63 research outputs found
Ready for O4 II: GRANDMA Observations of Swift GRBs during eight-weeks of Spring 2022
We present a campaign designed to train the GRANDMA network and its
infrastructure to follow up on transient alerts and detect their early
afterglows. In preparation for O4 II campaign, we focused on GRB alerts as they
are expected to be an electromagnetic counterpart of gravitational-wave events.
Our goal was to improve our response to the alerts and start prompt
observations as soon as possible to better prepare the GRANDMA network for the
fourth observational run of LIGO-Virgo-Kagra (which started at the end of May
2023), and future missions such as SM. To receive, manage and send out
observational plans to our partner telescopes we set up dedicated
infrastructure and a rota of follow-up adcates were organized to guarantee
round-the-clock assistance to our telescope teams. To ensure a great number of
observations, we focused on Swift GRBs whose localization errors were generally
smaller than the GRANDMA telescopes' field of view. This allowed us to bypass
the transient identification process and focus on the reaction time and
efficiency of the network. During 'Ready for O4 II', 11 Swift/INTEGRAL GRB
triggers were selected, nine fields had been observed, and three afterglows
were detected (GRB 220403B, GRB 220427A, GRB 220514A), with 17 GRANDMA
telescopes and 17 amateur astronomers from the citizen science project
Kilonova-Catcher. Here we highlight the GRB 220427A analysis where our
long-term follow-up of the host galaxy allowed us to obtain a photometric
redshift of , its lightcurve elution, fit the decay slope of the
afterglows, and study the properties of the host galaxy
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
GRANDMA and HXMT Observations of GRB 221009A -- the Standard-Luminosity Afterglow of a Hyper-Luminous Gamma-Ray Burst
GRB 221009A is the brightest Gamma-Ray Burst (GRB) detected in more than 50
years of study. In this paper, we present observations in the X-ray and optical
domains after the GRB obtained by the GRANDMA Collaboration (which includes
observations from more than 30 professional and amateur telescopes) and the
Insight-HXMT Collaboration. We study the optical afterglow with empirical
fitting from GRANDMA+HXMT data, augmented with data from the literature up to
60 days. We then model numerically, using a Bayesian approach, the GRANDMA and
HXMT-LE afterglow observations, that we augment with Swift-XRT and additional
optical/NIR observations reported in the literature. We find that the GRB
afterglow, extinguished by a large dust column, is most likely behind a
combination of a large Milky-Way dust column combined with moderate
low-metallicity dust in the host galaxy. Using the GRANDMA+HXMT-LE+XRT dataset,
we find that the simplest model, where the observed afterglow is produced by
synchrotron radiation at the forward external shock during the deceleration of
a top-hat relativistic jet by a uniform medium, fits the multi-wavelength
observations only moderately well, with a tension between the observed temporal
and spectral evolution. This tension is confirmed when using the extended
dataset. We find that the consideration of a jet structure (Gaussian or
power-law), the inclusion of synchrotron self-Compton emission, or the presence
of an underlying supernova do not improve the predictions, showing that the
modelling of GRB22109A will require going beyond the most standard GRB
afterglow model. Placed in the global context of GRB optical afterglows, we
find the afterglow of GRB 221009A is luminous but not extraordinarily so,
highlighting that some aspects of this GRB do not deviate from the global known
sample despite its extreme energetics and the peculiar afterglow evolution.Comment: Accepted to ApJL for the special issue, 37 pages, 23 pages main text,
6 tables, 13 figure
The GRANDMA network in preparation for the fourth gravitational-wave observing run
GRANDMA is a world-wide collaboration with the primary scientific goal ofstudying gravitational-wave sources, discovering their electromagneticcounterparts and characterizing their emission. GRANDMA involves astronomers,astrophysicists, gravitational-wave physicists, and theorists. GRANDMA is now atruly global network of telescopes, with (so far) 30 telescopes in bothhemispheres. It incorporates a citizen science programme (Kilonova-Catcher)which constitutes an opportunity to spread the interest in time-domainastronomy. The telescope network is an heterogeneous set of already-existingobserving facilities that operate coordinated as a single observatory. Withinthe network there are wide-field imagers that can observe large areas of thesky to search for optical counterparts, narrow-field instruments that dotargeted searches within a predefined list of host-galaxy candidates, andlarger telescopes that are devoted to characterization and follow-up of theidentified counterparts. Here we present an overview of GRANDMA after the thirdobserving run of the LIGO/VIRGO gravitational-wave observatories in and its ongoing preparation for the forthcoming fourth observational campaign(O4). Additionally, we review the potential of GRANDMA for the discovery andfollow-up of other types of astronomical transients.<br
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
On Evaluation of the Statistical Error in Measuring the Reactor Period and Reactivity in Case of a Drift-Type Disturbance
Automation of the analysis of resonance vibrations of mechanical systems in vibration tests
Nonlinear dynamics of a multimode laser with stimulated Mandel'shtam-Brillouin scattering in the active medium
Estimation of parameters of interference concentrated in spectrum at the output of LFM iono-probe receiver
Aicardi–Goutieres syndrome in children with idiopathic epilepsy
This article describes 9 clinical cases of Aicardi–Goutières syndrome (AGS) in children admitted to the hospital of the Scientific and Practical Center of Medical Care for Children with Resistant Multifocal Epilepsy. Epilepsy, psychomotor retardation, and a loss of previously acquired skills were diagnosed during the investigation. Targeted exome sequencing in one child revealed a mutation in the RNASEH2B gene responsible for the development of this disease. AGS is an early-onset progressive encephalopathy with basal ganglia calcification, leukodystrophy, lymphocytosis, elevated interferon-alfa levels in the cerebrospinal fluid, and no evidence of viral infection. Noninfectious leukoencephalopathy concurrent with multifocal epilepsy in early childhood suggest that the syndrome is an inherited disease
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