(ORDO NEWS) — Using the Indian Astronomical Observatory (IAO) at Khanle, astronomers have observed a globular cluster known as NGC 7006.
The results of the study, presented Dec. 9 on the arXiv preprint server, provide important information about the properties of the cluster’s stellar population.
Globular clusters are clusters of closely related stars orbiting galaxies. Astronomers perceive them as natural laboratories to study the evolution of stars and galaxies.
In particular, globular clusters could help researchers better understand the history of formation and evolution of early-type galaxies, since their origin is closely related to periods of intense star formation.
NGC 7006 (also known as Caldwell 42) is located about 137,000 light-years away in the constellation Dolphin. This is a globular cluster.
Its estimated mass is about 300,000 solar masses. Previous observations of NGC 7006 have shown that it contains at least 76 variable stars, of which 64 are found to be RR Lyrae variables.
To shed more light on the population of variable stars in NGC 7006, a team of astronomers led by Armando Arellano Ferro of the National Autonomous University of Mexico made photometric observations of variable stars in the cluster region.
The team was able to identify 470 stars that are likely members of NGC 7006. They then searched for variable stars in that sample.
As a result, 10 new variables were discovered: two RR Lyrae stars of the RRc subtype (V77 and V78), two RR Lyrae stars of the RRab subtype (V79 and V80), one BL Hercules star (V81), and five semi-regular (SR) variables ( V82, V83, V84, V85 and V86).
The average period of RRab stars in NGC 7006 was calculated as 0.577 days, and the proportion of RRc stars in this cluster was approximately 0.14.
The study found that the weighted average radius and mass of all known RRab variables in NGC 7006 are 5.61 solar radii and 0.67 solar masses. For RRc stars, these values ​​have been measured as 4.27 solar radii and 0.55 solar masses.
The collected data also allowed scientists to get some fundamental parameters of NGC 7006. They found that the cluster is located about 134,200 light years from Earth, has a metallicity of -1.53, and its redness is at the level of 0.08.
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