Stellar Activity in a Postmerger Giant Star
6 affiliations
- 1MIT Kavli Institute for Astrophysics and Space Research
- 2University of California San Diego
- 3University of California
- 4University of Rochester
- 5University of Florida
- 6Christian-Albrechts-Universität zu Kiel
Abstract
Binary stars are the progenitors of exotic objects, such as supernovae and gravitational-wave sources. However, some systems merge earlier, when the primary expands into a giant star at the end of its lifetime on the main sequence and causes its companion to spiral in. TYC 4144-329-2 is a candidate postmerger first-ascent giant star with a circumstellar disk seen in the infrared (IR). We detect weak X-ray and far-ultraviolet (FUV) emission from TYC 4144-329-2, which we interpret as a signature of weak coronal activity. We also find variability in H α line profiles and in the optical light curves, and we suggest an intermediate geometry where the line of sight passes through the upper layers of a flared disk with a time-variable column density. While the X-rays must be coronal, the H α line profiles point to ongoing and variable accretion. We suggest that TYC 4144-329-2’s merger was more recent than those of other stars in this class and that it did not yet have time to develop a deep convection zone. If this scenario holds, TYC 4144-329-2 would be a unique probe of the earliest stages in the evolution of postmerger systems.
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BibTeX
@article{gunther2026stellar,
title = {{Stellar Activity in a Postmerger Giant Star}},
author = {H. M. Günther and C. Melis and K. J. Shen and Eric G. Blackman and K. Hoadley and P. C. Schneider},
journal = {The Astrophysical Journal},
year = {2026},
month = oct,
doi = {10.3847/1538-4357/aea619},
url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea619},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Stellar Activity in a Postmerger Giant Star
AU - H. M. Günther
AU - C. Melis
AU - K. J. Shen
AU - Eric G. Blackman
AU - K. Hoadley
AU - P. C. Schneider
PY - 2026
DA - 2026/10/07
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/aea619
UR - https://iopscience.iop.org/article/10.3847/1538-4357/aea619
AB - Binary stars are the progenitors of exotic objects, such as supernovae and gravitational-wave sources. However, some systems merge earlier, when the primary expands into a giant star at the end of its lifetime on the main sequence and causes its companion to spiral in. TYC 4144-329-2 is a candidate postmerger first-ascent giant star with a circumstellar disk seen in the infrared (IR). We detect weak X-ray and far-ultraviolet (FUV) emission from TYC 4144-329-2, which we interpret as a signature of weak coronal activity. We also find variability in H α line profiles and in the optical light curves, and we suggest an intermediate geometry where the line of sight passes through the upper layers of a flared disk with a time-variable column density. While the X-rays must be coronal, the H α line profiles point to ongoing and variable accretion. We suggest that TYC 4144-329-2’s merger was more recent than those of other stars in this class and that it did not yet have time to develop a deep convection zone. If this scenario holds, TYC 4144-329-2 would be a unique probe of the earliest stages in the evolution of postmerger systems.
SN - 0004-637X
SN - 1538-4357
ER -