Astrometry with the Hubble Space Telescope: Trigonometric Parallaxes of Selected Hyads

We present absolute parallaxes and proper motions for seven members of the Hyades open cluster, pre-selected to lie in the core of the cluster. Our data come from archival astrometric data from FGS 3, and newer data for 3 Hyads from FGS 1R, both white-light interferometers on the Hubble Space Telescope (HST). We obtain member parallaxes from six individual Fine Guidance Sensor (FGS) fields and use the field containing van Altena 622 and van Altena 627 (= HIP 21138) as an example. Proper motions, spectral classifications and VJHK photometry of the stars comprising the astrometric refer- ence frames provide spectrophotometric estimates of reference star absolute parallaxes. Introducing these into our model as observations with error, we determine absolute parallaxes for each Hyad. The parallax of vA 627 is significantly improved by including a perturbation orbit for this previously known spectroscopic binary, now an astrometric binary. Compared to our original (1997) determina- tions, a combination of new data, updated calibration, and improved analysis lowered the individual parallax errors by an average factor of 4.5. Comparing parallaxes of the four stars contained in the Hipparcos catalog, we obtain an average factor of 11 times improvement with the HST . With these new results, we also have better agreement with Hipparcos for the four stars in common. These new parallaxes provide an average distance for these seven members, = 47.5 pc, for the core a \pm 1 - {\sigma} dispersion depth of 3.6 pc, and a minimum depth from individual components of 16.0 \pm 0.9 pc. Absolute magnitudes for each member are compared to established main sequences, with excellent agreement. We obtain a weighted average distance modulus for the core of the Hyades of m-M=3.376 \pm 0.01, a value close to the previous Hipparcos values, m-M=3.33\pm 0.02.Comment: 21 pages, 7 figures, Astronomical Journal, accepted 2011-3-

The Mass of the Candidate Exoplanet Companion to HD136118 from Hubble Space Telescope Astrometry and High-Precision Radial Velocities

We use Hubble Space Telescope Fine Guidance Sensor astrometry and high-cadence radial velocities for HD136118 from the HET with archival data from Lick to determine the complete set of orbital parameters for HD136118b. We find an orbital inclination for the candidate exoplanet of i_{b} = 163.1 +- 3.0 deg. This establishes the actual mass of the object, M_{b} = 42^{+11}_{-18} MJup, in contrast to the minimum mass determined from the radial velocity data only, M_{b}sin{i} ~ 12 MJup. Therefore, the low-mass companion to HD 136118 is now identified as a likely brown dwarf residing in the "brown dwarf desert".Comment: 35 pages, 12 figures, 10 tables. Accepted for publication in Astrophysical Journa

Hubble Space Telescope Fine Guidance Sensor Parallaxes For Four Classical Novae

We have used data obtained with the Fine Guidance Sensors on the Hubble Space Telescope to derive precise astrometric parallaxes for four classical novae: V603 Aql, DQ Her, GK Per, and RR Pic. All four objects exceeded the Eddington limit at visual maximum. Re-examination of the original light curve data for V603 Aql and GK Per has led us to conclude that their visual maxima were slightly brighter than commonly assumed. With known distances, we examine the various maximum magnitude-rate of decline relationships that have been established for classical novae. We find that these four objects show a similar level of scatter about these relationships as seen in larger samples of novae whose distances were determined using indirect techniques. We also examine the nebular expansion parallax method and find that it fails for three of the four objects. In each case it was possible to find an explanation for the failure of that technique to give precise distance estimates. DQ Her appears to suffer from an anomalously high extinction when compared to field stars on its sight line. We suggest that this is likely due to local material, which may also be the source of the IRAS detections of this object.NASA from the Space Telescope Science Institute AR12617NASA NAS 5-26555McDonald Observator

Approximate Canonical Quantization for Cosmological Models

In cosmology minisuperspace models are described by nonlinear time-reparametrization invariant systems with a finite number of degrees of freedom. Often these models are not explicitly integrable and cannot be quantized exactly. Having this in mind, we present a scheme for the (approximate) quantization of perturbed, nonintegrable, time-reparametrization invariant systems that uses (approximate) gauge invariant quantities. We apply the scheme to a couple of simple quantum cosmological models.Comment: 16 pages, Latex, accepted for publication in Int. Jou. Mod. Phys.

The Mass of HD 38529 c from Hubble Space Telescope Astrometry and High-Precision Radial Velocities

(Abridged) Hubble Space Telescope (HST) Fine Guidance Sensor astrometric observations of the G4 IV star HD 38529 are combined with the results of the analysis of extensive ground-based radial velocity data to determine the mass of the outermost of two previously known companions. Our new radial velocities obtained with the Hobby-Eberly Telescope and velocities from the Carnegie-California group now span over eleven years. With these data we obtain improved RV orbital elements for both the inner companion, HD 38529 b and the outer companion, HD 38529 c. We identify a rotational period of HD 38529 (P_{rot}=31.65 +/- 0.17 d) with FGS photometry. We model the combined astrometric and RV measurements to obtain the parallax, proper motion, perturbation period, perturbation inclination, and perturbation size due to HD 38529 c. For HD 38529 c we find P = 2136.1 +/- 0.3 d, perturbation semi-major axis \alpha =1.05 +/-0.06$mas, and inclination$i$= 48.3 deg +/- 4 deg. Assuming a primary mass M_* = 1.48 M_{sun}, we obtain a companion mass M_c = 17.6 ^{+1.5}_{-1.2} M_{Jup}, 3-sigma above a 13 M_{Jup} deuterium burning, brown dwarf lower limit. Dynamical simulations incorporating this accurate mass for HD 38529 c indicate that a near-Saturn mass planet could exist between the two known companions. We find weak evidence of an additional low amplitude signal that can be modeled as a planetary-mass (~0.17 M$_{Jup}) companion at P~194 days. Additional observations (radial velocities and/or Gaia astrometry) are required to validate an interpretation of HD 38529 d as a planetary-mass companion. If confirmed, the resulting HD 38529 planetary system may be an example of a "Packed Planetary System".Comment: Accepted by The Astronomical Journa

The Internal Proper Motions Of Stars In The Open Cluster M35

Relative proper motions, based on 108 orbits of Hubble Space Telescope Fine Guidance Sensor data extending from 1992 to 2006, are reported for 74 stars in the open cluster M35 (NGC 2168). A subset of 22 of these objects are then used to compute the cluster's internal proper motion dispersions in both right ascension and declination. We find that these dispersions are equal to within their measurement errors. The average one-dimensional dispersion is 0.018 +/- 0.002 arcsec century(-1). When combined with the M35 radial velocity dispersion of 0.65 +/- 0.10 km s(-1) found by Geller et al., this produces a cluster distance of 762 +/- 145 pc. Using isochrone fits to the cluster main sequence, this distance suggests that M35 has an age of about 133 Myr. Although this age is consistent with that typically found for M35, the formal error in the dynamical distance of +/- 19% can accommodate ages between 65 Myr and 201 Myr.McDonald Observator