arXiv subjects

Brian D. Mason

Publications and source records attributed to Brian D. Mason.

At least 19 recordsLinked to original sources

arXiv2026

Speckle Interferometry at SOAR in 2024 and 2025

Results of speckle interferometry observations at the 4.1 m SOuthern Astrophysical Research (SOAR) telescope obtained during 2024-2025 are presented. We present 5316 measurements of relative positions and magnitude differences in 3532 pairs (including 524 unpublished measures made before 2024) with median and minimum separations of 0.19" and 12 mas, respectively; non-resolutions of 1723 stars are documented as well. More than 400 pairs have been resolved here for the first time and not resolved by Gaia; among those are 222 TESS objects of interest, 46 inner subsystems in known wider binaries within 100 pc, and 43 subdwarfs. Positional measurements are used to compute or improve binary orbits; elements of 202 orbits with meaningful errors are given here, while preliminary and tentative orbits are published elsewhere. Of special note are orbits with large and accurately measured eccentricties (e.g. e=0.9866+/-0.0014 for J13038-2035) and orbits of pre-main sequence binaries. Appendix contains parameters of 86 binaries used for calibration of pixel scale and orientation.

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arXiv2024

Speckle Interferometry at SOAR in 2023

Results of the speckle-interferometry observations at the 4.1 m Southern Astrophysical Research Telescope (SOAR) obtained during 2023 are presented: 1913 measurements of 1533 resolved pairs or subsystems (median separation 0.16") and non-resolutions of 552 targets; 42 pairs are resolved here for the first time. This work continues our long-term effort to monitor orbital motion in close binaries and hierarchical systems. A large number (147) of orbits have been determined for the first time or updated using these measurements. Complementarity of this program with the Gaia mission is highlighted.

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arXiv2022

Speckle Interferometry at SOAR in 2021

The speckle interferometry program at the the 4.1 m Southern Astrophysical Research Telescope (SOAR), started in 2008, now accumulated over 30,300 individual observations of 12,700 distinct targets. Its main goal is to monitor orbital motion of close binaries, including members of high-order hierarchies and low-mass dwarfs in the solar neighborhood. The results from 2021 are published here, totaling 2,623 measurements of 2,123 resolved pairs and non-resolutions of 763 targets. The median measured separation is 0.21", and 75 pairs were closer than 30 mas. The calibration of scale and orientation is based on the observations of 103 wide pairs with well-modeled motion. These calibrators are compared to the latest Gaia data release, and minor (0.5%) systematic errors were rectified, resulting in accurate relative positions with typical errors on the order of 1 mas. Using these new measurements, orbits of 282 binaries are determined here (54 first determinations and 228 corrections). We resolved for the first time 50 new pairs, including subsystems in known binaries. A list of 94 likely spurious pairs unresolved at SOAR (mostly close Hipparcos binaries) is also given.

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arXiv2021

Speckle Interferometry at SOAR in 2020

The results of speckle interferometric observations at the 4.1 m Southern Astrophysical Research Telescope (SOAR) in 2020, as well as earlier unpublished data, are given, totaling 1735 measurements of 1288 resolved pairs and non-resolutions of 1177 targets. We resolved for the first time 59 new pairs or subsystems in known binaries, mostly among nearby dwarf stars. This work continues our long-term speckle program. Its main goal is to monitor orbital motion of close binaries, including members of high-order hierarchies and Hipparcos pairs in the solar neighborhood. We also report observations of 892 members of young moving groups and associations, where we resolved 103 new pairs.

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arXiv2020

Hubble Space Telescope Snapshot Survey for Resolved Companions of Galactic Cepheids: Final Results

Cepheids in multiple systems provide information on the outcome of the formation of massive stars. They can also lead to exotic end-stage objects. This study concludes our survey of 70 galactic Cepheids using the {\it Hubble Space Telescope\} (\HST) Wide Field Camera~3 (WFC3) with images at two wavelengths to identify companions closer than $5\arcsec$. In the entire WFC3 survey we identify 16 probable companions for 13 Cepheids. The seven Cepheids having resolved candidate companions within $2"$ all have the surprising property of themselves being spectroscopic binaries (as compared with a 29\% incidence of spectroscopic binaries in the general Cepheid population). That is a strong suggestion that an inner binary is linked to the scenario of a third companion within a few hundred~AU\null. This characteristic is continued for more widely separated companions. Under a model where the outer companion is formed first, it is unlikely that it can anticipate a subsequent inner binary. Rather it is more likely that a triple system has undergone dynamical interaction, resulting in one star moving outward to its current location. {\it Chandra\} and {\it Gaia\} data as well as radial velocities and \HSTSTIS and {\it IUE\} spectra are used to derive properties of the components of the Cepheid systems. The colors of the companion candidates show a change in distribution at approximately 2000~AU separations, from a range including both hot and cool colors for closer companions, to only low-mass companions for wider separations.

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arXiv2020

Speckle interferometry at SOAR in 2019

The results of speckle interferometric observations at the 4.1 m Southern Astrophysical Research Telescope (SOAR) in 2019 are given, totaling 2555 measurements of 1972 resolved pairs with separations from 15 mas (median 0.21") and magnitude difference up to 6 mag, and non-resolutions of 684 targets. We resolved for the first time 90 new pairs or subsystems in known binaries. This work continues our long-term speckle program. Its main goal is to monitor orbital motion of close binaries, including members of high-order hierarchies and Hipparcos pairs in the solar neighborhood. We give a list of 127 orbits computed using our latest measurements. Their quality varies from excellent (25 orbits of grades 1 and 2) to provisional (47 orbits of grades 4 and 5).

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arXiv2019

Speckle interferometry at SOAR in 2018

The results of speckle interferometric observations at the 4.1 m Southern Astrophysical Research Telescope (SOAR) in 2018 are given, totaling 3097 measurements of 2427 resolved pairs with separations from 11 mas to 5.9" (median 0.15", magnitude difference up to 7 mag) and non-resolutions of 624 targets. This work continues our long-term speckle program. Its main goal is to monitor orbital motion of close binaries, including members of high-order hierarchies and Hipparcos pairs in the solar neighborhood. Also, pre-main-sequence stars in the Orion OB1 association were surveyed, resolving 26 out of 118 targets. In addition, we report discovery of 35 new companions among field visual multiples (some of which are likely optical) and first-time resolutions of another 31 pairs. By combining the measurements given here with the published ones, we computed 76 orbits for the first time and updated orbital elements of 34 visual binaries. Their periods range from 0.65 to 1100 years, and their quality varies from first tentative solutions of grade 5 to accurate elements of grades 1 and 2. Finally, a list of 53 spurious pairs discovered by various techniques and unresolved at SOAR

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arXiv2018

Speckle Interferometry at the U.S. Naval Observatory. XXIII

The results of 3,989 intensified CCD observations of double stars, made with the 26-inch refractor of the U.S. Naval Observatory, are presented. Each observation of a system represents a combination of over two thousand short-exposure images. These observations are averaged into 1,911 mean relative positions and range in separation from 0.289 to 128.638, with a median separation of 8.669. Four orbits are improved. This is the 23rd in this series of papers and covers the period 4 January 2017 through 13 September 2017.

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arXiv2018

Speckle interferometry at SOAR in 2016 and 2017

The results of speckle interferometric observations at the 4.1 m SOAR telescope in 2016 and 2017 are given, totaling 2483 measurements of 1570 resolved pairs and 609 non-resolutions. We describe briefly recent changes in the instrument and observing method and quantify the accuracy of the pixel scale and position angle calibration. Comments are given on 44 pairs resolved here for the first time. Orbital motion of the newly resolved subsystem BU~83 Aa,Ab roughly agrees with its 36 year astrometric orbit proposed by J.~Dommanget. Most Tycho binaries examined here turned out to be spurious.

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arXiv2018

Speckle Interferometry of Red Dwarf Stars

We report high resolution optical speckle observations of 336 M dwarfs which result in 113 measurements of relative position of 80 systems and 256 other stars with no indications of duplicity. These are the first measurements for two of the systems. We also present the earliest measures of relative position for 17 others. We include orbits for six of the systems, two revised and four reported for the first time. For one of the systems with a new orbit, G 161-7, we determine masses of 0.156 +/- 0.011 and 0.1175 +/-0.0079 \msun for the A and B components, respectively. All six of these new calculated orbits have short periods between five and thirty-eight years and hold the promise of deriving accurate masses in the near future. For many other pairs we can establish their nature as physical or chance alignment depending on their relative motion. Of the 80 systems, 32 have calculated orbits, 25 others are physical pairs, 4 are optical pairs and 19 are currently unknown.

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arXiv2017

Speckle Interferometry at the U.S. Naval Observatory. XXII

The results of 4,747 intensified CCD observations of double stars, made with the 26-inch refractor of the U.S. Naval Observatory, are presented. Each observation of a system represents a combination of over two thousand short-exposure images. These observations are averaged into 2,667 mean relative positions and range in separation from 0.328" to 95.9", with a median separation of 8.673". Four orbits are improved. This is the 22nd in this series of papers and covers the period 4 January 2016 through 29 December 2016.

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arXiv2017

Binary Star Orbits. V. The Nearby White Dwarf - Red Dwarf pair 40 Eri BC

A new relative orbit solution with new dynamical masses is determined for the nearby white dwarf - red dwarf pair 40 Eri BC. The period is 230.09+/-0.68y. It is predicted to close slowly over the next half-century getting as close as 1.32" in early 2066. We determine masses of 0.575+/-0.018 $m_\odot$ for the white dwarf and 0.2041+/-0.0064 $m_\odot$ for the red dwarf companion. The inconsistency of the masses determined by gravitational redshift and dynamical techniques, due to a premature orbit calculation, no longer exists.

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arXiv2017

The Sirius System and its Astrophysical Puzzles: Hubble Space Telescope and Ground-Based Astrometry

Sirius, the seventh-nearest stellar system, is a visual binary containing the metallic-line A1 V star Sirius A, brightest star in the sky, orbited in a 50.13-year period by Sirius B, the brightest and nearest white dwarf (WD). Using images obtained over nearly two decades with the Hubble Space Telescope (HST), along with photographic observations covering almost 20 years, and nearly 2300 historical measurements dating back to the 19th century, we determine precise orbital elements for the visual binary. Combined with the parallax and the motion of the A component, these elements yield dynamical masses of 2.063+/-0.023 Msun and 1.018+/-0.011 Msun for Sirius A and B, respectively. Our precise HST astrometry rules out third bodies orbiting either star in the system, down to masses of ~15-25 Mjup. The location of Sirius B in the H-R diagram is in excellent agreement with theoretical cooling tracks for WDs of its dynamical mass, and implies a cooling age of ~126 Myr. The position of Sirius B in the mass-radius plane is also consistent with WD theory, assuming a carbon-oxygen core. Including the pre-WD evolutionary timescale of the assumed progenitor, the total age of Sirius B is about 228+/-10 Myr. We calculated evolutionary tracks for stars with the dynamical mass of Sirius A, using two independent codes. We find it necessary to assume a slightly sub-solar metallicity, of about 0.85 Zsun, to fit its location in the luminosity-radius plane. The age of Sirius A based on these models is about 237-247 Myr, with uncertainties of +/-15 Myr, consistent with that of the WD companion. We discuss astrophysical puzzles presented by the Sirius system, including the probability that the two stars must have interacted in the past, even though there is no direct evidence for this, and the orbital eccentricity remains high.

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arXiv2017

Continued Kinematic and Photometric Investigations of Hierarchical Solar-Type Multiple Star Systems

We observed 15 of the solar-type binaries within 67 pc of the Sun previously observed by the Robo-AO system in the visible, with the PHARO near-IR camera and the PALM-3000 adaptive optics system on the 5 m Hale telescope. The physical status of the binaries is confirmed through common proper motion and detection of orbital motion. In the process we detected a new candidate companion to HIP 95309. We also resolved the primary of HIP 110626 into a close binary making that system a triple. These detections increase the completeness of the multiplicity survey of the solar-type stars within 67 pc of the Sun. Combining our observations of HIP 103455 with archival astrometric measurements and RV measurements, we are able to compute the first orbit of HIP 103455 showing that the binary has a 68 yr period. We place the components on a color-magnitude diagram and discuss each multiple system individually.

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arXiv2016

The National Science Foundation's AST Portfolio Review of 2012 is Not Relevant to the Green Bank Telescope of 2017: A White Paper

The National Science Foundation (NSF) Astronomy Division's Portfolio Review of 2012 is no longer relevant to the Green Bank Telescope (GBT) of 2017 for two principal reasons, one instrumental and the other astrophysical: 1) The GBT has begun significant operations in the 3mm band, giving it unrivaled capabilities for spectroscopy and continuum studies over 67-116 GHz. It is now an instrument that is unique worldwide and is a critical complement to ALMA for the U.S. scientific community. These capabilities had not been implemented at the time of the review. 2) The detection of gravitational radiation by LIGO in 2015 places the GBT's work on pulsar observations of nano-Hz gravitational radiation at the forefront of modern astrophysics. The Green Bank Telescope of 2017 is not the GBT that was reviewed by the Eisenstein-Miller committee in 2012, a review that was specific to the NSF Astronomy portfolio. The GBT serves a wide spectrum of science areas including physics, chemistry, and planetary studies as well as astronomy. Besides its well-documented intellectual merit, it thus has a significant broader impact. The GBT is making significance advances in our understanding of gravitational waves, the equation-of-state of nuclear matter, the mass of supermassive black holes, the value of H0, and the physics of star-formation, all key science goals for astronomy identified in a recent National Academy study "New Worlds, New Horizons: A Midterm Assessment". In the era of ALMA and LIGO, other countries have bolstered their mm-wave and cm-wave facilities; it is critical that U.S. scientists have ready access to a large filled aperture to remain at the forefront of research.

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arXiv2016

Nominal values for selected solar and planetary quantities: IAU 2015 Resolution B3

In this brief communication we provide the rationale for, and the outcome of the International Astronomical Union (IAU) resolution vote at the XXIX-th General Assembly in Honolulu, Hawaii, in 2015, on recommended nominal conversion constants for selected solar and planetary properties. The problem addressed by the resolution is a lack of established conversion constants between solar and planetary values and SI units: a missing standard has caused a proliferation of solar values (e.g., solar radius, solar irradiance, solar luminosity, solar effective temperature and solar mass parameter) in the literature, with cited solar values typically based on best estimates at the time of paper writing. As precision of observations increases, a set of consistent values becomes increasingly important. To address this, an IAU Working Group on Nominal Units for Stellar and Planetary Astronomy formed in 2011, uniting experts from the solar, stellar, planetary, exoplanetary and fundamental astronomy, as well as from general standards fields to converge on optimal values for nominal conversion constants. The effort resulted in the IAU 2015 Resolution B3, passed at the IAU General Assembly by a large majority. The resolution recommends the use of nominal solar and planetary values, which are by definition exact and are expressed in SI units. These nominal values should be understood as conversion factors only, not as the true solar/planetary properties or current best estimates. Authors and journal editors are urged to join in using the standard values set forth by this resolution in future work and publications to help minimize further confusion.

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arXiv2016

Characterization of the Companion to $μ$ Her

$μ$ Her is a nearby quadruple system with a G-subgiant primary and several low mass companions arranged in a 2+2 architecture. While the BC components have been well characterized, the Ab component has been detected astrometrically and with direct imaging but there has been some confusion over its nature, in particular whether the companion is stellar or substellar. Using near-infrared spectroscopy we are able to estimate the spectral type of the companion as a M4$\pm$1V star. In addition, we have measured the astrometry of the system for over a decade. We combined the astrometry with archival radial velocity measurements to compute an orbit of the system. From the combined orbit, we are able to compute the mass sum of the system. Using the estimated mass of the primary, we estimate the mass of the secondary as 0.32 M_sun, which agrees with the estimated spectral type. Our computed orbit is preliminary due to the incomplete orbital phase coverage, but it should be sufficient to predict ephemerides over the next decade.

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arXiv2016

Speckle interferometry at SOAR in 2015

The results of speckle interferometric observations at the SOAR telescope in 2015 are given, totalling 1303 measurements of 924 resolved binary and multiple stars and non-resolutions of 260 targets. The separations range from 12 mas to 3.37" (median 0.17"); the maximum measured magnitude difference is 6.7 mag. We resolved 27 pairs for the first time, including 10 as inner or outer subsystems in previously known binaries, e.g. the 50-mas pair in Epsilon Cha. Newly resolved pairs are commented upon. We discuss three apparently non-hierarchical systems discovered in this series, arguing that their unusual configuration results from projection. The resolved quadruple system HIP 71510 is studied as well.

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