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Accurate age and mass determinations for young pre-main sequence stars are made challenging by the presence of large-scale starspots. We present results from a near-infrared spectroscopic survey of ten T-Tauri Stars in Taurus-Auriga that characterize spot filling factors and temperatures, the resulting effects on temperature and luminosity determinations, and the consequences for inferred stellar masses and ages. We constructed composite models of spotted stars by combining BTSettl-CIFIST synthetic spectra of atmospheres to represent the spots and the photosphere along with continuum emission from a warm inner disk. Using a Markov-Chain Monte-Carlo algorithm, we find the best-fit spot and photospheric temperatures, spot filling factors, as well as disk filling factors. This methodology allowed us to reproduce the 0.75-2.40 micron stellar spectra and molecular feature strengths for all of our targets, disentangling the complicated multi-component emission. For a subset of stars with multi-epoch observations spanning an entire stellar rotation, we correlate the spectral variability and changes in the filling factors with rotational periods observed in K2 and AAVSO photometry. Combining spot-corrected effective temperatures and Gaia distances, we calculate luminosities and use the Stellar Parameters of Tracks with Starspots (SPOTS) models to infer spot-corrected masses and ages for our sample of stars. Our method of accounting for spots results in an average increase of 60% in mass and a doubling in age with respect to traditional methods using optical spectra that do not account for the effect of spots., Comment: Accepted for publication in ApJ. Preprint

We describe the results of a new reverberation mapping program focused on the nearby Seyfert galaxy NGC 3227. Photometric and spectroscopic monitoring were carried out from 2022 December to 2023 June with the Las Cumbres Observatory network of telescopes. We detected time delays in several optical broad emission lines, with H$\beta$ having the longest delay at $\tau_{\rm cent}=4.0^{+0.9}_{-0.9}$ days and He II having the shortest delay with $\tau_{\rm cent}=0.9^{+1.1}_{-0.8}$ days. We also detect velocity-resolved behavior of the H$\beta$ emission line, with different line-of-sight velocities corresponding to different observed time delays. Combining the integrated H$\beta$ time delay with the width of the variable component of the emission line and a standard scale factor suggests a black hole mass of $M_{\rm BH}=1.1^{+0.2}_{-0.3} \times 10^7 M_{\odot}$. Modeling of the full velocity-resolved response of the H$\beta$ emission line with the phenomenological code CARAMEL finds a similar mass of $M_{\rm BH}=1.2^{+1.5}_{-0.7} \times 10^7 M_{\odot}$, and suggests that the H$\beta$-emitting broad line region (BLR) may be represented by a biconical or flared disk structure that we are viewing at an inclination angle of $\theta_i \approx 33^{\circ}$ and with gas motions that are dominated by rotation. The new photoionization-based BLR modeling tool BELMAC finds general agreement with the observations when assuming the best-fit CARAMEL results, however BELMAC prefers a thick disk geometry and kinematics that are equally comprised of rotation and inflow. Both codes infer a radially extended and flattened BLR that is not outflowing., Comment: 16 pages, 9 figures, 4 tables; submitted to ApJ

Understanding the interplay of stellar feedback and turbulence in the interstellar medium (ISM) is essential to modeling the evolution of galaxies. To determine the timescales over which stellar feedback drives turbulence in the ISM, we performed a spatially resolved, multi-wavelength study of the nearby star-forming dwarf galaxy UGC 4305 (aka Holmberg II). As indicators of turbulence on local scales (400 pc), we utilized ionized gas velocity dispersion derived from IFU H$\alpha$ observations and atomic gas velocity dispersion and energy surface densities derived from HI synthesis observations with the Very Large Array. These indicators of turbulence were tested against star formation histories over the past 560 Myr derived from Color-Magnitude Diagrams (CMD) using Spearman's rank correlation coefficient. The strongest correlation identified at the 400 pc scale is between measures of HI turbulence and star formation 70-140 Myr ago. We repeated our analysis of UGC 4305's current turbulence and past star formation activity on multiple physical scales ($\sim$560, and 800 pc) to determine if there are indications of changes in the correlation timescale with changes to the physical scale. No notable correlations were found at larger physical scales emphasizing the importance of analyzing star formation driven turbulence as a local phenomenon., Comment: 17 pages, 9 figure, accepted to AJ