In the latest edition of the scientific investigations, it has come to light that the Chandra X-Ray Observatory of NASA has been employed by an international team of astronomers to investigate a supergiant star called Wd1-9. It has certainly performed a detailed investigation, which was accompanied by in-depth analysis and offered essential insights. Considering the supergiant B Stars, these are quite rare in the Milky Way. As these stars grow, they undergo continuous changes. These stars also exhibit strong Balmore emission lines, forbidden lines, and infrared excess.
Wd1-9: What is this Supergiant B Star?
Wd1-9 is a supergiant B (e) star in Westerlund 1. It is located at a distance of 13,800 light years from Earth. This star is the brightest radio source present within the cluster. Likewise, the recent findings presented in the paper published on July 23rd, 2025, suggest that this star displays a rich emission-line spectrum. Significantly, no photospheric features were detected.
Although Wd1-9 has been studied multiple times at different wavelengths, its true nature is still unknown due to it being covered by a cloud of dust. As the previous research suggests, this star may be a cool hypergiant or an interacting binary system. Now, to overcome these suspicions, Konstantina Anastasopolou led a team of the Harvard-Smithsonian Center for Astrophysics (CfA), Cambridge, employed Chandra to dig deeper.
What did the Astronomers Find?
As per the observations offered by Chandra, it was witnessed that Wd1-9 exhibits long-term X-ray variability. The team further identified an orbital period that comprised a 14-day periodic signal. According to the astronomers, this is the first period determination for the Wd1-9.
Significantly, the astronomers found that strong emission lines were detected that surfaced from elements like silicon, sulfur, and argon. Similarly, the iron emission line at 6.7 keV was identified for the first time ever. These identifications have become a part of the new findings.
To Conclude
According to the astronomers, the above-specified findings directly relate to binarity. The spectrum of Wd1-9 resembles the Wolf-Rayet (WR) binaries in Westerlund 1. Also, when the astronomers examined the X-Ray color-color diagrams, they identified that Wd1-9 showcased variations in thermal temperatures. After analysing the findings and putting all the examinations together, the scientists concluded that Wd1-9 is a part of the binary system.
