38052681
Eclipsing Binary Science via the Merging of Transit and Doppler Exoplanet Survey Data—A Case Study with the MARVELS Pilot Project and SuperWASP
Exoplanet transit and Doppler surveys discover many binary stars during their operation that can be used to conduct a variety of ancillary science. Specifically, eclipsing binary stars can be used to study the stellar mass-radius relationship and to test predictions of theoretical stellar evolution models. By cross-referencing 24 binary stars found in the MARVELS Pilot Project with SuperWASP photometry, we find two new eclipsing binaries, TYC 0272-00458-1 and TYC 1422-01328-1, which we use as case studies to develop a general approach to eclipsing binaries in survey data. TYC 0272-00458-1 is a single-lined spectroscopic binary for which we calculate a mass of the secondary and radii for both components using reasonable constraints on the primary mass through several different techniques. For a primary mass of M_1 = 0.92 ± 0.1 M_☉, we find M_2 = 0.610 ± 0.036 M_☉, R_1 = 0.932 ± 0.076 R_☉, and R_2 = 0.559 ± 0.102 R_☉, and find that both stars have masses and radii consistent with model predictions. TYC 1422-01328-1 is a triple-component system for which we can directly measure the masses and radii of the eclipsing pair. We find that the eclipsing pair consists of an evolved primary star (M_1 = 1.163 ± 0.034 M_☉, R_1 = 2.063 ± 0.058 R_☉) and a G-type dwarf secondary (M_2 = 0.905 ± 0.067 M_☉, R_2 = 0.887 ± 0.037 R_☉). We provide the framework necessary to apply this analysis to much larger data sets.
119032296
Modelling collision products of triple‐star mergers
In dense stellar clusters, binary-single and binary-binary encounters can ultimately lead to collisions involving two or more stars during a resonant interaction. A comprehensive survey of multistar collisions would needto explore an enormous amount of parameter space, but here we focus on a number of representative cases involving low-mass (0.4-, 0.6- and 0.8-M O .) main-sequence stars. Using both smoothed particle hydrodynamics (SPH) calculations and a much faster fluid sorting software package (MMAS), we study scenarios in which a newly formed product from an initial collision collides with a third parent star. By varying the order in which the parent stars collide, as well as the orbital parameters of the collision trajectories, we investigate how factors such as shock heating affect the chemical composition and structure profiles of the collision product. Our simulations and models indicate that the distribution of most chemical elements within the final product is not significantly affected by the order in which the stars collide, the direction of approach of the third parent star, or the periastron separations of the collisions. Although the exact surface abundances of beryllium and lithium in the product do depend on the details of the dynamics, these elements are always severely depleted due to mass loss during the collisions. We find that the sizes of the products, and hence their collisional cross-sections for subsequent encounters, can be sensitive to the order and geometry of the collisions. For the cases that we consider, the radius of the product formed in the first (single-single star) collision ranges anywhere from roughly 2-30 times the sum of the radii of its parent stars. The size of the final product formed in our triple-star collisions is more difficult to determine, but it can easily be as large or larger than a typical red giant. Although the vast majority of the volume in such a product contains diffuse gas that could be readily stripped in subsequent interactions, we nevertheless expect the collisional cross-section of a newly formed product to be greatly enhanced over that of a thermally relaxed star of the same mass. Our results also help establish that the algorithms of MMAS can quickly reproduce the important features of our SPH models for these collisions, even when one of the parent stars is itself a former product.
118312614
SPITZER AND NEAR-INFRARED OBSERVATIONS OF A NEW BIPOLAR PROTOSTELLAR OUTFLOW IN THE ROSETTE MOLECULAR CLOUD
We present and discuss Spitzer and near-infrared H2 observations of a new bipolar protostellar outflow in the Rosette Molecular Cloud. The outflow is seen in all four InfraRed Array Camera (IRAC) bands and partially as diffuse emission in the MIPS 24 μm band. An embedded MIPS 24 μm source bisects the outflow and appears to be the driving source. This source is coincident with a dark patch seen in absorption in the 8 μm IRAC image. Spitzer IRAC color analysis of the shocked emission was performed from which thermal and column density maps of the outflow were constructed. Narrowband near-infrared (NIR) images of the flow reveal H2 emission features coincident with the high temperature regions of the outflow. This outflow has now been given the designation MHO 1321 due to the detection of NIR H2 features. We use these data and maps to probe the physical conditions and structure of the flow.
15434364
An Inexpensive Field-Widened Monolithic Michelson Interferometer for Precision Radial Velocity Measurements
ABSTRACT. We have constructed a thermally compensated field-widened monolithic Michelson interferometer that can be used with a medium-resolution spectrograph to measure precise Doppler radial velocities of stars. Our prototype monolithic fixed-delay interferometer is constructed with off-the-shelf components and assembled using a hydrolysis bonding technique. We installed and tested this interferometer in the Exoplanet Tracker (ET) instrument at the Kitt Peak 2.1 m telescope, an instrument built to demonstrate the principles of dispersed fixed-delay interferometry. An iodine cell allows the interferometer drift to be accurately calibrated, relaxing the stability requirements on the interferometer itself. When using our monolithic interferometer, the ET instrument has no moving parts (except the iodine cell), greatly simplifying its operation. We demonstrate differential radial velocity precision of a few m s-1 m s - 1 on well known radial velocity standards and planet bearing stars when using this inte...
13879217
The First Extrasolar Planet Discovered with a New-Generation High-Throughput Doppler Instrument
We report the detection of the first extrasolar planet, ET-1 (HD 102195b), using the Exoplanet Tracker (ET), a new-generation Doppler instrument. The planet orbits HD 102195, a young star with solar metallicity that may be part of the local association. The planet imparts radial velocity variability to the star with a semiamplitude of 63.4 ± 2.0 m s-1 and a period of 4.11 days. The planetary minimum mass (m sin i) is 0.488MJ ± 0.015MJ. The planet was initially detected in the spring of 2005 with the Kitt Peak National Observatory (KPNO) 0.9 m coude feed telescope. The detection was confirmed by radial velocity observations with the ET at the KPNO 2.1 m telescope and also at the 9 m Hobby-Eberly Telescope (HET) with its High Resolution Spectrograph. This planetary discovery with a 0.9 m telescope around a V = 8.05 magnitude star was made possible by the high throughput of the instrument: 49% measured from the fiber output to the detector. The ET's interferometer-based approach is an effective method for planet detection. In addition, the ET concept is adaptable to multiple-object Doppler observations or very high precision observations with a cross-dispersed echelle spectrograph to separate stellar fringes over a broad wavelength band. In addition to spectroscopic observations of HD 102195, we obtained brightness measurements with one of the automated photometric telescopes at Fairborn Observatory. Those observations reveal that HD 102195 is a spotted variable star with an amplitude of ~0.015 mag and a 12.3 ± 0.3 day period. This is consistent with spectroscopically observed Ca II H and K emission levels and line-broadening measurements but inconsistent with rotational modulation of surface activity as the cause of the radial velocity variability. Our photometric observations rule out transits of the planetary companion.
45393848
Jets from massive unstable particles: Top-mass determination
We construct jet observables for energetic top quarks that can be used to determine a short-distance top quark mass from reconstruction in e+e- collisions with accuracy better than LambdaQCD. Using a sequence of effective field theories we connect the production energy, mass, and top width scales, Q>>m>>Gamma, for the top jet cross section, and derive a QCD factorization theorem for the top invariant mass spectrum. Our analysis accounts for alphas corrections from the production and mass scales, corrections due to constraints in defining invariant masses, nonperturbative corrections from the cross talk between the jets, and alphas corrections to the Breit-Wigner line shape. This paper mainly focuses on deriving the factorization theorem for hemisphere invariant mass distributions and other event shapes in e+e- collisions applicable at a future linear collider. We show that the invariant mass distribution is not a simple Breit-Wigner function involving the top width. Even at leading order it is shifted and broadened by nonperturbative soft QCD effects. We predict that the invariant mass peak position increases linearly with Q/m due to these nonperturbative effects. They are encoded in terms of a universal soft function that also describes soft effects for massless dijet events. In a future paper we compute alphas corrections to the jet invariant mass spectrum, including a summation of large logarithms between the scales Q, m, and Gamma.
2043741
Summing Sudakov logarithms in B ---> X(s gamma) in effective field theory
We construct an effective field theory valid for processes in which highly energetic light-like particles interact with collinear and soft degrees of freedom, using the decay B -> X_s + gamma near the endpoint of the photon spectrum, x = 2 E_gamma / m_b -> 1, as an example. Below the scale mu=m_b both soft and collinear degrees of freedom are included in the effective theory, while below the scale mu=m_b sqrt{x-y}, where 1-y is the lightcone momentum fraction of the b quark in the B meson, we match onto a theory of bilocal operators. We show that at one loop large logarithms cancel in the matching conditions, and that we recover the well known renormalization group equations that sum leading Sudakov logarithms.
116268330
Rapidity Divergences and Deep Inelastic Scattering in the Endpoint Region
The deep inelastic scattering cross section in the endpoint region, $x \sim 1$, has been subjected to extensive analysis. We revisit this process, and show that in the endpoint individual factors in the factorized hadronic tensor have rapidity divergences. We regulate these divergences using a recently introduced rapidity regulator, and find that each factor requires a different scale to minimize large rapidity logarithms. Interestingly, in this case running in rapidity is non-perturbative. In addition, we give an operator definition of the parton distribution function in the endpoint region, and remark on the issues that should be considered in constructing this function.
119508366
Flavor-singlet light-cone amplitudes and radiative Upsilon decays in SCET
We study the evolution of flavor-singlet, light-cone amplitudes in the soft-collinear effective theory (SCET), and reproduce results previously obtained by a different approach. We apply our calculation to the color-singlet contribution to the photon endpoint in radiative Upsilon decay. In a previous paper, we studied the color-singlet contributions to the endpoint, but neglected operator mixing, arguing that it should be a numerically small effect. Nevertheless the mixing needs to be included in a consistent calculation, and we do just that in this work. We find that the effects of mixing are indeed numerically small. This result combined with previous work on the color-octet contribution and the photon fragmentation contribution provides a consistent theoretical treatment of the photon spectrum in radiative Upsilon decay.
117895382
Exclusive Radiative Decays of Upsilon in SCET
We study exclusive radiative decays of the $\Upsilon$ using soft-collinear effective theory and non-relativistic QCD. In contrast to inclusive radiative decays at the endpoint we find that color-octet contributions are power suppressed in exclusive decays, and can safely be neglected, greatly simplifying the analysis. We determine the complete set of Lorentz structures that can appear in the SCET Wilson coefficients and match onto them using results from a previous calculation. We run these coefficients from the scale $\mups$ to the scale $\Lambda \sim 1 \textrm{GeV}$, thereby summing large logarithms. Finally we use our results to predict the ratio of branching fractions $B(\Upsilon \to \gamma f_2)/B(J/\psi \to \gamma f_2)$, $B(J/\psi \to \gamma f_2)/B(\psi' \to \gamma f_2)$, and the partial rate for $\Upsilon \to \gamma \pi \pi$.