NBC News Scripts
WBAP-TV (Television station : Fort Worth, Tex.)
1954-12-31
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13 records were found.
By exploiting Far Ultraviolet Spectroscopic Explorer (FUSE) satellite time-series data, we have probed the relation between accretion disc geometry and bipolar outflow in the low-inclination, nova-like cataclysmic variable (CV) V592 Cas. Our results show that the outflow is strictly modulated on the orbital period and not on the (negative or positive) superhump periods of this system. This implies that the precession of either the disc eccentricity or its tilt is not directly affecting the structure and global dynamics of the outflow. The principal variability in the ultraviolet resonance lines is characterized by Doppler shifts of the entire blueward absorption troughs, in concert for a range of low- and high-ionization cases. The repetitive behaviour is asymmetric and highly non-sinusoidal over the orbital cycle of the system. The di...
We present results from time-series optical spectroscopy of the low-inclination, nova-like cataclysmic variable, V592 Cas. The data span the wavelength range from similar to4000 to 5000 Angstrom. and include Balmer lines (Hbeta to Hepsilon) as well as He I and He II. The Balmer lines are generally characterized by shallow absorption troughs with superimposed narrower central emission components. The absorption troughs are variable on time-scales of at least similar to20 min, but the fluctuations are asymmetric such that they are more dominant on the blueward side of the profile out to similar to-2000 km s(-1). Fourier analysis reveals modulation periods for emission radial velocities and absorption changes of similar to0.114 and 0.103 d; we support earlier suggestions that the latter is likely to be 1-day alias of the former, which is ...
We present Far Ultraviolet Spectroscopic Explorer (FUSE) satellite time-series data of the low-inclination, nova-like cataclysmic variable RW Sex. The data span the wavelength range between similar to905 and 1188 Angstrom, which contains the resonance lines of C III, N III, S IV, P V, S VI and O VI. All these spectral lines are present in the form of blueshifted absorption components, with no evidence for the lines redward of rest velocity; the FUSE data probe the fast disc-wind of RW Sex. The time-variable nature of these features is established. Substantial line profile variability is observed, confined between similar to-1000 and 0 km s(-1), and modulated on the orbital period of the system (similar to0.245 d). The fundamental characteristics of the temporal behaviour are very similar between the low and high ionization lines. The w...
We present a compilation of spectroscopic observations of the sgB[e] star CI Cam, the optical counterpart of XTE J0421+560. This includes data from before, during, and after its 1998 outburst, with quantitative results spanning 37 years. The object shows a rich emission line spectrum originating from circumstellar material, rendering it difficult to determine the nature of either star involved or the cause of the outburst. We collate all available pre-outburst data to determine the state of the system before this occurred and provide a baseline for comparison with outburst and post-outburst data. During the outburst all lines become stronger, and hydrogen and helium lines become significantly broader and asymmetric. After the outburst, spectral changes persist for at least three years, with Fe II and [N II] lines still a factor of simi...
We present far-infrared and submillimetre spectra of three carbon-rich evolved objects, AFGL 2688, AFGL 618 and NGC 7027. The spectra were obtained with the SPIRE Fourier-transform spectrometer on board the Herschel Space Observatory, and cover wavelengths from 195-670 mu m, a region of the electromagnetic spectrum hitherto difficult to study in detail. The far infrared spectra of these objects are rich and complex, and we measure over 150 lines in each object. Lines due to 18 different species are detected. We determine physical conditions from observations of the rotational lines of several molecules, and present initial large velocity gradient models for AFGL 618. We detect water in AFGL 2688 for the first time, and confirm its presence in AFGL 618 in both ortho and para forms. In addition, we report the detection of the J = 1-0 lin...
We present far-infrared and submillimetre spectra of three carbon-rich evolved objects, AFGL 2688, AFGL 618 and NGC 7027. The spectra were obtained with the SPIRE Fourier-transform spectrometer on board the Herschel Space Observatory, and cover wavelengths from 195-670 ìm, a region of the electromagnetic spectrum hitherto difficult to study in detail. The far infrared spectra of these objects are rich and complex, and we measure over 150 lines in each object. Lines due to 18 different species are detected. We determine physical conditions from observations of the rotational lines of several molecules, and present initial large velocity gradient models for AFGL 618. We detect water in AFGL 2688 for the first time, and confirm its presence in AFGL 618 in both ortho and para forms. In addition, we report the detection of the J = 1-0 line ...
With a luminosity > 10(5) L-circle dot and a mass-loss rate of similar to 2 x 10(-4) M-circle dot yr(-1), the red supergiant VY CMa truly is a spectacular object. Because of its extreme evolutionary state, it could explode as supernova any time. Studying its circumstellar material, into which the supernova blast will run, provides interesting constraints on supernova explosions and on the rich chemistry taking place in such complex circumstellar envelopes. We have obtained spectroscopy of VY CMa over the full wavelength range offered by the PACS and SPIRE instruments of Herschel, i.e. 55-672 micron. The observations show the spectral fingerprints of more than 900 spectral lines, of which more than half belong to water. In total, we have identified 13 different molecules and some of their isotopologues. A first analysis shows that water...
The interstellar medium is enriched primarily by matter ejected from evolved low and intermediate mass stars. The outflows from these stars create a circumstellar envelope in which a rich gas-phase and dust-nucleation chemistry takes place. We observed the nearest carbon-rich evolved star, IRC+10216, using the PACS (55-210 {\mu}m) and SPIRE (194-672 {\mu}m) spectrometers on board Herschel. We find several tens of lines from SiS and SiO, including lines from the v=1 vibrational level. For SiS these transitions range up to J=124-123, corresponding to energies around 6700K, while the highest detectable transition is J=90-89 for SiO, which corresponds to an energy around 8400K. Both species trace the dust formation zone of IRC+10216, and the broad energy ranges involved in their detected transitions permit us to derive the physical propert...
