Search Publications
A Strong Correlation between Circumnuclear Dust and Black Hole Accretion in Early-Type Galaxies
Storchi-Bergmann, Thaisa; Simões Lopes, Ramiro D.; de Fátima Saraiva, Maria +1 more
We present a detailed investigation of the incidence of circumnuclear dust structure in a large, well-matched sample of early-type galaxies with and without active galactic nuclei (AGNs). All 34 early-type AGN hosts in our sample have circumnuclear dust, while dust is only observed in 26% (9) of a pair-matched sample of 34 early-type, inactive gal…
Isolated neutron stars: magnetic fields, distances,and spectra
van Kerkwijk, M. H.; Kaplan, D. L.
We present timing measurements, astrometry, and high-resolution spectra of a number of nearby, thermally emitting, isolated neutron stars. We use these to infer magnetic field strengths and distances, but also encounter a number of puzzles. We discuss three specific ones in detail: (i) For RX J0720.4-3125 and RX J1308.6+2127, the characteristic ag…
The signature of hot hydrogen in the atmosphere of the extrasolar planet HD 209458b
Sing, David K.; Ballester, Gilda E.; Herbert, Floyd
About ten per cent of the known extrasolar planets are gas giants that orbit very close to their parent stars. The atmospheres of these `hot Jupiters' are heated by the immense stellar irradiation. In the case of the planet HD 209458b, this energy deposition results in a hydrodynamic state in the upper atmosphere, allowing for sizeable expansion a…
The Comet Nucleus Sounding Experiment by Radiowave Transmission (CONSERT): A Short Description of the Instrument and of the Commissioning Stages
Plettemeier, D.; Picardi, G.; Elachi, C. +12 more
The primary scientific goal of the CONSERT experiment on the Rosetta space mission is to investigate the deep interior of the nucleus of comet 67/P Churyumov-Gerasimenko. This will be achieved through the use of long wavelength radio-waves, transmitted from the orbiter and returned from the lander. In this overview, a description of the instrument…
Trigonometric Parallaxes of Central Stars of Planetary Nebulae
Harris, Hugh C.; Vrba, Frederick J.; Leggett, S. K. +11 more
Trigonometric parallaxes of 16 nearby planetary nebulae are presented, including reduced errors for seven objects with previous initial results and results for six new objects. The median error in the parallax is 0.42 mas, and 12 nebulae have parallax errors of less than 20%. The parallax for PHL 932 is found here to be smaller than was measured b…
Modeling and Measuring the Flux Reconnected and Ejected by the Two-Ribbon Flare/CME Event on 7 November 2004
Qiu, Jiong; Longcope, Dana; Ravindra, B. +3 more
Observations of the large two-ribbon flare on 7 November 2004 made using SOHO and TRACE data are interpreted in terms of a three-dimensional magnetic field model. Photospheric flux evolution indicates that −1.4×1043 Mx2 of magnetic helicity was injected into the active region during the 40-hour buildup prior to the flare. The…
Evidence for magnetic reconnection initiated in the magnetosheath
Eastwood, J. P.; Lucek, E. A.; Rème, H. +6 more
We report Cluster spacecraft 1 observations of a reconnection exhaust embedded in the magnetosheath flow. The reconnection evidence consists of (1) accelerated plasma outflows, (2) interpenetrating ion beams, (3) reconnection inflows and (4) the associated tangential reconnection electric field. Furthermore, Hall magnetic fields were observed with…
Constraints on Neutron Star Properties from X-Ray Observations of Millisecond Pulsars
Bogdanov, Slavko; Grindlay, Jonathan E.; Rybicki, George B.
We present a model of thermal X-ray emission from hot spots on the surface of a rotating compact star with an unmagnetized light-element atmosphere. An application to ROSAT, Chandra, and XMM-Newton X-ray observations of the nearest known rotation-powered millisecond pulsar (MSP) PSR J0437-4715 reveals that the thermal emission from this pulsar is …
The variable X-ray spectrum of Markarian 766. I. Principal components analysis
Turner, T. J.; Kraemer, S. B.; Reeves, J. N. +3 more
Aims:We analyse a long XMM-Newton observation of the narrow-line Seyfert 1 galaxy Mrk 766, using the marked spectral variability on timescales >20 ks to separate components in the X-ray spectrum.
Methods: Principal components analysis is used to identify distinct emission components in the X-ray spectrum, possible alternative physical model…
Past and Present Star Formation in the SMC: NGC 346 and its Neighborhood
Tosi, M.; Sabbi, E.; Nota, A. +8 more
In the quest to understand how star formation occurs and propagates in the low-metallicity environment of the Small Magellanic Cloud (SMC), we acquired deep F555W (~V) and F814W (~I) Hubble Space Telescope ACS images of the young and massive star-forming region NGC 346. These images and their photometric analysis provide us with a snapshot of the …