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Ripples, Transverse Aeolian Ridges, and Dark-Toned Sand Dunes on Mars: A Case Study in Terra Sabaea
Lu, Y.; Edgett, K. S.; Wu, Y. Z.
Ripples, transverse aeolian ridges (TARs), and dark-toned sand sheets and dunes are common aeolian bedforms on the Martian surface. They are important for understanding the nature of present-day Martian sediments and regional aeolian processes. Here we present a case study investigation of ripples, TARs, a dark-toned sand sheet, and dunes in an un…
HATS-34b and HATS-46b: re-characterization using TESS and Gaia
Hartman, Joel D.; Louden, Emma M.
We present a revised characterization of the previously discovered transiting planet systems HATS-34 and HATS-46. We make use of the newly available space-based light curves from the NASA TESS mission and high-precision parallax and absolute photometry measurements from the ESA Gaia mission to determine the mass and radius of the planets and host …
Spitzer Mid-infrared Study of Sh 2-208: Evolution of Protoplanetary Disks in Low-metallicity Environments
Yasui, Chikako
This study presents sensitive mid-infrared (MIR) photometry obtained with the Spitzer/IRAC for a young cluster in Sh 2-208 (S208) located in one of the lowest-metallicity H II regions in the Galaxy, $[{\rm{O}}/{\rm{H}}]=-0.8$ dex. Previous studies suggested that the cluster is ~0.5 Myr old and has a distance of D = 4 kpc, which is consistent with …
Energetic particle distributions in space physics represented by the Pearson differential equation for the kappa distribution
Shizgal, Bernie D.
The kappa distribution has been used for decades as a numerical fitting function to represent the energetic particle distributions measured with satellite instruments. The distributions are generally either a three dimensional distribution in the particle velocity or the one dimensional distribution in a velocity component in a particular directio…
Implications of the Low-frequency Turnover in the Spectrum of Radio Knot C in DG Tau
Björnsson, C. -I.
The synchrotron spectrum of radio knot C in the protostellar object DG Tau has a low-frequency turnover. This is used to show that its magnetic field strength is likely to be at least 10 mG, which is roughly two orders of magnitude larger than previously estimated. The earlier, lower value is due to an overestimate of the emission volume together …
Chandra X-Ray Observations of V830 Tau: A T Tauri Star Hosting an Evanescent Planet
Skinner, Stephen L.; Güdel, Manuel
The radial velocity study by Donati et al. (2016) reported the detection of a close-in giant planet in a 4.93 day orbit around the ~2 Myr old weak-lined T Tauri star V830 Tau. Because of the stringent timescale constraints that a very young host star like V830 Tau would place on hot-Jupiter formation models and inward-migration mechanisms, indepen…
Heliospheric Magnetic Field and The Parker Model
Bazilevskaya, G. A.; Svirzhevsky, N. S.; Kalinin, M. S. +4 more
In the Parker model of the heliospheric magnetic field, the ratio of the azimuthal field component
The frequency by mass of Galactic carbon stars inferred from Gaia measurements of star cluster members
Worthey, G.; Pal, Tathagata
We investigate the frequency of occurrence of Galactic carbon stars as a function of progenitor mass using Gaia data. Small number statistics limit fidelity, but C-star frequency agrees with that observed in the Magellanic Clouds (MCs) down to m ≈ 1.67 M⊙. At m ≈ 1.38 M⊙, the frequency rises by a factor of three even though t…
Mass Ratios of Long-Period Binary Stars Resolved in Precision Astrometry Catalogs of Two Epochs
Makarov, V. V.
Mass ratios of widely separated, long-period, resolved binary stars can be directly estimated from the available data in major space astrometry catalogs, such as the ESA's Hipparcos and Gaia mission results. The method is based on the universal principle of inertial motion of the system's center of mass in the absence of external forces, and is in…
Interstellar Extinction and Polarization of Stars in the Open Cluster NGC 7160
Topasna, G. A.; Riley, R. W.; Kaltcheva, N. T.
We present polarimetric observations of stars in the field of the open cluster NGC 7160. The multi-wavelength UBVRI polarization measurements of 21 stars that we performed indicate that some of the observed stars follow the typical wavelength dependence indicative of polarization by selective extinction in the interstellar medium, while others dis…