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The stellar composition of the star formation region CMa R1 - I. Results from new photometric and spectroscopic classifications
A new photometric and spectroscopic survey of the star formation region(SFR) CMa R1 is described. In a sample of 165 stars brighter than 13thmag, 88 stars were found to be probable members of the SFR. They aredefined as early-type stars with E(B-V)>=0.16mag, which correspondsto a distance of about 1kpc. 74 of the probable members are B stars. 19stars are possibly associated with an IRAS point source. We derive amost probable distance of 1050+/-150pc to the association. It appearsthat about 80 candidate members are pre-main-sequence stars with ageslower than 6 million years, while the main sequence extends over6.0-7.6mag, which is consistent with star formation starting about 8million years ago and continuing until at least half a million yearsago. Two bright B stars in the association (GU CMa and FZ CMa) seem tobe much older and probably do not originate from the same star formationepisode. The star formation efficiency appears to increase roughlymonotonically with time up to half a million years ago. From our data,we conclude that only a minor fraction of the stars has been createdthrough the scenario suggested by Herbst & Assousa, in which themembers of CMa R1 form by compression of ambient material by a supernovashock wave. An extensive search for candidate members with Hαemission did not reveal new Herbig Ae/Be candidates, so that the numberof stars in this class seems to be limited to four: Z CMa, LkHα218, LkHα 220 and possibly HD 53367.
| Speckle Interferometry at the US Naval Observatory. IV.
The results of 1314 speckle interferometric observations of 625 binarystars, ranging in separation from 0.2" to 5.2" with a limiting secondarymagnitude of V=11, are tabulated. These observations were obtained usingthe 66 cm refractor at the US Naval Observatory in Washington, DC, withan intensified CCD detector. This is the fourth in a series of paperspresenting measures obtained with this equipment and covers the period1997 January 1 through December 31. Random errors for all measures areestimated to be 18 mas in separation and 0.57d/rho in position angle,where rho is the separation in arcseconds.
| Speckle Interferometry at the US Naval Observatory. III.
Position angles and separations resulting from 2578 speckleinterferometric observations of 590 binary stars are tabulated. This isthe third in a series of papers presenting measures obtained using the66 cm refractor at the US Naval Observatory in Washington, DC, andcovers the period from 1995 June through 1996 December. Program starsrange in separation from 0.2" to 4.3", with a limiting magnitude ofV=11. Random errors are estimated to be 17.0 mas in separation and0.56d/rho in position angle, where rho is the separation in arcseconds.These are the first results acquired using an improved intensified CCDdetector. The new detector, in concert with an intensity-filteringtechnique applied in software, has permitted a 1 mag increase in dynamicrange, to 3.5 mag, for pairs separated by about 2". The instrumentationand calibration are briefly described, with an emphasis on thecharacteristics of the new detector. The software filter used toincrease the dynamic range is also described.
| Investigation of a Milky Way field in Canis Major
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974AJ.....79.1022C&db_key=AST
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