High Frequency Radio Observations of Two Magnetars, PSR J1622$-$4950 and 1E 1547.0$-$5408

TL;DR

This study analyzes radio spectra of two magnetars, revealing spectral features, flux variations, and potential emission mechanisms, which enhance understanding of their radio and X-ray emission connection.

Contribution

It provides detailed radio spectral measurements of two magnetars and compares their radio and X-ray emission evolution, proposing insights into their emission mechanisms.

Findings

PSR J1622-4950 has a steep spectrum with spectral index -1.3 in 5.5-45 GHz.

1E 1547.0-5408 shows an inverted spectrum with a peak at a few hundred GHz.

Radio emission rises more slowly than X-ray during outbursts, indicating different emission processes.

Abstract

We investigated the radio spectra of two magnetars, PSR J1622$-$4950 and 1E 1547.0$-$5408, using observations from the Australia Telescope Compact Array and the Atacama Large Millimeter/submillimeter Array taken in 2017. Our observations of PSR J1622$-$4950 show a steep spectrum with a spectral index of $-$1.3 $\pm$ 0.2 in the range of 5.5-45 GHz during its re-activating X-ray outburst in 2017. By comparing the data taken at different epochs, we found significant enhancement in the radio flux density. The spectrum of 1E 1547.0$-$5408 was inverted in the range of 43-95 GHz, suggesting a spectral peak at a few hundred gigahertz. Moreover, we obtained the X-ray and radio data of radio magnetars, PSR J1622$-$4950 and SGR J1745$-$2900, from literature and found two interesting properties. First, radio emission is known to be associated with X-ray outburst but has different evolution. We further found that the rising time of the radio emission is much longer than that of the X-ray during the outburst. Second, the radio magnetars may have double peak spectra at a few GHz and a few hundred GHz. This could indicate that the emission mechanism is different in the cm and the sub-mm bands. These two phenomenons could provide a hint to understand the origin of radio emission and its connection with the X-ray properties.