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Fundamental effective temperature measurements for eclipsing binary stars - I. Development of the method and application to AI Phoenicis
Maxted, P. F. L.; Smalley, B.; Miller, N. J.
Stars with accurate and precise effective temperature (Teff) measurements are needed to test stellar atmosphere models and calibrate empirical methods to determine Teff. There are few standard stars currently available to calibrate temperature indicators for dwarf stars. Gaia parallaxes now make it possible, in principle, to …
A Microlensing Accretion Disk Size Measurement in the Lensed Quasar WFI 2026-4536
Millon, Martin; Bonvin, Vivien; Bentz, Misty C. +4 more
We use 13 seasons of R-band photometry from the 1.2 m Leonard Euler Swiss Telescope at La Silla to examine microlensing variability in the quadruply imaged lensed quasar WFI 2026-4536. The lightcurves exhibit ∼0.2 mag of uncorrelated variability across all epochs and a prominent single feature of ∼0.1 mag within a single season. We analyze this va…
Amplification of Brightness Variability by Active-region Nesting in Solar-like Stars
Solanki, Sami K.; Shapiro, Alexander I.; Krivova, Natalie A. +1 more
Kepler observations revealed that hundreds of stars with near-solar fundamental parameters and rotation periods have much stronger and more regular brightness variations than the Sun. Here we identify one possible reason for the peculiar behavior of these stars. Inspired by solar nests of activity, we assume that the degree of inhomogeneity of act…
A Supernova Candidate at z = 0.092 in XMM-Newton Archival Data
Mereghetti, Sandro; Esposito, Paolo; Tiengo, Andrea +14 more
During a search for X-ray transients in the XMM-Newton archive within the EXTraS project, we discovered a new X-ray source that is detected only during an ∼5 min interval of an ∼21 hr-long observation performed on 2011 June 21 (EXMM 023135.0-603743, probability of a random Poissonian fluctuation: ∼1.4 × 10-27). With dedicated follow-up …
The Evolution of Rotation and Magnetic Activity in 94 Aqr Aa from Asteroseismology with TESS
Chaplin, William J.; Stassun, Keivan G.; Metcalfe, Travis S. +29 more
Most previous efforts to calibrate how rotation and magnetic activity depend on stellar age and mass have relied on observations of clusters, where isochrones from stellar evolution models are used to determine the properties of the ensemble. Asteroseismology employs similar models to measure the properties of an individual star by matching its no…
Speckle Interferometry at SOAR in 2019
Tokovinin, Andrei; Horch, Elliott P.; Mason, Brian D. +2 more
The results of speckle-interferometric observations at the 4.1 m Southern Astrophysical Research Telescope in 2019 are given, totaling 2555 measurements of 1972 resolved pairs with separations from 15 mas (median 0"21) and magnitude difference up to 6 mag, and non-resolutions of 684 targets. We resolved for the first time 90 new pairs or subsystem…
Discovery of a Giant Radio Fossil in the Ophiuchus Galaxy Cluster
Wik, D. R.; Giacintucci, S.; Markevitch, M. +3 more
The Ophiuchus galaxy cluster exhibits a curious concave gas density discontinuity at the edge of its cool core. It was discovered in the Chandra X-ray image by Werner and collaborators, who considered the possibility of it being a boundary of an active galactic nucleus (AGN)-inflated bubble located outside the core, but discounted this possibility…
The changing-type SN 2014C may come from an 11-M⊙ star stripped by binary interaction and violent eruption
Sun, Ning-Chen; Crowther, Paul A.; Maund, Justyn R.
SN 2014C was an unprecedented supernova (SN) that displayed a metamorphosis from Type Ib to Type IIn over ∼200 d. This transformation is consistent with a helium star having exploded in a cavity surrounded by a dense shell of the progenitor's stripped hydrogen envelope. For at least 5 yr post-explosion, the ejecta continued to interact with an out…
Modeling the Lyα transit absorption of the hot Jupiter HD 189733b
Holmström, M.; Lammer, H.; Fossati, L. +7 more
Context. Hydrogen-dominated atmospheres of hot exoplanets expand and escape hydrodynamically due to the intense heating by the X-ray and extreme ultraviolet (XUV) irradiation of their host stars. Excess absorption of neutral hydrogen has been observed in the Lyα line during transits of several close-in gaseous exoplanets, indicating such extended …
Zodiacal Exoplanets in Time (ZEIT). IX. A Flat Transmission Spectrum and a Highly Eccentric Orbit for the Young Neptune K2-25b as Revealed by Spitzer
Gaidos, Eric; Dalba, Paul A.; Rizzuto, Aaron C. +9 more
Transiting planets in nearby young clusters offer the opportunity to study the atmospheres and dynamics of planets during their formative years. To this end, we focused on K2-25b—a close-in (P = 3.48 days), Neptune-sized exoplanet orbiting a M4.5 dwarf in the 650 Myr Hyades cluster. We combined photometric observations of K2-25 covering a total of…