A repeating fast radio burst source in a globular cluster

Fast radio bursts (FRBs) are flashes of unknown physical origin¹. The majority of FRBs have been seen only once, although some are known to generate multiple flashes^2,3. Many models invoke magnetically powered neutron stars (magnetars) as the source of the emission^4,5. Recently, the discovery⁶ of another repeater (FRB 20200120E) was announced, in the direction of the nearby galaxy M81, with four potential counterparts at other wavelengths⁶. Here we report observations that localized the FRB to a globular cluster associated with M81, where it is 2 parsecs away from the optical centre of the cluster. Globular clusters host old stellar populations, challenging FRB models that invoke young magnetars formed in a core-collapse supernova. We propose instead that FRB 20200120E originates from a highly magnetized neutron star formed either through the accretion-induced collapse of a white dwarf, or the merger of compact stars in a binary system⁷. Compact binaries are efficiently formed inside globular clusters, so a model invoking them could also be responsible for the observed bursts.

A direct localization of a fast radio burst and its host

Fast radio bursts are astronomical radio flashes of unknown physical nature with durations of milliseconds. Their dispersive arrival times suggest an extragalactic origin and imply radio luminosities that are orders of magnitude larger than those of all known short-duration radio transients. So far all fast radio bursts have been detected with large single-dish telescopes with arcminute localizations, and attempts to identify their counterparts (source or host galaxy) have relied on the contemporaneous variability of field sources or the presence of peculiar field stars or galaxies. These attempts have not resulted in an unambiguous association with a host or multi-wavelength counterpart. Here we report the subarcsecond localization of the fast radio burst FRB 121102, the only known repeating burst source, using high-time-resolution radio interferometric observations that directly image the bursts. Our precise localization reveals that FRB 121102 originates within 100 milliarcseconds of a faint 180-microJansky persistent radio source with a continuum spectrum that is consistent with non-thermal emission, and a faint (twenty-fifth magnitude) optical counterpart. The flux density of the persistent radio source varies by around ten per cent on day timescales, and very long baseline radio interferometry yields an angular size of less than 1.7 milliarcseconds. Our observations are inconsistent with the fast radio burst having a Galactic origin or its source being located within a prominent star-forming galaxy. Instead, the source appears to be co-located with a low-luminosity active galactic nucleus or a previously unknown type of extragalactic source. Localization and identification of a host or counterpart has been essential to understanding the origins and physics of other kinds of transient events, including gamma-ray bursts and tidal disruption events. However, if other fast radio bursts have similarly faint radio and optical counterparts, our findings imply that direct subarcsecond localizations may be the only way to provide reliable associations.

A strong magnetic field around the supermassive black hole at the centre of the Galaxy

Earth's nearest candidate supermassive black hole lies at the centre of the Milky Way. Its electromagnetic emission is thought to be powered by radiatively inefficient accretion of gas from its environment, which is a standard mode of energy supply for most galactic nuclei. X-ray measurements have already resolved a tenuous hot gas component from which the black hole can be fed. The magnetization of the gas, however, which is a crucial parameter determining the structure of the accretion flow, remains unknown. Strong magnetic fields can influence the dynamics of accretion, remove angular momentum from the infalling gas, expel matter through relativistic jets and lead to synchrotron emission such as that previously observed. Here we report multi-frequency radio measurements of a newly discovered pulsar close to the Galactic Centre and show that the pulsar's unusually large Faraday rotation (the rotation of the plane of polarization of the emission in the presence of an external magnetic field) indicates that there is a dynamically important magnetic field near the black hole. If this field is accreted down to the event horizon it provides enough magnetic flux to explain the observed emission--from radio to X-ray wavelengths--from the black hole.

Gamma-ray emission concurrent with the nova in the symbiotic binary V407 Cygni

Novae are thermonuclear explosions on a white dwarf surface fueled by mass accreted from a companion star. Current physical models posit that shocked expanding gas from the nova shell can produce x-ray emission, but emission at higher energies has not been widely expected. Here, we report the Fermi Large Area Telescope detection of variable gamma-ray emission (0.1 to 10 billion electron volts) from the recently detected optical nova of the symbiotic star V407 Cygni. We propose that the material of the nova shell interacts with the dense ambient medium of the red giant primary and that particles can be accelerated effectively to produce pi(0) decay gamma-rays from proton-proton interactions. Emission involving inverse Compton scattering of the red giant radiation is also considered and is not ruled out.

Isolated pulmonary artery stenosis: four-year follow-up: case report

The authors present a four-year follow-up of a patient with a single isolated right main pulmonary artery stenosis without an associated cardiac anomaly. This is an extremely uncommon lesion thought to be congenital. This case illustrates the stability of isolated lesions of the pulmonary vasculature without associated cardiac defects.

Active tuberculosis in the medical intensive care unit: a 15-year retrospective analysis

Of approximately 6000 admissions to the Henry Ford Hospital medical ICU between October 1969 and September 1984, 61 (1%) had active tuberculosis (TB). Forty-three (70%) of these 61 had acute respiratory failure (ARF). TB was considered to be the sole cause of ARF in 12 and contributory in 31. Eighteen patients with TB but without ARF were admitted for treatment of other critical illnesses. Alcoholism was present in 31 (51%) of the TB patients. Only one of 12 whose ARF was caused primarily by TB had a history of known TB at the time of admission. Important factors contributing to ARF in TB patients included Gram-negative pneumonia and/or sepsis, chronic obstructive pulmonary disease, prior TB with anti-TB medication noncompliance, and malignancy. Six patients were not suspected of having TB when admitted to the medical ICU; three patients who had not been treated for TB were found to have TB on autopsy. The inhospital mortality rate for all patients with TB requiring intensive care was 67%, but was 81% in those with ARF.

The significance of facial burns in acute smoke inhalation

The medical records of 21 patients with smoke inhalation admitted to a medical ICU (MICU) were reviewed. Of 21 patients, 6 (29%) died. Of 21 patients, 13 (62%) had facial burns and 11 of the 13 (85%) later developed pneumonia. Only 1 of 8 patients (12%) without facial burns developed pneumonia (p less than 0.005). Of the 12 patients with pneumonia, 7 required ventilatory assistance and 6 of the 7 died in the MICU. The authors conclude that the presence of facial burns is associated with the later development of pneumonia in a high percentage of cases. Pneumonia contributes significantly to the high mortality rate. The need for ventilatory assistance in smoke inhalation patients is associated with a poor prognosis.

Hypersomnolence and intermittent upper airway obstruction. Occurrence caused by micrognathia

A patient with hypersomnolence, micrognathia, and respiratory insufficiency had been treated eight years for narcolepsy. Sleep apnea because of upper airway obstruction was found, and a tracheostomy was performed. Following this the hypersomnolence and respiratory insufficiency resolved. This case emphasizes the importance of carefully evaluating the condition of patients complaining of hypersomnolence to detect those with intermittent upper airway obstruction occurring during sleep.

Acute pulmonary hypersensitivity to carbamazepine

Acute pulmonary hypersensitivity to carbamazepine (Tegretol) is reported, manifested by diffuse pulmonary infiltrates, skin rash, and eosinophilia. The reaction cleared on cessation of the drug. A lymphocyte transformation test was reactive to carbamazepine.