{
  "id": "2110.07802",
  "version": "v1",
  "published": "2021-10-15T01:50:59.000Z",
  "updated": "2021-10-15T01:50:59.000Z",
  "title": "VLBI properties of compact interplanetary scintillators detected by the Murchison Widefield Array",
  "authors": [
    "Sumit Jaiswal",
    "Tao An",
    "Ailing Wang",
    "Steven Tingay"
  ],
  "comment": "28 pages, 7 figures, 4 tables, Accepted for publication in MNRAS",
  "doi": "10.1093/mnras/stab2993",
  "categories": [
    "astro-ph.GA",
    "astro-ph.HE"
  ],
  "abstract": "Interplanetary scintillation (IPS) provides an approach for identifying the presence of sub-arcsec structures in radio sources, and very long baseline interferometry (VLBI) technique can help verify whether the IPS sources have fine structures on milli-arcsec (mas) scales. We searched the available VLBI archive for the 244 IPS sources detected by the Murchison Widefield Array at 162~MHz and found 63 cross-matches. We analysed the VLBI data of the 63 sources and characterised the compactness index in terms of the ratio $R$ of the VLBI-measured flux density at 4.3~GHz to the flux density estimated using the Very Large Array Sky Survey (VLASS) at 3~GHz and NRAO VLA Sky Survey (NVSS) at 1.4~GHz ($S_{\\rm VLBI}/S_{\\rm SA}$). Eleven sources are identified as blazars according to their flat spectra and strong variability. They show high compactness indices with $R>0.4$, compact core-jet structure, and a broad distribution of normalised scintillation index (NSI). Other sources show diverse morphologies (compact core, core and one-sided jet, core and two-sided jets), but there is a correlation between $R$ and NSI with a correlation coefficient $r=0.47$. A similar $R$--NSI correlation is found in sources showing single steep power-law or convex spectra. After excluding blazars (which are already known to be compact sources) from the VLBI-detected IPS sources, a strong correlation is found between the compactness and scintillation index of the remaining samples, indicating that stronger scintillating sources are more compact. This pilot study shows that IPS offers a convenient method to identify compact radio sources without the need to invoke high-resolution imaging observations, which often require significant observational time.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2021-10-15T01:50:59.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "murchison widefield array",
      "compact interplanetary scintillators",
      "vlbi properties",
      "ips sources",
      "scintillation index"
    ],
    "tags": [
      "journal article"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 28,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}