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Chandra Observations of Markarian 273: Unveiling the Central Active Galactic Nucleus and the Extended Hot Gas Halo
Xia, X. Y.; Xue, S. J.; Mao, S. +3 more
We report X-ray observations of the field containing the ultraluminous IRAS galaxy Mrk 273. The data were obtained using the Advanced CCD Imaging Spectrometer S3 instrument on board Chandra. The high-resolution X-ray image for the first time reveals a compact hard X-ray nucleus in Mrk 273. Its position is coincident with the northern nucleus ident…
Resolving subdwarf B stars in binaries by HST imaging
Heber, U.; Green, E. M.; Thejll, P. +2 more
The origin of subluminous B stars is still an unsolved problem in stellar evolution. Single star as well as close binary evolution scenarios have been invoked but until now have met with little success. We have carried out a small survey of spectroscopic binary candidates (19 systems consisting of an sdB star and late type companion) with the Plan…
The 7.5 Magnitude Limit Sample of Bright Short-Period Binary Stars. I. How Many Contact Binaries Are There?
Rucinski, Slavek M.
A sample of bright contact binary stars (W UMa type or EW, and related: with β Lyr light curves, EB, and ellipsoidal, ELL-in effect, all but the detached, EA) to the limit of Vmax=7.5 mag is deemed to include all discoverable short-period (P<1 day) binaries with photometric variation larger than about 0.05 mag. Of the 32 systems in t…
Cluster observations of the exterior cusp and its surrounding boundaries under northward IMF
Lundin, R.; Sauvaud, J. -A.; Escoubet, C. P. +18 more
We have studied in detail multi-spacecraft observations of the exterior cusp on 04 February 2001, during a steady northward Interplanetary Magnetic Field (IMF) interval. At a radial distance of 11 Re, Cluster encountered a well-bounded region where the magnetic field exhibited very low diamagnetic values and the ions displayed high levels of isotr…
A Far Ultraviolet Spectroscopic Explorer Survey of Late-Type Dwarf Stars
Ayres, Thomas R.; Redfield, Seth; Wood, Brian E. +5 more
We describe the 910-1180 Å spectra of seven late-type dwarf stars obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. The stars include Altair (A7 IV), Procyon (F5 IV-V), α Cen A (G2 V), AB Dor (K1 V), α Cen B (K2 V), ɛ Eri (K2 V), and AU Mic (M0 V). We present line identifications, fluxes, Doppler shifts, and widths. Dopple…
Galaxies with a Central Minimum in Stellar Luminosity Density
Filippenko, Alexei V.; Ho, Luis C.; van der Marel, Roeland P. +15 more
We used Hubble Space Telescope WFPC2 images to identify six early-type galaxies with surface brightness profiles that decrease inward over a limited range of radii near their centers. The inferred luminosity density profiles of these galaxies have local minima interior to their core break radii. NGC 3706 harbors a high surface brightness ring of s…
New Members of the Cluster Family in Nearby Lenticular Galaxies
Brodie, Jean P.; Larsen, Søren S.
Using spectra obtained with the Keck I Telescope, we have demonstrated conclusively that the faint (23<=V<=24 mag) and unusually extended objects we discovered in Hubble Space Telescope images of the lenticular galaxies NGC 1023 and NGC 3384 are star clusters associated with their respective galaxies. In the case of NGC 1023, we were further…
Evolution in the Far-Infrared Spectra of Low-Mass Young Embedded Sources
Giannini, Teresa; Nisini, Brunella; Lorenzetti, Dario
The far-infrared spectra (45-197 µm) of 28 low-luminosity young embedded objects have been studied in order to search for possible evolutive trends in the observed spectral features. The low-resolution spectra from 45 to 197 µm of 17 Class 0 and 11 Class I sources taken with the Long Wavelength Spectrometer (LWS) on board the Infrared …
Orbits of Four Very Massive Binaries in the R136 Cluster
Massey, Philip; Penny, Laura R.; Vukovich, Julia
We present radial velocity and photometry for four early-type, massive, double-lined spectroscopic binaries in the R136 cluster. Three of these systems are eclipsing, allowing orbital inclinations to be determined. One of these systems, R136-38 (O3 V+O6 V), has one of the highest masses ever measured for the primary, 57 Msolar. Comparis…
The Chandra Deep Field North Survey. X. X-Ray Emission from Very Red Objects
Hornschemeier, A. E.; Alexander, D. M.; Bauer, F. E. +4 more
The multiwavelength properties of very red objects [VROs; (I-K)>=4] are largely unknown since many of these sources are optically faint (I>=24) and undetected at most wavelengths. Here we provide constraints on the X-ray (0.5-8.0 keV) properties of VROs using the 1 Ms Chandra exposure of an 8.4‧×8.4‧ region within the Hawaii flanking-field a…