1998A&A...331..661K

A new supernova remnant (G182.4+4.3) in the Galactic anti-centre region has been detected at radio frequencies. Observations at 1400MHz, 2675MHz, 4850MHz, and at 10450MHz with the Effelsberg 100-m telescope reveal a shell structure of about 50' across. The flux density radio spectral index is α=-0.42±0.10, (S_ν∝ν^α). The polarization percentage of the brighter part of the shell is about 40%. At 4850MHz the polarization percentage near the peak of the shell exceeds 60%. The Faraday rotation measure varies between 0rad/m² and 70rad/m². The total flux density extrapolated to 1GHz is 1.24±0.38Jy leading to a radio surface brightness of {SIGMA}_1GHz=7.5x10^–23Watt/m²/Hz/sr. HI line observations of neutral hydrogen show that the column density towards G182.4+4.3 must be ≤4x10²¹cm^–2. No X-ray emission is visible in the ROSAT all-sky survey at the position of the new supernova remnant. This corresponds to an upper limit of 6.2x10^–2counts/s. Some information on the nature of G182.4+4.3 is obtained from a discussion of these observations: G182.4+4.3 is at a distance of ≥3kpc and probably expanding according to the classical Sedov equations. Assuming an initial explosion energy of 10⁵¹erg the following parameters are obtained: n₀≃0.013cm^–3, a radius of R≃22.5pc, a swept-up mass of M_sw≃14M_☉, kT≃5.0keV, age=3800years, and V_exp=2300km/s.