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Mode Identification of Pulsating White Dwarfs Using the Hubble Space Telescope
Kepler, S. O.; Clemens, J. C.; Jiang, X. J. +3 more
We have obtained time-resolved ultraviolet spectroscopy for the pulsating DAV stars G226-29 and G185-32 and for the pulsating DBV star PG 1351+489 with the Hubble Space Telescope Faint Object Spectrograph to compare the ultraviolet to the optical pulsation amplitude and determine the pulsation indices. We find that for essentially all observed pul…
Infrared Spectroscopy of Molecular Supernova Remnants
Reach, William T.; Rho, Jeonghee
We present Infrared Space Observatory spectroscopy of sites in the supernova remnants W28, W44, and 3C 391, where blast waves are impacting molecular clouds. The complete wavelength range from 42 to 188 µm was observed with the Long Wavelength Spectrometer, as well as narrow ranges centered on 4.695, 9.665, 25.98, and 34.82 µm with the…
Keck Mid-Infrared Imaging of QSO 2237+0305
Agol, Eric; Jones, Barbara; Blaes, Omer
Using the Long Wavelength Spectrometer on Keck, we have imaged the gravitationally lensed radio-quiet quasi-stellar object QSO 2237+0305 at 8.9 and 11.7 µm for the first time. The mid-IR flux ratios are inconsistent with the optical flux ratios but agree with the radio flux ratios and with some published gravitational lens models. These flux…
SN 1987A's Circumstellar Envelope. II. Kinematics of the Three Rings and the Diffuse Nebula
Crotts, Arlin P. S.; Heathcote, Stephen R.
We present several different measurements of the velocities of structures within the circumstellar envelope of SN 1987A, including the inner, equatorial ring (ER), the outer rings (ORs), and the diffuse nebulosity at radii <~5 pc, based on CTIO 4 m and Hubble Space Telescope (HST) data. A comparison of STIS and WFPC2 [N II] λ6583 loci for the r…
O-bearing Molecules in Carbon-rich Proto-Planetary Objects
Cernicharo, J.; Herpin, F.
We present Infrared Space Observatory long-wavelength spectrometer observations of the proto-planetary nebula CRL 618, a star evolving very fast toward the planetary nebula stage. In addition to the lines of 12CO, 13CO, HCN, and HNC, we report on the detection of H2O and OH emission together with the fine-structure…
Chromospheric and Transition Region Internetwork Oscillations: A Signature of Upward-propagating Waves
Judge, P. G.; Hansteen, V. H.; Carlsson, M. +1 more
We analyze spectral time series obtained on 1997 April 25 with the SUMER instrument on SOHO. Line and continuum data near 1037 Å were acquired at a cadence of 16 s. This spectral region was chosen because it contains strong emission lines of C II, formed in the upper chromosphere/lower transition region; O VI, formed in the upper transition region…
Hubble Space Telescope Observations of the Large Magellanic Cloud Field around SN 1987A: Distance Determination with Red Clump and Tip of the Red Giant Branch Stars
Panagia, N.; Salaris, M.; Cassisi, S. +1 more
We have used Hubble Space Telescope (HST) WFPC2 multiband observations of a field around SN 1987A in the Large Magellanic Cloud to measure its distance from the Sun. The observations allowed us to carefully determine the interstellar extinction along the line of sight to a large number of stars and to measure the LMC distance by using two stellar …
Factors Related to the Origin of a Gradual Coronal Mass Ejection Associated with an Eruptive Prominence on 1998 June 21-22
Srivastava, Nandita; Inhester, Bernd; Hanaoka, Yoichiro +2 more
We present observations of a coronal mass ejection (CME) associated with an eruptive prominence during 1998 June 21-22 by LASCO (Large Angle Spectroscopic Coronagraph) aboard SOHO (Solar and Heliospheric Observatory). Various features in the three-part structured, white-light CME as observed by LASCO-C2 and C3 coronagraphs were compared with featu…
Faint Blue Objects on the Hubble Deep Field North and South as Possible Nearby Old Halo White Dwarfs
Minniti, D.; Méndez, R. A.
Using data derived from the deepest and finest angular resolution images of the universe yet acquired by astronomers at optical wavelengths, with the Hubble Space Telescope (HST) in two postage-stamp sections of the sky, plus simple geometrical and scaling arguments, we demonstrate that the faint blue population of point-source objects detected in…
Identification of Solar Acoustic Modes of Low Angular Degree and Low Radial Order
Kosovichev, A. G.; Henney, C. J.; García, R. A. +4 more
We present evidence for the detection of low radial order (n<10) acoustic modes of low angular degree, l=0-2, in the 759 day long Global Oscillations at Low Frequency and Michelson Doppler Imager time series. We used Random-Lag Singular Cross-Spectrum Analysis, which searches for simultaneous oscillatory components in two or more time series. W…