{
  "id": "1009.5704",
  "version": "v1",
  "published": "2010-09-28T21:40:51.000Z",
  "updated": "2010-09-28T21:40:51.000Z",
  "title": "An Examination of Recent Transformations to the BV(RI)_C Photometric System from the Perspective of Stellar Models for Old Stars",
  "authors": [
    "Don A. VandenBerg",
    "Luca Casagrande",
    "Peter B. Stetson"
  ],
  "comment": "To appear in 2010, AJ, 140, 1020",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "Isochrones for ages > 4 Gyr and metallicities in the range -2.5 < [Fe/H] < +0.3 that take the diffusion of helium and recent advances in stellar physics into account are compared with observations in the Johnson-Cousins BV(RI)_C photometric system for several open and globular star clusters. The adopted color-Teff relations include those which we have derived from the latest MARCS model atmospheres and empirical transformations for dwarf and subgiant stars given by Casagrande et al (2010, A&A, 512, 54; CRMBA). Those reported by VandenBerg & Clem (2003, AJ, 126, 778) have also been considered, mainly to resolve some outstanding questions concerning them. Remarkably, when the subdwarfs in the CRMBA data set that have sigma_pi/pi < 0.15 are superimposed on a set of 12 Gyr isochrones spanning a wide range in [Fe/H], the inferred metallicities and effective temperatures agree, in the mean, with those given by CRMBA to within +/- 0.05 dex and +/- 10 K, respectively. Thus the hot Teff scale derived by CRMBA is nearly identical with that predicted by stellar models and consequently, there is excellent consistency between theory and observations on the H-R diagram and the different color-magnitude diagrams considered in this investigation. To obtain similar consistency, the colors obtained from the MARCS and VandenBerg & Clem B-V vs. Teff relations for metal-poor dwarf stars should be adjusted to the red by 0.02-0.03 mag. In general, isochrones that employ the CRMBA transformations provide reasonably good fits to our BV(RI)_C photometry for main-sequence stars in the globular clusters 47 Tuc, M3, M5, M92 and NGC 1851 - but not the cluster giants (when adopting the synthetic MARCS colors). We speculate that differences between the actual heavy-element mixtures and those assumed in the theoretical models may be the primary cause of this difficulty.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2010-09-28T21:40:51.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "stellar models",
      "photometric system",
      "old stars",
      "transformations",
      "latest marcs model atmospheres"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1088/0004-6256/140/4/1020",
      "journal": "The Astronomical Journal",
      "year": 2010,
      "month": "Oct",
      "volume": 140,
      "number": 4,
      "pages": 1020
    },
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 871440,
      "adsabs": "2010AJ....140.1020V"
    }
  }
}