arXiv subjects

B. F. Lane

Publications and source records attributed to B. F. Lane.

17 recordsLinked to original sources

arXiv2007

The Palomar Testbed Interferometer Calibrator Catalog

The Palomar Testbed Interferometer (PTI) archive of observations between 1998 and 2005 is examined for objects appropriate for calibration of optical long-baseline interferometer observations - stars that are predictably point-like and single. Approximately 1,400 nights of data on 1,800 objects were examined for this investigation. We compare those observations to an intensively studied object that is a suitable calibrator, HD217014, and statistically compare each candidate calibrator to that object by computing both a Mahalanobis distance and a Principal Component Analysis. Our hypothesis is that the frequency distribution of visibility data associated with calibrator stars differs from non-calibrator stars such as binary stars. Spectroscopic binaries resolved by PTI, objects known to be unsuitable for calibrator use, are similarly tested to establish detection limits of this approach. From this investigation, we find more than 350 observed stars suitable for use as calibrators (with an additional $\approx 140$ being rejected), corresponding to $\gtrsim 95%$ sky coverage for PTI. This approach is noteworthy in that it rigorously establishes calibration sources through a traceable, empirical methodology, leveraging the predictions of spectral energy distribution modeling but also verifying it with the rich body of PTI's on-sky observations.

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arXiv2007

Interferometric Observations of V1663 Aquilae (Nova Aql 2005)

We have resolved the classical nova V1663 Aql using long-baseline near-IR interferometry covering the period from 5--18 days after peak brightness. We directly measure the shape and size of the fireball, which we find to be asymmetric. In addition we measure an apparent expansion rate of 0.21 +/- 0.03 mas/day. Assuming a linear expansion model we infer a time of initial outburst approximately 4 days prior to peak brightness. When combined with published spectroscopic expansion velocities our angular expansion rate implies a distance of 8.9 +/- 3.6 kpc. This distance measurement is independent of, but consistent with, determinations made using widely available photometric relations for novae.

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arXiv2006

Interferometric Observations of RS Ophiuchi and the Origin of the Near-IR Emission

We report observations of the recurrent nova RS Oph using long-baseline near-IR interferometry. We are able to resolve emission from the nova for several weeks after the February 2006 outburst. The near-IR source initially expands to a size of approximately 5 milli-arcseconds. However, beginning around day 10 the IR source appears to begin to shrink, reaching approximately 2 milli-arcseconds by day 100. We combine our measured angular diameters with previously available interferometric and photometric data to derive an emission measure for the source, and hence are able to determine the mass-loss rate of the nova in the days following the outburst.

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arXiv2006

Spectrally Dispersed K-Band Interferometric Observations of Herbig Ae/Be Sources: Inner Disk Temperature Profiles

We use spectrally dispersed near-IR interferometry data to constrain the temperature profiles of sub-AU-sized regions of 11 Herbig Ae/Be sources. We find that a single-temperature ring does not reproduce the data well. Rather, models incorporating radial temperature gradients are preferred. These gradients may arise in a dusty disk, or may reflect separate gas and dust components with different temperatures and spatial distributions. Comparison of our models with broadband spectral energy distributions suggests the latter explanation. The data support the view that the near-IR emission of Herbig Ae/Be sources arises from hot circumstellar dust and gas in sub-AU-sized disk regions. Intriguingly, our derived temperature gradients appear systematically steeper for disks around higher mass stars. It is not clear, however, whether this reflects trends in relative dust/gas contributions or gradients within individual components.

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arXiv2006

No Expanding Fireball: Resolving the Recurrent Nova RS Ophiuchi with Infrared Interferometry

Following the recent outburst of the recurrent nova RS Oph on 2006 Feb 12, we measured its near-infrared size using the IOTA, Keck, and PTI Interferometers at multiple epochs. The characteristic size of ~3 milliarcseconds hardly changed over the first 60 days of the outburst, ruling out currently-popular models whereby the near-infrared emission arises from hot gas in the expanding shock. The emission was also found to be significantly asymmetric, evidenced by non-zero closure phases detected by IOTA. The physical interpretation of these data depend strongly on the adopted distance to RS Oph. Our data can be interpreted as the first direct detection of the underlying RS Oph binary, lending support to the recent ``reborn red giant'' models of Hachisu & Kato. However, this result hinges on an RS Oph distance of ~< 540 pc, in strong disagreement with the widely-adopted distance of ~1.6 kpc. At the farther distance, our observations imply instead the existence of a non-expanding, dense and ionized circumbinary gaseous disk or reservoir responsible for the bulk of the near-infrared emission. Longer-baseline infrared interferometry is uniquely suited to distinguish between these models and to ultimately determine the distance, binary orbit, and component masses for RS Oph, one of the closest-known (candidate) SNIa progenitor systems.

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arXiv2005

Interferometric Observations of V838 Monocerotis

We have used long-baseline near-IR interferometry to resolve the peculiar eruptive variable V838 Mon and to provide the first direct measurement of its angular size. Assuming a uniform disk model for the emission we derive an apparent angular diameter at the time of observations (November-December 2004) of $1.83 \pm 0.06$ milli-arcseconds. For a nominal distance of $8\pm2$ kpc, this implies a linear radius of $1570 \pm 400 R_{\odot}$. However, the data are somewhat better fit by elliptical disk or binary component models, and we suggest that the emission may be strongly affected by ejecta from the outburst.

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arXiv2004

Resolved Inner Disks around Herbig Ae/Be Stars

We have observed 14 Herbig Ae/Be sources with the long-baseline near-IR Palomar Testbed Interferometer, All except two sources are resolved at 2.2 um, with angular sizes generally <5 mas. We determine the size scales and orientations of the 2.2 um emission using various models: uniform disks, Gaussians, uniform rings, flat accretion disks with inner holes, and flared disks with puffed-up inner rims; 7 objects display significantly inclined morphologies, generally compatible with the outer disk geometries inferred from millimeter interferometric observations, implying that HAEBE disks are not significantly warped. Using the derived inner disk sizes and inclinations, we compute the spectral energy distributions for two simple physical disk models, and compare these with observed SEDs compiled from the literature and new near-IR photometry. While geometrically flat accretion disk models are consistent with the data for the earliest spectral types in our sample (MWC 297, V1685 Cyg, and MWC 1080), the later-type sources are explained better through models incorporating puffed-up inner disk walls; this may indicate different accretion mechanisms for early and late-type Herbig Ae/Be stars.

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arXiv2003

The visual orbits of the spectroscopic binaries HD 6118 and HD 27483 from the Palomar Testbed Interferometer

We present optical interferometric observations of two double-lined spectroscopic binaries, HD 6118 and HD 27483, taken with the Palomar Testbed Interferometer (PTI) in the K band. HD 6118 is one of the most eccentric spectroscopic binaries and HD 27483 a spectroscopic binary in the Hyades open cluster. The data collected with PTI in 2001-2002 allow us to determine astrometric orbits and when combined with the radial velocity measurements derive all physical parameters of the systems. The masses of the components are 2.65 +/- 0.27 M_Sun and 2.36 +/- 0.24 M_Sun for HD 6118 and 1.38 +/- 0.13 M_Sun and 1.39 +/- 0.13 M_Sun for HD 27483. The apparent semi-major axis of HD 27483 is only 1.2 mas making it the closest binary successfully observed with an optical interferometer.

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arXiv2003

Differential Astrometry of Sub-arcsecond Scale Binaries at the Palomar Testbed Interferometer

We have used the Palomar Testbed Interferometer to perform very high precision differential astrometry on the 0.25 arcsecond separation binary star HD 171779. In 70 minutes of observation we achieve a measurement uncertainty of approximately 9 micro-arcseconds in one axis, consistent with theoretical expectations. Night-to-night repeatability over four nights is at the level of 16 micro-arcseconds. This method of very-narrow-angle astrometry may be extremely useful for searching for planets with masses as small as 0.5 Jupiter Masses around a previously neglected class of stars -- so-called ``speckle binaries.'' It will also provide measurements of stellar parameters such as masses and distances, useful for constraining stellar models at the 10^-3 level.

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arXiv2003

Near-Infrared Interferometric Measurements of Herbig Ae/Be Stars

We have observed the Herbig Ae/Be sources AB Aur, VV Ser, V1685 Cyg (BD+40 4124), AS 442, and MWC 1080 with the Palomar Testbed Interferometer, obtaining the longest baseline near-IR interferometric observations of this class of objects. All of the sources are resolved at 2.2 microns with angular size scales generally <5 mas, consistent with the only previous near-IR interferometric measurements of Herbig Ae/Be stars by Millan-Gabet and collaborators. We determine the angular size scales and orientations predicted by uniform disk, Gaussian, ring, and accretion disk models. Although it is difficult to distinguish different radial distributions, we are able to place firm constraints on the inclinations of these models, and our measurements are the first that show evidence for significantly inclined morphologies. In addition, the derived angular sizes for the early type Herbig Be stars in our sample, V1685 Cyg and MWC 1080, agree reasonably well with those predicted by the face-on accretion disk models used by Hillenbrand and collaborators to explain observed spectral energy distributions. In contrast, our data for the later-type sources AB Aur, VV Ser, and AS 442 are somewhat inconsistent with these models, and may be explained better through the puffed-up inner disk models of Dullemond and collaborators.

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arXiv2002

Calibration of the Barnes-Evans relation using interferometric observations of Cepheids

Direct diameter observations of Cepheid variables are used to calibrate the Barnes-Evans Cepheid surface brightness relation. Fifty-nine separate Cepheid diameter measurements from four different optical interferometers are used to calculate surface brightnesses as a function of magnitude and color. The linear fit to Cepheid surface brightness versus color is in excellent agreement with functions in the literature found using interferometric observations of non-variable giant and supergiant stars (Fouque & Gieren 1997). Using these relations the distance is calculated to delta Cephei, for which an independent distance is known from trigonometric parallax. The distance from the relation in this paper differs from that derived by the previously published relation by 4% but is still marginally within the combined errors. Both distances are well within the errors of the distance derived from trigonometric parallax.

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arXiv2002

Long baseline interferometric observations of Cepheids

We present observations of the galactic cepheids eta Aql and zeta Gem. Our observations are able to resolve the diameter changes associated with pulsation. This allows us to determine the distance to the Cepheids independent of photometric observations. We determine a distance to eta Aql of 320 +/- 32 pc, and a distance to zeta Gem of 362 +/- 38 pc. These observations allow us to calibrate surface brightness relations for use in extra-galactic distance determination. They also provide a measurement of the mean diameter of these Cepheids, which is useful in constructing structural models of this class of star.

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arXiv2001

The orbit of the brown dwarf binary Gl 569B

We present photometric, astrometric and spectroscopic observations of the nearby (9.8 pc) low-mass binary Gl 569Bab (in turn being a companion to the early-M star Gl 569A), made with the Keck adaptive optics facility. Having observed Gl 569Bab since August 1999, we are able to see orbital motion and to determine the orbital parameters of the pair. We find the orbital period to be 892 +/- 25 days, the semi-major axis to be 0.90 +/- 0.02 AU, the eccentricity to be 0.32 +/- 0.02 and the inclination of the system to be 34+/- 3 degrees (1-sigma). The total mass is found to be 0.123 (-0.022/+0.027) Msun (3-sigma). In addition, we have obtained low resolution (R=1500-1700) near-infrared spectra of each of the components in the J- and K-bands. We determine the spectral types of the objects to be M8.5V (Gl 569Ba) and M9V (Gl 569Bb) with an uncertainty of half a subclass. We also present new J- and K-band photometry which allows us to accurately place the objects in the HR diagram. Most likely the binary system is comprised of two brown dwarfs with a mass ratio of 0.89 and with an age of approximately 300 Myr.

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arXiv2001

Atmospheric Turbulence Measurements with the Palomar Testbed Interferometer

Data from the Palomar Testbed Interferometer, with a baseline length of 110 m and an observing wavelength of $2.2 μ{\rm m}$, were used to derive information on atmospheric turbulence on 64 nights in 1999. The measured two-aperture variance coherence times at $2.2 μ{\rm m}$ ranged from 25 msec to 415 msec (the lower value was set by instrumental limitations---the interferometer could not operate when the coherence time was lower than this). On all nights, the spectrum of the short time scale ($<600$ msec) delay fluctuations had a shallower spectrum than the theoretical Kolmogorov value of 5/3. On most nights, the mean value of the power law slope was between 1.40 and 1.50. Such a sub-Kolmogorov slope will result in the seeing improving as the $\approx 0.4$ power of wavelength, rather than the slower 0.2 power predicted by Kolmogorov theory. On four nights, the combination of delay and angle tracking measurements allowed a derivation of the (multiple) wind velocities of the turbulent layers, for a frozen-flow model. The derived wind velocities were all $\le 4 {\rm m\ s^{-1}}$, except for a small $10 {\rm m s^{-1}}$ component on one night. The combination of measured coherence time, turbulence spectral slope, and wind velocity for the turbulent layer(s) allowed a robust solution for the outer scale size (beyond which the fluctuations do not increase). On the four nights with angle tracking data, the outer scale varied from 6 to 54 m, with most values in the 10-25 m range. Such small outer scale values cause some components of visibility and astrometric errors to average down rapidly.

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arXiv2000

A Preliminary Visual Orbit of BY Draconis

We report on the preliminary determination of the visual orbit of the double-lined spectroscopic binary system BY Draconis with data obtained by the Palomar Testbed Interferometer in 1999. BY Dra is a nearly equal-mass double-lined binary system whose spectroscopic orbit is well known. We have estimated the visual orbit of BY Dra from our interferometric visibility data fit both separately and in conjunction with archival radial velocity data. Our BY Dra orbit is in good agreement with the spectroscopic results. Due to the orbit's face-on orientation, the physical parameters implied by a combined fit to our visibility data and radial velocity data do not yet result in precise component masses and a system distance, but with continued interferometric monitoring we hope to improve the mass estimates to better than 10% determinations.

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arXiv1999

The Discovery of a Companion to the Very Cool Dwarf Gl~569~B with the Keck Adaptive Optics Facility

We report observations obtained with the Keck adaptive optics facility of the nearby (d=9.8 pc) binary Gl~569. The system was known to be composed of a cool primary (dM2) and a very cool secondary (dM8.5) with a separation of 5" (49 Astronomical Units). We have found that Gl~569~B is itself double with a separation of only 0".101$\pm$0".002 (1 Astronomical Unit). This detection demonstrates the superb spatial resolution that can be achieved with adaptive optics at Keck. The difference in brightness between Gl~569~B and the companion is $\sim$0.5 magnitudes in the J, H and K' bands. Thus, both objects have similarly red colors and very likely constitute a very low-mass binary system. For reasonable assumptions about the age (0.12~Gyr--1.0~Gyr) and total mass of the system (0.09~M$_\odot$--0.15~M$_\odot$), we estimate that the orbital period is $\sim$3 years. Follow-up observations will allow us to obtain an astrometric orbit solution and will yield direct dynamical masses that can constrain evolutionary models of very low-mass stars and brown dwarfs.

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arXiv1999

The Visual Orbit of 64 Piscum

We report on the determination of the visual orbit of the double-lined spectroscopic binary system 64 Piscum with data obtained by the Palomar Testbed Interferometer in 1997 and 1998. 64 Psc is a nearly equal-mass double-lined binary system whose spectroscopic orbit is well known. We have estimated the visual orbit of 64 Psc from our interferometric visibility data. Our 64 Psc orbit is in good agreement with the spectroscopic results, and the physical parameters implied by a combined fit to our interferometric visibility data and radial velocity data of Duquennoy and Mayor result in precise component masses that agree well with their spectral type identifications. In particular, the orbital parallax of the system is determined to be 43.29 \pm 0.46 mas, and masses of the two components are determined to be 1.223 \pm 0.021 M_{\sun} and 1.170 \pm 0.018 M_{\sun}, respectively. Nadal et al. put forward arguments of temporal variability in some of the orbital elements of 64 Psc, presumably explained by an undetected component in the system. While our visibility data does not favor the Nadal temporal variability inference, neither is it definitive in excluding it. Consequently we have performed both high dynamic-range near-infrared imaging and spectroscopy of potential additional companions to the 64 Psc system. Our imaging and spectroscopic data do not support the conjecture of an additional component to 64 Psc, but we did identify a faint object with unusual red colors and spectra.

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