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Astron. Astrophys. 352, L103-L106 (1999)

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3. Radio spectrum

The source G16.2-2.7 was detected in the Galactic plane survey (Trushkin, 1996 , 1998) at 0.96 and 3.9 GHz, then we observed this sources in May 1999 with the RATAN-600 radio telescope. The transit observations were carried out with the North sector at 0.96, 2.3, and 3.9 GHz of the continuum radiometric complex of RATAN-600 in the upper culmination of the source. The angular resolution (HPBW) in Azimuth [FORMULA] Elevation is [FORMULA] and [FORMULA] at 0.96 and 3.9 GHz, respectively.

Also we used the images in the FITS format from the Effelsberg Galactic plane surveys at 1.4 and 2.7 GHz to estimate the flux densities from G16.2-2.7. In the package "Skyview" (Ebert et al. 1998) we calculated the integral flux densities in a defined elliptical area of the images. The linear background was subtracted using the pixels of nearby regions around G16.2-2.7.

In Table 2 we summarize the flux density measurements, where [FORMULA][FORMULA] means [FORMULA] error. In Fig. 5 radio spectrum of G16.2-2.7 is plotted. A power law non-thermal spectrum is a good fit: [FORMULA][Jy]=([FORMULA])[FORMULA]. Based on the spectra of nearly 200 Galactic SNRs, Trushkin (1999b) shows that the mean spectral index for the total sample of the 200 Galactic SNRs is equal to [FORMULA] at high frequencies.

[FIGURE] Fig. 5. Radio spectrum of the new SNR, the Effelsberg surveys data at 1.4 and 2.7 GHz are marked by boxes, the RATAN data at 0.96, 2.3 and 3.9 GHz are marked by diamonds.


[TABLE]

Table 2. Measured flux densities from G16.2-2.7


We have tried to roughly estimate the distance and diameter of the SNR from the [FORMULA] relation. In order to avoid uncertainties in calibrating the Galactic SNRs distances, we took the relation, based on the sample of SNRs of nearby galaxies (Huang et al. 1994): [FORMULA](W Hz-1m- 2 sr-1) = [FORMULA]. Then for the angular size [FORMULA] and above fitting of S[FORMULA], the distance d[FORMULA]13 kpc and the diameter D[FORMULA]64 pc. A new refined [FORMULA] relation was obtained by Case & Bhattachatya (1998) for a sample of 36 Galactic shell SNRs: [FORMULA](W Hz-1m- 2 sr-1) = [FORMULA]. For [FORMULA](1GHz)[FORMULA]W Hz-1m- 2 sr-1 it gives D[FORMULA] pc and d=[FORMULA] kpc Then the distance from the Galactic plane z = 300[FORMULA] pc.

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© European Southern Observatory (ESO) 1999

Online publication: December 2, 1999
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