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Comparison of Kinematics of Solar Eruptive Prominences and Spatial Distribution of the Magnetic Decay Index
Myshyakov, Ivan; Tsvetkov, Tsvetan
Theoretical studies of electric current instability explaining solar prominence eruptions show that the loss of equilibrium may develop in a case when the surrounding magnetic field decreases sufficiently rapidly with height. The magnetic decay index, a parameter indicating whether the external magnetic field has a configuration that may lead to a…
Li-rich giant stars under scrutiny: binarity, magnetic activity, and the evolutionary status after Gaia DR2
Castro, M.; da Costa, J. S.; de Almeida, L. +2 more
We present a study of the evolutionary state of a few lithium-rich giant stars based on the Gaia Data Release 2 (DR2) parallaxes and photometry. We also investigate the chromospheric activity, the presence of a surface magnetic field, and the radial velocity for our sample stars. We analysed both archive and new data. We gathered archive spectra f…
Strömgren metallicities for intermediate-age and old star clusters
Piatti, Andrés E.
We report results that show that the straightforward star cluster metallicities obtained from Strömgren vby photometry are age-dependent and need to be corrected for further use. This outcome arises from the comparison of [Fe/H] values derived from Strömgren photometry with those metallicities published in the literature for 26 Large and Small Mag…
High-velocity interstellar absorption associated with the supernova remnant W28
Ritchey, Adam M.
We present an analysis of moderately high-resolution optical spectra obtained for the sightline to CD-23 13777, an O9 supergiant that probes high-velocity interstellar gas associated with the supernova remnant W28. Absorption components at both high positive and high negative velocity are seen in the interstellar Na I D and Ca II H and K lines tow…
Evidence for Transparency and Clumps in the Circumbinary Ring of the T Tauri Star V582 Mon (KH 15D)
Winn, Joshua N.; Herbst, William; Newmark, Amanda +3 more
The binary T Tauri star V582 Mon (KH 15D) is surrounded by a tilted and nodally precessing ring of dusty material, which has caused periodic occultations of one or both stars over the last 50 years. Here, we present multi-color time-series photometry (VRIJHK) throughout the 2017/2018 observing season, when the ring was covering the entire orbit of…
Testing ΛCDM with Dwarf Galaxy Morphology
Xu, Weishuang Linda; Randall, Lisa
The leading tensions to the collisionless cold dark matter (CDM) paradigm are the "small-scale controversies," discrepancies between observations at the dwarf-galactic scale, and their simulational counterparts. In this work we consider methods to infer 3D morphological information on Local Group dwarf spheroidals and test the fitness of CDM+hydro…
Pleiades or Not? Resolving the Status of the Lithium-rich M Dwarfs HHJ 339 and HHJ 430
Oppenheimer, Rebecca; Aigrain, Suzanne; Hillenbrand, Lynne A. +7 more
Oppenheimer et al. discovered two M5 dwarfs in the Pleiades with nearly primordial lithium. These stars are not low enough in mass to represent the leading edge of the lithium depletion boundary at Pleiades age (∼125 Myr). A possible explanation for the enhanced lithium in these stars is that they are actually not members of the Pleiades but inste…
Which stars can see Earth as a transiting exoplanet?
Kaltenegger, L.; Pepper, J.
Transit observations have found the majority of exoplanets to date. Also spectroscopic observations of transits and eclipses are the most commonly used tool to characterize exoplanet atmospheres and will be used in the search for life. However, an exoplanet's orbit must be aligned with our line of sight to observe a transit. Here, we ask, from whi…
Two Quasi-periodic Oscillations in ESO 113-G010
Zhang, Peng; Yan, Jing-Zhi; Liu, Qing-Zhong
In the narrow-line Seyfert galaxy (NLS1) ESO 113-G010, two quasi-periodic oscillation (QPO) signals are detected in the XMM-Newton data collected in 2005 November. The XMM-Newton telescope has an exposure longer than 100 ks in the energy range of 0.3-10 keV. The data are analyzed using the Lomb-Scargle periodogram (LSP) and the weighted wavelet Z-…
Estimation of the Gould Belt Scale Height from T Tauri Type Stars in the Gaia DR2 Catalog
Bobylev, V. V.; Bajkova, A. T.
—We analyze the spatial and kinematic properties of a large sample of young T Tauri type stars in a 500 pc radius solar neighborhood, closely related to the Gould belt. The following parameters of the exponential density distribution have been determined: the average