Binary Star Observations in Selected Instants of Good Seeing

We present 549 observations of 181 primarily southern binary stars. Of these, 32 are high-quality nondetections, meaning that, if binary, the system had a separation below the diffraction limit at the time of the observation, and relative astrometry is presented for the remaining 517 observations. In addition, a magnitude difference measure is reported in 312 cases in which the observation was judged to be of sufficient quality to have little decorrelation of the speckle pattern of the secondary relative to the primary star. These data were obtained from speckle observations taken at the Lowell-Tololo 0.6 m telescope at Cerro Tololo Inter-American Observatory using a fast-readout CCD detector during 2001 November. Results from an astrometric measurement precision study indicate that the measures have typical uncertainties of 12.2 ± 1.4 mas in separation and 128 ± 021 in position angle with little systematic error. The magnitude differences presented show good agreement with values in the Hipparcos catalog where comparisons can be made. Their uncertainties are also characterized; they show a typical value of 0.18 mag per 2 minute observation. Four systems of particular interest are discussed.

The number of exoplanets found with periods as short as one day and less was surprising given how fast these planets had been expected to migrate into the star due to the tides raised on the star by planets at such close distances. It has been seen as improbable that we would find planets in such a small final fraction of their lives. The favored solution has been that the tidal dissipation is much weaker than expected, which would mean that the final infall would be a larger fraction of the planets' life. We find no reason to exclude the explanation that a small number of planets are continuously sent migrating inwards such that these planets indeed are in the last fraction of their lives. Following the observation that the distribution of medium planets disfavors tidal dissipation being significantly weaker than has been found from observations of binary stars, we now show that the numbers of planets in such a "flow" of excess planets migrating inwards is low enough that even depletion of the three-day pileup is a plausible source. Then the shortest period occurrence distribution would be shaped by planets continuously being sent into the star, which may explain the depletion of the pileup in the Kepler field relative to the solar neighborhood (Howard et al. 2012, hereafter H12). Because Kepler observes above the galactic plane, H12 suggested the Kepler field may include an older population of stars. The tidal dissipation strength in stars due to giant planets may be not greatly weaker than it is in binary stars.

Aims. Accurately measuring the atmospheric coherence time is still a significant problem despite a variety of applicable methods. The Multi-Aperture Scintillation Sensor (MASS) designed for the vertical profiling of optical turbulence also provides a measurements of coherence time, but its results were found to be biased. Hence there is a need for a more robust method to determine τ0.

Five hundred twelve relative astrometry measures are presented for 253 double stars, including 53 double stars discovered by Hipparcos. In 15 cases, relative astrometry is reported for the first time for newly confirmed pairs. In addition, 20 high-quality nondetections of companions are reported for stars suspected of being nonsingle by Hipparcos. Observations were taken using a fast-readout CCD camera system at the WIYN 3.5 m telescope at Kitt Peak, Arizona. In comparing these measures with ephemeris predictions for binary stars with very well known orbits, we find that the measurement precision is better than 3 mas in separation and 1° in position angle per individual observation. Measurement precision and detection capabilities are fully discussed, and confirmed orbital motion is reported in four cases of the Hipparcos double star discoveries.

Betelgeuse—the closest M-supergiant to the Sun—has recently been predicted to host a lower-mass stellar companion that orbits the primary with a period of ∼6 yr. The putative stellar companion is thought to cause the long photometric modulation observed in Betelgeuse, which cannot be explained by stellar pulsations. Additionally, radial velocity and astrometric data also point to a stellar companion. Here we present diffraction-limited optical speckle imaging observations obtained on the 8.1 m Gemini North telescope in 2020 and 2024. The 2020 observations were taken during the Great Dimming event and at a time when the stellar companion was predicted to be unobservable because it was directly in line with Betelgeuse itself. The 2024 observations were taken 3 days after the predicted time of greatest elongation for the companion. A comparison of the 2020 and 2024 data reveals no companion in 2020 (as expected) and the probable detection of a companion in 2024. The presumed stellar companion has an angular separation and position angle of 52 mas and 115° east of north, respectively, which is in excellent agreement with predictions from dynamical considerations. The detected companion is roughly 6 magnitudes fainter than Betelgeuse at 466 nm. While this is only a 1.5σ detection, five results are in reasonable agreement with the predictions: the appearance of the companion at quadrature; the angular separation from Betelgeuse; the position angle with respect to Betelgeuse; the magnitude difference; and the estimated mass of the companion.

Observations of binary stars containing an accreting black hole or neutron star often show x-ray emission extending to high energies (>10 kilo--electron volts), which is ascribed to an accretion disk corona of energetic particles akin to those seen in the solar corona. Despite their ubiquity, the physical conditions in accretion disk coronae remain poorly constrained. Using simultaneous infrared, optical, x-ray, and radio observations of the Galactic black hole system V404 Cygni, showing a rapid synchrotron cooling event in its 2015 outburst, we present a precise 461 ± 12 gauss magnetic field measurement in the corona. This measurement is substantially lower than previous estimates for such systems, providing constraints on physical models of accretion physics in black hole and neutron star binary systems.

CONTEXT. Massive stars have high-multiplicity fractions, and many of them have still undetected components, thus hampering the study of their properties. AIMS. I study a sample of massive stars with high angular resolution to better characterize their multiplicity. METHODS. I observed 138 fields that include at least one massive star with AstraLux, a lucky imaging camera at the 2.2 m Calar Alto telescope. I also used observations of 3 of those fields with ACS/HRC on HST to obtain complementary information and to calibrate the AstraLux data. The results were compared with existing information from the Washington Double Star Catalog, Tycho-2, 2MASS, and other literature results. RESULTS. I discover 16 new optical companions of massive stars, the majority of which are likely to be physically bound to their primaries. I also improve the accuracy for the separation and magnitude difference of many previously known systems. In a few cases the orbital motion is detected when comparing the new data with existing ones and constraints on the orbits are provided. CONCLUSIONS. The analysis indicate that the majority of the AstraLux detections are bound pairs. For a range of separations of 0.1"-14" and magnitude differences lower than 8, I find that the multiplicity fraction for massive stars is close to 50%. When objects outside those ranges are included, the multiplicity fraction should be considerably higher.

The well-known Langley extrapolation technique produces measurements of atmospheric optical depth (AOD) by collecting direct sun irradiance at multiple zenith angles. One common application of this technique is used by sun photometers such as in NASA’s AErosol Robotic Network (AERONET). This large, spatially distributed network collects time averaging data from across the globe and applying Beer’s Law, produces hourly estimates of AOD. While this technique has produced excellent data, the dependence on direct sun irradiance requires cloudless skies and line-ofsight to the sun. Atmospheric LIDARs, on the other hand, can operate in the presence of clouds and can also produce range-resolved measurements of AOD by applying the same Langley technique. For aerosol LIDARs, this technique requires that the LIDAR be capable of producing high quality waveforms within the atmospheric coherence time and also be capable of taking measurements off zenith. At least two unique angles are required to produce data, although 3+ are recommended. This paper will present an overview of the Langley technique applied with a 1064 nm atmospheric aerosol LIDAR, an overview of the LIDAR hardware and capabilities, sample data collected by the LIDAR, and challenges associated with this technique. It will be shown that while this technique is useful, it requires measurements at all three angles to be made when the atmosphere is reasonably horizontally homogenous. Furthermore, the system optics, alignment, and laser power must be kept constant (keeping the LIDAR’s system constant the same for all measurements) for the data to be useful in a Langley analysis.

The NASA Deep Space Network (DSN) is studying arrays of large numbers of small, mass-produced radio antennas as a cost-effective way to increase downlink sensitivity and data rates for future missions. An important issue for the operation of large arrays is the accuracy with which signals from hundreds of small antennas can be combined. This is particularly true at Ka band (32 GHz) where atmospheric phase variations can be large and rapidly changing. A number of algorithms exist to correct the phases of signals from individual antennas in the case where a spacecraft signal provides a useful signal-to-noise ratio (SNR) on time scales shorter than the atmospheric coherence time. However, for very weak spacecraft signals it will be necessary to rely on background natural radio sources to maintain array phasing. Very weak signals could result from a spacecraft emergency or by design, such as direct-to-Earth data transmissions from distant planetary atmospheric or surface probes using only low gain antennas. This paper considers the parameter space where external real-time phase calibration will be necessary, and what this requires in terms of array configuration and signal processing. The inherent limitations of this technique are also discussed

Using the adaptive optics facilities at the 200-in Hale and 10-m Keck II, we observed in the near infrared a sample of 12 binary and multiple stars and one open cluster. We used the near diffraction limited images of these systems to measure the relative separations and position angles between their components. In this paper, we investigate and correct for the influence of the differential chromatic refraction and chip distortions on our relative astrometric measurements. Over one night, we achieve an astrometric precision typically well below 1 miliarcsecond and occasionally as small as 40 microarcseconds. Such a precision is in principle sufficient to astrometrically detect planetary mass objects around the components of nearby binary and multiple stars. Since we have not had sufficiently large data sets for the observed sample of stars to detect planets, we provide the limits to planetary mass objects based on the obtained astrometric precision.

We present low-resolution (R ~ 90) and medium-resolution (R ~ 2500) spectropolarimetry of nova V475 Sct taken with the HBS instrument, mounted on the 0.91 m telescope at the Okayama Astrophysical Observatory, and taken with the Faint Object Camera and Spectrograph, mounted on the 8.2 m Subaru telescope. We estimated the interstellar polarization toward the nova from the steady continuum polarization components and Hα line emission components. After subtracting the interstellar polarization component from the observations, we found that the Hα emission seen on 2003 October 7 was clearly polarized. In the polarized flux spectrum the Hα emission had a distinct red wing extending to ~+4900 km s-1 and a shoulder around +3500 km s-1, showing a constant position angle (P.A.) of linear polarization θ* 155° ± 15°. This suggests that the nova had an asymmetric outflow with a velocity of vwind 3500 km s-1 or more, which is 6 times higher than the expansion velocity of the ionized shell at the same epoch. Such a high-velocity component has not previously been reported for a nova in the moderately fast speed class. Our observations suggest the occurrence of violent mass-loss activity in the nova binary system even during the common-envelope phase. The P.A. of the polarization in the Hα wing is in good agreement with that of the continuum polarization found on 2003 September 26 (p* 0.4%-0.6%), which disappeared within the following 2 days. The uniformity of the P.A. between the continuum polarization and the wing polarization on October 7 suggests that the axis of the circumstellar asymmetry remained nearly constant during the period of our observations.

Two hundred seventy-two magnitude difference measures of 135 double star systems are presented. The results are derived from speckle observations using the Bessel V and R passbands and a fast readout CCD camera. Observations were taken at two 60 cm telescopes, namely the Helen Sawyer Hogg Telescope, formerly at Las Campanas, Chile, and the Lowell-Tololo Telescope at the Cerro Tololo Inter-American Observatory, Chile. The data analysis method is presented and, in comparing the results to those of Hipparcos as well as to recent results using adaptive optics, we find very good agreement. Overall, the measurement precision appears to be dependent on seeing and other factors but is generally in the range of 0.10–0.15 mag for single observations under favorable observing conditions. In four cases, multiple observations in both V and R allowed for the derivation of component V-R colors with uncertainties of 0.11 mag or less. Spectral types are assigned and preliminary effective temperatures are estimated in these cases.

We perform consistent reductions and measurements for three ultra-faint dwarf galaxies (UFDs): Boötes I, Leo IV, and Leo V. Using the public archival data from the GIRAFFE spectrograph on the Very Large Telescope (VLT), we locate new members and provide refined measurements of physical parameters for these dwarf galaxies. We identify nine new Leo IV members and four new Leo V members, and perform a comparative analysis of previously discovered members. Additionally, we identify one new binary star in both Leo IV and Leo V. After removing binary stars, we recalculate the velocity dispersions of Boötes I and Leo IV to be 5.1 − 0.8 + 0.7 and 3.4 − 0.9 + 1.3 km s−1, respectively; we do not resolve the Leo V velocity dispersion. We identify a weak velocity gradient in Leo V that is ∼4× smaller than the previously calculated gradient and that has a corresponding position angle that differs from the value in the literature by ∼120°. Combining the VLT data with previous values from the literature, we reanalyze the Boötes I metallicity distribution function and find that a model including infall of pristine gas, while Boötes I was forming stars’ best fits the data. Our analysis of Leo IV, Leo V, and other UFDs will enhance our understanding of these enigmatic stellar populations and contribute to future dark matter studies. This is the first in a series of papers examining 13 UDFs observed with VLT/GIRAFFE between 2009 and 2017. Similar analyses of the remaining 10 UFDs will be presented in forthcoming papers.

The Optical Gravitational Lensing Experiment (OGLE) continuously monitors hundreds of thousands of eclipsing binaries in the Galactic bulge field and the Magellanic Clouds. These objects have been classified into major morphological subclasses, such as contact, noncontact, ellipsoidal, and cataclysmic variables, both by matching the light curves with predefined templates and by visual inspections. Here we present the result of a machine-learned automatic classification based on the morphology of light curves inspired by the classification of eclipsing binaries observed by the original Kepler mission. We similarly use a dimensionality reduction technique with locally linear embedding to map the high dimension of the data set into a low-dimensional embedding parameter space, while keeping the local geometry and the similarities of the neighboring data points. After three consecutive steps, we assign one parameter to each binary star, which scales well with the “detachness,” i.e., the sum of the relative radii of the components. This value is in good agreement with the morphology types listed in the OGLE catalog and, along with the orbital periods, can be used to filter any morphological subtypes based on the similarity of light curves. Our open-source pipeline can be applied in a fully automatic way to any other large data set to classify binary stars.

The WFPC2 camera aboard the Hubble Space Telescope was used to obtain images of the planetary nebula BD +30°3639 at two epochs separated by 5.663 yr. The expansion of the nebula in the Hα and [N II] bands has been measured using several methods. Detailed expansion maps for both emission lines were constructed from nearly 200 almost independent features. There is good agreement between the (independent) Hα and [N II] proper motions. There are clear deviations from uniform radial expansion, with higher expansion rates in regions where the shell is faintest, such as the southwest quadrant. The Space Telescope Imaging Spectrograph was used to obtain echelle spectra in the C II] λ2326 multiplet and the [O II] λ2470 doublet, providing well-resolved expansion velocities at two position angles. From the C II] lines we find that the central velocity split is ±36.3 km s-1 at a position angle (P.A.) of 99° and ±33.5 km s-1 at P.A. 25°. The fainter [O II] doublet does not appear to differ from the C II] multiplet. To determine the distance of BD +30°3639 by comparison of the angular expansion and the spectroscopically determined radial expansion, we must address the problem of the three-dimensional shape of the nebula. We measured the angular expansion along the position of the 99° echelle slit, finding displacements of 4.25 mas yr-1 at the shell edge (247 from the center). If the nebula were spherical, this would imply a distance of 1.80 kpc. But there is evidence that the nebula is elongated along the line of sight, which suggests that the actual distance is less. Radio continuum images from 5 and 15 GHz VLA observations provide information on the extent of the radial elongation. We fit the radio brightness variation and the echelle data by approximating the nebula as an ellipsoid, also making use of the ground-based echelle spectra reported by Bryce & Mellema. Our model has an axial ratio of 1.56, is inclined to the line of sight by 97, and exhibits an expansion in the plane of the sky which is that in the radial direction, leading to a distance of 1.2 kpc. Not all the kinematic data fit this simple model, so the distance must still be regarded as uncertain. Based on the recent model atmosphere of Crowther et al., a distance of 1.2 kpc implies a stellar luminosity of 4250 L⊙. The kinematic age of the nebula, θ/, varies somewhat from region to region. A good average value is 800 yr, while the expansion along the position of the 99° echelle slit gives about 600 yr.