Abstracts of Interest
Selected by:
Fedor Tairli
Abstract: 2305.16003
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Title:Solution To The Cosmic Rays Puzzle ?
Download PDFAbstract: Recent observations provide compelling evidence that the bulk of the high energy cosmic rays (CRs) and gamma-ray bursts (GRBs) are co-produced by highly relativistic jets of plasmoids of stellar matter. These jets are launched by fall back matter on newly born neutron stars and stellar black holes in core collapse of stripped envelope massive stars with or without an associated supernova. The electrons in the plasmoids produce GRB pulses mainly by inverse Compton scattering of photons on their path, while magnetic reflection of the charged particles produces the high energy cosmic rays.
Abstract: 2305.15185
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Title:Recent results from continuous gravitational wave searches using data from LIGO/Virgo/KAGRA's third observing run
Download PDFAbstract: The third observing run of advanced LIGO, Virgo and KAGRA brought unprecedented sensitivity towards a variety of quasi-monochromatic, persistent gravitational-wave signals. Continuous waves allow us to probe not just the existence of canonical asymmetrically rotating neutron stars, but also different forms of dark matter, thus showing the wide-ranging astrophysical implications of using a relatively simple signal model. I will describe the major results from the numerous continuous-wave searches that were performed in O3, both inside and outside the LIGO/Virgo/KAGRA collaborations, and show how impactful to multi-messenger physics that they have been.
Abstract: 2305.15185
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Full Text: [ PostScript, PDF]
Title:Recent results from continuous gravitational wave searches using data from LIGO/Virgo/KAGRA's third observing run
Download PDFAbstract: The third observing run of advanced LIGO, Virgo and KAGRA brought unprecedented sensitivity towards a variety of quasi-monochromatic, persistent gravitational-wave signals. Continuous waves allow us to probe not just the existence of canonical asymmetrically rotating neutron stars, but also different forms of dark matter, thus showing the wide-ranging astrophysical implications of using a relatively simple signal model. I will describe the major results from the numerous continuous-wave searches that were performed in O3, both inside and outside the LIGO/Virgo/KAGRA collaborations, and show how impactful to multi-messenger physics that they have been.
Abstract: 2305.18538
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Title:Accretion onto a Supermassive Black Hole Binary Before Merger
Download PDFAbstract: While supermassive binary black holes (SMBBHs) inspiral toward merger they may also accrete significant amounts of matter. To study the dynamics of such a system requires simultaneously describing the evolving spacetime and the dynamics of magnetized plasma. Here we present the first relativistic calculation simulating two equal-mass, non-spinning black holes as they inspiral from an initial separation of $20M$ ($G=c=1$) almost to merger, $\simeq 9M$, while accreting gas from a surrounding disk, where $M$ is the total binary mass. We find that the accretion rate $\dot M$ onto the black holes first decreases during this period and then reaches a plateau, dropping by only a factor of $\sim 3$ despite its rapid inspiral. An estimated bolometric light curve follows the same profile. The minidisks through which the accretion reaches the black holes are very non-standard. Reynolds, not Maxwell, stresses dominate, and they oscillate between two distinct structural states. In one part of the cycle, ``sloshing" streams transfer mass from one minidisk to the other through the L1 point at a rate $\sim 0.1\times$ the accretion rate, carrying kinetic energy at a rate that can be as large as the peak minidisk bolometric luminosity. We also discover that the minidisks have time-varying tilts with respect to the orbital plane similar in magnitude to the circumbinary disk's aspect ratio. The unsigned poloidal flux on the black hole event horizon is roughly constant at a dimensionless level $\phi\sim 2-3$, but doubles just before merger; if the black holes had significant spin, this flux could support jets whose power could approach the radiated luminosity. This simulation is the first to employ our multipatch infrastructure \pwmhd, decreasing computational expense per physical time to $\sim 3\%$ of similar runs using conventional single-grid methods.
Abstract: 2305.18628
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Title:Simultaneous and panchromatic observations of the Fast Radio Burst FRB 20180916B
Download PDFAbstract: Aims. Fast Radio Bursts are bright radio transients whose origin has not yet explained. The search for a multi-wavelength counterpart of those events can put a tight constrain on the emission mechanism and the progenitor source. Methods. We conducted a multi-wavelength observational campaign on FRB 20180916B between October 2020 and August 2021 during eight activity cycles of the source. Observations were led in the radio band by the SRT both at 336 MHz and 1547 MHz and the uGMRT at 400 MHz. Simultaneous observations have been conducted by the optical telescopes Asiago (Galileo and Copernico), CMO SAI MSU, CAHA 2.2m, RTT-150 and TNG, and X/Gamma-ray detectors on board the AGILE, Insight-HXMT, INTEGRAL and Swift satellites. Results. We present the detection of 14 new bursts detected with the SRT at 336 MHz and seven new bursts with the uGMRT from this source. We provide the deepest prompt upper limits in the optical band fro FRB 20180916B to date. In fact, the TNG/SiFAP2 observation simultaneous to a burst detection by uGMRT gives an upper limit E_optical / E_radio < 1.3 x 10^2. Another burst detected by the SRT at 336 MHz was also co-observed by Insight-HMXT. The non-detection in the X-rays yields an upper limit (1-30 keV band) of E_X-ray / E_radio in the range of (0.9-1.3) x 10^7, depending on which model is considered for the X-ray emission.
Abstract: 2305.14399
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Title:Type Ia Supernovae Induced by Primordial Black Holes from Dark First-Order Phase Transition
Download PDFAbstract: A primordial black hole (PBH) with mass $10^{-15}\leq M_{\rm PBH}/M_{\odot}\leq 10^{-10}$ is currently beyond the sensitivity of both microlensing and black hole (BH) evaporation methods. A novel scenario has been proposed: When a PBH with mass $10^{-14}\leq M_{\rm PBH}/M_{\odot}\leq 10^{-11}$ transits through a white dwarf (WD) made up of carbon and oxygen, Bondi-Hoyle-Lyttleton (BHL) accretion in a reactive medium creates a shock wave, which generates direct detonation ignition in the WD core and then leads to thermonuclear supernovae (SNe Ia). The aim of this study is to impose constraints on the PBH to dark matter (DM) abundance fraction, $f_{\rm PBH}$, via comparing the SN Ia event rates between PBH hypotheses and observational data. For PBH fraction less than unity, we found the observed event rate prefers PBH mass region, $7.6\times 10^{-13}\leq M_{\rm PBH}/M_{\odot}\leq 6.1\times 10^{-12}$, under the Navarro-Frenk-White (NFW) profile. Meanwhile, the aforementioned PBH mass and abundance can be efficiently produced via a cosmological first-order phase transition (FOPT) in dark sector which associates with $\mathcal{O}({\rm MeV})$ energy scale and thus gives rise to complementary signals of stochastic gravitational waves (GWs) from $10^{-6}$ Hz to $10^{-5}$ Hz peak frequency which can be probed by future $\mu$Ares GW interferometer.
Abstract: 2305.16278
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Title:Power spectrum in the cave
Download PDFAbstract: Forthcoming galaxy surveys will provide measurements of galaxy clustering with an unprecedented level of precision, that will require comparably good accuracy. Current models for galaxy correlations rely on approximations and idealizations that might be inadequate for ultra precise measurements. On the other hand, exact calculations have proven to be computationally too expensive to be efficiently implemented in real data analyses. We start a project to provide precise and accurate formalisms for galaxy correlations, and in this paper we investigate the 3D angular power spectrum including effects of unequal time correlations. We establish an explicit link between the full- and flat-sky spectra by performing an asymptotic expansion of the full-sky result around the equal time case. The limiting case coincides with the idealized spectrum that a meta-observer would measure if it had access to the entire 4D Universe. The leading term in the obtained flat-sky expansion is the only translationally invariant term in the plane perpendicular to the line of sight, while the higher-order terms account for the deviation from this invariance. We study the behavior of such corrections for a simplified universe where we can analytically solve the power spectrum and have full control of the equations, therefore being able to understand the exact nature of all the terms and the origin of the corrections. We highlight that the conclusions and the structure of the unequal time spectra are fully general and serve as lessons and guidance in understanding galaxy clustering in any cosmology. Finally, we show that our flat-sky unequal time expression matches the exact full-sky calculation remarkably better than commonly adopted approximations, even at the largest scales and for both shallow and deep redshift bins.
Abstract: 2305.16514
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Title:New Measurement of Muon Neutrino Disappearance from the IceCube Experiment
Download PDFAbstract: The IceCube Neutrino Observatory is a Cherenkov detector located at the South Pole. Its main component consists of an in-ice array of optical modules instrumenting one cubic kilometer of deep Glacial ice. The DeepCore sub-detector is a denser in-fill array with a lower energy threshold, allowing us to study atmospheric neutrinos oscillations with energy below 100 GeV arriving through the Earth. We present preliminary results of an atmospheric muon neutrino disappearance analysis using data from 2012 to 2021 and employing convolutional neural networks (CNNs) for precise and fast event reconstructions.
Abstract: 2305.16693
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Title:Constraining models for the origin of ultra-high-energy cosmic rays with a novel combined analysis of arrival directions, spectrum, and composition data measured at the Pierre Auger Observatory
Download PDFAbstract: The combined fit of the measured energy spectrum and shower maximum depth distributions of ultra-high-energy cosmic rays is known to constrain the parameters of astrophysical models with homogeneous source distributions. Studies of the distribution of the cosmic-ray arrival directions show a better agreement with models in which a fraction of the flux is non-isotropic and associated with the nearby radio galaxy Centaurus A or with catalogs such as that of starburst galaxies. Here, we present a novel combination of both analyses by a simultaneous fit of arrival directions, energy spectrum, and composition data measured at the Pierre Auger Observatory.
We find that a model containing a flux contribution from the starburst galaxy catalog of around 20% at 40 EeV with a magnetic field blurring of around $20^\circ$ for a rigidity of 10 EV provides a fair simultaneous description of all three observables. The starburst galaxy model is favored with a significance of $4.5\sigma$ (considering experimental systematic effects) compared to a reference model with only homogeneously distributed background sources. By investigating a scenario with Centaurus A as a single source in combination with the homogeneous background, we confirm that this region of the sky provides the dominant contribution to the observed anisotropy signal. Models containing a catalog of jetted active galactic nuclei whose flux scales with the $\gamma$-ray emission are, however, disfavored as they cannot adequately describe the measured arrival directions.
Abstract: 2305.16887
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Title:Awesome SOSS: Atmospheric Characterisation of WASP-96 b using the JWST Early Release Observations
Download PDFAbstract: The newly operational JWST offers the potential to study the atmospheres of distant worlds with precision that has not been achieved before. One of the first exoplanets observed by JWST in the summer of 2022 was WASP-96 b, a hot-Saturn orbiting a G8 star. As part of the Early Release Observations program, one transit of WASP-96 b was observed with NIRISS/SOSS to capture its transmission spectrum from 0.6-2.85 microns. In this work, we utilise four retrieval frameworks to report precise and robust measurements of WASP-96 b's atmospheric composition. We constrain the logarithmic volume mixing ratios of multiple chemical species in its atmosphere, including: H$_2$O = $-3.59 ^{+ 0.35 }_{- 0.35 }$, CO$_2$ = $-4.38 ^{+ 0.47 }_{- 0.57 }$ and K = $-8.04 ^{+ 1.22 }_{- 1.71 }$. Notably, our results offer a first abundance constraint on potassium in WASP-96 b's atmosphere, and important inferences on carbon-bearing species such as CO$_2$ and CO. Our short wavelength NIRISS/SOSS data are best explained by the presence of an enhanced Rayleigh scattering slope, despite previous inferences of a clear atmosphere - although we find no evidence for a grey cloud deck. Finally, we explore the data resolution required to appropriately interpret observations using NIRISS/SOSS. We find that our inferences are robust against different binning schemes. That is, from low $R = 125$ to the native resolution of the instrument, the bulk atmospheric properties of the planet are consistent. Our systematic analysis of these exquisite observations demonstrates the power of NIRISS/SOSS to detect and constrain multiple molecular and atomic species in the atmospheres of hot giant planets.
Abstract: 2305.17086
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Title:Sun is a cosmic ray TeVatron
Download PDFAbstract: Very recently, HAWC observatory discovered the high-energy gamma ray emission from the solar disk during the quiescent stage of the sun, extending the Fermi-LAT detection of intense, hard emission between 0.1 - 200 GeV to TeV energies. The flux of these observed gamma-rays is significantly higher than that theoretically expected from hadronic interactions of galactic cosmic rays with the solar atmosphere. More importantly, spectral slope of Fermi and HAWC observed gamma ray energy spectra differ significantly from that of galactic cosmic rays casting doubt on the prevailing galactic cosmic ray ancestry model of solar disk gamma rays. In this letter, we argue that the quiet sun can accelerate cosmic rays to TeV energies with an appropriate flux level in the solar chromosphere, as the solar chromosphere in its quiet state probably possesses the required characteristics to accelerate cosmic rays to TeV energies. Consequently, the mystery of the origin of observed gamma rays from the solar disc can be resolved consistently through the hadronic interaction of these cosmic rays with solar matter above the photosphere in a quiet state. The upcoming IceCube-Gen2 detector should be able to validate the proposed model in future through observation of TeV muon neutrino flux from the solar disk. The proposed idea should have major implications on the origin of galactic cosmic rays.
Abstract: 2305.17243
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Title:The pursuit of the Hubble Constant using Type II Supernovae
Download PDFAbstract: The use of multiple independent methods with their own systematic uncertainties is crucial for resolving the ongoing tension between local and distant measurements of the Hubble constant ($H_{0}$). While type Ia supernovae (SNe Ia) have historically been the most widely used distance indicators, recent studies have shown that type II supernovae (SNe II) can provide independent measurements of extragalactic distances with different systematic uncertainties. Unlike SNe Ia, the progenitors of SNe II are well understood, arising from the explosion of red supergiants in late-type galaxies via core-collapse. While SNe II do not exhibit the same level of uniformity in peak luminosity as SNe Ia, their differences can be calibrated using theoretical or empirical methods. Overall, this chapter presents a comprehensive overview of the use of SNe II as extragalactic distance indicators, with a particular focus on their application to measuring $H_0$ and addressing the Hubble tension. We describe the underlying theory of each method, discuss the challenges associated with them, including uncertainties in the calibration of the supernova absolute magnitude, and present a comprehensive list of the most updated Hubble constant measurements.
Abstract: 2305.18635
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Title:The origin of the terrestrial planets
Download PDFAbstract: Three major planets, Venus, Earth, and Mercury formed out of the solar nebula. A fourth planetesimal, Theia, also formed near Earth where it collided in a giant impact, rebounding as the planet Mars. During this impact Earth lost ${\approx}4$\% of its crust and mantle that is now is found on Mars and the Moon. At the antipode of the giant impact, $\approx$60\% of Earth's crust, atmosphere, and a large amount of mantle were ejected into space forming the Moon. The lost crust never reformed and became the Earth's ocean basins. The Theia impact site corresponds to Indian Ocean gravitational anomaly on Earth and the Hellas basin on Mars. The dynamics of the giant impact are consistent with the rotational rates and axial tilts of both Earth and Mars. The giant impact removed sufficient CO$_2$ from Earth's atmosphere to avoid a runaway greenhouse effect, initiated plate tectonics, and gave life time to form near geothermal vents at the continental margins. Mercury formed near Venus where on a close approach it was slingshot into the Sun's convective zone losing 94\% of its mass, much of which remains there today. Black carbon, from CO$_2$ decomposed by the intense heat, is still found on the surface of Mercury. Arriving at 616 km/s, Mercury dramatically altered the Sun's rotational energy, explaining both its anomalously slow rotation rate and axial tilt. These results are quantitatively supported by mass balances, the current locations of the terrestrial planets, and the orientations of their major orbital axes.
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