Search Publications
Gas and dust in the star-forming region ρ Oph A. II. The gas in the PDR and in the dense cores
Liseau, R.; Larsson, B.
Context. The evolution of interstellar clouds of gas and dust establishes the prerequisites for star formation. The pathway to the formation of stars can be studied in regions that have formed stars, but which at the same time also display the earliest phases of stellar evolution, i.e. pre-collapse/collapsing cores (Class -1), protostars (Class 0)…
Quantitative spectroscopy of extreme helium stars Model atmospheres and a non-LTE abundance analysis of BD+10°2179
Butler, K.; Heber, U.; Przybilla, N. +3 more
Extreme helium stars (EHe stars) are hydrogen-deficient supergiants of spectral type A and B. They are believed to result from mergers in double degenerate systems. In this paper, we present a detailed quantitative non-LTE spectral analysis for BD+10°2179, a prototype of this rare class of stars, using UV-Visual Echelle Spectrograph and Fiber-fed …
Atmospheric waves and dynamics beneath Jupiter's clouds from radio wavelength observations
de Pater, Imke; Butler, Bryan; Morales-Juberías, Raúl +3 more
We observed Jupiter at wavelengths near 2 cm with the Karl G. Jansky Very Large Array (VLA) in February 2015. These frequencies are mostly sensitive to variations in ammonia abundance and probe between ∼ 0.5 - 2.0 bars of pressure in Jupiter's atmosphere; within and below the visible cloud deck which has its base near 0.7 bars. The resultant obser…
Tidal disruption of stars by super-massive black holes—XMM-Newton highlights and the next decade
Komossa, S.
This article provides a summary of XMM-Newton highlights on stellar tidal disruption events. First found with ROSAT, ongoing and upcoming sky surveys will detect these events in the thousands. In X-rays, tidal disruption events (TDEs) provide us with powerful new probes of accretion physics under extreme conditions and on short timescales and of r…
A high spectral resolution map of the nuclear emitting regions of NGC 7582
Bianchi, S.; Piconcelli, E.; Reeves, J. N. +2 more
We present the results of the spatial and spectral analysis of the deep ( 200 ks) Chandra HETG observation of the changing look AGN NGC 7582. During this long Chandra observation, NGC 7582 was in a highly obscured state. Therefore, we also consider a short ( 24 ks) Suzaku observation, which caught NGC 7582 in a Compton thick state. This allows us …
Extragalactic background light: a measurement at 400 nm using dark cloud shadow*†- I. Low surface brightness spectrophotometry in the area of Lynds 1642
Leinert, Ch.; Väisänen, P.; Lehtinen, K. +2 more
We present the method and observations for the measurement of the Extragalactic Background Light (EBL) utilizing the shadowing effect of a dark cloud. We measure the surface brightness difference between the opaque cloud core and its unobscured surroundings. In the difference the large atmospheric and Zodiacal light components are eliminated and t…
A Tale of Two Impostors: SN2002kg and SN1954J in NGC 2403
Van Dyk, Schuyler D.; Humphreys, Roberta M.; Davidson, Kris +1 more
We describe new results on two supernova impostors in NGC 2403, SN 1954J(V12) and SN 2002kg(V37). For the famous object SN 1954J, we combine four critical observations: its current SED, its Hα emission line profile, the Ca II triplet in absorption in its red spectrum, and the brightness compared to its pre-event state. Together, these strongly sug…
The 26 December 2001 Solar Eruptive Event Responsible for GLE63. II. Multi-Loop Structure of Microwave Sources in a Major Long-Duration Flare
Kochanov, A. A.; Kiselev, V. I.; Uralov, A. M. +1 more
Our analysis of the observations of the SOL2001-12-26 event, which was related to ground-level enhancement of cosmic-ray intensity GLE63, including microwave spectra and images from the Nobeyama Radioheliograph at 17 and 34 GHz, from the Siberian Solar Radio Telescope at 5.7 GHz, and from the Transition Region and Coronal Explorer in 1600 Å, has l…
Investigating prominence turbulence with Hinode SOT Dopplergrams
Ichimoto, K.; Matsumoto, T.; Hillier, A.
Quiescent prominences host a diverse range of flows, including Rayleigh-Taylor instability driven upflows and impulsive downflows, and so it is no surprise that turbulent motions also exist. As prominences are believed to have a mean horizontal guide field, investigating any turbulence they host could shed light on the nature of magnetohydrodynami…
Hierarchical Probabilistic Inference of the Color-Magnitude Diagram and Shrinkage of Stellar Distance Uncertainties
Leistedt, Boris; Hogg, David W.
We present a hierarchical probabilistic model for improving geometric stellar distance estimates using color-magnitude information. This is achieved with a data-driven model of the color-magnitude diagram, not relying on stellar models but instead on the relative abundances of stars in color-magnitude cells, which are inferred from very noisy magn…