The benchmark cluster reddening project. III. A comparison of reddening values derived from F and K stars in NGC 752.
Abstract (from CDS):
A protocol for reddening analysis developed in previous papers in this series is reviewed here and applied to NGC 752. The protocol includes (1) detailed scrutiny of the histories of reddening determinations for program clusters, (2) adherence to statistical norms, (3) quality control of all reddening techniques, (4) a primary focus on techniques with limited metallicity sensitivity, (5) zero-point control of source data, (6) use of the solar neighborhood to establish a zero point for reddening values, (7) use of a standard permitting meaningful quantities to be as small as a few millimagnitudes, and (8) rejection of ad hoc data assessments. After certain published results are set aside, it is found that a reddening value derived for F stars by using a technique that is insensitive to blanketing disagrees by about 0.04 mag with a value derived for K giants by using DDO photometry. This disagreement does not appear to be an artifact of the use of questionable data, and it persists if additional techniques are considered. Partly because two comparable reddening results for K giants are afterward found to disagree with each other, the problem is attributed to a blanketing effect (with an unknown source) on the reddening values derived for the K giants. Pending a final resolution of that problem, the adopted value of E(B-V) for the cluster (44±3.4 mmag) is based solely on the initial F-star analysis. A discussion of the potential usefulness of small standard errors like the one derived here for E(B-V) is given. In a parallel investigation, it is found that no definitive value of [Fe/H] can be assigned to NGC 752 at present because a statistically significant disagreement between two published high-precision metallicities is detected.
open clusters and associations: individual (NGC 752) - Stars: Abundances
Table 9 : stars H NNN are NGC 752 NNN.