Search Publications
H I content, metallicities and spin temperatures of damped and sub-damped Lyα systems in the redshift desert (0.6 < zabs < 1.7)★
Ellison, Sara L.; Prochaska, J. Xavier; Kanekar, Nissim +2 more
The H I 21-cm absorption optical depth and the N(H I) column density derived from Lyα absorption can be combined to yield the spin temperature (Ts) of intervening damped Lyα systems (DLAs). Although spin temperatures have been determined for samples of DLAs with zabs < 0.6 and zabs > 1.7, the intermediate reg…
BD-22°3467, a DAO-type star exciting the nebula Abell 35
Rauch, T.; Werner, K.; Kruk, J. W. +2 more
Context. Spectral analyses of hot, compact stars with non-local thermodynamical equilibrium (NLTE) model-atmosphere techniques allow the precise determination of photospheric parameters such as the effective temperature (Teff), the surface gravity (log g), and the chemical composition. The derived photospheric metal abundances are cruci…
Photocentric variability of quasars caused by variations in their inner structure: consequences for Gaia measurements
Jovanović, P.; Popović, L. Č.; Stalevski, M. +4 more
Context. We study the photocenter position variability caused by variations in the quasar inner structure. We consider the variability in the accretion disk emissivity and torus structure variability caused by the different illumination by the central source. We discuss the possible detection of these effects by Gaia. Observations of the photocent…
The XMM-Newton view of supergiant fast X-ray transients: the case of IGR J16418-4532
Mereghetti, S.; Sidoli, L.; Sguera, V. +1 more
We report on a 40 ks long, uninterrupted X-ray observation of the candidate supergiant fast X-ray transient (SFXT) IGR J16418-4532 performed with XMM-Newton on 2011 February 23. This high-mass X-ray binary lies in the direction of the Norma arm, at an estimated distance of 13 kpc. During the observation, the source showed strong variability exceed…
Hydrogen Fluoride in High-mass Star-forming Regions
Ceccarelli, C.; Lis, D. C.; Phillips, T. G. +5 more
Hydrogen fluoride (HF) has been established to be an excellent tracer of molecular hydrogen in diffuse clouds. In denser environments, however, the HF abundance has been shown to be approximately two orders of magnitude lower. We present Herschel/HIFI observations of HF J = 1-0 toward two high-mass star formation sites, NGC 6334 I and AFGL 2591. I…
The circumstellar disk of HH 30. Searching for signs of disk evolution with multi-wavelength modeling
Wolf, S.; Guilloteau, S.; Dutrey, A. +1 more
Context. Circumstellar disks are characteristic for star formation and vanish during the first few Myr of stellar evolution. During this time planets are believed to form in the dense midplane by growth, sedimentation and aggregation of dust. Indicators of disk evolution, such as holes and gaps, can be traced in the spectral energy distribution (S…
The first outburst of the black-hole candidate MAXI J1836-194 observed by INTEGRAL, Swift, and RXTE
Capitanio, F.; Ferrigno, C.; Bozzo, E. +1 more
MAXI J1836-194 is a transient black-hole candidate discovered in outburst on 30 August 2011. We report on the available INTEGRAL, Swift, and RXTE observations performed in the direction of the source during this event before 55 864 MJD. Combining the broad band (0.6-200 keV) spectral and timing information obtained from these data with the results…
Gasa impact crater, Mars: Very young gullies formed from impact into latitude-dependent mantle and debris-covered glacier deposits?
Head, James W.; Schon, Samuel C.
The mode of formation of gullies on Mars, very young erosional-depositional landforms consisting of an alcove, channel, and fan, is one of the most enigmatic problems in martian geomorphology. Major questions center on their ages, geographic and stratigraphic associations, relation to recent ice ages, and, if formed by flowing water, the sources o…
The ROSAT-ESO flux limited X-ray galaxy cluster survey (REFLEX II). I. Newly identified X-ray luminous clusters at z ≥ 0.2
Böhringer, H.; Chon, G.
We report 19 intermediate redshift clusters newly detected in the ROSAT All-Sky survey that are spectroscopically confirmed. They form a part of 911 objects in the REFLEX II cluster catalogue with a limiting flux of 1.8 × 10-12 erg/s/cm2 in the 0.1-2.4 keV ROSAT band at redshift z ≥ 0.2. In addition we report three clusters f…
The Close T Tauri Binary System V4046 Sgr: Rotationally Modulated X-Ray Emission from Accretion Shocks
Donati, J. -F.; Audard, M.; Güdel, M. +11 more
We report initial results from a quasi-simultaneous X-ray/optical observing campaign targeting V4046 Sgr, a close, synchronous-rotating classical T Tauri star (CTTS) binary in which both components are actively accreting. V4046 Sgr is a strong X-ray source, with the X-rays mainly arising from high-density (n e~ 1011-1012…