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J/AZh/71/110     Supernova Remnants at Meter Wavelengths (Kovalenko+ 1994)

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
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 (J2000) 27- 28 I2 min RAm Right ascension (J2000) 30- 31 I2 s RAs Right ascension (J2000) 33 A1 --- DE- Declination sign 34- 35 I2 deg DEd Declination (J2000) 37- 38 I2 arcmin DEm Declination (J2000) 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
(End) Veta Avedisova [INASAN] 30-Sep-1996
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