Exoplanets or extrasolar planets are among the most fascinating phenomena in astrophysics today. Their detection and followup has established itself as a major field of research that will be a major focus for decades into the future. These planetary systems discovered outside our solar system are not observed directly but detected principally by high resolution spectroscopy enabling the measurement of the wobble they induce upon their parent sun. Another innovative technique called the transit method permits the detection of exoplanets whose orbit carries them in fornt of their star from our terrestrial point of view. This is accomplished by measuring the periodic dimming observed in the light from the parent star reaching us. These objects are aptly described as Transiting Exoplanets ( TEP's ) or Transiting Hot Jupiters ( THJ's ) as they orbit their stars at distances much closer than the orbit of Mercury around our Sun, making a complete revolution around their stars in just a few ( Earth) days and resemble objects comparable to our own solar system’s giant planet Jupiter in mass and size. Transits are relatively easy to observe with commonly available amateur equipment and are the focus of research efforts conducted at Volunteer Observatory. I have co-discovered two exoplanets, XO-2b and XO-3b and timely observations of the WASP-1b system were utilized to determine many of the planet's physical parameters that were published in the scientific discovery paper for that system.Additionaly, I routinely conduct follow up observations of THJ systems in search for transit timing variations which would permit the inference of multiple planets in these exo-solar systems including the possibility of exo-earths.
 
 

Exoplanet observations involve differential photometry of a star field. This entails a series of  images taken over the time span of several hours during an expected transit event. Baselines immediately before and after the transit are also acquired. The objective is to measure the ratio of the exoplanet star's intensity relative to one or more "reference" or comparison stars in the same field of view that do not change in brightness.The relative brightness of the exoplanet star is plotted as magnitude versus time also known as a light curve. The resulting transit profile then can be used to determine many physical parameters of the system. A Jupiter sized exoplanet will produce a 1% drop in brightness of a solar type star's light intensity. With the radius of the star derived from either spectroscopy or its color index it is then possible to secure a precise estimate of the radius of the planet using the change in flux observed during a transit.
 
 

In June 2006 at the invitation of Dr. Peter Mc Cullough, XO's  principal investigator, I joined the XO project as a member of the extended team (ET).The ET are a small number of serious amateur and professional astronomers that conduct follow up observations of potential exoplanet candidates identified by Dr. McCullough and his colleagues. These candidates are identified from data generated by the XO constellation located atop the 3054 meter summit of Haleakala on Maui, Hawaii. Data generated by XO and the ET follow up observations then are used to determine which stars are suitable for further analysis with spectroscopy using larger ground based telescopes such as the 11 meter Hobby Ebberly Telescope ( HET ) and 2.7 meter Harlan J Smith (HJS) telescope at McDonald Observatory. The ET are especially helpful in revealing false positives detected in the XO photometry from Maui such as  blend scenarios where background stars contaminate an unknown eclipsing binary system in the XO photometer annulus. Many new EB's are scooped up in this survey.  Needless to say- This exciting project and has been given first priority.Volunteer Observatory operates autonomously gathering data on available XO candidates every clear night.
 
 

Authors: Christopher J. Burke, P. R. McCullough, Jeff A. Valenti, Christopher M. Johns-Krull, Kenneth A. Janes, J. N. Heasley, F. J. Summers, J. E. Stys, R. Bissinger, Michael L. Fleenor, Cindy N. Foote, Enrique Garcia-Melendo, Bruce L. Gary, P. J. Howell, F. Mallia, G. Masi, B. Taylor, T. Vanmunster
Comments: 17 pages, 14 Figures, Submitted to ApJ

ABSTRACT
We report on a V=11.2 early K dwarf, XO-2 (GSC 03413-00005), that hosts a Rp=0.973+0.03/-0.008 Rjup, Mp=0.57+/-0.06 Mjup transiting extrasolar planet, XO-2b, with an orbital period of 2.615838+/-0.000008 days. XO-2 has high metallicity, [Fe/H]=0.45+/-0.02, high proper motion, mu_tot=157 mas/yr, and has a common proper motion stellar companion with 31" separation. The two stars are nearly identical twins, with very similar spectra and apparent magnitudes. Due to the high metallicity, these early K dwarf stars have a mass and radius close to solar, Ms=0.98+/-0.02 Msolar and Rs=0.964+0.02/-0.009 Rsolar. The high proper motion of XO-2 results from an eccentric orbit (Galactic pericenter, Rper<4 kpc) well confined to the Galactic disk (Zmax~100 pc). In addition, the phase space position of XO-2 is near the Hercules dynamical stream, which points to an origin of XO-2 in the metal-rich, inner Thin Disk and subsequent dynamical scattering into the solar neighborhood. We describe an efficient Markov Chain Monte Carlo algorithm for calculating the Bayesian posterior probability of the system parameters from a transit light curve. System parameters and confidence intervals from a chi^2 minimization are also provided.

I am pleased to announce my collaboration with the Wide Angle Search for Planets  (WASP) and our resulting discovery paper!

Authors: A. Collier Cameron, F. Bouchy, G. Hebrard, P. Maxted, D. Pollacco, F. Pont, I. Skillen, B. Smalley, R. A. Street, R.G. West, D.M. Wilson, S. Aigrain, D.J. Christian, W.I. Clarkson, B. Enoch, A. Evans, A. Fitzsimmons, M. Fleenor, M. Gillon, C.A. Haswell, L. Hebb, C. Hellier, S.T. Hodgkin, K. Horne, J. Irwin, S.R. Kane, F.P. Keenan, B. Loeillet, T.A. Lister, M. Mayor, C. Moutou, A.J. Norton, J. Osborne, N. Parley, D. Queloz, R. Ryans, A.H.M.J. Triaud, S. Udry, P.J. Wheatley

ABSTRACT
We have detected low-amplitude radial-velocity variations in two stars, USNO-B1.0 1219-0005465 (GSC 02265-00107 = WASP-1) and USNO-B1.0 0964-0543604 (GSC 00522-01199 = WASP-2). Both stars were identified as being likely host stars of transiting exoplanets in the 2004 SuperWASP wide-field transit survey. Using the newly-commissioned radial-velocity spectrograph SOPHIE at the Observatoire de Haute-Provence, we found that both objects exhibit reflex orbital radial-velocity variations with amplitudes characteristic of planetary-mass companions and in-phase with the photometric orbits. Line-bisector studies rule out faint blended binaries as the cause of either the radial-velocity variations or the transits. We perform preliminary spectral analyses of the host stars, which together with their radial-velocity variations and fits to the transit light curves, yield estimates of the planetary masses and radii. WASP-1b and WASP-2b have orbital periods of 2.52 and 2.15 days respectively. Given mass estimates for their F7V and K1V primaries we derive planet masses 0.80 to 0.98 and 0.81 to 0.95 times that of Jupiter respectively. WASP-1b appears to have an inflated radius of at least 1.33 R_Jup, whereas WASP-2b has a radius in the range 0.65 to 1.26 R_Jup.
 
 

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