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Arxiv: MINDS. The DR Tau disk II: probing the hot and cold H_2O reservoirs in the JWST-MIRI spectrum Published: 7/6/2024 4:25:44 PM Updated: 7/6/2024 4:25:44 PM

Paper abstract: The MRS mode of the JWST-MIRI instrument gives insights into the chemicalrichness and complexity of the inner regions of planet-forming disks. Here, weanalyse the H_2O-rich spectrum of the compact disk DR Tau. We probe theexcitation conditions of the H_2O transitions observed in differentwavelength regions across the entire spectrum using LTE slab models, probingboth the rovibrational and rotational transitions. These regions suggest aradial temperature gradient, as the excitation temperature (emitting radius)decreases (increases) with increasing wavelength. To explain the derivedemitting radii, we require a larger inclination for the inner disk (i~20-23degrees) compared to the outer disk (i~5 degrees), agreeing with our previousanalysis on CO. We also analyse the pure rotational spectrum (<10 micron) usinga large, structured disk (CI Tau) as a template, confirming the presence of theradial gradient, and by fitting multiple components to further characterise theradial and vertical temperature gradients present in the spectrum. At leastthree temperature components (T~180-800 K) are required to reproduce therotational spectrum of H_2O arising from the inner ~0.3-8 au. Thesecomponents describe a radial temperature gradient that scales roughly as~R^{-0.5} in the emitting layers. As the H_2O is mainly optically thick, wederive a lower limit on the abundance ratio of H_2O/CO~0.17, suggesting apotential depletion of H_2O. Similarly to previous work, we detect a coldH_2O component (T~180 K) originating from near the snowline. We cannotconclude if an enhancement of the H_2O reservoir is observed following radialdrift. A consistent analysis of a larger sample of compact disks is necessaryto study the importance of drift in enhancing the H_2O abundances.