%R 1995PASP..107..307P
%T The Remarkable Eclipsing Asynchronous AM Herculis Binary RX J19402-1025
%A JOSEPH PATTERSON, DAVID R. SKILLMAN, JOHN THORSTENSEN, and COEL HELLIER
%B We report on two years of photometric and spectroscopic observation of the recently discovered AM Herculis star RX
J19402-1025. A sharp eclipse feature is present in the optical and X-ray light curves, repeating with a period of
12116.290 +- 0.003 s. The out-of-eclipse optical waveform contains approximately equal contributions from a signal at
the same period and another signal at 12150 s. As these signals drift in adn out of phase, the waveform of the light
curve changes in a complex but predictable manner. After one entire "super-cycle" of 50 days (the beat period between
the shorter periods), the light curve returns to its initial shape. We present long-term ephemerides for each of these
periods. \par It is highly probable that the eclipse period is the underlying orbital period, while the magnetic white
dwarf rotates with P = 12150 s. The eclipses appear to be eclipses of the white dwarf by the secondary star. But there
is probably also a small obsuring effect from cold gas surrounding the secondary, especially on the orbit-leading side
where the stream begins to fall towards the white dwarf. The latter hypothesis can account for several puzzling effects
in this star, as well as the tendency among most AM Her stars for the sharp emission-line components to slightly precede
the actual motion of the secondary. \par The presence of eclipses in an asynchronous Am Her star provides a marvelous
opportunity to study how changes in the orientation of magnetic field lines affect the accretion flows. Repeated
polarimetric light curves and high-resolution studies of the emission lines are now critical to exploit this potential.

%R 1995PASP..107..324H
%T Secondary Photometric Standards for Northern Nova-Like Cataclysmic
   Variables
%A A. A. HENDEN and R. K. HONEYCUTT
%B An average of 11 B, V secondary standards per field have been established for 58 cataclysmic variable stars, most of
which are nova-like variables. The standards are within a few arc minutes of the variable and are therefore well suited
for CCD photometry. The standards have brightnesses of V ~ 12-17 and have a typical accuracy per standard of +-0.02 mag.

%R 1995PASP..107..347B
%T Radio Emission from Type Ia Supernovae as a Test of Symbiotic Star
   Progenitor Systems
%A FRANCESCA R. BOFFI and DAVID BRANCH
%B The nature of the binary systems that are the immediate progenitors of Type Ia supernovae (SNe Ia) remains an open
question. We propose that deep, early searches for radio emission from relatively nearby SNe Ia could test the
possibility that the progenitor system consists of a white dwarf accreting from the wind of a red giant companion, ie.,
the symbiotic-star scenario. \par To illustrate the nature of the radio emission that might be expected, we predict the
radio light curve of SN 1986G in NGC 5128 (Centaurus A) by scaling it against the observed radio light curve of the Type
Ib SN 1983N in NGC 5236, a member of the same group of galaxies as NGC 5128. Although the denisty of the circumstellar
medium surrounding a symbiotic system is expected to be lower than that surrounding the Type II and Ib/c supernovae from
which radio emission has been detected, we find that relatively nearby SNe Ia such as SN 1986G, if they are coming from
symbiotic systems, should be detectable by deep early radio observations. The lower density of the circumstellar medium
leads to a weaker radio emission at a given time after explosion, but because the lower density reduces the free-free
absorption in the circumstellar medium, the radio light curve peaks at an earlier time. Consequently, the peak
luminosity does not depend strongly on the density of the circumstellar medium.

%R 1995PASP..107..351J
%T The Consistency of Stromgren-Beta Photometry for Northern Galactic
   Clusters. II. Praesepe and NGC 752
%A MICHAEL D. JONER and BENJAMIN J. TAYLOR
%B We have measured stars in Praesepe and NGC 752 in an internally-consistent Stromgren-Beta system. This system is
based in large part on published Hyades and Coma measurements. On comparing our Praesepe results to those of Crawford
and Barnes (1969, AJ, 74, 818), we find that the published color indices require corrections of 10-18 mmag to put them
on the Hyades-Coma system. This deduction applies for b-y, m_1 and Beta (but not c_1). For the NGC 752 data of Crawford
and Barnes (1970, AJ, 75, 946), we obtain a nonzero correction only for Beta. This correction is about 9 mmag. Also for
NGC 752, we find that the data of Twarog (1983, ApJ, 267, 207) require corrections ranging from 4-17 mmag, with all
Stromgren indices being affected and the largest correction being for m_1. These corrections resolve the long-standing
proglem posed by the differences between the Twarog and Crawford-Barnes data. For three published sources of V
magnitudes, we obtain offsets ranging from -14 to +27 mmag relative to our zero point, and we suggest that such offsets
are fairly common in published photometry for galactic clusters. For Praesepe, we use new and corrected data to test for
a c_1 anomaly and is indistinguishable from Coma in that regard.

%R 1995PASP..107..361C
%T The H II Regions of NGC 6822. IV. A Multivariate and Bivariate Analysis
%A JOHN COLLIER, PAUL HODGE, and ROBERT KENNICUTT, JR.
%B Using calibrated H-alpha CCD images, we have examined the structure of most of the known H II regions in the
irregular galaxy NGC 6822. To search for observaitonal clues to the reasons for the different morphologies, we have
examined correlations between several quantitative parameters (peak surface brightness, full-width half-maximum,
position, local H I intensity, total emission-line luminosity) and one qualitative one (morphological type). Although
many weak correlations exist among these data sets, the only strong bivariate correlation found was between luminosity
and size. Multivariate analysis (using principal components analysis) shows that there are no other strong correlations,
indicating that the variety displayed in the morphologies of these H II regions is the result of significant differences
in the physical parameters that govern them (mass, exciting star or stars, gas density and distribution, dust density
and distribution, dynamics, evolutionary state). No simple scaling of parameters can explain the observations.

%R 1995PASP..107..369M
%T Optical Identifications of Radio Galaxies from the B3VLA Survey
%A L. MAXFIELD, D. THOMPSON, S. DJORGOVSKI, M. VIGOTTI, and G. GRUEFF
%B We present new optical identifications of 16 radio galaxies from the B3VLA survey, as well as redshifts for 4 of
them. Finding charts, photometry, and offsets from nearby stars are given for all identifications. This is a
continuation of a long-term effort to obtain optical identifications and redshifts for complete subsamples of sources
from this survey.

%R 1995PASP..107..375O
%T The Keck Low-Resolution Imaging Spectrometer
%A J. B. OKE, J. G. COHEN, M. CARR, J. CROMER, A. DINGIZIAN, F. H. HARRIS, S. LABRECQUE, R. LUCINIO, W.
   SCHAAL, H. EPPS, and J. MILLER
%B The Low Resolution Imaging Spectrometer (LRIS) for the Cassegrain focus of the Keck 10-meter telescope on Mauna Kea
is described. It has an imaging mode so it can also be used for taking direct images. The field of view in both
spectrographic and imaging modes is 6 by 7.8 arcmin. It can be used with both conventional slits and custom-punched slit
masks. The optical quality of the spectrograph is good enough to take full advantage of the excellent imaging properties
of the telescope itself. The detector is a cooled back-illuminated Tektronics Inc. 2048 CCD which gives a sampling rate
of 4.685 pixels per arcsec. In the spectrographic mode the spectrograph has a maximum efficiency at the peak of the
grating blaze of 32-34% for the two lowest resolution gratings and 28% for the 1200 g/mm grating. This efficiency
includes the detector but not the telescope or the atmosphere.

%R 1995PASP..107..386M
%T High-Dynamic-Range Imaging Using a Deformable Mirror for Space
   Coronography
%A F. MALBET, J. W. YU, and M. SHAO
%B The need for high dynamic range imaging is crucial in many astronomical fields, such as extra-solar planet direct
detection, extra-galactic science and circumstellar imaging. Using a high quality coronograph, dynamic ranges of up to
10^5 have been achieved. However the ultimate limitations of coronographs do not come from their optical performances,
but from scattering due to imperfections in the optical surfaces of the collecting system. We propse to use a deformable
mirror to correct these imperfections and decrease the scattering level in local regions called "dark holes." Using this
technique will enable imaging of fields with dynamic ranges exceeding 10^8. We show that the dark-hole algorithm results
in a lower scattering level than simply minimizing the RMS figure error (maximum-strehl-ratio algorithm). The achievable
scattering level inside the dark-hole region will depend on the number of mirror actuators, the surface quality of the
telescope, the single-actuator influence function and the observing wavelength. We have simulated cases with a 37 X 37
deformable mirror using data from the Hubble Space Telescope optics without spherical aberrations and have demonstrated
dark holes with rectangular and annular shapes. We also present a preliminary concept of a monolithic, fully-integrated,
high-density deformable mirror whih can be used for this type of space application.

%R 1995PASP..107..399H
%T A Study of the Accuracy of Narrow Field Astrometry using Star Trails taken
   with the Cfht
%A INWOO HAN and GEORGE D. GATEWOOD
%B We extend the study of Han (1989a) to angles as small as 7 arcsec. To investigate the relation between the relative
motion and the separation of two stars in astrometric observations, we analyzed star trail plates taken with the CFHT by
Christian and Racine (1985). The result shows that on Mauna Kea the r.m.s. relative image motion for 1 sec of
integration time is given by sigma = 0.054 arcsec (theta/10 arcminute)^0.35, where theta is the separation between two
stars. The standard theory on atmospheric turbulence predicts that sigma is proportional to the 1/3th power of theta.
Our study shows that it is valid for the range of 7 arcsec < theta < 1100 arcsec. Han, using data taken with MAP
(Multichannel Astrometric Photometer, Gatewood 1987) of Allegheny Observatory of the University of Pittsburgh, showed
that in Pittsburgh sigma = 0.143 arcsec (theta/10arcminute)^0.34. This implies that the accuracy of very narrow field
astrometric observations at an excellent site may be more than 7 times higher than those of the currently most precise
astrometric programs.

%R 1995PASP..107..401A
%T Changing Sources of Published Information
%A HELMUT A. ABT
%B We looked at the types of referneces in papers published during the first month of 1972, 1982, and 1992 in the
Astrophysical Journal and Astronomy \& Astrophysics; also those published in the former journal during the first
half-years of 1952 and 1962. Some of the results are qualitatively predictable, such as the decrease (from 12% to 1%) in
references to observatory publications and inhouse technical reports, and the increase (from 1% to 10%) in references to
conference papers. But what are surprising are (1) the low (less than 3%) reference rate to preprints, showing that they
are not replacing journal papers (78%) as the primary source for reliable information, (2) the low (1%) reference rate
to theses, showing that they are not cited more frequently than average research papers, (3) the low (1%) reference rate
to review papers, showing that contrary to popular belief, very few people cite review papers instead of the original
research papers, and (4) the slightly decreasing reference rate (from 6% to 4%) to monographs, showing that despite
their greatly increased publication rate, they are gradually being quoted less for research use (as contrasted to
tutorial use).

%R 1995PASP..107..404G
%T Photometric and Morphological Analysis of UCM Galaxies
%A ALVARO G. VITORES GONZALEZ
%B A set of 212 objects of the UCM (Universidad Complutense de Madrid) survey of emission-line galaxies (ELGs), selected
from objective prism plates by the presence of H-alpha emission in their spectra, has been analysed in the Thuan \& Gunn
r filter. \par From CCD images of these UCM objects we have obtained the fundamental photometric parameters (apparent
and absolute magnitudes, linear diameters) and a set of characteristic morphological parameters extracted by surface
photometry techniques (parameters of bulb + disk descomposition, concentration indexes and mean surface brightnesses).
From this information, we have carried out intrinsecal statistical analysis of the data in the UCM sample and
extrinsecal comparison with other samples of galaxies. And specially, we have simultaneously applied, for the first time
in a sample of ELGs, five morphological criteria in order to obtain the Hubble type of these galaxies. \par As results
of this work we have obtained that the UCM survey is specially effective in the detection of ELGs smaller and less
luminous than normal spirals (the median values of the UCM sample are M_r = -20.6 and D_24 = 19.4 kpc) and that emission
arises fundamentally from the nuclear regions of the galaxies (only 22% of the sample show emitting knots outside the
nucleus). Morphologically, the UCM sample is dominated by late-type galaxies, with 66% being Sb or later. This result
confirms the expected tendency of the ELGs to be advanced type galaxies due to the higher mass fraction in gas available
in these systems. Specially, we have found 9 candidates to BCD (blue compact dwarf galaxy), five of them previously
unknown. We have also obtained that 10% of the UCM ELGs present typical parameters of S0 types, supporting the idea that
not all S0 galaxies are dead systems without prominent recent star formation, and that in the subsample of 16 UCM
galaxies showing obvious signs of interactions, 25% are S0 type galaxies. \par Finally, we have analysed the influence
of the medium in the occurence and nature of the ELGs. So, we have compared the presence of ELGs and their morphologies
in a subsample of galaxies in the Coma cluster respect to the subsample of field galaxies. Then, we have found that
whereas 34% of the field Zwicky galaxies are ELGs, this fraction is reduced to 9% in the Coma cluster, consistent with
the known efect that the fraction of galaxies that are ELGs is much lower in high-density cluster environments than in
the field due to the lower fraction of star forming gas available in these dense media. And respect to the morphology,
the objective prism technique permits to reveal, inside a cluster globally dominated by E-S0 type galaxies, a population
of ELGs with 71% being Sb type or later. \par In the future, we propose to study in others filters the subset of these
UCM galaxies specially peculiar, like the BCD galaxies (candidates to low metalicity objects), irregular and interacting
systems, and to continue investigating the conexion between the medium and the presence of ELGs and its influence on the
morphology of these galaxies.