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Lithium, masses, and kinematics of young Galactic dwarf and giant stars with extreme [α/Fe] ratios
Charbonnel, C.; Prantzos, N.; Borisov, S.
Context. Recent spectroscopic explorations of large Galactic stellar samples stars have revealed the existence of red giants with [α/Fe] ratios that are anomalously high, given their relatively young ages.
Aims: We revisit the GALAH DR3 survey to look for both dwarf and giant stars with extreme [α/Fe] ratios, that is, the upper 1% in the [α/F…
On the Dwarf Irregular Galaxy NGC 6822. I. Young, Intermediate, and Old Stellar Populations
Salaris, Maurizio; Nonino, Mario; Dall'Ora, Massimo +13 more
We present accurate and deep multiband (g, r, i) photometry of the Local Group dwarf irregular galaxy NGC 6822. The images were collected with wide-field cameras at 2 m/4 m (INT, CTIO, CFHT) and 8 m class telescopes (Subaru) covering a 2 deg2 field of view across the center of the galaxy. We performed point-spread function photometry of…
Line-of-sight Elongation and Hydrostatic Mass Bias of the Frontier Fields Galaxy Cluster Abell 370
Koekemoer, Anton M.; Oguri, Masamune; Umetsu, Keiichi +6 more
We present a detailed weak-lensing and X-ray study of the Frontier Fields galaxy cluster Abell 370, one of the most massive known lenses on the sky, using wide-field BR C z' Subaru/Suprime-Cam and Chandra X-ray observations. By combining two-dimensional (2D) shear and azimuthally averaged magnification constraints derived from Subaru da…
Understanding structure in line-driven stellar winds using ultraviolet spectropolarimetry in the time domain
Nazé, Yaël; Ignace, Richard; Scowen, Paul A. +13 more
The most massive stars are thought to lose a significant fraction of their mass in a steady wind during the main-sequence and blue supergiant phases. This in turn sets the stage for their further evolution and eventual supernova, and preconditions the surrounding medium for all following events, with consequences for ISM energization, chemical enr…
Li-rich and super Li-rich giants produced by element diffusion
Shi, Jianrong; Lü, Guoliang; Zhu, Chunhua +4 more
Context. About 0.2−2% of giant stars are Li rich, that is to say their lithium abundance (A(Li)) is higher than 1.5 dex. Nearly 6% of these Li-rich giant stars are super Li rich, with an A(Li) exceeding 3.2 dex. Meanwhile, the formation mechanism of these Li-rich and super Li-rich giants is still under debate.
Aims: Considering the compact He…
SRG/ART-XC discovery of SRGA J204318.2+443815: Towards the complete population of faint X-ray pulsars
Yao, Y.; Kulkarni, S. R.; Bikmaev, I. F. +19 more
We report the discovery of the new long-period X-ray pulsar SRGA J204318.2+443815/SRGe J204319.0+443820 in a Be binary system. The source was found in the second all-sky survey by the Mikhail Pavlinsky ART-XC telescope on board the SRG mission. The follow-up observations with XMM-Newton, NICER, and NuSTAR allowed us to discover a strong coherent s…
Pulsating hydrogen-deficient white dwarfs and pre-white dwarfs observed with TESS. V. Discovery of two new DBV pulsators, WDJ152738.4−450207.4 and WD 1708−871, and asteroseismology of the already known DBV stars PG 1351+489, EC 20058−5234, and EC 04207−4748
Kepler, S. O.; Hermes, J. J.; Althaus, L. G. +9 more
Context. The TESS space mission has recently demonstrated its great potential to discover new pulsating white dwarf and pre-white dwarf stars, and to detect periodicities with high precision in already known white-dwarf pulsators.
Aims: We report the discovery of two new pulsating He-rich atmosphere white dwarfs (DBVs) and present a detailed …
Impact of ionization and electron density gradients in X-ray reflection spectroscopy measurements
Tripathi, Ashutosh; Abdikamalov, Askar B.; Bambi, Cosimo +1 more
The models currently used for the analysis of the reflection spectra of black holes usually assume a disc with constant ionization and electron density. However, there is some debate on the impact of these assumptions on the estimate of the properties of the sources, in particular when the fits suggest very steep emissivity profiles in the inner p…
Tracking X-ray outflows with optical/infrared footprint lines
Turner, T. J.; Kraemer, S. B.; Crenshaw, D. M. +5 more
We use cloudy photoionization models to predict the flux profiles for optical/infrared (IR) emission lines that trace the footprint of X-ray gas, such as [Fe X] 6375 Å and [Si X] 1.43 $\mu\mathrm{m}$. These are subset of coronal lines, from ions with ionization potential greater than or equal to that of O VII, i.e. 138 eV. The footprint lines are …
Predictions of Astrometric Jitter for Sun-like Stars. III. Fast Rotators
Solanki, S. K.; Shapiro, A. I.; Krivova, N. A. +3 more
A breakthrough in exoplanet detections is foreseen with the unprecedented astrometric measurement capabilities offered by instrumentation aboard the Gaia space observatory. Besides, astrometric discoveries of exoplanets are expected from the planned space mission, Small-JASMINE. In this setting, the present series of papers focuses on estimating t…