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Early Noachian terrains: Vestiges of the early evolution of Mars
Dohm, James M.; Buczkowski, Debra; Anderson, Robert C. +1 more
NASA's main scientific reason for exploring Mars is to determine the early evolution and the possibility of life on the red planet. Scientists have adopted an approach for identifying habitable environments on Mars that could be conducive to the early development and preservation of life (e.g., robotically exploring hydrothermal and lake deposits …
Expanding shells around young clusters - S 171/Be 59
Persson, C. M.; Gahm, G. F.; Wilhelm, M. J. C. +2 more
Context. Some HII regions that surround young stellar clusters are bordered by molecular shells that appear to expand at a rate inconsistent with our current model simulations. In this study we focus on the dynamics of Sharpless 171 (including NGC 7822), which surrounds the cluster Berkeley 59.
Aims: We aim to compare the velocity pattern ove…
Gaia GraL: Gaia DR2 Gravitational Lens Systems. VII. XMM-Newton Observations of Lensed Quasars
Djorgovski, S. G.; Connor, Thomas; Walton, Dominic J. +23 more
We present XMM-Newton X-ray observations of nine confirmed lensed quasars at 1 ≲ z ≲ 3 identified by the Gaia Gravitational Lens program. Eight systems are strongly detected, with 0.3-8.0 keV fluxes F 0.3-8.0 ≳ 5 ×10-14 erg cm-2 s-1. Modeling the X-ray spectra with an absorbed power law, we derive power-…
Reconciling Observational Challenges to the Impulsive-Piston Shock-Excitation Scenario. II. Shock Waves Produced in CME-Less Events with a Null-Point Topology
Grechnev, V. V.; Kiselev, V. I.; Uralov, A. M. +1 more
Continuing Article I, we revisit challenging events previously identified by different authors, whose analysis led to conclusions about various mechanisms of the shock-wave excitation. Here, we reconsider four events that involved fan-spine coronal configurations with a null-point topology (NPT). The presence of Type-II radio bursts in all events …
Using machine learning to identify extragalactic globular cluster candidates from ground-based photometric surveys of M87
Clarkson, William I.; Kundu, Arunav; Dage, Kristen C. +6 more
Globular clusters (GCs) have been at the heart of many longstanding questions in many sub-fields of astronomy and, as such, systematic identification of GCs in external galaxies has immense impacts. In this study, we take advantage of M87's well-studied GC system to implement supervised machine learning (ML) classification algorithms - specificall…
Lithium Detection in Red Supergiant Stars of the Perseus Complex
Dalessandro, E.; Sanna, N.; Mucciarelli, A. +3 more
We present the first systematic study of lithium abundance in a chemically homogeneous sample of 27 red supergiants (RSGs) in the young Perseus complex. For these stars, accurate stellar parameters and detailed chemical abundances of iron and iron peak, CNO, alpha, light, and neutron capture elements have already been obtained by means of high-res…
XMM-Newton study of six massive, X-ray luminous galaxy cluster systems in the redshift range z = 0.25-0.5
Böhringer, H.; Laporte, N.; Ellis, R. S. +2 more
Massive galaxy clusters are interesting astrophysical and cosmological objects to study, but they are relatively rare. In the redshift range z = 0.25-0.5 which is, for example, a favourable region for gravitational lensing studies, about 100 such systems are known. Most of them have been studied in X-rays. In this paper we study the six remaining …
Deep and fast Solar System flybys: the controversial case of WD 0810-353
de la Fuente Marcos, R.; de la Fuente Marcos, C.
Context. Most flybys in the Galactic disk are distant, beyond 104 AU, and have characteristic velocities of ~70 km s−1. However, deep and fast encounters also take place, albeit with lower probability, particularly if one of the objects involved is a stellar remnant ejected during a supernova. WD 0810-353 might be a high velo…
The miniJPAS survey: White dwarf science with 56 optical filters
Tremblay, P. -E.; Mendes de Oliveira, C.; Guerrero, M. A. +21 more
Aims: We analyze the white dwarf population in miniJPAS, the first square degree observed with 56 medium-band, 145 Å in width optical filters by the Javalambre Physics of the accelerating Universe Astrophysical Survey (J-PAS), to provide a data-based forecast for the white dwarf science with low-resolution (R ∼ 50) photo-spectra.
Methods…
Observations of the First Harmonic of Saturn Kilometric Radiation During Cassini's Grand Finale
Lamy, Laurent; Fischer, Georg; Kurth, William S. +6 more
Clear first harmonic emissions of Saturn Kilometric Radiation are discovered during the Cassini Grand Finale orbits. Both ordinary (O) and extraordinary (X) mode fundamental emissions accompanied by X mode harmonics are observed. Analysis shows that the frequency ratio between the fundamental and harmonic emissions is 2.01 ± 0.08, and the harmonic…