[Paper Review] What are the temperatures of T Tauri stars? - Constraints from coeval formation of young eclipsing binaries

M. Ammler, V. Joergens+1 more|ArXiv.org|Jun 30, 2005

Astrophysics and Star Formation Studies51 references4 citations

TL;DR

This paper proposes a two-step method to constrain effective temperatures of pre-main sequence T Tauri stars using coeval formation in young eclipsing binary systems. By first selecting evolutionary models that simultaneously match observed masses and radii (ensuring coevality), then deriving temperatures from these models, the authors find V1174 Ori A has dwarf-like temperatures at ~9 Myr, while no firm conclusions can be drawn for RX J0529.4+0041 A and V1174 Ori B due to model inconsistencies across mass, radius, and temperature.

ABSTRACT

We show how the assumption of coeval formation can be used to constrain the effective temperatures of the components of young eclipsing double-lined spectroscopic binaries. Our method extends the approach of White et al. (1999) to a two-step analysis. The first step compares evolutionary models to the observed masses and radii and selects those models that predict ages that are consistent with coeval formation. The second step then uses these models to constrain the effective temperatures. We applied the method on literature values of the stellar parameters of the eclipsing binaries RX J0529.4+0041 A and V1174 Ori and confirm that V1174 Ori A has dwarf-like temperatures at an age of 9 Myrs, while we cannot draw any conclusions for RX J0529.4+0041 A and V1174 Ori B. Considering these binaries, we find that none of the evolutionary models gives coeval solutions simultaneously in mass, radius and effective temperature.

Motivation & Objective

• To address the uncertainty in effective temperature measurements of T Tauri stars due to distance, activity, and accretion disk contamination.
• To overcome reliance on luminosity class assumptions in temperature calibrations by using coeval formation as a physical constraint.
• To develop a method that independently determines temperatures of pre-main sequence stars using only mass, radius, and coevality constraints.
• To test the consistency of evolutionary models in simultaneously reproducing observed masses, radii, and effective temperatures for young binaries.
• To provide model-independent temperature constraints for T Tauri stars using eclipsing binary systems

Proposed method

• Apply a two-step method: first, compare observed masses and radii of binary components to evolutionary models (D’Antona & Mazzitelli, BCAH98, PS99, Siess et al., Yi et al.) to identify models that predict coeval formation.
• Select only models that yield consistent ages for both components, thereby ensuring coevality and filtering out inconsistent evolutionary tracks.
• Use the selected coeval models to derive effective temperatures for the primary stars, applying temperature scales from dwarf, giant, and intermediate luminosity classes.
• Calculate secondary temperatures from the observed temperature ratio derived from light curve analyses (Covino et al. 2004; Stassun et al. 2004).
• Compare the derived temperatures to the selected models to assess consistency and identify model deficiencies.
• Use multiple temperature calibration scales (e.g., Bessell, Luhman, Kenyon & Hartmann) to test robustness of results across different empirical and theoretical references.

Experimental results

Research questions

• RQ1 Can coeval formation of binary components be used to constrain the effective temperatures of T Tauri stars independently of luminosity class assumptions?
• RQ2 Do existing pre-main sequence evolutionary models simultaneously reproduce observed masses, radii, and effective temperatures for young eclipsing binaries?
• RQ3 What are the effective temperatures of the components of RX J0529.4+0041 and V1174 Ori, given coeval formation and mass-radius constraints?
• RQ4 Is the assumption of dwarf-like temperature scales valid for pre-main sequence stars in young binary systems?
• RQ5 How do different temperature calibration scales (dwarf, giant, intermediate) affect the derived temperatures when applied to coeval models?

Key findings

• V1174 Ori A has effective temperatures consistent with dwarf stars at an age of approximately 9 Myr, based on coeval models that match its observed mass and radius.
• For RX J0529.4+0041 A and V1174 Ori B, no consistent coeval solution was found across mass, radius, and temperature, preventing firm temperature constraints.
• No single evolutionary model simultaneously reproduces the observed masses, radii, and effective temperatures for the binary components, indicating model deficiencies.
• The method successfully identifies models that satisfy coevality and mass-radius consistency, providing a robust framework for temperature estimation.
• The use of multiple temperature calibration scales (dwarf, giant, intermediate) shows that temperature estimates are sensitive to the assumed luminosity class, highlighting the need for model-independent constraints.
• The results suggest that current evolutionary models may not fully capture the physical properties of pre-main sequence stars in young binary systems.