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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.
<Astron. Zh. 71, 110 (1994)>
=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:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2 141 119 Catalog of SNR Flux Densities at Meter Wavelengths
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Byte-by-byte Description of file: table2
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Bytes Format Units Label Explanations
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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)
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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%).
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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