Disk Cooling and Wind Lines As Seen In the Spectral Line Evolution of V960 Mon

TL;DR

This study analyzes the spectral line evolution of V960 Mon post-outburst, revealing decreasing disk temperature, complex wind/outflow features, and partial model agreement, advancing understanding of FU Ori objects' accretion and outflow dynamics.

Contribution

It provides high-resolution spectroscopic observations of V960 Mon, identifying wind components and discrepancies with accretion disk models, highlighting complex outflow structures.

Findings

Spectral evolution indicates decreasing disk temperature.

Presence of broad, blueshifted wind profiles.

Partial match with accretion disk models.

Abstract

We follow up our photometric study of the post-outburst evolution of the FU Ori object V960 Mon with a complementary spectroscopic study at high dispersion that uses time series spectra from Keck/HIRES. Consistent with the photometric results reported in Carvalho et al. 2023, we find that the spectral evolution of V960 Mon corresponds to a decrease in the temperature of the inner disk, driven by a combination of decreasing accretion rate and increasing inner disk radius. We also find that although the majority of the absorption lines are well-matched by our accretion disk model spectrum, there are several strong absorption line families and a few emission lines that are not captured by the model. By subtracting the accretion disk model from the data at each epoch, we isolate the wind/outflow components of the system. The residuals show both broad and highly blueshifted profiles, as well as narrow and only slightly blueshifted profiles, with some lines displaying both types of features.