%...Journal: PASP %...MainTag: '~}1 {\em M}_{sun}_and a lognormal form below, except possibly for early star formation conditions. The disk IMF for single objects has a characteristic mass around m_c_~0.08 {\em M}_{sun}_and a variance in logarithmic mass {sigma}~0.7, whereas the IMF for multiple systems has m_c_~0.2 {\em M}_{sun}_and {sigma}~0.6. The extension of the single MF into the brown dwarf regime is in good agreement with present estimates of L- and T-dwarf densities and yields a disk brown dwarf number density comparable to the stellar one, n_BD_~n_*_~0.1 pc^-3^. The IMF of young clusters is found to be consistent with the disk field IMF, providing the same correction for unresolved binaries, confirming the fact that young star clusters and disk field stars represent the same stellar population. Dynamical effects, yielding depletion of the lowest mass objects, are found to become consequential for ages {>~}130 Myr. The spheroid IMF relies on much less robust grounds. The large metallicity spread in the local subdwarf photometric sample, in particular, remains puzzling. Recent observations suggest that there is a continuous kinematic shear between the thick-disk population, present in local samples, and the genuine spheroid one. This enables us to derive only an upper limit for the spheroid mass density and IMF. Within all the uncertainties, the latter is found to be similar to the one derived for globular clusters and is well represented also by a lognormal form with a characteristic mass slightly larger than for the disk, m_c_~0.2-0.3 {\em M}_{sun}_, excluding a significant population of brown dwarfs in globular clusters and in the spheroid. The IMF characteristic of early star formation at large redshift remains undetermined, but different observational constraints suggest that it does not extend below ~1 {\em M}_{sun}_. These results suggest a characteristic mass for star formation that decreases with time, from conditions prevailing at large redshift to conditions characteristic of the spheroid (or thick disk) to present-day conditions. These conclusions, however, remain speculative, given the large uncertainties in the spheroid and early star IMF determinations.\par These IMFs allow a reasonably robust determination of the Galactic present-day and initial stellar and brown dwarf contents. They also have important galactic implications beyond the Milky Way in yielding more accurate mass-to-light ratio determinations. The mass-to-light ratios obtained with the disk and the spheroid IMF yield values 1.8-1.4 times smaller than for a Salpeter IMF, respectively, in agreement with various recent dynamical determinations. This general IMF determination is examined in the context of star formation theory. None of the theories based on a Jeans-type mechanism, where fragmentation is due only to gravity, can fulfill all the observational constraints on star formation and predict a large number of substellar objects. On the other hand, recent numerical simulations of compressible turbulence, in particular in super-Alfv\'enic conditions, seem to reproduce both qualitatively and quantitatively the stellar and substellar IMF and thus provide an appealing theoretical foundation. In this picture, star formation is induced by the dissipation of large-scale turbulence to smaller scales through radiative MHD shocks, producing filamentary structures. These shocks produce local nonequilibrium structures with large density contrasts, which collapse eventually in gravitationally bound objects under the combined influence of turbulence and gravity. The concept of a single Jeans mass is replaced by a distribution of local Jeans masses, representative of the lognormal probability density function of the turbulent gas. Objects below the mean thermal Jeans mass still have a possibility to collapse, although with a decreasing probability. %K Galaxies: Luminosity Function, Mass Function %K Invited Reviews %I (1) The page charges for this Review were partially covered by a generous gift from a {\em PASP} supporter. %R 2003PASP..115..796Y %F ori/PASPv115n809 %J-806 %T Finding Cool Subdwarfs Using a {\em V-J} Reduced Proper-Motion Diagram: Stellar Parameters for 91 Candidates. %A Yong, David %A Lambert, David L. %I Department of Astronomy, University of Texas, Austin, TX 78712; (tofu@astro.as.utexas.edu), (dll@astro.as.utexas.edu) %B We present the results of a search for cool subdwarfs for which our candidates were drawn from a {\em V-J} reduced proper-motion diagram constructed by Salim & Gould. Kinematic ({\em U}, {\em V}, and {\em W}) and self-consistent stellar parameters ({\em T}_eff_, log{\em g}, [Fe/H], and {xi}_t_) are derived for 91 candidate subdwarfs based on high-resolution spectra. The observed stars span 3900 K<{\em T}_eff_< 6200 K and -2.63<[Fe/H]<0.25 including only three giants (log{\em g}<4.0). Of the sample, 77 stars have MgH lines present in their spectra. With more than 56% of our candidate subdwarfs having [Fe/H]{<=}-1.5, we show that the {\em V-J} reduced proper-motion diagram readily identifies metal-poor stars. %K Stars: Abundances %K Stars: Fundamental Parameters %K Stars: Subdwarfs %R 2003PASP..115..807F %F ori/PASPv115n809 %J-810 %T Rotational Velocities of B, A, and Early-F Narrow-lined Stars. %A Fekel, Francis C.(1) %I Center of Excellence in Information Systems, Tennessee State University, 330 10th Avenue North, Nashville, TN 37203 %B Projected rotational velocities for 58 B, A, and early-F stars have been determined from high-resolution spectroscopic observations made at Kitt Peak National Observatory with the coud\'e feed telescope. All the stars are slowly rotating with vsini<60 km/s. Because of their low rotational velocities, 15 of the stars have been observed as prospective, early-type, radial velocity standards. %K Stars: Early-Type %K Stars: Rotation %I (1) Visiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatory, operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation. %R 2003PASP..115..811B %F ori/PASPv115n809 %J-818 %T RW Ursae Minoris (1956): An Evolving Postnova System. %A Bianchini, A.(1)(2) %A Tappert, C.(3) %A Canterna, R.(1) %A Tamburini, F.(2)(4) %A Osborne, H.(5) %A Cantrell, K.(1) %B From 1999-2002 photometric observations of the old nova RW UMi (1956), we systematically detect a dominant modulation with a period P_0_peaking in the range 1.7-2.4 hr. This period, on average, is about 45% longer than the previously suggested orbital period of ~1.42 hr. This could be due to the occasional presence of low-frequency quasi-periodic oscillations (QPOs) that can eventually dominate the light curve. Rather irregular QPOs, on the order of the orbital period, can be produced by vertical oscillations of the inner-disk region excited by the rotating magnetosphere of the white dwarf. Thus, RW UMi could be an intermediate polar system. Since we find that the luminosity of the postnova is decaying at a rate of ~0.02 mag/yr, we should observe some important changes in its photometric behavior in the future. %K accretion, accretion disks %K Stars: Novae, Cataclysmic Variables %K Stars: White Dwarfs %I (1) Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071. %I (2) Department of Astronomy, University of Padova, Italy. %I (3) Departamento de F\'isica, Universidad de Concepci\'on, Chile. %I (4) Institute of Cosmology and Gravitation, Portsmouth University, UK. %I (5) New Mexico State University, Las Cruces, NM. %R 2003PASP..115..819C %F ori/PASPv115n809 %J-824 %T A Reinvestigation of the Possible Metallicity Spread in NGC 3201. %A Covey, Kevin R. %A Wallerstein, George %A Gonzalez, Guillermo (1) %A Vanture, Andrew D.(2) %I Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195; (covey@astro.washington.edu), (wall@astro.washington.edu), (gonzog@iastate.edu), (avanture@evcc.ctc.edu) %A Suntzeff, Nicholas B. %I Cerro Tololo Inter-American Observatory/AURA, Inc., Casilla 603, La Serena, Chile; (nsuntzeff@noao.edu) %B We have conducted a reanalysis of the metallicity of six red giants within NGC 3201 on the basis of a new homogeneous set of spectra with resolution ~30,000. Iron line strengths and the MOOG software suite were used to derive metallicities based on spectroscopically and photometrically estimated values of {\em T}_eff_and log{\em g}. We cannot confirm the presence of a significant spread in metallicity within the cluster greater than about 0.3 dex nor any significant correlation between metallicity and temperature, as first suggested by Gonzalez & Wallerstein. We call attention to the possibility that differences in boundary temperature for stars of the same {\em T}_eff_may lead to apparent differences in metallicity. %K Galaxy: Globular Clusters: Individual: NGC Number: NGC 3201 %I (1) Current address: Department of Physics and Astronomy, Iowa State University, Ames, IA 50011-3160. %I (2) Regularly at Science Division, Everett Community College, 801 Wetmore Avenue, Everett, WA 98201. %R 2003PASP..115..825D %F ori/PASPv115n809 %J-836 %T Dynamical Stability of Earth-like Planetary Orbits in Binary Systems. %A David, Eva-Marie (1) %A Quintana, Elisa V.(2) %A Fatuzzo, Marco (1) %A Adams, Fred C.(2)(3) %B This paper explores the stability of an Earth-like planet orbiting a solar-mass star in the presence of an outer-lying intermediate-mass companion. The overall goal is to estimate the fraction of binary systems that allow Earth-like planets to remain stable over long timescales. We numerically determine the planet's ejection time {tau}_ej_over a range of companion masses (M_C_=0.001-0.5 M_{sun}_), orbital eccentricities {epsilon}, and semimajor axes {\em a}. This suite of ~40,000 numerical experiments suggests that the most important variables are the companion's mass M_C_and periastron distance R_min_=a(1-{epsilon}) to the primary star. At fixed M_C_, the ejection time is a steeply increasing function of R_min_over the range of parameter space considered here (although the ejection time has a distribution of values for a given R_min_). Most of the integration times are limited to 10 Myr, but a small set of integrations extend to 500 Myr. For each companion mass, we find fitting formulae that approximate the mean ejection time as a function of R_min_. These functions can then be extrapolated to longer timescales. By combining the numerically determined ejection times with the observed distributions of orbital parameters for binary systems, we estimate that (at least) 50% of binaries allow an Earth-like planet to remain stable over the 4.6 Gyr age of our solar system. %K astrobiology %K Stars: Binaries: General %K Celestial Mechanics %K Solar System: General %I (1) Department of Physics, Xavier University, Cincinnati, OH 45207. %I (2) Michigan Center for Theoretical Physics, Department of Physics, University of Michigan, Ann Arbor, MI 48109. %I (3) Department of Astronomy, University of Michigan, Ann Arbor, MI 48109; (fca@umich.edu). %R 2003PASP..115..837C %F ori/PASPv115n809 %J-843 %T The Automated Plate Scanner Catalog of the Palomar Observatory Sky Survey. II. The Archived Database. %A Cabanela, Juan E.(1) %A Humphreys, Roberta M. %A Aldering, Greg (2) %A Larsen, Jeffrey A.(3) %A Odewahn, Stephen C.(4) %A Thurmes, Peter M.(5) %A Cornuelle, Chris S. %I Department of Astronomy, University of Minnesota, Minneapolis, MN 55455; (juan@aps.umn.edu), (roberta@aps.umn.edu) %B The Minnesota Automated Plate Scanner Catalog of the POSS I has been available on-line since 1994. We are now archiving it for distribution to the national and international data centers. In this brief paper, we describe the calibration of the digitized data and the characteristics of the archived database. %K astronomical databases: miscellaneous %K Catalogs %I (1) Now at Haverford College. %I (2) Now at Lawrence Berkeley Laboratory. %I (3) Now at Lunar and Planetary Laboratory, University of Arizona. %I (4) Now at Arizona State University. %I (5) Now at Honeywell, Inc., Minneapolis, MN. %R 2003PASP..115..844L %F ori/PASPv115n809 %J-853 %T The Katzman Automatic Imaging Telescope Gamma-Ray Burst Alert System, and Observations of GRB 020813. %A Li, Weidong %A Filippenko, Alexei V. %A Chornock, Ryan %A Jha, Saurabh %I Department of Astronomy, University of California, Berkeley, CA 94720-3411; (wli@astro.berkeley.edu), (alex@astro.berkeley.edu), (rchornock@astro.berkeley.edu), (sjha@astro.berkeley.edu) %B We present the technical details of the gamma-ray burst (GRB) alert system of the Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory and the successful observations of the GRB 020813 optical afterglow with this system. KAIT responds to GRB alerts robotically, interrupts its prearranged program, and takes a sequence of images for each GRB alert. A grid-imaging procedure is used to increase the efficiency of the early-time observations. Different sequences of images have been developed for different types of GRB alerts. With relatively fast telescope slew and CCD readout speed, KAIT can typically complete the first observation within 60 s after receiving a GRB alert, reaching a limiting magnitude of ~19. Our reduction of the GRB 020813 data taken with KAIT shows that unfiltered magnitudes can be reliably transformed to a standard passband with a precision of ~5%, given that the color of the object is known. The GRB 020813 optical afterglow has an exceptionally slow early-time power-law decay index, although other light-curve parameters and the optical spectral index are fairly typical of GRBs. %K gamma rays: bursts %K Instrumentation: Miscellaneous %K Telescopes %R 2003PASP..115..854S %F ori/PASPv115n809 %J-868 %T Statistical Test of Optical Fibers for Use in PMAS, the Potsdam Multi-Aperture Spectrophotometer. %A Schmoll, J.(1) %I Astronomical Instrument Group, Department of Physics, Rochester Building, University of Durham, South Road, Durham DH1 3LE, UK; (jurgen.schmoll@durham.ac.uk) %A Roth, M.M. %I Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany; (mmroth@aip.de) %A Laux, U. %I Th\"uringer Landessternwarte Tautenburg, Sternwarte 5, D-07778 Tautenburg, Germany; (laux@tls-tautenburg.de) %B Focal ratio degradation measurements of optical fibers for the Potsdam Multi-Aperture Spectrophotometer integral field instrument have been performed using the Photometric Testbench of the Potsdam Astrophysical Institute. An effort has been made to obtain sufficiently large statistical samples of individual fiber measurements. The optimization of the measurement process has made it possible to study quantitatively the effects of different coupling methods (air-glass vs. immersion) and of imperfections such as defocus, lateral displacement, and angular misalignment. Furthermore, the effects of mechanical stress on focal ratio degradation have been investigated, confirming the presumed cause of modal noise that is known to limit the maximum signal-to-noise ratio one can achieve with fiber-coupled echelle spectrographs. %K Instrumentation: Spectrographs %K Techniques: Spectroscopic %I (1) Formerly Astrophysikalisches Institut Potsdam. %R 2003PASP..115..869S %F ori/PASPv115n809 %J-878 %T The High-Resolution Light-polluted Night-Sky Spectrum at Mount Hamilton, California(1). %A Slanger, T.G. %A Cosby, P.C. %I Molecular Physics Laboratory, SRI International, Menlo Park, CA 94025; (tom.slanger@sri.com), (philip.cosby@sri.com) %A Osterbrock, D.E. %A Stone, R.P.S. %A Misch, A.A. %I University of California Observatories/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064; (don@ucolick.org), (rem@ucolick.org), (misch@ucolick.org) %B Sky spectra were recorded over San Jose at the Lick Observatory over the 3800-9200 {AA} spectral range, with a spectral resolution of 45,000. Strong atomic lines were detected from Al I, Ar I, Hg I, K I, Li I, Na I, Ne I, Sc I, Sc II, Th I, Th II, and from O I and OH nightglow features. Spectra are contrasted for observations over San Jose (west), the zenith direction, and the eastern sky. When observing in the easterly direction, the emission intensity is still 20%-30% of that seen toward the west. For a natural and stable terrestrial nightglow line, O I {lambda}5577, the intensity is comparable in either direction. A variety of line shapes are observed, reflecting the outputs of the m\'elange of pollution sources. A total of 177 identified light-pollution lines were observed, of which more than half are due to Sc I and Sc II. The Sc I lines show a systematic shift to longer wavelengths from the expected positions, amounting to an average of 25 m{AA}. This is presumably a consequence of their origin, high-pressure metal halide lamps. By comparing the intensity of the strongest pollution lines and continuum (from Na) with the nightglow O I {lambda}5577 line, a figure of merit for the pollution line intensity is the equivalent of 4 kR for the atmospheric conditions and viewing geometry investigated. %K Atmospheric Effects %K Techniques: Spectroscopic %I (1) Lick Observatory Bulletin 1401. %R 2003PASP..115..879C %F ori/PASPv115n809 %J-887 %T Optical Seeing at Sierra Negra. %A Carrasco, Esperanza %A Carrami\~nana, Alberto %A Avil\'es, Jos\'e Luis %A Yam, Omar %I Instituto Nacional de Astrof\'isica, \'Optica y Electr\'onica, Luis Enrique Erro 1, Tonantzintla, Puebla 72840, Mexico; (bec@inaoep.mx) %B Optical seeing measurements carried out at Sierra Negra, the site of the Large Millimeter Telescope, are reported. The site, one of the highest peaks in central Mexico, offers good coverage of the northern and southern hemispheres, and we have undertaken several campaigns to investigate the astronomical potential of the site in the optical. Here we report on our campaign to establish the seeing quality of the site. We present data from the first three campaigns of optical seeing monitoring covering 2000 February to 2002 May, carried out with a Differential Image Motion Monitor. The results clearly indicate subarcsecond seeing, better statistics during the dry season, and no dependence on the time of night. We find no dependence of our results on the integration time used. %K Atmospheric Effects %K Site Testing %R 2003PASP..115..888Y %F ori/PASPv115n809 %J-888 %T Spectral Analyses of 4 Lacertae and {nu} Cephei. (Dissertation Summary). %A Y\"uce, Kutluay %I Current address: Ankara University, Department of Astronomy and Space Sciences, 06100 Tando{gbreve}an, Ankara, Turkey; (kyuce@astro1.science.ankara.edu.tr)Thesis work conducted at Ankara UniversityPh.D. thesis directed by Semanur Engin (Ankara University) and Saul J. Adelman (The Citadel); Ph.D. degree awarded 2003 March %K Dissertation Summaries %K Stars: Abundances %K Stars: Early-Type %K Stars: Evolution %K Stars: Supergiants %R 2003PASP..115..889C %F ori/PASPv115n809 %J-889 %T Dynamical Evolution of Dust in Expanding Circumstellar Shells. (Dissertation Summary). %A Covatto, Carl %I Current address: Department of Physics and Astronomy, Arizona State University, Tempe, AZ 85287; (carl.covatto@asu.edu)Thesis work conducted at Arizona State UniversityPh.D. thesis directed by Per A. Aannestad; Ph.D. degree awarded 2002 May %K Stars: Circumstellar Matter %K Dissertation Summaries %K Stars: Mass Loss %K Stars: Winds, Outflows %R 2003PASP..115..890T %F ori/PASPv115n809 %J-896 %T Jesse Leonard Greenstein (1909-2002). (Obituary). %A Trimble, Virginia %I Department of Astronomy, University of Maryland, College Park, MD 20742; and Department of Physics and Astronomy, University of California, Irvine, CA 92697