Using Multiwavelength Variability to Explore the Connection between X-ray Emission, the Far-Ultraviolet H2 Bump, and Accretion in T Tauri Stars

Abstract

The high-energy radiation fields of T Tauri stars (TTS) should affect the surrounding circumstellar disk, having implications for disk transport and heating. Yet, observational evidence of the effect of high-energy fields on disks is scarce. Here we investigate the connection between X-ray emission and the innermost gas disk by leveraging the variability of TTS. We obtained multiple epochs of coordinated data (taken either simultaneously or within a few hours) of accreting TTS with the Hubble Space Telescope, the Neil Gehrels Swift Observatory, and the Chandra X-ray Observatory. We measured the far-ultraviolet (FUV) H2 bump feature at 1600 A, which traces gas <1 AU from the star; the near-ultraviolet (NUV) emission, from which we extract the accretion luminosity; and also the X-ray luminosity. We do not find a correlation between the FUV H2 bump and X-ray luminosity. Therefore, an observable tracer of the effect of X-ray ionization in the innermost disk remains elusive. We report a correlation between the FUV H2 bump and accretion luminosity, linking this feature to the disk surface density. We also see a correlation between the X-ray luminosity and the accretion column density, implying that flaring activity may influence accretion. These results stress the importance of coordinated multiwavelength work to understand TTS.

accepted to ApJ

References in corpus (23)

• The Gaia mission
• UV excess measures of accretion onto young very low-mass stars and brown dwarfs
• On the gas content of transitional disks: a VLT/X-Shooter study of accretion and winds
• Mapping accretion and its variability in the young open cluster NGC 2264: a study based on u-band photometry
• c2d Spitzer IRS Spectra of Disks around T Tauri Stars. III. [Ne II], [Fe I], and H_2 gas-phase lines
• Probing the Dust and Gas in the Transitional Disk of CS Cha with Spitzer
• Neon Fine-Structure Line Emission By X-ray Irradiated Protoplanetary Disks
• The Origins of Fluorescent H2 Emission From T Tauri~Stars
• X-ray emission from MP Muscae: an old classical T Tauri star
• X-rays from T Tau: A test case for accreting T Tauri stars
• The X-ray soft excess in classical T Tauri stars
• The first high-resolution X-ray spectrum of a Herbig Star: The case of AB Aurigae
• X-ray accretion signatures in the close CTTS binary V4046 Sgr
• High Resolution X-ray Spectroscopy of T Tauri Stars in the Taurus-Auriga Complex
• X-ray Flares in Orion Low Mass Stars
• Evidence for Accretion in the High-resolution X-ray Spectrum of the T Tauri Star System Hen 3-600
• Atomic Diagnostics of X-ray Irradiated Protoplanetary Disks
• Variable H${}^{13}$CO${}^{+}$ Emission in the IM Lup Disk: X-ray Driven Time-Dependent Chemistry?
• The nature of the soft X-ray source in DG Tau
• Multi-epoch Ultraviolet HST Observations of Accreting Low-mass Stars
• Using FUV to IR Variability to Probe the Star-Disk Connection in the Transitional Disk of GM Aur
• Redshifted X-rays from the material accreting onto TW Hya: evidence of a low-latitude accretion spot
• The 1600 Angstrom Emission Bump in Protoplanetary Disks: A Spectral Signature of H${}_2$O Dissociation

Cited by in corpus (1)

• Revealing the Star-Disk-Jet Connection in GM Aur using Multiwavelength Variability