The Bappu photometric system

Basic Reference

Bappu M.K.V., Chandra S., Sanwal N.B., Sinvhal S.D. 1962, MNRAS 123, 521


Photoelectric determinations of Hgamma absorption line intensity have been made of stars in selected clusters and associations as well as in the general galactic field. Interference filters having a width at half intensity of 45 Å were used to isolate spectral regions centred on 4280 Å, Hgamma and 4410 Å. The gamma indices derived, which represent a measure of the Hgamma absorption, can be used in conjunction with unreddened values of either (U-B) or (B-V) for spectral and luminosity class determinations of stars in the spectral range O6 to A0. The separation of age loci is shown to exist on gamma, (U-B)o diagrams of clusters and associations having different ages. A gamma, Mv calibration for the young, or less evolved stars, has been derived. Tests of such a calibration have been made on the Orion association and NGC 2362. The distance moduli thus obtained are in good agreement with the values derived from the colour magnitude arrays.


Access to the data and references

Asiago Database on Photometric System (ADPS)

Indices and Parameters



Baird Atomic interference filters, at 4280 Å, Hgamma and 4410 Å Half width 45 Å.


RCA 1P21
Please, send your commentsto
Last update: 13 September 2002