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Short- and long-term near-infrared spectroscopic variability of eruptive protostars from VVV
Minniti, D.; Alonso-García, J.; Lucas, P. W. +7 more
Numerous eruptive variable young stellar objects (YSOs), mostly Class I systems, were recently detected by the near-infrared Vista Variables in the Via Lactea (VVV) survey. We present an exploratory near-infrared spectroscopic variability study of 14 eruptive YSOs. The variations were sampled over one-day and one-to-two-year intervals and analysed…
A combined timing/spectral study of IRAS 13224-3809 using XMM-Newton data
Papadakis, I. E.; Dovčiak, M.; Karas, V. +3 more
We present the results from an X-ray variability study of IRAS 13224-3809. This is probably the best source for X-ray reverberation studies since it is X-ray bright, extremely variable, and it has been extensively observed with XMM-Newton. We used all the archival XMM-Newton data from the three EPIC cameras (to increase the signal to noise) and, g…
Properties of five z ∼ 0.3-0.4 confirmed LyC leakers: VLT/XShooter observations
Schaerer, D.; Ramambason, L.; Izotov, Y. I. +7 more
Using new Very Large Telescope (VLT)/XShooter spectral observations we analyse the physical properties of five z ~ 0.3-0.4 confirmed Lyman continuum (LyC) leakers. Strong resonant Mg II λλ2796, 2803 Å emission lines (I(λλ2796, 2803)/I(Hβ) ≃ 10-38 per cent) and non-resonant Fe II* λλ2612, 2626 Å emission lines are observed in spectra of five and th…
COol Companions ON Ultrawide orbiTS (COCONUTS). I. A High-gravity T4 Benchmark around an Old White Dwarf and a Re-examination of the Surface-gravity Dependence of the L/T Transition
Magnier, Eugene A.; Hermes, J. J.; Marley, Mark S. +7 more
We present the first discovery from the COol Companions ON Ultrawide orbiTS (COCONUTS) program, a large-scale survey for wide-orbit planetary and substellar companions. We have discovered a comoving system COCONUTS-1, composed of a hydrogen-dominated white dwarf (PSO J058.9855+45.4184; d = 31.5 pc) and a T4 companion (PSO J058.9869+45.4296) at a 4…
A plethora of new, magnetic chemically peculiar stars from LAMOST DR4
Paunzen, E.; Bernhard, K.; Hümmerich, S.
Context. Magnetic chemically peculiar (mCP) stars are important to astrophysics because their complex atmospheres lend themselves perfectly to the investigation of the interplay between such diverse phenomena as atomic diffusion, magnetic fields, and stellar rotation. The most up-to-date catalogue of these objects was published a decade ago. Since…
The Multiplanet System TOI-421
Henning, Thomas; Butler, R. Paul; Hellier, Coel +110 more
We report the discovery of a warm Neptune and a hot sub-Neptune transiting TOI-421 (BD-14 1137, TIC 94986319), a bright (V = 9.9) G9 dwarf star in a visual binary system observed by the Transiting Exoplanet Survey Satellite (TESS) space mission in Sectors 5 and 6. We performed ground-based follow-up observations—comprised of Las Cumbres Observator…
The Stellar Velocity Distribution Function in the Milky Way Galaxy
Majewski, Steven R.; Beers, Timothy C.; Hayes, Christian R. +6 more
The stellar velocity distribution function in the solar vicinity is reexamined using data from the Sloan Digital Sky Survey Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey's DR16 and Gaia DR2. By exploiting APOGEE's ability to chemically discriminate with great reliability the thin-disk, thick-disk, and (accreted) halo popul…
The stellar and wind parameters of six prototypical HMXBs and their evolutionary status
Hamann, W. -R.; Oskinova, L. M.; Sander, A. A. C. +7 more
Context. High-mass X-ray binaries (HMXBs) are exceptional astrophysical laboratories that offer a rare glimpse into the physical processes that govern accretion on compact objects, massive-star winds, and stellar evolution. In a subset of the HMXBs, the compact objects accrete matter solely from winds of massive donor stars. These so-called wind-f…
Carbon stars as standard candles: I. The luminosity function of carbon stars in the Magellanic Clouds
Heyl, Jeremy; Richer, Harvey; Ripoche, Paul +1 more
Our goal in this paper is to derive a carbon-star luminosity function that will eventually be used to determine distances to galaxies at 50-60 Mpc and hence yield a value of the Hubble constant. Cool N-type carbon stars exhibit redder near-infrared colours than oxygen-rich stars. Using Two Micron All Sky Survey near-infrared photometry and the Gai…
Open Cluster Chemical Homogeneity throughout the Milky Way
Beaton, Rachael L.; Hawkins, K.; Cunha, K. +10 more
The chemical homogeneity of surviving stellar clusters contains important clues about interstellar medium (ISM) mixing efficiency, star formation, and the enrichment history of the Galaxy. Existing measurements in a handful of open clusters suggest homogeneity in several elements at the 0.03 dex level. Here we present (i) a new cluster member cata…