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

Abstract

New South African Astronomical Observatory (SAAO) BV(RI) C measurements of 19 Hyades stars and 11 M67 stars are reported. The zero points of the new color indices conform closely to those of SAAO data reported in a previous paper. In addition, the new M67 measurements of (V − R) C and (R − I ) C are compared to data published previously by Taylor, Joner, and Jeffery. The results support conclusions drawn by those authors that the scale factors of their data are correct and that a scale factor problem exists in measurements published by Montgomery, Marshall, and Janes. The new values of B − V are used with Tycho data in tests of extant Hyades and M67 measurements and of the accuracy of the SAAO B − V system. A problem encountered previously with the Hyades B − V zero point is resolved, and an extant Hyades relation between B − V and (R − I ) C is re-zeroed. A satisfactory zero point is also obtained for M67, and published photomultiplier values of B − V are reduced to that zero point, averaged, and tabulated. It is found that the zero point of B − V data published by Sandquist is satisfactory. However, tests of B − V measurements made by Montgomery et al. suggest that those data are not on a single zero point. Finally, the scale factor of the E region B − V system is found to be satisfactory, but a well-supported interim conclusion is drawn that E region values of B − V should be corrected by about −9 mmag. It is suggested that this conclusion be tested by using instrumental systems that have not yet contributed to the testing process.

The Unevolved Main Sequence of Nearby Field Stars and the Open Cluster Distance Scale

“…Because our catalog includes Hyades stars and the Hyades is assumed to be reddening-free, the only potential source of controversy is the photometric scale. Our analysis confirms what has been found by others (Joner et al 2006;Joner et al 2008). The Johnson & Knuckles (1955) photometric system in the Hyades is offset from the SAAO/E-region standards that define the transformed Tycho-2 system by approximately -0.009 mag and 0.02 mag in B − V and V , respectively.…”

“…), again in good agreement with the results derived above. The B − V color offset between the Hyades and the Tycho-2 system has also been confirmed by the analysis of Joner et al (2008).…”

“…The former builds upon the approach of Pinsonneault et al (2003Pinsonneault et al ( , 2004 The last piece of the puzzle requires a link between the adopted BV photometry for M67 (Sandquist 2004) and that of the transformed Tycho-2 colors. The only direct comparison is that of Joner et al (2008) where the Hyades, M67, and transformed Tycho-2 data are coupled through SAAO observations, all ultimately tied to SAAO E-region standards. Within the uncertainties, the multiple comparisons imply that the color offsets required to transform the Johnson & Knuckles (1955) Hyades BV data to the Tycho-2/SAAO system are similar to those applicable to the Sandquist (2004) BV data of M67 tied to the Johnson system through the standards of Stetson (2000) and Landolt (1992).…”

Selecting High-Precision Photometry on Uniform Zero Points for Five Benchmark Galactic Clusters

“…Users who do not require Hyades values of V − R can limit their attention to Table 2 and CDS data files from TJJ. 1 Those who wish to include Hyades values of V − R should consult Taylor & Joner (1985), Joner et al (2006), andJoner et al (2008) and the footnotes given in Table 1 to the entries for those papers.…”

NEWBV(RI)CPHOTOMETRY FOR PRAESEPE: FURTHER TESTS OF BROADBAND PHOTOMETRIC CONSISTENCY

“…In the first paper, a new homogeneous set of Hyades photometry is tested (see Joner et al 2006, hereafter Paper I). The second paper presented tests of new Hyades and M67 measurements along with standard-star values of B − V in the SAAO system (see Joner et al 2008, hereafter Paper II). The current paper examines new Praesepe photometry and compares it with prior results.…”