Abstracts of Interest
Selected by:
Rami Alsulami
Abstract: 1805.01588
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: How does the stellar disk of the Milky Way get its gas?
(Submitted on 4 May 2018)
Abstract: In chemodynamical evolution models it is usually assumed that the Milky Way galaxy forms from the inside-out implying that gas inflows onto the disk decrease with galactocentric distance. Similarly, to reproduce differences between chemical abundances of the thick disk and bulge with respect to those of the thin disk, higher accretion fluxes at early times are postulated. By using a suite of Milky Way-like galaxies extracted from cosmological simulations, we investigate the accretion of gas on the simulated stellar disks during their whole evolution. In general, we find that the picture outlined above holds, although the detailed behavior depends on the assembly history of the Galaxy and the complexities inherent to the physics of galaxy formation.
Abstract: 1805.01481
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: An X-ray guided gravitational-wave search for binary neutron star merger remnants
(Submitted on 3 May 2018)
Abstract: X-ray observations of some short gamma-ray bursts indicate that a long-lived neutron star can form as a remnant of a binary neutron star merger. We develop a gravitational-wave detection pipeline for a long-lived binary neutron star merger remnant guided by these counterpart electromagnetic observations. We determine the distance out to which a gravitational-wave signal can be detected with Advanced LIGO at design sensitivity and the Einstein Telescope using this method, guided by X-ray data from GRB140903A as an example. Such gravitational waves can in principle be detected out to $\sim$ 20 Mpc for Advanced LIGO and $\sim$ 450 Mpc for the Einstein Telescope assuming a fiducial ellipticity of $10^{-2}$. However, in practice we can rule out such high values of the ellipticity as the total energy emitted in gravitational waves would be greater than the total rotational energy budget of the system. We show how these observations can be used to place upper limits on the ellipticity using these energy considerations. For GRB140903A, the upper limit on the ellipticity is $10^{-3}$, which lowers the detectable distance to $\sim$ 2 Mpc and $\sim$ 45 Mpc for Advanced LIGO and the Einstein Telescope, respectively.
Abstract: 1805.00050
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: Diagnosing the Structure of Massive Stars with Galactic Supernova Neutrinos
(Submitted on 30 Apr 2018)
Abstract: It has been suggested that whether a star explodes or not, and what kind of explosion properties it shows, is strongly dependent on the progenitor's core structure. We present the results from 101 axisymmetric core-collapse supernova simulations performed with progenitors spanning initial masses in the range from 10.8 to 75 solar masses, and focus on their connections to the compactness of the progenitor's core. Our simulations confirm a correlation between the neutrinos emitted during the accretion phase and the progenitor's compactness. We suggest that the ratio of observed neutrino events during the first hundreds of milliseconds can be used to infer the progenitor's inner mass density structure.
Abstract: 1804.10847
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: Open Astronomy Catalogs API
(Submitted on 28 Apr 2018)
Abstract: We announce the public release of the application program interface (API) for the Open Astronomy Catalogs (OACs), the OACAPI. The OACs serve near-complete collections of supernova, tidal disruption, kilonova, and fast stars data (including photometry, spectra, radio, and X-ray observations) via a user-friendly web interface that displays the data interactively and offers full data downloads. The OACAPI, by contrast, enables users to specifically download particular pieces of the OAC dataset via a flexible programmatic syntax, either via URL GET requests, or via a module within the astroquery Python package.
Abstract: 1804.10719
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: Direct detection of Ultra-High Energy WIMPs with a satellite detector like JEM-EUSO
(Submitted on 28 Apr 2018)
Abstract: I study the possibility of directly detecting Ultra-high energy (UHE from now on) WIMPs by the WIMPs interaction with the nuclei in the air. Since neutrinos dominate the events from the spherical crown near JEM-EUSO, these signals should be ignored. Then I evaluate the numbers of UHE WIMPs and neutrino detected by JEM-EUSO at different energies (1 PeV < E < 10 EeV) in ten years, respectively. If the energy thresholds are taken to be O($10^7$ GeV), neutrino events can be almost rejected in the detection of UHE WIMPs. According to my evaluation, the numbers of the detected UHE WIMPs can reach a few ten and a few at the energies with O($10^7$ GeV) and 10 EeV in ten years, respectively.
Abstract: 1804.10989
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: Mapping the emission line strengths and kinematics of Supernova Remnant S147 with extensive LAMOST spectroscopic observations
(Submitted on 29 Apr 2018)
Abstract: We present extensive spectroscopic observations of supernova remnant (SNR) S147 collected with the Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST). The spectra were carefully sky-subtracted taking into account the complex filamentary structure of S147. We have utilized all available LAMOST spectra toward S147, including sky and stellar spectra. By measuring the prominent optical emission lines including H{\alpha}, [NII]{\lambda}6584, and [SII]{\lambda}{\lambda}6717,6731, we present maps of radial velocity and line intensity ratio covering the whole nebula of S147 with unprecedented detail. The maps spatially correlated well with the complex filamentary structure of S147. For the central 2 deg of S147, the radial velocity varies from -100 to 100 km/s and peaks between ~ 0 and 10 km/s. The intensity ratios of H{\alpha}/[SII]{\lambda}{\lambda}6717,6731, [SII]{\lambda}6717/{\lambda}6731 and H{\alpha}/[NII]{\lambda}6584 peak at about 0.77, 1.35 and 1.48, respectively, with a scatter of 0.17, 0.19 and 0.37, respectively. The intensity ratios are consistent with the literature values. However, the range of variations of line intensity ratios estimated here and representative of the whole nebula, are larger than previously estimated.
Abstract: 1805.00498
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: PUSHing Core-Collapse Supernovae to Explosions in Spherical Symmetry III: Nucleosynthesis Yields
(Submitted on 1 May 2018)
Abstract: In a previously presented proof-of-principle study, we established a parametrized spherically symmetric explosion method (PUSH) that can reproduce many features of core-collapse supernovae for a wide range of pre-explosion models. The method is based on the neutrino-driven mechanism and follows collapse, bounce and explosion. There are two crucial aspects of our model for nucleosynthesis predictions. First, the mass cut and explosion energy emerge simultaneously from the simulation (determining, for each stellar model, the amount of Fe-group ejecta). Second, the interactions between neutrinos and matter are included consistently (setting the electron fraction of the innermost ejecta). In the present paper, we use the successful explosion models from Ebinger et al. (2018) which include two sets of pre-explosion models at solar metallicity, with combined masses between 10.8 and 120 M$_{\odot}$. We perform systematic nucleosynthesis studies and predict detailed isotopic yields. The resulting $^{56}$Ni ejecta are in overall agreement with observationally derived values from normal core-collapse supernovae. The Fe-group yields are also in agreement with derived abundances for metal-poor star HD84937. We also present a comparison of our results with observational trends in alpha element to iron ratios.
Abstract: 1805.01653
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: A Laminar Model for the Magnetic Field Structure in Bow-Shock Pulsar Wind Nebulae
(Submitted on 4 May 2018)
Abstract: Bow Shock Pulsar Wind Nebulae are a class of non-thermal sources, that form when the wind of a pulsar moving at supersonic speed interacts with the ambient medium, either the ISM or in a few cases the cold ejecta of the parent supernova. These systems have attracted attention in recent years, because they allow us to investigate the properties of the pulsar wind in a different environment from that of canonical Pulsar Wind Nebulae in Supernova Remnants. However, due to the complexity of the interaction, a full-fledged multidimensional analysis is still laking. We present here a simplified approach, based on Lagrangian tracers, to model the magnetic field structure in these systems, and use it to compute the magnetic field geometry, for various configurations in terms of relative orientation of the magnetic axis, pulsar speed and observer direction. Based on our solutions we have computed a set of radio emission maps, including polarization, to investigate the variety of possible appearances, and how the observed emission pattern can be used to constrain the orientation of the system, and the possible presence of turbulence.
Abstract: 1805.00610
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: Continued cooling of the accretion-heated neutron-star crust in the X-ray transient IGR J17480$-$2446 located in the globular cluster Terzan 5
(Submitted on 2 May 2018)
Abstract: We present a new {\it Chandra} observation (performed in July 2016) of the neutron-star X-ray transient IGR J17480$-$2446, located in the globular cluster Terzan 5. We study the further cooling evolution of the neutron-star crust in this system that was heated during the 2010 outburst of the source. This new observation was performed two years after the last observation of IGR J17480$-$2446, hence, significantly extending the cooling baseline. We reanalyzed all available {\it Chandra} observations of the source (but excluding observations during which one of the three known transients in Terzan 5 was in outburst) and fitted the obtained cooling curve with our cooling code {\tt NSCool}, which allows for much improved modelling than what was previously performed for the source. The data and our fit models show that the crust was still cooling $\sim$5.5 years after the end of the outburst. The neutron-star crust has likely not reached thermal equilibrium with the core yet, and further cooling is predicted (which can be confirmed with additional {\it Chandra} observations in $>$5 years time). Intriguingly, the obtained thermal conductivity in the neutron-drip layer in the crust is relatively low compared to what has been inferred for other crust-cooling sources. The reason for this difference is unclear but it might be related to the fact that IGR J17480$-$2446 harbours a relatively slow rotating neutron star (with a spin of 11 Hz) that has a relatively large inferred surface magnetic field strength ($10^{9-10}$ Gauss) compared to what is known or typically assumed for other cooling sources.
Abstract: 1805.01847
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: Observation of Anisotropy of TeV Cosmic Rays with Two Years of HAWC
(Submitted on 4 May 2018 (v1), last revised 7 May 2018 (this version, v2))
Abstract: After two years of operation, the High-Altitude Water Cherenkov (HAWC) Observatory has analyzed the TeV cosmic-ray sky over an energy range between $2.0$ and $72.8$ TeV. The HAWC detector is a ground-based air-shower array located at high altitude in the state of Puebla, Mexico. Using 300 light-tight water tanks, it collects the Cherenkov light from the particles of extensive air showers from primary gamma rays and cosmic rays. This detection method allows for uninterrupted observation of the entire overhead sky (2~sr instantaneous, 8.5~sr integrated) in the energy range from a few TeV to hundreds of TeV. Like other detectors in the northern and southern hemisphere, HAWC observes an energy-dependent anisotropy in the arrival direction distribution of cosmic rays. The observed cosmic-ray anisotropy is dominated by a dipole moment with phase $\alpha\approx40^{\circ}$ and amplitude that slowly rises in relative intensity from $8\times10^{-4}$ at 2 TeV to $14\times10^{-4}$ around 30.3 TeV, above which the dipole decreases in strength. A significant large-scale ($>60^{\circ}$ in angular extent) signal is also observed in the quadrupole and octupole moments, and significant small-scale features are also present, with locations and shapes consistent with previous observations. Compared to previous measurements in this energy range, the HAWC cosmic-ray sky maps improve on the energy resolution and fit precision of the anisotropy. These data can be used in an effort to better constrain local cosmic-ray accelerators and the intervening magnetic fields.
This page created: Tue May 8 10:43:14 ACST 2018 by Rami Alsulami
For a printable title listing click here
For details on generating this page see the instructions. If there are problems with this page (and I expect there will be from time to time) contact Jose.
For previous lists of abstracts of interest click Previous abstracts of interest