We present an analysis of the diffuse emission at 5 GHz in the first quadrant of the Galactic plane using two months of preliminary intensity data taken with the C-Band All Sky Survey (C-BASS) northern instrument at the Owens Valley Radio Observatory, California.Combining C-BASS maps with ancillary data to make temperature-temperature plots we find synchrotron spectral indices of β = −2.65 ± 0.05 between 0.408 GHz and 5 GHz and β = −2.72 ± 0.09 between 1.420 GHz and 5 GHz for −10 • < |b| < −4 • , 20 • < l < 40 • . Through the subtraction of a radio recombination line (RRL) free-free template we determine the synchrotron spectral index in the Galactic plane (|b| < 4 • ) to be β = −2.56 ± 0.07 between 0.408 GHz and 5 GHz, with a contribution of 53 ± 8 per cent from free-free emission at 5 GHz. These results are consistent with previous low frequency measurements in the Galactic plane.By including C-BASS data in spectral fits we demonstrate the presence of anomalous microwave emission (AME) associated with the Hii complexes W43, W44 and W47 near 30 GHz, at 4.4 σ, 3.1 σ and 2.5 σ respectively. The CORNISH VLA 5 GHz source catalogue rules out the possibility that the excess emission detected around 30 GHz may be due to ultra-compact Hii regions. Diffuse AME was also identified at a 4σ level within 30 • < l < 40 • , −2 • < b < 2 • between 5 GHz and 22.8 GHz.

We report the serendipitous discovery of the Sloan Digital Sky Survey star, SDSS J160043.6+074802.9 to be a very rapid pulsator. The variation is dominated by a frequency near 8380 microHz (period = 119.33 s) with a large amplitude (0.04 mag) and its first harmonic at 16760 microHz (59.66 s; 0.005 mag). In between these frequencies, we find at least another 8 variations with periods between 62 and 118 seconds and amplitudes between about 0.007 and 0.003 mag; weaker oscillations might also be present. Preliminary spectrograms from the performance verification phase of the Southern African Large Telescope indicate that SDSS J160043.6+074802.9 is a spectroscopic binary consisting of an sdO star and a late-type main-sequence companion. This makes it the first unambiguous detection of such an sdO star to pulsate, and certainly the first found to exhibit multi-frequency variations.Comment: 7 pages, 6 figures (figure 4 at reduced resolution, original available on request). Accepted for publication in MNRA

The C-Band All-Sky Survey (C-BASS) is an all-sky full-polarization survey at a frequency of 5 GHz, designed to provide complementary data to the all-sky surveys of WMAP and Planck, and future CMB B-mode polarization imaging surveys. The observing frequency has been chosen to provide a signal that is dominated by Galactic synchrotron emission, but suffers little from Faraday rotation, so that the measured polarization directions provide a good template for higher frequency observations, and carry direct information about the Galactic magnetic field. Telescopes in both northern and southern hemispheres with matched optical performance are used to provide all-sky coverage from a ground-based experiment. A continuous-comparison radiometer and a correlation polarimeter on each telescope provide stable imaging properties such that all angular scales from the instrument resolution of 45 arcmin up to full sky are accurately measured. The northern instrument has completed its survey and the southern instrument has started observing. We expect that C-BASS data will significantly improve the component separation analysis of Planck and other CMB data, and will provide important constraints on the properties of anomalous Galactic dust and the Galactic magnetic field.