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New 3D gas density maps of NaI and CaII interstellar absorption within 300 pc
Aims: We present new high resolution (R > 50 000) absorptionmeasurements of the NaI doublet (5889-5895 Å) along 482 nearbysight-lines, in addition to 807 new measurements of the CaII K (3933Å) absorption line. We have combined these new data withpreviously reported measurements to produce a catalog of absorptionstowards a total of 1857 early-type stars located within 800 pc of theSun. Using these data we have determined the approximate 3-dimensionalspatial distribution of neutral and partly ionized interstellar gasdensity within a distance-cube of 300 pc from the Sun. Methods:All newly recorded spectra were analyzed by means of a multi-componentline profile-fitting program, in most cases using simultaneous fits tothe line doublets. Normalized absorption profiles were fitted by varyingthe velocity, doppler width and column density for all interveninginterstellar clouds. The resulting total column densities were then usedin conjunction with the Hipparcos distances of the target stars toconstruct inversion maps of the 3D spatial density distribution of theNaI and CaII bearing gas. Results: A plot of the equivalent widthof NaI versus distance reveals a wall of neutral gas at ~80 pc that canbe associated with the boundary wall to the central rarefied LocalCavity region. In contrast, a similar plot for the equivalent width ofCaII shows no sharply increasing absorption at 80 pc, but instead weobserve a slowly increasing value of CaII equivalent width withincreasing sight-line distance sampled. Low values for the volumedensity of NaI (nNaI < 10-9 cm-3)are generally found within 50 pc of the Sun, whereas values in the range10-8 >nNaI > 10-10cm-3 are found for sight-lines with distance >300 pc. Bothhigh and low values of the volume density of CaII (nCaII) arefound for sight-lines <30 pc, dependent on whether local gascloudlets are encountered. For distances >100 pc a value ofnCaII ~ 10-9 cm-3 is typical for mostsight-lines, indicating that the distribution of CaII bearing gas isfairly uniform throughout the general ISM. Our three maps of the 3Dspatial distribution of local neutral NaI absorption extend and improveupon the accuracy of similar maps initially presented by Lallement etal. (2003, A&A, 411, 447), with many new neutral interstellar gasfeatures (such as low neutral density gas tunnels) in the localinterstellar medium now being revealed for the first time. The maps ofthe 3D distribution of partially ionized CaII gas are the first of theirkind to be presented and exhibit many spatial similarities to those oftheir equivalent NaI absorption maps. A major finding from both sets ofmaps is that the low density Local Cavity region is surrounded by ahighly fragmented wall of higher density NaI and CaII gas clouds. Theappearance of this broken boundary may be linked to the purportedexplosive origin of the Local Cavity. Maps of the distribution of CaIIgas density reveal the presence of many partially ionized low densitycloudlets that reside within the Local Cavity, and their newly derived3D spatial contours confirm previous observations of the local gas byRedfield & Linsky (2008, ApJ, 673, 283). Both the NaI and CaII mapssuggest that the Local Cavity may contain several low densitysub-cavities that are surrounded by thin filaments of neutral and/orpartially ionized gas. However, further observations will be required toconfirm the existence of a collection of cell-like interstellarcavities. The new maps also reveal several sight-lines where CaIIabsorption is high and the corresponding NaI absorption is low, andvice-versa. Such regions are probably influenced by the effects of thelocal stellar ionization field which can significantly affect theobserved NaI/CaII column density ratio. Plots of this ratio as afunction of distance for stars located near to the galactic plane showvalues in the range 0.1 to 1.0 for sight-lines with distances <80 pc.However, ratio values of between 0.5 and 20 are typical for more distantsight-lines. The highest values of the NaI/CaII ratio are found towardsl ~ 150° in the direction of the Taurus dark clouds, with ratiovalues in the narrower range of 0.1 to 5 being found in galacticquadrant 3.Partly based on observations collected at the European SouthernObservatory, La Silla, Chile.Full Table 1 is only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/510/A54
| FAUST observations of ultraviolet sources in the directions of NGC 4038-39 and 6752
Analysis of ultraviolet (UV) observations with the FAUST shuttle-bornetelescope toward the Antennae and NGC 6752 celestial regions resulted inthe detection of 46 and 221 candidate sources respectively, for asignal-to-noise ratio of 8. We discuss the source detection process andthe identification of UV sources with optical counterparts. Usingcorrelations with existing catalogues, we present reliableidentifications for approximately 60 per cent of the sources. We findthat most identified objects are B, A and F stars. The remainingidentified objects are galaxies, a white dwarf in a binary system, andtwo K-type stars. Nearly all of the remaining unidentified objects haveassigned optical counterparts but, lacking additional information, wegive these only as best estimates. With help from new diagnosticdiagrams, we suggest that these unclassified objects are main-sequence(or giant) stars within the local spiral arm or halo; or other hotevolved objects within the local spiral arm. We discuss the nature ofthe objects found and compare our results with those predicted fromspectral and Galactic models.
| Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
| 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%.
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משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | טווס |
| התרוממות ימנית: | 19h04m06.01s |
| סירוב: | -63°47'04.6" |
| גודל גלוי: | 7.69 |
| תנועה נכונה: | 17.9 |
| תנועה נכונה: | -19.2 |
| B-T magnitude: | 7.641 |
| V-T magnitude: | 7.686 |
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