Search Publications
Far-ultraviolet Observations of Outflows from Infrared-luminous Galaxies
Schaerer, Daniel; Leitherer, Claus; Chandar, Rupali +2 more
We obtained medium-resolution ultraviolet (UV) spectra between 1150 and 1450 Å of the four UV-bright, infrared-luminous starburst galaxies IRAS F08339+6517, NGC 3256, NGC 6090, and NGC 7552 using the Cosmic Origins Spectrograph on board the Hubble Space Telescope. The selected sightlines toward the starburst nuclei probe the properties of the rece…
Hard X-Ray Lags in Active Galactic Nuclei: Testing the Distant Reverberation Hypothesis with NGC 6814
Harrison, F. A.; Fabian, A. C.; Miller, J. M. +7 more
We present an X-ray spectral and temporal analysis of the variable active galaxy NGC 6814, observed with Suzaku during 2011 November. Remarkably, the X-ray spectrum shows no evidence for the soft excess commonly observed amongst other active galaxies, despite its relatively low level of obscuration, and is dominated across the whole Suzaku bandpas…
Detection of Diffuse X-Ray Emission from Planetary Nebulae with Nebular O VI
Steffen, M.; Gruendl, R. A.; Chu, Y. -H. +4 more
The presence of O VI ions can be indicative of plasma temperatures of a few ×105 K that are expected in heat conduction layers between the hot shocked stellar wind gas at several 106 K and the cooler (104 K) nebular gas of planetary nebulae (PNe). We have used FUSE observations of PNe to search for nebular O VI emi…
Ram pressure and dusty red galaxies - key factors in the evolution of the multiple cluster system Abell 901/902
Gray, M. E.; Wolf, C.; Barden, M. +6 more
Aims: We present spectroscopic observations of 182 disk galaxies (96 in the cluster and 86 in the field environment) in the region of the Abell 901/902 multiple cluster system, which is located at a redshift of z ~ 0.165. We estimate dynamical parameters of the four subclusters and analyse the kinematics of spiral galaxies, searching for indi…
On the thermal electron balance in Titan’s sunlit upper atmosphere
Strobel, D. F.; Wahlund, J. -E.; Ågren, K. +8 more
The Cassini mission has investigated Titan’s upper atmosphere in detail and found that, under solar irradiation, it has a well-developed ionosphere, which peaks between 1000 and 1200 km. In this paper we focus on the T40, T41, T42 and T48 Titan flybys by the Cassini spacecraft and use in situ measurements of N2 and CH4 densit…
Studies of NGC 6720 with Calibrated HST/WFC3 Emission-line Filter Images. I. Structure and Evolution
O'Dell, C. R.; Henney, W. J.; Ferland, G. J. +1 more
We have performed a detailed analysis of the Ring Nebula (NGC 6720) using Hubble Space Telescope WFC3 images and derived a new three-dimensional model. Existing high spectral resolution spectra played an important supplementary role in our modeling. It is shown that the Main Ring of the nebula is an ionization-bounded irregular non-symmetric disk …
Further Evidence of the Planetary Nature of HD 95086 b from Gemini/NICI H-band Data
Boccaletti, A.; Lagrange, A. -M.; Bonnefoy, M. +8 more
We present our analysis of the Gemini/NICI H-band data of HD 95086, following the discovery of the planet HD 95086 b in L'. The H-band data reach a contrast of 12.7 mag relative to the host star at 5σ levels in the location of HD 95086 b, and no point source is found. Our non-detection and H - L' color limit rules out the possibility that the obje…
Discovery of very high energy γ-ray emission from the BL Lacertae object PKS 0301-243 with H.E.S.S.
Klochkov, D.; Santangelo, A.; Quirrenbach, A. +211 more
The active galactic nucleus
Phase-resolved ultraviolet spectroscopy of the magnetic Of?p star HD 191612
Bouret, J. -C.; Howarth, I. D.; Wade, G. A. +5 more
We present for the first time phase-resolved ultraviolet (UV) spectroscopy of an Of?p star, namely, HD 191612. The observations were acquired with the Space Telescope Imaging Spectrograph (STIS) onboard the Hubble Space Telescope (HST). We report the variability observed in the main photospheric and wind features and compare the results with previ…
Variable pulse profiles of Hercules X-1 repeating with the same irregular 35 d clock as the turn-ons
Klochkov, D.; Wilms, J.; Staubert, R. +4 more
The accreting X-ray pulsar Her X-1 shows two types of long-term variations, both with periods of ~35 days: 1) turn-on cycles, a modulation of the flux, with a ten-day long main-on and a five-day long short-on, separated by two off-states, and 2) a systematic variation in the shape of the 1.24 s pulse profile. While there is general consensus that …