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The properties of the X-ray corona in the distant (z = 3.91) quasar APM 08279+5255
Cappi, M.; Vignali, C.; Gilli, R. +7 more
We present new joint XMM-Newton and NuSTAR observations of APM 08279+5255, a gravitationally-lensed, broad-absorption line quasar (z = 3.91). After showing a fairly stable flux (f2 − 10 ≃ 4 − 5.5 × 10−13 erg s−1) from 2000 to 2008, APM 08279+5255 was found in a fainter state in the latest X-ray exposures (f2 −…
Identification of three cataclysmic variables detected by the ART-XC and eROSITA telescopes on board the SRG during the all-sky X-ray survey
Sunyaev, R.; Sazonov, S.; Burenin, R. +6 more
We report the discovery of three cataclysmic variables in the data of the first year of the all-sky X-ray survey by the SRG orbital observatory. The sources were selected for their brightness in the 4-12 keV band in the data of the Mikhail Pavlinsky ART-XC telescope. They are also detected by the eROSITA telescope, which provides accurate localiza…
Dual storage and release of molecular oxygen in comet 67P/Churyumov-Gerasimenko
Mousis, Olivier; Trattner, Karlheinz J.; Lunine, Jonathan I. +7 more
One of the biggest surprises of the Rosetta mission was the detection of O2 in the coma of 67P/Churyumov-Gerasimenko in remarkably high abundances. The measured levels of O2 in the coma are generally assumed to reflect the overall abundance and chemical origin of cometary O2 in the nucleus. Along with its strong as…
Characterization of Kepler targets based on medium-resolution LAMOST spectra analyzed with ROTFIT
De Cat, P.; Frasca, A.; Wang, J. X. +7 more
Aims: In this work we present the results of our analysis of 16 300 medium-resolution LAMOST spectra of late-type stars in the Kepler field with the aim of determining the stellar parameters, activity level, lithium atmospheric content, and binarity.
Methods: We have used a version of the code ROTFIT specifically developed for the LAMOST…
The LHS 1678 System: Two Earth-sized Transiting Planets and an Astrometric Companion Orbiting an M Dwarf Near the Convective Boundary at 20 pc
Kostov, Veselin B.; Torres, Guillermo; Barclay, Thomas +48 more
We present the Transiting Exoplanet Survey Satellite (TESS) discovery of the LHS 1678 (TOI-696) exoplanet system, comprised of two approximately Earth-sized transiting planets and a likely astrometric brown dwarf orbiting a bright (V J = 12.5, K s = 8.3) M2 dwarf at 19.9 pc. The two TESS-detected planets are of radius 0.7…
Massive Black Hole Formation in Dense Stellar Environments: Enhanced X-Ray Detection Rates in High-velocity Dispersion Nuclear Star Clusters
Stone, Nicholas C.; Ostriker, Jeremiah P.; Baldassare, Vivienne F. +2 more
We analyze Chandra X-ray Observatory imaging of 108 galaxies hosting nuclear star clusters (NSCs) to search for signatures of massive black holes (BHs). NSCs are extremely dense stellar environments with conditions that can theoretically facilitate massive BH formation. Recent work by Stone et al. finds that sufficiently dense NSCs should be unsta…
High-resolution ALMA observations of V4046 Sgr: a circumbinary disc with a thin ring
Garufi, Antonio; Pérez, Sebastián; Casassus, Simon +8 more
The nearby V4046 Sgr spectroscopic binary hosts a gas-rich disc known for its wide cavity and dusty ring. We present high resolution (~20 mas or 1.4 au) ALMA observations of the 1.3 mm continuum of V4046 Sgr which, combined with SPHERE-IRDIS polarised images and a well-sampled spectral energy distribution (SED), allow us to propose a physical mode…
On the dynamical evolution of Cepheids in star clusters
Anderson, Richard I.; Kroupa, Pavel; Dinnbier, František
We investigated the occurrence of classical (type-I) Cepheid variable stars (henceforth Cepheids) in dynamically evolving star clusters from birth to an age of approximately 300 Myr. The clusters are modelled by the Aarseth code NBODY6, and they feature a realistic stellar initial mass function and initial binary star population, single star and b…
Investigating the Low-flux States in Six Intermediate Polars
Littlefield, Colin; Heinke, Craig O.; Mukai, Koji +30 more
We present optical photometry of six intermediate polars that exhibit transitions to a low-flux state. For four of these systems, DW Cnc, V515 And, V1223 Sgr, and RX J2133.7+5107, we are able to perform timing analysis in and out of the low states. We find that, for DW Cnc and V515 And, the dominant periodicities in the light curves change as the …
A systematic comparison of galaxy cluster temperatures measured with NuSTAR and Chandra
Wik, D. R.; Gastaldello, F.; Maughan, B. J. +2 more
Temperature measurements of galaxy clusters are used to determine their masses, which in turn are used to determine cosmological parameters. However, systematic differences between the temperatures measured by different telescopes imply a significant source of systematic uncertainty on such mass estimates. We perform the first systematic compariso…