Evidence for J and H-band excess in classical T Tauri stars and the implications for disk structure and estimated ages

We argue that classical T Tauri stars (cTTs) possess significant non- photospheric excess in the J and H bands. We first show that normalizing the spectral energy distributions (SEDs) of cTTs to the J-band leads to a poor fit of the optical fluxes, while normalizing the SEDs to the Ic-band produces a better fit to the optical bands and in many cases reveals the presence of a considerable excess at J and H. NIR spectroscopic veiling measurements from the literature support this result. We find that J and H-band excesses correlate well with the K-band excess, and that the J-K and H-K colors of the excess emission are consistent with that of a black body at the dust sublimation temperature (~ 1500-2000 K). We propose that this near-IR excess originates at a hot inner rim, analogous to those suggested to explain the near-IR bump in the SEDs of Herbig Ae/Be stars. To test our hypothesis, we use the model presented by Dullemond et al. (2001) to fit the photometry data between 0.5 um and 24 um of 10 cTTs associated with the Chamaeleon II molecular cloud. The models that best fit the data are those where the inner radius of the disk is larger than expected for a rim in thermal equilibrium with the photospheric radiation field alone. In particular, we find that large inner rims are necessary to account for the mid infrared fluxes (3.6-8.0 um) obtained by the Spitzer Space Telescope. Finally, we argue that deriving the stellar luminosities of cTTs by making bolometric corrections to the J-band fluxes systematically overestimates these luminosities. The overestimated luminosities translate into underestimated ages when the stars are placed in the H-R diagram. Thus, the results presented herein have important implications for the dissipation timescale of inner accretion disks.Comment: 45 pages, 13 figure

Detection and Quantification of Gas-Phase Oxidized Mercury Compounds by GC/MS

Most mercury pollution is emitted to the atmosphere, and the location and bioavailability of deposited mercury largely depends on poorly understood atmospheric chemical reactions that convert elemental mercury into oxidized mercury compounds. Current measurement methods do not speciate oxidized mercury, leading to uncertainty about which mercury compounds exist in the atmosphere and how oxidized mercury is formed. We have developed a gas chromatography/mass spectrometry (GC-MS)-based system for identification and quantification of atmospheric oxidized mercury compounds. The system consists of an ambient air collection device, a thermal desorption module, a cryofocusing system, a gas chromatograph, and an ultra-sensitive mass spectrometer. It was able to separate and identify mercury halides with detection limits low enough for ambient air collection (90 pg), but an improved ambient air collection device is needed. The GC/MS system was unable to quantify HgO or Hg(NO3)2, and data collected cast doubt upon the existence of HgO in the gas phase

H2 Mid-IR Pure Rotational Emission from Young Stars: The TEXES/IRTF Survey

We describe the TEXES survey for mid-IR H2 pure rotational emission from young stars and report early successes. H2 emission is a potential tracer of warm gas in circumstellar disks. Three pure rotational lines are available from the ground: the J=3=>1, J=4=>2, and J=6=>4, transitions at 17.035 microns, 12.279 microns, and 8.025 microns, respectively. Using TEXES at the NASA IRTF 3m, we are midway through a survey of roughly 30 pre-main-sequence stars. To date, detected lines are all resolved, generally with FWHM<10 km/s. Preliminary analysis suggests the gas temperatures are between 400 and 800 K. From the work so far, we conclude that high spectral and spatial resolution are critical to the investigation of H2 in disks.Comment: 6 pages, to appear in Proceedings of the ESO Workshop on "High Resolution Infrared Spectroscopy in Astronomy" held in Garching, Germany, 18-21 November 200

Wolf 1130: A Nearby Triple System Containing a Cool, Ultramassive White Dwarf

Following the discovery of the T8 subdwarf WISEJ200520.38+542433.9 (Wolf 1130C), with common proper motion to a binary (Wolf 1130AB) consisting of an M subdwarf and a white dwarf, we set out to learn more about the old binary in the system. We find that the A and B components of Wolf 1130 are tidally locked, which is revealed by the coherence of more than a year of V band photometry phase folded to the derived orbital period of 0.4967 days. Forty new high-resolution, near-infrared spectra obtained with the Immersion Grating Infrared Spectrometer (IGRINS) provide radial velocities and a projected rotational velocity (v sin i) of 14.7 +/- 0.7 km/s for the M subdwarf. In tandem with a Gaia parallax-derived radius and verified tidal-locking, we calculate an inclination of i=29 +/- 2 degrees. From the single-lined orbital solution and the inclination we derive an absolute mass for the unseen primary (1.24+0.19-0.15 Msun). Its non-detection between 0.2 and 2.5 microns implies that it is an old (>3.7 Gyr) and cool (Teff<7000K) ONe white dwarf. This is the first ultramassive white dwarf within 25pc. The evolution of Wolf 1130AB into a cataclysmic variable is inevitable, making it a potential Type Ia supernova progenitor. The formation of a triple system with a primary mass >100 times the tertiary mass and the survival of the system through the common-envelope phase, where ~80% of the system mass was lost, is remarkable. Our analysis of Wolf 1130 allows us to infer its formation and evolutionary history, which has unique implications for understanding low-mass star and brown dwarf formation around intermediate mass stars.Comment: 37 pages, 9 Figures, 5 Table

A Candidate Young Massive Planet in Orbit around the Classical T Tauri Star CI Tau

The ~2 Myr old classical T Tauri star CI Tau shows periodic variability in its radial velocity (RV) variations measured at infrared (IR) and optical wavelengths. We find that these observations are consistent with a massive planet in a ~9-day period orbit. These results are based on 71 IR RV measurements of this system obtained over 5 years, and on 26 optical RV measurements obtained over 9 years. CI Tau was also observed photometrically in the optical on 34 nights over ~one month in 2012. The optical RV data alone are inadequate to identify an orbital period, likely the result of star spot and activity induced noise for this relatively small dataset. The infrared RV measurements reveal significant periodicity at ~9 days. In addition, the full set of optical and IR RV measurements taken together phase coherently and with equal amplitudes to the ~9 day period. Periodic radial velocity signals can in principle be produced by cool spots, hot spots, and reflection of the stellar spectrum off the inner disk, in addition to resulting from a planetary companion. We have considered each of these and find the planet hypothesis most consistent with the data. The radial velocity amplitude yields an Msin(i) of ~8.1 M_Jup; in conjunction with a 1.3 mm continuum emission measurement of the circumstellar disk inclination from the literature, we find a planet mass of ~11.3 M_Jup, assuming alignment of the planetary orbit with the disk.Comment: 61 pages, 13 figures, accepted for publication in The Astrophysical Journa

The Effects Of Caffeine On Early Second Half Sprint Performance In NCAA DIII Women’s Soccer Players

Objective The purpose of this study was to examine the effects of caffeine on early second half sprint performance in 21 NCAA DIII women’s soccer players. The caffeine dosage attempted to approximate a liquid dosage many student athletes typically consume. Design In a randomized double blind repeated measures design, subjects began the protocol after ingestion of caplets containing 3 mg.kg-1 of caffeine (CAF) and after ingestion of placebo (PLA) caplets. Pre-game, warm-up, and first half conditions were designed to maximize external validity. Methods An adapted version of the Loughborough Intermittent Shuttle Test was applied to replicate first half activity. Sprint performance was measured with the Running Based Anaerobic Sprint Test. Mean power, maximum power, and minimum power, were assessed under each condition. Repeated measures MANOVA was used to determine if there were significant mean vector differences between the trials. Results Although mean, maximum, and minimum power in the CAF trial increased 3.2%, 3.4%, and 4% respectively, MANOVA results showed no statistically significant differences in the mean vector for power variables (Λ = .752, p \u3e .05). Conclusions The lack of statistical significance in this study is likely attributed to the relationship between a small, although contextually plausible, relative caffeine dosage and an extended exercise time. The results also suggest caffeine ingestion of 3 mg.kg-1 should not be considered capable of improving sprint performance at the start of the second half

Observations of Reactive Gaseous Mercury in the Free Troposphere at the Mount Bachelor Observatory

We measured gaseous elemental mercury (GEM), particulate mercury (PHg), and reactive gaseous mercury (RGM), along with CO, ozone, and aerosol scatter at the Mount Bachelor Observatory (2.7 km above sea level), Oregon, from May to August 2005. The mean mercury concentrations (at standard conditions) were 1.54 ng/m3 (GEM), 5.2 pg/m3 (PHg), and 43 pg/m3 (RGM). RGM enhancements, up to 600 pg/m3, occurred at night and were linked to a diurnal pattern of upslope and downslope flows that mixed in boundary layer air during the day and free tropospheric air at night. During the night, RGM was inversely correlated (P < 0.0001) with CO (r = −0.36), GEM (r = −0.73), and H2O (r = −0.44), was positively correlated with ozone (r = 0.38), and could not be linked to recent anthropogenic emissions from local sources or long-range transport. Principal component analysis and a composite of change in RGM versus change in GEM during RGM enhancements indicate that a nearly quantitative shift in speciation is associated with increases in ozone and decreases in water vapor and CO. This argues that high concentrations of RGM are present in the free troposphere because of in situ oxidation of GEM to RGM. A global chemical transport model reproduces the RGM mean and diurnal pattern but underestimates the magnitude of the largest observed enhancements. Since the only modeled, in situ RGM production mechanisms are oxidation of GEM by ozone and OH, this implies that there are faster reaction rates or additional RGM production mechanisms in the free troposphere.Earth and Planetary SciencesEngineering and Applied Science

Diesel particulate matter emission factors and air quality implications from in–service rail in Washington State, USA

AbstractWe sought to evaluate the air quality implications of rail traffic at two sites in Washington State. Our goals were to quantify the exposure to diesel particulate matter (DPM) and airborne coal dust from current trains for residents living near the rail lines and to measure the DPM and black carbon emission factors (EFs). We chose two sites in Washington State, one at a residence along the rail lines in the city of Seattle and one near the town of Lyle in the Columbia River Gorge (CRG). At each site, we made measurements of size–segregated particulate matter (PM1, PM2.5 and PM10), CO2 and meteorology, and used a motion–activated camera to capture video of each train for identification. We measured an average DPM EF of 0.94g/kg diesel fuel, with an uncertainty of 20%, based on PM1 and CO2 measurements from more than 450 diesel trains. We found no significant difference in the average DPM EFs measured at the two sites. Open coal trains have a significantly higher concentration of particles greater than 1μm diameter, likely coal dust. Measurements of black carbon (BC) at the CRG site show a strong correlation with PM1 and give an average BC/DPM ratio of 52% from diesel rail emissions. Our measurements of PM2.5 show that living close to the rail lines significantly increases PM2.5 exposure. For the one month of measurements at the Seattle site, the average PM2.5 concentration was 6.8μg/m3 higher near the rail lines compared to the average from several background locations. Because the excess PM2.5 exposure for residents living near the rail lines is likely to be linearly related to the diesel rail traffic density, a 50% increase in rail traffic may put these residents over the new U.S. National Ambient Air Quality Standards, an annual average of 12μg/m3