Mid-infrared interferometry of the Mira variable RR Sco with the VLTI MIDI instrument
We present the results of the first mid-infrared interferometricobservations of the Mira variable RR Sco with the MID-infraredInterferometer (MIDI) coupled to the European Southern Observatory's(ESO) Very Large Telescope Interferometer (VLTI), together with K-bandobservations using VLTI VINCI. The observations were carried out in June2003, when the variability phase of the object was 0.6, using two unittelescopes (UT1 and UT3), as part of the Science Demonstration Time(SDT) program of the instrument. Projected baseline lengths ranged from73 to 102 m, and a spectral resolution of 30 was employed in theobservations, which enabled us to obtain the wavelength dependence ofthe visibility in the region between 8 and 13 μm. The uniform-diskdiameter was found to be 18 mas between 8 and 10 μm, while itgradually increases at wavelengths longer than 10 μm to reach 24 masat 13 μm. The uniform-disk diameter between 8 and 13 μm issignificantly larger than the K-band uniform-disk diameter of 10.2± 0.5 mas measured using VLTI VINCI with projected baselinelengths of 15-16 m, three weeks after the MIDI observations. Our modelcalculations show that optically thick emission from a warm molecularenvelope consisting of H2O and SiO can cause the apparent mid-infrared diameter to be much larger than the continuum diameter. Wefind that the warm molecular envelope model extending to 2.3R\star with a temperature of 1400 K and column densitiesof H2O and SiO of 3 × 1021 cm-2and 1 × 1020 cm-2, respectively, canreproduce the observed uniform-disk diameters between 8 and 10 μm.The observed increase of the uniform-disk diameter longward of 10 μmcan be explained by an optically thin dust shell consisting of silicateand corundum grains. The inner radius of the optically thin dust shellis derived to be 7-8 R\star with a temperature of 700 K,and the optical depth at 10 μm is found to be 0.025.Based on observations made with the Very Large Telescope Interferometerof the European Southern Observatory.
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Mid-infrared sizes of circumstellar disks around Herbig Ae/Be stars measured with MIDI on the VLTI
We present the first long baseline mid-infrared interferometricobservations of the circumstellar disks surrounding Herbig Ae/Be stars.The observations were obtained using the mid-infrared interferometricinstrument MIDI at the European Southern Observatory (ESO) Very LargeTelescope Interferometer VLTI on Cerro Paranal. The 102 m baseline givenby the telescopes UT1 and UT3 was employed, which provides a maximumfull spatial resolution of 20 milli-arcsec (mas) at a wavelength of 10μm. The interferometric signal was spectrally dispersed at aresolution of 30, giving spectrally resolved visibility information from8 μm to 13.5 μm. We observed seven nearby Herbig Ae/Be stars andresolved all objects. The warm dust disk of HD 100546 could even beresolved in single-telescope imaging. Characteristic dimensions of theemitting regions at 10 μm are found to be from 1 AU to 10 AU. The 10μm sizes of our sample stars correlate with the slope of the 10-25μm infrared spectrum in the sense that the reddest objects are thelargest ones. Such a correlation would be consistent with a differentgeometry in terms of flaring or flat (self-shadowed) disks for sourceswith strong or moderate mid-infrared excess, respectively. We comparethe observed spectrally resolved visibilities with predictions based onexisting models of passive centrally irradiated hydrostatic disks madeto fit the SEDs of the observed stars. We find broad qualitativeagreement of the spectral shape of visibilities corresponding to thesemodels with our observations. Quantitatively, there are discrepanciesthat show the need for a next step in modelling of circumstellar disks,satisfying both the spatial constraints such as are now available fromthe MIDI observations and the flux constraints from the SEDs in aconsistent way.Based on observations made with the Very Large Telescope Interferometerat Paranal Observatory.
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Hipparcos red stars in the HpV_T2 and V I_C systems
For Hipparcos M, S, and C spectral type stars, we provide calibratedinstantaneous (epoch) Cousins V - I color indices using newly derivedHpV_T2 photometry. Three new sets of ground-based Cousins V I data havebeen obtained for more than 170 carbon and red M giants. These datasetsin combination with the published sources of V I photometry served toobtain the calibration curves linking Hipparcos/Tycho Hp-V_T2 with theCousins V - I index. In total, 321 carbon stars and 4464 M- and S-typestars have new V - I indices. The standard error of the mean V - I isabout 0.1 mag or better down to Hp~9 although it deteriorates rapidly atfainter magnitudes. These V - I indices can be used to verify thepublished Hipparcos V - I color indices. Thus, we have identified ahandful of new cases where, instead of the real target, a random fieldstar has been observed. A considerable fraction of the DMSA/C and DMSA/Vsolutions for red stars appear not to be warranted. Most likely suchspurious solutions may originate from usage of a heavily biased color inthe astrometric processing.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA 1997).}\fnmsep\thanks{Table 7 is onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/397/997
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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.
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The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
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Classification and Identification of IRAS Sources with Low-Resolution Spectra
IRAS low-resolution spectra were extracted for 11,224 IRAS sources.These spectra were classified into astrophysical classes, based on thepresence of emission and absorption features and on the shape of thecontinuum. Counterparts of these IRAS sources in existing optical andinfrared catalogs are identified, and their optical spectral types arelisted if they are known. The correlations between thephotospheric/optical and circumstellar/infrared classification arediscussed.
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Red supergiants as starburst tracers in galactic nuclei.
We present infrared spectral observations of CO (1.62, 2.29μm) and Si(1.59μm) stellar absorption features in 23 galaxies including 14calibrators (normal ellipticals/spirals and well known HII galaxies) and9 Seyferts. Our main aim was to define and calibrate an observationalmethod for tracing red supergiants (i.e. starbursts) in active galaxies.Additional spectra were also obtained around the Brγ hydrogenrecombination line. The measured equivalent widths of the absorptionfeatures in old stellar systems and HII galaxies are found to beremarkably similar and the CO and Si indices do not therefore providereliable diagnostics for distinguishing red supergiants (i.e.starbursts) from metallic red giants (i.e. old stellar systems). A moresensitive quantity is found to be the light to mass ratio (L_H_/M) asinferred from the observed 1.65μm stellar luminosities and velocitydispersions. All HII galaxies and several of the Seyfert 2's exhibitL_H_/M values a factor =~5 larger than normal ellipticals and spirals.Both the L_H_/M ratios and the Brγ equivalent widths in Sy2's areconsistent with the presence of starbursts which are older than those inHII galaxies. A large fraction of the near infrared (<2μm)continuum in Sy1's also appears to be stellar but associated with evenolder starburst activity or normal red giants in the galaxy bulge. Theseresults therefore provide additional support for evolutionary models inwhich Seyfert activity is related to the presence of a black hole whichis formed/fueled by the remnants of a pre-cursor starburst. The originof the non-stellar 2μm continuum in Seyferts and the metallicity ofellipticals are also discussed.
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Asymptotic giant branch stars near the sun
Available red and near-infrared photometry and apparent motions of M, S,and C asymptotic giant branch (AGB) stars in the Bright Star Catalogueare tabulated and discussed. It is shown that the red and near infraredindices normally used for late-type stars are interchangeable except forcarbon stars. The M-type giants are variable with visual amplitudegreater than 0.05 mag. The reddening-free parameter m2 from Genevaphotometry is essentially a temperature parameter for M giants, whilethe reddening-free parameter d is a sensitive detector of blue stellarcompanions. The space density of AGB stars near the sun decreases by afactor of 35 in a temperature range 3800 to 3400 K. Two of the S starsnear the sun were found to have nearly equal space motions and may becomembers of the Arcturus group.
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Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
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New LRS spectra for 356 bright IRAS sources
The low-resolution spectra of all IRAS point sources with F(nu) (12microns) greater than 40 Jy that were not included in the Atlas ofLow-Resolution Spectra are presented. These have been classified intoeight groups based upon the spectral morphology. Silicate emissionspectra and red-continuum spectra associated with H II region sourcesform about 60 percent of this sample. All types of spectra in the LRSAtlas are represented in the sample except for emission-line sources.The sample is used to test a recent classification scheme for IRASsources based on broadband colors. The spectra is used to test a recentclassification scheme for IRAS sources based on broadband colors. Thespectra are consistent with the classifications from the colors in mostcases.
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Radial velocities of southern stars obtained with the photoelectric scanner CORAVEL. III - 790 late-type bright stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&AS...59...15A&db_key=AST
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The radial velocities of 116 southern red stars
Using a photoelectric speedometer based on the radial velocityspectrometer of Griffin (1967), radial velocities of 116 southern redstars, many of them semi-regular variables, were measured. Theinstrument was placed at the Newtonian focus of the 130-inch (4.2-m)camera of the Coude spectrograph of the Mount Stromlo 74-inch (1.88-m)reflector. The stellar spectrum was focused on a mask 50 mm in length,designed to match the spectrum of the M-giant Beta Pegasi. The inversedispersion was 2.5 angstroms per millimeter in the second order. Thewavelength range used (5338-5449 angstroms) was chosen because it isbetween two TiO bands and so suffers less blanketing in M stars. Resultsare tabulated and compared with standard values.
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Determination of proper motions in the region of the association Scorpius OB1
Not Available
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INHABITED SKY
