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Composition of Coronal Streamers from the SOHO Ultraviolet Coronagraph Spectrometer

Romoli, M.; Raymond, J. C.; Naletto, G. +24 more

The Ultraviolet Coronagraph Spectrometer on the SOHO satellite covers the 940-1350 Å range as well as the 470-630 Å range in second order. It has detected coronal emission lines of H, N, O, Mg, Al, Si, S, Ar, Ca, Fe, and Ni, particularly in coronal streamers. Resonance scattering of emission lines from the solar disk dominates the intensities of a…

Low-Mass Binaries and the Stellar Luminosity Function

Gizis, John E.; Reid, I. Neill

We present a new investigation of the influence of unresolved binaries on the form deduced for the stellar luminosity function from photometric parallax surveys. We have compiled a catalogue of photometry and binary statistics for stars known to be north of -30° declination and within 8 parsecs of the Sun, and have used these stars as a reference …

Interstellar Abundance Gradients in NGC 2403: Comparison to M33

Garnett, D. R.; Skillman, E. D.; Dufour, R. J. +2 more

We present new long-slit spectra of 12 H II regions in the Scd spiral galaxy NGC 2403. Gas-phase element abundances for O, N, S, Ne, and Ar were estimated using direct measurements of electron temperature based on detections of [O III] λ4363, [S III] λ6312, and [O II] λ7320-7330, and from theoretical photoionization analysis. We find abundance gra…

Impact excavation on asteroid 4 Vesta: Hubble Space Telescope results

Binzel, R. P.; Thomas, P. C.; Storrs, A. D. +3 more

A Pair of Lensed Galaxies at z = 4.92 in the Field of CL 1358+62

van Dokkum, Pieter G.; Franx, Marijn; Kelson, Daniel D. +2 more

The cluster CL 1358+62 displays a prominent red arc in WFPC2 images obtained with the Hubble Space Telescope. Keck spectra of the arc show Lyα emission at 7204 Å, a continuum drop blueward of the line, and several absorption lines to the red. We identify the arc as a gravitationally lensed galaxy at a redshift of z = 4.92. It is the highest redshi…

The Structure and Appearance of Protostellar Accretion Disks: Limits on Disk Flaring

Henning, Th.; Bell, K. R.; Cassen, P. M. +1 more

Vertical structure models are used to investigate the structure of protostellar, α-law, accretion disks. Conditions investigated cover a range of mass fluxes (10^-9 to 10^-5 M_⊙ yr^-1), viscous efficiencies (α = 10^-2 and 10^-4), and stellar masses (0.5-3 M_⊙). Analytic formulae…

The nature of intermediate-redshift damped Lyα absorbers.

Deharveng, J. M.; Bergeron, J.; Le Brun, V. +1 more

We present HST/WFPC2 high-spatial resolution images in the R and B bands of the close environment of the sightlines to seven quasars which spectra show either a damped Lyα absorption line, 21cm absorption, or a very strong MgII/FeII absorption system at intermediate redshifts (0.4<=z<=1). Objects down to about 0.3", or 2.0kpc at z=0.6 (H_0_=…

A subsurface flow of material from the Sun's equator to its poles

Scherrer, P. H.; Bogart, R. S.; Duvall, T. L. +1 more

Gas on the Sun's surface has been observed to flow away from the equator towards both poles. If the same flow persists to great depths, it could play an important dynamical role in the eleven-year sunspot cycle, by carrying the magnetic remnants of the sunspots to high latitudes. An even deeper counterflow, which would be required to maintain mass…

Structure and Rotation of the Solar Interior: Initial Results from the MDI Medium-L Program

Kosovichev, A. G.; Hoeksema, J. T.; Scherrer, P. H. +31 more

The medium-l program of the Michelson Doppler Imager instrument on board SOHO provides continuous observations of oscillation modes of angular degree, l, from 0 to ∽ 300. The data for the program are partly processed on board because only about 3% of MDI observations can be transmitted continuously to the ground. The on-board data processing, the …

Evolutionary models for metal-poor low-mass stars. Lower main sequence of globular clusters and halo field stars

Hauschildt, P. H.; Allard, F.; Baraffe, I. +1 more

We have performed evolutionary calculations of very-low-mass stars from 0.08 to 0.8 M_sunl for different metallicites from [M/H]= -2.0 to -1.0 and we have tabulated the mechanical, thermal and photometric characteristics of these models. The calculations include the most recent interior physics and improved non-grey atmosphere models. The models r…