Engineering topics

Hopkins, J. L.

Publications and source records attributed to Hopkins, J. L..

7 records

NASA NTRS1985

Optical photometry of the 1982-1984 eclipse of Epsilon Aurigae

From slightly before the 1982-1984 eclipse of Epsilon Aurigae to the present observers from around the world have been making photoelectric photometry observations of this star system. Over 2000 UBV observations have been reported as well as observations in the R, I, J, H, K, L, M, N, and Q bandpasses plus the y, b, v, and u bandpasses. Twenty nine observers from 9 countries submitted photometry data to the campaign. The data have shown many interesting features of the star system including a Cepheid-like pulsation, flare activity, mid-eclipse brightening, post egress brightening, plus other strange activity.

Hopkins, J. L.↗

NASA NTRS1985

Astronomical research at the Hopkins Phoenix Observatory

After trying astrophotography and radio astronomy it was decided that the best way to do meaningful astronomical research at a small private observatory was by doing photoelectric photometry. Having the observatory located in the back yard of a private residence affors the luxury of observing any time the sky conditions permit. Also modest equipment is all that is needed to do accurate UBV photometry of stars 8th magnitude and brighter. Since beginning in 1980 the Hopkins Phoenix Observatory has published papers on several RS CVn star systems, 31 Cygni, 22 Vul, 18 Tau Per, and has followed the 1982-1984 eclipse of Epsilon Aurigae from its start to the present with over 1000 UBV measurements. In addition the Hopkins Phoenix Observatory has developed several pieces of photometry equipment including the HPO PEPH-101 photometer head and photon counting electronics.

Hopkins, J. L.↗

NASA NTRS1985

The August 1984 eclipse of 22 Vulpeculae

Observations are reported of the newly discovered eclipsing binary 22 Vul (G3 IB-II+B9), in and around the 1984 eclipse. IUE satellite and ground-based photometric observations are included. The depth of total eclipse of the hot component was 0.05 mag in the V band, 0.14 in B, and 0.35 in U. Time of mideclipse is now established at JD1445942.3 (1984 August 29.8) plus-or-minus 0.2 day, with an eclipse duration of 9.8 plus-or-minus 0.2 days. The period is 249.115 plus-or-minus 0.024 days. The ingress and egress phases, lasting only about one day in visible light, last a week or more at some UV wavelengths and are not symmetrical.

Parsons, S. B.↗

NASA NTRS1984

The 1982 eclipse of 31 Cygni

UBV photometry and optical-UV spectroscopy of the primary eclipse of the long period Zeta Aurigae-like system 31 Cygni are reported. The precise timings made possible by the photometry imply that the spectral features could be due to an accretion shock associated with a hot star embedded in an extended chromosphere surrounding the red supergiant. The data also suggest an extended clumpy structure to the atmosphere of the late-type supergiant in the binary.

Hopkins, J. L.↗

NASA NTRS1983

The photometric period of 39 AY Ceti

A photometric period of 77.65 days is derived for 39 AY Ceti through a comparison of photoelectric photometry obtained in 1971 and 1972 with that obtained in the periods 1980-1981 and 1981-1982. JD 2444636.0 is an epoch of minimum light, and the full amplitude is found to have been as large as 0.18 mag in V. It is noted that the mean light level has dropped by almost 0.2 mag over the last decade. The present binary star is also noteworthy in light of the recently discovered white dwarf secondary component, and because radial velocity measurements indicate an eccentricity as large as 0.1 and an orbital period which, at 57.1 days, differs considerably from the photometric period presented.

Hopkins, J. L.↗

NASA NTRS1983

Five years of photometry of Sigma Geminorum

Thirteen observatories have collaborated in obtaining five years of photoelectric photometry for the bright, K1 III RS CVn binary Sigma Geminorum. Except for one year, the light curve has exhibited two minima which are separated by approximately half a cycle. At the 1977.2 epoch of discovery one minimum was shallower, but as of 1982.2 they have become comparable in depth. During the 1979-80 season, the light curve changed shape rapidly, with the shallower minimum becoming as deep as the other within a period of no more than 80 days. The overall brightness range during the five years in V has been 4.13-4.29 mag, and it is found that the times of both minima can be fit with a photometric period of 19.423 days.

Fried, R. E.↗

NASA NTRS1983

Five years of photometry of Lambda Andromedae

Photoelectric photometry of the bright variable RS CVn-type binary Lambda And obtained in 1977-78 and 1980-81 is presented and used, together with earlier photometry, to derive the photometric period and discuss the changing shape of the light curve. The best ephemeris for times of minimum light is 2443829.2 + 53.95 d E. Because times of minimum and maximum extending back to those of Calder in 1933-37 can be phased together properly, the principal dark region must have maintained its identity for almost 50 yr. Over the last five years the brightness range has been between 3.70 and 4.05 m. During 1980-81 shallow secondary minima developed at phases where maxima occurred in previous years. Lambda And remains the only well-established case of nonsynchronous rotation among the known RS CVn variables.

Boyd, R. W.↗