From IAC-The Institute of Astrophysics of the Canary Islands [Instituto de Astrofísica de Canarias](ES): “Astronomers observe potential magnetic flip around a supermassive black hole”
05/05/2022 [Just now in social media.]
Contacts at the IAC:
José Acosta,
jose.acosta@iac.es
Josefa Becerra,
josefa.becerra.gonzalez@iac.es
Artist’s impression of the unusual eruption of the galaxy 1ES 1927+654. A sudden reversal of the magnetic field around its million-solar-mass black hole may have triggered the outburst. Credit: NASA.
An international research, in which a team from the Instituto de Astrofísica de Canarias (IAC) has participated, has provided new evidence for an enigmatic outburst from a galaxy 216 million light-years away, proposing a new interpretation based on a spontaneous flip of the magnetic field surrounding its central black hole. The study has used joint data from different satellites and telescopes, including the Telescopio Nazionale Galileo (TNG) [below] and the Gran Telescopio Canarias (GTC)[below], both located at the Roque de los Muchachos Observatory (Garafía, La Palma). The results will be published in the coming days in The Astrophysical Journal.
In early March 2018, the All-Sky Automated Survey for Supernovae alerted astronomers that a galaxy called 1ES 1927+654 had brightened by nearly 100 times in visible light. A search for earlier detection by the NASA-funded Asteroid Terrestrial-impact Last Alert System showed that the eruption had begun months earlier, at the end of 2017. Three months after the discovery the X-ray emission from the galaxy disappeared.
“Rapid changes in visible and ultraviolet light have been seen in a few dozen galaxies similar to this one,” says Sibasish Laha, a research scientist at the University of Maryland and NASA’s Goddard Space Flight Center in the United States. “But this event marks the first time we’ve seen X-rays dropping out completely while the other wavelengths brighten.”
“An earlier interpretation of the eruption suggested that it was triggered by a star that passed so close to the black hole it was torn apart, disrupting the flow of gas,” says Josefa Becerra, researcher at the IAC and co-author of the article. “However, such an event would fade out more rapidly than this outburst.”
The research team analyzed new and archival observations across the spectrum. NASA’s Neil Gehrels Swift Observatory and ESA’s (European Space Agency) XMM-Newton satellite provided UV and X-ray measurements.
Visible light observations came from the Telescopio Nazionale Galileo (TNG) and the Gran Telescopio Canarias (GTC or Grantecan), both located at the Roque de los Muchachos Observatory on the island of La Palma. Radio measurements were acquired from the Very Long Baseline Array, a network of 10 radio telescopes located across the United States; the Very Large Array in New Mexico; and the European VLBI Network.
“The high quality of the GTC/OSIRIS spectrum allows us to disentangle the stellar contribution from that of the active core,” says José Acosta, IAC researcher and co-author of the paper. “The stellar population of the host galaxy is dominated by young stars and the nuclear spectrum is dominated by strong emission lines,” he says.
Most big galaxies, including our own Milky Way, host a supermassive black hole weighing millions to billions of times the Sun’s mass. When matter falls toward one, it first collects into a vast, flattened structure called an accretion disk. As the material slowly swirls inward, it heats up and emits visible, UV, and lower-energy X-ray light. Near the black hole, a cloud of extremely hot particles – called the corona – produces higher-energy X-rays. The brightness of these emissions depends on how much material streams toward the black hole.
The unique disappearance of the X-ray emission provides astronomers with an important clue. They suspect the black hole’s magnetic field creates and sustains the corona, so any magnetic change could impact its X-ray properties. “A magnetic reversal, where the north pole becomes south and vice versa, seems to best fit the observations,” says co-author Mitchell Begelman, a professor in the department of astrophysical and planetary sciences at the University of Colorado-Boulder who developed the model. “The field initially weakens at the outskirts of the accretion disk, leading to greater heating and brightening in visible and UV light,” he explains.
As the flip progresses, the field becomes so weak that it can no longer support the corona and the X-ray emission vanishes. The magnetic field then gradually strengthens in its new orientation. In Oct 2018, about 3-4 months after they disappeared, the X-rays came back, indicating that the corona had been fully restored.
Magnetic reversals are likely to be common events in the cosmos. The geologic record shows that Earth’s field flips unpredictably, averaging a few reversals every million years in the recent past. The Sun, by contrast, undergoes a magnetic reversal as part of its normal cycle of activity, switching north and south poles roughly every 11 years.
See the full article here .
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IAC-The Institute of Astrophysics of the Canary Islands [Instituto de Astrofísica de Canarias] (ES) operates two astronomical observatories in the Canary Islands:
Roque de los Muchachos Observatory on La Palma
Teide Observatory on Tenerife.
The Instituto de Astrofísica the headquarters, which is in La Laguna (Tenerife).
Observatorio del Roque de los Muchachos at La Palma (ES) at an altitude of 2400m.
The seeing statistics at ORM make it the second-best location for optical and infrared astronomy in the Northern Hemisphere, after Mauna Kea Observatory Hawaii (US).
Maunakea Observatories Hawai’i (US) altitude 4,213 m (13,822 ft).
The site also has some of the most extensive astronomical facilities in the Northern Hemisphere; its fleet of telescopes includes the 10.4 m Gran Telescopio Canarias, the world’s largest single-aperture optical telescope as of July 2009; the Telescopio Nazionale Galileo (IT) (ES) a 3.58-meter Italian telescope; the William Herschel Telescope (second largest in Europe), and the adaptive optics corrected Swedish 1-m Solar Telescope.
Gran Telescopio Canarias [Instituto de Astrofísica de Canarias ](ES) sited on a volcanic peak 2,267 metres (7,438 ft) above sea level.
Isaac Newton Group 4.2 meter William Herschel Telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands(ES), 2,396 m (7,861 ft).
The Swedish 1m Solar Telescope SST at the Roque de los Muchachos observatory on La Palma Spain, Altitude 2,360 m (7,740 ft).
The observatory was established in 1985, after 15 years of international work and cooperation of several countries with the Spanish island hosting many telescopes from Britain, The Netherlands, Spain, and other countries. The island provided better seeing conditions for the telescopes that had been moved to Herstmonceux by the Royal Greenwich Observatory, including the 98 inch aperture Isaac Newton Telescope (the largest reflector in Europe at that time). When it was moved to the island it was upgraded to a 100-inch (2.54 meter), and many even larger telescopes from various nations would be hosted there.
Tiede Observatory, Tenerife, Canary Islands (ES)
Teide Observatory [Observatorio del Teide], IAU code 954, is an astronomical observatory on Mount Teide at 2,390 metres (7,840 ft), located on Tenerife, Spain. It has been operated by the Instituto de Astrofísica de Canarias since its inauguration in 1964. It became one of the first major international observatories, attracting telescopes from different countries around the world because of the good astronomical seeing conditions. Later the emphasis for optical telescopes shifted more towards Roque de los Muchachos Observatory on La Palma.
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