Bibcode
Phillips, J. P.; Martinez Roger, C.; Sanchez Magro, C.; Lazaro Vilchez, C.
Referencia bibliográfica
Astronomy and Astrophysics (ISSN 0004-6361), vol. 161, no. 2, June 1986, p. 257-263.
Fecha de publicación:
6
1986
Número de citas
9
Número de citas referidas
9
Descripción
Near-infrared photometry for the red-giant and horizontal branches in
M4, obtained with the InSb detector mounted on the 1.54-m Tenerife
Infrared flux collector, are presented. The red giant branch is shown to
be displaced from the corresponding trend for M92, confirming earlier
work, and implying an intermediate to high cluster metallicity. The
horizontal branch intersects the RGB at (V - K)0 = 2.0, and continues to
increase an additional two or more magnitudes in K towards the BHB,
indicating a log (HB luminosity/solar luminosity) of about 1.60 for E(B
- V) = 0.46 mag, a value approximately 0.1 mag larger than previous
estimates of selective extinction. Color-color and color-magnitude plots
show similar trends to those of field stars in the regime of H(-)
opacity dominance, though the entire range of cluster stars are seen to
depart from the trend in the B - V, V - K plane due to reduced
short-wave opacities, a departure also seen in the V - B, V - K plane.