From The California Institute of Technology (US) via : “Persistent radio source QRS121102 investigated in detail”

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From The California Institute of Technology (US)


January 11, 2022
Tomasz Nowakowski

VLA images (in J2000 coordinates) of QRS121102 in seven epochs, with band indicated in parentheses. Credit: Ge Chen et al., 2022.

National Radio Astronomy Observatory(US)Karl G Jansky Very Large Array located in central New Mexico on the Plains of San Agustin, between the towns of Magdalena and Datil, ~50 miles (80 km) west of Socorro. The VLA comprises twenty-eight 25-meter radio telescopes.

Astronomers from the California Institute of Technology (Caltech) have investigated a persistent radio source known as QRS121102 that is associated with the fast radio burst FRB 121102. Results of the study, published January 4 in The Astrophysical Journal, shed more light on the origin of this source and could help us better understand the nature of fast radio bursts.

Fast radio bursts (FRBs) are intense bursts of radio emission lasting milliseconds and showcasing characteristic dispersion sweep of radio pulsars. The physical nature of these bursts is yet unknown, and astronomers consider a variety of explanations ranging from synchrotron maser emission from young magnetars in supernova remnants to cosmic string cusps.

FRB 121102 is the first repeating fast radio burst detected and one of the most extensively studied FRB sources. It exhibits complex burst morphology, sub-burst downward frequency drifts, and also complex pulse phenomenology. FRB 121102 is also one of only two FRBs reported to be spatially associated with persistent radio emission of unknown origin.

A team of astronomers led by Caltech’s Ge Chen took a closer look at this persistent radio source. For this purpose, they observed QRS121102 with the G. Jansky Very Large Array (VLA)[above] and the Low-Resolution Imaging Spectrometer (LRIS) at the Keck Observatory.

UCO Keck LRIS on Keck 1.

W.M. Keck Observatory two ten meter telescopes operated by California Institute of Technology(US) and The University of California(US), at Mauna Kea Observatory, Hawaii USA, altitude 4,207 m (13,802 ft). Credit: Caltech.

“In this work, we investigated the origin of the persistent radio source, QRS121102, associated with FRB 121102. We present new VLA monitoring data (12 to 26 GHz) and new spectra from Keck/LRIS,” the researchers wrote in the paper.

The observations allowed the team to estimate the physical size of QRS121102. It was found that the emission radius is most likely between 0.1 and 1 light year. Such a relatively small size suggests a few compact radio source candidates, for instance, active galactic nuclei (AGN), pulsar wind nebulae (PWNe), very young supernova remnants (SNRs) and gamma-ray burst (GRB) afterglows.

Given that QRS121102 may be an AGN, the astronomers constrained the mass of the potential black hole. They found that this mass would be lower than 100,000 solar masses, which does not support the AGN scenario as this source is too faint in the X-ray for its calculated low black hole mass and bright radio emission.

The radio luminosity of QRS121102, from 400 MHz to 10 GHz, was measured to be approximately 20 billion TW/Hz. Therefore, according to the researchers, this source is too luminous to be an SNR. It was added that QRS121102 is also too bright to be a long-duration GRB (LGRB) radio afterglow.

Summing up the results, the researchers noted that it is too early to draw final conclusions regarding the true origin of QRS121102 and further observations are required in order to get more insights into the nature of this source.

“We urge continued broadband radio monitoring of QRS121102 to search for long-term evolution, and the detailed evaluation of potential analogs that may provide greater insight into the nature of this remarkable, mysterious class of object,” the authors of the paper concluded.

See the full article here .


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The The California Institute of Technology (US) is a private research university in Pasadena, California. The university is known for its strength in science and engineering, and is one among a small group of institutes of technology in the United States which is primarily devoted to the instruction of pure and applied sciences.

The California Institute of Technology was founded as a preparatory and vocational school by Amos G. Throop in 1891 and began attracting influential scientists such as George Ellery Hale, Arthur Amos Noyes, and Robert Andrews Millikan in the early 20th century. The vocational and preparatory schools were disbanded and spun off in 1910 and the college assumed its present name in 1920. In 1934, The California Institute of Technology was elected to the Association of American Universities, and the antecedents of National Aeronautics and Space Administration (US)’s Jet Propulsion Laboratory, which The California Institute of Technology continues to manage and operate, were established between 1936 and 1943 under Theodore von Kármán.

The California Institute of Technology has six academic divisions with strong emphasis on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. First-year students are required to live on campus, and 95% of undergraduates remain in the on-campus House System at The California Institute of Technology. Although The California Institute of Technology has a strong tradition of practical jokes and pranks, student life is governed by an honor code which allows faculty to assign take-home examinations. The The California Institute of Technology Beavers compete in 13 intercollegiate sports in the NCAA Division III’s Southern California Intercollegiate Athletic Conference (SCIAC).

As of October 2020, there are 76 Nobel laureates who have been affiliated with The California Institute of Technology, including 40 alumni and faculty members (41 prizes, with chemist Linus Pauling being the only individual in history to win two unshared prizes). In addition, 4 Fields Medalists and 6 Turing Award winners have been affiliated with The California Institute of Technology. There are 8 Crafoord Laureates and 56 non-emeritus faculty members (as well as many emeritus faculty members) who have been elected to one of the United States National Academies. Four Chief Scientists of the U.S. Air Force and 71 have won the United States National Medal of Science or Technology. Numerous faculty members are associated with the Howard Hughes Medical Institute(US) as well as National Aeronautics and Space Administration(US). According to a 2015 Pomona College(US) study, The California Institute of Technology ranked number one in the U.S. for the percentage of its graduates who go on to earn a PhD.


The California Institute of Technology is classified among “R1: Doctoral Universities – Very High Research Activity”. Caltech was elected to The Association of American Universities in 1934 and remains a research university with “very high” research activity, primarily in STEM fields. The largest federal agencies contributing to research are National Aeronautics and Space Administration(US); National Science Foundation(US); Department of Health and Human Services(US); Department of Defense(US), and Department of Energy(US).

In 2005, The California Institute of Technology had 739,000 square feet (68,700 m^2) dedicated to research: 330,000 square feet (30,700 m^2) to physical sciences, 163,000 square feet (15,100 m^2) to engineering, and 160,000 square feet (14,900 m^2) to biological sciences.

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