Search Publications
Molecular gas in two companion cluster galaxies at z = 1.2
Pannella, M.; Andreon, S.; Heywood, I. +8 more
Context. Probing both star formation history and evolution of distant cluster galaxies is essential to evaluate the effect of dense environment on shaping the galaxy properties we observe today.
Aims: We investigate the effect of cluster environment on the processing of the molecular gas in distant cluster galaxies. We study the molecular gas…
Charge exchange in galaxy clusters
Raassen, A. J. J.; Gu, Liyi; Mao, Junjie +3 more
Context. Though theoretically expected, the charge exchange emission from galaxy clusters has never been confidently detected. Accumulating hints were reported recently, including a rather marginal detection with the Hitomi data of the Perseus cluster. As previously suggested, a detection of charge exchange line emission from galaxy clusters would…
New database for a sample of optically bright lensed quasars in the northern hemisphere
Gil-Merino, R.; Goicoechea, L. J.; Oscoz, A. +1 more
In the framework of the Gravitational LENses and DArk MAtter (GLENDAMA) project, we present a database of nine gravitationally lensed quasars (GLQs) that have two or four images brighter than r = 20 mag and are located in the northern hemisphere. This new database consists of a rich variety of follow-up observations included in the GLENDAMA global…
Spectroscopic identification of INTEGRAL high-energy sources with VLT/ISAAC
Chaty, S.; Tomsick, J. A.; Coleiro, A. +2 more
Context. The INTEGRAL satellite has been observing the γ-ray sky for 15 years and has detected over 900 X-ray sources of various nature. However, more than 200 of these sources still lack precise identification.
Aims: Our goal is to reveal the nature of the high-energy sources detected by INTEGRAL. In particular, we want to improve the census…
Gaia Data Release 2. Validating the classification of RR Lyrae and Cepheid variables with the Kepler and K2 missions
Molnár, László; Rimoldini, Lorenzo; Plachy, Emese +1 more
Context. The second data release of the Gaia mission (DR2) includes an advance catalogue of variable stars. The classifications of these stars are based on sparse photometry from the first 22 months of the mission.
Aims: We set out to investigate the purity and completeness of the all-sky Gaia classification results with the help of the conti…
Whipping IC 63/IC 59
Tielens, A. G. G. M.; Okada, Y.; Peeters, E. +1 more
Context. IC 63 and IC 59 are a pair of cometary-shaped nebulae in the vicinity of the star γCas (also known as Tsih, "the Whip"). Both nebulae have very different optical appearances, despite the fact that both objects lie at similar projected distances from the star: IC 63 shows bright rims and filaments, while IC 59 looks more homogeneous and fa…
NGC 4051: Black hole mass and photon index-mass accretion rate correlation
Titarchuk, Lev; Seifina, Elena; Chekhtman, Alexandre
We present a discovery of the correlation between the X-ray spectral (photon) index and mass accretion rate observed in an active galactic nucleus, NGC 4051. We analyzed spectral transition episodes observed in NGC 4051 using XMM-Newton, Suzaku and RXTE. We applied a scaling technique for a black hole (BH) mass evaluation which uses a correlation …
Short-term variability and mass loss in Be stars. IV. Two groups of closely spaced, approximately equidistant frequencies in three decades of space photometry of ν Puppis (B7-8 IIIe)
Wang, L.; Handler, G.; Carciofi, A. C. +13 more
Context. In early-type Be stars, groups of nonradial pulsation (NRP) modes with numerically related frequencies may be instrumental for the release of excess angular momentum through mass-ejection events. Difference and sum/harmonic frequencies often form additional groups.
Aims: The purpose of this study is to find out whether a similar freq…
Measuring the Wilson depression of sunspots using the divergence-free condition of the magnetic field vector
Solanki, S. K.; Lagg, A.; Löptien, B. +1 more
Context. The Wilson depression is the difference in geometric height of unit continuum optical depth between the sunspot umbra and the quiet Sun. Measuring the Wilson depression is important for understanding the geometry of sunspots. Current methods suffer from systematic effects or need to make assumptions on the geometry of the magnetic field. …
Extended VHE γ-ray emission towards SGR1806-20, LBV 1806-20, and stellar cluster Cl* 1806-20
Klochkov, D.; Santangelo, A.; Quirrenbach, A. +242 more
Using the High Energy Spectroscopic System (H.E.S.S.) telescopes we have discovered a steady and extended very high-energy (VHE) γ-ray source towards the luminous blue variable candidate LBV 1806-20, massive stellar cluster Cl* 1806-20, and magnetar SGR 1806-20. The new VHE source, HESS J1808-204, was detected at a statistical significance of >…