in star-forming regions.Comment: Accepted for publication in The Astrophysical Journal. 12 pages;
citations & references updated; minor textual change
The Interplanetary Network Supplement to the BATSE Catalogs of Untriggered Cosmic Gamma Ray Bursts
We present Interplanetary Network (IPN) detection and localization
information for 211 gamma-ray bursts (GRBs) observed as untriggered events by
the Burst and Transient Source Experiment (BATSE), and published in catalogs by
Kommers et al. (2001) and Stern et al. (2001). IPN confirmations have been
obtained by analyzing the data from 11 experiments. For any given burst
observed by BATSE and one other distant spacecraft, arrival time analysis (or
``triangulation'') results in an annulus of possible arrival directions whose
half-width varies between 14 arcseconds and 5.6 degrees, depending on the
intensity, time history, and arrival direction of the burst, as well as the
distance between the spacecraft. This annulus generally intersects the BATSE
error circle, resulting in a reduction of the area of up to a factor of ~650.
When three widely separated spacecraft observed a burst, the result is an error
box whose area is as much as 30000 times smaller than that of the BATSE error
circle.
Because the IPN instruments are considerably less sensitive than BATSE, they
generally did not detect the weakest untriggered bursts, but did detect the
more intense ones which failed to trigger BATSE when the trigger was disabled.
In a few cases, we have been able to identify the probable origin of bursts as
soft gamma repeaters. The vast majority of the IPN-detected events, however,
are GRBs, and the confirmation of them validates many of the procedures
utilized to detect BATSE untriggered bursts.Comment: Minor revisions. Accepted for publication in the Astrophysical
Journal Supplement Series, February 200
Investigation of Primordial Black Hole Bursts using Interplanetary Network Gamma-ray Bursts
The detection of a gamma-ray burst (GRB) in the solar neighborhood would have
very important implications for GRB phenomenology. The leading theories for
cosmological GRBs would not be able to explain such events. The final bursts of
evaporating Primordial Black Holes (PBHs), however, would be a natural
explanation for local GRBs. We present a novel technique that can constrain the
distance to gamma-ray bursts using detections from widely separated,
non-imaging spacecraft. This method can determine the actual distance to the
burst if it is local. We applied this method to constrain distances to a sample
of 36 short duration GRBs detected by the Interplanetary Network (IPN) that
show observational properties that are expected from PBH evaporations. These
bursts have minimum possible distances in the 10^13-10^18 cm (7-10^5 AU) range,
consistent with the expected PBH energetics and with a possible origin in the
solar neighborhood, although none of the bursts can be unambiguously
demonstrated to be local. Assuming these bursts are real PBH events, we
estimate lower limits on the PBH burst evaporation rate in the solar
neighborhood.Comment: Accepted to the Astrophysical Journal (9 Figures, 3 Tables
Solar Influence on Nuclear Decay Rates: Constraints from the MESSENGER Mission
We have analyzed Cs-137 decay data, obtained from a small sample onboard the
MESSENGER spacecraft en route to Mercury, with the aim of setting limits on a
possible correlation between nuclear decay rates and solar activity. Such a
correlation has been suggested recently on the basis of data from Mn-54 decay
during the solar flare of 13 December 2006, and by indications of an annual and
other periodic variations in the decay rates of Si-32, Cl-36, and Ra-226. Data
from five measurements of the Cs-137 count rate over a period of approximately
5.4 years have been fit to a formula which accounts for the usual exponential
decrease in count rate over time, along with the addition of a theoretical
solar contribution varying with MESSENGER-Sun separation. The indication of
solar influence is then characterized by a non-zero value of the calculated
parameter \xi, and we find \xi=(2.8+/-8.1)x10^{-3} for Cs-137. A simulation of
the increased data that can hypothetically be expected following Mercury orbit
insertion on 18 March 2011 suggests that the anticipated improvement in the
determination of \xi could reveal a non-zero value of \xi if present at a level
consistent with other data.Comment: Accepted for publication in Astrophysics and Space Science, 2011. 7
pages, 5 figures. Version 2 has corrected Figure 1, since Fig. 1 did not
appear correctly in Version
Rehabilitation Following Posterior Shoulder Stabilization
Posterior shoulder instability has been noted in recent reports to occur at a higher prevalence than originally believed, with many cases occurring in active populations. In most cases, primary surgical treatment for posterior shoulder instabilityâa posterior labral repairâis indicated for those patients who have failed conservative management and demonstrate persistent functional limitations. In order to optimize surgical success and return to a prior level of function, a comprehensive and focused rehabilitation program is crucial. Currently, there is a limited amount of literature focusing on rehabilitation after surgery for posterior instability. Therefore, the purpose of this clinical commentary is to present a post-surgical rehabilitation program for patients following posterior shoulder labral repair, with recommendations based upon best medical evidence.
# Level of Evidence
Integrating the Fermi Gamma-Ray Burst Monitor into the 3rd Interplanetary Network
We are integrating the Fermi Gamma-Ray Burst Monitor (GBM) into the
Interplanetary Network (IPN) of Gamma-Ray Burst (GRB) detectors. With the GBM,
the IPN will comprise 9 experiments. This will 1) assist the Fermi team in
understanding and reducing their systematic localization uncertainties, 2)
reduce the sizes of the GBM and Large Area Telescope (LAT) error circles by 1
to 4 orders of magnitude, 3) facilitate the identification of GRB sources with
objects found by ground- and space-based observatories at other wavelengths,
from the radio to very high energy gamma-rays, 4) reduce the uncertainties in
associating some LAT detections of high energy photons with GBM bursts, and 5)
facilitate searches for non-electromagnetic GRB counterparts, particularly
neutrinos and gravitational radiation. We present examples and demonstrate the
synergy between Fermi and the IPN. This is a Fermi Cycle 2 Guest Investigator
project.Comment: 5 pages, 11 figures. 2009 Fermi Symposium. eConf Proceedings C09112
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