soft gamma repeater
A soft gamma repeater (SGR) is an astronomical object which emits large bursts of gamma-rays and X-rays at irregular intervals. It is conjectured that they are a type of magnetar or, alternatively, neutron stars with fossil disks around them.
Hi ...
(SGR) that is an ancient stellar remnant, in the constellation
Vulpecula
Vulpecula is a faint constellation in the northern sky. Its name is Latin for "little fox", although it is commonly known simply as the fox. It was identified in the seventeenth century, and is located in the middle of the Summer Triangle (an ...
, originally discovered in 2014 by the
Neil Gehrels Swift Observatory
Neil Gehrels Swift Observatory, previously called the Swift Gamma-Ray Burst Explorer, is a NASA three-telescope space observatory for studying gamma-ray bursts (GRBs) and monitoring the afterglow in X-ray, and UV/Visible light at the location o ...
. Currently, the SGR-phenomena and the related
anomalous X-ray pulsar
Anomalous X-ray pulsars (AXPs) are an observational manifestation of magnetars—young, isolated, highly magnetized neutron stars. These energetic X-ray pulsars are characterized by slow rotation periods of ~2–12 seconds and large magnetic fields ...
s (AXP) are explained as arising from
magnetar
A magnetar is a type of neutron star with an extremely powerful magnetic field (∼109 to 1011 T, ∼1013 to 1015 G). The magnetic-field decay powers the emission of high-energy electromagnetic radiation, particularly X-rays and gamma rays.War ...
s. On 28 April 2020, this remnant about away in our
Milky Way
The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. ...
galaxy was observed to be associated with a very powerful radio pulse known as a
fast radio burst
In radio astronomy, a fast radio burst (FRB) is a transient radio pulse of length ranging from a fraction of a millisecond to 3 seconds, caused by some high-energy astrophysical process not yet understood. Astronomers estimate the average FRB rel ...
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.
History
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
The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is an interferometric radio telescope at the Dominion Radio Astrophysical Observatory in British Columbia, Canada which consists of four antennas consisting of 100 x 20 metre cylindrical ...
(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
The Crab Pulsar (PSR B0531+21) is a relatively young neutron star. The star is the central star in the Crab Nebula, a remnant of the supernova SN 1054, which was widely observed on Earth in the year 1054. 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
In mathematics, an integral assigns numbers to functions in a way that describes displacement, area, volume, and other concepts that arise by combining infinitesimal data. The process of finding integrals is called integration. Along wit ...
, 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
The Five-hundred-meter Aperture Spherical radio Telescope (FAST; ), nicknamed Tianyan (, lit. "Sky's/Heaven's Eye"), is a radio telescope located in the Dawodang depression (), a natural basin in Pingtang County, Guizhou, southwest China. FAST ...
(FAST) reported the detection of a much weaker radio burst, which was localized to within a maximal
margin of error
The margin of error is a statistic expressing the amount of random sampling error in the results of a survey. The larger the margin of error, the less confidence one should have that a poll result would reflect the result of a census of the e ...
of a few arcminutes of the position of the remnant with a dispersion measure consistent with those reported by STARE2 and CHIME.
The
NuSTAR
NuSTAR (Nuclear Spectroscopic Telescope Array, also named Explorer 93 and SMEX-11) is a NASA space-based X-ray telescope that uses a conical approximation to a Wolter telescope to focus high energy X-rays from astrophysical sources, especiall ...
, Swift, and
NICER
The Neutron Star Interior Composition ExploreR (NICER) is a NASA telescope on the International Space Station, designed and dedicated to the study of the extraordinary gravitational, electromagnetic, and nuclear physics environments embodied by ...
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
The Karl G. Jansky Very Large Array (VLA) is a centimeter-wavelength radio astronomy observatory located in central New Mexico on the Plains of San Agustin, between the towns of Magdalena and Datil, ~ west of Socorro. The VLA comprises twent ...
(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
The NASA Deep Space Network (DSN) is a worldwide network of American spacecraft communication ground segment facilities, located in the United States (California), Spain (Madrid), and Australia (Canberra), that supports NASA's interplanetary ...
(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
Arecibo (; ) is a city and municipality on the northern coast of Puerto Rico, on the shores of the Atlantic Ocean, located north of Utuado and Ciales; east of Hatillo; and west of Barceloneta and Florida. It is about west of San Juan, th ...
did not detect any bursts during a period of activity from the remnant in October 2019.
Spektr-RG
Spektr-RG ( Russian: Спектр-РГ, ''Spectrum'' + '' Röntgen'' + ''Gamma''; also called Spectrum-X-Gamma, SRG, SXG) is a Russian–German high-energy astrophysics space observatory which was launched on 13 July 2019. It follows on from th ...
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
The European VLBI Network (EVN) is a network of radio telescopes located primarily in Europe and Asia, with additional antennas in South Africa and Puerto Rico, which performs very high angular resolution observations of cosmic radio sources usin ...
on 13 May 2020. There have been other reported observations as well.