A comprehensive study of Kepler phase curves and secondary eclipses -- temperatures and albedos of confirmed Kepler giant planets

We present a comprehensive study of phase curves and secondary eclipses in the Kepler data set using all data from 16 quarters that were available in 2013-2014. Our sample consists of 20 confirmed planets with R_p > 4 R_e ,P < 10d, V_mag < 15. Here we derive their temperatures and albedos, with an eye towards constraining models for the formation and evolution of such planets. Where there was overlap our results confirm parameters derived by previous studies, whereas we present new results for Kepler 1b-8b, 12b-15b, 17b, 40b, 41b, 43b, 44b, 76b, 77b, and 412b derived in a consistent manner. We also present lightcurve analyses for Kepler 91b and Kepler 74b, which both show extra dimmings at times other than from the expected primary and secondary eclipses. Corrected for thermal emission we find most of the massive planets from our sample to be low in albedo (<0.1) with a few having higher albedo (>0.1).Comment: 50 pages, 7 figures - PASP accepte

Resonant two-photon ionization spectroscopy of jet-cooled RuC

Journal ArticleA resonant two-photon ionization study of the jet-cooled RuC molecule has identified the ground state as a 1?+ state arising from the 10?211?25rr42?4 configuration. The 3?i state arising from the 10?211?25rr42?312?1 configuration lies very low in energy, with the 3?3 and 3?2 components lying only 76 and 850 cm-1 above the ground state, respectively. Transitions from the X 1?+, 3?3 , and 3?2 states to the 3II2, 3II1, 3?3, 3?4, 1?3, and 1II1 states arising from the 10?211?25rr42?36rr1 configuration have been observed in the 12 700?18 100 cm-1 range, allowing all of these states to be placed on a common energy scale. The bond length increases as the molecule is electronically excited, from r051.608 ? in the 2?4, X 1?+ state, to 1.635 ? in the 2?312?1, 3? state, to 1.66 ? in the 2?36rr1, 3II and 3? states, to 1.667 ? in the 2?36rr1, 1? and 1.678 ? in the 2?36rr1, 1II state. A related decrease in vibrational frequency with electronic excitation is also observed. Hyperfine splitting is observed in the 2?312?1, 3?3 state for the 99Ru(I55/2)12C and 101Ru(I55/2)12C isotopic combinations. This is analyzed using known atomic hyperfine parameters to show that the 12? orbital is roughly 83% 5sRu in character, a result in good agreement with previous work on the related RhC and CoC molecules

The bond energy of Rh?

Journal ArticleIn a spectroscopic investigation of jet-cooled Rh2 by the resonant two-photon ionization method, an abrupt predissociation threshold is observed in a dense set of vibronic levels at 19 405?4 cm-1. Based on the high density of states expected in the rhodium dimer, the sharp definition of the predissociation threshold that is observed, and the validation of a similar conclusion in the case of V2, it is argued that predissociation occurs as soon as the energy of the separated ground state atoms is exceeded. On this basis the bond energy of Rh2 is assigned as D0(Rh2)=19 405 ?4 cm-1=2.4059?0.0005 eV. This value is compared to the results of other experiments and to theoretical calculations. The bond energy of disilver, D0(Ag2)=1.65?0.03 eV, provides a particularly useful standard of comparison, and suggests that 4d contributions to the bond energy of Rh2 amount to at least 0.76 eV

Resonant two-photon ionization spectroscopy of jet-cooled PdC

Journal ArticleThe first optical investigation of the spectra of diatomic PdC has revealed that the ground state has ?=0+, with a bond length of r0=1.712?. The Hund?s case (a) nature of this state could not be unambiguously determined from the experimental data, but dispersed fluorescence studies to be reported in a separate publication, in combination with a comparison to theoretical calculations, demonstrate that it is the 2?4 12?2, 1?+0+ state, which undergoes spin?orbit mixing with a low-lying 2?4 12?1 6rr1, 3II0+ state. An excited 3?+ state with re=1.754?0.003? (r051.758?0.002?) and ?G1/25794 cm-1 is found at T0=17 867 cm21. Although only the ?=1 component of this state is directly observed, the large hyperfine splitting of this state for the 105Pd 12C isotopomer implies that an unpaired electron occupies an orbital that is primarily of 5s character on Pd. Comparison to ab initio calculations identifies this state as 2?4 12?113?1, 3?+1. To higher wavenumbers a number of transitions to states with ?=1+ have been observed and rotationally analyzed. Two groups of these have been organized into band systems, despite the clear presence of homogeneous perturbations between states with ?=0+ in the region between 22 000 and 26 000 cm-1

Inclined Gas Disks in the Lenticular Seyfert Galaxy NGC 5252

We discuss the morphology and kinematics of the extended gas in the type 2 Seyfert galaxy NGC 5252 based on Hubble Space Telescope (HST) WFPC2 continuum and emission-line images (including a new [O III] λ5007 image) and a ground-based Fabry-Perot (F-P) velocity map of the ionized gas. The fine-scale morphology of the ionized gas in this galaxy's very extended (~40 kpc) ionization bicone consists of a complex network of filamentary strands. The new WFPC2 [O III] image also reveals more detail in the circumnuclear (~3 kpc) gas disk than is seen in the Hα + [N II] image presented previously by Tsvetanov and coworkers. The F-P velocity map shows an obvious antisymmetry of the velocity field of the ionized gas across the nucleus. We conclude that there are three dynamical components to the extended gas in NGC 5252. Two of these components are gas disks aligned with the stellar disk, one rotating with the stars and the other counterrotating. The third component is the circumnuclear gas disk seen in the HST observations and its extension to larger scales; this disk has an inclination of ~40° and a kinematic major axis in P.A. ~ 90°-135°, some 80°-125° from the major axis of the stellar disk. This simple model of two inclined rotating disks, superposed along the line of sight, describes well the seemingly complex kinematics observed in the optical emission lines and the H I 21 cm radio maps. The large misalignment between the second disk and the stellar disk suggests that the gas distribution, and possibly the nuclear activity, in NGC 5252 may have resulted from a galaxy merger event. The absence of significant radial motions, together with the well-defined ionization cones, strongly suggests that the gas is photoionized by a compact nuclear source rather than being ionized in situ by shock waves in a large-scale outflow

The Purple Haze of Eta Carinae: Binary-Induced Variability?

Asymmetric variability in ultraviolet images of the Homunculus obtained with the Advanced Camera for Surveys/High Resolution Camera on the Hubble Space Telescope suggests that Eta Carinae is indeed a binary system. Images obtained before, during, and after the recent ``spectroscopic event'' in 2003.5 show alternating patterns of bright spots and shadows on opposite sides of the star before and after the event, providing a strong geometric argument for an azimuthally-evolving, asymmetric UV radiation field as one might predict in some binary models. The simplest interpretation of these UV images, where excess UV escapes from the secondary star in the direction away from the primary, places the major axis of the eccentric orbit roughly perpendicular to our line of sight, sharing the same equatorial plane as the Homunculus, and with apastron for the hot secondary star oriented toward the southwest of the primary. However, other orbital orientations may be allowed with more complicated geometries. Selective UV illumination of the wind and ejecta may be partly responsible for line profile variations seen in spectra. The brightness asymmetries cannot be explained plausibly with delays due to light travel time alone, so a single-star model would require a seriously asymmetric shell ejection.Comment: 8 pages, fig 1 in color, accepted by ApJ Letter

A Survey of Proper-Motion Stars. XIV. Spectroscopic Binaries among Metal-poor Field Blue Stragglers

We summarize the results from a program of monitoring the radial velocities of 10 metal-poor, high-velocity field stars whose colors are 0.01 to 0.13 mag bluer than main-sequence turnoffs of comparable-metallicity globular clusters. Two of the candidate halo blue stragglers (BD +72 94 and BD +40 1166) show no signs of velocity variability, one (HD 84937) shows only weak signs of variability, one (BD +25 1981) appears to be a very long-period binary, and six (BD -12 2669, HD 97916, HD 106516, BD +51 1817, G66-30, and G202-65) are single-lined spectroscopic binaries, with periods ranging from 167 to 844 days. Velocity coverage for the four candidates without orbital solutions ranges from 15.9 to 19.0 years. The orbital eccentricities are all low, e < 0.30 and e = 0.11. Five of the six binary orbits have very low eccentricities, with e = 0.07. We have reanalyzed the velocity data from Preston & Sneden and have derived orbital solutions similar to theirs for 10 of the spectroscopic binaries among their "blue metal-poor" stars with [Fe/H] ≤ -0.6. We confirm their conclusion that the binary frequency is high; we find 47 ± 10% if we include only the definite binaries with [Fe/H] ≤ -0.6. Our orbital solutions for the seven binaries with periods longer than 20 days all have low eccentricities, with e ≤ 0.26 and e = 0.11. These orbital characteristics are very similar to the Ba II, CH, subgiant CH, and dwarf carbon stars, suggesting that mass transfer has been involved in their formation. Of the five binary stars in our program with published abundances of lithium, all have been found to be deficient (and one in beryllium as well). In contrast, two of the three apparently single stars have published lithium abundances and show no deficiency. The mass functions for the six binaries in our program and seven similar systems studied by Preston & Sneden are consistent with their unseen companions all being white dwarfs with M ≈ 0.55 M and random orbital inclinations. Taking all of our observations and those of others together, we argue that the results are consistent with all field blue stragglers being binary systems with long periods and low eccentricities, the primary stars being deficient in lithium and the secondary stars being normal-mass white dwarfs. All these properties are suggestive of a blue-straggler formation model that involves mass transfer. For six of the 13 stars in the two programs for which s-process elemental abundances are available, no signs of enhancement are discernible, suggesting that the donor star was a first-ascent red giant. For the star with the longest orbital period (1307 days), CS 22956-028, s-process abundance enhancements have been reported. This star may be a precursor to the subgiant CH class, as suggested by Luck & Bond

Spectroscopic Binaries, Velocity Jitter, and Rotation in Field Metal-poor Red Giant and Red Horizontal-Branch Stars

We summarize 2007 radial velocity measurements of 91 metal-poor field red giants. Excluding binary systems with orbital solutions, our coverage averages 13.7 yr per star, with a maximum of 18.0 yr. We report four significant findings. (1) Sixteen stars are found to be spectroscopic binaries, and we present orbital solutions for 14 of them. The spectroscopic binary frequency of the metal-poor red giants, with [Fe/H] ≤ -1.4, for periods less than 6000 days, is 16% ± 4%, which is not significantly different from that of comparable-metallicity field dwarfs, 17% ± 2%. The two CH stars in our program, BD -1°2582 and HD 135148, are both spectroscopic binaries. (2) Velocity jitter is present among about 40% of the giants with MV ≤ -1.4. The two best-observed cases, HD 3008 and BD +22°2411, show pseudoperiodicities of 172 and 186 days, longer than any known long-period variable in metal-poor globular clusters. Photometric variability seen in HD 3008 and three other stars showing velocity jitter hints that starspots are the cause. However, the phasing of the velocity data with the photometry data from Hipparcos is not consistent with a simple starspot model for HD 3008. We argue against orbital motion effects and radial pulsation, so rotational modulation remains the best explanation. The implied rotational velocities for HD 3008 and BD +22°2411, both with MV ≤ -1.4 and R ≈ 50 R⊙, exceed 12 km s-1. (3) Including HD 3008 and BD +22°2411, we have found signs of significant excess line broadening in eight of the 17 red giants with MV ≤ -1.4, which we interpret as rotation. In three cases, BD +30°2034, CD -37°14010, and HD 218732, the rotation is probably induced by tidal locking between axial rotation and the observed orbital motion with a stellar companion. But this cannot explain the other five stars in our sample that display signs of significant rotation. This high frequency of elevated rotational velocities does not appear to be caused by stellar mass transfer or mergers: there are too few main-sequence binaries with short enough periods. We also note that the lack of any noticeable increase in mean rotation at the magnitude level of the red giant branch luminosity function "bump" argues against the rapid rotation's being caused by the transport of internal angular momentum to the surface. Capture of a planetary-mass companion as a red giant expands in radius could explain the high rotational velocities. (4) We also find significant rotation in at least six of the roughly 15 (40%) red horizontal-branch stars in our survey. It is likely that the enhanced rotation seen among a significant fraction of both blue and red horizontal-branch stars arose when these stars were luminous red giants. Rapid rotation alone therefore appears insufficient cause to populate the blue side of the horizontal branch. While the largest projected rotational velocities seen among field blue and red horizontal-branch stars are consistent with their different sizes, neither are consistent with the large values we find for the largest red giants. This suggests that some form of angular momentum loss (and possibly mass loss) has been at work. Also puzzling is the apparent absence of rotation seen in field RR Lyrae variables. Angular momentum transfer and conservation in evolved metal-poor field stars thus pose many interesting questions for the evolution of low-mass stars

Location of the Optical Reverse Shock in the Cassiopeia A Supernova Remnant

We use two epochs of Hubble Space Telescope WFPC2 images separated by 2 yr to determine the location and propagation of the reverse shock (RS) in the young supernova remnant Cassiopeia A (Cas A). The images trace optical line emission from fast-moving knots and filaments of highly processed ejecta as they cross the RS, become heated and compressed, and radiatively cool. At numerous positions around the optical shell, new emission features are seen in the 2002 images that were not yet visible in the 2000 exposures. In a few instances emission features seen in the first epoch have completely disappeared in the second epoch. We concentrate on two regions along the rim of the main emission shell in Cas A for close inspection: one in the northwestern part of the shell and another along the southwestern part of it. In these regions the RS is viewed almost edge-on, and its precise position has been measured. The RS is coherent in these regions over arcminute (~1 pc) scales but is highly distorted perpendicular to the direction of expansion. We find the RS to be generally expanding at 50%-60% of the ~5500 km s-1 bulk velocity of the optical ejecta. We present shock models for the ejecta that are consistent with the high densities and short cooling times observed in the optical knots of the Cas A remnant