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X-ray shapes of elliptical galaxies and implications for self-interacting dark matter
Jeltema, T.; McDaniel, A.; Profumo, S.
Several proposed models for dark matter posit the existence of self-interaction processes that can impact the shape of dark matter halos, making them more spherical than the ellipsoidal halos of collisionless dark matter. One method of probing the halo shapes, and thus the strength of the dark matter self-interaction, is by measuring the shape of …
Using radial velocities to reveal black holes in binaries: A test case
Babusiaux, C.; Dubus, G.; Casares, J. +1 more
Aims: Large radial velocity variations in the LAMOST spectra of giant stars have been used to infer the presence of unseen companions. Some of them have been proposed as possible black hole candidates. We test this selection by investigating the classification of the one candidate that has a known X-ray counterpart (UCAC4 721-037069).
Me…
20 Years of Cluster Observations: The Magnetopause
Hasegawa, H.; Dunlop, M.; Haaland, S. +2 more
The terrestrial magnetopause forms the boundary between the solar wind plasma with its embedded interplanetary magnetic field on one side, and the terrestrial magnetosphere, dominated by Earth's dipole field, on the other side. It is therefore a key region for the transfer of mass, momentum, and energy from the solar wind to the magnetosphere. The…
New members of Cygnus OB2 from Gaia DR2
Orellana, R. B.; De Biasi, M. S.; Paíz, L. G.
Due to the high quality of Gaia DR2 stellar parallaxes and proper motions, we can study the Cygnus OB2 region up to G = 17.5 mag in circular region centred at (l, b) = (79.8°, +0.8°) of radius 1°. We detect four overdensities in the Vector Point Diagram. We apply a parametric model of the proper motion distribution and determine their mean proper …
Shortest Microlensing Event with a Bound Planet: KMT-2016-BLG-2605
Han, Cheongho; Lee, Chung-Uk; Zang, Weicheng +17 more
With a planet-host mass ratio q = 0.012 ± 0.001, KMT-2016-BLG-2605 has the shortest Einstein timescale, tE = 3.41 ± 0.13 days, of any planetary microlensing event to date. This prompts us to examine the full sample of seven short (tE < 7 days) planetary events with good q measurements. We find that six have clustered Einst…
Fragmenting Active Asteroid 331P/Gibbs
Jewitt, David; Li, Jing; Kim, Yoonyoung
We describe active asteroid 331P/Gibbs (2012 F5) using archival Hubble Space Telescope (HST) data taken between 2015 and 2018. 331P is an outer main belt active asteroid with a long-lived debris trail that formed in 2011. Embedded in the debris trail we identify 19 fragments with radii between 0.04 and 0.11 km (albedo 0.05 assumed) containing abou…
Multipoint remote and in situ observations of interplanetary coronal mass ejection structures during 2011 and associated geomagnetic storms
Teriaca, Luca; Srivastava, Nandita; Mishra, Wageesh +1 more
We present multipoint remote and in situ observations of interplanetary coronal mass ejection (ICME) structures during the year 2011. The selected ICMEs arrived at Earth on 2011 March 11 and 2011 August 6, and led to geomagnetic storms. Around the launch of these CMEs from the Sun, the coronagraphs onboard STEREO-Aand-B and SOHO enabled the CMEs t…
New Measurement of the Vertical Atmospheric Density Profile From Occultations of the Crab Nebula With X Ray Astronomy Satellites Suzaku and Hitomi
Katsuda, Satoru; Sato, Kosuke; Tashiro, Makoto S. +6 more
We present new measurements of the vertical density profile of the Earth's atmosphere at altitudes between 70 and 200 km, based on Earth occultations of the Crab Nebula observed with the X ray Imaging Spectrometer onboard Suzaku and the hard X ray Imager onboard Hitomi. X ray spectral variation due to the atmospheric absorption is used to derive t…
Cassini Observation of Relativistic Electron Butterfly Distributions in Saturn's Inner Radiation Belts: Evidence for Acceleration by Local Processes
Krupp, N.; Wei, Y.; Roussos, E. +3 more
The morphology of electron pitch angle distributions (PADs) helps to identify dynamic processes in Saturn's magnetosphere. Previous studies demonstrated convective transport being important for relativistic electron acceleration at L > 4 in the inner magnetosphere, whereas closer to Saturn the situation is not as well established. We have inves…
Clean catalogues of blue horizontal-branch stars using Gaia EDR3
Geier, S.; Pelisoli, I.; Culpan, R.
Context. Blue horizontal-branch stars evolve from low-mass stars that have completed their main-sequence lifetimes and undergone a helium flash at the end of their red-giant phase. As such, blue horizontal-branch stars are very old objects that can be used as markers in studies of the Galactic structure and formation history. To create a clean sky…