Testing Pre-main-sequence Evolutionary Models with Gaia and SPHEREx Observations of Canis Major North
Abstract
Pre-main-sequence (PMS) evolutionary models can assign different ages across stellar mass within the same population. We use joint Gaia and SPHEREx spectral energy distributions to infer effective temperatures, radii, and luminosities for members of Canis Major North (CMaN), a nearby association with independent lithium and kinematic age constraints near 23 Myr. The SPHEREx fluxes agree with 2MASS and WISE photometry to 3--6\%, and we anchor the absolute flux scale to Gaia, 2MASS, and WISE. Using the revised temperatures, we obtain a lithium age of 22.4+2.8−1.5 Myr. For a 29-star PMS sample, population-wide HR-diagram fits yield 20.5+1.5−1.4 Myr for unspotted SPOTS models, consistent with the external constraints, 18.4+1.4−1.3 and 18.7+1.3−1.2 Myr for the Feiden nonmagnetic and BHAC15 models, and substantially older ages of 32.2+2.3−2.1 and 55+5−5 Myr for the Feiden magnetic and PARSEC models. No grid returns a temperature-independent age. The Feiden, SPOTS, and BHAC15 models assign older ages to stars above $4000$ K, whereas PARSEC assigns increasingly older ages toward lower temperatures. The intrinsic luminosity dispersion is also mass dependent, approximately $0.14$ dex below $3450$ K but $0.05$ dex at intermediate temperatures. At a fixed age of 23.0 Myr, a single SPOTS filling factor cannot reproduce the width of the low-temperature sequence, whereas the empirical filling-factor distribution of young stars overpredicts it. Spotted isochrones can enclose every cool member only at ages of 37--50 Myr, inconsistent with the lithium and kinematic ages.
Related
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BibTeX
@misc{paolino2026testing,
title = {{Testing Pre-main-sequence Evolutionary Models with Gaia and SPHEREx Observations of Canis Major North}},
author = {Facundo Perez Paolino and Ronan Kerr and Jonathan Gagne},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.36223},
eprint = {2610.36223},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.36223},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Testing Pre-main-sequence Evolutionary Models with Gaia and SPHEREx Observations of Canis Major North
AU - Facundo Perez Paolino
AU - Ronan Kerr
AU - Jonathan Gagne
PY - 2026
DA - 2026/10/26
PB - arXiv
DO - 10.48550/arxiv.2610.36223
UR - https://arxiv.org/abs/2610.36223
AB - Pre-main-sequence (PMS) evolutionary models can assign different ages across stellar mass within the same population. We use joint Gaia and SPHEREx spectral energy distributions to infer effective temperatures, radii, and luminosities for members of Canis Major North (CMaN), a nearby association with independent lithium and kinematic age constraints near 23 Myr. The SPHEREx fluxes agree with 2MASS and WISE photometry to 3--6\%, and we anchor the absolute flux scale to Gaia, 2MASS, and WISE. Using the revised temperatures, we obtain a lithium age of 22.4^+2.8_−1.5 Myr. For a 29-star PMS sample, population-wide HR-diagram fits yield 20.5^+1.5_−1.4 Myr for unspotted SPOTS models, consistent with the external constraints, 18.4^+1.4_−1.3 and 18.7^+1.3_−1.2 Myr for the Feiden nonmagnetic and BHAC15 models, and substantially older ages of 32.2^+2.3_−2.1 and 55^+5_−5 Myr for the Feiden magnetic and PARSEC models. No grid returns a temperature-independent age. The Feiden, SPOTS, and BHAC15 models assign older ages to stars above $4000$ K, whereas PARSEC assigns increasingly older ages toward lower temperatures. The intrinsic luminosity dispersion is also mass dependent, approximately $0.14$ dex below $3450$ K but $0.05$ dex at intermediate temperatures. At a fixed age of 23.0 Myr, a single SPOTS filling factor cannot reproduce the width of the low-temperature sequence, whereas the empirical filling-factor distribution of young stars overpredicts it. Spotted isochrones can enclose every cool member only at ages of 37--50 Myr, inconsistent with the lithium and kinematic ages.
ER -