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Helium-like triplet density diagnostics. Applications to CHANDRA-LETGS X-ray observations of Capella and Procyon
Schmitt, J. H. M. M.; Kaastra, J. S.; Burwitz, V. +6 more
Electron density diagnostics based on the triplets of helium-like C v, N vi, and O vii are applied to the X-ray spectra of Capella and Procyon measured with the Low Energy Transmission Grating Spectrometer (LETGS) on board the Chandra X-ray Observatory. New theoretical models for the calculation of the line ratios between the forbidden (f), interc…
Cusped Mass Models of Gravitational Lenses
Keeton, C. R.; Kochanek, C. S.; Muñoz, J. A.
Recent observations of galaxy luminosity profiles and dark matter simulations find luminosity and mass distributions characterized by central cusps rather than finite core radii. We introduce and implement a set of cusped ellipsoidal lens models that include limits similar to the Jaffe, Hernquist, η and NFW models and apply them to the gravitation…
Radial Velocity Studies of Close Binary Stars. V.
Rucinski, Slavek M.; Lu, Wenxian; Mochnacki, Stefan W. +2 more
Radial velocity measurements and sine-curve fits to the orbital velocity variations are presented for the fifth set of 10 close binary systems: V376 And, EL Aqr, EF Boo, DN Cam, FN Cam, V776 Cas, SX Crv, V351 Peg, EQ Tau, and KZ Vir. All systems are double-lined, spectroscopic contact binaries (KZ Vir may be a low-inclination, close, noncontact bi…
A Study of Chromospheric Oscillations Using the SOHO and TRACE Spacecraft
Wilhelm, Klaus; Judge, Philip G.; Tarbell, Theodore D.
We analyze line and continuum time-series data of the solar atmosphere, with between 10 and 60 s cadence, using the MDI and SUMER instruments on the SOHO spacecraft and the UV bandpasses on the TRACE satellite. The co-aligned data sets sample spectral features formed from photosphere to the middle transition region, spanning five decades in pressu…
Non-axisymmetric accretion on the classical TTS RW Aur A
Tuominen, I.; Gahm, G. F.; Gameiro, J. F. +5 more
High-resolution spectroscopic monitoring of the exceptionally active classical T Tauri star (CTTS) RW Aur A was carried out in three seasons of 1996, 1998 and 1999 with simultaneous B, V photometry. The high quality spectra revealed a multicomponent structure of the spectrum, which includes: 1) a veiled photospheric spectrum of a K1-K4 star, 2) br…
Old Stellar Populations of the Small Magellanic Cloud
Dolphin, Andrew E.; Schommer, Robert A.; Mateo, Mario +4 more
We present WFPC2 and ground-based VI photometry of NGC 121 and a nearby field in the outer SMC. For NGC 121, we measure a true distance modulus of µ0=18.96+/-0.04 (distance of 61.9+/-1.1 kpc), age of 10.6+/-0.5 Gyr, metallicity of [Fe/H]=-1.03+/-0.06, and initial mass of 4.1+/-0.4×105 Msolar, assuming a Salpe…
Evidence for the Heating of Atomic Interstellar Gas by Polycyclic Aromatic Hydrocarbons
Dale, Daniel A.; Malhotra, Sangeeta; Helou, George +2 more
We report a strong correlation between the [C II] 158 µm cooling line and the mid-infrared flux in the 5-10 µm range in a wide variety of star-forming galaxies. The mid-infrared flux is dominated by the aromatic features in emission (AFEs), which are thought to arise from large polycyclic aromatic hydrocarbons (PAHs) and are generally …
The Discovery of a Second Luminous Low-Mass X-Ray Binary in the Globular Cluster M15
White, Nicholas E.; Angelini, Lorella
We report an observation by the Chandra X-Ray Observatory of 4U 2127+119, the X-ray source identified with the globular cluster M15. The Chandra observation reveals that 4U 2127+119 is in fact two bright sources, separated by 2.7". One source is associated with AC 211, the previously identified optical counterpart to 4U 2127+119, a low-mass X-ray …
Erupting Solar Magnetic Flux Ropes: Theory and Observation
Thompson, B. J.; Chen, J.; Howard, R. A. +2 more
Measurements of coronograph (LASCO) and extreme-ultraviolet (EIT) images are presented for 11 coronal mass ejection (CME) events. Detailed measurements of these events, selected because they have flux-rope-like morphological features, show excellent agreement with results from a theoretical model of erupting flux-rope dynamics. Here, data are used…
Four-point high time resolution information on electron densities by the electric field experiments (EFW) on Cluster
Vaivads, A.; Gustafsson, G.; Décréau, P. +7 more
For accurate measurements of electric fields, spherical double probes are electronically controlled to be at a positive potential of approximately 1 V relative to the ambient magnetospheric plasma. The spacecraft will acquire a potential which balances the photoelectrons escaping to the plasma and the electron flux collected from the plasma. The p…