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Astronomers detect five young stars in the Chamaeleon cloud complex

Using the Australia Telescope Compact Array (ATCA), astronomers have performed large-scale radio observations of a star-forming region known as the Chamaeleon cloud complex. The observational campaign, which detected five young stars in Chamaeleon, may shed more light on the properties of this complex. The were detailed in a paper published June 19 on the arXiv pre-print server.

Star-forming regions are perceived by astronomers as essential for better understanding the processes of star formation and stellar evolution. Observations of such regions are crucial to expand the list of known stars, protostars, young stellar objects (YSOs) and clumps, which could then be studied comprehensively to get more insights into the initial stages of the stellar life cycle.

The Chamaeleon cloud complex is a prominent star-forming region in the southern hemisphere, at a distance of some 620 light years. It harbors three main dark clouds, designated Cha I, Cha II and Cha III.

Previous studies have found that Cha I contains about 250 pre-main sequence (PMS) stars, while Cha II has less than 100 stellar members. The age of Cha I and Cha II is estimated to be two million years, while Cha III appears to be at an earlier evolutionary phase where star-formation is yet to occur.

A team of astronomers led by Ernesto Garcia Valencia of the University of Sonora, Mexico, decided to employ ATCA in order to conduct large-scale high-resolution radio observations of Chamaeleon, searching for new stars. As a result, they detected radio emission from five young stars.

According to the paper, three of the five detected stars are fairly evolved low-mass T Tauri stars. One of them is a protostellar object and one turned out to be a Herbig Ae/Be star. The astronomers noted that the radio emission mechanism is likely of non-thermal origin in these stars, except the protostellar object.

The detected radio sources were further inspected by Valencia's team using the Australian Long Baseline Array (LBA). The LBA observations found that one of them, designated J11061540−7721567, may be a tight binary system with an orbital period of about 40 years, a mass of approximately 1.0 solar masses, and a semi-major axis of 12 AU.

Moreover, the ATCA observations also led to the tentative detection of five more young stars in Chamaeleon. However, these objects require further observation to confirm.

In concluding remarks, the authors of the paper sum up the efficiency of detecting new sources in Chamaeleon using ATCA.

"Since the surveyed region includes a total of 201 young stars, the detection rate is between 2.5% and 5%. This is somewhat lower than in other star-forming regions," the scientists conclude.