Open Access. Powered by Scholars. Published by Universities.®
- Discipline
- Keyword
-
- Techniques: photometric (27)
- Techniques: radial velocities (20)
- Planetary systems (14)
- Stars: early-type (13)
- Planets and satellites: detection (11)
-
- Outflows (9)
- Stars: winds (9)
- X-rays: stars (9)
- Astrophysics - Earth and Planetary Astrophysics (8)
- Exoplanet astronomy (8)
- Stars: magnetic field (8)
- Stars: massive (8)
- Exoplanet systems (6)
- Exoplanets (6)
- Transit photometry (6)
- Planets and satellites: fundamental parameters (5)
- Radial velocity (5)
- Stars: low-mass (5)
- Stars: mass-loss (5)
- Techniques: spectroscopic (5)
- Astrophysics - Solar and Stellar Astrophysics (4)
- Binaries: general (4)
- Planets and satellites: gaseous planets (4)
- Planets and satellites: general (4)
- Protoplanetary disks (4)
- Stars: late-type (4)
- Stars: rotation (4)
- Exoplanet detection methods (3)
- Exoplanet evolution (3)
- M dwarf stars (3)
Articles 151 - 180 of 221
Full-Text Articles in Astrophysics and Astronomy
Constraints On A Second Planet In The Wasp-3 System, G. Maciejewski, A. Niedzielski, A. Wolszczan, G. Nowak, R. Neuhäuser, J. N. Winn, B. Deka, M. Adamów, M. Górecka, M. Fernández, F. J. Aceituno, J. Ohlert, R. Errmann, M. Seeliger, D. P. Dimitrov, D. W. Latham, G. A. Esquerdo, L. Mcknight, M. J. Holman, Eric L.N. Jensen, U. Kramm, T. Pribulla, S. Raetz, T. O.B. Schmidt, C. Ginski, S. Mottola, S. Hellmich, C. Adam, H. Gilbert, M. Mugrauer, G. Saral, V. Popov, M. Raetz
Constraints On A Second Planet In The Wasp-3 System, G. Maciejewski, A. Niedzielski, A. Wolszczan, G. Nowak, R. Neuhäuser, J. N. Winn, B. Deka, M. Adamów, M. Górecka, M. Fernández, F. J. Aceituno, J. Ohlert, R. Errmann, M. Seeliger, D. P. Dimitrov, D. W. Latham, G. A. Esquerdo, L. Mcknight, M. J. Holman, Eric L.N. Jensen, U. Kramm, T. Pribulla, S. Raetz, T. O.B. Schmidt, C. Ginski, S. Mottola, S. Hellmich, C. Adam, H. Gilbert, M. Mugrauer, G. Saral, V. Popov, M. Raetz
Physics & Astronomy Faculty Works
There have been previous hints that the transiting planet WASP-3b is accompanied by a second planet in a nearby orbit, based on small deviations from strict periodicity of the observed transits. Here we present 17 precise radial velocity (RV) measurements and 32 transit light curves that were acquired between 2009 and 2011. These data were used to refine the parameters of the host star and transiting planet. This has resulted in reduced uncertainties for the radii and masses of the star and planet. The RV data and the transit times show no evidence for an additional planet in the system. …
Kelt-3b: A Hot Jupiter Transiting A V=9.8 Late-F Star, J. Pepper, R. J. Siverd, T. G. Beatty, B. S. Gaudi, K. G. Stassun, J. D. Eastman, K. Collins, D. W. Latham, A. Bieryla, L. A. Buchhave, Eric L.N. Jensen, M. Manner, K. Penev, J. R. Crepp, P. A. Cargile, Saurav Dhital , '06, M. L. Calkins, G. A. Esquerdo, P. Berlind, B. J. Fulton, R. Street, B. Ma, J. Ge, J. Wang, Q. Mao, A. J.W. Richert, A. Gould, D. L. Depoy, J. F. Kielkopf, J. L. Marshall, R. W. Pogge, R. P. Stefanik, M. Trueblood, P. Trueblood
Kelt-3b: A Hot Jupiter Transiting A V=9.8 Late-F Star, J. Pepper, R. J. Siverd, T. G. Beatty, B. S. Gaudi, K. G. Stassun, J. D. Eastman, K. Collins, D. W. Latham, A. Bieryla, L. A. Buchhave, Eric L.N. Jensen, M. Manner, K. Penev, J. R. Crepp, P. A. Cargile, Saurav Dhital , '06, M. L. Calkins, G. A. Esquerdo, P. Berlind, B. J. Fulton, R. Street, B. Ma, J. Ge, J. Wang, Q. Mao, A. J.W. Richert, A. Gould, D. L. Depoy, J. F. Kielkopf, J. L. Marshall, R. W. Pogge, R. P. Stefanik, M. Trueblood, P. Trueblood
Physics & Astronomy Faculty Works
We report the discovery of KELT-3b, a moderately inflated transiting hot Jupiter with a mass of 1.477(-0.067)(+0.066) M-J, radius of 1.345 +/- 0.072 R-J, and an orbital period of 2.7033904 +/- 0.000010 days. The host star, KELT-3, is a V = 9.8 late F star with M-* = 1.278(-0.061)(+0.063) M-circle dot, R-* = 1.472(-0.067)(+0.065) R-circle dot, T-eff = 6306(-49)(+50) K, log(g) = 4.209(-0.031)(+0.033), and [Fe/H] = 0.044(-0.082)(+0.080), and has a likely proper motion companion. KELT-3b is the third transiting exoplanet discovered by the KELT survey, and is orbiting one of the 20 brightest known transiting planet host stars, making it …
The Stellar Content Of The Young Open Cluster Trumpler 37, R. Errmann, R. Neuhäuser, L. Marschall, G. Torres, M. Mugrauer, W. P. Chen, S. C.-L. Hu, C. Briceño, R. Chini, L. Bukowiecki, D. P. Dimitrov, D. P. Kjurkchieva, Eric L.N. Jensen, David H. Cohen, Z.-Y. Wu, T. Pribulla, M. Vaňko, V. Krushevska, J. Budaj, Y. Oasa, A. K. Pandey, M. Fernández, A. Kellerer, C. Marka
The Stellar Content Of The Young Open Cluster Trumpler 37, R. Errmann, R. Neuhäuser, L. Marschall, G. Torres, M. Mugrauer, W. P. Chen, S. C.-L. Hu, C. Briceño, R. Chini, L. Bukowiecki, D. P. Dimitrov, D. P. Kjurkchieva, Eric L.N. Jensen, David H. Cohen, Z.-Y. Wu, T. Pribulla, M. Vaňko, V. Krushevska, J. Budaj, Y. Oasa, A. K. Pandey, M. Fernández, A. Kellerer, C. Marka
Physics & Astronomy Faculty Works
With an apparent cluster diameter of 1.5 degrees and an age of 4 Myr, Trumpler 37 is an ideal target for photometric monitoring of young stars as well as for the search of planetary transits, eclipsing binaries and other sources of variability. The YETI consortium has monitored Trumpler 37 throughout 2010 and 2011 to obtain a comprehensive view of variable phenomena in this region. In this first paper we present the cluster properties and membership determination as derived from an extensive investigation of the literature. We also compared the coordinate list to some YETI images. For 1872 stars we found …
Wind Channeling, Magnetospheres, And Spindown Of Magnetic Massive Stars, S. P. Owocki, A. Ud-Doula, R. H. D. Townsend, V. Petit, J. O. Sundqvist, David H. Cohen
Wind Channeling, Magnetospheres, And Spindown Of Magnetic Massive Stars, S. P. Owocki, A. Ud-Doula, R. H. D. Townsend, V. Petit, J. O. Sundqvist, David H. Cohen
Physics & Astronomy Faculty Works
A subpopulation (~10%) of hot, luminous, massive stars have been revealed through spectropolarimetry to harbor strong (hundreds to tens of thousand Gauss), steady, large-scale (often significantly dipolar) magnetic fields. This review focuses on the role of such fields in channeling and trapping the radiatively driven wind of massive stars, including both in the strongly perturbed outflow from open field regions, and the wind-fed “magnetospheres” that develop from closed magnetic loops. For B-type stars with weak winds and moderately fast rotation, one finds “centrifugal magnetospheres”, in which rotational support allows magnetically trapped wind to accumulate to a large density, with quite …
Constraints On Porosity And Mass Loss In O-Star Winds From The Modeling Of X-Ray Emission Line Profile Shapes, M. A. Leutenegger, David H. Cohen, J. O. Sundqvist, S. P. Owocki
Constraints On Porosity And Mass Loss In O-Star Winds From The Modeling Of X-Ray Emission Line Profile Shapes, M. A. Leutenegger, David H. Cohen, J. O. Sundqvist, S. P. Owocki
Physics & Astronomy Faculty Works
We fit X-ray emission line profiles in high resolution XMM-Newton and Chandra grating spectra of the early O supergiant zeta Pup with models that include the effects of porosity in the stellar wind. We explore the effects of porosity due to both spherical and flattened clumps. We find that porosity models with flattened clumps oriented parallel to the photosphere provide poor fits to observed line shapes. However, porosity models with isotropic clumps can provide acceptable fits to observed line shapes, but only if the porosity effect is moderate. We quantify the degeneracy between porosity effects from isotropic clumps and the …
Improved Orbital Parameters And Transit Monitoring For Hd 156846b, S. R. Kane, A. W. Howard, G. Pilyavsky, S. Mahadevan, G. W. Henry, K. Von Braun, D. R. Ciardi, D. Dragomir, D. A. Fischer, Eric L.N. Jensen, G. Laughlin, S. V. Ramirez, J. T. Wright
Improved Orbital Parameters And Transit Monitoring For Hd 156846b, S. R. Kane, A. W. Howard, G. Pilyavsky, S. Mahadevan, G. W. Henry, K. Von Braun, D. R. Ciardi, D. Dragomir, D. A. Fischer, Eric L.N. Jensen, G. Laughlin, S. V. Ramirez, J. T. Wright
Physics & Astronomy Faculty Works
HD 156846b is a Jovian planet in a highly eccentric orbit (e = 0.85) with a period of 359.55 days. The pericenter passage at a distance of 0.16 AU is nearly aligned to our line of sight, offering an enhanced transit probability of 5.4% and a potentially rich probe of the dynamics of a cool planetary atmosphere impulsively heated during close approach to a bright star (V = 6.5). We present new radial velocity (RV) and photometric measurements of this star as part of the Transit Ephemeris Refinement and Monitoring Survey. The RV measurements from the Keck-High Resolution Echelle Spectrometer …
Host Star Properties And Transit Exclusion For The Hd 38529 Planetary System, G. W. Henry, S. R. Kane, S. X. Wang, T. S. Boyajian, K. Von Braun, D. R. Ciardi, D. Dragomir, C. Farrington, D. A. Fischer, N. R. Hinkel, A. W. Howard, Eric L.N. Jensen, G. Laughlin, S. Mahadevan, G. Pilyavsky
Host Star Properties And Transit Exclusion For The Hd 38529 Planetary System, G. W. Henry, S. R. Kane, S. X. Wang, T. S. Boyajian, K. Von Braun, D. R. Ciardi, D. Dragomir, C. Farrington, D. A. Fischer, N. R. Hinkel, A. W. Howard, Eric L.N. Jensen, G. Laughlin, S. Mahadevan, G. Pilyavsky
Physics & Astronomy Faculty Works
The transit signature of exoplanets provides an avenue through which characterization of exoplanetary properties may be undertaken, such as studies of mean density, structure, and atmospheric composition. The Transit Ephemeris Refinement and Monitoring Survey is a program to expand the catalog of transiting planets around bright host stars by refining the orbits of known planets discovered with the radial velocity technique. Here we present results for the HD 38529 system. We determine fundamental properties of the host star through direct interferometric measurements of the radius and through spectroscopic analysis. We provide new radial velocity measurements that are used to improve …
Thin-Shell Mixing In Radiative Wind-Shocks And The L-X Similar To L-Bol Scaling Of O-Star X-Rays, S. P. Owocki, J. O. Sundqvist, David H. Cohen, K. G. Gayley
Thin-Shell Mixing In Radiative Wind-Shocks And The L-X Similar To L-Bol Scaling Of O-Star X-Rays, S. P. Owocki, J. O. Sundqvist, David H. Cohen, K. G. Gayley
Physics & Astronomy Faculty Works
X-ray satellites since Einstein have empirically established that the X-ray luminosity from single O-stars scales linearly with bolometric luminosity, L-x similar to 10(-7)L(bol). But straightforward forms of the most favoured model, in which X-rays arise from instability-generated shocks embedded in the stellar wind, predict a steeper scaling, either with mass-loss rate L-x similar to(M)over dot similar to L-bol(1.7) if the shocks are radiative or with L-x similar to (M)over dot(2) similar to L-bol(3.4) if they are adiabatic. This paper presents a generalized formalism that bridges these radiative versus adiabatic limits in terms of the ratio of the shock cooling length …
A Magnetic Confinement Versus Rotation Classification Of Massive-Star Magnetospheres, V. Petit, S. P. Owocki, G. A. Wade, David H. Cohen, J. O. Sundqvist, M. Gagné, J. Maíz Apellániz, M. E. Oksala, D. A. Bohlender, T. Rivinius, H. F. Henrichs, E. Alecian, R. H.D. Townsend, A. Ud-Doula
A Magnetic Confinement Versus Rotation Classification Of Massive-Star Magnetospheres, V. Petit, S. P. Owocki, G. A. Wade, David H. Cohen, J. O. Sundqvist, M. Gagné, J. Maíz Apellániz, M. E. Oksala, D. A. Bohlender, T. Rivinius, H. F. Henrichs, E. Alecian, R. H.D. Townsend, A. Ud-Doula
Physics & Astronomy Faculty Works
Building on results from the Magnetism in Massive Stars (MiMeS) project, this paper shows how a two-parameter classification of massive-star magnetospheres in terms of the magnetic wind confinement (which sets the Alfvén radius RA) and stellar rotation (which sets the Kepler co-rotation radius RK) provides a useful organization of both observational signatures and theoretical predictions. We compile the first comprehensive study of inferred and observed values for relevant stellar and magnetic parameters of 64 confirmed magnetic OB stars with Teff ≳ 16 kK. Using these parameters, we locate the stars in the magnetic confinement–rotation diagram, a log–log plot of RK …
Discovery Of A Magnetic Field In The Rapidly Rotating O-Type Secondary Of The Colliding-Wind Binary Hd 47129 (Plaskett's Star), J. H. Grunhut, G. A. Wade, M. A. Leutenegger, V. Petit, G. Rauw, C. Neiner, F. Martins, David H. Cohen, M. Gagné, R. Ignace, S. Mathis, S. E. De Mink, A. F.J. Moffat, S. P. Owocki, M. Shultz, J. O. Sundqvist
Discovery Of A Magnetic Field In The Rapidly Rotating O-Type Secondary Of The Colliding-Wind Binary Hd 47129 (Plaskett's Star), J. H. Grunhut, G. A. Wade, M. A. Leutenegger, V. Petit, G. Rauw, C. Neiner, F. Martins, David H. Cohen, M. Gagné, R. Ignace, S. Mathis, S. E. De Mink, A. F.J. Moffat, S. P. Owocki, M. Shultz, J. O. Sundqvist
Physics & Astronomy Faculty Works
We report the detection of a strong, organized magnetic field in the secondary component of the massive O8III/I+O7.5V/III double-lined spectroscopic binary system HD 47129 (Plaskett's star) in the context of the Magnetism in Massive Stars survey. Eight independent Stokes V observations were acquired using the Echelle SpectroPolarimetric Device for the Observations of Stars (ESPaDOnS) spectropolarimeter at the Canada-France-Hawaii Telescope and the Narval spectropolarimeter at the Telescope Bernard Lyot. Using least-squares deconvolution we obtain definite detections of signal in Stokes V in three observations. No significant signal is detected in the diagnostic null (N) spectra. The Zeeman signatures are broad and …
Kelt-1b: A Strongly Irradiated, Highly Inflated, Short Period, 27 Jupiter-Mass Companion Transiting A Mid-F Star, R. J. Siverd, T. G. Beatty, J. Pepper, J. D. Eastman, K. Collins, A. Bieryla, D. W. Latham, L. A. Buchhave, Eric L.N. Jensen, J. R. Crepp, R. Street, K. G. Stassun, B. S. Gaudi, P. Berlind, M. L. Calkins, D. L. Depoy, G. A. Esquerdo, B. J. Fulton, G. Fürész, J. C. Geary, A. Gould, L. Hebb, J. F. Kielkopf, J. L. Marshall, R. Pogge, K. Z. Stanek, R. P. Stefanik, A. H. Szentgyorgyi, M. Trueblood, P. Trueblood, A. M. Stutz, J. L. Van Saders
Kelt-1b: A Strongly Irradiated, Highly Inflated, Short Period, 27 Jupiter-Mass Companion Transiting A Mid-F Star, R. J. Siverd, T. G. Beatty, J. Pepper, J. D. Eastman, K. Collins, A. Bieryla, D. W. Latham, L. A. Buchhave, Eric L.N. Jensen, J. R. Crepp, R. Street, K. G. Stassun, B. S. Gaudi, P. Berlind, M. L. Calkins, D. L. Depoy, G. A. Esquerdo, B. J. Fulton, G. Fürész, J. C. Geary, A. Gould, L. Hebb, J. F. Kielkopf, J. L. Marshall, R. Pogge, K. Z. Stanek, R. P. Stefanik, A. H. Szentgyorgyi, M. Trueblood, P. Trueblood, A. M. Stutz, J. L. Van Saders
Physics & Astronomy Faculty Works
We present the discovery of KELT-1b, the first transiting low-mass companion from the wide-field Kilodegree Extremely Little Telescope-North (KELT-North) transit survey. A joint analysis of the spectroscopic, radial velocity, and photometric data indicates that the V = 10.7 primary is a mildly evolved mid-F star with T-eff = 6516 +/- 49 K, log g = 4.228(-0.021)(+0.014), and [Fe/H] = 0.052 +/- 0.079, with an inferred mass M* = 1.335 +/- 0.063M(circle dot) and radius R* = 1.471(-0.035)(+0.045) R-circle dot. The companion is a low-mass brown dwarf or a super-massive planet with mass M-P = 27.38 +/- 0.93 M-Jup and radius …
The X-Ray View Of Ob Star Wind Structure And Dynamics, David H. Cohen
The X-Ray View Of Ob Star Wind Structure And Dynamics, David H. Cohen
Physics & Astronomy Faculty Works
High-resolution X-ray grating spectroscopy enables us to measure the kinematics and spatial distribution of the shock-heated wind plasma in O and early B stars, testing the predictions of the embedded wind shock scenario of massive star X-ray production. By fitting models to the resolved, Doppler broadened X-ray emission line profiles measured by the Chandra X-ray Observatory's grating spectrometer, we find an onset radius of X-ray production of roughly Ro = 1.5 R★ for the O supergiants, ζ Pup and HD 93129A. From the profile fitting we also find that the terminal velocity of the X-ray emitting plasma is consistent with …
Kelt-2ab: A Hot Jupiter Transiting The Bright (V=8.77) Primary Star Of A Binary System, T. G. Beatty, J. Pepper, R. J. Siverd, J. D. Eastman, A. Bieryla, D. W. Latham, L. A. Buchhave, Eric L.N. Jensen, M. Manner, K. G. Stassun, B. S. Gaudi, P. Berlind, M. L. Calkins, K. Collins, D. L. Depoy, G. A. Esquerdo, B. J. Fulton, G. Fürész, J. C. Geary, A. Gould, L. Hebb, J. F. Kielkopf, J. L. Marshall, R. Pogge, K. Z. Stanek, R. P. Stefanik, R. Street, A. H. Szentgyorgyi, M. Trueblood, P. Trueblood, A. M. Stutz
Kelt-2ab: A Hot Jupiter Transiting The Bright (V=8.77) Primary Star Of A Binary System, T. G. Beatty, J. Pepper, R. J. Siverd, J. D. Eastman, A. Bieryla, D. W. Latham, L. A. Buchhave, Eric L.N. Jensen, M. Manner, K. G. Stassun, B. S. Gaudi, P. Berlind, M. L. Calkins, K. Collins, D. L. Depoy, G. A. Esquerdo, B. J. Fulton, G. Fürész, J. C. Geary, A. Gould, L. Hebb, J. F. Kielkopf, J. L. Marshall, R. Pogge, K. Z. Stanek, R. P. Stefanik, R. Street, A. H. Szentgyorgyi, M. Trueblood, P. Trueblood, A. M. Stutz
Physics & Astronomy Faculty Works
We report the discovery of KELT-2Ab, a hot Jupiter transiting the bright (V = 8.77) primary star of the HD 42176 binary system. The host is a slightly evolved late F-star likely in the very short-lived "blue-hook" stage of evolution, with T-eff = 6148 +/- 48 K, log g = 4.030(-0.026)(+0.015) and [Fe/H] = 0.034 +/- 0.78. The inferred stellar mass is M-* = 1.314(-0.060)(+0.063) M-circle dot and the star has a relatively large radius of R-* = 1.836(-0.046)(+0.066) R-circle dot. The planet is a typical hot Jupiter with period 4.1137913 +/- 0.00001 days and a mass of M-P = …
The Hd 192263 System: Planetary Orbital Period And Stellar Variability Disentangled, D. Dragomir, S. R. Kane, G. W. Henry, D. R. Ciardi, D. A. Fischer, A. W. Howard, Eric L.N. Jensen, G. Laughlin, S. Mahadevan, J. M. Matthews, G. Pilyavsky, K. Von Braun, S. X. Wang, J. T. Wright
The Hd 192263 System: Planetary Orbital Period And Stellar Variability Disentangled, D. Dragomir, S. R. Kane, G. W. Henry, D. R. Ciardi, D. A. Fischer, A. W. Howard, Eric L.N. Jensen, G. Laughlin, S. Mahadevan, J. M. Matthews, G. Pilyavsky, K. Von Braun, S. X. Wang, J. T. Wright
Physics & Astronomy Faculty Works
As part of the Transit Ephemeris Refinement and Monitoring Survey, we present new radial velocities and photometry of the HD 192263 system. Our analysis of the already available Keck-HIRES and CORALIE radial velocity measurements together with the five new Keck measurements we report in this paper results in improved orbital parameters for the system. We derive constraints on the size and phase location of the transit window for HD 192263b, a Jupiter-mass planet with a period of 24.3587 +/- 0.0022 days. We use 10 years of Automated Photoelectric Telescope photometry to analyze the stellar variability and search for planetary transits. …
A Possible Detection Of Occultation By A Proto-Planetary Clump In Gm Cephei, W. P. Chen, S. C.-L. Hu, R. Errmann, C. Adam, S. Baar, A. Berndt, L. Bukowiecki, D. P. Dimitrov, T. Eisenbeiss, S. Fiedler, C. Ginski, C. Gräfe, J. K. Guo, M. M. Hohle, H. Y. Hsiao, R. Janulis, M. Kitze, H. C. Lin, C. S. Lin, G. Maciejewski, C. Marka, L. Marschall, M. Moualla, M. Mugrauer, R. Neuhäuser, T. Pribulla, S. Raetz, T. Röll, E. Schmidt, J. Schmidt, T. O.B. Schmidt, M. Seeliger, L. Trepl, C. Briceño, R. Chini, Eric L.N. Jensen, E. H. Nikogossian, A. K. Pandey, J. Sperauskas, H. Takahashi, F. M. Walter, Z. Y. Wu, X. Zhou
A Possible Detection Of Occultation By A Proto-Planetary Clump In Gm Cephei, W. P. Chen, S. C.-L. Hu, R. Errmann, C. Adam, S. Baar, A. Berndt, L. Bukowiecki, D. P. Dimitrov, T. Eisenbeiss, S. Fiedler, C. Ginski, C. Gräfe, J. K. Guo, M. M. Hohle, H. Y. Hsiao, R. Janulis, M. Kitze, H. C. Lin, C. S. Lin, G. Maciejewski, C. Marka, L. Marschall, M. Moualla, M. Mugrauer, R. Neuhäuser, T. Pribulla, S. Raetz, T. Röll, E. Schmidt, J. Schmidt, T. O.B. Schmidt, M. Seeliger, L. Trepl, C. Briceño, R. Chini, Eric L.N. Jensen, E. H. Nikogossian, A. K. Pandey, J. Sperauskas, H. Takahashi, F. M. Walter, Z. Y. Wu, X. Zhou
Physics & Astronomy Faculty Works
GM Cephei (GM Cep), in the young (similar to 4 Myr) open cluster Trumpler 37, has been known to be an abrupt variable and to have a circumstellar disk with a very active accretion. Our monitoring observations in 2009-2011 revealed that the star showed sporadic flare events, each with a brightening of less than or similar to 0.5 mag lasting for days. These brightening events, associated with a color change toward blue, should originate from increased accretion activity. Moreover, the star also underwent a brightness drop of similar to 1 mag lasting for about a month, during which time the …
A Generalized Porosity Formalism For Isotropic And Anisotropic Effective Opacity And Its Effects On X-Ray Line Attenuation In Clumped O Star Winds, J. O. Sundqvist, S. P. Owocki, David H. Cohen, M. A. Leutenegger, R. H.D. Townsend
A Generalized Porosity Formalism For Isotropic And Anisotropic Effective Opacity And Its Effects On X-Ray Line Attenuation In Clumped O Star Winds, J. O. Sundqvist, S. P. Owocki, David H. Cohen, M. A. Leutenegger, R. H.D. Townsend
Physics & Astronomy Faculty Works
We present a generalized formalism for treating the porosity-associated reduction in continuum opacity that occurs when individual clumps in a stochastic medium become optically thick. As in previous work, we concentrate on developing bridging laws between the limits of optically thin and thick clumps. We consider geometries resulting in either isotropic or anisotropic effective opacity, and, in addition to an idealized model in which all clumps have the same local overdensity and scale, we also treat an ensemble of clumps with optical depths set by Markovian statistics. This formalism is then applied to the specific case of boundfree absorption of …
A Search For The Transit Of Hd 168443b: Improved Orbital Parameters And Photometry, G. Pilyavsky, S. Mahadevan, S. R. Kane, A. W. Howard, D. R. Ciardi, C. De Pree, D. Dragomir, D. A. Fischer, G. W. Henry, Eric L.N. Jensen, G. Laughlin, H. Marlowe, M. Rabus, K. Von Braun, J. T. Wright, X. X. Wang
A Search For The Transit Of Hd 168443b: Improved Orbital Parameters And Photometry, G. Pilyavsky, S. Mahadevan, S. R. Kane, A. W. Howard, D. R. Ciardi, C. De Pree, D. Dragomir, D. A. Fischer, G. W. Henry, Eric L.N. Jensen, G. Laughlin, H. Marlowe, M. Rabus, K. Von Braun, J. T. Wright, X. X. Wang
Physics & Astronomy Faculty Works
The discovery of transiting planets around bright stars holds the potential to greatly enhance our understanding of planetary atmospheres. In this work we present the search for transits of HD 168443b, a massive planet orbiting the bright star HD 168443 (V = 6.92) with a period of 58.11 days. The high eccentricity of the planetary orbit (e = 0.53) significantly enhances the a priori transit probability beyond that expected for a circular orbit, making HD168443 a candidate for our ongoing Transit Ephemeris Refinement and Monitoring Survey. Using additional radial velocities from Keck High Resolution Echelle Spectrometer, we refined the orbital …
Chandra X-Ray Spectroscopy Of The Very Early O Supergiant Hd 93129a: Constraints On Wind Shocks And The Mass-Loss Rate, David H. Cohen, M. Gagné, M. A. Leutenegger, James Paton Macarthur , '11, Emma Edwina Wollman , '09, J. O. Sundqvist, A. W. Fullerton, S. P. Owocki
Chandra X-Ray Spectroscopy Of The Very Early O Supergiant Hd 93129a: Constraints On Wind Shocks And The Mass-Loss Rate, David H. Cohen, M. Gagné, M. A. Leutenegger, James Paton Macarthur , '11, Emma Edwina Wollman , '09, J. O. Sundqvist, A. W. Fullerton, S. P. Owocki
Physics & Astronomy Faculty Works
We present an analysis of both the resolved X-ray emission-line profiles and the broad-band X-ray spectrum of the O-2 If* star HD 93129A, measured with the Chandra High Energy Transmission Grating Spectrometer ( HETGS). This star is among the earliest and most massive stars in the Galaxy, and provides a test of the embedded wind-shock scenario in a very dense and powerful wind. A major new result is that continuum absorption by the dense wind is the primary cause of the hardness of the observed X-ray spectrum, while intrinsically hard emission from colliding wind shocks contributes less than 10 per …
The Young Exoplanet Transit Initiative (Yeti), R. Neuhäuser, R. Errmann, A. Berndt, G. Maciejewski, H. Takahashi, W. P. Chen, D. P. Dimitrov, T. Pribulla, E. H. Nikogossian, Eric L.N. Jensen, L. Marschall, Z.-Y. Wu, A. Kellerer, F. M. Walter, C. Briceño, R. Chini, M. Fernández, S. Raetz, G. Torres, D. W. Latham, S. N. Quinn, A. Niedzielski, L. Bukowiecki, G. Nowak, T. Tomov, K. Tachihara, S. C.-L. Hu, L. W. Hung, D. P. Kjurkchieva, V. S. Radeva, B. M. Mihov, L. Slavcheva-Mihova, I. N. Bozhinova, J. Budaj, M. Vanko, E. Kundra, L. Hambalek, V. Krushevska, T. Movsessian, H. Harutyunyan, J. J. Downes, J. Hernandez, V. H. Hoffmeister, David H. Cohen, Imoleayo Samson Abel , '14, Rebecca Ruby Ahmad , '14, Seth Walker Chapman , '14, Sierra Clare Eckert , '14, Jackson Goodman , '13, Adrien Charles Guerard , '14, H. M. Kim, Andrew Evan Koontharana , '11, Joshua Daniel Sokol , '11, Jennifer Trinh , '11, Yuwen Wang , '14, X. Zhou, R. Redmer, U. Kramm, N. Nettelmann, M. Mugrauer, J. Schmidt, M. Moualla, C. Ginski, C. Marka, C. Adam, M. Seeliger, S. Baar, T. Roell, T. O.B. Schmidt, L. Trepl, T. Eisenbeiss, S. Fiedler, N. Tetzlaff, E. Schmidt, M. M. Hohle, M. Kitze, N. Chakrova, C. Grafe, K. Schreyer, V. V. Hambaryan, C. H. Broeg, J. Koppenhoefer, A. K. Pandey
The Young Exoplanet Transit Initiative (Yeti), R. Neuhäuser, R. Errmann, A. Berndt, G. Maciejewski, H. Takahashi, W. P. Chen, D. P. Dimitrov, T. Pribulla, E. H. Nikogossian, Eric L.N. Jensen, L. Marschall, Z.-Y. Wu, A. Kellerer, F. M. Walter, C. Briceño, R. Chini, M. Fernández, S. Raetz, G. Torres, D. W. Latham, S. N. Quinn, A. Niedzielski, L. Bukowiecki, G. Nowak, T. Tomov, K. Tachihara, S. C.-L. Hu, L. W. Hung, D. P. Kjurkchieva, V. S. Radeva, B. M. Mihov, L. Slavcheva-Mihova, I. N. Bozhinova, J. Budaj, M. Vanko, E. Kundra, L. Hambalek, V. Krushevska, T. Movsessian, H. Harutyunyan, J. J. Downes, J. Hernandez, V. H. Hoffmeister, David H. Cohen, Imoleayo Samson Abel , '14, Rebecca Ruby Ahmad , '14, Seth Walker Chapman , '14, Sierra Clare Eckert , '14, Jackson Goodman , '13, Adrien Charles Guerard , '14, H. M. Kim, Andrew Evan Koontharana , '11, Joshua Daniel Sokol , '11, Jennifer Trinh , '11, Yuwen Wang , '14, X. Zhou, R. Redmer, U. Kramm, N. Nettelmann, M. Mugrauer, J. Schmidt, M. Moualla, C. Ginski, C. Marka, C. Adam, M. Seeliger, S. Baar, T. Roell, T. O.B. Schmidt, L. Trepl, T. Eisenbeiss, S. Fiedler, N. Tetzlaff, E. Schmidt, M. M. Hohle, M. Kitze, N. Chakrova, C. Grafe, K. Schreyer, V. V. Hambaryan, C. H. Broeg, J. Koppenhoefer, A. K. Pandey
Physics & Astronomy Faculty Works
We present the Young Exoplanet Transit Initiative (YETI), in which we use several 0.2 to 2.6-m telescopes around the world to monitor continuously young (<= 100 Myr), nearby (<= 1 kpc) stellar clusters mainly to detect young transiting planets (and to study other variability phenomena on time-scales from minutes to years). The telescope network enables us to observe the targets continuously for several days in order not to miss any transit. The runs are typically one to two weeks long, about three runs per year per cluster in two or three subsequent years for about ten clusters. There are thousands of stars detectable in each field with several hundred known cluster members, e. g. in the first cluster observed, Tr-37, a typical cluster for the YETI survey, there are at least 469 known young stars detected in YETI data down to R = 16.5 mag with sufficient precision of 50 millimag rms (5 mmag rms down to R = 14.5 mag) to detect transits, so that we can expect at least about one young transiting object in this cluster. If we observe similar to 10 similar clusters, we can expect to detect similar to 10 young transiting planets with radius determinations. The precision given above is for a typical telescope of the YETI network, namely the 60/90-cm Jena telescope (similar brightness limit, namely within +/-1 mag, for the others) so that planetary transits can be detected. For targets with a periodic transit-like light curve, we obtain spectroscopy to ensure that the star is young and that the transiting object can be sub-stellar; then, we obtain Adaptive Optics infrared images and spectra, to exclude other bright eclipsing stars in the (larger) optical PSF; we carry out other observations as needed to rule out other false positive scenarios; finally, we also perform spectroscopy to determine the mass of the transiting companion. For planets with mass and radius determinations, we can calculate the mean density and probe the internal structure. We aim to constrain planet formation models and their time-scales by discovering planets younger than similar to 100 Myr and determining not only their orbital parameters, but also measuring their true masses and radii, which is possible so far only by the transit method. Here, we present an overview and first results. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
An Introduction To The Chandra Carina Complex Project, L. K. Townsley, P. S. Broos, M. F. Corcoran, E. D. Feigelson, M. Gagné, T. Montmerle, M. S. Oey, N. Smith, G. P. Garmire, K. V. Getman, M. S. Povich, N. R. Evans, Y. Nazé, E. R. Parkin, T. Preibisch, J. Wang, S. J. Wou, Y.-H. Chu, David H. Cohen, R. A. Gruendl, K. Hamaguchi, R. R. King, M.-M. M. Low, M. J. Mccaughrean, A. F.J. Moffat, L. M. Oskinova, J. M. Pittard, K. G. Stassun, A. Ud-Doula, N. R. Walborn, W. L. Waldron, E. Churchwell, J. S. Nictiols, S. P. Owocki, N. S. Schulz
An Introduction To The Chandra Carina Complex Project, L. K. Townsley, P. S. Broos, M. F. Corcoran, E. D. Feigelson, M. Gagné, T. Montmerle, M. S. Oey, N. Smith, G. P. Garmire, K. V. Getman, M. S. Povich, N. R. Evans, Y. Nazé, E. R. Parkin, T. Preibisch, J. Wang, S. J. Wou, Y.-H. Chu, David H. Cohen, R. A. Gruendl, K. Hamaguchi, R. R. King, M.-M. M. Low, M. J. Mccaughrean, A. F.J. Moffat, L. M. Oskinova, J. M. Pittard, K. G. Stassun, A. Ud-Doula, N. R. Walborn, W. L. Waldron, E. Churchwell, J. S. Nictiols, S. P. Owocki, N. S. Schulz
Physics & Astronomy Faculty Works
The Great Nebula in Carina provides an exceptional view into the violent massive star formation and feedback that typifies giant H II regions and starburst galaxies. We have mapped the Carina star-forming complex in X-rays, using archival Chandra data and a mosaic of 20 new 60 ks pointings using the Chandra X-ray Observatory's Advanced CCD Imaging Spectrometer, as a testbed for understanding recent and ongoing star formation and to probe Carina's regions of bright diffuse X-ray emission. This study has yielded a catalog of properties of > 14,000 X-ray point sources;> 9800 of them have multiwavelength counterparts. Using Chandra's unsurpassed X-ray …
Global X-Ray Properties Of The O And B Stars In Carina, Y. Nazé, P. S. Broos, L. M. Oskinova, L. K. Townsley, David H. Cohen, M. F. Corcoran, N. R. Evans, M. Gagné, A. F.J. Moffat, J. M. Pittard, G. Rauw, A. Ud-Doula, N. R. Walborn
Global X-Ray Properties Of The O And B Stars In Carina, Y. Nazé, P. S. Broos, L. M. Oskinova, L. K. Townsley, David H. Cohen, M. F. Corcoran, N. R. Evans, M. Gagné, A. F.J. Moffat, J. M. Pittard, G. Rauw, A. Ud-Doula, N. R. Walborn
Physics & Astronomy Faculty Works
The key empirical property of the X-ray emission from O stars is a strong correlation between the bolometric and X-ray luminosities. In the framework of the Chandra Carina Complex Project, 129 O and B stars have been detected as X-ray sources; 78 of those, all with spectral type earlier than B3, have enough counts for at least a rough X-ray spectral characterization. This leads to an estimate of the L-X-L-BOL ratio for an exceptional number of 60 O stars belonging to the same region and triples the number of Carina massive stars studied spectroscopically in X-rays. The derived log(L-X/L-BOL) is …
Carina Ob Stars: X-Ray Signatures Of Wind Shocks And Magnetic Fields, M. Gagné, G. Fehon, M. R. Savoy, David H. Cohen, L. K. Townsley, P. S. Broos, M. S. Povich, M. F. Corcoran, N. R. Walborn, N. R. Evans, A. F.J. Moffat, Y. Nazé, L. M. Oskinova
Carina Ob Stars: X-Ray Signatures Of Wind Shocks And Magnetic Fields, M. Gagné, G. Fehon, M. R. Savoy, David H. Cohen, L. K. Townsley, P. S. Broos, M. S. Povich, M. F. Corcoran, N. R. Walborn, N. R. Evans, A. F.J. Moffat, Y. Nazé, L. M. Oskinova
Physics & Astronomy Faculty Works
The Chandra Carina Complex contains 200 known O- and B-type stars. The Chandra survey detected 68 of the 70 O stars and 61 of 127 known B0-B3 stars. We have assembled a publicly available optical/X-ray database to identify OB stars that depart from the canonical L-X/L-bol relation or whose average X-ray temperatures exceed 1 keV. Among the single O stars with high kT we identify two candidate magnetically confined wind shock sources: Tr16-22, O8.5 V, and LS 1865, O8.5 V((f)). The O4 III(fc) star HD 93250 exhibits strong, hard, variable X-rays, suggesting that it may be a massive binary with …
V474 Car: A Rare Halo Rs Cvn Binary In Retrograde Galactic Orbit, E. J. Bubar, E. E. Mamajek, Eric L.N. Jensen, F. M. Walter
V474 Car: A Rare Halo Rs Cvn Binary In Retrograde Galactic Orbit, E. J. Bubar, E. E. Mamajek, Eric L.N. Jensen, F. M. Walter
Physics & Astronomy Faculty Works
We report the discovery that the star V474 Car is an extremely active, high velocity halo RS CVn system. The star was originally identified as a possible pre-main-sequence star in Carina, given its enhanced stellar activity, rapid rotation (10.3 days), enhanced Li, and absolute magnitude which places it above the main sequence (MS). However, its extreme radial velocity (264 km s–1) suggested that this system was unlike any previously known pre-MS system. Our detailed spectroscopic analysis of echelle spectra taken with the CTIO 4 m finds that V474 Car is both a spectroscopic binary with an orbital period …
X-Ray Spectral Diagnostics Of Activity In Massive Stars, David H. Cohen, Emma Edwina Wollman , '09, M. A. Leutenegger
X-Ray Spectral Diagnostics Of Activity In Massive Stars, David H. Cohen, Emma Edwina Wollman , '09, M. A. Leutenegger
Physics & Astronomy Faculty Works
X-rays give direct evidence of instabilities, time-variable structure, and shock heating in the winds of O stars. The observed broad X-ray emission lines provide information about the kinematics of shock-heated wind plasma, enabling us to test wind-shock models. And their shapes provide information about wind absorption, and thus about the wind mass-loss rates. Mass-loss rates determined from X-ray line profiles are not sensitive to density-squared clumping effects, and indicate mass-loss rate reductions of factors of 3 to 6 over traditional diagnostics that suffer from density-squared effects. Broad-band X-ray spectral energy distributions also provide mass-loss rate information via soft X-ray absorption …
A Multiphase Suzaku Study Of X-Rays From Τ Sco, R. Ignace, L. M. Oskinova, M. Jardine, J. P. Cassinelli, David H. Cohen, J.-F. Donati, R. H.D. Townsend, A. Ud-Doula
A Multiphase Suzaku Study Of X-Rays From Τ Sco, R. Ignace, L. M. Oskinova, M. Jardine, J. P. Cassinelli, David H. Cohen, J.-F. Donati, R. H.D. Townsend, A. Ud-Doula
Physics & Astronomy Faculty Works
We obtained relatively high signal-to-noise X-ray spectral data of the early massive star tau Sco (B0.2V) with the Suzaku X-ray Imaging Spectrometer (XIS) instrument. This source displays several unusual features that motivated our study: (1) redshifted absorption in UV P Cygni lines to approximately +250 km s(-1) suggestive of infalling gas, (2) unusually hard X-ray emission requiring hot plasma at temperatures in excess of 10 MK whereas most massive stars show relatively soft X-rays at a few MK, and (3) a complex photospheric magnetic field of open and closed field lines. In an attempt to understand the hard component better, …
Modeling Broadband X-Ray Absorption Of Massive Star Winds, M. A. Leutenegger, David H. Cohen, J. Zsargó, Erin Marie Martell , '09, James Paton Macarthur , '11, S. P. Owocki, M. Gagné, D. J. Hillier
Modeling Broadband X-Ray Absorption Of Massive Star Winds, M. A. Leutenegger, David H. Cohen, J. Zsargó, Erin Marie Martell , '09, James Paton Macarthur , '11, S. P. Owocki, M. Gagné, D. J. Hillier
Physics & Astronomy Faculty Works
We present a method for computing the net transmission of X-rays emitted by shock-heated plasma distributed throughout a partially optically thick stellar wind from a massive star. We find the transmission by an exact integration of the formal solution, assuming that the emitting plasma and absorbing plasma are mixed at a constant mass ratio above some minimum radius, below which there is assumed to be no emission. This model is more realistic than either the slab absorption associated with a corona at the base of the wind or the exospheric approximation that assumes that all observed X-rays are emitted without …
A Mass-Loss Rate Determination For Zeta Puppis From The Quantitative Analysis Of X-Ray Emission-Line Profiles, David H. Cohen, M. A. Leutenegger, Emma Edwina Wollman , '09, J. Zsargó, D. J. Hillier, R. H.D. Townsend, S. P. Owocki
A Mass-Loss Rate Determination For Zeta Puppis From The Quantitative Analysis Of X-Ray Emission-Line Profiles, David H. Cohen, M. A. Leutenegger, Emma Edwina Wollman , '09, J. Zsargó, D. J. Hillier, R. H.D. Townsend, S. P. Owocki
Physics & Astronomy Faculty Works
We fit every emission line in the high-resolution Chandra grating spectrum of. Pup with an empirical line profile model that accounts for the effects of Doppler broadening and attenuation by the bulk wind. For each of 16 lines or line complexes that can be reliably measured, we determine a best-fitting fiducial optical depth, tau(*) equivalent to kappa(M) over dot/4 pi R(*)upsilon(infinity), and place confidence limits on this parameter. These 16 lines include seven that have not previously been reported on in the literature. The extended wavelength range of these lines allows us to infer, for the first time, a clear …
Discovery Of Rotational Braking In The Magnetic Helium-Strong Star Sigma Orionis E, R. H.D. Townsend, M. E. Oksala, David H. Cohen, S. P. Owocki, A. Ud-Doula
Discovery Of Rotational Braking In The Magnetic Helium-Strong Star Sigma Orionis E, R. H.D. Townsend, M. E. Oksala, David H. Cohen, S. P. Owocki, A. Ud-Doula
Physics & Astronomy Faculty Works
We present new U-band photometry of the magnetic helium-strong star sigma Ori E, obtained over 2004-2009 using the SMARTS 0.9 m telescope at Cerro Tololo Inter-American Observatory. When combined with historical measurements, these data constrain the evolution of the star's 1.19 day rotation period over the past three decades. We are able to rule out a constant period at the p(null) = 0.05% level, and instead find that the data are well described (p(null) = 99.3%) by a period increasing linearly at a rate of 77 ms per year. This corresponds to a characteristic spin-down time of 1.34 Myr, in …
A Test Of Pre-Main-Sequence Lithium Depletion Models, Jennifer Chun Ming Yee , '07, Eric L.N. Jensen
A Test Of Pre-Main-Sequence Lithium Depletion Models, Jennifer Chun Ming Yee , '07, Eric L.N. Jensen
Physics & Astronomy Faculty Works
Despite the extensive study of lithium depletion during pre-main-sequence (PMS) contraction, studies of individual stars show discrepancies between ages determined from the Hertzsprung-Russell (H-R) diagram and ages determined from lithium depletion, indicating open questions in the PMS evolutionary models. To further test these models, we present high-resolution spectra for members of the beta Pictoris Moving Group (BPMG), which is young and nearby. We measure equivalent widths of the 6707.8 angstrom Li I line in these stars and use them to determine lithium abundances. We combine the lithium abundance with the predictions of PMS evolutionary models in order to calculate a …
Discovery Of A Magnetic Field In The O9 Sub-Giant Star Hd 57682 By The Mimes Collaboration, J. H. Grunhut, G. A. Wade, W. L.F. Marcolino, V. Petit, H. F. Henrichs, David H. Cohen, E. Alecian, D. A. Bohlender, J.-C. Bouret, O. Kochukhov, C. Neiner, N. St. Louis, R. H.D. Townsend
Discovery Of A Magnetic Field In The O9 Sub-Giant Star Hd 57682 By The Mimes Collaboration, J. H. Grunhut, G. A. Wade, W. L.F. Marcolino, V. Petit, H. F. Henrichs, David H. Cohen, E. Alecian, D. A. Bohlender, J.-C. Bouret, O. Kochukhov, C. Neiner, N. St. Louis, R. H.D. Townsend
Physics & Astronomy Faculty Works
We report the detection of a strong, organized magnetic field in the O9IV star HD 57682, using spectropolarimetric observations obtained with ESPaDOnS at the 3.6-m Canada-France-Hawaii Telescope within the context of the Magnetism in Massive Stars (MiMeS) Large Programme. From the fitting of our spectra using non-local thermodynamic equilibrium model atmospheres, we determined that HD 57682 is a 17(-9)(+19)M(circle dot) star with a radius of 7.0(-1.8)(+2.4)R(circle dot) and a relatively low mass-loss rate of 1.4(-0.95)(+3.1) x 10(-9) M(circle dot) yr(-1). The photospheric absorption lines are narrow, and we use the Fourier transform technique to infer v sin i = 15 …