| 1. |
- Greiner, J., et al.
(författare)
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GRIPS - Gamma-Ray Imaging, Polarimetry and Spectroscopy
- 2012
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Ingår i: Experimental astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 34:2, s. 551-582
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Tidskriftsartikel (refereegranskat)abstract
- We propose to perform a continuously scanning all-sky survey from 200 keV to 80 MeV achieving a sensitivity which is better by a factor of 40 or more compared to the previous missions in this energy range (COMPTEL, INTEGRAL; see Fig. 1). These gamma-ray observations will be complemented by observations in the soft X-ray and (near-)infrared region with the corresponding telescopes placed on a separate satellite. The Gamma-Ray Imaging, Polarimetry and Spectroscopy ("GRIPS") mission with its three instruments Gamma-Ray Monitor (GRM), X-Ray Monitor (XRM) and InfraRed Telescope (IRT) addresses fundamental questions in ESA's Cosmic Vision plan. Among the major themes of the strategic plan, GRIPS has its focus on the evolving, violent Universe, exploring a unique energy window. We propose to investigate γ-ray bursts and blazars, the mechanisms behind supernova explosions, nucleosynthesis and spallation, the enigmatic origin of positrons in our Galaxy, and the nature of radiation processes and particle acceleration in extreme cosmic sources including pulsars and magnetars. The natural energy scale for these non-thermal processes is of the order of MeV. Although they can be partially and indirectly studied using other methods, only the proposed GRIPS measurements will provide direct access to their primary photons. GRIPS will be a driver for the study of transient sources in the era of neutrino and gravitational wave observatories such as IceCUBE and LISA, establishing a new type of diagnostics in relativistic and nuclear astrophysics. This will support extrapolations to investigate star formation, galaxy evolution, and black hole formation at high redshifts.
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| 2. |
- Iyudin, A. F., et al.
(författare)
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GRB redshifts from prompt emission SEDs
- 2007
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Ingår i: Gamma-Ray Bursts. - : American Institute of Physics (AIP). - 0735404135 - 9780735404137 ; , s. 89-98
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Konferensbidrag (refereegranskat)abstract
- Recently the very first detection of γ-ray resonant absorptions along the line of sight toward γ-ray bright quasars (QSOs), like 3C273, 3C279, PKS0528+0134 and BL Lacertae were reported. These detections resulted from the analysis of absorption troughs in SEDs derived on the base of mostly EGRET data that were collected during monitoring campaigns of the Virgo and galactic anticenter regions by the Compton Gamma Ray Observatory (CGRO), as well as during ToO observations of QSOs flares. Among three resonant absorption mechanisms that affect the γ-ray spectrum of point-like sources we point out the Δ-isobar resonance that has a very stable peak-energy of the absorption cross-section for all elements (nuclei), and for individual nucleons. By fitting the SED of γ-ray bright point-sources with a high-energy component, including long duration gamma-ray bursts (GRBs), two absorbers can be detected on the sight lines towards such a γ-ray bright point-source. One of those absorbers is at the GRB rest frame, and, therefore, the value of the GRB redshift can be found by fitting an appropriate trough in the SED. A distinct component of GRBs due to the synchrotron self-Compton (SSC) process is expected to be responsible for the significant GRB emission at GeV and TeV energies. Derishev, Aharonian and Kocharovsky suggested that this GeV-TeV emission is observable over a much broader range of angles relative to the direction of the GRB jet. Such GeV-TeV emission will have much harder spectrum and a much higher cut-off frequency compared to the values derived from the Doppler boosting considerations. These factors boost also our expectations for using GRB prompt emission to derive the redshift of host galaxy. Below we discuss a potential application of the gamma-ray absorption method (GRAM) for derivation of the redshift distribution of the long GRBs having a high-energy component, like GRB910503, GRB930131, GRB930506, GRB941017, and GRB980923. Successful application of this method will dramatically broaden the scope of cosmological studies with the use of GRBs.
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| 3. |
- Iyudin, Anatoli F., et al.
(författare)
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Search for broad absorption lines in spectra of stars in the field of supernova remnant RX J0852.0-4622 (Vela Jr.)
- 2010
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 519:9, s. A86-
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Tidskriftsartikel (refereegranskat)abstract
- Aims. Supernova remnant (SNR) RX J0852.0-4622 is one of the youngest and is most likely the closest among known Galactic SNRs. It was detected in X-rays, the (44)Ti gamma-line, and radio. We obtain and analyze medium-resolution spectra of 14 stars in the direction towards the SNR RX J0852.0-4622 in an attempt to detect broad absorption lines of unshocked ejecta against background stars. Methods. Spectral synthesis is performed for all the stars in the wavelength range of 3740-4020 angstrom to extract the broad absorption lines of Ca II related to the SNR RX J0852.0-4622. Results. We do not detect any broad absorption line and place a 3 sigma upper limit on the relative depths of <0.04 for the broad Ca II absorption produced by the SNR. We detect narrow low and high velocity absorption components of Ca II. High velocity vertical bar V(LSR)vertical bar similar to 100-140 km s(-1) components are attributed to radiative shocks in clouds engulfed by the old Vela SNR. The upper limit to the absorption line strength combined with the width and flux of the (44)Ti gamma-ray line 1.16 MeV lead us to conclude that SNR RX J0852.0-4622 was probably produced by an energetic SN Ic explosion.
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