Engineering topics

Barbour, M. S.

Publications and source records attributed to Barbour, M. S..

8 records

NASA NTRS1983

X Persei - Optical polarization variation on the 580 day binary-like period

Observations of periodicities in the optical polarization of the weak X-ray source X Persei are reported. Polarization was measured in the V band 400 times over the course of 356 nights during 1977-1982. The Q and U Stokes parameters derived from the measurements show a definite variability with a typical amplitude of 0.1%, which is strongest at periods greater than 100 days. In particular, a strong peak is observed with a period of 297 days, consistent with the second-harmonic component of the known 580-day radial velocity cycle. A component with 590-day periodicity is not ruled out by the observations, although it was not detected. Observations imply the 580-day period to be an effect of orbital or rotational processes, with the corotating scattering body either close to the light source or very large in extent, and a system inclination close to 80 deg.

Kemp, J. C.↗

NASA NTRS1981

A photoelastic-modulator polarimeter at Pine Mountain Observatory

The use of photoelastic polarimeters in astronomy is briefly reviewed, and a visible and near-UV photoelastic modulation polarimeter is described which has been in continuous service on the 61-cm telescope of Pine Mountain Observatory for 6 years. The polarimeter is used primarily for linear polarization measurements, but is easily adaptable to circular polarimetry. The instrument has produced data at a sensitivity level of 0.01%, with long-term absolute reproducibility.

Kemp, J. C.↗

NASA NTRS1981

Discovery of phase-locked variable polarization in an RS Canum Venaticorum-like star, HR 5110

Using measurements on 79 nights in 1980 January-August, it is established that the polarization in the ultraviolet (U band) varies synchronously on the known binary period of 2.6132 days, with a peak-to-peak amplitude of 0.03%. The pattern is mainly second harmonic in character, as typical of binary star examples such as Algol and Upsilon Her. Reflection by the cooler star, by a plasma concentration, or both, is suggested. The scale of the polarization seems to be consistent with Rayleigh scattering by neutral hydrogen on the cooler star, and a roughly lambda to the -4th wavelength dependence should be searched for. The QU curve suggests a sizeable inclination for the system, of about 45 deg, but this is preliminary. Separately, a possible weak periodicity might be present on a subsidiary period, conceivably related to a rotating star spot.

Barbour, M. S.↗

NASA NTRS1981

The 1980 June X-ray high state of Cygnus X-1 - Optical changes

UBV photometry of Cygnus X-1 is reported from before, during, and after the 1980 June X-ray high state discovered by the Hakucho satellite. A darkening was recorded around orbital phase 0.25, also near phase 0.0, which persisted for over a month after the X-ray episode. The brightness around phase 0.75 remained normal. Light curves from preceding years are compared. Preliminary mention is also made of polarization changes during the high state.

Kemp, J. C.↗

NASA NTRS1981

Algol - A further study of the optical polarization

Results of a study of the phase-locked optical polarization of the Algol triple star system are presented. Polarimetry was obtained in the B filter during 75 nights from 1979 to 1980, and results were folded on the AB orbital period for the equatorial Stokes parameters Q and U. As expected for a nearly edge-on system, the polarization variations are predominantly in one direction of the Stokes-vector plane, and are mainly second-harmonic in character. The variable polarization indicates an eigendirection for the AB system at an angle of 137 + or - 4 deg, and a projected major axis of the third star at 133 + or - 3 deg with respect to the AB system. Considerations of the lowest-order theories of polarizing mechanisms, including limb polarization and reflection, indicate that the AB and AB-C orbital planes are almost normal to each other, rather than coplanar. An angular splitting in the Q-U curve between the two quadrature phases 0.25 and 0.75 is also found which can be explained by centrifugal flattening of the secondary's Roche lobe, or reflection from an optically thick, flattened gas cloud near the L1 point.

Kemp, J. C.↗

NASA NTRS1981

Optical photometry of SS 433 - 200 nights of data 1979-1980

Results from over 200 nights of optical photoelectric photometry of SS 433 during the period July 1979-October 1980 are presented. The data, taken in unfiltered light, the V band, an interference filter band centered on stationary H-alpha and a far-red band, provide evidence for an underlying 164-day light variation of peak-to-peak amplitudes 0.50 magnitude in V and 0.7 magnitude at 6567 A, and a binary-like variation with period 13.074 days and peak-to-peak amplitudes 0.50 and 0.60 magnitudes, respectively. The 13-day light curves are found to change slightly as a function of phase in the 164-day cycle, while seemingly erratic light fluctuations of up to 1 magnitude in 1 day and about 2 magnitudes in 3-4 days are imposed on both cyclic variations. It is noted that a conventional close-binary model is incapable of accounting for all the observed features, and alternatives involving some sort of luminous, rapidly changing extended low-mass envelope or screen in the binary system must be sought.

Kemp, J. C.↗

NASA NTRS1980

SS 433 - Intensive 4 month light curves

Photometry covering 100 nights during 1979 July-November is reported, in an unfiltered band (effectively 5200-8000 A), in a V band, and with a few measures in B. Correlation with the 13 day period of Crampton, Cowley, and Hutchings is found in the form of a double-peaked light curve. A more tentative connection with the 164 day 'precession' period suggested by a broad light minimum near a critical phase in the long cycle is found.

Kemp, J. C.↗

NASA NTRS1980

New results from optical polarimetry of Saturn's rings

Linear polarimetry of Saturn's rings, obtained through the period of the 1979 opposition, is presented. The polarisation clearly correlates in direction with the plane containing the Sun, planet and Earth, but not the ring plane. The results are consistent with local scattering on the surface of individual ring bodies, covered with frost

Johnson, P. E.↗