Prelude to, and Nature of the Space Photometry Revolution

It is now less than a decade since CoRoT initiated the space photometry revolution with breakthrough discoveries, and five years since Kepler started a series of similar advances. I'll set the context for this revolution noting the status of asteroseismology and exoplanet discovery as it was 15-25 years ago in order to give perspective on why it is not mere hyperbole to claim CoRoT and Kepler fostered a revolution in our sciences. Primary events setting up the revolution will be recounted. I'll continue with noting the major discoveries in hand, and how asteroseismology and exoplanet studies, and indeed our approach to doing science, have been forever changed thanks to these spectacular missions.Comment: Invited review for the CoRoT3-KASC7 Conference: The Space Photometry Revolution, Toulouse, France, July 2014. 6 page

Differential NICMOS Spectrophotometry at High S/N

Transiting extrasolar planets present an opportunity for probing atmospheric conditions and constituents by taking advantage of different apparent radii, hence transit depth as a function of wavelength. Strong near-IR bands should support detection of water vapor via G141 spectroscopy of the bright star HD 209458 (H=6.13) by comparing in- and out-of-transit ratios of in- and out-of-band spectral intensity ratios. The reduction and analysis of science observations in which the goal is to support 1 part in 10,000, or better, development of spectral diagnostics using NICMOS grism-based spectroscopy is discussed

Faint, moving objects in the Hubble Deep Field: components of the dark halo?

The deepest optical image of the sky, the Hubble Deep Field (HDF), obtained with the Hubble Space Telescope (HST) in December 1995, has been compared to a similar image taken in December 1997. Two very faint, blue, isolated and unresolved objects are found to display a substantial apparent proper motion, 23+/-5 mas/yr and 26+/-5 mas/yr; a further three objects at the detection limit of the second epoch observations may also be moving. Galactic structure models predict a general absence of stars in the color-magnitude range in which these objects are found. However, these observations are consistent with recently-developed models of old white dwarfs with hydrogen atmospheres, whose color, contrary to previous expectations, has been shown to be blue. If these apparently moving objects are indeed old white dwarfs with hydrogen atmospheres and masses near 0.5 M_Sun, they have ages of approximately 12 Gyr, and a local mass density that is sufficient, within the large uncertainties arising from the small size of the sample, to account for the entire missing Galactic dynamical mass.Comment: 6 pages, using emulateapj, including 2 colour figures, accepted for publication in ApJ Letter

Revision of Earth-sized Kepler Planet Candidate Properties with High Resolution Imaging by Hubble Space Telescope

We present the results of our Hubble Space Telescope program and describe how our analysis methods were used to re-evaluate the habitability of some of the most interesting Kepler planet candidates. Our program observed 22 Kepler Object of Interest (KOI) host stars, several of which were found to be multiple star systems unresolved by Kepler. We use our high-resolution imaging to spatially resolve the stellar multiplicity of Kepler-296, KOI-2626, and KOI-3049, and develop a conversion to the Kepler photometry (Kp) from the F555W and F775W filters on WFC3/UVIS. The binary system Kepler-296 (5 planets) has a projected separation of 0.217" (80AU); KOI-2626 (1 planet candidate) is a triple star system with a projected separation of 0.201" (70AU) between the primary and secondary components and 0.161" (55AU) between the primary and tertiary; and the binary system KOI-3049 (1 planet candidate) has a projected separation of 0.464" (225AU). We use our measured photometry to fit the separated stellar components to the latest Victoria-Regina Stellar Models with synthetic photometry to conclude that the systems are coeval. The components of the three systems range from mid-K dwarf to mid-M dwarf spectral types. We solved for the planetary properties of each system analytically and via an MCMC algorithm using our independent stellar parameters. The planets range from ~1.6R_Earth to ~4.2R_Earth, mostly Super Earths and mini-Neptunes. As a result of the stellar multiplicity, some planets previously in the Habitable Zone are, in fact, not, and other planets may be habitable depending on their assumed stellar host.Comment: 16 pages, 10 figures, ApJ, 804, 9

Photometric Oscillations of Low Luminosity Red Giant Stars

I present details of the variations of several hundred red giant stars on time scales of a few hours to a few days from Hubble Space Telescope (HST) observations of a low-extinction galactic bulge sample from an intensive seven day campaign. Variations in the red giants are shown to be a strong function of position within the color-magnitude diagram (CMD) in accord with general expectations from theory. Amplitudes are greater for stars with larger radii, whether this results from higher luminosity at the same effective temperature or lower temperature at a fixed apparent magnitude. Likewise, characteristic time scales for the variations increase to the upper right in a CMD as does the ratio of amplitudes measured at 606 nm compared to 814 nm. Characteristic variation time scales are well matched by low-order radial pulsation modes. The effective sample discussed here extends from about two magnitudes above the bulge turnoff at which red giant radii are ~7 R/R_{\odot} at 5,000 K with typical amplitudes of ~0.5 mmag to ~40 R/R_{\odot} at 4,000 K with amplitudes of ~3.5 mmag. Variability characteristics are quite similar at any given position in the CMD, and at levels in the CMD where oscillations are easily detected nearly all red giants show such. If these variations represent oscillations with sufficient lifetimes to derive accurate mode frequencies more extensive observations, e.g. as should soon be provided by the Kepler Mission}, would provide a rich asteroseismic return.Comment: 36 pages, 12 figures, 7 tables; accepted for publication in A

Kepler Mission Stellar and Instrument Noise Properties Revisited

An earlier study of the Kepler Mission noise properties on time scales of primary relevance to detection of exoplanet transits found that higher than expected noise followed to a large extent from the stars, rather than instrument or data analysis performance. The earlier study over the first six quarters of Kepler data is extended to the full four years ultimately comprising the mission. Efforts to improve the pipeline data analysis have been successful in reducing noise levels modestly as evidenced by smaller values derived from the current data products. The new analyses of noise properties on transit time scales show significant changes in the component attributed to instrument and data analysis, with essentially no change in the inferred stellar noise. We also extend the analyses to time scales of several days, instead of several hours to better sample stellar noise that follows from magnetic activity. On the longer time scale there is a shift in stellar noise for solar-type stars to smaller values in comparison to solar values.Comment: 10 pages, 8 figures, accepted by A

The Formation Rate of Blue Stragglers in 47 Tucanae

We investigate the effects of changes in the blue straggler formation rate in globular clusters on the blue straggler distribution in the color-magnitude diagram. We find that the blue straggler distribution is highly sensitive to the past formation rate. Comparing our models to new UBV observations of a region close to the core of 47 Tucanae suggests that this cluster may have stopped forming blue straggler formation several Gyr ago. This cessation of formation can be associated with an epoch of primordial binary burning which has been invoked in other clusters to infer the imminence of core collapse.Comment: 17 pages, 9 figures, submitted to the Astrophysical Journa

Solar-like oscillations in a metal-poor globular cluster with the HST

We present analyses of variability in the red giant stars in the metal-poor globular cluster NGC6397, based on data obtained with the Hubble Space Telescope. We use an non-standard data reduction approach to turn a 23-day observing run originally aimed at imaging the white dwarf population, into time-series photometry of the cluster's highly saturated red giant stars. With this technique we obtain noise levels in the final power spectra down to 50 parts per million, which allows us to search for low amplitude solar-like oscillations. We compare the observed excess power seen in the power spectra with estimates of the typical frequency range, frequency spacing and amplitude from scaling the solar oscillations. We see evidence that the detected variability is consistent with solar-like oscillations in at least one and perhaps up to four stars. With metallicities two orders of magnitude lower than of the Sun, these stars present so far the best evidence of solar-like oscillations in such a low metallicity environment.Comment: 7 pages, 6 figures, accepted by Ap