Passage:
The detection of the so-called Lorimer Burst in 2007 heralded the discovery of a new astronomical phenomenon: fast radio bursts (FRBs). These are intensely bright, millisecond-duration pulses of radio emission that appear randomly in the sky. The brevity of the bursts implies that the emitting region must be incredibly small—no larger than a few hundred kilometers across—which points to compact objects like neutron stars or black holes as the likely sources. Initially, the most compelling clue regarding their origin was their "dispersion measure"—a quantification of the delay between the arrival of high-frequency and low-frequency radio waves. Because lower frequencies are slowed more by free electrons in space than higher frequencies, a large dispersion measure strongly indicates that the signal has traveled across vast cosmic distances, definitively placing the origin of most FRBs outside the Milky Way galaxy.
For nearly a decade following the Lorimer Burst, all detected FRBs were singular, isolated events. Consequently, the prevailing astrophysical models posited cataclysmic origins—events that inherently destroy the source object. Theoretical explanations heavily favored the mergers of binary neutron stars or the collapse of a supramassive neutron star into a black hole. However, the landscape shifted dramatically with the observation of FRB 121102. Unlike its predecessors, FRB 121102 emitted multiple bursts over time. This crucial observation of repetition unequivocally demonstrated that the source of at least this particular FRB survived the emission process, effectively ruling out cataclysmic models for repeating bursts.
The discovery of repetition invigorated an alternative hypothesis: that FRBs are powered by magnetars, which are young, highly magnetized neutron stars capable of surviving repeated outbursts. This model gained substantial empirical support in 2020 when astronomers detected an FRB-like radio pulse emanating from SGR 1935+2154, a known magnetar located within our own galaxy. Crucially, this radio burst was accompanied by a simultaneous burst of X-rays, matching the theoretical predictions of magnetar emission models.
Despite this breakthrough, a consensus has yet to emerge regarding whether a single unified mechanism can explain all FRBs. Some researchers argue that all FRBs are produced by magnetars, suggesting that apparent non-repeaters are simply repeaters with extremely long intervals between bursts. In contrast, researchers such as Dr. Elena Rostova maintain a dichotomous view, arguing that while repeating FRBs are indeed generated by magnetars in dense environments, the genuinely non-repeating FRBs are the product of the cataclysmic mergers previously theorized.
Based on the passage, which of the following statements about fast radio bursts are explicitly supported? (Select all that apply)
- A substantial dispersion measure serves as evidence that a fast radio burst has traveled across vast cosmic distances, originating outside of our galaxy.Answer
- Prior to the observation of FRB 121102, astrophysical models primarily proposed that fast radio bursts resulted from events that inherently destroyed the emitting object.Answer
- CThe Lorimer Burst was the first recorded instance of a fast radio burst emitting multiple millisecond-duration radio pulses over an extended period.
- DThe detection of a radio pulse from SGR 1935+2154 conclusively proved to the astronomical community that all fast radio bursts are powered by highly magnetized neutron stars.
- EDr. Elena Rostova theorizes that repeating fast radio bursts, such as FRB 121102, are generated by the cataclysmic merger of binary neutron stars.