Correlating Changes in Spot Filling Factors with Stellar Rotation: The Case of LkCa 4

We present a multi-epoch spectroscopic study of LkCa 4, a heavily spotted non-accreting T Tauri star. Using SpeX at NASA's Infrared Telescope Facility (IRTF), 12 spectra were collected over five consecutive nights, spanning $\approx$ 1.5 stellar rotations. Using the IRTF SpeX Spectral Library, we constructed empirical composite models of spotted stars by combining a warmer (photosphere) standard star spectrum with a cooler (spot) standard weighted by the spot filling factor, $f_{spot}$. The best-fit models spanned two photospheric component temperatures, $T_{phot}$ = 4100 K (K7V) and 4400 K (K5V), and one spot component temperature, $T_{spot}$ = 3060 K (M5V) with an $A_V$ of 0.3. We find values of $f_{spot}$ to vary between 0.77 and 0.94 with an average uncertainty of $\sim$0.04. The variability of $f_{spot}$ is periodic and correlates with its 3.374 day rotational period. Using a mean value for $f^{mean}_{spot}$ to represent the total spot coverage, we calculated spot corrected values for $T_{eff}$ and $L_\star$. Placing these values alongside evolutionary models developed for heavily spotted young stars, we infer mass and age ranges of 0.45-0.6 $M_\odot$ and 0.50-1.25 Myr, respectively. These inferred values represent a twofold increase in the mass and a twofold decrease in the age as compared to standard evolutionary models. Such a result highlights the need for constraining the contributions of cool and warm regions of young stellar atmospheres when estimating $T_{eff}$ and $L_\star$ to infer masses and ages as well as the necessity for models to account for the effects of these regions on the early evolution of low-mass stars.Comment: 21 pages, 9 Figures; Accepted for publication in Ap

Bone cancer pain: The effects of the bisphosphonate alendronate on pain, skeletal remodeling, tumor growth and tumor necrosis

Patients with metastatic breast, lung or prostate cancer frequently have significant bone cancer pain. In the present report we address, in a single in vivo mouse model, the effects the bisphosphonate alendronate has on bone cancer pain, bone remodeling and tumor growth and necrosis. Following injection and confinement of green fluorescent protein-transfected murine osteolytic tumor cells into the marrow space of the femur of male C3H/HeJ mice, alendronate was administered chronically from the time the tumor was established until the bone cancer pain became severe. Alendronate therapy reduced ongoing and movement-evoked bone cancer pain, bone destruction and the destruction of sensory nerve fibers that innervate the bone. Whereas, alendronate treatment did not change viable tumor burden, both tumor growth and tumor necrosis increased. These data emphasize that it is essential to utilize a model where pain, skeletal remodeling and tumor growth can be simultaneously assessed, as each of these can significantly impact patient quality of life and survival.Peer reviewe