{
  "id": "1508.05898",
  "version": "v1",
  "published": "2015-08-24T18:07:30.000Z",
  "updated": "2015-08-24T18:07:30.000Z",
  "title": "A new measurement of $Ω_m$ from Gamma-ray Bursts",
  "authors": [
    "Luca Izzo",
    "Marco Muccino",
    "Elena Zaninoni",
    "Lorenzo Amati",
    "Massimo Della Valle"
  ],
  "comment": "10 pages, 9 figures, 3 tables. Accepted for publication in A&A. Truncated abstract text",
  "categories": [
    "astro-ph.CO",
    "astro-ph.HE"
  ],
  "abstract": "Context: Data from cosmic microwave background radiation (CMB), baryon acoustic oscillations (BAO) and supernovae Ia (SNe-Ia) support a constant dark energy equation of state with $w_0 \\sim -1$. Measuring the evolution of $w$ along the redshift is one of the most demanding challenges for observational cosmology. Aims: We present and discuss the existence of a tight relation for GRBs, named \"Combo-relation,\" based on characteristic parameters of GRB phenomenology such as the prompt intrinsic peak energy $E_{p,i}$, the X-ray afterglow, the initial luminosity of the shallow phase $L_0$, the rest-frame duration $\\tau$ of the shallow phase, and the index of the late power-law decay $\\alpha_X$. We use it to measure $\\Omega_m$ and the evolution of the dark energy equation of state. We also propose a new calibration method for the same relation, which reduces the dependence on SNe Ia systematics. Methods: We have selected a sample of GRBs having: 1) a measured redshift $z$; 2) a determined intrinsic prompt peak energy $E_{p,i}$, and 3) a good coverage of the observed (0.3-10) keV afterglow light curves. The fitting technique of the rest-frame (0.3-10) keV luminosity light curves represents the core of the Combo-relation. We separate the early steep decay, considered as part of the prompt emission, from the X-ray afterglow additional component. Data with the largest positive residual, identified as flares, are automatically eliminated until the p-value of the fit becomes greater than 0.3. Results: We strongly minimize the dependency of the Combo-GRB calibration on SNe Ia. We also measure a small extra-poissonian scatter of the Combo-relation, which allows us to infer from GRBs alone $\\Omega_M =0.29^{+0.23}_{-0.15}$ (1$\\sigma$) for the $\\Lambda$CDM cosmological model, and $\\Omega_M =0.40^{+0.22}_{-0.16}$, $w_0 = -1.43^{+0.78}_{-0.66}$ for the flat-Universe variable EOS case.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2015-08-24T18:07:30.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "gamma-ray bursts",
      "intrinsic prompt peak energy",
      "dark energy equation",
      "kev luminosity light curves represents",
      "prompt intrinsic peak energy"
    ],
    "publication": {
      "doi": "10.1051/0004-6361/201526461"
    },
    "note": {
      "typesetting": "TeX",
      "pages": 10,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1389149
    }
  }
}