Tomasz Nowakowski is a writer for the website Phys.org.
The image is showing a group of objects. Credit: NASA/Ames
A group of subdwarf B stars in an open cluster have been investigated by an international team using NASA's Kepler and the MMT telescope in Arizona. The results of the study were published on arXiv.org, and they provide important information about the properties of these stars.
The hot subdwarf B stars are made of very thin hydrogen envelopes. They are small, typically half the size of the sun, with effective temperatures ranging from 20,000 to 40,000 K.
Astronomers are interested in finding and analyzing pulsating subdwarf B stars, which show two types of variation. The first is associated with short period pressure modes, with pulsation periods of the order of minutes and pulsation modes reaching tens of mmag. The second is due to long-period gravity modes that have pulsation periods of the order of hours.
A group of researchers, led by Sachu Sanjayan of the Pedagogical University of Cracow in Poland, have been searching for sdBVs in the open cluster NGC 6791, which is about 8 billion years old. The cluster is 13,300 light years away in the Lyra constellation, and has a large population of stars.
The goal of our work was to find all sdBV stars in the same place, provide the mode identification of detected modes, derive parameters by means of asteroseismology, and compare them with parameters of field counterparts," the astronomer wrote in the paper.
KIC 2569576 (B3), KIC 2438324 (B4) and KIC 2437937 were identified by the team. The stars were classified as pulsators by previous research, but now have extended time coverage and higher quality data. They were able to confirm frequencies already reported in the g-mode region.
The temperatures of B3 were measured to be 24,250, B4 was measured to be 24,786 and B5 was measured to be 23,844 K. B4 is a system with a sdBV star and a main sequence companion that has an orbital period of about nine hours. The authors of the paper did not exclude the possibility that B3 and B5 may also be a pair.
Four other hot stars were identified as cluster members by the astronomer. These objects show no photometric variability. The researchers said that the remaining sdBs in NGC 6791 don't show any light variations down to their detection thresholds.
S.Sanjayan and his team found subdwarf B stars in the oldest open cluster.
The Science X Network will be launched in 2021.
The study looked at subdwarf B stars in the open cluster.
The document is copyrighted. Any fair dealing for the purpose of private study or research cannot be reproduced without written permission. The content is not intended to be used for anything other than information purposes.
