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The Ionization Source in the Nucleus of M84
Nelson, C.; Green, R. F.; Kaiser, M. E. +9 more
We have obtained new Hubble Space Telescope observations of M84, a nearby massive elliptical galaxy whose nucleus contains a ~1.5×109 Msolar dark compact object, which presumably is a supermassive black hole. Our Space Telescope Imaging Spectrograph spectrum provides the first clear detection of emission lines in the blue (e.…
The Triple System HR 7272
Udry, S.; Griffin, R. F.; Tokovinin, A. A. +2 more
A combined spectroscopic-interferometric orbit is computed for the primary component of the visual binary star HR 7272 = ADS 12101. The orbital period is 3.55 years; semimajor axis 0.074 arcsec. Radial velocities of both components were determined by correlation techniques; their semi-amplitudes are 6.6 and 8.4 km/s. Because those amplitudes are s…
Comparative abundance analysis of the hot main sequence stars and their progeny in open cluster M 25
Korotin, S. A.; Andrievsky, S. M.; Kovtyukh, V. V. +2 more
Remarkable inconsistencies between elemental abundances in the main sequence stars and their progeny F-G supergiants are discussed. Comparative abundance analysis of the hot main sequence stars, the cepheid U Sgr and two cool supergiants belonging to young open cluster M 25 is performed. The detected disaccord in the abundances of carbon, oxygen a…
Radial Color Gradient and Main-Sequence Mass Segregation in M30 (NGC 7099)
Guhathakurta, Puragra; Howell, Justin H.; Tan, Amy
It has long been known that the post-core-collapse globular cluster M30 (NGC 7099) has a bluer-inward color gradient, and recent work suggests that the central deficiency of bright red giant stars does not fully account for this gradient. This study uses Hubble Space Telescope Wide Field Planetary Camera 2 images in the F439W and F555W bands, alon…
Galactic Cosmic Ray Observations at Different Heliospheric Latitudes
Heber, Bernd; Potgieter, Marius S.
The local interstellar spectra (LIS) of galactic cosmic rays at low energies cannot be determined from measurements made near Earth, because of strong solar modulation processes from the heliospheric boundary to the observer. Computations done in the seventies based on Parker's cosmic ray modulation theory taking into account diffusion, convection…
Experimental Study of External Occulters for the Large Angle and Spectrometric Coronagraph 2: LASCO-C2
Lamy, Philippe; Bout, Maurice; Maucherat, André +2 more
Lensing properties of 7 damped Lyalpha absorbing galaxy-QSO pairs
Surdej, J.; Smette, A.; Le Brun, V. +1 more
Le Brun et al. (1997) presented the first identifications of the galaxies giving rise to 7 intermediate redshift damped Lyalpha (DLA) absorption systems. Here, we study the gravitational lensing properties of these foreground galaxies based on their observed optical appearance and on the absence of any secondary lensed quasar image. We consider th…
Modeling the Photoionized Interface in Blister H II Regions
Hester, J. Jeff; Sankrit, Ravi
We present a grid of photoionization models for the emission from photoevaporative interfaces between the ionized gas and molecular cloud in blister H II regions. For the density profiles of the emitting gas in the models, we use a general power-law form calculated for photoionized, photoevaporative flows by Bertoldi. We find that the spatial emis…
Discovery of Millihertz ULTRAVIOLET Quasi-periodic Oscillations in Hercules X-1
Horne, Keith; Boyd, Patricia T.; Boroson, Bram +5 more
Observations of the ultraviolet continuum of the X-ray binary system Her X-1/HZ Herculis with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope (HST) show quasi-periodic oscillations (QPOs) at frequencies of 8+/-2 and 43+/-2 mHz, with rms amplitudes of 2% and 4% of the steady flux. Observations with the Keck Telescope confirm …
The Starburst-Interstellar Medium Interaction in NGC 1569. I. Location and Nature of HE II Sources UsingHubble Space Telescope WFPC2 Imagery
Dufour, Reginald J.; Buckalew, Brent A.; Walter, Donald K. +1 more
We present the detection of He II sources in the Im galaxy NGC 1569 from Hubble Space Telescope WFPC2 imagery. Of the 15 detections, seven were Wolf-Rayet stars, five were stellar clusters with associated He II emission, and three were sources of unknown origin. The detected Wolf-Rayet stars' colors and magnitudes are similar to those of Large Mag…