The distance to the SNR CTB109 deduced from its environment

We conducted a study of the environment around the supernova remnant CTB109. We found that the SNR is part of a large complex of HII regions extending over an area of 400 pc along the Galactic plane at a distance of about 3 kpc at the closer edge of the Perseus spiral arm. At this distance CTB109 has a diameter of about 24 pc. We demonstrated that including spiral shocks in the distance estimation is an ultimate requirement to determine reliable distances to objects located in the Perseus arm. The most likely explanation for the high concentration of HII regions and SNRs is that the star formation in this part of the Perseus arm is triggered by the spiral shock.Comment: 6 pages, 6 figures. accepted for publication in the Astrophysical Journa

Radio emission from the Cygnus Loop and its spectral characteristics

We present a new sensitive 2675 MHz radio continuum map of the Cygnus Loop, which is used in conjunction with 408 MHz, 863 MHz and 1420 MHz maps from both the Effelsberg 100-m telescope and the DRAO Synthesis Telescope for a spectral analysis. Between 408 MHz and 2675 MHz we find an overall integrated spectral index of $\rm \alpha = -0.42 \pm 0.06$ ($S \sim \nu^{\alpha}$), close to previous results. There is no indication of a spectral break in the integrated spectrum. Spatially highly varying and rather strong spectral curvature was previously reported, but is not confirmed on the basis of new, higher sensitivity observations. We found spectral variations across the Cygnus Loop reaching up to $\Delta\alpha = 0.2$ from a TT-plot analysis. The flattest spectra are seen towards enhanced emission areas. Spectral index maps produced between different frequency pairs, as well as all four maps, revealed that there are at least three flat spectrum regions. In regions interior to the high emission filaments, we have detected at least two spectral components across the whole object with $\alpha=-0.4$ and $\alpha=-0.6$ towards northern and southern parts of the object, respectively.Comment: 22 pages, 13 figures in jpeg format, accepted for publication in Astrophysics & Astronom

Distance of three Supernova Remnants from HI line observations in a complex region: G114.3+0.3, G116.5+1.1, and CTB 1 (G116.9+0.2)

We present new radio continuum and HI images towards the supernova remnants (SNRs) G114.3+0.3, G116.5+1.1, and G116.9+0.2 (CTB 1) taken from the Canadian Galactic Plane Survey (CGPS). We discuss the dynamics of their HI environment and a possible relationship of these SNRs with each other. We discovered patches of HI emission surrounding G114.3+0.3 indicating a location in the Local arm at a distance of about 700 pc in contrast to previous publications which proposed a Perseus arm location. The other two SNRs have radial velocities of -17 km/s (G116.5+1.1) and -27 km/s (CTB 1) according to related HI. However, the structure of the HI and its dynamics in velocity space suggest a possible relation between them, placing both remnants at a distance of about 1.6 kpc. CTB 1 appears to be embedded in an HI feature which is moving as a whole towards us with a velocity of about 10 km/s. Furthermore, the off-centered location of CTB 1 in a large HI bubble indicates that the so-called breakout region of the remnant is in fact due to its expansion towards the low density interior of this bubble. We believe that the progenitor star of CTB 1 was an early B or O-type star shaping its environment with a strong stellar wind in which case it exploded in a Ib or Ic event.Comment: 16 pages, 9 figures, accepted for publication in The Astrophysical Journa

OBSERVATIONS OF A DELTA SCUTI-LIKE PULSATOR - HR-7222

Visual and blue band photometric observations of the delta Scuti-type variable have been carried out. It has been found that LT Vul pulsates in the radial fundamental mode. Higher overtones such as third and n > 3 overtones have also been detected

The low-resolution DRAO survey of H I emission from the galactic plane. II

NRC publication: Ye