麻豆淫院

Astronomers from the Czech Republic and Argentina have employed the Gemini South telescope to observe a yellow supergiant star designated HD 144812. The observations found that HD 144812 is a rare post-red supergiant orbited by a companion star. The finding was reported in a paper March 25 on the arXiv pre-print server.

Yellow supergiant stars (YSGs) have spectral types F or G and initial masses between 10 and 40 solar masses. Most YSGs are cooling and expanding rapidly towards red supergiants (RSGs) after leaving the main sequence, spending only a few thousand years in that phase.

Observations show that periods of enhanced circumstellar wind activity can drive stars off the RSG branch of the HR Diagram. This phase, known as post-RSG evolution, may well be tied to high mass-loss events or eruptions as seen in the Luminous Blue Variables (LBVs) and other massive stars.

In order to increase the number of known post-RSG stars in the Milky Way and nearby galaxies, a team of astronomers led by Michalis Kourniotis of the Czech Academy of Sciences have been carrying out spectroscopic observations of YSGs with infrared excess.

One of the stars targeted by the researchers was HD 144812. Located some 2,500 light years away, HD 144812 is a star first identified in 1978 as a Galactic emission-line YSG. The star showcases infrared excess typically expected for evolved stars undergoing enhanced mass-loss activity.

Kourniotis' team obtained high-resolution spectroscopy of HD 144812 with the GRating INfrared Spectrometer (IGRINS) at the Gemini South telescope. The observations revealed a wealth of photospheric absorption lines, also containing distinctive emission features, mostly from the hydrogen series and from iron. It appears that the most pronounced feature in the K鈭抌and spectrum of the star is the emission from the first-overtone bands of the carbon monoxide molecule.

According to the authors of the paper, the findings suggest that HD 144812 is orbited by a disk-hosting companion. The disk likely consists of material that has been dredged up from the core of the star to its surface during a prior phase as a red supergiant.

Furthermore, the analysis of the carbon monoxide emission indicates that HD 144812 is found in a post-RSG phase evolving bluewards. It was noted that the processed, ejected gas from the surface of the star emits in the form of a disk.

All in all, the researchers concluded that HD 144812 is a rare example of a post-RSG star in a binary system.

"The yellow super(hyper)giant HD 144812 complements the sparse sample of post-RSGs identified in binary systems, offering valuable insights into the late evolutionary stages of massive stars," the scientists write.

They now plan to monitor HD 144812 in both the infrared and optical bands in order to get more insights into the kinematics and properties of the system.

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