A Reverse Shock in GRB 181201A Laskar, Tanmoy; Eerten, Hendrik van; Schady, Patricia ...
Astrophysical journal/The Astrophysical journal,
10/2019, Volume:
884, Issue:
2
Journal Article
Peer reviewed
Open access
We present comprehensive multiwavelength radio to X-ray observations of GRB 181201A spanning from 150 s to 163 days after the burst, comprising the first joint ALMA-VLA-GMRT observations of a ...gamma-ray burst (GRB) afterglow. The radio and millimeter-band data reveal a distinct signature at 3.9 days, which we interpret as reverse-shock (RS) emission. Our observations present the first time that a single radio-frequency spectral energy distribution can be decomposed directly into RS and forward shock (FS) components. We perform detailed modeling of the full multiwavelength data set, using Markov Chain Monte Carlo sampling to construct the joint posterior density function of the underlying physical parameters describing the RS and FS synchrotron emission. We uncover and account for all discovered degeneracies in the model parameters. The joint RS-FS modeling reveals a weakly magnetized ( 3 × 10−3), mildly relativistic RS, from which we derive an initial bulk Lorentz factor of Γ0 103 for the GRB jet. Our results support the hypothesis that low-density environments are conducive to the observability of RS emission. We compare our observations to other events with strong RS detections and find a likely observational bias selecting for longer lasting, nonrelativistic RSs. We present and begin to address new challenges in modeling posed by the present generation of comprehensive, multifrequency data sets.
ABSTRACT
We report on results of spectropolarimetry of the afterglow of the long gamma-ray burst GRB 191221B, obtained with SALT/RSS and VLT/FORS2, as well as photometry from two telescopes in the ...MASTER Global Robotic Network, at the MASTER-SAAO (South Africa) and MASTER-OAFA (Argentina) stations. Prompt optical emission was detected by MASTER-SAAO 38 s after the alert, which dimmed from a magnitude (white-light) of ∼10–16.2 mag over a period of ∼10 ks, followed by a plateau phase lasting ∼10 ks and then a decline to ∼18 mag after 80 ks. The light curve shows complex structure, with four or five distinct breaks in the power-law decline rate. SALT/RSS linear spectropolarimetry of the afterglow began ∼2.9 h after the burst, during the early part of the plateau phase of the light curve. Absorption lines seen at ∼6010 and 5490 Å are identified with the Mg ii 2799 Å line from the host galaxy at z = 1.15 and an intervening system located at z = 0.96. The mean linear polarization measured over 3400–8000 Å was ∼1.5 per cent and the mean equatorial position angle (θ) was ∼65°. VLT/FORS2 spectropolarimetry was obtained ∼10 h post-burst, during a period of slow decline (α = −0.44), and the polarization was measured to be p = 1.2 per cent and θ = 60°. Two observations with the MeerKAT radio telescope, taken 30 and 444 d after the GRB trigger, detected radio emission from the host galaxy only. We interpret the light curve and polarization of this long GRB in terms of a slow-cooling forward shock.
The article presents 3 cohorts with early rheumatoid arthritis in patients aged 50 years and older with a disease duration from 1.5 months to 1 year. To establish a diagnosis, the classification ...criteria of its period were applied to each of the cohorts: to the 1st - the 1958 ARA criteria, to the 2nd – the 1987 ARA criteria, to the 3rd - the 2010 ACR / EULAR criteria. Along with changes in the criteria diagnostic methods improved, many qualitative laboratory indicators were replaced by a quantitative equivalent; new disease markers (including ACPA), improved imaging methods, changed treatment strategies, genetically engineered drugs, numerous analogues of the original drugs appeared. Сonflicting opinions about the course of RA in older age periods have been published in the literature consistently. During application of the 1958 classification criteria, the prevailing opinion was that these patients had a more favorable course; as a more hardline approach to RA diagnosing appeared, a growing number of supporters of its more severe course appeared. In the research the author tries to answer the question whether the course of the disease in the older age groups has changed at the earliest time from its beginning by comparing three cohorts of different time periods. The data obtained are discussed.
The paper presents the materials of the Russian Arthritis Registry (OREL) that includes 3276 patients from 11 Russian Federation's largest research-and-practical centers situated in Moscow, Saint ...Petersburg, Novosibirsk, Kazan, Tula, Yaroslavl, Tyumen. It discusses the main goals of setting up registries, compares the results of an analysis of the data available in the Russian Registry OREL and registries of European countries and the USA. The findings suggest that there is non-uniform information on clinical, laboratory, and instrumental parameters in the national registers of a numberof European countries and the USA. According to its basic characteristics, the Russian Registry OREL compares favorably with a number of other registries in the completeness of data collection, which allows a general idea of rheumatoid arthritis (RA) patients in Russia. For further development of the OREL Registry, it is necessary to concentrate our attention on the following main areas: to improve the quality of filling out documents; to follow-up patients receiving different RA therapy regimens according to the guidelines of the Association of Rheumatologists of Russia for the treatment of RA; to conduct in-depth studies of comorbidity, primarily depressive disorders; to analyze adverse reactions that make RA therapy difficult; to actively use modules for patients' self-rating of their condition; to develop nursing care, etc.
N-body dynamical simulations are used to analyze the conditions for the gravitational stability of a three-dimensional stellar disk in the gravitational field of two rigid spherical components--a ...bulge and halo whose central concentrations and relative masses vary over wide ranges. The number of point masses N in the simulations varies from 40 to 500 000 and the evolution of the simulated systems is followed over 10-20 rotation periods of the outer edge of the disk. The initially unstable disks are heated and, as a rule, reach a quasi-stationary equilibrium with a steady-state radial-velocity dispersion c sub(r) over five to eight turns. The radial behavior of the Toomre stability parameter Q sub(T)(r) for the final state of the disk is estimated. Simple models are used to analyze the dependence of the gravitational stability of the disk on the relative masses of the spherical components, disk thickness, degree of differential rotation, and initial state of the disk. Formal application of existing, analytical, local criteria for marginal stability of the disk can lead to errors in c sub(r) of more than a factor of 1.5. It is suggested that the approximate constancy of Q sub(T)1.2-1.5 for r(1-2)L (where L is the radial scale of disk surface density), valid for a wide range of models, can be used to estimate upper limits for the mass and density of a disk based on the observed distributions of the rotational velocity of the gaseous component and of the stellar velocity dispersion.
How to help smoking patients: new opportunities R. G. Oganov; G. Ya. Maslennikova; T. V. Tyurina ...
Kardiovaskuli͡a︡rnai͡a︡ terapii͡a︡ i profilaktika,
01/2011, Volume:
10, Issue:
5
Journal Article
Programmed ferroptotic death eliminates cells in all major organs and tissues with imbalanced redox metabolism due to overwhelming iron-catalyzed lipid peroxidation under insufficient control by ...thiols (Glutathione (GSH)). Ferroptosis has been associated with the pathogenesis of major chronic degenerative diseases and acute injuries of the brain, cardiovascular system, liver, kidneys, and other organs, and its manipulation offers a promising new strategy for anticancer therapy. This explains the high interest in designing new small-molecule-specific inhibitors against ferroptosis. Given the role of 15-lipoxygenase (15LOX) association with phosphatidylethanolamine (PE)-binding protein 1 (PEBP1) in initiating ferroptosis-specific peroxidation of polyunsaturated PE, we propose a strategy of discovering antiferroptotic agents as inhibitors of the 15LOX/PEBP1 catalytic complex rather than 15LOX alone. Here we designed, synthesized, and tested a customized library of 26 compounds using biochemical, molecular, and cell biology models along with redox lipidomic and computational analyses. We selected two lead compounds, FerroLOXIN-1 and 2, which effectively suppressed ferroptosis in vitro and in vivo without affecting the biosynthesis of pro-/anti-inflammatory lipid mediators in vivo. The effectiveness of these lead compounds is not due to radical scavenging or iron-chelation but results from their specific mechanisms of interaction with the 15LOX-2/PEBP1 complex, which either alters the binding pose of the substrate eicosatetraenoyl-PE (ETE-PE) in a nonproductive way or blocks the predominant oxygen channel thus preventing the catalysis of ETE-PE peroxidation. Our successful strategy may be adapted to the design of additional chemical libraries to reveal new ferroptosis-targeting therapeutic modalities.
Available velocity dispersion estimates for the old stellar population of galactic disks at galactocentric distances r2L (where L is the photometric radial scale length of the disk) are used to ...determine the threshold local surface density of disks that are stable against gravitational perturbations. The mass of the disk M^sub d^ calculated under the assumption of its marginal stability is compared with the total mass M^sub t^ and luminosity L^sub B^ of the galaxy within r=4L. We corroborate the conclusion that a substantial fraction of the mass in galaxies is probably located in their dark halos. The ratio of the radial velocity dispersion to the circular velocity increases along the sequence of galactic color indices and decreases from the early to late morphological types. For most of the galaxies with large color indices (B-V)^sub 0^>0.75, which mainly belong to the S0 type, the velocity dispersion exceeds significantly the threshold value required for the disk to be stable. The reverse situation is true for spiral galaxies: the ratios M^sub d^/L^sub B^ for these agree well with those expected for evolving stellar systems with the observed color indices. This suggests that the disks of spiral galaxies underwent no significant dynamical heating after they reached a quasi-equilibrium stable state.PUBLICATION ABSTRACT
The early afterglow of GRB 190829A Dichiara, S; Troja, E; Lipunov, V ...
Monthly Notices of the Royal Astronomical Society,
03/2022, Volume:
512, Issue:
2
Journal Article
Peer reviewed
Open access
ABSTRACT
GRB 190829A at z = 0.0785 is the fourth closest long GRB ever detected by the Neil Gehrels Swift observatory, and the third confirmed case with a very high-energy component. We present our ...multiwavelength analysis of this rare event, focusing on its early stages of evolution, and including data from Swift, the MASTER global network of optical telescopes, ALMA, and ATCA. We report sensitive limits on the linear polarization of the optical emission, disfavouring models of off-axis jets to explain the delayed afterglow peak. The study of the multiwavelength light curves and broad-band spectra supports a model with at least two emission components: a bright reverse shock emission, visible at early times in the optical and X-rays and, later, in the radio band; and a forward shock component dominating at later times and lower radio frequencies. A combined study of the prompt and afterglow properties shows many similarities with cosmological long GRBs, suggesting that GRB 190829A is an example of classical GRBs in the nearby universe.
We present the results of our
UBVRI
CCD photometry for the second brightest supernova of 2009, SN 2009nr, discovered during a sky survey with the telescopes of the MASTER robotic network. Its light ...and color curves and bolometric light curves have been constructed. The light-curve parameters and the maximum luminosity have been determined. SN 2009nr is shown to be similar in light-curve shape and maximum luminosity to SN 1991T, which is the prototype of the class of supernovae Ia with an enhanced luminosity. SN 2009nr exploded far from the center of the spiral galaxy UGC 8255 and most likely belongs to its old halo population. We hypothesize that this explosion is a consequence of the merger of white dwarfs.
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