Bulent Uyaniker

The Cygnus superbubble revisited

The Orion local spiral arm is seen tangential towards the Cygnus region. Intense radio emission with quite a complex morphology is observed, which appears to be surrounded by strong soft X{ray emission. This remarkable X{ray structure is known as the Cygnus superbubble. We compare a recent 1.4 GHz radio continuum and polarization map from the Eelsberg 100-m telescope with X{ray data from the ROSAT all{sky survey of this area. Including available survey data of the infrared, H i and CO emission, we investigate a number of high latitude features, which are physically related to one of the Cygnus OB associations. These OB associations, however, are located along the local arm at dierent distances. Our results support the view that the Cygnus superbubble is not a physical unity, but results from a projection of unrelated X{ray emitting features at dierent distances blown out from the local arm seen along the line of sight.

Distance of Three Supernova Remnants from H I 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 H I images toward 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 H I environment and a possible relationship of these SNRs with each other. We discovered patches of H I 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-1 (G116.5+1.1) and -27 km s-1 (CTB 1) according to related H I. However, the structure of the H I 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 H I feature that is moving as a whole toward us with a velocity of about 10 km s-1. Furthermore, the off-centered location of CTB 1 in a large H I bubble indicates that the so-called breakout region of the remnant is in fact due to its expansion toward 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.

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 α = −0.42 ± 0.06 (S ∼ ν α ), 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 ∆α = 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 α = −0. 4a ndα = −0.6 towards northern and southern parts of the object, respectively.

Two new Perseus arm supernova remnants discovered in the Canadian Galactic Plane Survey

We report the discovery of two new second-quadrant supernova remnants, G96.0+2.0 and G113.0+0.2, in the data of the Canadian Galactic Plane Survey. The two SNRs are residents of the Perseus spiral arm at distances of 4.0 kpc and 3.1 kpc, respectively. The distances were determined kinematically by associating the objects with neutral hydrogen and molecular material. G96.0+2.0 is most likely located at the edge of a large stellar wind bubble with a systemic velocity of about −44 km s −1 . It consists of a relatively bright shell where the shock is encountering the wall of H i and slowly fades away towards the interior of the stellar wind bubble. The visible part of the remnant has a diameter of about 30 pc and a radio spectral index of α ≈− 0.66 (S ∼ ν α ), indicating that it is a shell-type remnant in an early stage of development. The SNR is most likely the remnant of a type Ib/c supernova explosion. G113.0+0.2 is located in an area of confusing thermal emission not far from the radio-bright supernova remnant Cassiopeia A. It has an unusual elongated structure consisting of a long polarized filament and a more complex head structure that is interacting with a small molecular cloud; it resides in a butterfly-shaped H i cavity, probably a stellar wind bubble. It is about 36 pc long and 15 pc wide at a position angle of 70 ◦ with the Galactic Plane. A pulsar with a relatively low period derivative, giving it a characteristic age of 10 million years, is located close to the centre of the radio continuum emission at a Perseus arm distance. Whether the pulsar is the result of the same supernova explosion that created G113.0+0.2 or if it was left behind by an earlier supernova that also shaped the stellar wind bubble remains uncertain.

The MPIfR Radio Continuum Surveys and Their WWW Distribution

The observation of an area of 120° × 56° centered on RA=8 h DEC=20° at 408 MHz was the first astronomical use of the MPIfR 100-m telescope (1970) and was designed to compile a complete sky survey using also data from Jodrell Bank and Parkes (Haslam et al., 1982). The observation of the northern sky at 1420 MHz started in 1972 using the Stockert 25-m telescope and was finished in 1976 (Reich and Reich 1986). This survey has been completed to an all sky survey using data from Villa Elisa (Argentina). The two surveys are absolutely calibrated. The angular resolutions are 0.8° and 0.59°, respectively. A number of surveys of the Galactic plane have been made with the 100-m telescope at arc minute angular resolution. Surveys at 2695 MHz (|b| ≤ 5°) (Reich et al. 1990, Furst et al. 1990) and at 1410 MHz (|b| ≤ 4°) (Reich et al. 1990) are public.