H$alpha$ and EUV observations of a partial CME

We have obtained H$alpha$ high spatial and time resolution observations of the upper solar chromosphere and supplemented these with multi-wavelength observations from the Solar Dynamic Observatory (SDO) and the {it Hinode} ExtremeUltraviolet Imaging Spectrometer (EIS). The H$alpha$ observations were conducted on 11 February 2012 with the Hydrogen-Alpha Rapid Dynamics Camera (HARDcam) instrument at the National Solar Observatorys Dunn Solar Telescope. Our H$alpha$ observations found large downflows of chromospheric material returning from coronal heights following a failed prominence eruption. We have detected several large condensations (blobs) returning to the solar surface at velocities of $approx$200 km s$^{-1}$ in both H$alpha$ and several SDO AIA band passes. The average derived size of these blobs in H$alpha$ is 500 by 3000 km$^2$ in the directions perpendicular and parallel to the direction of travel, respectively. A comparison of our blob widths to those found from coronal rain, indicate there are additional smaller, unresolved blobs in agreement with previous studies and recent numerical simulations. Our observed velocities and decelerations of the blobs in both H$alpha$ and SDO bands are less than those expected for gravitational free-fall and imply additional magnetic or gas pressure impeding the flow. We derived a kinetic energy $approx$2 orders of magnitude lower for the main eruption than a typical CME, which may explain its partial nature.

Constraints on the radio loud/radio quiet dichotomy from the fundamental plane

The fundamental plane for black hole activity constitutes a tight correlation between jet power, X-ray luminosity, and black hole mass. Under the assumption that a Blandford-Znajek-type mechanism, which relies on black hole spin, contributes non-negligibly to jet production, the sufficiently small scatter in the fundamental plane shows that black hole spin differences of $mid$$Delta$a$mid sim$1 are not typical among the active galactic nuclei population. If $-$ as it seems $-$ radio loud and radio quiet objects are both faithful to the fundamental plane, models of black hole accretion in which the radio loud/radio quiet dichotomy is based on a spin dichotomy of a$sim$1/a$sim$0, respectively, are difficult to reconcile with the observations. We show how recent theoretical work based on differences in accretion flow orientation between retrograde and prograde, accommodates a small scatter in the fundamental plane for objects that do have non-negligible differences in black hole spin values. We also show that the dichotomy in spin between the most radio loud and the most radio quiet involves $mid$$Delta$a$mid approx$0. And, finally, we show how the picture that produces compatibility with the fundamental plane, also allows one to interpret other otherwise puzzling observations of jets across the mass scale including 1) the recently observed inverse relation between radio and X-rays at higher Eddington ratios in both black hole X-ray binaries as well as active galactic nuclei and 2) the apparent contradiction between jet power and black hole spin observed in X-ray hard and transitory burst states in X-ray binaries.

Emission lines between 1 and 2 keV in Cometary X-ray Spectra

We present the detection of new cometary X-ray emission lines in the 1.0 to 2.0 keV range using a sample of comets observed with the Chandra X-ray observatory and ACIS spectrometer. We have selected 5 comets from the Chandra sample with good signal-to-noise spectra. The surveyed comets are: C/1999 S4 (LINEAR), C/1999 T1 (McNaught-Hartley), 153P/2002 (Ikeya-Zhang), 2P/2003 (Encke), and C/2008 8P (Tuttle). We modeled the spectra with an extended version of our solar wind charge exchange (SWCX) emission model (Bodewits et al. 2007). Above 1 keV, we find Ikeya-Zhang to have strong emission lines at 1340 and 1850 eV that we identify as being created by solar wind charge exchange lines of Mg XI and Si XIII, respectively, and weaker emission lines at 1470, 1600, and 1950 eV formed by SWCX of Mg XII, Mg XI, and Si XIV, respectively. The Mg XI and XII and Si XIII and XIV lines are detected at a significant level for the other comets in our sample (LS4, MH, Encke, 8P), and these lines promise additional diagnostics to be included in SWCX models. The silicon lines in the 1700 to 2000 eV range are detected for all comets, but with the rising background and decreasing cometary emission, we caution these detections need further confirmation with higher resolution instruments.

A search for line intensity enhancements in the far-UV spectra of active late-type stars arising from opacity

Radiative transfer calculations have predicted intensity enhancements for optically thick emission lines, as opposed to the normal intensity reductions, for astrophysical plasmas under certain conditions. In particular, the results are predicted to be dependent both on the geometry of the emitting plasma and the orientation of the observer. Hence in principle the detection of intensity enhancement may provide a way of determining the geometry of an unresolved astronomical source. To investigate such enhancements we have analyzed a sample of active late-type stars observed in the far ultraviolet spectral region. Emission lines of O VI in the FUSE satellite spectra of epsilon Eri, II Peg and Prox Cen were searched for intensity enhancements due to opacity. We have found strong evidence for line intensity enhancements due to opacity during active or flare-like activity for all three stars. The O VI 1032/1038 line intensity ratios, predicted to have a value of 2.0 in the optically thin case, are found to be up to ~30% larger during several orbital phases. Our measurements, combined with radiative transfer models, allow us to constrain both the geometry of the O VI emitting regions in our stellar sources and the orientation of the observer. A spherical emitting plasma can be ruled out, as this would lead to no intensity enhancement. In addition, the theory tells us that the line-of-sight to the plasma must be close to perpendicular to its surface, as observations at small angles to the surface lead to either no intensity enhancement or the usual line intensity decrease over the optically thin value. For the future, we outline a laboratory experiment, that could be undertaken with current facilities, which would provide an unequivocal test of predictions of line intensity enhancement due to opacity, in particular the dependence on plasma geometry.

The Search for Super-saturation in Chromospheric Emission

We investigate if the super-saturation phenomenon observed at X-ray wavelengths for the corona, exists in the chromosphere for rapidly rotating late-type stars. Moderate resolution optical spectra of fast rotating EUV- and X-ray- selected late-type stars were obtained. Stars in alpha Per were observed in the northern hemisphere with the Isaac Newton 2.5 m telescope and IDS spectrograph. Selected objects from IC 2391 and IC 2602 were observe in the southern hemisphere with the Blanco 4m telescope and R-C spectrograph at CTIO. Ca II H & K fluxes were measured for all stars in our sample. We find the saturation level for Ca II K at log(L_CaK/L_bol) = -4.08. The Ca II K flux does not show a decrease as a function of increased rotational velocity or smaller Rossby number as observed in the X-ray. This lack of super-saturation supports the idea of coronal-stripping as the cause of saturation and super-saturation in stellar chromospheres and corona, but the detailed underlying mechanism is still under investigation.

Comparison of current models for Hot Jupiters to the sample of transiting exoplanets

A growing number (over 100!) of extra-solar planets (ESPs) have been discovered by transit photometry, and these systems are important because the transit strongly constrains their orbital inclination and allows accurate physical parameters for the planet to be derived, especially their radii. Their mass-radius relation allows us to probe their internal structure. In the present work we calculate Safronov numbers for the current sample of ESP and compare their masses and radii to current models with the goal of obtaining better constrains on their formation processe. Our calculation of Safronov numbers for the current TESP sample does show 2 classes, although about 20% lie above the formal Class I definition. These trends and recent results that argue against a useful distinction between Safronov classes are under further investigation. Mass-radius relations for the current sample of TESP are inconsistent with ESP models with very large core masses (geq 100 Moplus). Most TESP with radii near 1RJ are consistent with models with no core mass or core masses of 10 Moplus . The inflated planets, with radii geq 1.2 RJ are not consistent with current ESP models, but may lie along the lower end of models for brown dwarfs. Although such models are nascent, it is important to establish trends for the current sample of ESP, which will further the understanding of their formation and evolution.

Chandra Observations of Comets 8P/Tuttle and 17P/Holmes during Solar Minimum

We present results for Chandra observations of comets, 17P/Holmes (17P) and 8P/Tuttle (8P). 17P was observed for 30 ksec right after its major outburst, on 31 Oct 2007 (10:07 UT) and comet 8P/Tuttle was observed in 2008 January for 47 ksec. During the two Chandra observations, 17P was producing at least 100 times more water than 8P but was 2.2 times further away from the Sun. Also, 17P is the first comet observed at high latitude (+19.1 degrees) during solar minimum, while 8P was observed at a lower solar latitude (3.4 degrees). The X-ray spectrum of 17P is unusually soft with little significant emission at energies above 500 eV. Depending on our choice of background, we derive a 300 to 1000 eV flux of 0.5 to 4.5 x 10^-13 ergs/cm2/sec, with over 90% of the emission in the 300 to 400 eV range. This corresponds to an X-ray luminosity between 0.4 to 3.3 x 10^15 ergs/sec. 17Ps lack of X-rays in the 400 to 1000 eV range, in a simple picture, may be attributed to the polar solar wind, which is depleted in highly charged ions. 8P/Tuttle was much brighter, with an average count rate of 0.20 counts/s in the 300 to 1000 eV range. We derive an average X-ray flux in this range of 9.4 x 10^-13 ergs/cm2/sec and an X-ray luminosity for the comet of 1.7 x 10^14 ergs/sec. The light curve showed a dramatic decrease in flux of over 60% between observations on January 1st and 4th. When comparing outer regions of the coma to inner regions, its spectra showed a decrease in ratios of CVI/CV, OVIII/OVII, as predicted by recent solar wind charge exchange emission models. There are remarkable differences between the X-ray emission from these two comets, further demonstrating the qualities of cometary X-ray observations, and solar wind charge exchange emission in more general as a means of remote diagnostics of the interaction of astrophysical plasmas.

WASP-10b: a 3M_J, gas-giant planet transiting a late-type K star

We report the discovery of WASP-10b, a new transiting extrasolar planet (ESP) discovered by the WASP Consortium and confirmed using NOT FIES and SOPHIE radial velocity data. A 3.09 day period, 29 mmag transit depth, and 2.36 hour duration are derived for WASP-10b using WASP and high precision photometric observations. Simultaneous fitting to the photometric and radial velocity data using a Markov-chain Monte Carlo procedure leads to a planet radius of 1.28R_J, a mass of 2.96M_J and eccentricity of ~0.06. WASP-10b is one of the more massive transiting ESPs, and we compare its characteristics to the current sample of transiting ESP, where there is currently little information for masses greater than ~2M_J and non-zero eccentricities. WASP-10s host star, GSC 2752-00114 (USNO-B1.0 1214-0586164) is among the fainter stars in the WASP sample, with V=12.7 and a spectral type of K5. This result shows promise for future late-type dwarf star surveys.

Spectral Analysis of the Chandra Comet Survey

We present results of the analysis of cometary X-ray spectra with an extended version of our charge exchange emission model (Bodewits et al. 2006). We have applied this model to the sample of 8 comets thus far observed with the Chandra X-ray observatory and ACIS spectrometer in the 300-1000 eV range. The surveyed comets are C/1999 S4 (LINEAR), C/1999 T1 (McNaught-Hartley), C/2000 WM1 (LINEAR), 153P/2002 (Ikeya-Zhang), 2P/2003 (Encke), C/2001 Q4 (NEAT), 9P/2005 (Tempel 1) and 73P/2006-B (Schwassmann-Wachmann 3) and the observations include a broad variety of comets, solar wind environments and observational conditions. The interaction model is based on state selective, velocity dependent charge exchange cross sections and is used to explore how cometary X-ray emission depend on cometary, observational and solar wind characteristics. It is further demonstrated that cometary X-ray spectra mainly reflect the state of the local solar wind. The current sample of Chandra observations was fit using the constrains of the charge exchange model, and relative solar wind abundances were derived from the X-ray spectra. Our analysis showed that spectral differences can be ascribed to different solar wind states, as such identifying comets interacting with (I) fast, cold wind, (II), slow, warm wind and (III) disturbed, fast, hot winds associated with interplanetary coronal mass ejections. We furthermore predict the existence of a fourth spectral class, associated with the cool, fast high latitude wind.