The UV BG R photometric system

Basic Reference

Tifft W.G. 1958, Astron. J. 63, 127

Abstract

A system of three-color photoelectric and photographic photometry, resembling the system of W. Becker, has been established and applied. The system utilizes relatively narrow response bands at lambda 3600, lambda 4700, and lambda 6300 (lambda 6000 for photoelectric work). Observations are given which define the characteristics of the system sufficiently to permit application of the system to problems in galactic structure and to permit derivation of nonlinear relations to the Johnson-Morgan system.

The system has been applied to NGC 6910 and NGC 6913 (M29) which are reddened galactic clusters containing early-type stars. The NGC 6913 region shows a real O-B star cluster at a distance of 1.6 kpc which presumably is associated with the P Cygni aggregate. In addition of early-type stars is found near 2.1 kpc. The NGC 6910 region shows a strong concentration of O-B stars at 2.1 kpc, possibly related to the group in the NGC 6913 field, and a distant group at 3.3 kpc. A few observations of another galactic cluster, NGC 663, locate the cluster in the Perseus spiral arm. Most of the four magnitudes of interstellar absorption shown by the B stars in both NGC 6910 and NGC 6913 is found to lie between 1.0 and 1.6 kpc and is presumably the edge of the great rift in cygnus. Beyond 1.6 kpc absorption increases slowly. the variable heavy absorption in the regions provides a good empirical determination of the radio of total to selective absorption for the system used, and indirectly confirms the value A/E=3.0 for the Johnson-Morgan system.

Content

Access to the data and references

Asiago Database on Photometric System (ADPS)

Indices and Parameters

BG, BG-R, UV-BG

Color-free Indices

Q=(UV-BG) - 0.89 (BG-R)

Filters

UV : Corning 5970
Max transmission: 3700 Å
BG : Corning 5030 + Corning 3387
Max transmission: 4700 Å
O : Corning 2434
R : Corning 2418
Max transmission: 6400 Å

Photomultiplier

Transformations

(BG-R) = 1.169 (BG-O)

Basic Relations

Reddening-free index Q
Q = (UV - BG) - [E(UV-BG)/E(BG-R)] (BG - R)
Intrinsic colour index
(BG - R) = 0.320 Q - 0.014
Ratio of total to selective absorption
A(BG) / E(BG-R) = 3.14

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Jean-Claude.Mermilliod@obs.unige.ch
Last update: 21 May 1996