Two new rotating radio transients discovered by astronomers

Two new rotating radio transients discovered by astronomers

The time in milliseconds is delayed along the horizontal axis. The vertical axis shows the frequency of observations in MHz. The dark line within the dynamic spectrum is the signal of the detected transient. The intensity of radiation within the dynamic spectrum is shown in shades of gray. The darker the color, the stronger the recorded signal. Pulse profiles are shown above the spectra, which represent the integral sum of the pulse in all frequency channels, combined taking into account the dependence of the signal delay in the interstellar medium on the frequency of observations. The slope of the line reflects the magnitude of the dispersion measure (DM). The greater the slope, the greater the DM. Credit: Tyul’bashev et al., 2022.

Using the Pushchino Radio Astronomy Observatory (PRAO), Russian astronomers have conducted a search for rotating radio transients (RRATs). In a recently published article on the arXiv pre-print server, they report the detection of two new RRATs as part of this observation campaign.

RRATs are a subclass of pulsars characterized by sporadic emission. The first objects of this type were identified in 2006 as sporadically appearing scattered pulses, with frequencies ranging from a few minutes to several hours. However, the nature of these transients is still unclear. It is generally believed that they are common pulsars experiencing strong pulses.

So far, only a little over 100 RRATs have been found, which is why astronomers are interested in detecting new such transients in order to characterize them and improve our knowledge about their nature.

Now a team of astronomers led by Sergey Tyul’bashev of PRAO are reporting the discovery of two new RRATs: J1550+09 and J2047+13. The finding was made with PRAO’s Large Phased Array with a channel width of 78 kHz and a readout time of 12.5 milliseconds. The observations were performed simultaneously in 96 spatial beams with declinations from -7 to +42 degrees.

“The large effective area of ​​the radio telescope, which is about 45,000 m2offers high fluctuation sensitivity, making it possible to Search for RRATs,” the researchers explained.

Both RRATs were found far beyond the plane of the Milky Way Galaxy. The distances were estimated to be about 3,100 and 7,200 light years, for J1550+09 and J2047+13 respectively, so typical for pulsars. The dispersion size for J1549+09 and J2047+12 was calculated to be 21 and 35 pct/cm3

According to the study, J1549+09 was detected four times in a four-year interval and J2047+12 was detected seven times. For J2047+12, two pulses were detected on one of the days, over a span of 2.925 seconds. The pulse half widths for J1550+09 and J2047+13 were measured as 18 and 35 milliseconds, respectively.

The astronomers noted that the observation time before the appearance of the pulse of J1550+09 was 20 hours, and for J2047+12 about 11 hours. The researchers concluded that this confirms the existence of RRATs, which have one pulse for 10 or more hours.

“The study demonstrates the existence of rotating transients whose pulses occur less frequently than one pulse per 10 hours of observation.(…) Long series of observations and the use of the programs described above allow to obtain such a seldom flashing rotary radio detect transient,” the article’s authors wrote.

Gamma-ray pulsations detected by pulsar PSR J1835-3259B

More information:
Detection of two new RRATs at 111 MHz, arXiv:2206.12108 [astro-ph.HE]

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