Lacerta OB1 Revisited
This investigation utilizes precise uvby? photometry and therecently recalculated Hipparcos data to provide an improved homogeneousdistance scale for the apparent groups of young stars in Lacerta. Allexisting uvby? photometry for stars earlier than A0-type in a20°×20° field centered at l=100°, b=-15° iscollated and the individual stellar distances and color excesses areobtained. The association Lac OB1 is reliably identified as a verycompact young group of 12 bright stars at an average distance of520±20(s.e.) pc. The available radial velocity and proper motionmeasurements strongly support the impression that the group is real. Thestars in the northeast part of Lacerta seem not to represent a physicalgroup, but rather a layer of field stars spread between 140 and 400 pcand extending farther than that toward l˜104°. An estimate of678±50(s.e.) pc of the distance to the open cluster NGC 7243 isobtained based on the brightest cluster members. The calculateddistances are based on a well-tested procedure, and thus represent aclarification over the range of distance existing in the literature forthe bright stars in the Lacerta field. Although a better agreement isnow evident between the photometric distances and the recalculatedHipparcos parallaxes in comparison to the original Hipparcos data,discrepancies still exist for this particular field.
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The Herbig Ae-Star LKH-ALPHA:233 and a Related Compact Region of Star Formation
Not Available
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Radial velocity measurements. II - Ground-based observations of the program stars for the HIPPARCOS satellite
New radial velocities for 446 stars of magnitude 9.0 or brighter in 1616-sq-deg fields of the Northern Hemisphere are determined by automaticPDS measurement of 80-A/mm-dispersion spectra obtained at theObservatoire de Haute Provence using a 17-cm-diameter objective prism.The fields were selected to provide data for the input catalog of theESA Hipparcos astrometric satellite. The measurement techniques andprecision are discussed, and the results are presented in extensivetables and graphs.
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Photometry of stars in the uvgr system
Photoelectric photometry is presented for over 400 stars using the uvgrsystem of Thuan and Gunn. Stars were selected to cover a wide range ofspectral type, luminosity class, and metallicity. A mean main sequenceis derived along with reddening curves and approximate transformationsto the UBVR system. The calibration of the standard-star sequence issignificantly improved.
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Four-color photometry for the association Lac OB1.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976PASP...88..930C&db_key=AST
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Spectral classification of stars in Lac OB1
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976AJ.....81.1120G&db_key=AST
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Evidence of helium abundance differences between young groups of stars
Seven groups of B-type stars - Sco-Cen, NGC 6231, LacOBI,OriOBIb, h + chi Per, CepOBIII, and field stars - wereinvestigated photoelectrically to determine whether helium abundance isuniform in the solar neighborhood and in a region of the spiral arm ofthe Galaxy. Observations were performed using an echelle spectrometer inthe narrow band index of the I (4026) of the He I-4026 line. Amodel-atmosphere analysis of I (4026) and the beta index of the H betaline shows that in the spectral range B O-B 2, the relation between I(4026) and beta is insensitive to differences in the surface gravity butsensitive to differences in the helium to hydrogen ratio. It is foundthat stars in the two groups most distant from the sun - h + chi Per andCepOBIII - have a lower helium abundance than stars in the solarneighborhood.
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Spectral types in the Lac OB1 association.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976PASP...88..141L&db_key=AST
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Classifications of Some Stars in the Lacertae OBI Association
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973PASP...85..676A&db_key=AST
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Hβ Photometry for the Association i Lacertae.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1961ApJ...133..860C&db_key=AST
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A Study of the i Lacertae Association.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1959ApJ...129..601H&db_key=AST
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INHABITED SKY
