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The first view of δ Scuti and γ Doradus stars with the TESS mission
Reese, D. R.; Niemczura, E.; Handberg, R. +63 more
We present the first asteroseismic results for δ Scuti and γ Doradus stars observed in Sectors 1 and 2 of the TESS mission. We utilize the 2-min cadence TESS data for a sample of 117 stars to classify their behaviour regarding variability and place them in the Hertzsprung-Russell diagram using Gaia DR2 data. Included within our sample are the epon…
The Galactic WC and WO stars. The impact of revised distances from Gaia DR2 and their role as massive black hole progenitors
Hamann, W. -R.; Oskinova, L. M.; Sander, A. A. C. +4 more
Wolf-Rayet stars of the carbon sequence (WC stars) are an important cornerstone in the late evolution of massive stars before their core collapse. As core-helium burning, hydrogen-free objects with huge mass-loss, they are likely the last observable stage before collapse and thus promising progenitor candidates for type Ib/c supernovae. Their stro…
Super-efficient Electron Acceleration by an Isolated Magnetic Reconnection
Vaivads, A.; Xu, Y.; Fu, H. S. +1 more
Magnetic reconnection—the process typically lasting for a few seconds in space—is able to accelerate electrons. However, the efficiency of the acceleration during such a short period is still a puzzle. Previous analyses, based on spacecraft measurements in the Earth’s magnetotail, indicate that magnetic reconnection can enhance electron fluxes up …
PHIBSS2: survey design and z = 0.5 - 0.8 results. Molecular gas reservoirs during the winding-down of star formation
Lutz, D.; Wuyts, S.; Förster Schreiber, N. M. +29 more
Following the success of the Plateau de Bure high-z Blue Sequence Survey (PHIBSS), we present the PHIBSS2 legacy program, a survey of the molecular gas properties of star-forming galaxies on and around the star-formation main sequence (MS) at different redshifts using IRAM's NOrthern Extended Millimeter Array (NOEMA). This survey significantly ext…
The Galactic disc in action space as seen by Gaia DR2
Rix, Hans-Walter; Coronado, Johanna; Trick, Wilma H.
The quality and quantity of 6D stellar position-velocity measurements in the second Gaia data release's radial velocity sample (DR2/RVS) allow us to study small-scale structure in the orbit distribution of the Galactic disc beyond the immediate Solar neighbourhood. We investigate the distribution of orbital actions (JR, Lz, J…
The Faint End of the Centaurus A Satellite Luminosity Function
Crnojević, D.; Sand, D. J.; Simon, J. D. +9 more
The Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS) is constructing a wide-field map of the resolved stellar populations in the extended halos of these two nearby, prominent galaxies. We present new Magellan/Megacam imaging of a ∼3 deg2 area around Centaurus A (Cen A), which filled in much of our coverage to its south, leavi…
A magnetar-powered X-ray transient as the aftermath of a binary neutron-star merger
Lehmer, B. D.; Bauer, F. E.; Brandt, W. N. +14 more
Mergers of neutron stars are known to be associated with short γ-ray bursts1-4. If the neutron-star equation of state is sufficiently stiff (that is, the pressure increases sharply as the density increases), at least some such mergers will leave behind a supramassive or even a stable neutron star that spins rapidly with a strong magneti…
Gaia DR2 reveals a star formation burst in the disc 2-3 Gyr ago
Luri, X.; Figueras, F.; Mor, R. +2 more
We use Gaia data release 2 (DR2) magnitudes, colours, and parallaxes for stars with G < 12 to explore a parameter space with 15 dimensions that simultaneously includes the initial mass function (IMF) and a non-parametric star formation history (SFH) for the Galactic disc. This inference is performed by combining the Besançon Galaxy Model fast a…
Gaia DR2 unravels incompleteness of nearby cluster population: new open clusters in the direction of Perseus
Castro-Ginard, A.; Jordi, C.; Cantat-Gaudin, T. +13 more
Context. Open clusters (OCs) are popular tracers of the structure and evolutionary history of the Galactic disc. The OC population is often considered to be complete within 1.8 kpc of the Sun. The recent Gaia Data Release 2 (DR2) allows the latter claim to be challenged.
Aims: We perform a systematic search for new OCs in the direction of Per…
Too big to fail in light of Gaia
Kaplinghat, Manoj; Yu, Hai-Bo; Valli, Mauro
We point out an anticorrelation between the central dark matter (DM) densities of the bright Milky Way dwarf spheroidal galaxies (dSphs) and their orbital pericenter distances inferred from Gaia data. The dSphs that have not come close to the Milky Way centre (like Fornax, Carina and Sextans) are less dense in DM than those that have come closer (…