Search Publications
Quasars as standard candles. III. Validation of a new sample for cosmological studies
Marconi, A.; Vignali, C.; Gilli, R. +15 more
We present a new catalogue of ∼2400 optically selected quasars with spectroscopic redshifts and X-ray observations from either Chandra or XMM-Newton. The sample can be used to investigate the non-linear relation between the ultraviolet (UV) and X-ray luminosity of quasars as well as to build a Hubble diagram up to a redshift of z ∼ 7.5. We selecte…
A naked-eye triple system with a nonaccreting black hole in the inner binary
Rivinius, Th.; Baade, D.; Klement, R. +2 more
Several dozen optical echelle spectra demonstrate that
Is HR 6819 a triple system containing a black hole?. An alternative explanation
Shenar, T.; Sana, H.; Hawcroft, C. +10 more
Context. HR 6819 was recently proposed to be a triple system consisting of an inner B-type giant plus black hole (BH) binary with an orbital period of 40 d and an outer Be tertiary. This interpretation is mainly based on two inferences: that the emission attributed to the outer Be star is stationary and that the inner star, which is used as mass c…
Evidence for variability time-scale-dependent UV/X-ray delay in Seyfert 1 AGN NGC 7469
Peterson, Bradley M.; Horne, Keith; Gültekin, Kayhan +5 more
Using a month-long X-ray light curve from RXTE/PCA and 1.5 month-long UV continuum light curves from IUE spectra in 1220-1970 Å, we performed a detailed time-lag study of the Seyfert 1 galaxy NGC 7469. Our cross-correlation analysis confirms previous results showing that the X-rays are delayed relative to the UV continuum at 1315 Šby 3.49 ± 0.22 d…
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…
Atmospheric compositions and observability of nitrogen-dominated ultra-short-period super-Earths
Mollière, Paul; Tsai, Shang-Min; Miguel, Yamila +1 more
We explore the chemistry and observability of nitrogen-dominated atmospheres for ultra-short-period super-Earths. We base the assumption that super-Earths could have nitrogen-filled atmospheres on observations of 55 Cancri e that favour a scenario with a high-mean-molecular-weight atmosphere. We take Titan's elemental budget as our starting point …
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 …
Regulation of accretion by its outflow in a symbiotic star: the 2016 outflow fast state of MWC 560
Sokoloski, J. L.; Luna, G. J. M.; Munari, U. +11 more
How are accretion discs affected by their outflows? To address this question for white dwarfs accreting from cool giants, we performed optical, radio, X-ray, and ultraviolet observations of the outflow-driving symbiotic star MWC 560 (≡V694 Mon) during its 2016 optical high state. We tracked multi-wavelength changes that signalled an abrupt increas…
Mode identification in three pulsating hot subdwarfs observed with TESS satellite
Heber, U.; Irrgang, A.; Raddi, R. +12 more
We report on the detection of pulsations of three pulsating subdwarf B stars observed by the Transiting Exoplanet Survey Satellite (TESS) satellite and our results of mode identification in these stars based on an asymptotic period relation. SB 459 (TIC 067584818), SB 815 (TIC 169285097), and PG 0342 + 026 (TIC 457168745) have been monitored durin…
The 2019 eruption of recurrent nova V3890 Sgr: observations by Swift, NICER, and SMARTS
Ness, J. -U.; Orio, M.; Osborne, J. P. +6 more
V3890 Sgr is a recurrent nova that has been seen in outburst three times so far, with the most recent eruption occurring on 2019 August 27 UT. This latest outburst was followed in detail by the Neil Gehrels Swift Observatory, from less than a day after the eruption until the nova entered the Sun observing constraint, with a small number of additio…