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On discrepancy between ATIC and Fermi data: Either ATIC or Fermi-LAT data can be fitted together with the PAMELA data by three components: primary background ~ E^{-3.3}, secondary background ~ E^{-3.6}, and an additional source of electrons ~ E^{-g_a} Exp(-E/E_{cut}). We find that the best fits for ATIC + PAMELA and fo...
astro-ph_HE
The Morphologies and Kinematics of Supernova Remnants: We review the major advances in understanding the morphologies and kinematics of supernova remnants (SNRs). Simulations of SN explosions have improved dramatically over the last few years, and SNRs can be used to test models through comparison of predictions with S...
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Spectral and Timing Properties of IGR J17091-3624 in the Rising Hard State During its 2016 Outburst: We present a spectral and timing study of the NuSTAR and Swift observations of the black hole candidate IGR J17091-3624 in the hard state during its outburst in 2016. Disk reflection is detected in each of the NuSTAR ...
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An unexpected drop in the magnetic field of the X-ray pulsar V0332+53 after the bright outburst occurred in 2015: How the accreted mass settling on the surface of a neutron star affects the topology of the magnetic field and how the secular evolution of the binary system depends on the magnetic field change is still ...
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ASASSN-18ey: The Rise of a New Black-Hole X-ray Binary: We present the discovery of ASASSN-18ey (MAXI J1820+070), a new black hole low-mass X-ray binary discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN). A week after ASAS-SN discovered ASASSN-18ey as an optical transient, it was detected as an X-ray t...
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What are Published X-ray lightcurves telling us about Young Supernova Expansion?: Massive stars lose mass in the form of stellar winds and outbursts. This material accumulates around the star. When the star explodes as a supernova (SN) the resulting shock wave expands within this circumstellar medium. The X-ray emiss...
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Thick accretion disk and Its super Eddington luminosity around spinning blackholes: In the general accretion disk model theory, the accretion disk surrounding an astronomical object comprises fluid rings obeying Keplerian motion. However, we should consider relativistic and rotational effects as we close in toward th...
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Rapid Generation of Kilonova Light Curves Using Conditional Variational Autoencoder: The discovery of the optical counterpart, along with the gravitational waves from GW170817, of the first binary neutron star merger, opened up a new era for multi-messenger astrophysics. Combining the GW data with the optical counter...
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The implications of large binding energies of massive stripped core collapse supernova progenitors on the explosion mechanism: We examine the binding energies of massive stripped-envelope core collapse supernova (SECCSN) progenitors with the stellar evolution code MESA, and find that the jittering jets explosion mech...
astro-ph_HE
Energy Dependent Time Delays of kHz Oscillations due to Thermal Comptonization: We study the energy dependent photon variability from a thermal Comptonizing plasma that is oscillating at kHz frequencies. In particular, we solve the linearised time dependent Kompaneets equation and consider the oscillatory perturbatio...
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How much H and He is "hidden" in SNe Ib/c? -- II. Intermediate-mass objects: a 22 M$_{\odot}$ progenitor case study: Stripped envelope supernovae are a sub-class of core collapse supernovae showing several stages of H/He shell stripping that determines the class: H-free/He-poor SNe are classified as Type Ic, H-poor/H...
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Magnetic Reconnection in Black-Hole Magnetospheres: Lepton Loading into Jets, Superluminal Radio Blobs, and Multi-wavelength Flares: Supermassive black holes in active galactic nuclei launch relativistic jets, as indicated by observed superluminal radio blobs. The energy source of these jets is widely discussed in th...
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Mixing of charged and neutral Bose condensates at nonzero temperature and magnetic field: It is expected that in the interior of compact stars a proton superconductor coexists with and couples to a neutron superfluid. Starting from a field-theoretical model for two complex scalar fields - one of which is electrically...
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Comptonization in 1E 1740.7-2942 spectra from 2 to 200 keV: Studies of the long-term spectral variations have been used to constrain the emission processes of black hole candidates. However, a common scenario which is able to explain the emission from soft to hard X-rays has been proposed only recently. Here, we use XM...
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Forbush Decreases during the DeepMin and MiniMax of Solar Cycle 24: After a prolong and deep solar minimum at the end of solar cycle 23, the current cycle 24 is one of the lowest cycles. The two periods of deep minimum and mini-maximum of the cycle 24 are connected by a period of increasing solar activity. In this work...
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Astrophysical black holes: In this chapter, we introduce the concept of a black hole (BH) and recount the initial theoretical predictions. We then review the possible types of BHs in nature, from primordial, to stellar-mass, to supermassive BHs. Finally, we focus on the latter category and on their intricate relation w...
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Evidence for changes in the radiative efficiency of transient black hole X-ray binaries: We have used pointed RXTE data to examine the long-term X-ray light curves of six transient black hole X-ray binaries during their decay from outburst to quiescence. In most cases there is a period of exponential decay as the sou...
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Search for relativistic fractionally charged particles in space: More than a century after the performance of the oil drop experiment, the possible existence of fractionally charged particles FCP still remains unsettled. The search for FCPs is crucial for some extensions of the Standard Model in particle physics. Most ...
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Gamma-Ray Observations of the Supernova Remnant RX J0852.0-4622 with the Fermi LAT: We report on gamma-ray observations of the supernova remnant (SNR) RX J0852.0-4622 with the Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope. In the Fermi LAT data, we find a spatially extended source at the locat...
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The Gamma-Ray Burst - Supernova Connection: A preponderance of evidence links long-duration, soft-spectrum gamma-ray bursts (GRBs) with the death of massive stars. The observations of the GRB-supernova (SN) connection present the most direct evidence of this physical link. We summarize 30 GRB-SN associations and focus ...
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The Guided Moments formalism: a new efficient full-neutrino treatment for astrophysical simulations: We present the new Guided Moments ($\texttt{GM}$) formalism for neutrino modeling in astrophysical scenarios like core-collapse supernovae and neutron star mergers. The truncated moments approximation ($\texttt{M1}$) ...
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X-ray Measurement of the Spin-Down of Calvera: a Radio- and Gamma-ray-Quiet Pulsar: We measure spin-down of the 59 ms X-ray pulsar Calvera by comparing the XMM-Newton discovery data from 2009 with new Chandra timing observations taken in 2013. Its period derivative is P-dot = (3.19+/-0.08)e-15, which corresponds to s...
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On the Rate of Neutron Star Binary Mergers from Globular Clusters: The first detection of gravitational waves from a neutron star - neutron star (NS-NS) merger, GW170817, and the increasing number of observations of short gamma-ray bursts (SGRBs) have greatly motivated studies of the origins of NS-NS and neutron star -...
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Precursors of Short Gamma-Ray Bursts in the SPI-ACS/INTEGRAL Experiment: We have analyzed the light curves of 519 short gamma-ray bursts (GRBs) detected in the SPI-ACS/INTEGRAL experiment from December 2002 to May 2014 to search for precursors. Both the light curves of 519 individual events and the averaged light curve...
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High-energy gamma-ray observations of Geminga with the Fermi Large Area Telescope: Geminga is the second brightest persistent source in the GeV gamma-ray sky. Discovered in 1975 by SAS-2 mission, it was identified as a pulsar only in the 90s, when ROSAT detected the 237 ms X-ray periodicity, that was later also found...
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Nonthermal X-ray Emission from the N11 Superbubble in the Large Magellanic Cloud: We present the results of X-ray spectral analysis of the superbubble around the OB association LH9 in the H II complex N11 in the Large Magellanic Cloud. Using observations from Suzaku, we have modeled the X-ray emission over the energy...
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On the physical meaning of the 2.1 keV absorption feature in 4U 1538-52: The improvement of the capabilities of nowadays X-ray observatories, like Chandra or XMM-Newton, offers the possibility to detect both absorption and emission lines and to study the nature of the matter surrounding the neutron star in X-ray binari...
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Simple waves in relativistic fluids: We consider the Riemann problem for relativistic flows of polytropic fluids and find relations for the flow characteristics. Evolution of physical quantities take especially simple form for the case of cold magnetized plasmas. We find exact, explicit analytical solutions for one dim...
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Expansion and Age of the Supernova Remnant G350.1-0.3: High-Velocity Iron Ejecta from a Core-Collapse Event: We report Chandra observations of the highly asymmetric core-collapse supernova remnant G350.1-0.3. We document expansion over 9 years away from the roughly stationary central compact object, with sky-plane ve...
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Multiple Peaks and a Long Precursor in the Type IIn Supernova 2021qqp: An Energetic Explosion in a Complex Circumsteller Environment: We present detailed optical photometry and spectroscopy of the Type IIn supernova (SN) 2021qqp. Its unusual light curve is marked by a long gradual brightening (i.e., precursor) for ab...
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Disentangling multiple high-energy emission components in the Vela X pulsar wind nebula with the Fermi Large Area Telescope: Vela X is a pulsar wind nebula in which two relativistic particle populations with distinct spatial and spectral distributions dominate the emission at different wavelengths. An extended $2^\ci...
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Radio-Frequency Searches for Dark Matter in Dwarf Galaxies: Dwarf spheroidal galaxies have long been discussed as optimal targets for indirect dark matter searches. However, the majority of such studies have been conducted with gamma-ray instruments. In this review, we discuss the very recent progress that has been mad...
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Ultra-high energy cosmic ray correlations with Active Galactic Nuclei in the world dataset: Pierre Auger collaboration have recently put forward the hypothesis that the arrival directions of the highest energy cosmic rays correlate with the subset of local active galactic nuclei (AGN). We perform a blind test of AGN ...
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Cosmic ray streaming in the turbulent interstellar medium: We study the streaming instability of GeV$-100~$GeV cosmic rays (CRs) and its damping in the turbulent interstellar medium (ISM). We find that the damping of streaming instability is dominated by ion-neutral collisional damping in weakly ionized molecular cloud...
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Modeling High-energy and Very-high-energy gamma-rays from the Terzan 5 Cluster: The Fermi Large Area Telescope (LAT) has recently detected a population of globular clusters (GCs) in high-energy (HE) gamma-rays. Their spectral properties and energetics are consistent with cumulative emission from a population of milli...
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MeV Pulsars: Modeling Spectra and Polarization: A sub-population of energetic rotation-powered pulsars show high fluxes of pulsed non-thermal hard X-ray emission. While this MeV pulsar population includes some radio-loud pulsars like the Crab, a significant number have no detected radio or GeV emission, a mystery since...
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A re-analysis of the NuSTAR and XMM-Newton broad-band spectrum of Ser~X-1: Context: Ser X-1 is a well studied LMXB which clearly shows a broad iron line. Recently, Miller et al. (2103) have presented broad-band, high quality NuSTAR data of SerX-1.Using relativistically smeared self-consistent reflection models, they ...
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Embedded Spiral Patterns in the Cool Core of the Massive Cluster of Galaxies Abell 1835: We present the properties of intracluster medium (ICM) in the cool core of the massive cluster of galaxies Abell 1835 obtained with the data by $ Chandra$ $X$-$ray$ $Observatory$. We find distinctive spiral patterns with the radi...
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Resolving the puzzle of type IIP SN 2016X: The enigmatic type IIP SN 2016X demonstrates the unprecedented asphericity in the nebular H-alpha line profile, the absence of nebular [O I] emission, and the unusual occultation effect due to the internal dust. The hydrodynamic modelling of the bolometric light curve and expa...
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Simulation study on origin of multi-core events in cosmic rays extensive air showers: Some experiments have found multi-core events in cosmic rays extensive air showers which should be interpreted by hadronic interaction theory. In this paper, the multi-core events are reproduced by Monte Carlo simulation with CORSIK...
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A Proper Motion for the Pulsar Wind Nebula G359.23-0.82, "the Mouse," Associated with the Energetic Radio Pulsar J1747-2958: The "Mouse" (PWN G359.23-0.82) is a spectacular bow shock pulsar wind nebula, powered by the radio pulsar J1747-2958. The pulsar and its nebula are presumed to have a high space velocity, but t...
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Time Evolution of Pulsar Magnetosphere I - An Implicit Approach: We apply a computationally efficient technique to validate the global structure of the pulsar magnetosphere. In this first of a series of studies, a 3D, computationally intensive, implicit Crank-Nicolson finite-difference scheme is developed. The region o...
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Assessing luminosity correlations via cluster analysis: Evidence for dual tracks in the radio/X-ray domain of black hole X-ray binaries: [abridged] The radio:X-ray correlation for hard and quiescent state black hole X-ray binaries is critically investigated in this paper. New observations of known sources, along with...
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Soft gamma-ray constraints on a bright flare from the Galactic Center supermassive black hole: Sagittarius A* (Sgr A*) is the supermassive black hole residing at the center of the Milky Way. It has been the main target of an extensive multiwavelength campaign we carried out in April 2007. Herein, we report the detect...
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Tidal Instability and Superhump by a Wave-Wave Resonant Model: On a disk deformed to a non-axisymmetric form, a set of oscillations can be excited by their resonant interaction through the disk deformation (Kato et al. 2011). This resonant instability process has been proposed to suggest a possible cause of the high-fr...
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Constraints on the source of ultra-high energy cosmic rays using anisotropy vs chemical composition: The joint analysis of anisotropy signals and chemical composition of ultra-high energy cosmic rays offers strong potential for shedding light on the sources of these particles. Following up on an earlier idea, this pa...
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Fragmentation cross-sections and model uncertainties in Cosmic Ray propagation physics: Abundances and energy spectra of cosmic ray nuclei are being measured with high accuracy by the AMS experiment. These observations can provide tight constraints to the propagation models of galactic cosmic rays. In the view of the...
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Diffuse flux of PeV neutrinos from centrifugally accelerated protons in active galactic nuclei: Evidence for high-energy astrophysical PeV neutrinos has been found in the IceCube experiment from an analysis with a 7.5 year (2010 - 2017) data. Active galactic nuclei (AGN) are among the most prominent objects in the un...
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Newtonian analogue of corresponding spacetime dynamics of rotating black holes: Implication on black hole accretion: Based on the conserved Hamiltonian for a test particle, we have formulated a Newtonian analogue of Kerr spacetime in the `low energy limit of the test particle motion' that, in principle, can be compre...
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Potential Gamma-ray Emissions from Low-Mass X-ray Binary Jets: By proposing a pure leptonic radiation model, we study the potential gamma-ray emissions from jets of the low-mass X-ray binaries. In this model, the relativistic electrons that are accelerated in the jets are responsible for radiative outputs. Nevertheless...
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Kinetic modeling of the electromagnetic precursor from an axisymmetric binary pulsar coalescence: The recent detection of gravitational waves associated with a binary neutron star merger revives interest in interacting pulsar magnetospheres. Current models predict that a significant amount of magnetic energy should b...
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The proton-air inelastic cross-section measurement at $\sqrt{s} \approx $ 2 TeV from EAS-TOP experiment: The proton-air inelastic cross section value \sigmapairin=338$\pm$21({\it stat})$\pm$19({\it syst})-28({\it syst}) mb at $\sqrt{s} \approx $ 2 TeV has been measured by the EAS-TOP Extensive Air Shower experiment. ...
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Low X-ray emission challenges supernovae remnants as the source of cosmic-ray electrons: The X-ray synchrotron emission of each of the young supernova-remnants (SNRs) SN1006, Kepler, Tycho, RCW86 and Cas A, is roughly given by $\nu L_{\nu}\sim 10^{45}\rm{erg}/t$, where $t$ is the remnant's age. The electrons emitting...
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Coherent Network Analysis of Gravitational Waves from Three-Dimensional Core-Collapse Supernova Models: Using predictions from three-dimensional (3D) hydrodynamics simulations of core-collapse supernovae (CCSNe), we present a coherent network analysis to detection, reconstruction, and the source localization of the g...
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Why Haven't Many of the Brightest Radio Loud Blazars Been Detected by Fermi ?: We use the complete MOJAVE 1.5 Jy sample of active galactic nuclei (AGN) to examine the gamma-ray detection statistics of the brightest radio-loud blazars in the northern sky. We find that 23% of these AGN were not detected above 0.1 GeV b...
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Optical Observations of the Type Ia Supernova 2011fe in M101 for Nearly 500 Days: We present well-sampled optical observations of the bright Type Ia supernova (SN~Ia) SN 2011fe in M101. Our data, starting from $\sim16$ days before maximum light and extending to $\sim463$ days after maximum, provide an unprecedented t...
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Metallicity Effect on LMXB Formation in Globular Clusters: We present comprehensive observational results of the metallicity effect on the fraction of globular clusters (GC) that contain low-mass X-ray binaries (LMXB), by utilizing all available data obtained with Chandra for LMXBs and HST ACS for GCs. Our primary samp...
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Precision ephemerides for gravitational-wave searches -- III. Revised system parameters of Sco X-1: Neutron stars in low-mass X-ray binaries are considered promising candidate sources of continuous gravitational-waves. These neutron stars are typically rotating many hundreds of times a second. The process of accretio...
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Charged current neutrino interactions in core-collapse supernovae in a virial expansion: Core-collapse supernovae may depend sensitively on charged current neutrino interactions in warm, low density neutron rich matter. A proton in neutron rich matter is more tightly bound than is a neutron. This energy shift \Delta ...
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Search for anisotropic Lorentz invariance violation with γ-rays: While Lorentz invariance, the fundamental symmetry of Einstein's theory of General Relativity, has been tested to a great level of detail, Grand Unified Theories that combine gravity with the other three fundamental forces may result in a violation of Lor...
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Detecting Stellar Lensing of Gravitational Waves with Ground-Based Observatories: We investigate the ability of ground based gravitational wave observatories to detect gravitational wave lensing events caused by stellar mass lenses. We show that LIGO and Virgo possess the sensitivities required to detect lenses with ...
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Effects of Compton Cooling on outflows in a Two Component Accretion Flow around a Black Hole: Results of a Coupled Monte Carlo-TVD Simulation: The effect of cooling on the outflow rate from an accretion disk around a black hole is investigated using a coupled Monte Carlo Total Variation Diminishing code. A correlatio...
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The Definitive X-ray Light Curve of Swift J164449.3+573451: On March 28, 2011, the Swift Burst Alert Telescope triggered on an object that had no analog in over six years of Swift operations. Follow-up observations by the Swift X-ray Telescope (XRT) found a new, bright X-ray source covering 3 orders of magnitude in flu...
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An extended Heitler-Matthews model for the full hadronic cascade in cosmic air showers: The Heitler-Matthews model for hadronic air showers will be extended to all the generations of electromagnetic subshowers in the hadronic cascade. The analysis is outlined in detail for showers initiated by primary protons. For sh...
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Search for gamma-ray emission from four accreting millisecond pulsars with Fermi/LAT: We report our search for \gamma-ray emission in the energy range from 100 MeV to 300 GeV from four Accreting Millisecond Pulsars (AMPs), SAX J1808.4-3658, IGR J00291+5934, XTE J1814-338, and XTE J0929-314. The data are from four-yea...
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Gamma-Ray Observational Properties of TeV-Detected Blazars: The synergy between the Fermi-LAT and ground-based Cherenkov telescope arrays gives us the opportunity for the first time to characterize the high-energy emission from blazars over 5 decades in energy, from 100 MeV to 10 TeV. In this study, we perform a Fermi-...
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GRB 091208B: First Detection of the Optical Polarization in Early Forward Shock Emission of a Gamma-Ray Burst Afterglow: We report that the optical polarization in the afterglow of GRB 091208B is measured at t = 149 - 706 s after the burst trigger, and the polarization degree is P = 10.4% +/- 2.5%. The optical light ...
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The high-energy emission of millisecond pulsars: This chapter provides a phenomenological appraisal of the high-energy emission of millisecond pulsars. We comment on some of their properties as a population, as well as consider the especial cases of transitional pulsars, other redbacks, and black widow systems.
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Constraints on the optical precursor to the naked-eye burst GRB080319B from Pi of the Sky observations: I present the results of the search for an optical precursor to the naked-eye burst - GRB080319B, which reached 5.87m optical peak luminosity in the "Pi of the Sky" data. A burst of such a high brightness could hav...
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X-ray Polarimetry of the accreting pulsar 1A~0535+262 in the supercritical state with PolarLight: The X-ray pulsar 1A 0535+262 exhibited a giant outburst in 2020, offering us a unique opportunity for X-ray polarimetry of an accreting pulsar in the supercritical state. Measurement with PolarLight yielded a non-detecti...
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{\it Suzaku} observation of Galactic supernova remnant CTB 37A (G348.5+0.1): We present here the results of the observation of CTB 37A obtained with the X-ray Imaging Spectrometer onboard the {\it Suzaku} satellite. The X-ray spectrum of CTB 37A is well fitted by two components, a single-temperature ionization equili...
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A flaring magnetar in FRB 121102?: The persistent radio counterpart of FRB 121102 is estimated to have $N\sim 10^{52}$ particles, energy $E_N\sim 10^{48}$ erg, and size $R\sim 10^{17}$ cm. The source can be a nebula inflated and heated by an intermittent outflow from a magnetar --- a neutron star powered by its magneti...
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$JetCurry$ I. Reconstructing Three-Dimensional Jet Geometry from Two-Dimensional Images: We present a three-dimensional (3-D) visualization of jet geometry using numerical methods based on a Markov Chain Monte Carlo (MCMC) and limited memory Broyden-Fletcher-Goldfarb-Shanno (BFGS) optimized algorithm. Our aim is to v...
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Quark matter with strong magnetic field and possibility of the third family of compact stars: We consider the possibility for the existence of the third family of compact objects, considering the effect of strong magnetic fields inside the hybrid stars. As a result, we demonstrate such new sequences of stable equilib...
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Low-frequency gravitational wave memory from gamma-ray burst afterglows with energy injection: Ultrarelativistic gamma-ray burst (GRB) jets are strong gravitational wave (GW) sources with memory-type signals. The plateau (or shallow decay) phases driven by the energy injection might appear in the early X-ray afterglo...
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Multifrequency studies of the narrow-line Seyfert 1 galaxy SBS 0846+513: The narrow-line Seyfert 1 galaxy SBS 0846+513 was first detected by the Large Area Telescope (LAT) on-board Fermi in 2011 June-July when it underwent a period of flaring activity. Since then, as Fermi continues to accumulate data on this source, i...
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Modeling the Spectrum of IGR J17177-3656: The correlation between radio and X-ray luminosity in the hard state of black hole X-ray binaries is important for unveiling the relation between the accretion flow and the jets. In this paper, we have modeled the quasi-simultaneous multi-band observations of a recently discove...
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Observational Signatures of Black Hole Accretion: Rotating vs. Spherical Flows with Tilted Magnetic Fields: We study the observational signatures of magnetically arrested black hole accretion with non-rotating inflow onto a rotating black hole; we consider a range of angles between the black hole spin and the initial...
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The short bursts in SGR 1806-20, 1E 1048-5937 and SGR 0501+4516: We analyzed temporal and spectral properties, focusing on the short bursts, for three anomalous X-ray pulsars (AXPs) and soft gamma repeaters (SGRs), including SGR 1806-20, 1E 1048-5937 and SGR 0501+4516. Using the data from XMM-Newton, we located the sho...
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Disentangling the Origin and Heating Mechanism of Supernova Dust: Late-Time Spitzer Spectroscopy of the Type IIn SN 2005ip: This paper presents late-time near-infrared and {\it Spitzer} mid-infrared photometric and spectroscopic observations of warm dust in the Type IIn SN 2005ip in NGC 2906. The spectra show evidenc...
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Multi-messenger and real-time astrophysics with the Baikal-GVD telescope: The Baikal-GVD deep underwater neutrino experiment participates in the international multi-messenger program on discovering the astrophysical sources of high energy fluxes of cosmic particles, while being at the stage of deployment with a gradual...
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Geodesic models of quasi-periodic-oscillations as probes of quadratic gravity: Future very-large-area X-ray instruments (for which the effective area is larger than $>3$m$^2$) will be able to measure the frequencies of quasi-periodic oscillations~(QPOs) observed in the X-ray flux from accreting compact objects with s...
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The GALEX Time Domain Survey. II. Wavelength-Dependent Variability of Active Galactic Nuclei in the Pan-STARRS1 Medium Deep Survey: We analyze the wavelength-dependent variability of a sample of spectroscopically confirmed active galactic nuclei (AGN) selected from near-UV ($NUV$) variable sources in the GALEX Time D...
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Probing AGN variability with the Cherenkov Telescope Array: Relativistic jets launched by Active Galactic Nuclei are among the most powerful particle accelerators in the Universe. The emission over the entire electromagnetic spectrum of these relativistic jets can be extremely variable with scales of variability from l...
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Influence of a Galactic Gamma-Ray Burst on Ocean Plankton: The hypothesis that one or more biodiversity drops in the Phanerozoic eon, evident in the geological record, might have been caused by the most powerful kind of stellar explosion so far known Gamma Ray Bursts (GRB) has been discussed in several works. These ste...
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First search for atmospheric and extraterrestrial neutrino-induced cascades with the IceCube detector: We report on the first search for atmospheric and for diffuse astrophysical neutrino-induced showers (cascades) in the IceCube detector using 257 days of data collected in the year 2007-2008 with 22 strings active. ...
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Magnetically-driven crustquakes in neutron stars: Crustquake events may be connected with both rapid spin-up `glitches' within the regular slowdown of neutron stars, and high-energy magnetar flares. We argue that magnetic field decay builds up stresses in a neutron star's crust, as the elastic shear force resists the L...
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Understanding the Unusual X-Ray Emission Properties of the Massive, Close Binary WR 20a: A High Energy Window into the Stellar Wind Initiation Region: The problem of explaining the X-ray emission properties of the massive, close binary WR 20a is discussed. Located near the cluster core of Westerlund 2, WR 20a is co...
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GeV observations of the extended pulsar wind nebulae constrain the pulsar interpretations of the cosmic-ray positron excess: It has long been suggested that nearby pulsars within $\sim 1 \,{\rm kpc}$ are the leading candidate of the 10-500 GeV cosmic-ray positron excess measured by PAMELA and other experiments. The r...
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Electron-positron flows around magnetars: The twisted magnetospheres of magnetars must sustain a persistent flow of electron-positron plasma. The flow dynamics is controlled by the radiation field around the hot neutron star. The problem of plasma motion in the self-consistent radiation field is solved using the method...
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A Consistent Modeling of Neutrino-driven Wind with Accretion Flow onto a Protoneutron Star and its Implications for $^{56}$Ni Production: Details of the explosion mechanism of core-collapse supernovae (CCSNe) are not yet fully understood. There is now an increasing number of successful examples of reproducing explosi...
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Ejection of Double knots from the radio core of PKS 1510--089 during the strong gamma-ray flares in 2015: PKS 1510--089 is a bright and active $\gamma$-ray source that showed strong and complex $\gamma$-ray flares in mid-2015 during which the Major Atmospheric Gamma Imaging Cherenkov telescopes detected variable very...
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Multi-messenger searches via IceCube's high-energy neutrinos and gravitational-wave detections of LIGO/Virgo: We summarize initial results for high-energy neutrino counterpart searches coinciding with gravitational-wave events in LIGO/Virgo's GWTC-2 catalog using IceCube's neutrino triggers. We did not find any stati...
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Analysis of a State Changing Supersoft X-ray Source in M31: We report on observations of a luminous supersoft X-ray source (SSS) in M31, r1-25, that has exhibited spectral changes to harder X-ray states. We document these spectral changes. In addition, we show that they have important implications for modeling the sour...
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Primordial Black Holes having Gravitomagnetic Monopole: A primordial black hole (PBH) is thought to be made of the regular matter or ordinary mass ($M$) only, and hence could have already been decayed due to the Hawking radiation if its initial ordinary mass were $\lesssim 5 \times 10^{11}$ kg. Here, we study the role ...
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Discovery and Follow-up of ASASSN-23bd (AT 2023clx): The Lowest Redshift and Least Luminous Tidal Disruption Event To Date: We report the All-Sky Automated Survey for SuperNovae discovery of the tidal disruption event (TDE) ASASSN-23bd (AT 2023clx) in NGC 3799, a LINER galaxy with no evidence of strong AGN activity o...
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Estimating the maximum gravitational mass of nonrotating neutron stars from the GW170817/GRB 170817A/AT2017gfo observation: Assuming that the differential rotation of the massive neutron star (NS) formed in the double NS (DNS) mergers has been effectively terminated by the magnetic braking and a uniform rotation has ...
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The coalescence rates of double black holes: We present the summary of the recent investigations of double black hole binaries in context of their formation and merger rates. In particular we discuss the spectrum of black hole masses, the formation scenarios in the local Universe and the estimates of detection rates fo...
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Patterns in the multi-wavelength behavior of candidate neutrino blazars: Motivated by the identification of the blazar TXS 0506+056 as the first promising high-energy neutrino counterpart candidate, we search for additional neutrino blazars candidates among the Fermi-LAT detected blazars. We investigate the multi-wav...
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Analysis of the duration$-$hardness ratio plane of gamma-ray bursts with skewed distributions: It was recently shown that the $T_{90}-H_{32}$ distributions of gamma-ray bursts from CGRO/BATSE and Fermi/GBM are well described by a mixture of only two skewed components, making the presumed third, intermediate class unn...
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