Starspots on weak-lined T Tauri stars in the σ Orionis cluster
- 1University of Exeter Department of Physics and Astronomy, , Stocker Road, Exeter EX4 4QL ,
- 2Astrophysics Group, Keele University , Keele ST5 5BG ,
Abstract
The light curves and spectra of T Tauri stars indicate the presence of cool starspots covering large areas of their photospheres. Heavily spotted stars should have a larger mid-infrared flux than the equivalent single-temperature photospheres. To test this prediction we first fit single and two-temperature models to optical spectra of young stars in the 4 Myr-old σ Orionis cluster and a control set of older field stars. The fits to the young stars favour two temperatures while the field stars show no preference. Independent tests of our models for nine probable single K-type weak-lined T Tauri stars using infrared photometry confirms the presence of large cool components. We consider and rule out as explanations of the two temperature photospheres: binary stars for all but one WTTS; accretion, as the observed Hα equivalent width is too small; gravity darkening as the predicted temperature differences are too small. This leaves cool areas akin to starspots covering 30-95 per cent of the surface as the plausible explanation.Our results show no significant difference in the cool temperature for surface fractions between 0.30–0.75, implying a common mechanism is responsible. These cool surface fractions would lead to significant overestimates in age and mass when fitting unspotted isochrones in colour-magnitude diagrams. The dispersion in cool surface fraction could also explain the dispersion in lithium equivalent width seen in the spectra of coeval zero-age main sequence stars.
Versions
Related
- Starspots on weak-lined T Tauri stars in the sigma Orionis cluster
- Long-term ultraviolet variability of Taurus T Tauri stars from the IUE archive
- 3D simulations of magnetospheric accretion in T Tauri stars I. Disk truncation, stellar torques, and application to observations
- Long-term ultraviolet variability of Taurus T Tauri stars from the IUE archive
- 3D simulations of magnetospheric accretion in T Tauri stars: I. Disk truncation, stellar torques, and application to observations
BibTeX
@article{wilson2026starspots,
title = {{Starspots on weak-lined T Tauri stars in the σ Orionis cluster}},
author = {Andrew J Wilson and Darryl J Sergison and Tim Naylor and Robin D Jeffries},
journal = {Monthly Notices of the Royal Astronomical Society},
year = {2026},
month = oct,
doi = {10.1093/mnras/stag1909},
url = {https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag1909/8885812},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Starspots on weak-lined T Tauri stars in the σ Orionis cluster
AU - Andrew J Wilson
AU - Darryl J Sergison
AU - Tim Naylor
AU - Robin D Jeffries
PY - 2026
DA - 2026/10/08
JO - Monthly Notices of the Royal Astronomical Society
DO - 10.1093/mnras/stag1909
UR - https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag1909/8885812
AB - The light curves and spectra of T Tauri stars indicate the presence of cool starspots covering large areas of their photospheres. Heavily spotted stars should have a larger mid-infrared flux than the equivalent single-temperature photospheres. To test this prediction we first fit single and two-temperature models to optical spectra of young stars in the 4 Myr-old σ Orionis cluster and a control set of older field stars. The fits to the young stars favour two temperatures while the field stars show no preference. Independent tests of our models for nine probable single K-type weak-lined T Tauri stars using infrared photometry confirms the presence of large cool components. We consider and rule out as explanations of the two temperature photospheres: binary stars for all but one WTTS; accretion, as the observed Hα equivalent width is too small; gravity darkening as the predicted temperature differences are too small. This leaves cool areas akin to starspots covering 30-95 per cent of the surface as the plausible explanation.Our results show no significant difference in the cool temperature for surface fractions between 0.30–0.75, implying a common mechanism is responsible. These cool surface fractions would lead to significant overestimates in age and mass when fitting unspotted isochrones in colour-magnitude diagrams. The dispersion in cool surface fraction could also explain the dispersion in lithium equivalent width seen in the spectra of coeval zero-age main sequence stars.
SN - 0035-8711
SN - 1365-2966
ER -