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An Einstein Observatory SAO-based catalog of B-type stars
About 4000 X-ray images obtained with the Einstein Observatory are usedto measure the 0.16-4.0 keV emission from 1545 B-type SAO stars fallingin the about 10 percent of the sky surveyed with the IPC. Seventy-fourdetected X-ray sources with B-type stars are identified, and it isestimated that no more than 15 can be misidentified. Upper limits to theX-ray emission of the remaining stars are presented. In addition tosummarizing the X-ray measurements and giving other relevant opticaldata, the present extensive catalog discusses the reduction process andanalyzes selection effects associated with both SAO catalog completenessand IPC target selection procedures. It is concluded that X-rayemission, at the level of Lx not less than 10 exp 30 ergs/s, is quitecommon in B stars of early spectral types (B0-B3), regardless ofluminosity class, but that emission, at the same level, becomes lesscommon, or nonexistent, in later B-type stars.
| Dust ring around Lambda Orionis
Sky maps of a 12 deg x 12 deg region obtained by IRAS reveal a dust ringwhich has a diameter of about 9 deg and is centered on the H II region S264 and its exciting star, Lambda Orionis. The 60/100 micron colortemperature in the ring with an assumed dust emissivity law nu exp 1.5is on average 25 K. The luminosity in the IRAS wavelength range and thetotal far-infrared luminosity for the ring are 38,000 and 63,000 solarluminosities, respectively. The radiation field responsible for theheating of dust in the ring contains an enhanced UV component with anenergy density 2 to 3 times as large as that of the general interstellarradiation field. This enhancement of the UV component is ascribed to theO star Lambda Ori and several other early B stars. A careful analysis ofthe energetics of the ring shows that its total infrared luminosity canbe explained by the energy supply from the Lambda Ori OB association, HD34989 and the interstellar radiation field.
| Absorption in and around the H II region Lambda Orionis
Star counts were made, using the Cosmos measuring machine, in the fieldof the H II region excited by Lambda Orionis. These confirm thepreviously identified shell of absorption at the edge of the ionizedregion as well as a central core of absorption, and indicate thepossible presence of a second shell of absorption within the H IIregion, perhaps associated with the He II zone. The absorption radiallythrough the outer shell is 0.15 mag. Through the inner shell thisabsorption is 0.15 mag and along a radius of the central core, 0.35 mag.The mass of the dust in the outer shell, said to be formed by expansionof the H II region, is 2000 solar masses. Only 30 solar masses of dustare left in the central core.
| Photoelectric distances of 461 Northern OB-stars and galactic structure from Hγ- luminosities Author: Beer, A.
Abstract image available at:http://adsabs.harvard.edu/abs/1964MNRAS.128..261B
| A Catalogue of H II Regions.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1959ApJS....4..257S&db_key=AST
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Observation and Astrometry data
| Constellation: | Ωρίων |
| Right ascension: | 05h36m04.19s |
| Declination: | +09°49'55.0" |
| Apparent magnitude: | 9.085 |
| Proper motion RA: | 0.4 |
| Proper motion Dec: | 0.8 |
| B-T magnitude: | 9.065 |
| V-T magnitude: | 9.084 |
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