%...Journal: PASP
%...MainTag: '<UCP-HEADER'
%R=BibCode
%A=Authors
%B=Abstract
%c=Copyright
%D=Date of publication
%E=Electronic file
%F=Original File
%I=Institute and/or Footnotes
%J-last page
%K=Keywords
%T=Title
%Z=Editor's Notes sup. meterial

%R 2001PASP..113..775C
%F ori/PASPv113n785
%J-788
%T A Theoretical Exploration of the Pulsational Stability of Subdwarf B Stars(1).
   (Review).
%A Charpinet, St\'ephane
%I Laboratoire d'Astrophysique de l'Observatoire Midi-Pyr\'en\'ees, 14 Avenue Edouard
   Belin, 31400 Toulouse, France; (scharpin@ast.obs-mip.fr)
%A Fontaine, G.
%A Brassard, P.
%I D\'epartement de Physique, Universit\'e de Montr\'eal, Succ. Centre-Ville, Montr\'eal,
   QC H3C 3J7, Canada; (fontaine@astro.umontreal.ca), (brassard@astro.umontreal.ca)
%B In this paper, we first review the main steps of a purely theoretical exploration
   of the pulsation properties of subdwarf B (sdB) stars that led us, ultimately,
   to postulate the existence of a new class of pulsating stars. Using both
   detailed evolutionary and static models of sdB stars, we were able to establish
   that a potent oscillation driving mechanism exists in these objects. This
   mechanism results from the {kappa}-effect associated with a local enrichment
   of iron in the stellar envelope caused by diffusion. On this basis, we reached
   the conclusion that a fraction of hot B subdwarf stars should show observable
   pulsational instabilities, a theoretical prediction that was confirmed observationally
   by the independent discovery of real sdB pulsators by a team of astronomers
   at the South African Astronomical Observatory. We also review the current
   status of sdB star seismology, a field that has been growing at a fast pace following
   this key discovery. For that purpose, we present sample results obtained
   from more recent pulsation computations based on improved stellar models--our
   so-called second-generation models--which include a detailed treatment for
   gravitational settling and radiative levitation of iron. These clearly reveal
   that the theoretical expectations built upon the recognition of the iron
   driving mechanism in pulsating sdB stars reproduce remarkably well the observational
   data currently available. Such results confirm the basic ideas that we developed and
   that explain the origin of pulsations in sdB stars. They also pave the way
   for the future exploitation of the full asteroseismological potential of
   these stars.
%K Stars: Interiors
%K Stars: Oscillations
%K Stars: Subdwarfs
%I (1) Based on the J. S. Plaskett Lecture presented by S. Charpinet at
   the annual meeting of the Canadian Astronomical Society held in Halifax (1999 June).

%R 2001PASP..113..789G
%F ori/PASPv113n785
%J-802
%T The Optical/Infrared Astronomical Quality of High Atacama Sites. I. Preliminary
   Results of Optical Seeing.
%A Giovanelli, Riccardo (1)
%A Darling, Jeremy (1)
%A Sarazin, Marc (2)
%A Yu, Jennifer (3)
%A Harvey, Paul (4)
%A Henderson, Charles (1)
%A Hoffman, William (1)
%A Keller, Luke (1)
%A Barry, Don (1)
%A Cordes, James (1)
%A Eikenberry, Stephen (1)
%A Gull, George (1)
%A Harrington, Joseph (1)
%A Smith, J.D. (1)
%A Stacey, Gordon (1)
%A Swain, Mark (1)
%B The region surrounding the Llano de Chajnantor, a high-altitude plateau
   in the Atacama Desert in northern Chile, has caught the attention of the
   astronomical community for its potential as an observatory site. Combining
   high elevation and extremely low atmospheric water content, the Llano has
   been chosen as the future site of the Atacama Large Millimeter Array. We
   have initiated a campaign to investigate the astronomical potential of the
   region in the optical/infrared. Here we report on an aspect of our campaign
   aimed at establishing a seeing benchmark to be used as a reference for future
   activities in the region. After a brief description of the region and its
   climate, we describe the results of an astronomical seeing campaign, carried
   out with a Differential Image Motion Monitor that operates at 0.5 {mu}m wavelength.
   The seeing at the Llano altitude of 5000 m, measured over 7 nights in 1998
   May, yielded a median FWHM of 1".1. However, the seeing decreased to 0".7
   at a modest 100 m gain above the plateau (Cerro Chico), as measured over
   38 nights spread between 1998 July and 2000 October. Neither of these represents
   the best seeing expected in the region; the set of measurements provides
   a reference base for simultaneous dual runs at Cerro Chico and at other sites of
   interest in the region, currently underway. A comparison between simultaneous
   measurements at Cerro Chico and Cerro Paranal indicates that the seeing at
   Cerro Chico is about 12% better than that at Paranal. The percentage of optically
   photometric nights in the Chajnantor region is about 60%, while that of nights
   useful for astronomical work is near 80%.
%K Atmospheric Effects
%K Site Testing
%I (1) Department of Astronomy, Cornell University, Ithaca, NY 14853; (riccardo@astrosun.tn.cornell.edu).
%I (2) European Southern Observatory, D-85748 Garching bei M\"unchen, Germany.
%I (3) Department of Earth and Atmospheric Sciences, Cornell University, Ithaca,
   NY 14853.
%I (4) Department of Astronomy, University of Texas, Austin, TX 78712.

%R 2001PASP..113..803G
%F ori/PASPv113n785
%J-813
%T The Optical/Infrared Astronomical Quality of High Atacama Sites. II. Infrared
   Characteristics.
%A Giovanelli, Riccardo
%A Darling, Jeremy
%A Henderson, Charles
%A Hoffman, William
%A Barry, Don
%A Cordes, James
%A Eikenberry, Stephen
%A Gull, George
%A Keller, Luke
%A Smith, J.D.
%A Stacey, Gordon
%I Department of Astronomy, Cornell University, Ithaca, NY 14853; (riccardo@astrosun.tn.cornell.edu)
%B We discuss properties of the atmospheric water vapor above the high Andean
   plateau region known as the Llano de Chajnantor, in the Atacama Desert of
   northern Chile. A combination of radiometric and radiosonde measurements
   indicates that the median column of precipitable water vapor (PWV) above
   the plateau at an elevation of 5000 m is approximately 1.2 mm. The exponential
   scale height of the water vapor density in the median Chajnantor atmosphere
   is 1.13 km; the median PWV is 0.5 mm above an elevation of 5750 m. Both of
   these values appear to be lower at night. Annual, diurnal, and other dependences
   of PWV and its scale height are discussed, as well as the occurrence of temperature
   inversion layers below the elevation of peaks surrounding the plateau. We
   estimate the background for infrared observations and sensitivities for broadband
   and high-resolution spectroscopy. The results suggest that exceptional atmospheric
   conditions are present in the region, yielding high infrared transparency
   and high sensitivity for future ground-based infrared telescopes.
%K Atmospheric Effects
%K Site Testing

%R 2001PASP..113..814K
%F ori/PASPv113n785
%J-820
%T Three Newly Discovered M-Dwarf Companions of Solar Neighborhood Stars(1).
%A Kirkpatrick, J.Davy
%I Infrared Processing and Analysis Center, MS 100-22, California Institute
   of Technology, Pasadena, CA 91125; (davy@ipac.caltech.edu)
%A Liebert, James
%I Steward Observatory, University of Arizona, Tucson, AZ 85721; (liebert@as.arizona.edu)
%A Cruz, K.L. (2)
%I Department of Physics and Astronomy, University of Pennsylvania, 209 South
   33rd Street, Philadelphia, PA 19104-6396; (kelle@hep.upenn.edu)
%A Gizis, J.E.
%I Infrared Processing and Analysis Center, MS 100-22, California Institute
   of Technology, Pasadena, CA 91125; (gizis@ipac.caltech.edu)
%A Reid, I.Neill (2)
%I Department of Physics and Astronomy, University of Pennsylvania, 209 South
   33rd Street, Philadelphia, PA 19104-6396; and Space Telescope Science Institute,
   3700 San Martin Drive, Baltimore, MD 21218; (inr@stsci.edu)
%B We present low-resolution spectroscopy of newly discovered candidate
   companions to three stars in the solar neighborhood. All three companions
   are M dwarfs, with spectral types ranging from M4 to M9.5. In two cases,
   G85-55B (M6) and G87-9B (M4), we have circumstantial evidence from spectroscopy,
   photometry, and limited astrometry that the systems are physical binaries;
   in the third, G216-7B (M9.5), comparison of POSS II IIIaF plate material
   and the 2MASS image indicates common proper motion. The primary star in this
   system, G216-7A (M0), is itself an unresolved, nearly equal-mass binary.
   All three low-mass companions are highly likely to be stellar in nature,
   although G216-7B lies very close to the hydrogen-burning limit.
%K Galaxy: Stellar Content
%K Stars: Low-Mass, Brown Dwarfs
%I (1) Portions of the data presented here were obtained at the W. M. Keck Observatory,
   which is operated as a scientific partnership among the California Institute
   of Technology, the University of California, and the National Aeronautics
   and Space Administration. The Observatory was made possible by the generous
   financial support of the W. M. Keck Foundation. We also make use of data
   obtained with the Palomar 60 inch telescope, owned jointly by the California
   Institute of Technology and the Carnegie Institution of Washington.
%I (2) Visiting Astronomer at the Infrared Telescope Facility, which is operated
   by the University of Hawaii under contract from the National Aeronautics
   and Space Administration.

%R 2001PASP..113..821F
%F ori/PASPv113n785
%J-828
%T Spectrum Variability of the A-Type Supergiant Star HD 223960.
%A Fischer, William J.
%A Morrison, Nancy D.
%I Ritter Astrophysical Research Center, University of Toledo, Toledo, OH 43606;
   (wfische@uoft02.utoledo.edu), (nmorris2@uoft02.utoledo.edu)
%B HD 223960, an A0 Ia-type supergiant in the Cas OB5 association, is unusual
   among Galactic supergiants of its class in having an H{alpha} profile with
   double-peaked emission entirely above the continuum. We analyzed 12 high-resolution
   \'echelle spectra obtained in 1993-1995 and in 1999 with the 1 m telescope
   of Ritter Observatory. The radial velocities of photospheric Si, C, He, Ne,
   and S lines were found to be constant to within +/-2 km.s^-1^, but the data suggest
   variability in the equivalent widths of Si II {lambda}{lambda}6347, 6371
   and several other photospheric lines. The radial velocities and equivalent
   widths and, especially, the ratio V/R of the H{alpha} components vary. The present
   data do not indicate a binary explanation for the double-peaked emission
   feature. Alternative explanations are considered, but none is completely
   satisfactory. The available evidence is consistent with the star having a
   weak, fast wind.
%K Stars: Early-Type
%K Stars: Emission-Line, Be
%K stars: individual (HD 223960)
%K Stars: Mass Loss
%K Stars: Winds, Outflows
%K Stars: Supergiants

%R 2001PASP..113..829N
%F ori/PASPv113n785
%J-834
%T The Accretion Disk and White Dwarf in the Short-Period Dwarf Novae TY Piscium
   and V436 Centauri during Quiescence.
%A Nadalin, Ira
%A Sion, Edward M.
%I Department of Astronomy and Astrophysics, Villanova University, Vilanova,
   PA 19085; (ira.nadalin@villanova.edu), (edward.sion@villanova.edu)
%B The short-period dwarf novae TY Psc and V436 Cen are SU UMa systems
   with very similar orbital periods, similar recurrence times for normal outbursts
   (~23 days) and superoutbursts (~340 days), and nearly identical outburst
   amplitudes. We have carried out high-gravity model atmosphere and accretion
   disk synthetic spectra from the grid of Wade & Hubeny. The best-fit stellar
   model spectrum, from spectral slope and line fitting, is a white dwarf photosphere
   having T_eff_=25,000 K, logg=8, and essentially solar chemical abundances,
   while the best-fit optically thick accretion disk model, from spectral slope
   fitting, has M_wd_=0.55 M_{sun}_, M{dot}=10^-9.5^ M_{sun}_ yr^-1^, and an inclination
   i=18{deg}. The implied accretion rate is almost certainly too large for dwarf
   nova quiescence. The predicted fluxes using parameters from the photosphere
   and disk spectral slope fitting models reveal enormous differences compared
   with the observed luminosity using a reasonable distance estimate. For TY
   Psc, the predicted accretion disk luminosity is ~100 times too luminous,
   while the stellar luminosity is too luminous by a factor of ~10. For V436
   Cen, the best-fit high-gravity model photosphere, from spectral slope fitting,
   yields T_eff_=24,000 K, logg=8, and essentially solar abundance, while the
   best-fit accretion disk models, from spectral slope fitting, yield M_wd_=0.8 M_{sun}_, M{dot}=10^-10^ M_{sun}_
   yr^-1^, and i=75{deg}. The presence of broad absorption troughs at unusual
   wavelength positions suggests the presence of an absorption curtain (upper
   disk atmosphere) in V436 Cen. The temperatures we have for TY Psc and V436
   Cen are higher than normal for the accreting white dwarfs in dwarf novae
   below the period gap. This could indicate that the systems were not in the
   deepest level of quiescence when they were observed.
%K Stars: Novae, Cataclysmic Variables
%K stars: individual (TY Piscium)
%K stars: individual (V436 Centauri)
%K Stars: White Dwarfs

%R 2001PASP..113..835L
%F ori/PASPv113n785
%J-838
%T The Blazhko Effect of the RR Lyrae Star FM Persei.
%A Lee, Kevin M.
%A Schmidt, Edward G.
%I Behlen Observatory, Department of Physics and Astronomy, University of Nebraska, Lincoln,
   NE 68588-0111; (klee6@unl.edu)
%B We have obtained 615 new {\em V} and {\em R} observations of the RR
   Lyrae star FM Per. A period search identified a primary period of 0.489256
   days; however, the light curve of FM Per cannot be well described by a single
   period. We conclude that FM Per demonstrates the Blazhko effect with a Blazhko
   period of approximately 122 days.
%K stars: individual (FM Persei)
%K Stars: Variables: Other

%R 2001PASP..113..839P
%F ori/PASPv113n785
%J-845
%T The Masses of the Progenitors of Planetary Nebulae.
%A Phillips, J.P.
%I Instituto de Astronomia y Meteorologia, Avenida Vallarta 2602, Col. Arcos
   Vallarta, C.P. 44130 Guadalajara, Jalisco, Mexico; (jpp@udgserv.cencar.udg.mx)
%B Bipolar, elliptical, and circular planetary nebulae appear to be possessed
   of differing Galactic scale heights, a feature which is usually assumed to
   arise from the differing distributions and masses of their progenitor stars.
   It would appear that more massive progenitors are responsible for bipolar
   sources, whilst the least massive progenitors give rise to circular sources.
   This, clearly, is an important result, since it implies that shell formation
   mechanisms must be closely intertwined with progenitor type. We point out,
   however, that previous estimates of nebular scale height are at best somewhat
   sketchy and may even be wrong. At least two prior analyses, for instance,
   appear to compare reddened values of nebular scale height with extinction-corrected
   stellar scale heights. We have therefore attempted, in the following, to
   undertake a dereddening of nebular scale heights and perform a fresh comparison
   of these results with those for Galactic stars of differing spectral types.
   We find that circular and elliptical sources are likely to originate from early
   F-type stars and bipolar sources from stars of spectral type A7 or earlier.
   The results appear to be insensitive to uncertainties in the distance scale.
%K ISM: Dust, Extinction
%K ISM: Planetary Nebulae: General

%R 2001PASP..113..846P
%F ori/PASPv113n785
%J-850
%T Bipolar Nebulae: The Missing Population.
%A Phillips, J.P.
%I Instituto de Astronomia y Meteorologia, Avenida Vallarta 2602, Col. Arcos
   Vallarta, C.P. 44130 Guadalajara, Jalisco, Mexico; (jpp@udgserv.cencar.udg.mx)
%B We have undertaken an analysis of observed aspect ratios for the collimation
   disks in bipolar nebulae (BPNe). We find, as a result, that most such structures
   are likely to have a ratio of thickness to diameter b/a~0.23. Similarly,
   the paucity of disks having aspect ratios {>=}0.7 implies that many of the
   sources are either unobserved or, what is more probably the case, misidentified.
   It seems likely, as a result, that the true population of BPNe is ~1.7 times
   greater than previously supposed. Similarly, we determine that as many as
   of 43% of annular or ringlike planetaries may represent bipolar sources oriented
   along the line of sight.
%K ISM: Jets and Outflows
%K ISM: Planetary Nebulae: General

%R 2001PASP..113..851B
%F ori/PASPv113n785
%J-858
%T Modal Noise in High-Resolution, Fiber-fed Spectra: A Study and Simple Cure.
%A Baudrand, Jacques
%I Observatoire de Meudon, 5 Place Janssen, F-92195 Meudon, France; (Jacques.Baudrand@obspm.fr)
%A Walker, Gordon A.H.
%I 1234 Hewlett Place, Victoria, BC V8S 4P7, Canada; (walker@astro.ubc.ca)
%B The transmission modes of a fiber introduce an unstable intensity distribution
   in high-resolution spectra which cannot be eliminated by flat-fielding because
   the pattern is sensitive to any small changes in fiber position or illumination.
   These instabilities, rather than photon shot noise, limit the achievable
   signal-to-noise ratio (S/N). In controlled laboratory experiments at a resolution
   of ~150,000, we found S/N limited to {<=}500 for a range of fiber perturbations
   and illumination geometries from simple displacement to simulated seeing
   variations. We find an empirical relation between the number of monochromatic
   modes and the level of modal noise for which we offer no rigorous explanation.
   More important, we demonstrate that continuous, low-amplitude agitation of
   the fiber close to its output completely eliminates the problem.
%K Instrumentation: Spectrographs

%R 2001PASP..113..859B
%F ori/PASPv113n785
%J-871
%T Properties of PACE-I HgCdTe Detectors in Space: The NICMOS Warm-Up Monitoring Program.
%A B\"oker, T. (1)
%A Bacinski, J.
%A Bergeron, L.
%A Calzetti, D.
%A Jones, M.
%A Gilmore, D.
%A Holfeltz, S.
%A Monroe, B.
%A Nota, A. (1)
%A Sosey, M.
%I Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218;
   (boeker@stsci.edu)
%A Schneider, G.
%A O'Neil, E.
%A Hubbard, P.
%A Ferro, A.
%A Barg, I.
%A Stobie, E.
%I Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson,
   AZ 85721
%B We summarize the results of a monitoring program which was executed following
   the cryogen exhaustion of the Near Infrared Camera and Multi-Object Spectrometer
   (NICMOS) on board the {\em Hubble Space Telescope}. During the subsequent
   warm-up, detector parameters such as detective quantum efficiency, dark current,
   bias offsets, and saturation levels have been measured over the temperature
   range 62 K to about 100 K. The measurements provide a unique database of
   the characteristics of PACE-I HgCdTe detector arrays in the space environment.
   A surprising result of the analysis is the fact that all three NICMOS detectors
   showed an enhanced dark current in the temperature range between 77 and 85
   K. However, a subsequent laboratory experiment designed to replicate the
   on-orbit warm-up did not reproduce the anomaly, despite the fact that it
   employed a flight-spare detector of the same pedigree. The mechanism behind
   the on-orbit dark current anomaly is therefore believed to be unique to the
   space environment. We discuss possible explanations for these unexpected
   observational results, as well as their implications for future NICMOS operations.
%K Instrumentation: Detectors
%I (1) Affiliated with the Astrophysics Division, Space Science Department,
   European Space Agency.

%R 2001PASP..113..872K
%F ori/PASPv113n785
%J-881
%T A Fast Technique for the Creation of Large-Scale High-Resolution {\em IRAS}
   (HIRES) Beam-matched Images.
%A Kerton, C.R.
%I Dominion Radio Astrophysical Observatory, Herzberg Institute of Astrophysics, National
   Research Council, P.O. Box 248, Penticton, BC V2A 6K3, Canada; (charles.kerton@nrc.ca)
%A Martin, P.G.
%I Canadian Institute for Theoretical Astrophysics and Department of Astronomy, University
   of Toronto, 60 St. George Street, Toronto, ON M5S 3H8, Canada; (pgmartin@cita.utoronto.ca)
%B HIRES processing provides a significant improvement in both resolution and
   image quality over previous {\em IRAS} image products, but the characteristics
   of the HIRES beam make accurate comparisons between the various {\em IRAS}
   bandpasses and between HIRES data and data at other wavelengths nontrivial.
   We present a new, fast technique for the construction of HIRES beam-matched
   images that is especially well suited for the creation of large-scale (several
   square degree) ratio maps. Other techniques for the construction of ratio
   maps are discussed and compared with the new algorithm. Examples of the large-scale
   ratio maps that can be constructed using this new technique are presented.
   The algorithm's application to the construction of multiwavelength difference
   images and multicolor images is also demonstrated.
%K ISM: Dust, Extinction
%K infrared: general
%K Surveys
%K Techniques: Image Processing

%R 2001PASP..113..882S
%F ori/PASPv113n785
%J-897
%T A Study of the Wavelength Calibration of NEWSIPS High-Dispersion Spectra.
%A Smith, Myron A. (1)
%B In this study we cross-correlate many {\em IUE} echellograms of a variety
   of well-observed stars to evaluate systematic error sources in the wavelength
   zero points (velocities) of all three cameras. We first evaluate differences
   between the final archived (``NEWSIPS'') and the originally processed (``IUESIPS'')
   echellograms. These show a marked time dependence in zero point for the SWP
   camera resulting from several revisions of wavelength calibration coefficients
   used for IUESIPS. Smaller offsets are present for the LWR camera between
   the two processings. We also evaluated small-amplitude fluctuations in the
   zero points of the NEWSIPS wavelength calibration spectra themselves. In
   the case of the SWP camera, these variations are too complicated to have
   been completely removed in the NEWSIPS wavelength calibration. We also examine
   wavelength zero-point disparities between data obtained both through the
   small and large entrance apertures as well as for observations made by different target
   acquisitions of faint and bright stars. We also find that statistical differences
   between these alternative observing modes are virtually nil. For large-aperture
   observations, the dominant error source is the placement of the target in
   the aperture. These give rise to non-Gaussian, extended ``tails'' in apparent
   velocity. We also searched for spurious trends. Except for a possible trend
   for faint objects with SWP camera data, we cannot detect significant dependences
   with time. Additionally, we discovered a trend with telescope focus for data sets
   derived from intensive monitoring campaigns of bright stars. These exhibit
   a repeatable, 1 day ``radial velocity variation'' with a semiamplitude of nearly
   3 km.s^-1^. This pattern appears to be a by-product of fluctuations in telescope
   focus caused by operational procedures to maintain the ambient instrument
   temperature.\par In the second part of the paper, we measure the mean zero-point errors
   of NEWSIPS echellogram data with respect to laboratory results by using the
   Goddard High Resolution Spectrograph (GHRS) spectral atlas of the O9 V spectral
   standard 10 Lacertae as an intermediary reference. We find that the derived
   apparent velocity difference for this star is essentially zero: -1+/-3.5 km.s^-1^.
   Several less precise comparisons lead to similar results, including cross-correlations
   of (1) spectra of 10 Lac and two stars with similar spectra, HD 93521 and
   HD 60753; (2) lines in common with the SWP camera and GHRS and STIS atlases
   of Arcturus and Procyon; and (3) interstellar lines in the GHRS spectrum
   of the white dwarf G191-B2B. The zero points of the NEWSIPS-processed long-wavelength
   cameras are evaluated and are also found to be nearly zero (+/-5 km.s^-1^)
   relative to the Arcturus and Procyon atlas calibrations and relative to one
   another. In general, these results do not support the suggestion by Gonz\'alez-Riestra
   and coworkers that corrections should be introduced to the wavelength scales
   of various NEWSIPS high-dispersion data products. Despite our optimistic
   results, it is obvious that using small {\em IUE} data sets from large-aperture
   observations of arbitrarily chosen stars can contain velocity errors of at
   least a few km.s^-1^.
%K Instrumentation: Spectrographs
%K Methods: Data Analysis
%K Techniques: Photometric
%K Ultraviolet: Stars
%I (1) Computer Sciences Corporation/Space Telescope Science Institute,
   3700 San Martin Drive, Baltimore, MD 21218; (msmith@stsci.edu).

%R 2001PASP..113..898W
%F ori/PASPv113n785
%J-898
%T Investigation of the Ultraviolet Interstellar Extinction Curve. (Dissertation
   Summary).
%A Will, Lisa M.
%I Present address: Mesa Community College and Arizona State University; (lisa.will@asu.edu)Thesis
   work conducted at Arizona State UniversityPh.D. thesis directed by Per A.
   Aannestad; Ph.D. degree awarded 2000 August
%K Dissertation Summaries
%K ISM: Dust, Extinction
%K ultraviolet: ISM