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Acoustic Signatures of Subphotospheric Structure Underlying Sunspots
Braun, D. C.; Lindsey, C.
Helioseismic holography of active regions at frequencies in the range of 5-6 mHz renders acoustic signatures that we think signify acoustic perturbations several megameters beneath the photosphere. The application of holographic diagnostics at 5-6 mHz gives us images with considerably finer horizontal spatial resolution, and likewise much finer de…
The symbiotic system AG Dra: an unexpected photometric period
Bastian, U.
A photometric period of about 380 days is found in 6810 visual magnitude estimates of AG Dra. This is unexpected, since the orbital period of the system is about 552 days. The period is confirmed by Hipparcos photometry. The new periodicity provides an additional constraint on physical models for AG Dra. Detailed observations before the end of the…
ISO Detection of CO(+) toward the protostar IRAS 16293-2422
White, G. J.; Ceccarelli, C.; Caux, E. +4 more
In this letter we report the detection of eight high-N rotational transitions of CO(+) towards a low mass protostar, IRAS 16293-2422. The source was observed with the Long Wavelength Spectrometer on board the Infrared Space Observatory. This is the first time that CO(+) has been detected in a low luminosity source and the first time that high-N li…
Hubble Space Telescope WFPC2 Imaging of the Seyfert Galaxy NGC 3516
Mulchaey, John S.; Ferruit, Pierre; Wilson, Andrew S.
We have used the WFPC2 camera aboard the Hubble Space Telescope to obtain images of the Seyfert galaxy NGC 3516 in the [O III] λ5007 and [N II] λλ6548, 6583 + Hα emission lines as well as in their adjacent continua. The emission-line images reveal a close morphological association between an arclike structure 1.7" north of the nucleus and radio em…
Kinematics of the local universe. VI. B-band Tully-Fisher relation and mean surface brightness
Theureau, G.
Continuing our study of the type dependence of the TF relation, we present a new attempt to reduce the scatter of that relation by using the observed mean surface brightness Sigma of galaxies. It is shown that the zero-point of the relation is a continuous function of Sigma , well described by a third or fourth degree polynome. Taking this effect …
The Eclipsing Supersoft X-Ray Binary CAL 87
Hutchings, J. B.; Crampton, D.; Cowley, A. P. +1 more
We present and discuss 25 spectra obtained in 1996 November, covering all phases of the CAL 87 binary system. These spectra are superior both in signal-to-noise ratio and wavelength coverage to previously published data, so additional spectral features can be measured. Photometry obtained on the same nights is used to confirm the ephemeris and for…
WFPC2 Observations of the Small Magellanic Cloud Intermediate-Age Populous Cluster NGC 416
Sarajedini, Ata; Mighell, Kenneth J.; French, Rica S.
We present our analysis of archival Hubble Space Telescope Wide Field Planetary Camera 2 observations in F555W (~V) and F450W (~B) of the intermediate-age populous star cluster NGC 416 in the Small Magellanic Cloud (SMC). We use published photometry of two other SMC populous star clusters, Lindsay 1 and Lindsay 113, to investigate the age sequence…
The Ultraviolet Albedo of Titan
Smith, T. Ed; Feldman, Paul D.; Strobel, Darrell F. +2 more
Ultraviolet spectra of Titan obtained with the Faint Object Spectrograph of the Hubble Space Telescope in October 1991 and August 1992 have yielded a disk-average geometric albedo of 0.02-0.044 from 1800-3300 Å. These results are in excellent agreement with previous UV measurements from 2200-3300 Å spanning two decades, but have a significantly hi…
Latitudinal distribution of >106MeV protons and its relation to the ambient solar wind in the inner southern and northern heliosphere: Ulysses Cosmic and Solar Particle Investigation Kiel Electron Telescope results
Sierks, H.; Kunow, H.; Bothmer, V. +12 more
We present observations and model calculations of the modulated intensities of galactic cosmic ray protons above 106 MeV/n along the Ulysses trajectory. Data are taken by the Cosmic and Solar Particle Investigation (COSPIN) Kiel Electron Telescope (KET) from spring 1993 to fall 1996. During this time period solar activity decreased and galactic co…
On the Unresolved Fine Structures of the Solar Atmosphere. III. Elemental Abundances Consideration
Feldman, Uri
Results from high-quality solar upper atmosphere observations in the 104-106 K range contradict predictions made by models that assume that a single class of structures stretching throughout the entire temperature domain, from the cold chromosphere to the hot corona, is responsible for all the radiation we see. As a result, I…