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Peer-reviewedCC BY 4.0The Astrophysical Journal

Evolution of Stellar Activity and Habitable Zone. IV. Calcium II Infrared Triplet Activity from Open Clusters and White Dwarf Binaries

  • Shidi Zhang1
  • Song Wang2,3
  • Henggeng Han2
  • Wenyuan Cui1
  1. 1Hebei Normal University
  2. 2Chinese Academy of Sciences
  3. 3Beijing Normal University
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Abstract

Recent high-resolution spectroscopic observations from the Gaia mission provide a great opportunity to study calcium II infrared triplet (Ca ii IRT) activity. In this study, we present the first investigation of Ca ii IRT activity evolution using Gaia observations, together with age estimates derived from open clusters and white dwarf–main-sequence (WD-MS) binaries. We find that R IRT ′ serves as a reliable age proxy, declining with age in a manner consistent with other activity indicators. Notably, R IRT ′ exhibits a steeper decline and a larger decay amplitude for lower-mass stars. Furthermore, unlike the steady decay observed for F and G stars, late K and early M stars display a period of constant saturated activity before 100 Myr (consistent with the pre-main-sequence stage), after which R IRT ′ drops rapidly by about 1 dex between 100 Myr and 1 Gyr. However, due to the limited sample size and the scatter in the activity of WD-MS binaries, it remains unclear whether the activity continues to decline or flattens to a constant level at old ages (≳2 Gyr). More Ca ii IRT observations from the upcoming Gaia DR4, together with more accurate age estimates from various methods, will be key to revealing the true behavior of the activity–age relation at late stages.

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Cite

BibTeXRIS
BibTeX
@article{zhang2026evolution,
  title = {{Evolution of Stellar Activity and Habitable Zone. IV. Calcium II Infrared Triplet Activity from Open Clusters and White Dwarf Binaries}},
  author = {Shidi Zhang and Song Wang and Henggeng Han and Wenyuan Cui},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = nov,
  doi = {10.3847/1538-4357/aea974},
  url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea974},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - Evolution of Stellar Activity and Habitable Zone. IV. Calcium II Infrared Triplet Activity from Open Clusters and White Dwarf Binaries
AU  - Shidi Zhang
AU  - Song Wang
AU  - Henggeng Han
AU  - Wenyuan Cui
PY  - 2026
DA  - 2026/11/02
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/aea974
UR  - https://iopscience.iop.org/article/10.3847/1538-4357/aea974
AB  - Recent high-resolution spectroscopic observations from the Gaia mission provide a great opportunity to study calcium II infrared triplet (Ca ii IRT) activity. In this study, we present the first investigation of Ca ii IRT activity evolution using Gaia observations, together with age estimates derived from open clusters and white dwarf–main-sequence (WD-MS) binaries. We find that R IRT ′ serves as a reliable age proxy, declining with age in a manner consistent with other activity indicators. Notably, R IRT ′ exhibits a steeper decline and a larger decay amplitude for lower-mass stars. Furthermore, unlike the steady decay observed for F and G stars, late K and early M stars display a period of constant saturated activity before 100 Myr (consistent with the pre-main-sequence stage), after which R IRT ′ drops rapidly by about 1 dex between 100 Myr and 1 Gyr. However, due to the limited sample size and the scatter in the activity of WD-MS binaries, it remains unclear whether the activity continues to decline or flattens to a constant level at old ages (≳2 Gyr). More Ca ii IRT observations from the upcoming Gaia DR4, together with more accurate age estimates from various methods, will be key to revealing the true behavior of the activity–age relation at late stages.
SN  - 1538-4357
SN  - 0004-637X
ER  -