{
  "id": "1705.06780",
  "version": "v1",
  "published": "2017-05-18T19:55:46.000Z",
  "updated": "2017-05-18T19:55:46.000Z",
  "title": "Where Are the r-modes? Chandra Observations of Millisecond Pulsars",
  "authors": [
    "Simin Mahmoodifar",
    "Tod Strohmayer"
  ],
  "comment": "9 pages, 4 figures, published in ApJ",
  "journal": "The Astrophysical Journal, Volume 840, Number 2, article id. 94, 8 pp. (2017)",
  "doi": "10.3847/1538-4357/aa6d62",
  "categories": [
    "astro-ph.HE",
    "astro-ph.SR"
  ],
  "abstract": "We present the results of {\\it Chandra} observations of two non-accreting millisecond pulsars, PSRs J1640$+$2224 (J1640) and J1709$+$2313 (J1709), with low inferred magnetic fields and spin-down rates in order to constrain their surface temperatures, obtain limits on the amplitude of unstable $r$-modes in them, and make comparisons with similar limits obtained for a sample of accreting low-mass X-ray binary (LMXB) neutron stars. We detect both pulsars in the X-ray band for the first time. They are faint, with inferred soft X-ray fluxes ($0.3-3$ keV) of $\\approx$ $6\\times10^{-15}$ and $3\\times 10^{-15}$ erg cm$^{-2}$ s$^{-1}$ for J1640 and J1709, respectively. Spectral analysis assuming hydrogen atmosphere emission gives global effective temperature upper limits ($90\\%$ confidence) of $3.3 - 4.3 \\times 10^5$ K for J1640 and $3.6 - 4.7 \\times 10^5$ K for J1709, where the low end of the range corresponds to canonical neutron stars ($M=1.4 M_{\\odot}$), and the upper end corresponds to higher-mass stars ($M=2.21 M_{\\odot}$). Under the assumption that $r$-mode heating provides the thermal support, we obtain dimensionless $r$-mode amplitude upper limits of $3.2 - 4.8 \\times 10^{-8}$ and $1.8 - 2.8 \\times 10^{-7}$ for J1640 and J1709, respectively, where again the low end of the range corresponds to lower-mass, canonical neutron stars ($M=1.4 M_{\\odot}$). These limits are about an order of magnitude lower than those we derived previously for a sample of LMXBs, except for the accreting millisecond X-ray pulsar (AMXP) SAX J1808.4$-$3658, which has a comparable amplitude limit to J1640 and J1709.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2017-05-18T19:55:46.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "millisecond pulsars",
      "chandra observations",
      "effective temperature upper limits",
      "canonical neutron stars",
      "analysis assuming hydrogen atmosphere emission"
    ],
    "tags": [
      "journal article"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 9,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}