13 research outputs found
Goddard Robotic Telescope - Optical Follow-up of GRBs and Coordinated Observations of AGNs -
Since it is not possible to predict when a Gamma-Ray Burst (GRB) will occur
or when Active Galactic Nucleus (AGN) flaring activity starts,
follow-up/monitoring ground telescopes must be located as uniformly as possible
all over the world in order to collect data simultaneously with Fermi and Swift
detections. However, there is a distinct gap in follow-up coverage of
telescopes in the eastern U.S. region based on the operations of Swift.
Motivated by this fact, we have constructed a 14" fully automated optical
robotic telescope, Goddard Robotic Telescope (GRT), at the Goddard Geophysical
and Astronomical Observatory. The aims of our robotic telescope are 1) to
follow-up Swift/Fermi GRBs and 2) to perform the coordinated optical
observations of Fermi Large Area Telescope (LAT) AGN. Our telescope system
consists of off-the-shelf hardware. With the focal reducer, we are able to
match the field of view of Swift narrow instruments (20' x 20'). We started
scientific observations in mid-November 2008 and GRT has been fully remotely
operated since August 2009. The 3 sigma upper limit in a 30-second exposure in
the R filter is ~15.4 mag; however, we can reach to ~18 mag in a 600-second
exposures. Due to the weather condition at the telescope site, our observing
efficiency is 30-40% on average.Comment: 14 pages, 14 figures, accepted for publication in ASR special issue
on Neutron Stars and Gamma Ray Burst
Primordial Black Holes: Observational Characteristics of The Final Evaporation
Many early universe theories predict the creation of Primordial Black Holes
(PBHs). PBHs could have masses ranging from the Planck mass to 10^5 solar
masses or higher depending on the size of the universe at formation. A Black
Hole (BH) has a Hawking temperature which is inversely proportional to its
mass. Hence a sufficiently small BH will quasi-thermally radiate particles at
an ever-increasing rate as emission lowers its mass and raises its temperature.
The final moments of this evaporation phase should be explosive and its
description is dependent on the particle physics model. In this work we
investigate the final few seconds of BH evaporation, using the Standard Model
and incorporating the most recent Large Hadron Collider (LHC) results, and
provide a new parameterization for the instantaneous emission spectrum. We
calculate for the first time energy-dependent PBH burst light curves in the
GeV/TeV energy range. Moreover, we explore PBH burst search methods and
potential observational PBH burst signatures. We have found a unique signature
in the PBH burst light curves that may be detectable by GeV/TeV gamma-ray
observatories such as the High Altitude Water Cerenkov (HAWC) observatory. The
implications of beyond the Standard Model theories on the PBH burst
observational characteristics are also discussed, including potential
sensitivity of the instantaneous photon detection rate to a squark threshold in
the 5 -10 TeV range.Comment: Accepted to Astroparticle Physics Journal (71 Pages, 22 Figures
Milagro limits and HAWC sensitivity for the rate-density of evaporating Primordial Black Holes
postprin
On the sensitivity of the HAWC observatory to gamma-ray bursts
We present the sensitivity of HAWC to Gamma Ray Bursts (GRBs). HAWC is a very
high-energy gamma-ray observatory currently under construction in Mexico at an
altitude of 4100 m. It will observe atmospheric air showers via the water
Cherenkov method. HAWC will consist of 300 large water tanks instrumented with
4 photomultipliers each. HAWC has two data acquisition (DAQ) systems. The main
DAQ system reads out coincident signals in the tanks and reconstructs the
direction and energy of individual atmospheric showers. The scaler DAQ counts
the hits in each photomultiplier tube (PMT) in the detector and searches for a
statistical excess over the noise of all PMTs. We show that HAWC has a
realistic opportunity to observe the high-energy power law components of GRBs
that extend at least up to 30 GeV, as it has been observed by Fermi LAT. The
two DAQ systems have an energy threshold that is low enough to observe events
similar to GRB 090510 and GRB 090902b with the characteristics observed by
Fermi LAT. HAWC will provide information about the high-energy spectra of GRBs
which in turn could help to understanding about e-pair attenuation in GRB jets,
extragalactic background light absorption, as well as establishing the highest
energy to which GRBs accelerate particles