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A catalog of spectroscopic binary candidate stars derived from a comparison of Gaia DR2 with other radial velocity catalogs

Jack, Dennis

Using the recently published Gaia second data release that includes measurements of the mean radial velocity of about 7.2 million stars, we performed a systematic comparison with other existing radial velocity catalogs to search for variations in the radial velocity measurements, with the goal that detected differences may indicate that these star…

Unification of strongly magnetized neutron stars with regard to X‑ray emission from hot spots

Hayashida, K.; Nakajima, H.; Matsumoto, H. +1 more

Strongly magnetized isolated neutron stars (NSs) are categorized into two families according, mainly, to their magnetic field strength. The one with a higher magnetic field of 1014–1015 Gauss is called "magnetar," and the other is the X‑ray isolated neutron star (XINS) with 1013 Gauss. Both magnetars and XINSs show thermal emission in X‑rays, whos…

Variability in high‑mass X‑ray binaries

Wilms, J.; Pottschmidt, K.; Grinberg, V. +5 more

Strongly magnetized, accreting neutron stars show periodic and aperiodic variability over a wide range of time scales. By obtaining spectral and timing information on these different time scales, we can have a closer look into the physics of accretion close to the neutron star and the properties of the accreted material. One of the most prominent …

Constraints on the number of X‑ray pulsars in IC 10 from a deep XMM‑Newton observation

Wik, D. R.; Yang, J.; Laycock, S. G. T.

We report the most sensitive search yet for X‑ray pulsars in the dwarf starburst galaxy IC 10, which is known to contain a population of young, high‑mass X‑ray binaries. We searched for pulsations in 207 point‑like X‑ray sources in the direction of IC 10 by a 2012 XMM‑Newton observation with a total exposure time of 134.5 ks. Pulsation searches in…

Simultaneous Kepler/K2 and XMM‑Newton observations of superflares in the Pleiades

Antoniou, V.; Micela, G.; Stauffer, J. +9 more

Together with coronal mass ejection, flares are the most energetic stellar magnetic events, ignited by a sudden release of magnetic energy, which triggers a cascade of interconnected phenomena, each resulting in emission in different bands. For this reason, flares are intrinsic multiwavelength phenomena. In particular, optical and soft X‑ray emiss…

Automatic detection of tidal disruption events and other long‑duration transients in XMM‑Newton data

Webb, N. A.

XMM‑Newton's large field of view and excellent sensitivity have resulted in hundreds of thousands of serendipitous X‑ray detections. While their spectra have been widely exploited, their variable nature has been little studied. Part of this is due to the way XMM‑Newton currently operates, where observations generally have a 12‑month proprietary pe…

η Carinae: Particle acceleration and multimessenger aspects

Walter, R.; Balbo, M.

η Carinae is composed of two very massive stars orbiting each other in 5.5 years. The primary star features the densest known stellar wind, colliding with that expelled by its companion. The wind collision region dissipates energy and accelerates particles up to relativistic energies, producing nonthermal X‑ray and γ‑ray emission detected by Beppo…

Energy‑dependent timing studies of the low‑hard state of black hole X‑ray binaries with XMM‑Newton

Kong, Albert K. H.; Stiele, Holger

Almost all low‑mass black hole X‑ray binaries are transient sources. Most of these sources show a hysteresis: they evolve from the low‑hard state through intermediate state(s) into the high‑soft state and then return to the hard state at lower luminosity, again passing through the intermediate states. However, there are outbursts that remain in th…

Analytical Resolution of the Dark Night Sky (Olbers') Paradox

Harari, Zaki

We derive a spatiotemporal analytical resolution of the dark night sky, or Olbers' paradox, first showing that in an infinitely large universe the cumulative solid angle of the light that is projected upon the celestial sphere by an infinite population of directly observable stars is indeed finite. Using the GAIA DR2 data, we show that the number …

Editor's note

Schartel, Norbert