Search Publications
The Signature of Primordial Grain Growth in the Polarized Light of the AU Microscopii Debris Disk
Matthews, Brenda C.; Graham, James R.; Kalas, Paul G.
We have used the Hubble Space Telescope Advanced Camera for Surveys coronagraph to make the first polarization maps of the AU Microscopii debris disk. The polarization rises from 5% at 20 AU to 40% at 80 AU. The polarization is perpendicular to the disk, indicating that the scattered light originates from micron-sized grains in an optically thin d…
Low-luminosity active galactic nuclei: are they UV faint and radio loud?
Maoz, Dan
Low-luminosity active galactic nuclei (AGNs) are perceived to be radio loud and devoid of a `big blue bump', indicating a transition from a radiatively efficient, geometrically thin, accretion disc in high-luminosity AGNs, to a geometrically thick, radiatively inefficient accretion flow at low luminosities and accretion rates. I revisit the issue …
Cosima High Resolution Time-of-Flight Secondary Ion Mass Spectrometer for the Analysis of Cometary Dust Particles onboard Rosetta
Langevin, Y.; Altwegg, K.; Krüger, H. +38 more
The ESA mission Rosetta, launched on March 2nd, 2004, carries an instrument suite to the comet 67P/Churyumov-Gerasimenko. The COmetary Secondary Ion Mass Anaylzer - COSIMA - is one of three cometary dust analyzing instruments onboard Rosetta. COSIMA is based on the analytic measurement method of secondary ion mass spectrometry (SIMS). The experime…
Magnetic hydrogen atmosphere models and the neutron star RX J1856.5-3754
Ho, Wynn C. G.; Kaplan, David L.; Chang, Philip +2 more
RX J1856.5-3754 is one of the brightest nearby isolated neutron stars (INSs), and considerable observational resources have been devoted to it. However, current models are unable to satisfactorily explain the data. We show that our latest models of a thin, magnetic, partially ionized hydrogen atmosphere on top of a condensed surface can fit the en…
The Hα surges and EUV jets from magnetic flux emergences and cancellations
Yang, L. H.; Li, K. J.; Jiang, Y. C. +2 more
We analyzed multi-wavelength observations of three surges with a recurrent period of about 70 min in Hα, EUV, and soft X-ray, which occurred in the quiet-sun region on 2000 November 3. These homologous surges were associated with small flares at the same base, but their exact footpoints were spatially separated from the flare. Each surge consisted…
Internal Properties of Ultracompact Dwarf Galaxies in the Virgo Cluster
Hilker, M.; Evstigneeva, E. A.; Drinkwater, M. J. +1 more
We present new imaging and spectroscopic observations of six ultracompact dwarf (UCD) galaxies in the Virgo Cluster, along with reanalyzed data for five Fornax Cluster UCDs. These are the most luminous UCDs: -14 mag < MV < -12 mag. Our Hubble Space Telescope imaging shows that most of the UCDs have shallow or steep cusps in their …
X-Ray Absorption from the Milky Way Halo and the Local Group
Bregman, Joel N.; Lloyd-Davies, Edward J.
Million degree gas is present at near-zero redshift and is due to either a gaseous Galactic halo or a more diffuse but very massive Local Group medium. We can discriminate between these models because the column densities should depend on location in the sky, either relative to the Galaxy bulge or to the M31-Milky Way axis. To search for these sig…
Constraining supernova models using the hot gas in clusters of galaxies
Kaastra, J. S.; de Plaa, J.; Vink, J. +3 more
Context: The hot X-ray emitting gas in clusters of galaxies is a very large repository of metals produced by supernovae. During the evolution of clusters, billions of supernovae eject their material into this Intra-Cluster Medium (ICM).
Aims: We aim to accurately measure the abundances in the ICM of many clusters and compare these data with me…
A Narrow-Line Seyfert 1-Blazar Composite Nucleus in 2MASX J0324+3410
Yuan, Weimin; Zhou, Hongyan; Komossa, Stefanie +7 more
We report the identification of 2MASX J032441.19+341045.9 (hereafter 2MASX J0324+3410) with an appealing object that shows the dual properties of both a narrow-line Seyfert 1 galaxy (NLS1) and a blazar. Its optical spectrum, which has a Hβ line width of about 1600 km s-1 (FWHM), an [O III]-to-Hβ line ratio of ~=0.12, and strong Fe II em…
Saturn’s Gravitational Field, Internal Rotation, and Interior Structure
Anderson, John D.; Schubert, Gerald
Saturn’s internal rotation period is unknown, though it must be less than 10 hours, 39 minutes, and 22 seconds, as derived from magnetic field plus kilometric radiation data. By using the Cassini spacecraft’s gravitational data, along with Pioneer and Voyager radio occultation and wind data, we obtain a rotation period of 10 hours, 32 minutes, and…