Results 21 to 30 of about 657 (262)

Disentangling the Planet from the Star in Late-Type M Dwarfs: A Case Study of TRAPPIST-1g [PDF]

The Astronomical Journal, 2018
Abstract The atmospheres of late M stars represent a significant challenge in the characterization of any transiting exoplanets because of the presence of strong molecular features in the stellar atmosphere. TRAPPIST-1 is an ultracool dwarf, host to seven transiting planets, and contains its own molecular signatures that can potentially ...
H. R. Wakeford, N. K. Lewis, J. Fowler, G. Bruno, T. J. Wilson, S. E. Moran, J. Valenti, N. E. Batalha, J. Filippazzo, V. Bourrier, S. M. Hörst, S. M. Lederer, J. de Wit   +12 more
openaire   +3 more sources

Infrared Mn i laboratory oscillator strengths for the study of late type stars and ultracool dwarfs [PDF]

Astronomy & Astrophysics, 2010
Aims. The aim of our new laboratory measurements is to measure accurate absolute oscillator strengths for neutral manganese transitions in the infrared needed for the study of late-type stars and ultracool dwarfs. Methods. Branching fractions have been measured by high resolution Fourier transform spectroscopy and combined with radiative level ...
R. Blackwell-Whitehead, Y. V. Pavlenko, G. Nave, J. C. Pickering, H. R. A. Jones, Y. Lyubchik, H. Nilsson   +6 more
openaire   +1 more source

Titanium abundances in late-type stars

Astronomy & Astrophysics, 2022
Context. The titanium abundances of late-type stars are important tracers of Galactic formation history. However, abundances inferred from Ti I and Ti II lines can be in stark disagreement in very metal-poor giants. Departures from local thermodynamic equilibrium (LTE) have a large impact on the minority neutral species and thus influence the ...
Mallinson, J. W. E., Lind, K., Amarsi, Anish, Barklem, Paul, Grumer, Jon, Belyaev, A. K., Youakim, K.   +6 more
openaire   +3 more sources

X‐Ray Spectroscopy of Rapidly Rotating, Late‐Type Dwarf Stars

The Astrophysical Journal, 1999
We present an X-ray spectroscopic analysis of two active dwarf stars with extremely short rotation periods, HD 197890 (Speedy Mic) and Gliese 890, using X-ray data acquired with the ASCA observatory. We analyze the X-ray spectrum of Speedy Mic in two separate time intervals, one corresponding to an apparent stellar flare, the other to "quiescence" or ...
K. P. Singh, S. A. Drake, E. V. Gotthelf, N. E. White   +3 more
openaire   +1 more source

Mapping the Skies of Ultracool Worlds: Detecting Storms and Spots with Extremely Large Telescopes

The Astrophysical Journal, 2023
Extremely large telescopes (ELTs) present an unparalleled opportunity to study the magnetism, atmospheric dynamics, and chemistry of very-low-mass (VLM) stars, brown dwarfs, and exoplanets.
Michael K. Plummer, Ji Wang
doaj   +1 more source

Stellar Atmospheric Parameters for Cool Dwarfs in Gaia Data Release 3

The Astrophysical Journal Supplement Series
We provide a catalog of atmospheric parameters for 1,806,921 cool dwarfs from Gaia Data Release 3 (DR3) that lie within the range covered by LAMOST cool dwarf spectroscopic parameters: 3200 K < T _eff < 4300 K, −0.8 < [M/H] < 0.2 dex, and 4.5 < log g < 5.
Cai-Xia Qu, A-Li Luo, Rui Wang, Hugh R. A. Jones, Bing Du, Xiang-Lei Chen, You-Fen Wang   +6 more
doaj   +1 more source

Recycling of NiTi Shape Memory Alloys: Fundamental and Technological Aspects of a Vacuum Induction Melting Processing Route

Advanced Engineering Materials, EarlyView.
The present study investigates recycling of NiTi shape memory alloys via vacuum induction melting. An ingot was synthesized from elemental Ni and Ti and subjected to three subsequent remelting cycles. Remelting increases process durations and impurity levels and adversely affects microstructures and functional properties.
Sakia Sophia Noorzayee, Son Tung Mai, Sarath Menon, Braulio Gadiel Sánchez Ortega, Ralf Drautz, Alexander Kauffmann, Gunther Eggeler, Jan Frenzel   +7 more
wiley   +1 more source

The EUVE Optical Identification Campaign II: Late-Type and White Dwarf Stars

The Astronomical Journal, 1995
We present optical identifications of nine previously unidentified extreme ultraviolet (EUV) sources discovered during the Extreme Ultraviolet Explorer (EUVE) satellite surveys. The all-sky survey detected four of the sources and the more sensitive deep survey detected the other five sources.
N. Craig, A. Fruscione, J. Dupuis, M. Mathioudakis, J. J. Drake, M. Abbott, C. Christian, R. Green, T. Boroson, S. B. Howell   +9 more
openaire   +1 more source

Low Cycle Repetitive Loading of Ti‐6Al‐4V‐Epoxy Composite Lattice Structures for Enhanced Energy Dissipation and Damage Tolerance

Advanced Engineering Materials, EarlyView.
Composite Ti–6Al–4V–epoxy lattice structures are additively manufactured and epoxy infiltrated for cyclic loading. At low lattice volume fractions, hybridization produces synergistic gains in stiffness and energy dissipation. At higher volume fractions, synergy diminishes, although composites still exceed metallic lattices in specific energy ...
Joey Tallon, Jordan Noronha, Justin Dirrenberger, Andrey Molotnikov   +3 more
wiley   +1 more source

X-Ray, UV, and Optical Observations of Proxima Centauri’s Stellar Cycle

The Astrophysical Journal
Proxima Cen (GJ 551; dM5.5e) is one of only about a dozen fully convective stars known to have a stellar cycle, and the only one to have long-term X-ray monitoring.
Bradford J. Wargelin, Steven H. Saar, Zackery A. Irving, Jonathan D. Slavin, Peter Ratzlaff, José-Dias do Nascimento Jr   +5 more
doaj   +1 more source