Analysis of data from the Rossi X-ray Timing Explorer satellite's All Sky Monitor (ASM) instrument for several X-ray binary sources has identified a recurrent ∼24 h period. This period is sometimes highly significant, giving rise to the possibility of it being identified as an orbital or super-orbital period. Further analysis has revealed the same period in a number of other X-ray sources. As a result this period has been discounted as spurious, described variously as arising from daily variations in background levels, the scheduling of ASM observations and beating between the sampling period and long-term secular trends in the light curves. We present here an analysis of the spurious periods and show that the dominant mechanism is in fact spectral leakage of low-frequency power present in the light curves.

The 6dF Galaxy Survey is measuring around 150 000 redshifts and 15 000 peculiar velocities from galaxies over the southern sky at |b| > 10°. When complete, it will be the largest survey of its kind by more than an order of magnitude. Here we describe the characteristics of the Second Incremental Data Release and provide an update of the survey. This follows earlier data made public in 2002 December and 2004 March. A total of 83 014 sources now have their spectra, redshifts, and near-infrared and optical photometry available online and searchable through an Structured Query Language database at www-wfau.roe.ac.uk/6dFGS/.

Based on the magnitude–redshift diagram for the sample of supernovae Ia analyzed by Perlmutter et al. (1999), Davis & Lineweaver (2004) ruled out the special relativistic interpretation of cosmological redshifts at a confidence level of 23σ. Here, we critically reassess this result. Special relativity is known to describe the dynamics of an empty universe, by means of the Milne kinematic model. Applying only special relativistic concepts, we derive the angular diameter distance and the luminosity distance in the Milne model. In particular, in this model we do not use the underlying metric in its Robertson–Walker form, so our exposition is useful for readers without any knowledge of general relativity. We do however, explicitly use the special relativistic Doppler formula for redshift. We apply the derived luminosity distance to the magnitude–redshift diagram for supernovae Ia of Perlmutter et al. (1999) and show that special relativity fits the data much better than that claimed by Davis & Lineweaver. Specifically, using these data alone, the Milne model is ruled out only at a 2σ level. Alhough not a viable cosmological model, in the context of current research on supernovae Ia it remains a useful reference model when comparing predictions of various cosmological models.