K2 reveals pulsed accretion driven by the 2 Myr old hot Jupiter CI Tau b

CI Tau is a young (~2 Myr) classical T Tauri star located in the Taurus star forming region. Radial velocity observations indicate it hosts a Jupiter-sized planet with an orbital period of approximately 9 days. In this work, we analyze time series of CI Tau's photometric variability as seen by K2. The lightcurve reveals the stellar rotation period to be ~6.6 d. Although there is no evidence that CI Tau b transits the host star, a ~9 d signature is also present in the lightcurve. We believe this is most likely caused by planet-disk interactions which perturb the accretion flow onto the star, resulting in a periodic modulation of the brightness with the ~9 d period of the planet's orbit.Comment: Accepted for publication in ApJ Letter

The Far-Ultraviolet Spectra of TW Hya. II. Models of H2 Fluorescence in a Disk

We measure the temperature of warm gas at planet-forming radii in the disk around the classical T Tauri star (CTTS) TW Hya by modelling the H2 fluorescence observed in HST/STIS and FUSE spectra. Strong Ly-alpha emission irradiates a warm disk surface within 2 AU of the central star and pumps certain excited levels of H2. We simulate a 1D plane-parallel atmosphere to estimate fluxes for the 140 observed H2 emission lines and to reconstruct the Ly-alpha emission profile incident upon the warm H2. The excitation of H2 can be determined from relative line strengths by measuring self-absorption in lines with low-energy lower levels, or by reconstructing the Ly-alpha profile incident upon the warm H2 using the total flux from a single upper level and the opacity in the pumping transition. Based on those diagnostics, we estimate that the warm disk surface has a column density of log N(H2)=18.5^{+1.2}_{-0.8}, a temperature T=2500^{+700}_{-500} K, and a filling factor of H2, as seen by the source of Ly-alpha emission, of 0.25\pm0.08 (all 2-sigma error bars). TW Hya produces approximately 10^{-3} L_\odot in the FUV, about 85% of which is in the Ly-alpha emission line. From the H I absorption observed in the Ly-alpha emission, we infer that dust extinction in our line of sight to TW Hya is negligible.Comment: Accepted by ApJ. 26 pages, 17 figures, 6 table

The FUV spectrum of TW Hya. I. Observations of H2_2 Fluorescence

We observed the classical T Tauri star TW Hya with \textit{HST}/STIS using the E140M grating, from 1150--1700 \AA, with the E230M grating, from 2200--2900 \AA, and with \FUSE from 900--1180 \AA. Emission in 143 Lyman-band H$_2$ lines representing 19 progressions dominates the spectral region from 1250--1650 \AA. The total H$_2$ emission line flux is $1.94 \times 10^{-12}$ erg cm$^{-2}$ s$^{-1}$, which corresponds to $1.90\times10^{-4}$ $L_\odot$ at TW Hya's distance of 56 pc. A broad stellar \Lya line photoexcites the H$_2$ from excited rovibrational levels of the ground electronic state to excited electronic states. The \ion{C}{2} 1335 \AA doublet, \ion{C}{3} 1175 \AA\ multiplet, and \ion{C}{4} 1550 \AA doublet also electronically excite H$_2$. The velocity shift of the H$_2$ lines is consistent with the photospheric radial velocity of TW Hya, and the emission is not spatially extended beyond the 0\farcs05 resolution of \textit{HST}. The H$_2$ lines have an intrinsic FWHM of $11.91\pm0.16$ \kms. One H$_2$ line is significantly weaker than predicted by this model because of \ion{C}{2} wind absorption. We also do not observe any H$_2$ absorption against the stellar \Lya profile. From these results, we conclude that the H$_2$ emission is more consistent with an origin in a disk rather than in an outflow or circumstellar shell. We also analyze the hot accretion-region lines (e.g., \ion{C}{4}, \ion{Si}{4}, \ion{O}{6}) of TW Hya, which are formed at the accretion shock, and discuss some reasons why Si lines appear significantly weaker than other TR region lines.Comment: accepted by ApJ, 42 pages -- 20 text, 11 figure

Star-Crossed Lovers DI Tau A and B: Orbit Characterization and Physical Properties Determination

The stellar companion to the weak-line T Tauri star DI Tau A was first discovered by the lunar occultation technique in 1989 and was subsequently confirmed by a speckle imaging observation in 1991. It has not been detected since, despite being targeted by five different studies that used a variety of methods and spanned more than 20 years. Here, we report the serendipitous rediscovery of DI Tau B during our Young Exoplanets Spectroscopic Survey (YESS). Using radial velocity data from YESS spanning 17 years, new adaptive optics observations from Keck II, and a variety of other data from the literature, we derive a preliminary orbital solution for the system that effectively explains the detection and (almost all of the) non-detection history of DI Tau B. We estimate the dynamical masses of both components, finding that the large mass difference (q $\sim$0.17) and long orbital period ($\gtrsim$35 years) make DI Tau system a noteworthy and valuable addition to studies of stellar evolution and pre-main-sequence models. With a long orbital period and a small flux ratio (f2/f1) between DI Tau A and B, additional measurements are needed for a better comparison between these observational results and pre-main-sequence models. Finally, we report an average surface magnetic field strength ($\bar B$) for DI Tau A, of $\sim$0.55 kG, which is unusually low in the context of young active stars.Comment: 21 pages, 10 figures. Accepted to Ap

Randomized Controlled Pilot Trial of Mindfulness-Based Stress Reduction for Breast and Colorectal Cancer Survivors: Effects on Cancer-Related Cognitive Impairment

Purpose Cancer-related cognitive impairment (CRCI) is a common, fatigue-related symptom that disrupts cancer survivors’ quality of life. Few interventions for CRCI exist. As part of a randomized pilot study targeting cancer-related fatigue, the effects of mindfulness-based stress reduction (MBSR) on survivors’ cognitive outcomes were investigated. Methods Breast and colorectal cancer survivors (n = 71) with moderate-to-severe fatigue were randomized to MBSR (n = 35) or a fatigue education and support (ES; n = 36) condition. The Attentional Function Index (AFI) and the Stroop test were used to assess survivors’ cognitive function at baseline (T1), after the 8-week intervention period (T2), and 6 months later (T3) using intent-to-treat analysis. Mediation analyses were performed to explore mechanisms of intervention effects on cognitive functioning. Results MBSR participants reported significantly greater improvement on the AFI total score compared to ES participants at T2 (d = 0.83, p = 0.001) and T3 (d = 0.55, p = 0.021). MBSR also significantly outperformed ES on most AFI subscales, although both groups improved over time. MBSR produced greater Stroop accuracy rates relative to ES at T2 (r = 0.340, p = 0.005) and T3 (r = 0.280, p = 0.030), with improved accuracy over time only for the MBSR group. There were no significant differences in Stroop reaction time between groups. Improvements in mindfulness mediated the effect of group (e.g., MBSR vs. ES) on AFI total score at T2 and T3. Conclusions Additional randomized trials with more comprehensive cognitive measures are warranted to definitively assess the efficacy of MBSR for CRCI. Implications for Cancer Survivors This pilot study has important implications for all cancer survivors as it is the first published trial to show that MBSR offers robust and durable improvements in CRCI

Towards two decades of Atlantic Ocean mass and heat transports at 26.5° N

Continuous measurements of the Atlantic meridional overturning circulation (AMOC) and meridional ocean heat transport at 26.5° N began in April 2004 and are currently available through December 2020. Approximately 90% of the total meridional heat transport (MHT) at 26.5° N is carried by the zonally averaged overturning circulation, and an even larger fraction of the heat transport variability (approx. 95%) is explained by the variability of the zonally averaged overturning. A physically based separation of the heat transport into large-scale AMOC, gyre and shallow wind-driven overturning components remains challenging and requires new investigations and approaches. We review the major interannual changes in the AMOC and MHT that have occurred over the nearly two decades of available observations and their documented impacts on North Atlantic heat content. Changes in the flow-weighted temperature of the Florida Current (Gulf Stream) over the past two decades are now taken into account in the estimates of MHT, and have led to an increased heat transport relative to the AMOC strength in recent years. Estimates of the MHT at 26.5° N from coupled models and various surface flux datasets still tend to show low biases relative to the observations, but indirect estimates based on residual methods (top of atmosphere net radiative flux minus atmospheric energy divergence) have shown recent promise in reproducing the heat transport and its interannual variability. This article is part of a discussion meeting issue ‘Atlantic overturning: new observations and challenges’

Multi-wavelength analysis of high energy electrons in solar flares: a case study of August 20, 2002 flare

A multi-wavelength spatial and temporal analysis of solar high energy electrons is conducted using the August 20, 2002 flare of an unusually flat (gamma=1.8) hard X-ray spectrum. The flare is studied using RHESSI, Halpha, radio, TRACE, and MDI observations with advanced methods and techniques never previously applied in the solar flare context. A new method to account for X-ray Compton backscattering in the photosphere (photospheric albedo) has been used to deduce the primary X-ray flare spectra. The mean electron flux distribution has been analysed using both forward fitting and model independent inversion methods of spectral analysis. We show that the contribution of the photospheric albedo to the photon spectrum modifies the calculated mean electron flux distribution, mainly at energies below 100 keV. The positions of the Halpha emission and hard X-ray sources with respect to the current-free extrapolation of the MDI photospheric magnetic field and the characteristics of the radio emission provide evidence of the closed geometry of the magnetic field structure and the flare process in low altitude magnetic loops. In agreement with the predictions of some solar flare models, the hard X-ray sources are located on the external edges of the Halpha emission and show chromospheric plasma heated by the non-thermal electrons. The fast changes of Halpha intensities are located not only inside the hard X-ray sources, as expected if they are the signatures of the chromospheric response to the electron bombardment, but also away from them.Comment: 26 pages, 9 figures, accepted to Solar Physic

Randomized Controlled Pilot Trial of Mindfulness-Based Stress Reduction Compared to Psychoeducational Support for Persistently Fatigued Breast and Colorectal Cancer Survivors

Purpose Cancer-related fatigue (CRF) is a disruptive symptom for many survivors. Despite promising evidence for efficacy of Mindfulness-Based Stress Reduction (MBSR) in reducing CRF, no trials comparing it to an active comparator for fatigued survivors have been published. The purpose of this trial was to compare MBSR to psychoeducation for CRF and associated symptoms. Methods Breast (n=60) and colorectal (n=11) cancer survivors (stage 0–III) with clinically significant CRF after completing chemotherapy and/or radiation therapy an average of 28 months prior to enrollment were randomized to MBSR or psychoeducation/support groups (PES). MBSR focused on mindfulness training; PES focused on CRF self-management. Outcomes included CRF interference (primary), CRF severity and global improvement, vitality, depression, anxiety, sleep disturbance, and pain. Outcomes were assessed at baseline (T1), post-intervention (T2), and 6-month follow-up (T3) using intent-to-treat analysis. Results Between-group differences in CRF interference were not significant at any time point; however, there was a trend favoring MBSR (d=−0.46, p=0.073) at T2. MBSR participants reported significantly greater improvement in vitality (d=0.53, p=0.003) and were more likely to report CRF as moderately-to-completely improved compared to the PES group (χ2 (1)=4.1765, p=0.041) at T2. MBSR participants also reported significantly greater reductions in pain at T2 (d=0.53, p=0.014). In addition, both MBSR and PES produced moderate-to-large and significant within-group improvements in all fatigue outcomes, depression, anxiety, and sleep at T2 and T3 compared to T1. Conclusion MBSR and PES appear efficacious for CRF and related symptoms. Larger trials including a usual care arm are warranted