Astrophysics and Astronomy Commons^™

Rotational And Cyclical Variability In Γ Cassiopeiae. Ii. Fifteen Seasons, Gregory W. Henry, Myron A. Smith

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The B0.5 IVe star γ Cas is of great interest because it is the prototype of a small group of classical Be stars having hard X-ray emission of unknown origin. We discuss results from ongoing B and V observations of the γ Cas star–disk system acquired with an Automated Photometric Telescope during the observing seasons 1997–2011. In an earlier study, Smith, Henry, & Vishniac showed that light variations in γ Cas are dominated by a series of comparatively prominent cycles with amplitudes of 0.02–0.03 mag and lengths of 2–3 months, superimposed on a 1.21 day periodic signal some five times …

Non-Detection Of Previously Reported Transits Of Hd 97658b With Most* Photometry, Diana Dragomir, Jaymie M. Matthews, Andrew W. Howard, Victoria Antoci, Gregory W. Henry, David B. Guenther, John A. Johnson, Rainer Kuschnig, Geoffrey W. Marcy, Anthony F. J. Moffat, Jason F. Rowe, Slavek M. Rucinski, Dimitar Sasselov, Werner W. Weiss

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The radial velocity-discovered exoplanet HD 97658b was recently announced to transit, with a derived planetary radius of 2.93 ± 0.28 R⊕. As a transiting super-Earth orbiting a bright star, this planet would make an attractive candidate for additional observations, including studies of its atmospheric properties. We present and analyze follow-up photometric observations of the HD 97658 system acquired with the Microvariability and Oscillations of STars space telescope. Our results show no transit with the depth and ephemeris reported in the announcement paper. For the same ephemeris, we rule out transits for a planet with radius larger than 2.09 R⊕, corresponding …

The Relationship Between Γ Cassiopeiae’S X-Ray Emission And Its Circumstellar Environment Ii. Geometry And Kinematics Of The Disk From Mirc And Vega Instruments On The Chara Array, Philippe Stee, O. Delaa, John D. Monnier, Anthony Meilland, Karine Perraut, Denis Mourard, Xiao Che, Gail H. Schaefer, Ettore Pedretti, Myron A. Smith, Raimundo Lopes De Oliveira, Christian Motch, Gregory W. Henry, Noel D. Richardson, Karen S. Bjorkman, R. Bücke, E. Pollmann, Juan Zorec, Douglas R. Gies, Theo A. Ten Brummelaar, Harold A. Mcalister, Nils H. Turner, Judit Sturmann, Laszlo Sturmann, Stephen T. Ridgway

Information Systems and Engineering Management Research Publications

Context.γ Cas is thought to be the prototype of classical Be stars and is the most studied object among this group. However, as for all Be stars, the origin and the physics of its circumstellar disk responsible for the observed near IR-excess, emission lines, and peculiar X-ray emission is still being debated.

Aims. We constrain the geometry and kinematics of its circumstellar disk from the highest spatial resolution ever achieved on this star. This investigation is a part of a large multi-technique observing campaign to obtain the most complete picture of γ Cas which emphasizes the relation of the …

The Lick–Carnegie Survey: A New Two-Planet System Around The Star Hd 207832, Nader Haghighipour, R. Paul Butler, Eugenio J. Rivera, Gregory W. Henry, Steve Vogt

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Keck/HIRES precision radial velocities of HD 207832 indicate the presence of two Jovian-type planetary companions in Keplerian orbits around this G star. The planets have minimum masses of Msin i = 0.56 MJup and 0.73 MJup, with orbital periods of ∼162 and ∼1156 days, and eccentricities of 0.13 and 0.27, respectively. Strömgren b and y photometry reveals a clear stellar rotation signature of the host star with a period of 17.8 days, well separated from the period of the radial velocity variations, reinforcing their Keplerian origin. The values of the semimajor axes of the planets suggest that these objects have …

Spectro-Interferometric Observations Of Classical Nova V458 Vul 2007, Samira Rajabi, Matthew W. Muterspaugh, Benjamin F. Lane, Martin M. Sirk, Stanley Browne, Askari Ghasempour, Samuel P. Halverson, John G. Kelly, Michael Williamson

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We used the Palomar Testbed Interferometer (PTI) to resolve 2.2 μm emission from the classical nova V458 Vul 2007 over the course of several days following its discovery on 2007 August 8.54 UT. We also obtained K-band photometric data and spectra of the nova during the early days of the outburst. We also used photometric measurements from the AAVSO database. This is a unique data set offering a three-technique approach: high-resolution imaging, spectroscopy, and photometry. Our analysis shows that the nova ejecta can be modeled as an inclined disk at low inclination, i.e., low ellipticity which is consistent with the …

Confronting A Solar Irradiance Reconstruction With Solar And Stellar Data, Philip G. Judge, G. Wesley Lockwood, Richard R. Radick, Gregory W. Henry, Alexander I. Shapiro, Werner Schmutz, Charles Lindsey

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Context. A recent paper by Shapiro and colleagues (2011, A&A, 529, A67) reconstructs spectral and total irradiance variations of the Sun during the holocene.

Aims. In this note, we comment on why their methodology leads to large (0.5%) variations in the solar TSI on century-long time scales, in stark contrast to other reconstructions which have ≲ 0.1% variations.

Methods. We examine the amplitude of the irradiance variations from the point of view of both solar and stellar data.

Results. Shapiro et al.’s large amplitudes arise from differences between the irradiances computed from models A and C of Fontenla and colleagues, …

Absolute Properties Of The Eclipsing Binary Star V335 Serpentis, Claud H. Sandberg Lacy, Francis C. Fekel, Antonio Claret

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V335 Ser is now known to be an eccentric double-lined A1+A3 binary star with fairly deep (0.5 mag) partial eclipses. Previous studies of the system are improved with 7456 differential photometric observations from the URSA WebScope and 5666 from the NFO WebScope, and 67 high-resolution spectroscopic observations from the Tennessee State University 2 m automatic spectroscopic telescope. From dates of minima, the apsidal period is about 880 years. Accurate (better than 2%) masses and radii are determined from analysis of the two new light curves and the radial velocity curve. Theoretical models match the absolute properties of the stars at …

The Hd 192263 System: Planetary Orbital Period And Stellar Variability Disentangled, Diana Dragomir, Stephen R. Kane, Gregory W. Henry, David R. Ciardi, Debra A. Fischer, Andrew W. Howard, Eric L. N. Jensen, Gregory Laughlin, Suvrath Mahadevan, Jaymie M. Matthews, Genady Pilyavsky, Kaspar Von Braun, Sharon X. Wang, Jason T. Wright

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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. …

3.6 And 4.5 Μm Phase Curves And Evidence For Non-Equilibrium Chemistry In The Atmosphere Of Extrasolar Planet Hd 189733b, Heather A. Knutson, Nikole K. Lewis, Jonathan J. Fortney, Adam Burrows, Adam P. Showman, Nicolas B. Cowan, Eric Agol, Suzanne Aigrain, David Charbonneau, Drake Deming, Jean-Michel Désert, Gregory W. Henry, Jonathan Langton, Gregory Laughlin

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We present new, full-orbit observations of the infrared phase variations of the canonical hot Jupiter HD 189733b obtained in the 3.6 and 4.5 μm bands using the Spitzer Space Telescope. When combined with previous phase curve observations at 8.0 and 24 μm, these data allow us to characterize the exoplanet's emission spectrum as a function of planetary longitude and to search for local variations in its vertical thermal profile and atmospheric composition. We utilize an improved method for removing the effects of intrapixel sensitivity variations and robustly extracting phase curve signals from these data, and we calculate our best-fit parameters …

Spot Activity Of Lq Hydra From Photometry Between 1988 And 2011, Jyri J. Lehtinen, Lauri Jetsu, Thomas Hackman, Perttu Kajatkari, Gregory W. Henry

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Aims. We investigate the spot activity of the young magnetically active main sequence star LQ Hya. Our aims are to identify possible active longitudes, estimate the differential rotation, and study long and short term changes in the activity.

Methods. Our analysis is based on 24 years of Johnson V-band photometry of LQ Hya obtained with the T3 0.4 m Automated Telescope at the Fairborn Observatory. We use the previously published continuous period search (CPS) method to model the evolution of the light curve of LQ Hya. The CPS fits a Fourier series model to short overlapping subsets …

Absolute Properties Of The Eclipsing Binary Star Bf Draconis, Claud H. Sandberg Lacy, Guillermo Torres, Francis C. Fekel, Jeffrey A. Sabby, Antonio Claret

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BF Dra is now known to be an eccentric double-lined F6+F6 binary star with relatively deep (0.7 mag) partial eclipses. Previous studies of the system are improved with 7494 differential photometric observations from the URSA WebScope and 9700 from the NFO WebScope, 106 high-resolution spectroscopic observations from the Tennessee State University 2 m automatic spectroscopic telescope and the 1 m coudé-feed spectrometer at Kitt Peak National Observatory, and 31 accurate radial velocities from the CfA. Very accurate (better than 0.6%) masses and radii are determined from analysis of the two new light curves and four radial velocity curves. Theoretical models …

Probing The Haze In The Atmosphere Of Hd 189733b With Hubble Space Telescope/Wfc3 Transmission Spectroscopy, Neale P. Gibson, Suzanne Aigrain, Frederic Pont, David K. Sing, Jean-Michel Désert, Thomas M. Evans, Gregory W. Henry, Nawal Husnoo, Heather Knutson

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We present Hubble Space Telescope near-infrared transmission spectroscopy of the transiting exoplanet HD 189733b, using the Wide Field Camera 3 (WFC3). This consists of time series spectra of two transits, used to measure the wavelength dependence of the planetary radius. These observations aim to test whether the Rayleigh scattering haze detected at optical wavelengths extends into the near-infrared, or if it becomes transparent leaving molecular features to dominate the transmission spectrum. Due to saturation and non-linearity affecting the brightest (central) pixels of the spectrum, light curves were extracted from the blue and red ends of the spectra only, corresponding to …

The Relationship Between Γ Cassiopeiae’S X-Ray Emission And Its Circumstellar Environment, Myron A. Smith, Raimundo Lopes De Oliveira, Christian Motch, Gregory W. Henry, Noel D. Richardson, Karen S. Bjorkman, Philippe Stee, Denis Mourard, John D. Monnier, Xiao Che, R. Bücke, E. Pollmann, Douglas R. Gies, Gail Schaefer, Theo A. Ten Brummelaar, Harold Mcalister, Nils H. Turner, Judit Sturmann, Laszlo Sturmann, Stephen T. Ridgway

Information Systems and Engineering Management Research Publications

γ Cas is the prototypical classical Be star and is recently best known for its variable hard X-ray emission. To elucidate the reasons for this emission, we mounted a multiwavelength campaign in 2010 centered around four XMM-Newton observations. The observational techniques included long baseline optical interferometry (LBOI) from two instruments at CHARA, photometry carried out by an automated photometric telescope and Hα observations. Because γ Cas is also known to be in a binary, we measured radial velocities from the Hα line and redetermined its period as 203.55 ± 0.20 days and its eccentricity as near zero. The LBOI observations …

Third Component Search And Abundances Of The Very Dusty Short-Period Binary Bd +20°307, Francis C. Fekel, Maria J. Cordero, Raphael Galicher, Benjamin Zuckerman, Carl Melis, Alycia J. Weinberger

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We have obtained near-infrared adaptive optics imaging and collected additional radial velocity observations to search for a third component in the extremely dusty short-period binary system BD +20°307. Our image shows no evidence for a third component at separations greater than 19 AU. Our four seasons of radial velocities have a constant center-of-mass velocity and are consistent with the systemic velocities determined at two earlier epochs. Thus, the radial velocities also provide no support for a third component. Unfortunately, the separation domains covered by our imaging and radial velocity results do not overlap. Thus, we examined the parameters for possible …

Asteroseismology Of The Nearby Sn-Ii Progenitor: Rigel. I. The Most High-Precision Photometry And Radial Velocity Monitoring, Ehsan Moravveji, Edward F. Guinan, Matt Shultz, Michael H. Williamson, Andres Moya

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Rigel (β Ori, B8 Ia) is a nearby blue supergiant displaying α Cyg type variability, and is one of the nearest Type II supernova progenitors. As such it is an excellent test bed to study the internal structure of pre-core-collapse stars. In this study, for the first time, we present 28 days of high-precision MOST photometry and over six years of spectroscopic monitoring. We report 19 significant pulsation modes of signal-to-noise ratio, S/N ≳ 4.6 from radial velocities, with variability timescales ranging from 1.21 to 74.7 days, which are associated with high-order low-degree gravity modes. While the radial velocity variations …

A High-Eccentricity Component In The Double-Planet System Around Hd 163607 And A Planet Around Hd 164509*, Matthew J. Giguere, Debra A. Fischer, Andrew W. Howard, John A. Johnson, Gregory W. Henry, Jason T. Wright, Geoffrey W. Marcy, Howard Isaacson, Fengji Hou, Julien Spronck

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We report the detection of three new exoplanets from Keck Observatory. HD 163607 is a metal-rich G5IV star with two planets. The inner planet has an observed orbital period of 75.29 ± 0.02 days, a semi-amplitude of 51.1 ± 1.4 m s−1, an eccentricity of 0.73 ± 0.02, and a derived minimum mass of MPsin i = 0.77 ± 0.02 MJup. This is the largest eccentricity of any known planet in a multi-planet system. The argument of periastron passage is 78.7 ± 2fdg0; consequently, the planet's closest approach to its parent star is very near the line of sight, leading …

A Search For The Transit Of Hd 168443b: Improved Orbital Parameters And Photometry, Genady Pilyavsky, Suvrath Mahadevan, Stephen R. Kane, Andrew W. Howard, David R. Ciardi, Chris De Pree, Diana Dragomir, Debra A. Fischer, Gregory W. Henry, Eric L. N. Jensen, Gregory Laughlin

Information Systems and Engineering Management Research Publications

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 HD 168443 a candidate for our ongoing Transit Ephemeris Refinement and Monitoring Survey. Using additional radial velocities from Keck High Resolution Echelle Spectrometer, we refined the …

Retired A Stars And Their Companions. Vii. 18 New Jovian Planets, John Asher Johnson, Christian Clanton, Andrew W. Howard, Brendan P. Bowler, Gregory W. Henry, Geoffrey W. Marcy, Justin R. Crepp, Michael Endl, William D. Cochran, Phillip J. Macqueen, Jason T. Wright, Howard Isaacson

Information Systems and Engineering Management Research Publications

We report the detection of 18 Jovian planets discovered as part of our Doppler survey of subgiant stars at Keck Observatory, with follow-up Doppler and photometric observations made at McDonald and Fairborn Observatories, respectively. The host stars have masses 0.927 ⩽ M⋆/M☉ ⩽ 1.95, radii 2.5 ⩽ R⋆/R☉ ⩽ 8.7, and metallicities −0.46 ⩽ [Fe/H] ⩽+0.30. The planets have minimum masses 0.9 MJup ⩽ MPsin i ≲ 13 MJup and semimajor axes a ⩾ 0.76 AU. These detections represent a 50% increase in the number of planets known to orbit stars more massive than 1.5 M☉ and provide valuable additional …

Absolute Properties Of The Highly Eccentric, Solar-Type Eclipsing Binary Hd 74057, James R. Sowell, Gregory W. Henry, Francis C. Fekel

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We have obtained Strömgren b and y differential photometric observations of the solar-type eclipsing binary HD 74057 plus follow-up high-resolution, red wavelength spectroscopic observations. The system has an orbital period of 31.2198 days, a high eccentricity of 0.47, and is seen almost exactly edge on with an inclination of 89fdg8. The two main-sequence G0 stars are nearly identical in all physical characteristics. We used the Wilson–Devinney program to obtain a simultaneous solution of our photometric and spectroscopic observations. The resulting masses of the components are M1 = 1.138 ± 0.003 M☉ and M2 = 1.131 ± 0.003 M☉, and the …

The Stellar-Activity–Rotation Relationship And The Evolution Of Stellar Dynamos, Nicholas J. Wright, Jeremy J. Drake, Eric E. Mamajek, Gregory W. Henry

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We present a sample of 824 solar and late-type stars with X-ray luminosities and rotation periods. This is used to study the relationship between rotation and stellar activity and derive a new estimate of the convective turnover time. From an unbiased subset of this sample the power-law slope of the unsaturated regime, LX/Lbol∝Roβ, is fit as β = −2.70 ± 0.13. This is inconsistent with the canonical β = −2 slope to a confidence of 5σ, and argues for an additional term in the dynamo number equation. From a simple scaling analysis this implies ΔΩ/Ω∝Ω0.7, i.e., the differential rotation of …

Absolute Properties Of The Eclipsing Binary Star Hy Virginis, Claud H. Sandberg Lacy, Francis C. Fekel

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HY Vir is found to be a double-lined F0m+F5 binary star with relatively shallow (0.3 mag) partial eclipses. Previous studies of the system are improved with 7509 differential photometric observations from the URSA WebScope and 8862 from the NFO WebScope, and 68 high-resolution spectroscopic observations from the Tennessee State University 2 m automatic spectroscopic telescope, and the 1 m coudé-feed spectrometer at Kitt Peak National Observatory. Very accurate (better than 0.5%) masses and radii are determined from analysis of the new light curves and radial velocity curves. Theoretical models match the absolute properties of the stars at an age of …

Surprising Variations In The Rotation Of The Chemically Peculiar Stars Cu Virginis And V901 Orionis, Zdeněk Mikulášek, Jiří Krtička, Gregory W. Henry, Jan Janík, Juraj Zverko, Jozef Žižňovský, Miloslav Zejda, Jiri Liška, Pavel Zvěřina, D. O. Kudrjavtsev, Iosif I. Romanyuk, N. A. Sokolov, Theresa Lüftinger, Corrado Trigilio, Coralie Neiner, S. N. De Villiers

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Context. The majority of magnetic chemically peculiar (mCP) stars exhibit periodic light, radio, spectroscopic and spectropolarimetric variations that can be adequately explained by the model of a rigidly rotating main-sequence star with persistent surface structures. CU Vir and V901 Ori belong among these few mCP stars whose rotation periods vary on timescales of decades.

Aims. We aim to study the stability of the periods in CU Vir and V901 Ori using all accessible observational data containing phase information.

Methods. We collected all available relevant archived observations supplemented with our new measurements of these stars and analysed the period variations of …

The Real Orbital Period Of The Double-Lined Spectroscopic Binary Hd 31738, Francis C. Fekel, Roger F. Griffin

Information Systems and Engineering Management Research Publications

No abstract provided.

Hubble Space Telescope Transmission Spectroscopy Of The Exoplanet Hd 189733b: High-Altitude Atmospheric Haze In The Optical And Near-Ultraviolet With Stis, David K. Sing, Frederic Pont, Suzanne Aigrain, David Charbonneau, Jean-Michel Désert, Neale P. Gibson, Ronald Gilliland, Wolfgang Hayek, Gregory W. Henry, Heather Knutson, Alain Lecavelier Des Etangs, Tsevi Mazeh, Avi Shporer

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We present Hubble Space Telescope (HST) optical and near-ultraviolet transmission spectra of the transiting hot Jupiter HD 189733b, taken with the repaired Space Telescope Imaging Spectrograph (STIS) instrument. The resulting spectra cover the range 2900–5700 Å and reach per exposure signal-to-noise ratio levels greater than 11 000 within a 500-Å bandwidth. We used time series spectra obtained during two transit events to determine the wavelength dependence of the planetary radius and measure the exoplanet’s atmospheric transmission spectrum for the first time over this wavelength range. Our measurements, in conjunction with existing HST spectra, now provide a broad-band transmission spectrum covering …

New Precision Orbits Of Bright Double-Lined Spectroscopic Binaries. Vii. 47 Andromedae, 38 Cassiopeiae, And Hr 8467, Francis C. Fekel, Jocelyn Tomkin, Michael H. Williamson, Dimitri Pourbaix

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Improved orbital elements for three double-lined spectroscopic binaries, 47 And, 38 Cas, and HR 8467, have been determined with extensive new radial velocities. For 38 Cas lines of the secondary have been detected for the first time. Given the orbital periods for these systems of 35.3682, 134.130, and 42.3813 days, respectively, it is not surprising that all three have either moderate or relatively high eccentricities. The orbital dimensions (a1sin i and a2sin i) and minimum masses (m1sin 3i and m2sin 3i) have accuracies of 0.5% or better. An astrometric orbit for 38 Cas, which was recomputed with Hipparcos astrometry and …

A Volume-Limited Photometric Survey Of 114 Γ Doradus Candidates, Gregory W. Henry, Francis C. Fekel, Stephen M. Henry

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We have carried out a photometric survey of a complete, volume-limited sample of γ Doradus candidates. The sample was extracted from the Hipparcos catalog and consists of 114 stars with colors and absolute magnitudes within the range of known γ Doradus stars and that also lie within a specified volume of 266,600 pc3. We devoted one year of observing time with our T12 0.8 m automatic photometric telescope to acquire nightly observations of the complete sample of stars. From these survey observations, we identify 37 stars with intrinsic variability of 0.002 mag or more. Of these 37 variables, 8 have …

Revised Orbit And Transit Exclusion For Hd 114762b, Stephen R. Kane, Gregory W. Henry, Diana Dragomir, Debra A. Fischer, Andrew W. Howard, Xuesong Wang, Jason T. Wright

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Transiting planets around bright stars have allowed the detailed follow-up and characterization of exoplanets, such as the study of exoplanetary atmospheres. The Transit Ephemeris Refinement and Monitoring Survey is refining the orbits of the known exoplanets to confirm or rule out both transit signatures and the presence of additional companions. Here we present results for the companion orbiting HD 114762 in an eccentric 84 day orbit. Radial velocity analysis performed on 19 years of Lick Observatory data constrain the uncertainty in the predicted time of mid-transit to ∼5 hr, which is less than the predicted one-half day transit duration. We …

A Spitzer Transmission Spectrum For The Exoplanet Gj 436b, Evidence For Stellar Variability, And Constraints On Dayside Flux Variations, Heather Knutson, Nikku Madhusudhan, Nicolas B. Cowan, Jessie L. Christiansen, Eric Agol, Drake Deming, Jean-Michel Désert, David Charbonneau, Gregory W. Henry, Derek Homeier, Jonathan Langton, Gregory Laughlin, Sara Seager

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In this paper, we describe a uniform analysis of eight transits and eleven secondary eclipses of the extrasolar planet GJ 436b obtained in the 3.6, 4.5, and 8.0 μm bands using the IRAC instrument on the Spitzer Space Telescope between UT 2007 June 29 and UT 2009 February 4. We find that the best-fit transit depths for visits in the same bandpass can vary by as much as 8% of the total (4.7σ significance) from one epoch to the next. Although we cannot entirely rule out residual detector effects or a time-varying, high-altitude cloud layer in the planet's atmosphere as …

Improved Orbital Parameters And Transit Monitoring For Hd 156846b, Stephen R. Kane, Andrew W. Howard, Genady Pilyavsky, Suvrath Mahadevan, Gregory W. Henry, Kaspar Von Braun, David R. Ciardi, Diana Dragomir, Debra A. Fischer, Eric L. N. Jensen, Gregory Laughlin, Solange V. Ramirez, Jason T. Wright

Information Systems and Engineering Management Research Publications

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 …

New Precision Orbits Of Bright Double-Lined Spectroscopic Binaries. Vi. Hd 24623 And V923 Scorpii, Francis C. Fekel, Michael H. Williamson, Gregory W. Henry

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Using new radial velocities obtained at KPNO and Fairborn Observatory, we have determined improved spectroscopic orbits for two double-lined F-type binaries, HD 24623 and V923 Sco. The orbital periods are 19.66304 and 34.8386 days, respectively, so it is not surprising that their orbits have relatively high eccentricities of nearly 0.5. The orbital dimensions (a1sin i and a2sin i) and minimum masses (m1sin 3i and m2sin 3i) have accuracies of 0.2% or better. Extensive photometry of HD 24623 with the T4 0.75 m automatic photometric telescope at Fairborn Observatory shows no evidence of eclipses. Instead, a very weak reflection effect is …