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Low-Resolution Spectroscopy of Hot Post-AGB Candidates II. LS, LSS, LSE Stars and Additional IRAS Sources
Hot (OB) post-asymptotic giant branch (post-AGB) stars are immediateprogenitors of planetary nebulae (PNe). Very few hot post-AGB stars areknown. Detecting new hot post-AGB candidates and follow-upmultiwavelength studies will enable us to further understand theprocesses during the post-AGB evolution that lead to the formation ofPNe. Case-Hamburg OB star surveys and their extension (LS, LSS, and LSEcatalogues) and IRAS (point source) catalogues are good sources fordetecting new hot post-AGB candidates from low-resolution spectroscopy.Spectral types are determined from low-resolution optical spectra of 44stars selected from the LS, LSS, and LSE catalogues. Unlike the starsmentioned in the first paper, the stars discussed in this paper wereselected using criteria other than positional coincidence with an IRASsource with far-IR (IRAS) colours similar to post-AGB supergiants andplanetary nebulae. These included high galactic latitude, spectral typesof O, B, A supergiants, emission lines in the spectrum and knownspectral peculiarity. From the present study we find that LSS 1179, LSS1222, LSS 1256, LSS 1276, LSS 1341, LSS 1394, LSS 2241, LSS 2429, LSS4560, LSE 3, LSE 16, LSE 42, and LSE 67 to be new hot post-AGBcandidates. Further studies of these candidates are needed.
| New Estimates of the Solar-Neighborhood Massive Star Birthrate and the Galactic Supernova Rate
The birthrate of stars of masses >=10 Msolar is estimatedfrom a sample of just over 400 O3-B2 dwarfs within 1.5 kpc of the Sunand the result extrapolated to estimate the Galactic supernova ratecontributed by such stars. The solar-neighborhood Galactic-plane massivestar birthrate is estimated at ~176 stars kpc-3Myr-1. On the basis of a model in which the Galactic stellardensity distribution comprises a ``disk+central hole'' like that of thedust infrared emission (as proposed by Drimmel and Spergel), theGalactic supernova rate is estimated at probably not less than ~1 normore than ~2 per century and the number of O3-B2 dwarfs within the solarcircle at ~200,000.
| Catalog of Galactic OB Stars
An all-sky catalog of Galactic OB stars has been created by extendingthe Case-Hamburg Galactic plane luminous-stars surveys to include 5500additional objects drawn from the literature. This work brings the totalnumber of known or reasonably suspected OB stars to over 16,000.Companion databases of UBVβ photometry and MK classifications forthese objects include nearly 30,000 and 20,000 entries, respectively.
| UBV beta Database for Case-Hamburg Northern and Southern Luminous Stars
A database of photoelectric UBV beta photometry for stars listed in theCase-Hamburg northern and southern Milky Way luminous stars surveys hasbeen compiled from the original research literature. Consisting of over16,000 observations of some 7300 stars from over 500 sources, thisdatabase constitutes the most complete compilation of such photometryavailable for intrinsically luminous stars around the Galactic plane.Over 5000 stars listed in the Case-Hamburg surveys still lackfundamental photometric data.
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