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The reality of old moving groups - the case of HR 1614. Age, metallicity, and a new extended sample
Holmberg, J.; Feltzing, S.
We prove the existence of the old and metal-rich moving group HR 1614. This is done using the new Hipparcos parallaxes in combination with metallicities derived from Strömgren photometry, supported by dynamical simulations of the evolution of old moving groups in the galactic potential. A new selection criterion for this moving group is presented …
Nitrogen isotope fractionation and its consequence for Titan's atmospheric evolution
Lammer, H.; Owen, T.; Molina-Cuberos, G. J. +2 more
The first determination of the 15N/ 14N ratio in Titan's atmosphere comes from Earth-based millimetric wavelength spectroscopic observations of HC 15N/HC 14N. These measurements indicate that the bulk nitrogen is enriched in the heavy isotope 15N by about 4.5 times relative to the Earth value.…
Factors Related to the Origin of a Gradual Coronal Mass Ejection Associated with an Eruptive Prominence on 1998 June 21-22
Srivastava, Nandita; Inhester, Bernd; Hanaoka, Yoichiro +2 more
We present observations of a coronal mass ejection (CME) associated with an eruptive prominence during 1998 June 21-22 by LASCO (Large Angle Spectroscopic Coronagraph) aboard SOHO (Solar and Heliospheric Observatory). Various features in the three-part structured, white-light CME as observed by LASCO-C2 and C3 coronagraphs were compared with featu…
Faint Blue Objects on the Hubble Deep Field North and South as Possible Nearby Old Halo White Dwarfs
Minniti, D.; Méndez, R. A.
Using data derived from the deepest and finest angular resolution images of the universe yet acquired by astronomers at optical wavelengths, with the Hubble Space Telescope (HST) in two postage-stamp sections of the sky, plus simple geometrical and scaling arguments, we demonstrate that the faint blue population of point-source objects detected in…
The origin of silicate carbon stars: ISO/SWS observation of V778 Cygni
Waters, L. B. F. M.; Dominik, C.; Yamamura, I. +2 more
The origin of silicate carbon stars has been a mystery ever since their discovery. We discuss here a full grating spectrum between 2.4 and 45 mu m of the silicate carbon star
Identification of Solar Acoustic Modes of Low Angular Degree and Low Radial Order
Kosovichev, A. G.; Henney, C. J.; García, R. A. +4 more
We present evidence for the detection of low radial order (n<10) acoustic modes of low angular degree, l=0-2, in the 759 day long Global Oscillations at Low Frequency and Michelson Doppler Imager time series. We used Random-Lag Singular Cross-Spectrum Analysis, which searches for simultaneous oscillatory components in two or more time series. W…
The puzzling theoretical predictions for the luminosity of clumping He burning stars
Weiss, A.; Prada Moroni, P. G.; Degl'Innocenti, S. +3 more
This paper deals with theoretical predictions for He burning models in a range of masses covering the so-called Red Giant Branch phase transition. Taking as a guideline the observational constraints given by Hipparcos parallaxes to the predicted luminosity of models originated from Red Giant progenitors with He core undergoing electron degeneracy,…
Hubble Space Telescope Observations of the Planetary Nebula K648 in the Globular Cluster M15
Livio, Mario; Bond, Howard E.; Alves, David R.
We have obtained observations of the planetary nebula K648 in the Galactic globular cluster M15 with the Hubble Space Telescope's Wide Field Planetary Camera 2, covering an interval of 7 days. The frames provide both time-sampled broadband photometry of the central star and high-resolution images of the nebula in the light of Hα, [O III], and [N I…
Hubble Space Telescope/WFPC2 and VLA Observations of the Ionized Gas in the Dwarf Starburst Galaxy NGC 4214
Walborn, Nolan R.; MacKenty, John W.; Maíz-Apellániz, Jesús +2 more
We present new Hα and [O III] λ5007 narrowband images of the starbursting dwarf galaxy NGC 4214, obtained with the Wide Field and Planetary Camera (WFPC2) on board the Hubble Space Telescope (HST), together with VLA observations of the same galaxy. The HST images resolve features down to physical scales of 2-5 pc, revealing several young (<10 M…
The Spectroscopic and Astrometric Parallaxes of Three Dwarf Novae: The Nature of the Secondary Stars of U Geminorum, SS Aurigae, and SS Cygni
Harrison, Thomas E.; Szkody, Paula; Gilliland, Ronald L. +1 more
We compare the parallaxes of three dwarf novae obtained using the Fine Guidance Sensors on the Hubble Space Telescope with their ground-based infrared spectroscopic parallaxes to examine the nature of their secondary stars. We have used new optical spectroscopy of MK spectral-type standards to rework the spectroscopic parallaxes of the reference f…