Several thousands of gamma-ray bursts were observed by various experiments. During several GRBs very high-energy photons were detected both in space and ground-based experiments (up to some tens of ...GeV and up to some TeV, respectively). Usually 2 classes of bursts are considered: short and long GRBs separated by t90~2s. Because of several hundreds of GRBs located at high redshift, its sources' origins nature concluding as cosmological. Therefore correction to cosmological dilation of GRBs t90 should be considered during any analysis of bursts duration. Firstly very high-energy component was observed during GRB 970417a: 18 photons with energy ~650 GeV were registered by Milagrito within t90 interval of this burst. Now several tens of GRBs reveal activity in energy bands up to some tens of GeV and up to some TeV accordingly data of space and ground-based experiments correspondingly. Unfortunately redshift is unknown approximately for half of GRBs with high energy component presence. Here we introduce new parameter Rt is ratio of maximum energy photon arrival time to burst duration and it not required cosmological correction. At least 2 groups of long GRBs could be separated using parameter Rt: for 25% events highest energy gammas detected within t90 interval, but for other 75% of bursts it registered more than 10 sec. later than one. Moreover, preliminary results of analysis allow concluding 2 subtypes of second group GRBs. For one μ-quantum with maximum energy arrived within t90. For other such photon was registered later than t90. Therefore, the results of preliminary analyses allow conclude long GRBs population inhomogeneity.
Large articles amount refers to GRBs (at least long ones) as standard candles and then concludes various cosmological consequences. But firstly long GRBs sources population homogeneity should be ...proved. Redshift distribution analysis should represent GRBs population homogeneity if its shape similar to one of objects with real uniform distribution in our Metagalaxy, such as SN1a (subsets of 42 and 53 ones used for its Ω and Λ definition). There are one maximum in each subset redshifts distributions. Typically considered short and long GRBs classes separated by t90=2s. Moreover, registered event duration strongly depends on detector energy band and method used for temporal profile analysis and the same events could have different duration on various detectors data. GRBs mostly located at high redshifts and cosmological correction should be used in duration investigation. Redshift distribution for registered by Swift/BAT GRBs with t90>1s (corrected to z) was analyzed with short GRBs exclusion. But its redshift distribution is sufficiently differs from ones for SN1a: bursts deficit occur at z∼2, possibly caused by long GRBs population inhomogeneity. So, preliminary analyses results allow conclude long GRBs population inhomogeneity. Thus using GRBs as "standard candles" previously required events advanced classification completion and consideration only certain GRBs subsets.
Sources of gamma-ray bursts (GRBs) are detected at a high redshift
z
, testifying to their cosmological origin and thus requiring allowance for cosmological dilation in analyzing the distribution of ...their durations. New parameter
R
t
, the ratio of the arrival time of a maximum-energy photon to the duration of a burst, is introduced. The new parameter allows cosmological dilation to be ignored and at least two groups of long GRBs to be distinguished. Differences in the dynamics of the formation of high-energy γ-radiation for these groups demonstrates the inhomogeneity of their source populations.
The future space-based GAMMA-400
-ray telescope will operate onboard the Russian astrophysical observatory in a highly elliptic orbit during 7 years. Observing
-ray sources from Galactic plane,
-ray ...bursts,
-ray diffuse emission,
rays from the Sun, and
rays from dark matter particles will be performed uninterruptedly for a long time (
100 days) in point-source mode in contrast to scanning mode for Fermi-LAT and other space- and ground-based instruments. GAMMA-400 will measure
rays in the energy range from
20 MeV to several TeV units, have the unprecedented angular (
at
GeV) and energy (
at
GeV) resolutions better than for Fermi-LAT, as well as ground-based
-ray facilities, by a factor of 5–10, and perfectly separate
rays from cosmic-ray background.
Firstly GRB duration distribution was analyzed on data of BATSE experiment onboard the Compton Gamma Ray Observatory (CGRO) operated from April 1991 until to June 2000. Usually two GRBs groups ...separated in duration distribution: short and long. These types of events are classified due to analysis of duration of interval where integrated counts from the GRB raising from 5% to 95% (t90). The value t90 ∼ 2s is used as boundary between short and long events. However, in 1999 third burst subgroup (intermediate GRBs) was found due to GRBs duration and duration-hardness distributions analysis of 4B current BATSE catalogue (recently available as 5B one) in time interval of 0.8 s ≤ t90≤ 50 s. Since CGRO operation has finished, two satellite experiments GRBs catalogues BAT/Swift and GBM/Fermi contain the amount of bursts comparable with 4B current BATSE catalogue and it is sufficient for duration distribution precision investigation. The results of these distributions analysis are discussed. It allows concluding the appearance of intermediate GRB subgroup on data of three experiments: BATSE/CGRO, BAT/Swift and GBM/Fermi.
The presence of dual structure in 13 clusters of galaxies from CfA2 Redshift Survey is discussed. The spatial distributions of galaxies and ones on absolute magnitude, luminosity, angular velocity ...and absolute magnitude, velocity and distance for cluster center reveal two areas for clusters nos. 88, 1101, 1046, 142, 933, 1242, 1652, 107, 150, 316, 317, 961, 977. The occurrence of such structure allows concluding two alternatives. In the first one dark matter presence inside cluster or their nearest neighborhoods in configuration similar to Zeldovich pancake. The second case is gravitational lensing on compact object or dark matter blob located between galaxy cluster and observer. But now several evidences against gravitational lensing were found. Firstly, the studying of Summary of Multiply Imaged Systems within CfA-Arizona Space Telescope LEns Survey of gravitational lenses gives minimum lens redshift
and maximum distance between images
arcsec. These values are in contradiction with parameters of analyzable clusters of galaxies. Maximum redshift of these clusters is 0.032, and maximum distances between galaxies reach several degrees. Secondly, the parts of dual structure of systems being studied contain sufficiently different number of spiral galaxies, but types of objects on images due lens should be similar. Then we have investigated these systems dynamic using Nonlinear Time Series Analysis. We have constructed phase space for such clusters of galaxies using values of redshift, coordinates, magnitude, absolute magnitude and distance to centre. As a timelike variable we supposed the ratio between galaxies’ tangential velocity and its distance to cluster’s centre. According to preliminary results of analysis we have obtained two attractors in the phase spaces of cluster nos. 88 and 142 with basins corresponding to bifurcation points on the analyzable distributions. Such results conclude real dual structure of systems being studied. Also, we have investigated the appearances of systems being analyzed in high-energy gamma bands. It was found that cluster nos. 933, 142, 1046, 1652 and 316 reveal high-energy
-associations on Fermi/LAT 12-Year Point Source Catalog 4FGL-DR3 (4FGL J1144.9
1937, 4FGL J0152.2
3714, 4FGL J1230.8
1223, 4FGL J1653.8
3945 and 4FGL J0708.9
4839). Moreover, sources 4FGLJ1144.9
1937, 4FGLJ1230.8
1223 and 4FGL J1653.8
3945 were registered in subTeV energy region by VERITAS. These objects should be jointly observed by ground-based Cherenkov air-shower experiments and orbital gamma-ray observatories with high angular and energy resolution better than Fermi/LAT. One of such planned orbital experiments is GAMMA-400 with angular and energy resolution
and
at
GeV and ability of registration of gamma-quanta up to several TeV. Also, the coordination of lists of multiwavelength observations of Cherenkov Telescope Array (CTA) and GAMMA-400 is discussed now. Such observations could clarify the properties of high-energy emission from 4FGL J1144.9
1937, 4FGL J1230.8
1223 and 4FGL J1653.8
3945 and its interrelation with the cluster nos. 933, 1046 and 1652.
Gamma-ray bursts duration distributions properties for events registered by experiments CGRO/BATSE, VENERA11/KONUS, VENERA12/KONUS, Swift/BAT, GRANAT/PHEBUS, Suzaku/WAM, RHESSI and Fermi/GBM are ...considered. GRBs observed since 1967 and now several thousands of events were listed in more than 30 catalogues. Gamma-ray bursts duration distribution was the first analysed using data of BATSE instrument onboard the CGRO. The GRBs duration distribution analysis had shown the existence of two bursts classes: long and short separated by t90 = 2 s. But results of similar distributions for bursts observed by other detectors have shown shifting of boundary between short and long events from value of 2 s. For example, Swift/BAT GRBs subset analysis gives the value of ∼1 s for this separator point. Moreover, t90 has dependence from instrument registered this burst - it is function of detector sensitivity threshold and operation energy band. For instance, the duration of GRB060418 burst t90 is ∼52 s according to Swift/BAT data and only 36 s according to RHESSI data. Therefore, the type of GGB (whether it short or long) should be defined only taking into account distinctive features of instrument detected this event. Also attributes of third intermediate GRBs subgroup appearance in events subsets for various detectors are discussed. Firstly this subgroup was found some years ago in BATSE GRB duration and duration-hardness distributions.
Preliminary results of the investigation of the characteristics of 5 groups of galaxies are discussed in the presented article. We have analyzed the main characteristics of galaxy clusters 933, 88, ...142, 1046, 1101 from CfA2 redshift survey. Clusters 933, 142, 1046, and 1652 have high-energy gamma associations on Fermi/LAT data (4FGL J1144.9
1937, 4FGL J0152.2
3714, 4FGL J1230.8
1223 and 4FGL J1653.8
3945). These sources are active galaxies. Furthermore, the radiogalaxy 3C 264 (4FGL J1144.9
1937) was previously observed in the energy band
TeV. We have found several anomalies of the spatial dynamics of galaxies in these clusters. These features could be caused by the dynamics of galaxies’ motion in a gravitationally bound group taking into account possible space–time inhomogeneities at large distances. Investigation of high-energy gamma-emission of galaxies and peculiarities of its motion in groups allows studying properties of such inhomogeneities and understanding of its nature possibly caused by dark matter. The investigation of the spatial distribution and other characteristics of 933, 88, 142, 1046, 1101 galaxy clusters shows gravitational lensing effect. But now it is unknown which objects are gravitational lenses for these clusters. The angular size of such clusters is about 1–2 degree and now there are not clear associations between group members of clusters 142, 1046, and 1652 with the high-energy gamma-sources 4FGL J0152.2
3714, 4FGL J1230.8
1223, and 4FGL J1653.8
3945. Common observations of such clusters by orbital gamma-ray observatories with high angular resolution and ground-based Cherenkov air-shower experiments could possibly clarify the type of gravitational lenses.
The GAMMA-400 gamma-ray telescope is planned for the launch at the end of 2026 on the Navigator service platform designed by Lavochkin Association on an elliptical orbit with following initial ...parameters: an apogee
300 000, a perigee
500 km, a rotation period
7 days and inclination of 51.4
. The apparatus is expected to operate for more than 5 years, reaching an unprecedented sensitivity for the search of dark matter signatures and the study of the unresolved and so far unidentified gamma-ray sources. The segmented anticoincidence counters surround the converter-tracker and calorimeter of the telescope with the purpose of vetoing to assure a clean track reconstruction and charged particle background suppression. The anticoincidence detector prototype based on long BC-408 scintillator with silicon photomultipliers readout was tested using 300-MeV positron beam of synchrotron C-25P ‘‘PAKHRA’’ of Lebedev Physical Institute. The measurement setup, design concepts for the prototype detector together with test results are discussed.
Cosmophysical Research with GAMMA-400 Topchiev, N. P.; Galper, A. M.; Arkhangelskaja, I. V. ...
Physics of atomic nuclei,
08/2023, Volume:
86, Issue:
4
Journal Article
Peer reviewed
The GAMMA-400 gamma-ray telescope is the successor of Soviet and Russian gamma-ray telescopes. GAMMA-400 is being developed for cosmophysical research in accordance with the Russian Federal Space ...Program 2016–2025. The GAMMA-400 experiment will be implemented aboard the Russian astrophysical space observatory in a highly elliptic orbit during 7 years to provide new data on gamma-ray emission mainly from the Galactic plane, Galactic Center, the Sun and cosmic-ray electron
positron fluxes. The main mode of observations will be the continuous point-source mode with the duration of up to
100 days. The GAMMA-400 gamma-ray telescope will study high-energy gamma-ray emission up to several TeV and cosmic-ray electrons
positrons up to 20 TeV. GAMMA-400 will have the never-achieved angular resolution, the high-energy and time resolutions, as well as very good separation efficiency of gamma rays from cosmic-ray background and of electrons
positrons from protons. The distinctive features of GAMMA-400 are the excellent angular resolution of
at
GeV that exceeds resolutions of the space-based and ground-based gamma-ray telescopes by a factor of 5–10, as well as high-energy resolution of
at
GeV. GAMMA-400 studies can discover gamma-ray emission from annihilation or decay of dark matter particles, identify many unassociated discrete sources, explore the structure of extended sources, search for gamma-ray bursts and solar gamma-ray flares, improve the data on cosmic-ray electron
positron spectra for energies of >50 GeV.
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