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A Combined Hipparcos and Multichannel Astrometric Photometer Study of the Proposed Planetary System of ρ Coronae Borealis
Han, Inwoo; Gatewood, George; Black, David C.
Hipparcos and Multichannel Astrometric Photometer (MAP) observations of ρ Coronae Borealis independently display astrometric motion at the period of the proposed ``extrasolar planetary'' companion to the star. Individual least-squares fits to each astrometric data set yield independent estimates of the semimajor axis, inclination, and node angle t…
The Distance of the Large Magellanic Cloud Cluster NGC 1866
Walker, A. R.; Hill, V.; Castellani, V. +3 more
Hubble Space Telescope V, I photometry of stars in the Large Magellanic Cloud cluster NGC 1866 shows a well-defined cluster main sequence (MS) down to V=25 mag, with little contamination from field or foreground stars. We use the MS fitting procedure to link the distance of NGC 1866 to the Hipparcos determination of the distance for the Hyades MS …
Identification of Fe II Emission Lines in FUSE Stellar Spectra
Harper, Graham M.; Brown, Alexander; Linsky, Jeffrey L. +2 more
We identify two complexes of Fe II emission lines in far-ultraviolet spectra of the stars α TrA and HD 104237. Using spectra from both the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST), we show that these emission lines, which represent the majority of pr…
Multifrequency Analysis of the New Wide-Separation Gravitational Lens Candidate RX J0921+4529
Peng, C. Y.; Keeton, C. R.; Kochanek, C. S. +9 more
We report the discovery of a new two-image gravitational lens candidate. The system RX J0921+4529 contains two zs=1.66 quasars separated by 6.93" with an H-band magnitude difference of Δm=1.39. The HST NIC2 H-band images reveal an H=18.2 spiral galaxy between the quasar images, which is probably a member of a zl=0.32 X-ray cl…
Chandra Detection of X-Ray Absorption Associated with a Damped Lyα System
Elvis, Martin; Bechtold, Jill; Siemiginowska, Aneta +2 more
We have observed three quasars, PKS 1127-145, Q1331+171, and Q0054+144, with the ACIS-S aboard the Chandra X-Ray Observatory in order to measure soft X-ray absorption associated with intervening 21 cm and damped Lyα absorbers. For PKS 1127-145, we detect absorption that, if associated with an intervening zabs=0.312 absorber, implies a m…
The Obscuring Starburst of NGC 6221 and Implications for the Hard X-Ray Background
Storchi-Bergmann, T.; Heckman, T. M.; Levenson, N. A. +2 more
We present NGC 6221 as a case study of ``X-ray-loud composite galaxies,'' which appear similar to starbursts at optical wavelengths and resemble traditional active galactic nuclei in X-rays. The net optical spectrum of NGC 6221 is properly characterized as a starburst galaxy, but in X-rays, NGC 6221 is similar to Seyfert 1 galaxies, exhibiting a p…
Intensity Ratios between the 2s2 1S0-2s2p 3P1 and 2s2p 1P1-2p2 1D2 Transitions in Be-like Ions as Electron Temperature Indicators for Solar Upper Atmosphere Plasmas
Landi, E.; Doschek, G. A.; Feldman, U. +1 more
We investigate the relative intensities of the two moderately bright Be-like 2s2 1S0-2s2p 3P1 and 2s2p 1P1-2p2 1D2 lines as a function of electron temperature. We show that the intensity ratios of the lines in the beryllium isoelectronic s…
Mg II Absorber Number Density at z~=0.05: Implications for ΩDLA Evolution
Churchill, Christopher W.
An unbiased sample of 147 quasar/active galactic nuclei spectra, obtained with the Faint Object Spectrograph on board the Hubble Space Telescope, has been searched for intervening Mg II λλ2796, 2803 absorbers over the redshift range 0<z<=0.15. The total redshift path searched is 18.8, with the survey being 80% complete to a 5 σ rest-frame eq…
The Stellar Content of NGC 6789, A Blue Compact Dwarf Galaxy in the Local Void
Greggio, Laura; Hopp, Ulrich; Schulte-Ladbeck, Regina E. +2 more
We find that NGC 6789 is the most nearby example of a blue compact dwarf galaxy known to date. With the help of the Wide Field Planetary Camera 2 aboard the Hubble Space Telescope, we resolve NGC 6789 into over 15,000 point sources in the V and I bands. The young stars of NGC 6789 are found exclusively near the center of the galaxy. The red giant …
Dual Flows and Oscillations in the Sunspot Transition Region
Wilhelm, K.; Kjeldseth-Moe, O.; Brynildsen, N. +1 more
New knowledge about sunspot transition region lines that deviate significantly from a Gaussian shape are presented. Attention is given to ``multiple flows,'' a line profile phenomenon in which two or more distinct velocities are observed within the same spatial resolution element. We observe line profiles that are well represented by two Gaussian …