Cousins Photometry and Temperatures for the Hyades, Coma, NGC 752, Praesepe, and M67

Abstract

In this paper, new Cousins VRI data are presented for NGC 752 and Praesepe, and new and extant data are combined into an augmented database for M67. For those three clusters, catalogs containing Cousins VRI photometry, reddening-corrected values of (V À K ) J , and temperatures are produced. The same is done for Coma by using both previously published and newly derived Cousins photometry. An extant set of catalogs for the Hyades is updated to include V magnitudes and values of (R À I ) C that were published after the original catalogs appeared. Finally, M67 V magnitudes published previously by Sandquist are corrected for an effect that depends on location on the face of the cluster. The corrected data and values of (V À I ) C given by Sandquist are then set out in a supplementary catalog. Data files containing all of these catalogs are deposited in the CDS archives. To assess the quality of the data in the catalogs, the consistency of extant Cousins VRI databases is tested by performing analyses with the following features: (1) quantities as small as a few millimags are regarded as meaningful; (2) statistical analysis is applied; (3) no use is made of data other than VRI measurements and comparable results; (4) no inferences are drawn from colormagnitude comparisons; (5) pertinent data that have not been included previously are analyzed; and (6) results based on direct comparisons of stellar groups at the telescope are featured. In this way, it is found that our updated M67 color data and those of Sandquist are on the E region zero point. In contrast, values of (V À I ) C from Montgomery and collaborators are found to be too red by 27 AE 3 mmag, with an even larger offset being likely for unpublished data from Richer and his collaborators. Zero-point tests of our Cousins VRI colors for Coma, Praesepe, and NGC 752 are also satisfactory. Scale factor tests of the M67 colors are performed, and a likely scale factor error in the Montgomery et al. colors is found. However, it appears at present that the scale factors of our M67 colors and those of Sandquist are satisfactory. For the most part, zero-point tests of the assembled V magnitudes are also satisfactory, although it is found that further work on the V magnitudes for Praesepe and M67 would be useful. To put these results in perspective, it is pointed out that photometric tests that are satisfactory at the few-millimag level have been published for some two decades and so are not appearing for the first time in this paper.

Tests of Broadband Photometric Consistency for Standard Stars, the Hyades, and M67

“…Small and precise values of s are therefore expected, and in fact s is found to be −0.37 ± 0.23 for (V − R) C and 0.0 ± 0.65 for (R − I ) C . Since neither value of s differs from zero by at least twice its standard error, we conclude with some confidence that the measurements published by Taylor et al (2008) have the same scale factor as the SAAO data. Presumably that scale factor is correct, and the scale factor problem described above can be attributed to the Montgomery et al (1993) data.…”

“…One of these concerns the character of extant V (RI) C photometry for M67. In this case, we augment a discussion given recently by Taylor et al (2008). A second problem concerns the zero point of Hyades B − V photometry, and it was discussed but not solved in Paper I.…”

“…Here, the topic of interest is the relationship between the new SAAO data and a set of databases considered by Taylor et al (2008). In Sections 5.3 and 6 of their paper, those authors discussed the relationship between a new M67 database they had presented, extant results from Montgomery et al (1993) and other sources, and the SAAO data given in this paper.…”

The Benchmark Cluster Reddening Project. Iv. A Statistical Test for Nonuniform Reddening in the Pleiades

“…b "C89" is Cardelli et al (1989), "T86" is Taylor (1986), "TJ96" is Taylor & Joner (1996), "TJ05" is Taylor & Joner (2005), "TJ06" is , and "T08" is Taylor et al (2008). c The reddening ratio is given in footnote 7 of Table 4 of Taylor (1986).…”

“…These values are not adopted, but their zero point is used to test the zero points of (R − I) C data transformed from other sources. g See Table 2 of Taylor et al (2008). h Data from Stauffer (1982) and subsequent papers in that series are not used because almost all of those data apply for cooler stars than those considered here.…”