Photometric Absolute Magnitudes Research Articles

Absolute Magnitudes of Early-type Supergiants from uvbyβ Photometry and Parallax Data

We combine Strömgren–Crawford uvbyβ photometry with Gaia-DR2 parallaxes for a sample of 880 supergiants of O-B9 spectral types to explore the potential of these data in providing physical parameters of such stars. We obtained reddening corrections and photometric absolute magnitudes via the existing uvbyβ calibrations. We calculated Gaia-based absolute magnitudes applying individual photometric reddening corrections for each star. The uvbyβ photometry is particularly useful in this case, since it provides color excess independent of spectral classification, thus overcoming possible MK classification inconsistencies. After evaluating and correcting the effect of luminosity class mis-classifications on the photometric absolute magnitudes, we found a reasonable agreement between the photometric and Gaia-based absolute magnitudes for this sample. At this point, the color–magnitude MV versus (b − y)0 diagrams based on photometry and Gaia show slight discrepancies, which have to be addressed in the light of the next Gaia data releases. The derived precise reddening corrections should further help to refine the physical parameters of these stars and address their connection to OB-associations and regions of star formation.

On the absolute magnitudes of RV Tauri variables.

view Abstract Citations (16) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the absolute magnitudes of RV Tauri variables. Barnes, T. G., III ; DuPuy, D. L. Abstract Recently DuPuy suggested that RV Tauri variables show evidence for 1.5 mag of nearly neutral extinction in the visual region. The suggestion is based upon an apparent discrepancy between photometric absolute magnitudes and spectroscopic luminosity classes. We have reexamined the evidence and conclude that no discrepancy exists if the surface gravities of RV Tauri variables are as given by the current calibration of MK luminosity classes. In this case, the photometrically determined period-luminosity relation given by DuPuy correctly represents the luminosities of the variables, and no neutral extinction in the circumstellar envelopes is required. Subject headings: circumstellar shells - luminosities RV Tauri stars Publication: The Astrophysical Journal Pub Date: September 1975 DOI: 10.1086/153796 Bibcode: 1975ApJ...200..364B full text sources ADS | data products SIMBAD (6)

The Temperatures, Abundances and Gravities of F Dwarf Stars

Theoretical colours, computed using laboratory line data and model stellar atmospheres, have been used to interpret the colours of about 150 F and early G dwarfs. Effective temperatures have been derived from the H β index and from R–I , abundances have been obtained from m1 and b–y and gravities have been obtained from c1 and b–y . The effective temperatures and gravities are in good agreement with values obtained from spectral scans. Much less observing time is required to obtain the colours than to obtain scans and the reduction procedure is also far simpler. Absolute magnitudes have been obtained from the effective temperatures and the gravities, the latter being used with assumed stellar masses to yield radii. The root mean square difference between photometric absolute magnitudes and trigonometric ones is about 0.4 magnitudes. The present results provide theoretical justification for the empirical formulae given by Crawford and by Strömgren for the determination of absolute magnitudes and abundances from uvby photometry.