J/AZh/71/110     Supernova Remnants at Meter Wavelengths (Kovalenko+ 1994)
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Observations of Supernova Remnants at Pushchino:
Catalog of Flux Densities at Meter Wavelengths.
     Kovalenko A.V., Pynzar A.V., Udaltsov V.A.
    
    =1994AZh....71..110K
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ADC_Keywords: Supernova remnants; Radio sources; Surveys


Description:
    The total flux densities of more than one hundred galactic supernova
    remnants (SNR) at 111, 102, and 83MHz, measured at Pushchino using the
    E-W WBCR-1000 and LSA radio telescopes, to an accuracy of 2Jy or
    better; the spectral indices, with their errors, obtained from the
    compiled spectra; and optical depths at 100MHz in the direction of the
    supernova remnants are reported. The latter values are obtained from a
    low frequency cutoff caused by interstellar gas absorption, which was
    detected at meter and decimeter wavelengths in the direction of 38% of
    the supernova remnants.

File Summary:

       FileName      Lrecl  Records   Explanations

? ReadMe            80        .   This file
? table2           141      119   Catalog of SNR Flux Densities at Meter Wavelengths


Byte-by-byte Description of file:  table2

   Bytes Format  Units     Label    Explanations

   1-  6  F6.2   deg       GLON     Galactic longitude
   8- 12  F5.1   deg       GLAT     Galactic latitude
  15- 22  A8     ---      OtherNam  Other Names of SNR
  24- 25  I2     h         RAh      Right ascension (2000)
  27- 28  I2     min       RAm      Right ascension (2000)
  30- 31  I2     s         RAs      Right ascension (2000)
      33  A1     ---       DE-      Declination sign
  34- 35  I2     deg       DEd      Declination (2000)
  37- 38  I2     arcmin    DEm      Declination (2000)
  42- 48  A7     arcmin    AS       ? Angular size
      49  A1     ---       u_AS     [?] Uncertainty in size
      51  A1     ---       l_S83    Limit flag on S83 (> meaning >=)
  52- 57  F6.1   Jy        S83      ? Flux density at 83 MHz
  59- 61  I3     Jy        e_S83    ? Mean error on S83
      63  A1     ---       l_S102   Limit flag on S102 (> meaning >=)
  64- 69  F6.1   Jy        S102     ? Flux density at 102 MHz
  71- 73  I3     Jy        e_S102   ? Mean error on S102
      75  A1     ---       l_S111   Limit flag on S111 (> meaning >=)
  77- 83  F7.1   Jy        S111     ? Flux density at 111 MHz
  85- 90  F6.1   Jy        e_S111   ? Mean error on S111
      92  A1     ---       l_alpha  Limit flag on alpha (> meaning >=)
  93- 96  F4.2   ---       alpha    ? Spectral index
  99-102  F4.2   ---       e_alpha  ? Mean error on alpha
     103  A1     ---       u_alpha  [?] Uncertainty on alpha
 105-111  F7.2   Jy        S1       ? Flux density at 1 GHz
     112  A1     ---       u_S1     [?] Uncertainty on S1
     114  A1     ---       l_Tau    Limit flag on Tau (> meaning >=)
 115-120  F6.4   ---       Tau      ? Optical depth at 100 MHz
 122-127  F6.4   ---       e_Tau    ? Mean error on optical depth
     128  A1     ---       u_Tau    [?] Uncertainty on Tau
 130-137  A8     MHz       band     Frequency band for optical depth
 139-141  A3     ---       N        Running number of SNRs for remarks (1)

Note (1):
  1. The highest absorption is observed in the direction of G0.0+0.0.
      According to [47], (a(5-1.4GHz)=0.7, and Sa(327MHz)=220Jy;
      from [48] Sobs(327MHz)=135Jy, that t(327MHz)=0.51, or, after reduction,
      t(100MHz)=6.14.
  2. G0.9+0.1 is a classic example of a composite, two-component SNR including
      an extended (8') source with a steep (a=-0.64) spectrum and a central,
      more compact, component (2') with a flat spectrum (a=-0.1) [49]. The
      central component's contribution does not exceed 10% at 100MHz
      and S(1GHz) are shown for the extended component.
 16. The higher absorption in the direction of G9.8+0.6 obtained in [7] is
      caused by the overestimated (a=-0.8) adopted by the author.
 21. G12.0-0.1 is a two-component source with thermal and nonthermal
      components; according to Green [1] a=-1(?).
 26. In the direction G16.8-1.1 thermal and nonthermal components were
      registered. The spectrum with the positive spectral index was observed at
      centimeter wavelengths [50]; the likely reason is thermal self-absorption.
      The table shows the spectral index of the nonthermal component.
 58. Radio source G43.3-0.2 (W49B), has a possible spectrum break. The
      spectral index is a=0 at frequencies lower than 350MHz, and a=-0.47 at
      higher frequencies.
 74. Radio source G69.0+2.7 (CTB 80) has an unusual spectrum. Possibly it
      has a break near 1GHz. In the frequency range f<=1GHz, a~=+0.3,
      and at f>=1GHz, a=-0.83.
 The compiled spectra of 9 SNRs: 4, 42, 52, 64, 73, 75, 99, 103, and 111, were
   not constructed. The spectral indices, without error, are taken from [1].
   The absolute spectral index measurement accuracy of a>=0.15 was obtained for
   26 SNRs: 2, 3, 10, 12, 15, 16, 17, 19, 44, 49, 59, 65, 66, 69, 72, 77, 80,
   84, 88, 95, 98, 100, 101, 104, 107, and 110. Such great errors for 24% of the
   SNRs are the result of a large scatter of the compiled spectrum points, the
   low accuracy of the flux density measurements at different frequencies, and
   the small number of points. Several spectra, 98 and 110 for instance, were
   constructed using only two points: 83 and 408MHz. The smaller absolute
   measurement error, a>=0.1, had already been obtained for 70% of the SNRs.
   Absorption of SNR radio emission has yet to be observed for 42 SNRs (38%),
   see Table 2, column (11). The highest absorption was observed for four
   sources in the direction of the galactic central region: 1, 2, 3, and the
   unidentified source G0.4+0.1 [t(100MHz)=6-0.8]. In the direction of
   the other SNRs, the optical depth is t(100MHz)<=0.8. A high frequency (over
   1 GHz) break in the spectrum was observed for seven SNRs: 30, 40, 77, 78, 84,
   100, and 104. In all these cases, the spectrum was considerably steeper at
   frequencies above the break frequency than at the lower ones. The spectral
   index at high frequencies for these SNRs is given in the second row in the
   table. Spectra are drawn and discussed in [27]. New SNRs included in the
   catalog are: 3, 19, 68, and 99. SNRs with a flat spectrum (-a<=0.25) are: 7,
   8, 10, 14, 31, 32, 38, 40, 58, 64, 73, and 111 - a total of 12 objects (11%).
   SNRs with a steep spectrum (-a>=0.7) are: 21, 22, 23, 27, 40, 74, 75, 77, 78,
   79, 87, 100, and 104 a total of 13 objects (12%). SNRs with a high relative
   spectral index measurement accuracy (da/a<=0.1) are: 5, 18, 21, 23, 41, 45,
   and 53 a total of 7 objects (6%).


References:
   1. Green, 1991PASP...13..209G
   7. Kassim, 1989AJ...347..915K
  11. Udal'tsov et al., 1978XI All-Union Radio Astronomy Conf.,Erevan...132U
  27. Kovalenko et al., 1994AZh...71..92K
  47. Ekkers et al., 1983A&A...122..143E
  49. Helfand et al., 1989ApJ...341..151H
  50. Furst et al., 1990A&AS...155..185F
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(End)                                   Veta Avedisova [INASAN]      30-Sep-1996

Observations of SNR at Pushchino: Catalog of Flux Densities at Meter Wavelengths;

Kovalenko, Pynzar & Udal'tsov;