Science Archives Publication System

A Protocometary Cloud around HR 4796A?

DOI: 10.1086/306184 Bibcode: 1998ApJ...505..897J

Telesco, C.; Malkan, M.; Fisher, R. S. +3 more

We report both ROSAT observations and ground-based 10.8 µm imaging of the wide binary HR 4796, which consists of a main-sequence A-type star with a large amount of circumstellar dust, HR 4796A, and, at a separation of 7.7", a pre-main-sequence M-type companion, HR 4796B. From the ROSAT data, we find that the X-ray emission is centered on HR …

1998 • The Astrophysical Journal

Hipparcos 113

The Luminosity Function of the Globular Cluster NGC 6397 near the Limit of Hydrogen Burning

DOI: 10.1086/311082 Bibcode: 1998ApJ...492L..37K

Anderson, Jay; Piotto, Giampaolo; Cool, Adrienne M. +1 more

Second-epoch Hubble Space Telescope observations of NGC 6397 have led to the measurement of proper motions accurate enough to separate the faintest cluster stars from the field, thus extending the luminosity function of this globular cluster far enough to approach the limit of hydrogen burning on the main sequence. We isolate a sample of 1385 main…

1998 • The Astrophysical Journal

eHST 113

Strömgren Photometry of Globular Clusters: The Distance and Age of M13, Evidence for Two Populations of Horizontal-Branch Stars

DOI: 10.1086/311419 Bibcode: 1998ApJ...500L.179G

Grundahl, Frank; VandenBerg, Don A.; Andersen, Michael I.

We present deep CCD photometry of the globular cluster M13 (NGC 6205) in the Strömgren uvbyβ system and determine a foreground reddening of E(b-y)=0.015+/-0.01 mag. From a fit to the main sequence of metal-poor subdwarfs with Hipparcos parallaxes, we derive (m-M)₀=14.38+/-0.10, which implies an age near 12 Gyr assuming [Fe/H] = -1.61 an…

1998 • The Astrophysical Journal

Hipparcos 112

HIPPARCOS Parallaxes and the Cepheid Distance Scale

DOI: 10.1086/305041 Bibcode: 1998ApJ...492..110M

Madore, Barry F.; Freedman, Wendy L.

Hipparcos parallaxes have recently become available for a sample of Galactic Cepheids, and we have used these new distances to calibrate the Cepheid period-luminosity (PL) relation at six wavelengths (BVIJHK). Comparing these calibrations with previously published multiwavelength PL relations we find agreement to within 0.07 +/- 0.14 mag, or 4% +/…

1998 • The Astrophysical Journal

Hipparcos 112

Radii and Effective Temperatures for K and M Giants and Supergiants. II.

DOI: 10.1086/300453 Bibcode: 1998AJ....116..981D

van Belle, G. T.; Thompson, R. R.; Dyck, H. M.

We present new interferometric observations for 74 luminous red stars, made in the near-infrared. We show that our 2.2 µm uniform-disk diameters agree with other near-infrared diameter determinations (lunar occultations and interferometers) for 22 stars measured in common with ours. From our new data, we derive effective temperatures that ar…

1998 • The Astronomical Journal

Hipparcos 111

Jet-Driven Motions in the Narrow-Line Region of NGC 1068

DOI: 10.1086/311249 Bibcode: 1998ApJ...496L..75A

Marconi, A.; Macchetto, F. D.; Capetti, A. +3 more

We have obtained Hubble Space Telescope Faint Object Camera (FOC) f/48 long-slit spectroscopy of the inner 4" of the narrow-line region (NLR) of NGC 1068 between 3500 and 5400 Å with a spectral resolution of 1.78 Å pixel^-1. At a spatial scale of 0.0287" pixel^-1 these data provide an order-of-magnitude improvement in resolutio…

1998 • The Astrophysical Journal

eHST 111

The Extragalactic Distance Scale Key Project. XVI. Cepheid Variables in an Inner Field of M101

DOI: 10.1086/306443 Bibcode: 1998ApJ...508..491S

Kelson, Daniel D.; Illingworth, Garth D.; Huchra, John P. +20 more

We report on the identification of 255 candidate variable stars in a field located some 1.7 arcmin from the center of the late-type spiral galaxy M101 = NGC 5457, based on observations made with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope. Photometric measurements in the F555W and F814W filters--analyzed independently…

1998 • The Astrophysical Journal

eHST 111

Clustering at High Redshift: Precise Constraints from a Deep, Wide-Area Survey

DOI: 10.1086/306245 Bibcode: 1998ApJ...506...33P

Lauer, Tod R.; Oegerle, William; Postman, Marc +1 more

We present constraints on the evolution of large-scale structure from a catalog of 710,000 galaxies with I_AB <= 24 derived from a KPNO 4 m CCD imaging survey of a contiguous 4° × 4° region. The advantage of using large contiguous surveys for measuring clustering properties on even modest angular scales is substantial: the effects of …

1998 • The Astrophysical Journal

eHST 111

Galactic Cosmic-Ray Confinement Time: Ulysses High Energy Telescope Measurements of the Secondary Radionuclide ¹⁰Be

DOI: 10.1086/311437 Bibcode: 1998ApJ...501L..59C

Connell, J. J.

We report new measurements of the isotopic abundances of the Galactic cosmic-ray isotopes ⁷Be, ⁹Be, and radioactive ¹⁰Be. These measurements from the Ulysses High Energy Telescope (HET) combine exceptional mass resolution with superior statistics. Measurements of radioisotopes produced as secondaries during cosmic-…

1998 • The Astrophysical Journal

Ulysses 109

Revised ages for stars in the solar neighbourhood

DOI: 10.48550/arXiv.astro-ph/9707043 Bibcode: 1998A&A...329..943N

Bertelli, G.; Ng, Y. K.

New ages are computed for the stars from the Edvardsson et al. (1993) data set. The revised values are systematically larger toward older ages (t>4 Gyr), while they are slightly lower for t<4 Gyr. A similar, but considerably smaller trend is present when the ages are computed with the distances based on Hipparcos parallaxes. The resulting ag…

1998 • Astronomy and Astrophysics

Hipparcos 109