MeerKAT

Abstract:

One of the potential sources of repeating fast radio bursts (FRBs) is a rotating magnetosphere of a compact object, as suggested by the similarities in the polarization properties of FRBs and radio pulsars. Attempts to measure an underlying period in the times of arrival of repeating FRBs have nevertheless been unsuccessful. To explain this lack of observed periodicity, it is often suggested that the line of sight towards the source must be sampling active parts of the emitting magnetosphere throughout the rotation of the compact object, i.e. has a large duty cycle, as can be the case in a neutron star with near-aligned magnetic and rotation axes. This may lead to apparently aperiodic bursts; however, the polarization angle of the bursts should be tied to the rotational phase from which they occur. This is true for radio pulsars. We therefore propose a new test to identify a possible stable rotation period under the assumptions above, based on a periodogram of the measured polarization angle time series for repeating FRBs. We show that this test is highly sensitive when the duty cycle is large, where standard time-of-arrival periodicity searches fail. Therefore, we can directly test the hypothesis of repeating FRBs of magnetospheric origin with a stable rotation period. Both positive and negative results of the test applied to FRB data will provide important information.

Abstract:

We present the first results of the H i intensity mapping power spectrum analysis with the MeerKAT International GigaHertz Tiered Extragalactic Exploration (MIGHTEE) survey. We use data covering 4 square degrees in the COSMOS field using a frequency range of 962.5–1008.42 MHz, equivalent to H i emission in . The data consist of 15 pointings with a total of 94.2 h on-source. We verify the suitability of the MIGHTEE data for H i intensity mapping by testing for residual systematics across frequency, baselines, and pointings. We also vary the window used for H i signal measurements and find no significant improvement using stringent Fourier mode cuts. We compute the H i power spectrum at scales in autocorrelation as well as cross-correlation between observational scans using power spectrum domain averaging for pointings. We report consistent upper limits of 29.8 mK Mpc from the 2 cross-correlation measurements and 25.82 mK Mpc from autocorrelation at 2 Mpc.The low signal-to-noise ratio in this data potentially limits our ability to identify residual systematics, which will be addressed in the future by incorporating more data in the analysis.