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Probing the shape of the Milky Way dark matter halo with hypervelocity stars: A new method
Gallo, Arianna; Ostorero, Luisa; Chakrabarty, Sankha Subhra +2 more
We propose a new method for determining the shape of the gravitational potential of the dark matter (DM) halo of the Milky Way (MW) with the galactocentric tangential velocities of a sample of hypervelocity stars (HVSs). We compute the trajectories of different samples of HVSs in a MW where the baryon distribution is axisymmetric and the DM potent…
Relationships Between the Spectra of Near-Earth Proton Enhancements, Hard X-Ray Bursts, and CME Speeds
Grechnev, V. V.; Kiselev, V. I.; Meshalkina, N. S.
Some studies propose the transfer of flare-accelerated protons in an erupting flux rope until its reconnection with an open structure releases the trapped protons. Coulomb collisions in the dense flux-rope body deplete the low-energy part of the proton spectrum. On the other hand, shock acceleration progressively replenishes this part of the spect…
The escape of globular clusters from the satellite dwarf galaxies of the Milky Way
Haghi, Hosein; Zonoozi, Akram Hasani; Khalaj, Pouria +2 more
Using numerical simulations, we have studied the escape of globular clusters (GCs) from the satellite dwarf spheroidal galaxies (dSphs) of the Milky Way (MW). We start by following the orbits of a large sample of GCs around dSphs in the presence of the MW potential field. We then obtain the fraction of GCs leaving their host dSphs within a Hubble …
Luminosity Function and Event Rate Density of XMM-Newton-selected Supernova Shock Breakout Candidates
Liu, Zhu; Yuan, Weimin; Sun, Hui +6 more
A dozen X-ray supernova shock breakout (SN SBO) candidates were reported recently based on XMM-Newton archival data, which increased the X-ray-selected SN SBO sample by an order of magnitude. Assuming that they are genuine SN SBOs, we study the luminosity function (LF) by improving on the method used in our previous work. The light curves and the …
Light from the Darkness: Detecting Ultra-diffuse Galaxies in the Perseus Cluster through Over-densities of Globular Clusters with a Log-Gaussian Cox Process
van Dokkum, Pieter; Romanowsky, Aaron J.; Abraham, Roberto +6 more
We introduce a new method for detecting ultra-diffuse galaxies by searching for over-densities in intergalactic globular cluster populations. Our approach is based on an application of the log-Gaussian Cox process, which is a commonly used model in the spatial statistics literature but rarely used in astronomy. This method is applied to the globul…
The impact of stellar clustering on the observed multiplicity of super-earth systems: outside-in cascade of orbital misalignments initiated by stellar flybys
Rodet, Laetitia; Lai, Dong
A recent study suggests that the observed multiplicity of super-Earth (SE) systems is correlated with stellar overdensities: field stars in high phase-space density environments have an excess of single-planet systems compared to stars in low-density fields. This correlation is puzzling as stellar clustering is expected to influence mostly the out…
A detailed comparison of techniques used to model drift in numerical cosmic ray modulation models
Ferreira, S. E. S.; Engelbrecht, N. Eugene; Mohlolo, S. T.
Drifts have long been known to play a significant role in the transport and modulation of galactic cosmic rays (GCRs), occurring due to gradients in, as well as the curvature of, the heliospheric magnetic field (HMF). GCRs also drift along the wavy current sheet, a structure separating regions of opposite HMF polarity. Furthermore, the influence o…
Improved hydrodynamic pulsation models for the pulsating extreme helium star V652 Herculis
Saio, Hideyuki; Jeffery, C. Simon; Montañés-Rodríguez, Pilar
New non-linear hydrodynamic models have been constructed to simulate the radial pulsations observed in the extreme helium star V652 Her. These use a finer zoning to allow higher radial resolution than in previous simulations. Models incorporate updated OPAL and OP opacity tables and adopt a composition based on the best atmospheric analyses to dat…
Doubling of minute-long quasi-periodic pulsations from super-flares on a low-mass star
Ramsay, Gavin; Irawati, Puji; Dhillon, Vik S. +5 more
Using the ULTRASPEC instrument mounted on the 2.4-m Thai National Telescope, we observed two large flares, each with a total energy close to 1034 erg with sub-second cadence. A combination of a wavelet analysis, a Fourier transform plus an empirical mode decomposition, reveals quasi-periodic pulsations (QPPs) that exhibit an apparent do…
On the nature of the X-ray pulsar XTE J1859+083 and its broad-band properties
Gromadzki, Mariusz; Buckley, David A. H.; Tsygankov, Sergey S. +5 more
This work is devoted to the study of the broad-band 0.8-79 keV spectral and timing properties of the poorly studied X-ray pulsar XTE J1859+083 during its 2015 outburst based on the data from the NuSTAR and Swift observatories. We show that the source pulse profile has complex shape that depends on the energy band. Pulse fraction of XTE J1859+083 h…