High Energy Astrophysical Phenomena (astro-ph.HE)
Wed, 23 Aug 2023
1.Polarization Signature of Companion-Fed Supernovae Arising from BH-NS/BH Progenitor Systems
Authors:Xudong Wen, He Gao, Shunke Ai, liangduan liu, Jin-Ping Zhu, Wei-Hua Lei
Abstract: The formation of black hole-neutron star (BH-NS) or BH-BH systems may be accompanied with special supernova (SN) signals, due to the accretion feedback from the companion BH. The additional heating, which is mainly attributed to the Blandford-Payne mechanism, would disrupt the isotropic nature of the luminosity distribution on the surface of the SN ejecta, leading to the appearance of polarization. Here we develop a three dimensional (3D) Monte Carlo polarization simulation code (MCPSC) to conduct simulations for these special SNe. We find that the maximum polarization level of approximately \sim 2 occurs at the peak time of SN emission in the "close-binary" scenario, while in the "faraway-binary" case, maximum polarization (i.e. \sim 0.7) is observed at a considerably later time than the peak of the SN. The magnitude of polarization is dependent on the degree of unevenness in the luminosity distribution and the angle between the line of sight and the equatorial direction. When considering the geometric distortion of supernova ejecta at the same time, the magnitude of polarization may either increase (for a oblate ellipsoidal shape) or decrease (for a prolate ellipsoidal shape). The polarization signatures represent a promising auxiliary instrument to facilitate the identification of the companion-fed SNe. Moreover, by comparing the event rate of these special SNe with the event rate density of LIGO-Virgo detected BH-NS/BH systems could further help to distinguish the BH-NS/BH formation channel.
2.Detecting ultra-high-energy cosmic rays with prototypes of the Fluorescence detector Array of Single-pixel Telescopes (FAST) in both hemispheres
Authors:Shunsuke Sakurai The FAST Collaboration, Justin Albury The FAST Collaboration, Jose Bellido The FAST Collaboration, Fraser Bradfield The FAST Collaboration, Ladislav Chytka The FAST Collaboration, John Farmer The FAST Collaboration, Toshihiro Fujii The FAST Collaboration, Petr Hamal The FAST Collaboration, Pavel Horvath The FAST Collaboration, Miroslav Hrabovsky The FAST Collaboration, Vlastimil Jilek The FAST Collaboration, Jakub Kmec The FAST Collaboration, Jiri Kvita The FAST Collaboration, Max Malacari The FAST Collaboration, Dusan Mandat The FAST Collaboration, Massimo Mastrodicasa The FAST Collaboration, John N. Matthews The FAST Collaboration, Stanislav Michal The FAST Collaboration, Hiromu Nagasawa The FAST Collaboration, Hiroki Namba The FAST Collaboration, Libor Nozka The FAST Collaboration, Miroslav Palatka The FAST Collaboration, Miroslav Pech The FAST Collaboration, Paolo Privitera The FAST Collaboration, Francesco Salamida The FAST Collaboration, Petr Schovanek The FAST Collaboration, Radomir Smida The FAST Collaboration, Daniel Stanik The FAST Collaboration, Zuzana Svozilikova The FAST Collaboration, Akimichi Taketa The FAST Collaboration, Kenta Terauch The FAST Collaboration, Stan B. Thomas The FAST Collaboration, Petr Travnicek The FAST Collaboration, Martin Vacula The FAST Collaboration
Abstract: Ultra-high energy cosmic rays (UHECRs), whose energy are beyond $10^{18}~\mathrm{eV}$, are the most energetic particles we have ever detected. The latest results seem to indicate a heavier composition at the highest energies, complicating the search for their origins. Due to the limited number of UHECR events, we need to build an instrument with an order of magnitude larger effective-exposure to collect UHECRs in future decades. The Fluorescence detector Array of Single-pixel Telescopes (FAST) is a proposed low-cost, easily deployable UHECR detector suitable for a future ground array. It is essential to validate the telescope design and autonomous observational techniques using prototypes located in both hemispheres. Here we report on the current status of observations, recent performance results of prototypes, and developments towards a future mini-array.
3.Prospects of detecting gamma-ray signal of dark matter interaction with the MACE telescope
Authors:M. Khurana, A. Pathania, K. K. Singh, C. Borwankar, P. K. Netrakanti, K. K. Yadav
Abstract: The MACE (Major Atmospheric Cherenkov Experiment) telescope has started its regular gamma-ray observations at Hanle in India. Located at an altitude of $\sim$ 4.3 km above sea level and equipped with a 21 m diameter large quasi-parabolic reflector, it has the capability to explore the gamma-ray sky in the energy range above 20 GeV with very high sensitivity. In this work, we present the results from the feasibility studies for searching high-energy gamma-ray signals from dark matter interaction in potential astrophysical environments. We study the impact of MACE response function and other instrumental characteristics to probe the velocity average interaction cross-section ($<\sigma v>$) of the weakly interacting massive particles (WIMPs), expected from the thermal dark matter freeze-out during the decoupling era. We consider the presence of dark matter in the form of pure WIMPs in the mass range 200 GeV - 10 TeV to produce distinctive gamma-ray spectra through its self-annihilation into standard model particles using the Pythia simulation package. The convolution of gamma-ray spectra corresponding to different standard model channels with the MACE response function is used to estimate the upper limit on $<\sigma v>$ for 100 hours of expected MACE observation of Segue1 (a dwarf spheroidal galaxy) which is a potential site of dark matter.
4.Dense Forests of Microshots in Bursts from FRB 20220912A
Authors:Danté M. Hewitt, Jason W. T. Hessels, Omar S. Ould-Boukattine, Pragya Chawla, Ismaël Cognard, Akshatha Gopinath, Lucas Guillemot, Daniela Huppenkothen, Kenzie Nimmo6, Mark P. Snelders
Abstract: We report on exceptionally bright bursts (>400 Jy ms) detected from the repeating fast radio burst source FRB 20220912A using the Nan\c{c}ay Radio Telescope (NRT), as part of the ECLAT (Extragalactic Coherent Light from Astrophysical Transients) monitoring campaign. These bursts exhibit extremely luminous, broadband, short-duration structures (~ 16 microseconds), which we term 'microshots' and which can be especially well studied in the NRT data given the excellent signal-to-noise and dynamic range (32-bit samples). The estimated peak flux density of the brightest microshot is 450 Jy. We show that the microshots are clustered into dense 'forests', by modelling them as Weibull distributions and obtaining Weibull shape parameters of approximately 0.5. Our polarimetric analysis reveals that the bursts are nearly 100% linearly polarised; have < 10% circular polarisation fractions; a near-zero average rotation measure of 0.10(6) rad/m^2; and varying polarisation position angles over the burst duration. For one of the bursts, we analyse raw voltage data from simultaneous observations with the Westerbork RT-1 single 25-m dish. These data allow us to measure the scintillation bandwidth, 0.30(3) MHz, and to probe the bursts on (sub-)microsecond timescales. Some important nuances related to dedispersion are also discussed. We propose that the emission mechanism for the broadband microshots is potentially different from the emission mechanism of the broader burst components which still show a residual drift of a few hundred MHz/ms after correcting for dispersion using the microshots. We discuss how the observed emission is phenomenologically analogous to different types of radio bursts from the Sun.
5.Progress Towards a Diffuse Neutrino Search in the Full Livetime of the Askaryan Radio Array
Authors:Paramita Dasgupta for the ARA Collaboration, Marco Stein Muzio for the ARA Collaboration
Abstract: The Askaryan Radio Array (ARA) is an in-ice ultrahigh energy (UHE, $>10$ PeV) neutrino experiment at the South Pole that aims to detect radio emissions from neutrino-induced particle cascades. ARA has five independent stations which together have collected nearly 24 station-years of data. Each of these stations search for UHE neutrinos by burying in-ice clusters of antennas $\sim 200$ m deep in a roughly cubical lattice with side length $\sim 15$ m. Additionally, the fifth ARA station (A5) has a beamforming trigger, referred to as the Phased Array (PA), consisting of a trigger array of 7 tightly packed vertically-polarized antennas. In this proceeding, we will present a neutrino search with the data of this "hybrid" station, emphasizing its capabilities for improved analysis efficiencies, background rejection, and neutrino vertex reconstruction. This is enabled by combining the closely packed trigger antennas with the long-baselines of the outrigger antennas. We will also place the A5 analysis into the context of the broader five station analysis program, including efforts to characterize and calibrate the detector, model and constrain backgrounds, and reject noise across the entire array. We anticipate this full neutrino search to set world-leading limits above 100 PeV, and inform the next generation of neutrino detection experiments.
6.$γ$-ray detection from occasional flares in T Tauri stars of NGC 2071. I. Observational connection
Authors:A. Filócomo, J. F. Albacete Colombo, E. Mestre, L. J. Pellizza, J. A. Combi
Abstract: NGC 2071 is a star-forming region that overlaps with three $\gamma$-ray sources detected by the Fermi Space Telescope. We propose that strong flare activity in T Tauri stars could produce $\gamma$-ray emission in a way that makes them a counterpart to some unidentified sources detected by the Large Area Telescope aboard the Fermi satellite. We have performed a spectral and temporal analysis for two Fermi data sets: the first 2 yr and the entire 14 yr of observations. We have found that the $\gamma$-ray source is detectable at 3.2$\sigma$ above the background at energies above 100 GeV during the first 2 yr of observation. The analysis of the expected frequency of the highest energy flares occurring in T Tauri stars is consistent with our estimate. In addition, we have determined the minimum energy of the flare that would produce $\gamma$-ray emission, which is $\sim 5 \times 10^{37}$ erg. This agreement becomes a hard observational constraint supporting previous hypotheses about rare flares as the origin of unidentified $\gamma$-ray sources in star-forming regions.
7.VERITAS observations of the Be/X-ray binary system LS V +44 17 during a major outburst
Authors:Jamie Holder for the VERITAS Collaboration
Abstract: The Be/X-ray binary system LS V +44 17 (RX J0440.9+4431) is a potential member of the rare class of gamma-ray binaries. The system is comprised of a Be star and a neutron star companion with an orbital period of 150 days. In December of 2022, MAXI detected an X-ray outburst from the source, which peaked in early January before declining and then re-brightening. During the second peak, the flux exceeded 1 Crab in the 15-50 keV range, and exhibited a pulsed emission component with a pulse period of 208 seconds. VERITAS observations were conducted close to the peak of the second outburst, from January 24 to January 27, 2023. We report here on the search for very high energy (VHE) gamma-ray emission in these data.