18 research outputs found
Closure relations during the plateau emission of Swift GRBs and the fundamental plane
The Neil Gehrels Swift observatory observe Gamma-Ray bursts (GRBs) plateaus
in X-rays. We test the reliability of the closure relations through the
fireball model when dealing with the GRB plateau emission. We analyze 455 X-ray
lightcurves (LCs) collected by \emph{Swift} from 2005 (January) until 2019
(August) for which the redshift is both known and unknown using the
phenomenological Willingale 2007 model. Using these fits, we analyze the
emission mechanisms and astrophysical environments of these GRBs through the
closure relations within the time interval of the plateau emission. Finally, we
test the 3D fundamental plane relation (Dainotti relation) which connects the
prompt peak luminosity, the time at the end of the plateau (rest-frame), and
the luminosity at that time, on the GRBs with redshift, concerning groups
determined by the closure relations. This allows us to check if the intrinsic
scatter \sigma_{int} of any of these groups is reduced compared to previous
literature. The most fulfilled environments for the electron spectral
distribution, p>2, are Wind Slow Cooling (SC) and ISM Slow Cooling for cases in
which the parameter q, which indicates the flatness of the plateau emission and
accounts for the energy injection, is =0 and =0.5, respectively, both in the
cases with known and unknown redshifts.
We also find that for the sGRBs All ISM Environments with have the
smallest \sigma_{int}=0.04 \pm 0.15 in terms of the fundamental plane relation
holding a probability of occurring by chance of p=0.005. We have shown that the
majority of GRBs presenting the plateau emission fulfil the closure relations,
including the energy injection, with a particular preference for the Wind SC
environment. The subsample of GRBs that fulfil given relations can be used as
possible standard candles and can suggest a way to reduce the intrinsic scatter
of these studied relationships.Comment: 44 pages, 23 figures; Accepted to the PASJ to be published soo
A structured jet explains the extreme GRB 221009A
Long duration gamma-ray bursts (GRBs) are powerful cosmic explosions,
signaling the death of massive stars. Among them, GRB 221009A is by far the
brightest burst ever observed. Due to its enormous energy
(10 erg) and proximity (0.15), GRB
221009A is an exceptionally rare event that pushes the limits of our theories.
We present multi-wavelength observations covering the first three months of its
afterglow evolution. The X-ray brightness decays as a power-law with slope
, which is not consistent with standard predictions for
jetted emission. We attribute this behavior to a shallow energy profile of the
relativistic jet. A similar trend is observed in other energetic GRBs,
suggesting that the most extreme explosions may be powered by structured jets
launched by a common central engine.Comment: Submitted version. 53 pages, 9 figures, 6 table
A Sensitive Search for Supernova Emission Associated with the Extremely Energetic and Nearby GRB 221009A
We report observations of the optical counterpart of the long gamma-ray burst
(LGRB) GRB 221009A. Due to the extreme rarity of being both nearby () and highly energetic ( erg), GRB
221009A offers a unique opportunity to probe the connection between massive
star core collapse and relativistic jet formation across a very broad range of
-ray properties. Adopting a phenomenological power-law model for the
afterglow and host galaxy estimates from high-resolution Hubble Space Telescope
imaging, we use Bayesian model comparison techniques to determine the
likelihood of an associated SN contributing excess flux to the optical light
curve. Though not conclusive, we find moderate evidence
() for the presence of an additional component arising
from an associated supernova, SN 2022xiw, and find that it must be
substantially fainter ( 67% as bright at the 99% confidence interval) than
SN 1998bw. Given the large and uncertain line-of-sight extinction, we attempt
to constrain the supernova parameters (, ,
and ) under several different assumptions with respect to the
host galaxy's extinction. We find properties that are broadly consistent with
previous GRB-associated SNe: - ,
- , and - . We note that these properties are weakly
constrained due to the faintness of the supernova with respect to the afterglow
and host emission, but we do find a robust upper limit on the of
. Given the tremendous range in isotropic
gamma-ray energy release exhibited by GRBs (7 orders of magnitude), the SN
emission appears to be decoupled from the central engine in these systems.Comment: 18 pages, accepted to ApJL, 4 tables, 5 figures. Updated abstract in
Previe
Probing pre-supernova mass loss in double-peaked Type Ibc supernovae from the Zwicky Transient Facility
Eruptive mass loss of massive stars prior to supernova (SN) explosion is key
to understanding their evolution and end fate. An observational signature of
pre-SN mass loss is the detection of an early, short-lived peak prior to the
radioactive-powered peak in the lightcurve of the SN. This is usually
attributed to the SN shock passing through an extended envelope or
circumstellar medium (CSM). Such an early peak is common for double-peaked Type
IIb SNe with an extended Hydrogen envelope but is uncommon for normal Type Ibc
SNe with very compact progenitors. In this paper, we systematically study a
sample of 14 double-peaked Type Ibc SNe out of 475 Type Ibc SNe detected by the
Zwicky Transient Facility. The rate of these events is ~ 3-9 % of Type Ibc SNe.
A strong correlation is seen between the peak brightness of the first and the
second peak. We perform a holistic analysis of this sample's photometric and
spectroscopic properties. We find that six SNe have ejecta mass less than 1.5
Msun. Based on the nebular spectra and lightcurve properties, we estimate that
the progenitor masses for these are less than ~ 12 Msun. The rest have an
ejecta mass > 2.4 Msun and a higher progenitor mass. This sample suggests that
the SNe with low progenitor masses undergo late-time binary mass transfer.
Meanwhile, the SNe with higher progenitor masses are consistent with
wave-driven mass loss or pulsation-pair instability-driven mass loss
simulations.Comment: Submitted to ApJ. Comments are welcome. arXiv admin note: text
overlap with arXiv:2210.0572
Multi-band analyses of the bright GRB~230812B and the associated SN2023pel
GRB~230812B is a bright and relatively nearby () long gamma-ray
burst that has generated significant interest in the community and therefore
has been subsequently observed over the entire electromagnetic spectrum. We
report over 80 observations in X-ray, ultraviolet, optical, infrared, and
sub-millimeter bands from the GRANDMA (Global Rapid Advanced Network for
Multi-messenger Addicts) network of observatories and from observational
partners. Adding complementary data from the literature, we then derive
essential physical parameters associated with the ejecta and external
properties (i.e. the geometry and environment) and compare with other analyses
of this event (e.g. Srinivasaragavan et al. 2023). We spectroscopically confirm
the presence of an associated supernova, SN2023pel, and we derive a
photospheric expansion velocity of v 17 km . We
analyze the photometric data first using empirical fits of the flux and then
with full Bayesian Inference. We again strongly establish the presence of a
supernova in the data, with an absolute peak r-band magnitude . We find a flux-stretching factor or relative brightness and a time-stretching factor ,
both compared to SN1998bw. Therefore, GRB 230812B appears to have a clear long
GRB-supernova association, as expected in the standard collapsar model.
However, as sometimes found in the afterglow modelling of such long GRBs, our
best fit model favours a very low density environment (). We also find small values for
the jet's core angle and
viewing angle. GRB 230812B/SN2023pel is one of the best characterized
afterglows with a distinctive supernova bump
Multiband analyses of the bright GRB 230812B and the associated SN2023pel
GRB 230812B is a bright and relatively nearby (z = 0.36) long gamma-ray burst (GRB) that has generated significant interest in the community and has thus been observed over the entire electromagnetic spectrum. We report over 80 observations in X-ray, ultraviolet, optical, infrared, and submillimetre bands from the GRANDMA (Global Rapid Advanced Network for Multimessenger Addicts) network of observatories and from observational partners. Adding complementary data from the literature, we then derive essential physical parameters associated with the ejecta and external properties (i.e. the geometry and environment) of the GRB and compare with other analyses of this event. We spectroscopically confirm the presence of an associated supernova, SN2023pel, and we derive a photospheric expansion velocity of v ∼ 17 × 103 km s-1. We analyse the photometric data first using empirical fits of the flux and then with full Bayesian inference. We again strongly establish the presence of a supernova in the data, with a maximum (pseudo-)bolometric luminosity of 5.75 × 1042 erg s-1, at 15.76+-10.2181 d (in the observer frame) after the trigger, with a half-max time width of 22.0 d. We compare these values with those of SN1998bw, SN2006aj, and SN2013dx. Our best-fitting model favours a very low density environment (log10(nISM/cm-3) = -2.38+-11.6045) and small values for the jet's core angle θcore = 1.54+-01.8102 deg and viewing angle θobs = 0.76+-01.7629 deg. GRB 230812B is thus one of the best observed afterglows with a distinctive supernova bump
Finding scores in tournaments
A tournament T<SUB>n</SUB> is an orientation of the complete graph on nvertices. We continue the algorithmic study initiated by 10 of recognizing various directed trees in tournaments. Hell and Rosenfeld studied the complexity of finding various oriented paths in tournaments by probing edge directions. Here, we investigate the complexity of finding a vertex of prescribed outdegree (or indegree) in the same model. We show that the complexity of finding a vertex of outdegree k( ≤ (n − 1)/2) in T<SUB>n</SUB> is Θ(nk). This bound is in sharp contrast to the Θ(n) bound for selection in the case of transitive tournaments. We also establish tight bounds for finding vertices of prescribed degree from the adjacency matrix of general directed/undirected graphs. These bounds generalize the classical bound of 11 for finding a sink (a vertex of outdegree 0 and indegree n − 1) in a directed graph
NYU-DOE Pressurized Fluidized Bed Combustor Facility
New York University (NYU), under a Department of Energy (DOE) Contract, has designed and constructed a sub-pilot scale Pressurized Fluidized-Bed Combustor (PFBC) Facility at the Antonio Ferri Laboratories, Westbury, Long Island. The basic feature of this Experimental Research Facility is a well-instrumented, 30-inch diameter coal combustor capable of operating up to 10 atm and provided with a liberal number of ports, making it a versatile unit for study of fundamental in-bed phenomena. Additionally, the overall design features make it a flexible facility for solving a variety of industrial research problems. The main objectives of the facility are two-fold: (1) to perform research in important areas of Pressurized Fluidized-Bed Combustion like low-grade fuel combustion under pressure; and (2) to provide the PFBC community with a experimental research tool for basic and applied research in order to accelerate the commercialization of this technology. New York University will initially test the facility of burning low-grade fuels under pressure. During the test program, emphasis will be placed on burning North Dakota lignite under pressures up to 7 atm. The performance of lignite with regard to its feeding, combustion efficiency, sulfur adsorption and sorbent requirements will be investigated. This report describes the various systems of the PFBC facility and operating procedures, and presents an outline of the test program planned for the facility. Other details are provided in the Equipment and Maintenance Manual, Test Program and Data Acquisition Manual, and Training Manual
On the Existence of the Plateau Emission in High-energy Gamma-Ray Burst Light Curves Observed by Fermi-LAT
The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi) shows long-lasting high-energy emission in many gamma-ray bursts (GRBs), similar to X-ray afterglows observed by the Neil Gehrels Swift Observatory (Swift). Some LAT light curves (LCs) show a late-time flattening reminiscent of X-ray plateaus. We explore the presence of plateaus in LAT temporally extended emission analyzing GRBs from the second Fermi-LAT GRB Catalog from 2008 to 2016 May with known redshifts, and check whether they follow closure relations corresponding to four distinct astrophysical environments predicted by the external forward shock model. We find that three LCs can be fit by the same phenomenological model used to fit X-ray plateaus and show tentative evidence for the existence of plateaus in their high-energy extended emission. The most favorable scenario is a slow-cooling regime, whereas the preferred density profile for each GRBs varies from a constant-density interstellar medium to an r-2 wind environment. We also compare the end time of the plateaus in γ-rays and X-rays using a statistical comparison with 222 Swift GRBs with plateaus and known redshifts from 2005 January to 2019 August. Within this comparison, the case of GRB 090510 shows an indication of chromaticity at the end time of the plateau. Finally, we update the 3D fundamental plane relation among the rest-frame end time of the plateau, its correspondent luminosity, and the peak prompt luminosity for 222 GRBs observed by Swift. We find that these three LAT GRBs follow this relation
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A Population of Heavily Reddened, Optically Missed Novae from Palomar Gattini-IR: Constraints on the Galactic Nova Rate
The nova rate in the Milky Way remains largely uncertain, despite its vital importance in constraining models of Galactic chemical evolution as well as understanding progenitor channels for Type Ia supernovae. The rate has been previously estimated to be in the range of ≈10-300 yr-1, either based on extrapolations from a handful of very bright optical novae or the nova rates in nearby galaxies; both methods are subject to debatable assumptions. The total discovery rate of optical novae remains much smaller (≈5-10 yr-1) than these estimates, even with the advent of all-sky optical time-domain surveys. Here, we present a systematic sample of 12 spectroscopically confirmed Galactic novae detected in the first 17 months of Palomar Gattini-IR (PGIR), a wide-field near-infrared time-domain survey. Operating in the J band (≈1.2 μm), which is significantly less affected by dust extinction compared to optical bands, the extinction distribution of the PGIR sample is highly skewed to a large extinction values (>50% of events obscured by A V ⪆ 5 mag). Using recent estimates for the distribution of Galactic mass and dust, we show that the extinction distribution of the PGIR sample is commensurate with dust models. The PGIR extinction distribution is inconsistent with that reported in previous optical searches (null-hypothesis probability <0.01%), suggesting that a large population of highly obscured novae have been systematically missed in previous optical searches. We perform the first quantitative simulation of a 3π time-domain survey to estimate the Galactic nova rate using PGIR, and derive a rate of yr-1. Our results suggest that all-sky near-infrared time-domain surveys are well poised to uncover the Galactic nova population. © 2021. The American Astronomical Society. All rights reserved..Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]