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Evolution of Population II stars
Caputo, Filippina
The current knowledge of the evolution of Population II stars, as observed in galactic halos and globular clusters, is outlined. The recent theoretical results provided by an improved physical understanding of the stars are reported, with a particular emphasis upon those stellar evolutionary phases which are the keystones of the interpretation of …
Globular Cluster Photometry with the Hubble Space Telescope. VII. Color Gradients and Blue Stragglers in the Central Region of M30 from Wide Field Planetary Camera 2 Observations
Schneider, Donald P.; Yanny, Brian; Bahcall, John N. +2 more
We present F555W (V), F439W (B), and F336W (U) photometry of 9507 stars in the central 2' of the dense, post-core-collapse cluster M30 (NGC 7099) derived from Hubble Space Telescope Wide Field Planetary Camera 2 images. These data are used to study the mix of stellar populations in the central region of the cluster. Forty-eight blue straggler star…
Comparison of Prominences in Hα and He II 304 Å
Wang, Haimin; Chae, Jongchul; Gurman, Joseph B. +1 more
In this letter, we bring attention to prominences which show different morphology in Hα and He ii 304 Å, as observed simultaneously by BBSO and EIT on board SOHO. Those two lines have been thought to represent similar chromospheric structures although they are formed at significantly different temperatures. We give two examples representing two ki…
Evidence for multiple ejecta: April 7-11, 1997, ISTP Sun-Earth connection event
Reiner, M.; Delaboudinière, J. -P.; Bougeret, J. -L. +12 more
Evidence is presented that the enhanced geomagnetic activity, on April 10-11, 1997, was caused by one of two ejecta that left the Sun at ≈ 14 UT on April 7. This ejecta was not directly detected at the Earth. The evidence for this interpretation is based on WIND spacecraft observations in the solar wind (SW). It is consistent with: (i) measured ve…
Ultraviolet Absorption Lines from High-Velocity Gas in the VELA Supernova Remnant: New Insights from Space Telescope Imaging Spectrograph Echelle Observations of HD 72089
Kaiser, Mary Elizabeth; Tripp, Todd M.; Jenkins, Edward B. +12 more
The star HD 72089 is located behind the Vela supernova remnant and shows a complex array of high- and low-velocity interstellar absorption features arising from shocked clouds. A spectrum of this star was recorded over the wavelength range 1196.4-1397.2 Å at a resolving power of λ/Δλ = 110,000 and a signal-to-noise ratio of 32 by the Space Telesco…
Very low frequency waves in the heliosphere: Ulysses observations
Balogh, A.; McComas, D. J.; Forsyth, R. J. +5 more
An overall profile of plasma wave activity in a frequency range of 0.2 to 448 Hz in the solar wind is presented using 6 years of Ulysses data which cover a large range of heliographic latitudes (0° to +/-80°) at distances from 1 to 5 AU from the Sun. The spacecraft has continuously observed wave activity with peak power below the local electron cy…
The nature of some doubtful open clusters as revealed by HIPPARCOS
Baumgardt, H.
We discuss the nature of some galactic open clusters by using proper motions and parallaxes from the Hipparcos and ACT catalogues. We show that the clusters Collinder 399, Upgren 1, NGC 1252 and Melotte 227 do not exist. Collinder 132 is found to be mainly composed out of members of an OB association, but there may be a star cluster present in thi…
High-Temperature Lines in SUMER Spectra Recorded Above a Bright Solar Active Region
Wilhelm, K.; Curdt, W.; Schühle, U. +3 more
We identify spectral lines emitted by solar abundant elements due primarily to transitions within the 2s22pk and 3s23pk (where k = 1, 5) ground configurations of ions that are formed in ionization equilibrium between 2 × 106 and 8 × 106 K. The transitions were identified in spectra …
Radio jet interactions in the radio galaxy PKS 2152-699
di Serego Alighieri, S.; Fosbury, R. A. E.; Morganti, R. +3 more
We present radio observations of the radio galaxy PKS 2152-699 obtained with the Australia Telescope Compact Array. The much higher resolution and signal-to-noise ratio of the new radio maps reveal the presence of a bright radio component about 10 arcsec north-east of the nucleus. This lies close to the highly ionized cloud previously studied in t…
Atomic Carbon in ARP 220
Gerin, Maryvonne; Phillips, Thomas G.
We present detections of the 3P1-3P0 fine-structure line of neutral carbon and of the J=3-2 rotational line of carbon monoxide in the ultraluminous infrared galaxy Arp 220, obtained at the Caltech Submillimeter Observatory. C I emission in Arp 220 is found to be at the expected level in relation to the s…