The Effect of X-Ray and Accretion Variability on Mid-Infrared Lines in the Young Disk-Bearing Binary DQ Tau
Abstract
A star's radiation field is the main energy source of a planet-forming disk. Stellar photons---from X-rays to optical---are reprocessed in the inner protoplanetary disk enabling mid-IR diagnostics of the disk's physical conditions. Most pre-main-sequence stars accrete at moderate rates and emit X-rays efficiently. Such activity is expected to drive stochastic variability in the stellar spectrum. It is not clear to what extent such variability affects the thermochemical structure of protoplanetary disks. We aim to examine the effect of routine accretion variability and X-ray flares on the thermochemical structure and mid-IR line emission spectra of protoplanetary disks. We combine multiepoch, contemporaneous X-ray and NUV/optical observations of the DQ Tau binary with JWST/MIRI spectra of its circumbinary disk. We interpret the data and assess the effect of a varying stellar spectrum on the disk using a thermochemical model illustrative of the system. Synthetic fluxes of CO, CO2, HCN, and H2O are systematically stronger at periastron than at apastron due to an enhanced accretion luminosity. Variations in the integrated fluxes lie within a factor of two between epochs, in agreement with the JWST/MIRI spectra of DQ Tau. Routine stellar variability induces only modest changes in the disk's structure, yet it can still shift the snowline outwards by 17 percent relative to its apastron position. Because the JWST observations did not coincide with X-ray flares, our flare results rely on simulations: moderate-intensity flares leave most mid-IR molecular emission unchanged; in contrast, X-ray flares strongly enhance the abundances and mid-IR luminosities of H I, Ar II, and Ne II in the disk surface. Our results imply that the Spitzer/JWST line variability observed in non-outbursting systems is consistent with moderately variable stellar spectra driven by accretion and magnetospheric activity.
Related
- BlackHoleWeather – Spin-coupled chaotic cold accretion across the meso scale: Kinematics and variability
- Impact of accretion variability on the CO emission of a disk around a very low-mass star with JWST
- Accretion Geometry of the Ultracompact X-Ray Binary 4U 1543–624: AstroSat View
- Electromagnetic Counterparts of Stellar-mass Binary Black Hole Mergers in AGN Accretion Disks: Theoretical Models and Observational Status
- Disk Structure May Determine AGN Variability and Explain the Accretion Disk Size Problem: No Broad Line Region Required
BibTeX
@misc{portillarevelo2026effect,
title = {{The Effect of X-Ray and Accretion Variability on Mid-Infrared Lines in the Young Disk-Bearing Binary DQ Tau}},
author = {Bayron Portilla-Revelo and Konstantin V. Getman and Ágnes Kóspál and Dmitry Semenov and Vitaly Akimkin and Lis Zwicky and Jan Forbrich and Sierk van Terwisga},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.06863},
eprint = {2609.06863},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.06863},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The Effect of X-Ray and Accretion Variability on Mid-Infrared Lines in the Young Disk-Bearing Binary DQ Tau
AU - Bayron Portilla-Revelo
AU - Konstantin V. Getman
AU - Ágnes Kóspál
AU - Dmitry Semenov
AU - Vitaly Akimkin
AU - Lis Zwicky
AU - Jan Forbrich
AU - Sierk van Terwisga
PY - 2026
DA - 2026/09/06
PB - arXiv
DO - 10.48550/arxiv.2609.06863
UR - https://arxiv.org/abs/2609.06863
AB - A star's radiation field is the main energy source of a planet-forming disk. Stellar photons---from X-rays to optical---are reprocessed in the inner protoplanetary disk enabling mid-IR diagnostics of the disk's physical conditions. Most pre-main-sequence stars accrete at moderate rates and emit X-rays efficiently. Such activity is expected to drive stochastic variability in the stellar spectrum. It is not clear to what extent such variability affects the thermochemical structure of protoplanetary disks. We aim to examine the effect of routine accretion variability and X-ray flares on the thermochemical structure and mid-IR line emission spectra of protoplanetary disks. We combine multiepoch, contemporaneous X-ray and NUV/optical observations of the DQ Tau binary with JWST/MIRI spectra of its circumbinary disk. We interpret the data and assess the effect of a varying stellar spectrum on the disk using a thermochemical model illustrative of the system. Synthetic fluxes of CO, CO2, HCN, and H2O are systematically stronger at periastron than at apastron due to an enhanced accretion luminosity. Variations in the integrated fluxes lie within a factor of two between epochs, in agreement with the JWST/MIRI spectra of DQ Tau. Routine stellar variability induces only modest changes in the disk's structure, yet it can still shift the snowline outwards by 17 percent relative to its apastron position. Because the JWST observations did not coincide with X-ray flares, our flare results rely on simulations: moderate-intensity flares leave most mid-IR molecular emission unchanged; in contrast, X-ray flares strongly enhance the abundances and mid-IR luminosities of H I, Ar II, and Ne II in the disk surface. Our results imply that the Spitzer/JWST line variability observed in non-outbursting systems is consistent with moderately variable stellar spectra driven by accretion and magnetospheric activity.
ER -