5,335 research outputs found
On the consistency of the peculiar GRBs 060218 and 060614 with the Ep,i - Eiso correlation
We analyze and discuss the position of GRB 060218 and GRB 060614 in the Ep,i
- Eiso plane. GRB 060218 is important because of its similarity with GRB
980425, the proto-type event of the GRB-SN connection. While GRB 980425 is an
outlier of the Ep,i - Eiso correlation, we find that GRB 060218 is fully
consistent with it. This evidence, combined with the `chromatic' behavior of
the afterglow light curves, is at odds with the hypothesis that GRB 060218 was
a `standard' GRB seen off-axis and supports the existence of a class of truly
sub--energetic GRBs. GRB 060614 is a peculiar event not accompanied by a bright
Supernova. Based on published spectral information, we find that also this
event is consistent with the Ep,i - Eiso correlation. We discuss the
implications of our results for the rate of sub--energetic GRBs, the GRB/SN
connection and the properties of the newly discovered sub-class of long GRBs
not associated with bright Supernovae. We have included in our analysis other
recent GRBs with clear evidence (or clear no evidence) of associated SNe.Comment: 9 pages, 4 figures, FINAL REVISED VERSION (added Figure 4 and short
GRBs in Figure 1; minor changes and style corrections applied; references
updated), submitted to A&A on November 25, 200
GRB 000911: Evidence for an Associated Supernova?
We present photometric and spectroscopic observations of the late afterglow of GRB 000911. We detect a moderately significant re-brightening in the R, I and J lightcurves, associated with a sizable reddening of the spectrum. This can be explained through the presence of an underlying supernova, outshining the afterglow ~ 30 days after the burst event
The Optical SN 2012bz Associated with the Long GRB 120422A
The association of Type Ic SNe with long-duration GRBs is well established.
We endeavor, through accurate ground-based observational campaigns, to
characterize these SNe at increasingly high redshifts. We obtained a series of
optical photometric and spectroscopic observations of the Type Ic SN2012bz
associated with the Swift long-duration GRB120422A (z=0.283) using the 3.6-m
TNG and the 8.2-m VLT telescopes. The peak times of the light curves of
SN2012bz in various optical filters differ, with the B-band and i'-band light
curves reaching maximum at ~9 and ~23 rest-frame days, respectively. The
bolometric light curve has been derived from individual bands photometric
measurements, but no correction for the unknown contribution in the
near-infrared (probably around 10-15%) has been applied. Therefore, the present
light curve should be considered as a lower limit to the actual UV-optical-IR
bolometric light curve. This pseudo-bolometric curve reaches its maximum (Mbol
= -18.56 +/- 0.06) at 13 +/- 1 rest-frame days; it is similar in shape and
luminosity to the bolometric light curves of the SNe associated with z<0.2 GRBs
and more luminous than those of SNe associated with XRFs. A comparison with the
model generated for the bolometric light curve of SN2003dh suggests that
SN2012bz produced only about 15% less 56Ni than SN2003dh, about 0.35 Msol.
Similarly the VLT spectra of SN2012bz, after correction for Galactic extinction
and for the contribution of the host galaxy, suggest comparable explosion
parameters with those observed in SN2003dh (EK~3.5 x 10^52 erg, Mej~7 Msol) and
a similar progenitor mass (~25-40 Msol). GRB120422A is consistent with the
Epeak-Eiso and the EX,iso-Egamma,iso-E_peak relations. GRB120422A/SN2012bz
shows the GRB-SN connection at the highest redshift so far accurately monitored
both photometrically and spectroscopically.Comment: 7 pages, 6 figures, 2 tables, accepted for publication in Astronomy &
Astrophysic
POS1247 CLINICAL FEATURES AND OUTCOMES OF COVID-19 IN PATIENTS WITH IGG4-RELATED DISEASE. A COLLABORATIVE EUROPEAN MULTI-CENTRE STUDY
Background:Coronavirus disease 2019 (COVID-19) is a pandemic-spread systemic infectious disease with prominent respiratory manifestations and significant associated morbidity and mortality. Elderly people are most significantly affected with mortality ranging from 2.4% (age 60-69) to 19.6% (age>80) in European Countries. The prevalence of COVID-19 and of its complications in patients with immune-mediated disorders, remains unclear. The frequency and impact of COVID-19 on patients with IgG4-related diease (IgG4-RD), many of whom are on concurrent immunosuppression has not been addressed.Objectives:To assess the epidemiological and clinical relevance of COVID-19 in patients with IgG4-RD.Methods:This is a multi-centre retrospective observational study of IgG4-RD patients from France, Italy, Spain and the United Kingdom. Demographics, comorbidities, IgG4-RD features, current and past treatment along with COVID-19-suggestive symptoms and COVID-19 diagnoses from February 2020 to January 2021 were recorded by means of direct or phone interviews. Patients with reverse-transcriptase polymerase chain reaction-confirmed (cCOVID) or presumed COVID-19 based on clinical, serological or imaging features (pCOVID) were pooled for analysis (totCOVID) and compared to patients who were not diagnosed with COVID-19. Inter-group comparison of categorical and quantitative variables were performed by using the chi-square test with Fisher's correction and the Mann-Whitney's test respectively. Data are expressed as median (interquartile range) unless otherwise specified.Results:A total of 305 patients [71% males, median age 64 (54-74) years] were studied. Pancreato-biliary disease was the most frequently observed IgG4-RD phenotype (39%). Fifty-one percent of patients were taking corticosteroids at time of interview and 30% were on biological or conventional immunosuppressants. Thirty-two totCOVID cases (23 cCOVID, nine pCOVID) were identified: 11/32 were hospitalised, two needed intensive care and four (13%; 3/4 aged >80 years) died. Having one or more infected family members was a risk factor for COVID-19 in patients with IgG4-RD (OR=19.9; p20mg) or rituximab administration.Conclusion:The prevalence and course of COVID-19 in IgG4-RD patients are similar to those of the general population of the same age, with no evident impact of disease- or treatment-related factors to the basal infectious risk. Effective public health countermeasures might be beneficial for patients with IgG4RD.References:[1]European Centre for Disease Prevention and Control (ECDC): https://covid19-surveillance-report.ecdc.europa.eu/[2]Yang H, Ann Rheum Dis, 2021Disclosure of Interests:Giuseppe Alvise Ramirez: None declared, Marco Lanzillotta: None declared, Mikael Ebbo: None declared, Andreu Fernandez-Codina Consultant of: consulting fees from Atheneum Consulting, Gaia Mancuso: None declared, Fernando Martínez-Valle: None declared, Olimpia Orozco-Galvez: None declared, Nicolas Schleinitz: None declared, Lorenzo Dagna Consultant of: Abbvie, Amgen, Biogen, BristolMyers Squibb, Celltrion, Galapagos, GlaxoSmithKline, Novartis, Pfizer, Roche, Sanofi-Genzyme, and SOBI, Grant/research support from: The Unit of Immunology, Rheumatology, Allergy and Rare Diseases (UnIRAR) received unresctricted research/educational grants from Abbvie, Bristol-Myers Squibb, Celgene, GlaxoSmithKline,Janssen, Merk Sharp & Dohme, Mundipharma Pharmaceuticals, Novartis, Pfizer, Roche, Sanofi Genzyme, and SOBI, Emma L. Culver: None declared, Emanuel Della Torre: None declare
The optical afterglow of GRB 000911: evidence for an associated supernova?
We present photometric and spectroscopic observations of the late afterglow
of GRB 000911, starting ~1 day after the burst event and lasting ~8 weeks. We
detect a moderately significant re-brightening in the R, I and J lightcurves,
associated with a sizable reddening of the spectrum. This can be explained
through the presence of an underlying supernova, outshining the afterglow ~30
days after the burst event. Alternative explanations are discussed.Comment: 7 pages, 3 postscript figures, A&A in pres
Unveiling the origin of X-ray flares in Gamma-Ray Bursts
We present an updated catalog of 113 X-ray flares detected by Swift in the
~33% of the X-ray afterglows of Gamma-Ray Bursts (GRB). 43 flares have a
measured redshift. For the first time the analysis is performed in 4 different
X-ray energy bands, allowing us to constrain the evolution of the flare
temporal properties with energy. We find that flares are narrower at higher
energies: their width follows a power-law relation w~E^{-0.5} reminiscent of
the prompt emission. Flares are asymmetric structures, with a decay time which
is twice the rise time on average. Both time scales linearly evolve with time,
giving rise to a constant rise-to-decay ratio: this implies that both time
scales are stretched by the same factor. As a consequence, the flare width
linearly evolves with time to larger values: this is a key point that clearly
distinguishes the flare from the GRB prompt emission. The flare 0.3-10 keV peak
luminosity decreases with time, following a power-law behaviour with large
scatter: L_{pk}~ t_{pk}^{-2.7}. When multiple flares are present, a global
softening trend is established: each flare is on average softer than the
previous one. The 0.3-10 keV isotropic energy distribution is a log-normal
peaked at 10^{51} erg, with a possible excess at low energies. The flare
average spectral energy distribution (SED) is found to be a power-law with
spectral energy index beta~1.1. These results confirmed that the flares are
tightly linked to the prompt emission. However, after considering various
models we conclude that no model is currently able to account for the entire
set of observations.Comment: MNRAS submitte
GRB 080319B: A Naked-Eye Stellar Blast from the Distant Universe
Long duration gamma-ray bursts (GRBs) release copious amounts of energy
across the entire electromagnetic spectrum, and so provide a window into the
process of black hole formation from the collapse of a massive star. Over the
last forty years, our understanding of the GRB phenomenon has progressed
dramatically; nevertheless, fortuitous circumstances occasionally arise that
provide access to a regime not yet probed. GRB 080319B presented such an
opportunity, with extraordinarily bright prompt optical emission that peaked at
a visual magnitude of 5.3, making it briefly visible with the naked eye. It was
captured in exquisite detail by wide-field telescopes, imaging the burst
location from before the time of the explosion. The combination of these unique
optical data with simultaneous gamma-ray observations provides powerful
diagnostics of the detailed physics of this explosion within seconds of its
formation. Here we show that the prompt optical and gamma-ray emissions from
this event likely arise from different spectral components within the same
physical region located at a large distance from the source, implying an
extremely relativistic outflow. The chromatic behaviour of the broadband
afterglow is consistent with viewing the GRB down the very narrow inner core of
a two-component jet that is expanding into a wind-like environment consistent
with the massive star origin of long GRBs. These circumstances can explain the
extreme properties of this GRB.Comment: 43 pages, 18 figures, 3 tables, submitted to Nature May 11, 200
Late-epoch optical and near-infrared observations of the GRB000911 afterglow and its host galaxy
We present the results of an optical and near-infrared (NIR) monitoring
campaign of the counterpart of Gamma-Ray Burst (GRB) 000911, located at
redshift z=1.06, from 5 days to more than 13 months after explosion. Our
extensive dataset is a factor of 2 larger and spans a time interval about 4
times longer than the ones considered previously for this GRB afterglow; this
allows a more thorough analysis of its light curve and of the GRB host galaxy
properties. The afterglow light curves show a single power-law temporal
decline, modified at late times by light from a host galaxy with moderate
intrinsic extinction, and possibly by an emerging supernova (SN). The afterglow
evolution is interpreted within the classical "fireball" scenario as a weakly
collimated adiabatic shock propagating in the interstellar medium. The presence
of a SN light curve superimposed on the non-thermal afterglow emission is
investigated: while in the optical bands no significant contribution to the
total light is found from a SN, the NIR J-band data show an excess which is
consistent with a SN as bright as the known hypernova SN1998bw. If the SN
interpretation is true, this would be the farthest GRB-associated SN, as well
as the farthest core-collapse SN, discovered to date. However, other possible
explanations of this NIR excess are also investigated. Finally, we studied the
photometric properties of the host, and found that it is likely to be a
slightly reddened, subluminous, extreme starburst compact galaxy, with
luminosity about 0.1 L*, an age of about 0.5 Gyr and a specific Star Formation
Rate (SFR) of approximately 30 Msol yr-1 (L/L*)-1. This is the highest specific
SFR value for a GRB host inferred from optical/NIR data.Comment: 13 pages, 6 figures, 3 tables. Accepted for publication in A&A, main
journa
Observational Constraints on the Angular and Spectral Distributions of Photons in Gamma-Ray Burst Sources
The typical spectra of gamma-ray bursts (GRBs) are discussed in the context
of the compactness problem for GRB sources and how it is resolved in the
popular fireball model. In particular, observational (model-independent)
constraints on the collimation of the gamma-rays and the dependence of the
collimation angle on the photon energy are considered. The fact that the
threshold for the creation of pairs depends on the angle between
the momenta of the annihilating photons in the GRB source provides an
alternative solution to the compactness problem. A new approach to explaining
GRBs, taking into account the angular dependence for pair creation, is
proposed, and the main features of a scenario describing a GRB source with a
total (photon) energy smaller or of the order of erg are laid out.
Thus, we are dealing with an alternative to an ultra-relativistic fireball, if
it turns out (as follows from observations) that all "long" GRBs are associated
with normal (not peculiar) core-collapse supernovae. The effects of radiation
pressure and the formation of jets as a consequence of even a small amount of
anisotropy in the total radiation field in a (compact) GRB source are examined
in this alternative model. Possible energy release mechanisms acting in regions
smaller or of the order of cm in size (a compact model for a GRB) are
discussed. New observational evidence for such compact energy release in the
burst source is considered.Comment: 15 pages, no figures, no table
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