Engineering topics
Publications and source records attributed to Spinrad, H..
The spectral synthesis of C2 Swan band sequence Delta V = -1 indicates the intensity of the forbidden green oxygen line of 5577.3 A to be about 3 to 5 percent of the 6300 A line. Therefore, it appears that the green line should be observable in high-resolution spectra of a bright comet. Festou and Feldman suggest red/green greater than or equal to 10 means a water parent origin.
The detection of a 'classical' QSO in a previously studied, distant rich cluster of visible galaxies is reported. The blue and red/IR spectra of the QSO are shown. The QSO occurs at a redshift essentially identical to that of the cluster 0016+16, colocated on the 0.01 of the plate which contains the cluster. The simplest explanation of this association is that the QSO is a member of the cluster. The consequences of the finding are discussed. The QSO-cluster association is further confirmation of the cosmological nature of QSO-cluster association is further confirmation of the cosmological nature of QSOs, and it suggests that QSOs do not necessarily avoid the environment of rich clusters. The fact that this QSO is not well centered adds credence to the suggestion that 3C345 and QSO 1641+3998 constitute an additional case of QSOs in high redshift cluster. The location of this QSO could make it a unique probe to study the physical state of the intracluster gas that is common in rich clusters.
The digital sky-subtracted spectra of nine cometary nuclei are used to measure the 6300, 6363-A Auroral red doublet of the O I forbidden line, and in view of the confinement of the cometary oxygen lines to their nuclear source, a small but variable correction for NH2 blending in different comets is made. For seven of the comets measured, and under the assumption of H2O's exclusive role as the oxygen parent, the average Q(H2O)/Q(O I) ratio is about 20. This is in excellent accord with theory, and it is conjectured that the O I production rate can be used to scale the total cometary volatile loss in even faint, distant comets. The data obtained are consistent with heliocentric production rates that vary as power laws, with n values of 2.0 for 'gassy' comets and nearer to 5.0 for dusty ones. The comets with the greatest volatile mass-loss rates all were found to have dusty spectra.
The variable spectrum of BE Ursae Majoris, which is similar to that of the cataclysmic variables (CVs), shows (1) an emission-line spectrum with the high-excitation CN 4650 A blend as the strongest optical feature, weaker H and He lines, and a strong Balmer jump, and (2) an absorption spectrum dominated by He. Although the object shows no evidence of photometric variability on either short or long time-scales, it has been shown by Kurochkin (1964, 1971) to have a 2.29-day, sinusoidal, 1.5-mag variation. The luminosity is dominated by a UV power-law component, though the 4000-10000 A continuum is flat. The hypothesis that this object is an active mass transfer binary is not supported by its photometric behavior, energy distribution and long period, despite the spectroscopic variability. Nevertheless, three components whose nature is not understood remain: (1) an ultraviolet source whose energy distribution is explainable neither by a uniform temperature primary star nor by an accretion disk; (2) a reprocessed component powered by the UV star; and (3) a component similar to a CV disk, producing the optically thick Balmer lines.
Digital spectroscopic scans of P/Comets Encke, Stephan-Oterma, and Gunn were obtained with a sky-subtraction scanner system. Quantiative fluxes for the cometary emission bands of CN, C3, C2, NH2, and the 'D OI red auroral line are presented for P/Encke. The most straight-forward and model-independent line flux to interpret is the lambda lambda 6300, 6364 forbidden oxygen doublet. After an NH2 blending correction, the oxygen production rate may be directly measured from the Lick small-aperture fluxes. The oxygen production rates increased rapidly with decreasing heliocentric distance for both P/Encke and P/Stephan-Oterma. A rough power-law exponent in r with n = approximately -2.5 describes the change in oxygen production for P/Encke. Compared to the water production rates inferred from IUE satellite spectra showing the lambda 3080 OH band, these oxygen production rates are consistently lower by a factor of 11. This implies a common origin for the two species; H2O is the likely sole OI ID parent.
Changes in the nebular structure, optical spectrum and stellar brightness of the faint star PV Cephei and the nebulosity associated with it are discussed. Iris photometry of the starlike object at the tip of the fan-shaped nebula reveals irregular variability of approximately 4 magnitudes in the red. Stellar spectra in the region 4300-6750 A taken from December 1976 to April 1980 are similar to the richest emission line spectra of T Tauri stars, while nebular spectra indicate a lack of spherical symmetry. Observations obtained in the infrared reveal a source offset by a few arcsec from the apex of the fan, which is identified with the illuminating star. Radial velocities of CO emission indicate that PV Cep is at the same distance as NGC 7023, and independent estimates lead to an estimated value of 500 pc. Such a distance corresponds to a bolometric luminosity approximately 100 times that of the sun. It is suggested that PV Cep is a T Tauri star that has recently broken through its circumstellar cocoon at a time when highly erratic variability and a strong stellar wind characterize the star.
The average spectral energy distribution for a sample of bright elliptical galaxies is presented in the range lambda lambda 2000 to 3200 A. Spectral synthesis indicates that elliptical galaxies are most likely older than 9 Gyrs. The ultraviolet flux is consistent with a population of red horizontal branch stars, as those present in metal rich globular clusters. Data for distant first ranked cluster galaxies show indications of spectral evolution.
The average spectral energy distribution for a sample of 3200 A. Spectral synthesis indicates that elliptical galaxies are most likely older than 9 Gyrs. The ultraviolet flux is consistent with a population of red horizontal branch stars, as those present in metal-rich globular clusters. Data for distant (Z approximately 1) first ranked cluster galaxies show indications of spectral evolution.
With the advent of mission planning for spacecraft encounters with comets in the 1980s, the lack of basic data on cometary nuclei has become quite apparent and a real problem. More effort is needed on all comets, with special attention given to probable space flight targets such as Tempel 2. The paper presents medium-spectral-resolution spectrophotometry of P/Tempel 2, made at heliocentric distances of 2.66 and 3.02 AU on two dates in 1978. It is shown that optical spectrophotometry of comet Tempel 2 near 3 AU heliocentric distance places strict limits on its activity, the modeled CN production rate having an upper limit of 6 times 10 to the 21st molecules per sec. The observations of P/Tempel 2 are compatible with a bare nucleus of 1.6 km radius (geometric albedo = 0.15) and somewhat redder than the sun.
Results are reported for image-tube-scanner and digicon observations of Feige 7, a faint blue star identified as a probable white dwarf. It is found that this star is a magnetic white dwarf showing a very rich spectrum with Zeeman subcomponents of both hydrogen and neutral helium as well as periodic spectrum and circular-polarization variations. A polarization period of 2.2 hr is computed, and a surface magnetic-field strength of about 18 MG is determined by matching features of the absorption spectrum to Zeeman components. It is suggested that the only reasonable explanation for the periodic variations in circular polarization is an oblique rotator with the spin axis approximately in the plane of the sky and tilted by about 24 deg to the magnetic axis. An effective temperature in the range from 20,000 to 25,000 K is estimated, an absolute magnitude of about 10.5 is derived, and the atmosphere is shown to be helium-dominated. The evolution of Feige 7 is discussed in terms of possible magnetic-field effects on atmospheric composition, rotation velocity (5.5 km/s for a radius of 7000 km), and the origin of white-dwarf magnetic fields.
Scans of Alpha Aql (A7 IV, V) and Alpha CMi (F5 IV-V) obtained with the Copernicus satellite spectrometer over the wavelength range from 2100 to 3200 A are presented along with a spectrum of the integrated solar disk over the same range procured during a calibrated rocket flight. About 1500 fairly strong absorption lines in the Alpha CMi spectrum between 2400 and 2961 A are identified by comparison with a solar atlas and by using a theoretical spectrum synthesized from a blanketed LTE model with an effective temperature of 6500 K and a surface gravity of 10,000 cm/sec per sec. The Mg II resonance doublet at 2795.528 and 2802.704 A is found to be present in all three stars together with a discontinuity at 2635 A due to Fe II, Fe I, Cr I, and Mn II. It is concluded that the Mg II resonance lines and the 2635-A continuum break would be the best spectral features for estimating the redshift of a galaxy observed at low resolution provided the redshift is not less than about 0.75.
We present a catalog of the important optical data for the radio sources in the Revised Third Cambridge Catalog. Optical positions, redshifts, magnitudes, and identifications have been included, as well as radio flux densities and spectral indices for the sample of 297 extragalactic 3CR sources. A bibliography of optical identifications, spectroscopy, and radio position/structure is also given. In addition to the literature compilation, we present new spectroscopic observations of 27 3CR radio galaxies, 25 of which do not have previously published redshifts.
A variety of data are presented concerning the spectrum, distance, temperature, and evolutionary state of the hot white dwarf HZ 43, the first extrasolar object to be detected in the EUV band. The data include spectrophotometry of the star and its red dwarf companion (HZ 43B), a trigonometric parallax for the star, its tangential velocity, and results of soft X-ray and EUV observations. The main conclusions are that: (1) the spectrum of HZ 43A is that of a hot DAwk star, (2) HZ 43B is a dM3.5e star, (3) the distance of the system is about 65 pc, (4) the tangential velocity is not atypical of white dwarfs, and (5) the stellar energy distribution of HZ 43A is well fitted by a black body with an effective temperature of approximately 110,000 K. Evolutionary implications of the existence of an object as hot as HZ 43A are briefly considered, and it is suggested that the progenitors of hot DA stars must include objects hotter than spectral type sdB, with logical possibilities being nuclei of planetary nebulae and sdO stars.
We have obtained medium-resolution spectra in the yellow of seven stars in the error box of the binary radio pulsar PSR 1913 + 16, using the image-tube scanner at the Lick 3-m telescope. None of the objects is spectroscopically abnormal and thus a strong candidate for membership in the system. The data are used to establish the extinction in the field, which is modest for this low galactic latitude. For three of the stars, limits of the order V exceeding 23 mag on optical pulsations with the frequency of the radio pulsar are derived. X-ray observations of the field have been obtained in the 2.5-7.5 keV band, using the UCL experiment aboard OAO Copernicus. No source is detected, with a 2 sigma upper limit on the time-averaged flux of 1.0 times 10 to the -10th power ergs per sq cm per sec.
Based on positional agreement, ultraviolet excess, and spectroscopic peculiarity, the identification of the X-ray source 3U 0614+09 with a faint blue star, previously suggested by Murdin et al. (1974) as a candidate, is established. Four days of X-ray observations at 1-3 A failed to show evidence for significant variability or eclipses. The possibility that this object may be very similar to Sco X-1, but at a distance of 4-8 kpc, is discussed.
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The possible association of an X-ray source with the galaxy IC 3576 was investigated in a program of optical observations of this galaxy. The observations show that patches and condensations belonging to the galaxy are distributed in a nonrandom, spiral fashion. This distinctive morphology corresponds to the dwarf spiral of the second type discussed by van den Bergh (1959). Radio observations are also considered, giving attention to a 21-cm emission due to neutral hydrogen in IC 3576. It is pointed out that the evidence at this time that the X-ray source in Virgo corresponds to IC 3576 is positional only.