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The Gemini Spectral Library of Near-IR Late-Type Stellar Templates and Its Application for Velocity Dispersion Measurements
We present a spectroscopic library of late spectral type stellartemplates in the near-IR range 2.15-2.42 μm, at R = 5300-5900resolution, oriented to support stellar kinematics studies in externalgalaxies, such as the direct determination of the masses of supermassiveblack holes in nearby active (or non-active) galaxies. The combinationof high spectral resolution and state-of-the-art instrumentationavailable in 8 m class telescopes has made the analysis of circumnuclearstellar kinematics using the near-IR CO band heads one of the most usedtechniques for such studies, and this library aims to provide thesupporting data sets required by the higher spectral resolution andlarger spectral coverage currently achieved with modern near-IRspectrographs. Examples of the application for kinematical analysis aregiven for data obtained with two Gemini instruments, but the templatescan be easily adjusted for use with other near-IR spectrographs atsimilar or lower resolution. The example data sets are also used torevisit the "template mismatch" effect and the dependence of thevelocity dispersion values obtained from the fitting process with thecharacteristics of the stellar templates. The library is available inelectronic form from the Gemini Web pages..
| A Pair of Leading Spiral Arms in a Luminous Infrared Galaxy?
Leading spiral arms are a rare phenomenon. We present here one of thevery few convincing candidates of spiral arms opening counterintuitivelyin the same direction as the galaxy disk is rotating. This detection inthe luminous IR galaxy (LIRG) IRAS 18293-3413 is based on near-infrared(NIR) adaptive optics imaging with the Very Large Telescope andlong-slit NIR spectroscopy with the Anglo-Australian Telescope. Wediscuss the orientation of the galaxy based on imaging and deriverotation curves from both emission and absorption features in thespectrum. The galaxy is strongly star-forming and has a minor companionin a high-velocity encounter. The fact that the arms of IRAS 18293-3413are not easily traceable from optical images suggests that largersamples of high-quality NIR imaging of interacting systems and LIRGsmight uncover further cases of leading arms, placing constraints onspiral arm theories and retrogade encounters, and especially on therelationship between disk masses and dark matter halo masses.Based on observations made with the ESO telescopes at the ParanalObservatory under program 073.D-0406B and observations made at theAnglo-Australian Telescope.
| New periodic variables from the Hipparcos epoch photometry
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
| Multiperiodicities from the Hipparcos epoch photometry and possible pulsation in early A-type stars
A selection criterion based on the relative strength of the largestpeaks in the amplitude spectra, and an information criterion are used incombination to search for multiperiodicities in Hipparcos epochphotometry. The method is applied to all stars which have beenclassified as variable in the Hipparcos catalogue: periodic, unsolvedand microvariables. Results are assessed critically: although there aremany problems arising from aliasing, there are also a number ofinteresting frequency combinations which deserve further investigation.One such result is the possible occurrence of multiple periods of theorder of a day in a few early A-type stars. The Hipparcos catalogue alsocontains a number of these stars with single periodicities: such starswith no obvious variability classifications are listed, and informationabout their properties (e.g., radial velocity variations) discussed.These stars may constitute a new class of pulsators.
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| A study of visual double stars with early type primaries. IV Astrophysical data
Astrophysical parameters (MK class, color excess, absolute magnitude,distance, effective temperature, mass, and age) are derived fromcalibrations of the uvby-beta indices for the members of 253 doublestars with O or B type primaries and faint secondaries. The photometricspectral classification is compared to the MK classes, and the agreementis very good. The derived data together with spectroscopic and JHKL dataare used for deciding which pairs are likely to be physical and whichare optical, and it is shown that 98 (34 percent) of the secondaries arelikely to be members of physical systems. For 90 percent of the physicalpairs the projected separation between the components is less than25,000 AU. A majority of the physical secondaries are late-type stars,and 50 percent of them are contracting towards the zero-agemain-sequence. Also presented are new uvby-beta data for 43 secondariesand a computer program for determining astrophysical parameters fromuvby-beta data.
| Spectral types for early-type stars observed by SKYLAB
MK spectral types are presented for 246 early-type stars observed withthe S-019 ultraviolet stellar astronomy experiment on Skylab. K-linetypes are also given where applicable, and various peculiar stars areidentified. The peculiar stars include five silicon stars, a shell star,a helium-rich star, a silicon-strontium star, a chromium-europium star,and two marginal metallic-line stars.
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