A photometric investigation of the fields of two short-period Cepheids in Cygnus

xi, 95 leaves : ill. ; 28 cm.Includes abstract.Includes bibliographical references (leaves 90-93).Photoelectric, photographic and CCD photometry, as well as spectroscopic observations and proper motion data for stars in the fields of the short-period galactic Cepheids V1726 Cygni and SU Cygni are presented and analyzed. The existence of a sparsely populated cluster associated with V1726 Cyg has been confirmed, and a new, loose stellar group has been found in the vicinity of SU Cyg. The newly obtained distance modulus for C2128+488 (Anon. Platais), the cluster associated with V1726 Cyg, is V[subscript 0] - M[subscript V] = 10.98 [plus or minus] 0.02, corresponding to a distance of 1568 [plus or minus] 13 pc. The spatial coincidence and the close match of the radial velocity, proper motion and age of V1726 Cyg with those of the cluster indicate a high probability of cluster membership for the Cepheid. The space reddening of V1726 Cyg, found from two neighbouring stars, is E[subscript B-V] = 0.43 [plus or minus] 0.02 and its luminosity as a cluster member is = -3.42 [plus or minus] 0.07. The newly found group of stars in the vicinity of SU Cyg has a distance modulus of V[subscript 0] - M[subscript V] = 10.98 [plus or minus] 0.02 (d = 1040 pc). It contains mostly early A to late F-type stars, with a few early B-type stars whose membership is more uncertain. A reddening of E [subscript B-V] = 0.16 has been determined for SU Cyg from a nearby (20") star having an accurate MK spectral type. The probable discovery of a new planetary nebula, located about 3' south of SU Cyg, and a possible new cluster 17' west of SU Cyg, are also reported. (Abstract shortened by UMI.

Galactic clusters with associated Cepheid variables. IV. C2128+488 (Anon. Platais) and V1726 Cygni

Publisher's version/PDFNew photoelectric UBV photometry of 32 stars, photographic UBV photometry of 120 stars, and spectroscopic observations of 8 stars are presented for C 2128+488 (Anon. Platais), the cluster associated with the 4[d over dot]237 s-Cepheid V1726 Cygni. The resulting photometry, spectral classifications, and radial velocities are used with spectroscopic and proper motion data previously published by Platais and others for the Cepheid and other stars in this field in a detailed cluster analysis. The newly obtained cluster distance modulus is V[subscript 0]-M[subscript V] = 10.98 [plus or minus] 0.02 s.e. (d = 1568 [plus or minus] 13 pc), and a value of R = A[subscript V]/E[subscript B-V = 3.07 [plus or minus] 0.27 s.e. is found to describe the dust extinction in the field. A space reddening of E[subscript B-V] = 0.43 [plus or minus] 0.02 is derived for V1726 Cyg from two late B-type companions which bracket the Cepheid, as well as from the reddenings of other stars in the field. Its resulting luminosity as a probable cluster member is [angled bracket]M[subscript V][angled bracket] = -3.42 [plus or minus] 0.07. A cluster radial velocity of -15.4 [plus or minus] 0.2 km s[superscript -1] and a cluster turnoff point at spectral type B7 are both consistent with the likely membership of V1726 Cyg, as are the available proper motion data. The small amplitude, sinusoidal light curve, and location of V1726 Cyg on the blue edge of the Cepheid instability strip are consistent with the properties expected for overtone pulsation, although such a possibility appears to imply an unrealistically small value ([Beta]=0.5 [plus or minus] 0.2) for the color coefficient in the PLC relation. A more reasonable value of [Beta]=2.1 [plus or minus] 0.2 is derived for the color term applicable to galactic cluster Cepheids in this program when V1726 Cyg is assumed to be pulsating in the fundamental mode

Astrophysical False Positives Encountered in Wide-Field Transit Searches

Wide-field photometric transit surveys for Jupiter-sized planets are inundated by astrophysical false positives, namely systems that contain an eclipsing binary and mimic the desired photometric signature. We discuss several examples of such false alarms. These systems were initially identified as candidates by the PSST instrument at Lowell Observatory. For three of the examples, we present follow-up spectroscopy that demonstrates that these systems consist of (1) an M-dwarf in eclipse in front of a larger star, (2) two main-sequence stars presenting grazing-incidence eclipses, and (3) the blend of an eclipsing binary with the light of a third, brighter star. For an additional candidate, we present multi-color follow-up photometry during a subsequent time of eclipse, which reveals that this candidate consists of a blend of an eclipsing binary and a physically unassociated star. We discuss a couple indicators from publicly-available catalogs that can be used to identify which candidates are likely giant stars, a large source of the contaminants in such surveys.Comment: 10 pages, 9 figures, to appear in AIP Conf Proc: The Search for Other Worlds, eds. S. S. Holt & D. Demin

Identification, classifications, and absolute properties of 773 eclipsing binaries found in the Trans-Atlantic Exoplanet Survey

In recent years, we have witnessed an explosion of photometric time-series data, collected for the purpose of finding a small number of rare sources, such as transiting extrasolar planets and gravitational microlenses. Once combed, these data are often set aside, and are not further searched for the many other variable sources that they undoubtedly contain. To this end, we describe a pipeline that is designed to systematically analyze such data, while requiring minimal user interaction. We ran our pipeline on a subset of the Trans-Atlantic Exoplanet Survey dataset, and used it to identify and model 773 eclipsing binary systems. For each system we conducted a joint analysis of its light curve, colors, and theoretical isochrones. This analysis provided us with estimates of the binary's absolute physical properties, including the masses and ages of their stellar components, as well as their physical separations and distances. We identified three types of eclipsing binaries that are of particular interest and merit further observations. The first category includes 11 low-mass candidates, which may assist current efforts to explain the discrepancies between the observation and the models of stars at the bottom of the main sequence. The other two categories include 34 binaries with eccentric orbits, and 20 binaries with abnormal light curves. Finally, this uniform catalog enabled us to identify a number of relations that provide further constraints on binary population models and tidal circularization theory

Detection of a Temperature Inversion in the Broadband Infrared Emission Spectrum of TrES-4

We estimate the strength of the bandpass-integrated thermal emission from the extrasolar planet TrES-4 at 3.6, 4.5, 5.8, and 8.0 micron using the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. We find relative eclipse depths of 0.137 +/- 0.011%, 0.148 +/- 0.016%, 0.261 +/- 0.059%, and 0.318 +/- 0.044% in these four bandpasses, respectively. We also place a 2 sigma upper limit of 0.37% on the depth of the secondary eclipse in the 16 micron IRS peak-up array. These eclipse depths reveal that TrES-4 has an emission spectrum similar to that of HD 209458b, which requires the presence of water emission bands created by an thermal inversion layer high in the atmosphere in order to explain the observed features. TrES-4 receives more radiation from its star than HD 209458b and has a correspondingly higher effective temperature, therefore the presence of a temperature inversion in this planet's atmosphere lends support to the idea that inversions might be correlated with the irradiance received by the planet. We find no evidence for any offset in the timing of the secondary eclipse, and place a 3 sigma upper limit of |ecos(omega)|<0.0058 where e is the planet's orbital eccentricity and omega is the argument of pericenter. From this we conclude that tidal heating from ongoing orbital circulatization is unlikely to be the explanation for TrES-4's inflated radius.Comment: 10 pages in emulateapj format, 7 figures (some in color), accepted for publication in Ap

Absolute properties of the low-mass eclipsing binary CM Draconis

Spectroscopic and eclipsing binary systems offer the best means for determining accurate physical properties of stars, including their masses and radii. The data available for low-mass stars have yielded firm evidence that stellar structure models predict smaller radii and higher effective temperatures than observed, but the number of systems with detailed analyses is still small. In this paper we present a complete reanalysis of one of such eclipsing systems, CM Dra, composed of two dM4.5 stars. New and existing light curves as well as a radial velocity curve are modeled to measure the physical properties of both components. The masses and radii determined for the components of CM Dra are M1=0.2310+/-0.0009 Msun, M2=0.2141+/-0.0010 Msun, R1=0.2534+/-0.0019 Rsun, and R2=0.2396+/-0.0015 Rsun. With relative uncertainties well below the 1% level, these values constitute the most accurate properties to date for fully convective stars. This makes CM Dra a valuable benchmark for testing theoretical models. In comparing our measurements with theory, we confirm the discrepancies reported previously for other low-mass eclipsing binaries. These discrepancies seem likely to be due to the effects of magnetic activity. We find that the orbit of this system is slightly eccentric, and we have made use of eclipse timings spanning three decades to infer the apsidal motion and other related properties.Comment: 19 pages, 9 figures. Accepted for publication in Ap

The Broadband Infrared Emission Spectrum of the Exoplanet TrES-3

We use the Spitzer Space Telescope to estimate the dayside thermal emission of the exoplanet TrES-3 integrated in the 3.6, 4.5, 5.8, and 8.0 micron bandpasses of the Infrared Array Camera (IRAC) instrument. We observe two secondary eclipses and find relative eclipse depths of 0.00346 +/- 0.00035, 0.00372 +/- 0.00054, 0.00449 +/- 0.00097, and 0.00475 +/- 0.00046, respectively in the 4 IRAC bandpasses. We combine our results with the earlier K band measurement of De Mooij et al. (2009), and compare them with models of the planetary emission. We find that the planet does not require the presence of an inversion layer in the high atmosphere. This is the first very strongly irradiated planet that does not have a temperature inversion, which indicates that stellar or planetary characteristics other than temperature have an important impact on temperature inversion. De Mooij & Snellen (2009) also detected a possible slight offset in the timing of the secondary eclipse in K band. However, based on our 4 Spitzer channels, we place a 3sigma upper limit of |ecos(w)| < 0.0056 where e is the planets orbital eccentricity and w is the longitude of the periastron. This result strongly indicates that the orbit is circular, as expected from tidal circularization theory.Comment: Accepted by Ap