{
  "id": "2307.00341",
  "version": "v1",
  "published": "2023-07-01T13:38:24.000Z",
  "updated": "2023-07-01T13:38:24.000Z",
  "title": "Effective temperatures of classical Cepheids from line-depth ratios in the H-band",
  "authors": [
    "V. Kovtyukh",
    "B. Lemasle",
    "N. Nardetto",
    "G. Bono",
    "R. da Silva",
    "N. Matsunaga",
    "A. Yushchenko",
    "K. Fukue",
    "E. K. Grebel"
  ],
  "comment": "17 pages, 10 figures, 4 tables. Published in MNRAS",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "The technique of line depth ratios (LDR) is one of the methods to determine the effective temperature of a star. They are crucial in the spectroscopic studies of variable stars like Cepheids since no simultaneous photometry is usually available. A good number of LDR-temperature relations are already available in the optical domain, here we want to expand the number of relations available in the near-infrared in order to fully exploit the capabilities of current and upcoming near-infrared spectrographs. We used 115 simultaneous spectroscopic observations in the optical and the near-infrared for six Cepheids and optical line depth ratios to find new pairs of lines sensitive to temperature and to calibrate LDR-temperature relations in the near-infrared spectral range. We have derived 87 temperature calibrations valid in the [4800-6500] K range of temperatures. The typical uncertainty for a given relation is 60-70 K, and combining many of them provides a final precision within 30-50 K. We found a discrepancy between temperatures derived from optical or near-infrared LDR for pulsations phases close to phi ~ 0.0 and we discuss the possible causes for these differences. Line depth ratios in the near-infrared will allow us to spectroscopically investigate highly reddened Cepheids in the Galactic centre or in the far side of the disk.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2023-07-01T13:38:24.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "effective temperature",
      "line-depth ratios",
      "classical cepheids",
      "pulsations phases close",
      "temperature calibrations valid"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 17,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}