A powerful magnetar awakened in the constellation Sagittarius
Magnitars are neutron stars with an extremely strong magnetic field, the induction of which reaches, according to astrophysicists, up to 1011 T. This is a little - about a quadrillion times - superior to the induction of the Earth's magnetic field. It is believed that such a powerful field is formed due to currents flowing in a neutron star in the initial period of its existence. Its energy is spent on radiation, mainly in the X-ray range, and lasts for a short time - for several tens of thousands of years. By cosmic standards, this is an instant.
The XTE J1810−197 magnetar located in the constellation Sagittarius was discovered in 2004 by a burst in the radio range. Scientists suggest that this star has recently become neutron and we were able to hear, if not the first cry, then the sniffing of a baby. The star’s rotation period is 5.54 seconds - for neutron stars this speed is perhaps even small. From a few - magnetars all over the Milky Way, a little more than two dozen are known - its analogues are distinguished by powerful radiation in the radio range. Usually the abilities of these luminaries are exhausted by x-ray radiation. Astronomers recorded radio pulses in 2008, when the star suddenly became silent.
In anticipation of the XTE J1810−197 radioactivity, a group of astronomers led by Lina Levin of the Center for Astrophysics at the University of Manchester, has observed this magnetar since 2009 with the help of the Lovell telescope at the Jodrell Bank Observatory (JBO). On December 8, 2018, scientists discovered a bright pulsed radio signal at a frequency of 1.52 GHz from this source, which marked the end of almost a decade of its radio silence.
According to the study, the pulse shape of the XTE J1810−197 has changed significantly since its discovery in 2004. However, the profile changes observed during the first two months after reactivation were less significant than what was last observed when this source was active.
In addition, astronomers identified 50-millisecond oscillations observed in the magnetar's pulse profile for about 10 days after it was re-detected. These oscillations have a characteristic frequency of 20 Hz and are observed at different carrier frequencies and at different telescopes simultaneously. The authors of the article suggest that such oscillations can be associated with surface waves initiated in the crust of neutron stars with a wide spectrum of frequencies.
The reasons why the star was silent for ten years are still unclear.