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HEAPOW: A Loud Cry from a Baby Magnetar (2021 Jun 14)

The strongest magnets in the universe are magnetars, the crushed remnants of massive stars that are left behind after the nuclear fuel which sustains them is all used up, causing the center of the star to collapse to extremely high densities (about the same as the density of the atomic nuclei in your body) while (nearly simultaneously) the rest of the star explodes outwards as a supernova. Although massive stars usually have very weak magnetic fields, during the compactification of the core the magnetic field becomes intensified, reaching about one trillion times stronger than the magnetic field at the surface of the earth. Magnetars are extreme types of neutron stars, but have magnetic fields which are about 1000 times the strength of the magnetic field of a typical neutron star, and are typically only detected from their X-ray and gamma-ray emission (while typical neutron stars are usually strong radio emitters). Just a few dozen magnetars are known. The image above shows an artist's conception of the surface of a magnetar, based on the best science available. The image shows the surface of the magnetar, almost perfectly spherical, and the complicated tentacles of the magnetar's magnetic field reaching out into space. Like neutron stars, magnetars rotate, but typically at a much slower rate than the typical neutron star. In early 2020 NASA'S Swift observatory detected a burst of high energy emission from a previously unknown source, powerful enough to outshine a half-million Suns. Followup observations of this source by Swift, and by the XMM-Newton X-ray observatory, the NuSTAR hard X-ray observatory, and radio observations using the Sardinia Radio Telescope revealed this object is astonishingly young magnetar, only about 240 years old, the youngest magnetar yet discovers. The magnetar lies at a distance of about 16,000 lightyears from earth, so the magnetar's activity actually happened about 16,000 years ago. Oddly, the magnetar also showed unusually bright, periodic radio emission. These observations suggest that this object may be an unusual link between older neutron stars (which shine from conversion of rotational energy to radiation) and young magnetars (which shine due to conversion of magnetic energy to radiation).

https://www.syfy.com/syfywire/a-magnetar-is-outbursting-again-right-on-schedule wrote:
A magnetar is outbursting again right on schedule
by Phil Plait@BadAstronomer, Aug 2, 2021

<<SGR1935+2154 is known to blast out gamma rays, and to do so more than once. This is where the new research comes in: although the individual bursts of energy from the magnetar come at random times, they appear in predictable groupings, what the astronomers call windows. What the astronomers noticed is that the SGR1935+2154 gamma ray flashes were all clustered in four-month-long windows separated by three-month intervals of quiescence. They used data from the KONUS gamma-ray instrument on board the spacecraft WIND, launched in 1994 to observe the Sun’s solar wind. But it can detect flashes of energy from other objects, and has seen them from SGR1935+2154 since 2014. Using clever statistical techniques, [these astronomers] made a prediction: The magnetar would start blasting away again on June 1, 2021 and should shut down once more in October.

And they were right. Or close enough: The three months before June 1 it was quiet, and the first burst was detected on June 24, three weeks into the window. Since then several more have been seen, including one as recently as July 6. The important part will come in October, if the magnetar shuts down again. But given the pattern, this does seem to be the way to bet.

The big question: Why does it do this?>>

https://en.wikipedia.org/wiki/SGR_1935%2B2154 wrote:

Click to play embedded YouTube video.

Click to play embedded YouTube video.

<<SGR 1935+2154 (or SGR J1935+2154) is a soft gamma repeater (SGR) that is an ancient stellar remnant, in the constellation Vulpecula, originally discovered in 2014 by the Neil Gehrels Swift Observatory. Currently, the SGR-phenomena and the related anomalous X-ray pulsars (AXP) are explained as arising from magnetars. On 28 April 2020, this remnant about 30,000 light-years away in our Milky Way galaxy was observed to be associated with a very powerful radio pulse known as a fast radio burst or FRB (designated FRB 200428), and a related x-ray flare. The detection is notable as the first FRB detected inside the Milky Way, and the first to be linked to a known source. Later in 2020, SGR 1935+2154 was found to be associated with repeating fast radio bursts.

The Swift Burst Alert Telescope first alerted the astronomical community to an increase in activity from the remnant with the detection of a flare on 27 April 2020. The next day, the Canadian Hydrogen Intensity Mapping Experiment (CHIME) first reported the detection of two bright radio bursts from 400 MHz to 800 MHz in the direction of the remnant, establishing the link between radio emission and the remnant. They estimated that the bursts had an energy similar to the brightest giant pulses from the Crab pulsar, which had never been seen from a magnetar. An independent detection of the bursts at 1.4 GHz by the STARE2 team established that the burst, now named FRB 200428, is similar to the fast radio bursts (FRBs) at extragalactic distances with their report that the fluence of the burst must be >1.5 MJy ms, more than a thousand times that reported by CHIME. At the distance of the closest known fast radio burst, FRB 200428 would have been detected with a fluence of >7 mJy ms. The INTEGRAL, Konus-Wind, Insight-HXMT, and AGILE telescopes then reported the detection of an X-ray burst from SGR 1935+2154 that occurred at the same time as the CHIME and STARE2 bursts, marking the first time an FRB had been associated with an X-ray source. To further secure the association of FRB 200428 with the remnant, the Five-hundred-meter Aperture Spherical Telescope (FAST) reported the detection of a much weaker radio burst, which was localized to within a maximal margin of error of a few arcminutes of the position of the remnant with a dispersion measure consistent with those reported by STARE2 and CHIME.

The NuSTAR, Swift, and NICER satellites observed several short X-ray bursts from the remnant on 29 April 2020 and 30 April 2020, confirming the magnetar was still in an active phase. The Very Large Array (VLA) followed the remnant 1–2 days after FRB 200428 and did not find any pulsed radio emission or an afterglow. The Deep Space Network (DSN) observed the remnant 1.5 to 3.5 days after the FRB and did not find evidence of periodic emission. LOFAR searched for other pulses from the remnant 1.5 days after FRB 200428 at 145 MHz and did not find any. Arecibo did not detect any bursts during a period of activity from the remnant in October 2019. Spektr-RG observed the remnant four days prior to FRB 200428 and found no evidence of flaring activity. Follow-up studies and observations have been reported. On 4 June 2020, astronomers reported "periodic radio pulsations" from the remnant with the Medicina Northern Cross (MNC) radio observatory on 30 May 2020. Another study was reported on 6 June 2020 of observations made earlier with the European VLBI Network on 13 May 2020. There have been other reported observations as well.>>