Search Publications
Do Deltas Along the Crustal Dichotomy Boundary of Mars in the Gale Crater Region Record a Northern Ocean?
Rivera-Hernández, Frances; Palucis, Marisa C.
Deltaic deposits mapped along the Martian crustal dichotomy boundary scarp have been suggested to delineate an ancient ocean in the northern lowlands of Mars. Using recently acquired orbital data, we have expanded the dichotomy delta inventory and performed an updated analysis of delta front elevations, a proxy for paleo-water levels. Our analysis…
No surviving non-compact stellar companion to Cassiopeia A
Justham, Stephen; Do, Tuan; Milisavljevic, Dan +7 more
Massive stars in binaries can give rise to extreme phenomena such as X-ray binaries and gravitational wave sources after one or both stars end their lives as core-collapse supernovae. Stars in close orbit around a stellar or compact companion are expected to explode as "stripped-envelope supernovae", showing no (Type Ib/c) or little (Type IIb) sig…
Ongoing star formation at the outskirts of Sextans A: spectroscopic detection of early O-type stars
Garcia, Miriam; Herrero, Artemio; Najarro, Francisco +2 more
With both nebular- and stellar-derived abundances of ≲1/10 Z_{⊙ } and low foreground extinction, Sextans A is a prime candidate to replace the Small Magellanic Cloud as reservoir of metal-poor massive stars and reference to study the metal-poor Universe. We report the discovery of two early O-type stars in Sextans A, the earliest O-type stars with…
A new radio molecular line survey of planetary nebulae. HNC/HCN as a diagnostic of ultraviolet irradiation
Kastner, J. H.; Alcolea, J.; Santander-García, M. +3 more
Certain planetary nebulae (PNe) contain shells, filaments, or globules of cold gas and dust whose heating and chemistry are likely driven by UV and X-ray emission from their central stars and from wind-collision-generated shocks. We present the results of a survey of molecular line emission in the 88-236 GHz range from nine nearby (<1.5 kpc) pl…
The Gaia-ESO Survey: Age spread in the star forming region NGC 6530 from the HR diagram and gravity indicators
Gilmore, G.; Franciosini, E.; Randich, S. +33 more
Context. In very young clusters, stellar age distribution is empirical proof of the duration of star cluster formation and thus it gives indications of the physical mechanisms involved in the star formation process. Determining the amount of interstellar extinction and the correct reddening law are crucial steps to derive fundamental stellar param…
Chemical Cartography. II. The Assembly History of the Galactic Stellar Halo Traced by Carbon-enhanced Metal-poor Stars
Beers, Timothy C.; Lee, Young Sun; Kim, Young Kwang
We present an analysis of the kinematic properties of stellar populations in the Galactic halo, making use of over 100,000 main-sequence turnoff (MSTO) stars observed in the Sloan Digital Sky Survey. After dividing the Galactic halo into an inner-halo region (IHR) and outer-halo region (OHR), based on the spatial variation of carbon-to-iron ratios…
A Dynamical Model for Clustered Star Formation in the Galactic Disk
Conroy, Charlie; Ting, Yuan-Sen; Cargile, Phillip +3 more
The clustered nature of star formation should produce a high degree of structure in the combined phase and chemical space in the Galactic disk. To date, observed structure of this kind has been mostly limited to bound clusters and moving groups. In this paper, we present a new dynamical model of the Galactic disk that takes into account the cluste…
Revisiting the potassium feature of WASP-31b at high resolution
Nikolov, Nikolay; de Mooij, Ernst J. W.; Gibson, Neale P. +4 more
The analysis and interpretation of exoplanet spectra from time-series observations remains a significant challenge to our current understanding of exoplanet atmospheres, due to the complexities in understanding instrumental systematics. Previous observations of the hot Jupiter WASP-31b using transmission spectroscopy at low resolution have present…
Superflares on AB Doradus observed with TESS
Schmitt, J. H. M. M.; Czesla, S.; Robrade, J. +2 more
We present short-cadence data of the ultra-active star AB Dor measured by the Transiting Exoplanet Survey Satellite (TESS). In the TESS light curves of AB Dor, we found numerous flare events in addition to time-variable rotational modulation with an amplitude of up to 7%. We identified eight superflares (releasing more than 1034 erg) an…
First Observations of Irregular Surface of Interplanetary Shocks at Ion Scales by Cluster
Kajdič, Primož; Blanco-Cano, Xóchitl; Burgess, David +2 more
We present the first observational evidence of the irregular surface of interplanetary (IP) shocks by using multispacecraft observations of the Cluster mission. In total we discuss observations of four IP shocks that exhibit moderate Alfvénic Mach numbers (M A ≤ 6.5). Three of them are high-β shocks with upstream β = 2.2-3.7. During the…