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CaII K interstellar observations towards early-type disc and halo stars - distances to intermediate- and high-velocity clouds
We compare existing high spectral resolution(R=λ/Δλ~ 40000) CaII K observations(λair= 3933.66 Å) towards 88 mainly B-typestars, and new observations taken using the Intermediate dispersionSpectrograph and Imaging System (ISIS) on the William Herschel Telescopeat R~ 10000 towards three stars taken from the Palomar-Green Survey,with 21-cm HI emission-line profiles, in order to search for opticalabsorption towards known intermediate- and high-velocity cloudcomplexes. Given certain assumptions, limits to the gas phase abundanceof CaII are estimated for the cloud components. We use the data toderive the following distances from the Galactic plane (z). (i)Tentative lower z-height limits of 2800 and 4100 pc towards complex Cusing lack of absorption in the spectra of HD341617 and PG0855+294,respectively. (ii) A weak lower z-height of 1400 pc towards complexWA-WB using lack of absorption in EC09470-1433 and a weak lower limit of2470 pc using lack of absorption in EC09452-1403. (iii) An upperz-height of 2470 pc towards a southern intermediate-velocity cloud (IVC)with vLSR=-55 km s-1 using PG2351+198. (iv)Detection of a possible IVC in CaII absorption at vLSR=+52 kms-1 using EC20104-2944. No associated HI in emission isdetected. At this position, normal Galactic rotation predicts velocitiesof up to ~+25 km s-1. The detection puts an upper z-height of1860 pc to the cloud. (v) Tentative HI and CaII K detections towards anIVC at ~+70 km s-1 in the direction of high-velocity cloud(HVC) complex WE, sightline EC06387-8045, indicating that the IVC may beat a z-height lower than 1770 pc. (vi) Detection of CaII K absorption inthe spectrum of PG0855+294 in the direction of IV20, indicating thatthis IVC has a z-height smaller than 4100 pc. (vii) A weak lowerz-height of 4300 pc towards a small HVC with vLSR=+115 kms-1 at l, b= 200°, + 52°, using lack of absorption inthe CaII K spectrum of PG0955+291.
| CaII K interstellar observations towards early-type disc and halo stars
We present high-resolution (R=λ/Δλ~ 40000) CaII Kinterstellar observations (λair= 3933.66Å)towards 88 mainly B-type stars, of which 74 are taken from theEdinburgh-Cape or Palomar-Green surveys, and 81 have |b| > 25°.The majority of the data come from previously existing spectroscopy,although also included are 18 new observations of stars with echellespectra taken with UVES on the Very Large Telescope UT2 (Kueyen). Some49 of the sample stars have distance estimates above the Galactic plane(|z|) >= 1 kpc, and are thus good probes of the halo interstellarmedium. Of the 362 interstellar Ca K components that we detect, 75 (21per cent) have absolute values of their LSR velocity values exceeding 40km s-1. In terms of the deviation velocity for the sightlineswith distance estimates, 46/273 (17 per cent) of components havevelocity values exceeding those predicted by standard Galactic rotationby more than 40 km s-1. Combining this data set with previousobservations, we find that the median value of the reduced equivalentwidth (REW) of stars with |z| >= 1 kpc (EW×sin|b|) is ~115mÅ (n= 80), similar to that observed in extragalactic sightlinesby Bowen. Using data of all z distances, the REW at infinity is found tobe ~130 mÅ, with the scaleheight (l) of the CaII K column densitydistribution being ~800 pc (n= 196) and reduced column density atinfinity of log[N(CaII K) cm-2]~12.24. This implies that ~30per cent of CaII K absorption occurs at distances exceeding ~1 kpc. Fornine sightlines with distance exceeding 1 kpc and with a companionobject within 5°, we find that all but two have values of CaIIreduced equivalent width the same to within ~20 per cent, when the REWof the nearest object is extrapolated to the distance of the further ofthe pair, and assuming l= 800 pc. For 29 of our sightlines with |z|>= 1 kpc and a HI detection from the Leiden-Dwingeloo survey(beamsize of 0.5°), we find log(N(CaII K)/N(HI)) ranging from -7.4to -8.4. Values of the CaII K abundance relative to neutral hydrogen(log[N(CaIIK)cm-2]-log[N(HI)cm-2]) are found to bemore than ~0.5dex higher in stars with distances exceeding ~100 pc, whencompared with the (log[N(CaII K) cm-2]-log[N(Htot) cm-2]) values found in nearbysightlines such as those in Wakker & Mathis (2000). Finally, stellarCaII K equivalent widths of the sample are determined for 26 objects.
| Metallicity estimates for A-, F-, and G-type stars from the Edinburgh-Cape Blue Object Survey
The Edinburgh-Cape Blue Object Survey is an ongoing project to identifyand analyse a large sample of hot stars selected initially on the basisof photographic colours (down to a magnitude limit \fontshape{it}{B}\sim 18.0) over the entirehigh-Galactic-latitude southern sky, and then studied with broad-bandUBV photometry and medium-resolution spectroscopy. Due to unavoidableerrors in the initial candidate selection, stars that are likelymetal-deficient dwarfs and giants of the halo and thick-disc populationsare inadvertently included, yet are of interest in their own right. Inthis paper we discuss a total of 206 candidate metal-deficient dwarfs,subgiants, giants, and horizontal-branch stars with photoelectriccolours redder than (\fontshape{it}{B}-\fontshape{it}{V})0=0.3, andwith available spectroscopy. Radial velocities, accurate to~10-15kms-1, are presented for all of these stars.Spectroscopic metallicity estimates for these stars are obtained using arecently recalibrated relation between CaII K-line strength and(\fontshape{it}{B}-\fontshape{it}{V})0 colour.The identification of metal-poor stars from this colour-selectiontechnique is remarkably efficient, and competitive with previous surveymethods. An additional sample of 186 EC stars with photoelectric coloursin the range -0.4\leq(\fontshape{it}{B}-\fontshape{it}{V})0<0.3, composedprimarily of field horizontal-branch stars and other, higher gravity, A-and B-type stars, is also analysed. Estimates of the physical parametersTeff, logg, and [Fe/H] are obtained for cooler members ofthis subsample, and a number of candidate RR Lyrae variables areidentified.
| FAUST observations in the Fourth Galactic Quadrant*
We analyse UV observations with FAUST of four sky fields in the generaldirection of the Fourth Galactic Quadrant, in which we detect 777 UVsources. This is ~50 per cent more than detected originally by Bowyer etal. We discuss the source detection process and the identification of UVsources with optical counterparts. For the first time in this project weuse ground-based objective-prism information for two of the fields, toselect the best-matching optical objects with which to identify the UVsources. Using this, and correlations with existing catalogues, wepresent reliable identifications for ~75 per cent of the sources. Mostof the remaining sources have assigned optical counterparts but, lackingadditional information, we offer only plausible identifications. Wediscuss the types of objects found, and compare the observed populationwith predictions of our UV Galaxy model.
| Rotational velocities of B-type stars from the Edinburgh-Cape survey
The projected rotational velocity distribution for a sample of 34 highGalactic latitude B-type stars from the Edinburgh-Cape Faint Blue ObjectSurvey is presented to investigate the evolutionary status of the groupas a whole. Statistical analyses of the distribution show it to besimilar to that expected if the sample contained mainly normalPopulation i early B-type stars, although a contamination of up to 20 %by evolved stars cannot be ruled out. This implies that a large fractionof the sample consists of normal Population i B-type stars similar tothose found in the Galactic disk. Possible mechanisms explaining thepresence of these stars in the halo are briefly discussed.
| High-resolution spectroscopic observations of B-type stars from the Edinburgh-Cape survey
High-resolution spectroscopy has been obtained for 25 high-latitudestars identified from the Edinburgh-Cape faint blue object survey ashaving B-type spectra. Five objects are found to be subluminous(subdwarf or horizontal branch), chemically peculiar, or later thanB-type. We present model atmosphere analyses for the other 20 objects,and conclude that 17 stars exhibit stellar properties typical of youngB-type dwarfs. Photospheric abundances determined for a subset of starswere also found to be consistent with a Population I composition.Furthermore, we believe EC 05229-6058 to be an evolved object currentlyon the post-asymptotic giant branch phase, whilst EC 20411-2704 and11074-2912 are consistent with being zero-age horizontal branch andpost-blue horizontal branch objects respectively. A kinematic analysisof the normal stars implies that all could have formed in, and have beensubsequently ejected from, the Galactic disc.
| A catalog of far-ultraviolet point sources detected with the fast FAUST Telescope on ATLAS-1
We list the photometric measurements of point sources made by the FarUltraviolet Space Telescope (FAUST) when it flew on the ATLAS-1 spaceshuttle mission. The list contains 4698 Galactic and extragalacticobjects detected in 22 wide-field images of the sky. At the locationssurveyed, this catalog reaches a limiting magnitude approximately afactor of 10 fainter than the previous UV all-sky survey, TDl. Thecatalog limit is approximately 1 x 10-14 ergs A sq cm/s,although it is not complete to this level. We list for each object theposition, FUV flux, the error in flux, and where possible anidentification from catalogs of nearby stars and galaxies. Thesecatalogs include the Michigan HD (MHD) and HD, SAO, the HIPPARCOS InputCatalog, the Position and Proper Motion Catalog, the TD1 Catalog, theMcCook and Sion Catalog of white dwarfs, and the RC3 Catalog ofGalaxies. We identify 2239 FAUST sources with objects in the stellarcatalogs and 172 with galaxies in the RC3 catalog. We estimate thenumber of sources with incorrect identifications to be less than 2%.
| A Search for Beta-Cephei Type Variability in a Sample of Intermediate Galactic Latitude to High Galactic Latitude B-Type Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994MNRAS.267.1103H&db_key=AST
| First results from the Edinburgh-Cape faint blue object survey - Normal stars at high galactic latitudes
A simple analysis using low-dispersion Reticon spectroscopy andStromgren photometry is presented for a sample of 20 apparently normalearly-type stars detected in the Edinburgh-Cape faint blue object surveyof high galactic latitudes. Four stars are not normal, showing highgravity or helium abundance anomalies; 12 stars appear to be at moderatedistances from the galactic plane and four stars have derivedz-distances greater than about 5 kpc. The sample was selected from 33survey fields completed to B = 16.5 mag and indicates that the totalgalactic population of 'very high-z' B stars is only of the order100-1000. The Dyson and Hartquist (1983) model for the formation of suchobjects by cloudlet-cloudlet collisions within high-velocity cloudscannot therefore be ruled out on the basis of star formation rates.
| The galactic reddening law - The evidence from uvby-beta photometry of B stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&A...142..189T&db_key=AST
| Four-colour and H beta photometry of southern B stars at high galactic latitudes
Four-color and H beta photometry has been obtained for 105 early-type HDstars with galactic latitudes less than -45 deg. They are mostly late Bstars of luminosity class V to III. Two new Am stars and several Ap orBp stars are detected photometrically. Absolute magnitudes aredetermined from the photometry and from MK types where available. Theinterstellar reddening of many of the more distant stars is very small,suggesting either the existence of undetected peculiar stars in thesample or that there are areas of effectively zero reddening at highsouthern galactic latitudes.
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Dades d'Observació i Astrometria
| Constel·lació: | Reticulum |
| Ascensió Recta: | 03h47m20.71s |
| Declinació: | -58°04'36.3" |
| Magnitud Aparent: | 9.839 |
| Moviment propi RA: | 4.4 |
| Moviment propi Dec: | 21.6 |
| B-T magnitude: | 9.804 |
| V-T magnitude: | 9.837 |
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