Browsing by Subject "parallaxes"
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Item Astrometry, Radial Velocity, And Photometry: The Hd 128311 System Remixed With Data From Hst, Het, And Apt(2014-11) McArthur, Barbara E.; Benedict, G. Fritz; Henry, Gregory W.; Hatzes, Artie; Cochran, William D.; Harrison, Thomas E.; Johns-Krull, Chris; Nelan, Ed; McArthur, Barbara E.; Benedict, G. Fritz; Cochran, William D.We have used high-cadence radial velocity measurements from the Hobby-Eberly Telescope with published velocities from the Lick 3 m Shane Telescope, combined with astrometric data from the Hubble Space Telescope (HST) Fine Guidance Sensors to refine the orbital parameters of the HD 128311 system, and determine an inclination of 55.degrees 95 +/- 14.degrees 55 and true mass of 3.789(+0.924)(-0.432) M-JUP for HD 128311 c. The combined radial velocity data also reveal a short period signal which could indicate a third planet in the system with an M sin i of 0.133 +/- 0.005 M-JUP or stellar phenomena. Photometry from the T12 0.8 m automatic photometric telescope at the Fairborn Observatory and HST are used to determine a photometric period close to, but not within the errors of the radial velocity signal. We performed a cross-correlation bisector analysis of the radial velocity data to look for correlations with the photometric period and found none. Dynamical integrations of the proposed system show long-term stability with the new orbital parameters of over 10 million years. Our new orbital elements do not support the claims of HD 128311 b and c being in mean motion resonance.Item The Bolocam Galactic Plane Survey. V. HCO+ and N2H+ Spectroscopy of 1.1 mm Dust Continuum Sources(2011-08) Schlingman, Wayne M.; Shirley, Yancy L.; Schenk, David E.; Rosolowsky, Erik; Bally, John; Battersby, Cara; Dunham, Miranda K.; Ellsworth-Bowers, Timothy P.; Evans, Neal J., II; Ginsburg, Adam; Stringfellow, Guy; Evans, Neal J., IIWe present the results of observations of 1882 sources in the Bolocam Galactic Plane Survey (BGPS) at 1.1 mm with the 10 m Henrich Hertz Telescope simultaneously in HCO+ J = 3-2 and N2H+ J = 3-2. We detect 77% of these sources in HCO+ and 51% in N2H+ at greater than 3 sigma. We find a strong correlation between the integrated intensity of both dense gas tracers and the 1.1 mm dust emission of BGPS sources. We determine kinematic distances for 529 sources (440 in the first quadrant breaking the distance ambiguity and 89 in the second quadrant). We derive the size, mass, and average density for this subset of clumps. The median size of BGPS clumps is 0.75 pc with a median mass of 330M(circle dot) (assuming T-Dust = 20 K). The median HCO+ linewidth is 2.9 km s(-1) indicating that BGPS clumps are dominated by supersonic turbulence or unresolved kinematic motions. We find no evidence for a size-linewidth relationship for BGPS clumps. We analyze the effects of the assumed dust temperature on the derived clump properties with a Monte Carlo simulation and find that changing the temperature distribution will change the median source properties (mass, volume-averaged number density, surface density) by factors of a few. The observed differential mass distribution has a power-law slope that is intermediate between that observed for diffuse CO clouds and the stellar initial mass function. BGPS clumps represent a wide range of objects (from dense cores to more diffuse clumps) and are typically characterized by larger sizes and lower densities than previously published surveys of high-mass star-forming regions. This collection of objects is a less-biased sample of star-forming regions in the Milky Way that likely span a wide range of evolutionary states.Item High Angular Resolution Imaging And Infrared Spectroscopy Of CoRoT Candidates(2013-08) Guenther, E. W.; Fridlund, M.; Alonso, R.; Carpano, S.; Deeg, H. J.; Deleuil, M.; Dreizler, S.; Endl, M.; Gandolfi, D.; Gillon, M.; Guillot, T.; Jehin, E.; Leger, A.; Moutou, C.; Nortmann, L.; Rouan, D.; Samuel, B.; Schneider, J.; Tingley, B.; Endl, M.Context. Studies of transiting extrasolar planets are of key importance for understanding the nature of planets outside our solar system because their masses, diameters, and bulk densities can be measured. An important part of transit-search programmes is the removal of false-positives. In the case of the CoRoT space mission, the majority of the false-positives are removed by a detailed analysis of the light curves and by seeing-limited imaging in- and out-of-transit. However, the critical question is how many of the candidates that passed all these tests are false-positives. Such false-positives can be caused by eclipsing binaries, which are either related or unrelated to the targets. Aims. For our study we selected 25 CoRoT candidates that have already been screened against false-positives using detailed analysis of the light curves and seeing-limited imaging, which has transits that are between 0.7 and 0.05% deep. Our aim is to search for companion candidates that had not been recognized in previous observations. Methods. We observed 20 candidates with the adaptive optics imager NaCo and 18 with the high-resolution infrared spectrograph CRIRES. Results. We found previously unknown stars within 2 0 0 of the targets in seven of the candidates. All of these are too faint and too close to the targets to have been previously detected with seeing-limited telescopes in the optical. Our study thus leads to the surprising results that if we remove all candidates excluded by the sophisticated analysis of the light-curve, as well as carrying out deep imaging with seeing-limited telescopes, still 28 35% of the remaining candidates are found to possess companions that are bright enough to be false-positives. Conclusions. Given that the companion candidates cluster around the targets and that the J - K colours are consistent with physical companions, we conclude that the companion candidates are more likely to be physical companions rather than unrelated field stars.Item Hubble Space Telescope Fine Guidance Sensor Parallaxes For Four Classical Novae(2013-04) Harrison, Thomas E.; Bornak, Jilian; McArthur, Barbara E.; Benedict, G. Fritz; McArthur, Barbara E.; Benedict, G. FritzWe have used data obtained with the Fine Guidance Sensors on the Hubble Space Telescope to derive precise astrometric parallaxes for four classical novae: V603 Aql, DQ Her, GK Per, and RR Pic. All four objects exceeded the Eddington limit at visual maximum. Re-examination of the original light curve data for V603 Aql and GK Per has led us to conclude that their visual maxima were slightly brighter than commonly assumed. With known distances, we examine the various maximum magnitude-rate of decline relationships that have been established for classical novae. We find that these four objects show a similar level of scatter about these relationships as seen in larger samples of novae whose distances were determined using indirect techniques. We also examine the nebular expansion parallax method and find that it fails for three of the four objects. In each case it was possible to find an explanation for the failure of that technique to give precise distance estimates. DQ Her appears to suffer from an anomalously high extinction when compared to field stars on its sight line. We suggest that this is likely due to local material, which may also be the source of the IRAS detections of this object.Item The Mass-Luminosity Relation In The L/T Transition: Individual Dynamical Masses For The New J-Band Flux Reversal Binary SDSS J105213.51+442255.7Ab(2015-05) Dupuy, Trent J.; Liu, Michael C.; Leggett, S. K.; Ireland, Michael J.; Chiu, Kuenley; Golimowski, David A.; Dupuy, Trent J.We have discovered that SDSS J105213.51+442255.7 (T0.5 +/- 1.0) is a binary in Keck laser guide star adaptive optics imaging, displaying a large J- to K-band flux reversal (Delta J = -0.45 +/- 0.09 mag, Delta K= 0.52 +/- 0.05 mag). We determine a total dynamical mass from Keck orbital monitoring (88 +/- 5 M-Jup) and a mass ratio by measuring the photocenter orbit from CFHT/WIRCam absolute astrometry (M-B/M-A= 0.78 +/- 0.07). Combining these provides the first individual dynamical masses for any field L or T dwarfs, 49 +/- 3 M-Jup for the L6.5 +/- 1.5 primary and 39 +/- 3 M-Jup for the T1.5 +/- 1.0 secondary. Such a low mass ratio for a nearly equal luminosity binary implies a shallow mass-luminosity relation over the L/T transition (Delta log L-bol/Delta log M = 0.6(-0.8)(+0.6)). This provides the first observational support that cloud dispersal plays a significant role in the luminosity evolution of substellar objects. Fully cloudy models fail our coevality test for this binary, giving ages for the two components that disagree by 0.2 dex (2.0 sigma). In contrast, our observed masses and luminosities can be reproduced at a single age by "hybrid" evolutionary tracks where a smooth change from a cloudy to cloudless photosphere around 1300 K causes slowing of luminosity evolution. Remarkably, such models also match our observed JHK flux ratios and colors well. Overall, it seems that the distinguishing features SDSS J1052+ 4422AB, like a J-band flux reversal and high-amplitude variability, are normal for a field L/T binary caught during the process of cloud dispersal, given that the age (1.11(-0.20)(+0.17) Gyr) and surface gravity (log g = 5.0-5.2) of SDSS J1052+ 4422AB are typical for field ultracool dwarfs.Item A Technique To Derive Improved Proper Motions For Kepler Objects Of Interest(2014-12) Benedict, G. Fritz; Tanner, Angelle M.; Cargile, Phillip A.; Ciardi, David R.; Benedict, G. FritzWe outline an approach yielding proper motions with higher precision than exists in present catalogs for a sample of stars in the Kepler field. To increase proper-motion precision, we combine first-moment centroids of Kepler pixel data from a single season with existing catalog positions and proper motions. We use this astrometry to produce improved reduced-proper-motion diagrams, analogous to a Hertzsprung-Russell (H-R) diagram, for stars identified as Kepler objects of interest. The more precise the relative proper motions, the better the discrimination between stellar luminosity classes. Using UCAC4 and PPMXL epoch 2000 positions (and proper motions from those catalogs as quasi-Bayesian priors), astrometry for a single test Channel (21) and Season (0) spanning 2 yr yields proper motions with an average per-coordinate proper-motion error of 1.0 mas yr(-1), which is over a factor of three better than existing catalogs. We apply a mapping between a reduced-proper-motion diagram and an H-R diagram, both constructed using Hubble Space Telescope parallaxes and proper motions, to estimate Kepler object of interest K-band absolute magnitudes. The techniques discussed apply to any future small-field astrometry as well as to the rest of the Kepler field.