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Long-term ultraviolet variability of Taurus T Tauri stars from the IUE archive

Year: 2026
Type: article
Abstract: Aims. Ultraviolet (UV) radiation from classical T Tauri stars is generated primarily by magnetospheric accretion and plays a fundamental role in the evolution of circumstellar disks. Despite its importance, the long-term variability of the UV radiation field remains poorly characterized because homogeneous time-series observations are scarce. We investigate the long-term variability of the near-UV continuum and the Mg II resonance doublet, and assess whether the two diagnostics trace the same underlying accretion variability. Methods. We analyzed the complete archive of long-wavelength International Ultraviolet Explorer (IUE) observations of T Tauri stars in the Taurus–Auriga star-forming region, which comprises 475 low-dispersion spectra of 36 objects accumulated during the 18-year operational lifetime of the mission. The variability of the UV continuum was characterized using three continuum windows between 2600 and 3100 Å. Continuum-subtracted Mg II line fluxes, UV– V colors, and Lomb–Scargle periodograms were used to investigate the relationship between continuum and line variability and to search for characteristic timescales. Results. The continuum fluxes measured within the 2675–3055 Å interval are strongly correlated, with variability occurring predominantly in the continuum level rather than in the spectral shape. The near-UV and quasi-simultaneous optical fluxes are significantly correlated in six of the seven best-sampled sources, although their relative variability differs among objects. The relation between Mg II and the near-UV continuum shows substantial object-to-object diversity, ranging from correlated variations with different fractional responses to largely decoupled or anticorrelated behavior. Thus, Mg II does not show a universal temporal response to continuum variability. Lomb–Scargle periodograms show formally significant features in some of the best-sampled objects, including features near 10 and 33 d. However, the irregular and clustered temporal sampling provides insufficient cycle coverage to establish these features as periodic or characteristic timescales.
DOI: 10.1051/0004-6361/202661978
Language: English
Open Access status: gold
Estimated APC paid: $1,865
OpenAlex ID: W7220902285
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