Search Publications
Assessing Controls on the Incomplete Draining of Martian Open-Basin Lakes
Goudge, Timothy A.; Fassett, Caleb I.; Bamber, Emily R. +1 more
Over 250 hydrologically open paleolakes, which filled with water before catastrophically breaching, have been identified on Mars. These open-basin lakes are recognized by the topographic geometry of a closed contour below the elevation of the outlet, indicating that the lake was incompletely drained by the breach flood. Here, we explore factors th…
Gaia17bpp: A Giant Star with the Deepest and Longest Known Dimming Event
Davenport, James R. A.; Bellm, Eric C.; Tzanidakis, Anastasios +1 more
We report the serendipitous discovery of Gaia17bpp/2MASS J19372316+1759029, a binary star with a deep single large-amplitude dimming event of ~4.5 mag that lasted over 6.5 yr. Using the optical-to-IR spectral energy distribution (SED), we constrain the primary star to be a cool giant M0III star with effective temperature T eff = 3850 K …
Catching a Milky Way open cluster in its last breath
Piatti, Andrés E.
Theoretical models have suggested peculiar velocity dispersion profiles of star clusters facing dissolution. They predicted that, besides bound stars that still belong to the star cluster, and unbound ones already stripped off, there is an intermediate population of stars that having acquired the enough energy to escape the cluster are still withi…
Implications of time-dependent molecular chemistry in metal-poor dwarf stars
Ludwig, H. -G.; Deshmukh, S. A.
Context. Binary molecules such as CO, OH, CH, CN, and C2 are often used as abundance indicators in stars. These species are usually assumed to be formed in chemical equilibrium. The time-dependent effects of hydrodynamics can affect the formation and dissociation of these species and may lead to deviations from chemical equilibrium.
Variable Blue Straggler Stars in the Open Cluster NGC 6819 Observed in the Kepler "Superstamp" Field
Guzik, Joyce A.; Németh, Péter; Baran, Andrzej S. +4 more
NGC 6819 is an open cluster of age 2.4 Gyr that was in the NASA Kepler spacecraft's field of view from 2009 to 2013. The central part of the cluster was observed in a 200 × 200 pixel "superstamp" during these four years in 30 minute cadence photometry, providing a unique, high-precision, long time-series data set. The cluster contains "blue stragg…
Achromatic rapid flares in hard X-rays in the γ-ray binary LS I + 61 303
Romero, Gustavo E.; Saavedra, Enzo A.; Bosch-Ramon, Valenti +1 more
We report on the presence of very rapid hard X-ray variability in the γ-ray binary LS I + 61 303. The results were obtained by analysing Nuclear Spectroscopic Telescope Array (NuSTAR) data, which show two achromatic strong flares on ks time-scales before apastron. The Swift/Burst Alert Telescope orbital X-ray light curve is also presented, and the…
Infrared He I 10830 Å, ultra-violet Ca II, and Mg II chromosphere emissions in the spectra of classical Cepheid X Cyg
Korotin, S. A.; Andrievsky, S. M.; Kovtyukh, V. V.
Aims: In a previous publication, we reported the first detection of emission in the infrared (IR) triplet at 10 830 Å in the spectra of the classical Cepheid X Cyg. Emission is detectable at phases from approximately 0.25 to 0.90. We present and discuss further information on the chromosphere activity of this star, namely International Ultrav…
MoBiDICT: New 3D static models of close synchronised binaries in hydrostatic equilibrium
Dupret, M. -A.; Fellay, L.
Context. In close binary systems, tidal interactions and rotational effects can strongly influence stellar evolution as a result of mass transfer and common envelope phases. These aspects can only be treated following improvements of theoretical models to take into account the breaking of spherical symmetry occurring in close binaries. Current mod…
A Comparative Study of Ground-level Enhancement Events of Solar Energetic Particles
Vainio, Rami; Riihonen, Esa; Kocharov, Leon +2 more
Major solar eruptions can accelerate protons up to relativistic energies. Solar relativistic ions arriving at 1 au may cause a solar particle event detectable by the worldwide network of neutron monitors (NMs), a ground-level enhancement (GLE) event. Using the newly computed NM yield function, we have fitted the 15 historic GLEs. Moments of the fi…
The X-ray variation of M81* resolved by Chandra and NuSTAR
Wang, Q. Daniel; Yuan, Feng; Long, Min +3 more
Despite advances in our understanding of low-luminosity active galactic nuclei (LLAGNs), the fundamental details about the mechanisms of radiation and flare/outburst in hot accretion flow are still largely missing. We have systematically analysed the archival Chandra and NuSTAR X-ray data of the nearby LLAGN M81*, whose Lbol ~ 10-5…