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Observations of Star-Forming Regions with the Midcourse Space Experiment
We have imaged seven nearby star-forming regions, the Rosette Nebula,the Orion Nebula, W3, the Pleiades, G300.2-16.8, S263, and G159.6-18.5,with the Spatial Infrared Imaging Telescope on the Midcourse SpaceExperiment (MSX) satellite at 18" resolution at 8.3, 12.1, 14.7, and21.3 μm. The large angular scale of the regions imaged (~7.2-50deg2) makes these data unique in terms of the combination ofsize and resolution. In addition to the star-forming regions, twocirrus-free fields (MSXBG 160 and MSXBG 161) and a field near the southGalactic pole (MSXBG 239) were also imaged. Point sources have beenextracted from each region, resulting in the identification over 500 newsources (i.e., no identified counterparts at other wavelengths), as wellas over 1300 with prior identifications. The extended emission from thestar-forming regions is described, and prominent structures areidentified, particularly in W3 and Orion. The Rosette Nebula isdiscussed in detail. The bulk of the mid-infrared emission is consistentwith that of photon-dominated regions, including the elephant trunkcomplex. The central clump, however, and a line of site toward thenorthern edge of the cavity show significantly redder colors than therest of the Rosette complex.
| A photometric catalogue of southern emission-line stars
We present a catalogue of previously unpublished optical and infraredphotometry for a sample of 162 emission-line objects and shell starsvisible from the southern hemisphere. The data were obtained between1978 and 1997 in the Walraven (WULBV), Johnson/Cousins(UBV(RI)c) and ESO and SAAO near-infrared (JHKLM) photometricsystems. Most of the observed objects are Herbig Ae/Be (HAeBe) stars orHAeBe candidates appearing in the list of HAeBe candidates of Théet al. (1994), although several B[e] stars, LBVs and T Tauri stars arealso included in our sample. For many of the stars the data presentedhere are the first photo-electric measurements in the literature. Theresulting catalogue consists of 1809 photometric measurements. Opticalvariability was detected in 66 out of the 116 sources that were observedmore than once. 15 out of the 50 stars observed multiple times in theinfrared showed variability at 2.2 mu m (K band). Based on observationscollected at the European Southern Observatory, La Silla, Chile and onobservations collected at the South African Astronomical Observatory.Tables 2-4 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/380/609
| The 76th Name-List of Variable Stars
We present the next regular Name-List of variable stars containinginformation on 1406 variable stars recently designated in the system ofthe General Catalogue of Variable Stars.
| The η Chamaeleontis Cluster: Origin in the Sco-Cen OB Association
A young, nearby compact aggregate of X-ray-emitting pre-main-sequencestars was recently discovered in the vicinity of η Chamaeleontis. Inthis paper, we further investigate this cluster: its membership, itsenvirons, and its origins. ROSAT High Resolution Imager X-ray data forthe cluster's T Tauri stars show high levels of magnetic activity andvariability. The cluster has an anomalous X-ray luminosity functioncompared to other young clusters, deficient in stars with low butdetectable X-ray luminosities. This suggests that many low-mass membershave escaped the surveyed core region. Photographic photometry from theUSNO-A2.0 catalog indicates that additional, X-ray-quiet members existin the cluster core region. The components of the eclipsing binary RSCha, previously modeled in the literature as post-main sequence (MS)with discordant ages, are shown to be consistent with being coevalpre-MS stars. We compute the Galactic motion of the cluster fromHipparcos data and compare it to other young stars and associations inthe fourth Galactic quadrant. The kinematic study shows that the ηCha cluster, as well as members of the TW Hya association and a newgroup near ɛ Cha, probably originated near the giant molecularcloud complex that formed the two oldest subgroups of the Sco-Cen OBassociation roughly 10-15 Myr ago. Their dispersal is consistent withthe velocity dispersions seen in giant molecular clouds. A large H Ifilament and dust lane located near η Cha has been identified aspart of a superbubble formed by Sco-Cen OB winds and supernova remnants.The passage of the superbubble may have terminated star formation in theη Cha cluster and dispersed its natal molecular gas.
| A revised catalogue of delta Sct stars
An extensive and up-dated list of delta Sct stars is presented here.More than 500 papers, published during the last few years, have beenrevised and 341 new variables have been added to our last list, sixyears ago. This catalogue is intended to be a comprehensive review onthe observational characteristics of all the delta Sct stars known untilnow, including stars contained in earlier catalogues together with othernew discovered variables, covering information published until January2000. In summary, 636 variables, 1149 references and 182 individualnotes are presented in this new list. Tables 1 and 2 will be accessibleonly in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Photometric confirmation of the δ Scuti pulsational variability in the pre-main-sequence Herbig Ae star HD104237
Photometric observations of the Herbig Ae star HD104237 confirm that itis a δ Scuti star. We find two periods, the highest amplitude onehaving a value of 43min. This is only the fourth known pre-main-sequenceδ Scuti star, and the only one with such short periods. Theseimply high-overtone modes which have not yet been investigatedtheoretically. Two of our comparison stars, HD104036 and 105234, arenewly discovered δ Scuti stars.
| The chemical evolution of the solar neighborhood. I - A bias-free reduction technique and data sample
The possible ways of measuring the age-metallicity relation for thegalactic disk in the neighborhood of the sun are discussed. It is shownthat the use of a field star sample chosen on the basis of effectivetemperature introduces a bias which results in a monotonic increase inthe metal abundance of the disk with time. However, if theage-metallicity relation for the disk can be shown to satisfy certaincriteria, the bias introduced in such a sample can be neglected: thegalactic disk apparently satisfies the criteria. It is concluded that asample analyzed through the use of uvby and H(beta) photometry inconjunction with a self-consistent set of theoretical isochronesprovides the least biased, most accurate estimate of the age-metallicityrelation for the disk.
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