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The understanding of interstellar nitrogen chemistry has improved significantly with recent results from the Herschel Space Observatory. To set even better constraints, we report here on deep searches for the NH+ ground state rotational…

Positive lags between the arrival time of different photon energies are commonly observed in Gamma-Ray Bursts (GRBs), where soft photons lag behind harder ones. However, some GRBs exhibit the opposite behavior. In particular, Fermi LAT…

高能天体物理现象 · 物理学 2025-05-21 C. Maraventano , G. Ghirlanda , L. Nava , T. Di Salvo , W. Leone , R. Iaria , L. Burderi , A. Tsvetkova

A detection technique for ultra-high energy cosmic rays, complementary to the fluorescence technique, would be the use of the molecular Bremsstrahlung radiation emitted by low-energy ionization electrons left after the passage of the…

天体物理仪器与方法 · 物理学 2016-03-04 I. Al Samarai , C. Berat , O. Deligny , A. Letessier-Selvon , F. Montanet , M. Settimo , P. Stassi

The effective compton cross section in a non-degenerate plasma($n\ll\{\frac{(kT/c)^{2}+2mkT}{h^{2}}\}^{^{3/2}}$) is investigated in a wide range of temperatures. The results show a decreasing behavior with temperature especially for $kT\gg…

天体物理学 · 物理学 2009-11-10 F. Shekh-Momeni , J. Samimi

We have calculated synchrotron spectra of relativistic blast waves, and find predicted characteristic frequencies that are more than an order of magnitude different from previous calculations. For the case of an adiabatically expanding…

天体物理学 · 物理学 2008-11-26 R. A. M. J. Wijers , T. J. Galama

A large fraction of gamma-ray burst (GRB) spectra are very hard below the peak. Indeed, the observed distribution of sub-peak power-law indices, $\alpha$, has been used as an argument for a photospheric origin of GRB spectra. Here, we…

高能天体物理现象 · 物理学 2019-06-12 Zeynep Acuner , Felix Ryde , Hoi-Fung Yu

We present the multi-epoch analysis of 13 variable, nearby (z<0.1), Compton-thin (22<logN_H<24) active galactic nuclei (AGN) selected from the 105-month BAT catalog. Analyzing all available archival soft and hard X-ray observations, we…

高能天体物理现象 · 物理学 2024-03-12 A. Pizzetti , N. Torres-Alba , S. Marchesi , J. Buchner , I. Cox , X. Zhao , S. Neal , D. Sengupta , R. Silver , M. Ajello

Observational studies of GHz peaked spectrum (GPS) sources contribute to the understanding of the radiative properties and interstellar environment of host galaxies. We present the results from the multi-frequency high-resolution VLBI…

高能天体物理现象 · 物理学 2023-03-07 Xiaopeng Cheng , Tao An , Ailing Wang , Sumit Jaiswal

We examine whether the spectral energy distribution of optical continuum emission of active galactic nuclei (AGNs) changes during flux variation, based on accurate and frequent monitoring observations of 11 nearby Seyfert galaxies and QSOs…

The complex optical conductivity of the half-Heusler compound GdPtBi is measured in a frequency range from 20 to 22 000 cm$^{-1}$ (2.5 meV - 2.73 eV) at temperatures down to 10 K in zero magnetic field. We find the real part of the…

介观与纳米尺度物理 · 物理学 2018-10-29 F. Hütt , A. Yaresko , M. B. Schilling , C. Shekhar , C. Felser , M. Dressel , A. V. Pronin

FREGATE, the gamma-ray detector of HETE-2 is entirely dedicated to the study of GRBs. Its main characteristic is its broad energy range, from 7 keV to 400 keV. This energy range can be further extended down to 2 keV using the data from the…

天体物理学 · 物理学 2016-08-30 C. Barraud , the HETE-2 team

We have made radio- and millimeter-wavelength interferometric observations of a variety of molecular absorption lines toward the gravitational lens systems B0218+357 and PKS1830-211. The absorption occurs in the lensing galaxies at…

天体物理学 · 物理学 2007-05-23 Karl M. Menten , Christopher L. Carilli , Mark J. Reid

The high momentum tail (HMT) of nucleons, as a signature of the short-range correlations in nuclei, has been investigated by the high-energy bremsstrahlung $\gamma$ rays produced in $^{86}$Kr + $^{124}$Sn at 25 MeV/u. The energetic photons…

Despite more than fifty years of gamma-ray burst (GRB) observations, several questions regarding the origin of the prompt emission, particularly at high energies, remain unresolved. We present a comprehensive analysis of 35 GRBs observed by…

高能天体物理现象 · 物理学 2025-01-22 Samanta Macera , Biswajit Banerjee , Alessio Mei , Pawan Tiwari , Gor Oganesyan , Marica Branchesi

We report deep Green Bank Telescope (GBT) spectroscopy in the redshifted NH$_3$~(1,1), CS~1-0 and H$_2$CO~0$_{\rm 00}$-1$_{\rm 01}$ lines from the $z \sim 0.685$ absorber towards B0218+357. The inversion (NH$_3$) and rotational (CS,…

宇宙学与河外天体物理 · 物理学 2015-05-27 Nissim Kanekar

We present a case for significantly enhancing the utility and efficiency of the ngEHT by incorporating an additional 86 GHz observing band. In contrast to 230 or 345 GHz, weather conditions at the ngEHT sites are reliably good enough for 86…

One of the scientific goals of the main instrument of GLAST is the study of Gamma-Ray Bursts (GRBs) in the energy range from ~20 MeV to ~300 GeV. In order to extend the energy measurement towards lower energies a secondary instrument, the…

If a gamma ray burst with strong UV emission occurs in a molecular cloud, there will be observable consequences resulting from excitation of the surrounding H2. The UV pulse from the GRB will pump H2 into vibrationally-excited levels which…

天体物理学 · 物理学 2015-06-24 B. T. Draine

We evaluate the broadband afterglow emission of very high redshift gamma-ray bursts (GRBs) using standard relativistic blastwave models with both forward and reverse shock components. For a broad range of parameters, a generic property for…

天体物理学 · 物理学 2008-11-26 Susumu Inoue , Kazuyuki Omukai , Benedetta Ciardi

The paradigm for GRB prompt emission is changing. Since early in the CGRO era, the empirical Band function has been considered a good description of the keV-MeV spectra although its shape is very often inconsistent with the predictions of…

高能天体物理现象 · 物理学 2016-03-16 S. Guiriec , M. M. Gonzalez , J. R. Sacahui , C. Kouveliotou , N. Gehrels , J. McEnery