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Infrared Space Observatory Long-Wavelength Spectrometer Spectroscopy of Star-forming Regions in M33
Stacey, G. J.; Higdon, S. J. U.; Higdon, J. L. +1 more
We present Infrared Space Observatory (ISO) Long-Wavelength Spectrometer (LWS) far-infrared (FIR) spectra of the nucleus and six giant H II regions in M33 (NGC 595, IC 142, NGC 592, NGC 604, NGC 588, and IC 133). The seven fine-structure lines observed in the FIR are used to model the H II and photodissociation regions (PDRs). There is no observed…
Hubble Space Telescope/NICMOS Near-Infrared Imaging of the Proto-Planetary Nebula OH 231.8+4.2
Hora, J. L.; Tielens, A. G. G. M.; Latter, W. B. +2 more
We present observations of the bipolar nebula OH 231.8+4.2, made with the Hubble Space Telescope (HST) NICMOS camera, in three wide filter bands (F205W, F160W, and F110W). The images have excellent dynamic range after removal of low-level instrumental artifacts. In the F205W filter (λ~2.04 µm), we achieve a peak/rms of greater than 8000 with…
The 2001 April Burst Activation of SGR 1900+14: Pulse Properties and Torque
Frontera, F.; Hurley, K.; Mereghetti, S. +10 more
We report on observations of SGR 1900+14 made with the Rossi X-Ray Timing Explorer (RXTE) and BeppoSAX during the 2001 April burst activation of the source. Using these data, we measure the spin-down torque on the star and confirm earlier findings that the torque and burst activity are not directly correlated. We compare the X-ray pulse profile to…
Star Formation and X-Ray Emission in Distant Star-Forming Galaxies
Cohen, Judith G.
About 45% of the point sources detected in the 2 Ms Chandra exposure of the Hubble Deep Field-North (HDF-N) can be matched with moderately bright galaxies with z<1.4 that have been studied by the Caltech Faint Galaxy Redshift Survey. Although the optical spectra of these galaxies appear normal, based on their X-ray properties ~20% of them appea…
Atomic Data and Emission-Line Intensities for Ca VII
Bhatia, A. K.; Landi, E.
In the present work we calculate energy levels, transition probabilities, and electron-ion collisional excitation rates for the 3s23p2, 3s3p3, and 3s23p3d configurations of the silicon-like ion Ca VII. The total number of intermediate coupling levels considered is 27. Collision strengths are calculated a…
Preferential Heating of Particles by H-Cyclotron Waves Generated by a Global Magnetohydrodynamic Mode in Solar Coronal Holes
Zhang, T. X.
Preferential heating of particles by H-cyclotron waves is investigated to explain the recent measurements of anisotropic heating of ions in solar coronal holes. First, the dispersion relation of H-cyclotron waves generated by a global MHD mode in the solar coronal hole is numerically studied. Then, heating of H, O+5, and Mg+9…
On the Origin of the High-Ionization Intermediate-Velocity Gas toward HD 14434
Sembach, Kenneth R.; Meyer, David M.; Lauroesch, James T. +2 more
We present Far-Ultraviolet Spectroscopic Explorer and Space Telescope Imaging Spectrograph observations of high-ionization interstellar absorption toward HD 14434 (l=135.1d, b=-3.8d d~2.3 kpc), an O5.5 V star in the Perseus OB1 association. Intermediate-velocity interstellar Si IV and C IV absorption is present at VLSR=-67 km s-1
Lens or Binary? Chandra Observations of the Wide-Separation Broad Absorption Line Quasar Pair UM 425
Green, Paul J.; Aldcroft, Thomas L.
We have obtained a 110 ks Chandra ACIS-S exposure of UM 425, a pair of QSOs at z=1.47 separated by 6.5", which show remarkably similar emission and broad absorption line (BAL) profiles in the optical/UV. Our 5000 count X-ray spectrum of UM 425A (the brighter component) is well fitted with a power law (photon spectral index Γ=2.0) partially covered…
Hubble Space Telescope Observations of Ultraviolet Oscillations in WZ Sagittae During the Decline from Outburst
Szkody, Paula; Sion, Edward M.; Godon, Patrick +4 more
We present a time series analysis of Hubble Space Telescope observations of WZ Sge obtained in 2001 September, October, November, and December as WZ Sge declined from its 2001 July superoutburst. Previous analysis of these data showed the temperature of the white dwarf decreased from ~29,000 to ~18,000 K. In this study we binned the spectra over w…
Early-Type Stars: Most Favorable Targets for Astrometrically Detectable Planets in the Habitable Zone
Fischer, Debra A.; Gould, Andrew; Ford, Eric B.
Early-type stars appear to be a difficult place to look for planets astrometrically. First, they are relatively heavy, and for fixed planetary mass the astrometric signal falls inversely as the stellar mass. Second, they are relatively rare (and so tend to be more distant), and for fixed orbital separation the astrometric signal falls inversely as…