Search Publications
A Transient Heating Model for Coronal Structure and Dynamics
Klimchuk, J. A.; Lanzafame, A. C.; Lanza, A. F. +4 more
A wealth of observational evidence for flows and intensity variations in nonflaring coronal loops leads to the conclusion that coronal heating is intrinsically unsteady and concentrated near the chromosphere. We have investigated the hydrodynamic behavior of coronal loops undergoing transient heating with one-dimensional numerical simulations in w…
A tilted-dipole MHD model of the solar corona and solar wind
Goldstein, M. L.; Usmanov, A. V.
We simulate the three-dimensional structure of the heliosphere during solar activity minimum by specifying boundary conditions at the coronal base. We compare the output of the model with Ulysses observations obtained during the spacecraft's first fast latitude transition in 1994-1995. The polytropic MHD equations are solved for a steady coronal o…
Is There Really a Black Hole at the Center of NGC 4041? Constraints from Gas Kinematics
Marconi, A.; Capetti, A.; Carollo, C. M. +16 more
We present Space Telescope Imaging Spectrograph spectra of the Sbc spiral galaxy NGC 4041, which were used to map the velocity field of the gas in its nuclear region. We detect the presence of a compact (r~=0.4"~=40 pc), high surface brightness, rotating nuclear disk cospatial with a nuclear star cluster. The disk is characterized by a rotation cu…
Proper motions and velocity asymmetries in the RW Aur jet
Dougados, C.; Cabrit, S.; López-Martín, L.
We present adaptive optics spectro-imaging observations of the RW Aur jet in optical forbidden lines, at an angular resolution of 0.4''. Comparison with HST data taken 2 years later shows that proper motions in the blueshifted and redshifted lobes are in the same ratio as their radial velocities, a direct proof that the velocity asymmetry in this …
The detection of stellar velocity dispersion drops in the central regions of five isolated Seyfert spirals
Roth, M.; Durret, F.; González Delgado, R. M. +5 more
We analyze the kinematics of the central regions of five isolated Seyfert spiral galaxies from the DEGAS sample (four with new data presented in this paper, IC 184, UGC 3223, NGC 2639, NGC 6814, and NGC 6951 from our previous data), by using long slit spectroscopy in the CaII triplet range (at ~8600 Å) obtained with a 4 m-class telescope. A drop o…
The 100 Brightest X-Ray Stars within 50 Parsecs of the Sun
Makarov, Valeri V.
Based on the Hipparcos and Tycho-2 astrometric catalogs and the ROSAT surveys, a sample of 100 stars most luminous in X-rays within or around a distance of 50 pc is culled. The smallest X-ray luminosity in the sample, in units of 1029 ergs s-1, is LX=9.8 the strongest source in the solar neighborhood is II Peg, a R…
IBIS/PICsIT in-flight performances
Foschini, L.; Di Cocco, G.; Malaguti, G. +11 more
PICsIT (Pixellated Imaging CaeSium Iodide Telescope) is the high energy detector of the IBIS telescope on-board the INTEGRAL satellite. PICsIT operates in the gamma-ray energy range between 175 keV and 10 MeV, with a typical energy resolution of 10% at 1 MeV, and an angular resolution of 12 arcmin within a ~ 100 square degree field of view, with t…
Eccentric-Disk Models for the Nucleus of M31
Tremaine, Scott; Peiris, Hiranya V.
We construct dynamical models of the ``double'' nucleus of M31 in which the nucleus consists of an eccentric disk of stars orbiting a central black hole. The principal approximation in these models is that the disk stars travel in a Keplerian potential; i.e., we neglect the mass of the disk relative to the black hole. We consider both ``aligned'' …
Mapping the Circumstellar Environment of T Tauri with Fluorescent H2 Emission
Valenti, Jeff A.; Brown, Alexander; Walter, Frederick M. +6 more
We have obtained three long-slit, far-UV spectra of the pre-main-sequence system T Tauri. These Hubble Space Telescope STIS spectra show a strong and variable on-source spectrum composed of both fluoresced H2 and stellar chromospheric lines. Extended H2 emission is seen up to 10" from the T Tau system. The on-source and exten…
A Chandra X-Ray Study of the Dense Globular Cluster Terzan 5
Heinke, C. O.; Cohn, H. N.; Lugger, P. M. +3 more
We report a Chandra ACIS-I observation of the dense globular cluster Terzan 5. The previously known transient low-mass X-ray binary (LMXB) EXO 1745-248 in the cluster entered a rare high state during our 2000 August observation, complicating the analysis. Nevertheless, nine additional sources clearly associated with the cluster are also detected, …