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Nitrogen-containing Anions and Tholin Growth in Titan’s Ionosphere: Implications for Cassini CAPS-ELS Observations
Coates, Andrew J.; Carrasco, Nathalie; Desai, Ravindra T. +4 more
The Cassini Plasma Spectrometer (CAPS) Electron Spectrometer (ELS) instrument on board Cassini revealed an unexpected abundance of negative ions above 950 km in Titan’s ionosphere. In situ measurements indicated the presence of negatively charged particles with mass-over-charge ratios up to 13,800 u/q. At present, only a handful of anions have bee…
Membership and fundamental parameters of the Praesepe cluster based on Gaia-DR2
Gao, Xin-hua
In this paper, we investigate membership and fundamental astrophysical parameters of the nearby, intermediate-age Praesepe star cluster (M44) based on the Gaia data release 2 (Gaia-DR2). Based on 54 425 stars within a sky area of 5.5° radius, we identify 1111 likely cluster members (≥0.6) in an 11D parameter space based on a combined machine-learn…
Is Supernova Remnant Cassiopeia A a PeVatron?
Zhang, Xiao; Liu, Siming
Cassiopeia A, a well-observed young core-collapse supernova remnant (SNR), is considered to be one of the best candidates for studying very high-energy particle acceleration up to PeV via the diffusive shock mechanism. Recently, MAGIC observations revealed a γ-ray spectral cutoff at ∼ 3.5 {TeV}, suggesting that if the TeV γ-rays have a hadronic or…
Halo intruders in the Galactic bulge revealed by HST and Gaia: the globular clusters Terzan 10 and Djorgovski 1
Bica, E.; Nardiello, D.; Barbuy, B. +2 more
Context. The low-latitude globular clusters Terzan 10 and Djorgovski 1 are projected in the Galactic bulge, in a Galactic region highly affected by extinction. A discrepancy of a factor of ∼2 exists in the literature in regards to the distance determination of these clusters.
Aims: We revisit the colour-magnitude diagrams (CMDs) of these two …
Identifying Spectral Lines to Study Coronal Mass Ejection Evolution in the Lower Corona
Landi, Enrico; Rivera, Yeimy J.; Lepri, Susan T.
As prominences propagate away from the Sun via a coronal mass ejection (CME), they expand, accelerate, and are strongly heated. The heating is substantial enough to continuously ionize the prominence plasma, making it difficult to follow its dynamic evolution with a single extreme ultraviolet (EUV) narrow-band channel or a white light instrument. …
Chandra-HETGS Characterization of an Outflowing Wind in the Accreting Millisecond Pulsar IGR J17591-2342
Wilms, Jörn; Chenevez, Jérôme; Rodriguez, Jérôme +5 more
An accreting millisecond X-ray pulsar, IGR J17591-2342 was discovered in 2018 August in scans of the Galactic bulge and center by the International Gamma-Ray Astrophysics Laboratory X-ray and gamma-ray observatory. It exhibited an unusual outburst profile with multiple peaks in the X-ray, as observed by several X-ray satellites over 3 months. Here…
Dust-depletion sequences in damped Lyman-α absorbers. II. The composition of cosmic dust, from low-metallicity systems to the Galaxy
Petitjean, Patrick; De Cia, Annalisa; Andersen, Anja C. +1 more
Metals in the interstellar medium (ISM) of essentially all types of galaxies are observed to be depleted compared to the expected values. The depletion is most likely due to dust condensation in, for example, cold molecular clouds and various circumstellar and interstellar environments. The relative observed metal abundances should thereby reflect…
K2-291b: A Rocky Super-Earth in a 2.2 day Orbit
Vanderburg, Andrew; López-Morales, Mercedes; Latham, David W. +43 more
K2-291 is a solar-type star with a radius of R * = 0.899 ± 0.034 R ⊙ and mass of M* = 0.934 ± 0.038 M ⊙. From the K2 C13 data, we found one super-Earth planet (R p = {1.589}-0.072+0.095 R ⊕) transiting this star on a short period orbit (P = {2.225177}-6.…
Is there a fundamental upper limit to the mass of a star cluster?
Leaman, Ryan; Schinnerer, Eva; van de Ven, Glenn +2 more
The discovery around the turn of the millennium of a population of very massive (M⋆ > 2 × 106 M⊙) compact stellar systems (CSS) with physical properties (radius, velocity dispersion, stellar mass etc.) that are intermediate between those of the classical globular cluster (GC) population and galaxies led to quest…
Ultraviolet and optical spectroscopy of AGB stars showing UV excess
Guerrero, Martín A.; Ortiz, Roberto; Costa, Roberto D. D.
We have examined ultraviolet (UV) and optical UB spectra of 20 UV-emitting Asymptotic Giant Branch (AGB) stars of various variability classes to study the intensity of the continuum and emission lines as a function of stellar visual magnitude to shed light on the origin of their UV emission. A significant fraction (60 per cent) of these stars show…