Search Publications
Pulsational instability of pre-main-sequence models from accreting protostars. I. Constraining the input physics for accretion with spectroscopic parameters and stellar pulsations
Zwintz, K.; Barnes, T. G.; Steindl, T. +2 more
Context. The picture of pre-main-sequence evolution is often simplified by the application of classical initial models. Such models have large initial radii and sufficient uniform contraction to make them fully convective, however, real stars are born as small protostellar seeds in collapsing molecular clouds and obtain their final mass by means o…
Flux conservation, radial scalings, Mach numbers, and critical distances in the solar wind: magnetohydrodynamics and Ulysses observations
Verscharen, Daniel; Velli, Marco; Bale, Stuart D.
One of the key challenges in solar and heliospheric physics is to understand the acceleration of the solar wind. As a super-sonic, super-Alfvénic plasma flow, the solar wind carries mass, momentum, energy, and angular momentum from the Sun into interplanetary space. We present a framework based on two-fluid magnetohydrodynamics to estimate the flu…
Strong dependence of the physical properties of cores on spatial resolution in observations and simulations
Men'shchikov, A.; Didelon, P.; Motte, F. +3 more
The angular resolution of a telescope is the primary observational parameter, along with the detector sensitivity in defining the quality of the observed images and of the subsequent scientific exploitation of the data. During the last decade in star formation research, many studies have targeted low- and high-mass star formation regions located a…
A Case against a Significant Detection of Precession in the Galactic Warp
López-Corredoira, M.; Chrobáková, Ž.
Recent studies of warp kinematics using Gaia DR2 data have produced detections of warp precession for the first time, which greatly exceeds theoretical predictions of models. However, this detection assumes a warp model derived for a young population (few tens of megayears) to fit velocities of an average older stellar population of the thin disk …
Strong Mg II and Fe II Absorbers at 2.2 < z < 6.0
Willott, Chris J.; Shen, Yue; Ho, Luis C. +13 more
We present a study of strong intervening absorption systems in the near-IR spectra of 31 luminous quasars at z > 5.7. The quasar spectra were obtained with Gemini GNIRS that provide continuous wavelength coverage from ∼0.9 to ∼2.5 µm. We detect 32 strong Mg II doublet absorbers with rest-frame equivalent width Wr(λ2796) > 1.…
Dynamical Masses and Stellar Evolutionary Model Predictions of M Stars
Herczeg, Gregory J.; Wilner, David J.; Andrews, Sean M. +9 more
In this era of Gaia and ALMA, dynamical stellar mass measurements, derived from spatially and spectrally resolved observations of the Keplerian rotation of circumstellar disks, provide benchmarks that are independent of observations of stellar characteristics and their uncertainties. These benchmarks can then be used to validate and improve stella…
Semiempirical Modeling of the Atmospheres of the M Dwarf Exoplanet Hosts GJ 832 and GJ 581
France, Kevin; Linsky, Jeffrey L.; Buccino, Andrea P. +2 more
Stellar ultraviolet (UV) radiation drives photochemistry, and extreme-ultraviolet (EUV) radiation drives mass loss in exoplanet atmospheres. However, the UV flux is partly unobservable due to interstellar absorption, particularly in the EUV range (100-912 Å). It is therefore necessary to reconstruct the unobservable spectra in order to characteriz…
TOI-532b: The Habitable-zone Planet Finder confirms a Large Super Neptune in the Neptune Desert orbiting a metal-rich M-dwarf host
Kobulnicky, Henry A.; Cochran, William D.; Mahadevan, Suvrath +30 more
We confirm the planetary nature of TOI-532b, using a combination of precise near-infrared radial velocities with the Habitable-zone Planet Finder, Transiting Exoplanet Survey Satellite (TESS) light curves, ground-based photometric follow up, and high-contrast imaging. TOI-532 is a faint (J ~ 11.5) metal-rich M dwarf with Teff = 3957 ± 6…
Assessing the Projection Correction of Coronal Mass Ejection Speeds on Time of Arrival Prediction Performance Using the Effective Acceleration Model
Vourlidas, Angelos; Papaioannou, Athanasios; Anastasiadis, Anastasios +1 more
White light images of coronal mass ejections (CMEs) are projections on the plane of sky (POS). As a result, CME kinematics are subject to projection effects. The error in the true (deprojected) speed of CMEs is one of the main causes of uncertainty to Space Weather forecasts, since all estimates of the CME time of arrival (ToA) at a certain locati…
The Atacama Cosmology Telescope: A Search for Planet 9
Hasselfield, Matthew; Sifón, Cristóbal; Aiola, Simone +37 more
We use Atacama Cosmology Telescope (ACT) observations at 98 GHz (2015-2019), 150 GHz (2013-2019), and 229 GHz (2017-2019) to perform a blind shift-and-stack search for Planet 9. The search explores distances from 300 au to 2000 au and velocities up to 6.'3 per year, depending on the distance (r). For a 5 Earth-mass Planet 9 the detection limit var…