arXiv subjects

Andrei Tokovinin

Publications and source records attributed to Andrei Tokovinin.

At least 19 recordsLinked to original sources

arXiv2026

SOAR TESS Survey III: Mapping the Stellar Companion Deficit around TESS Planet Candidates

We present the cumulative SOAR TESS Survey, based on HRCam speckle observations of 2,982 targets, and report 433 companion measurements obtained after Survey II. In a demographic sample of 1,199 dwarf primaries, we compare detected companions with secondary-to-primary mass ratios $q=M_2/M_1\geq0.4$ to a field-star population after accounting for each observation's detection limits. We find 24 companions within 50 au versus 84.8 expected and 48 within 100 au versus 124.4 expected. The companion frequencies relative to the field expectation are $S_{50\,{\rm au}}=0.291^{+0.062}_{-0.054}$ and $S_{100\,{\rm au}}=0.391^{+0.058}_{-0.053}$. A continuous model in which the deficit weakens with separation reaches the midpoint between close-binary suppression and the field rate at $a_{50}=74$ au (57--101 au). The Gaia-matched subset contains 88 companions versus 69.6 expected, a difference consistent with the model once uncertainties in the field comparison and Gaia selection are included. A model that preserves the total number of binaries but shifts the field distribution toward 100 au fits poorly. Under the limiting assumption that all retained planets orbit the catalog primary, the fitted law implies reductions of 17.0\% in volume-limited planet yield over $q\geq0.4$ and 23.3\% when extended to all mass ratios. M-dwarf hosts show a similar close-companion deficit, but the smaller sample prevents a precise comparison with solar-type hosts.

astro-ph.EP↗

arXiv2026

Study of Vibrations at SOAR

The 4.1-m Southern Astrophysics Research (SOAR) telescope in Chile resembles larger optical telescopes by its thin actively controlled primary mirror, built-in tip-tilt correction, lightweight structure, and adaptive optics (AO) turbulence correction. The non-stationary vibration of the SOAR optical axis with a frequency of 50 Hz and an amplitude reaching 20-30 mas has been detected by the AO system, degrading the quality of optical speckle interferometric data. Accelerometers revealed that the 50 Hz tremor, driven by an external source, propagates within telescope structure and is strongly amplified by the response of the fast tip-tilt mirror servo system, producing characteristic elliptical beam path. The AO system also evidenced periodic components at 47 Hz in the defocus (matching the frequency of fans in electronic racks and computers) and at ~65 Hz in the astigmatism. The latter is associated with structural resonances of the SOAR primary mirror support, apparently excited by the wind. Periodic tracking errors with typical frequencies of 0.5-2.5 Hz are mostly caused by periodic errors of the encoders, depending on their alignment, and can be amplified by the mount servo at fast tracking rates. Vibration characterization at SOAR informs similar studies at other telescopes.

astro-ph.IM↗

arXiv2026

Operational capabilities and on-sky performance of SAMOS at the completion of science commissioning

We present the operational capabilities and on-sky performance of the SOAR Adaptive Module Optical Spectrograph (SAMOS) at the completion of its science commissioning phase. SAMOS is a Digital Micromirror Device (DMD)-based multi-object spectrograph and imager installed behind the SOAR Adaptive Module (SAM) ground-layer adaptive optics system. The instrument relays the full 3 x 3 arcmin AO-corrected field onto a large-format DMD, where each micromirror can direct light to either a spectroscopic or a parallel imaging channel. This architecture enables programmable slit-mask patterns that can be generated and reconfigured within seconds. SAMOS provides low-resolution spectroscopy over the 4000-10000 A wavelength range at resolving power R ~ 2500 and high-resolution spectroscopy (R ~ 10,000) in the 4500-5150 A and 6 000-7000 A bands. We summarize the operational workflow established during commissioning, including target acquisition, astrometric registration, DMD slit-mask generation, simultaneous imaging and spectroscopy, and automated data reduction. Science-verification observations demonstrate accurate target acquisition, reliable programmable slit-mask operation, multiplexed spectroscopy of crowded stellar fields, wavelength-calibration accuracy of about 0.3 A, and end-to-end spectrophotometric calibration through the combination of imaging and spectroscopic data. These results establish SAMOS as a unique facility instrument that combines adaptive-optics-assisted imaging, programmable multi-object spectroscopy, and rapid slit-mask reconfiguration for efficient spectroscopic surveys, transient follow-up, and studies of crowded stellar populations.

astro-ph.IM↗

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.

astro-ph.SR↗

arXiv2026

The Solar Neighborhood LIV: 54 Orbits of M Dwarf Multiples within 30 Parsecs with Speckle Interferometry at SOAR

We present 1066 speckle measurements of M dwarf multiples observed over 2021-2024, all taken with HRCam on the Southern Astrophysical Research 4.1 m telescope. Among these, 900 observations resolve companions in 212 pairs, with separations spanning 17 milliarcseconds to 3.4 arcsec and brightness differences ranging from 0 to 4.9 magnitudes in the I filter. We have characterized the orbits of 54 of these companions, spanning periods of 0.67-30 yr, by combining our data with literature astrometry, radial velocities, and, in four cases, Hipparcos-Gaia accelerations. Among the orbits presented here are 28 that are the first-ever such characterizations for their systems, and 26 that revise previously-published orbits, thus providing a significant update to the observed dynamics of M dwarfs in the solar neighborhood. From these orbits, we provide new and updated dynamical total masses for these systems, precise to 0.7-7% in nearly all cases. Future mass derivations for components in these systems will contribute to efforts in refining the mass-luminosity relation for the smallest stars, and will enhance investigations of age, magnetism, and metallicity effects on luminosities at a given mass.

astro-ph.SR↗

arXiv2026

Mutual Orbit Alignment in Resolved Triple Systems

A sample of 278 triple systems with outer separations under 300 au and resolved inner pairs is studied, focusing on the mutual alignment between inner and outer orbits. The degree of alignment increases with (i) decreasing outer separation, (ii) decreasing ratio of outer and inner separations, (iii) decreasing mass of the inner primary component, and (iv) increasing inner mass ratio. There is no dependence on the outer mass ratio. The average mutual inclination is ~40deg for the full sample and ~10deg for 38 triples with primary components less massive than 1 solar and outer separations below 50 au. Inner eccentricities in aligned triples are smaller compared to misaligned ones. In another sample of 371 hierarchies with known outer orbits and inner eclipsing subsystems, only 22% show mutual alignment within 20deg, while the rest are aligned randomly. These findings match qualitatively current understanding of the formation of hierarchical systems, where the N-body dynamics dominates at large scales, while the accretion and migration shape systems closer than $\sim$100 au. Fragmentation of isolated cores apparently produces approximately aligned low-mass hierarchies.

astro-ph.SR↗

arXiv2025

Orbits of Twelve Multiple Stars

Inner and outer orbits in twelve hierarchical stellar systems are determined using high-resolution speckle imaging, radial velocities, or both. Masses and fluxes of the components are estimated. The Hipparcos numbers of the main stars are 7111, 12912, 17895, 20375, 42424, 68717, 77439, 79076, 90253, 97922, and 102855; the faint triple WDS J10367+1522 has no HIP number. Four systems are quadruple of 3+1 hierarchy, the rest are triple. Two triples with low-mass M-type components are approximately planar, with moderately eccentric orbits and near-unit mass ratios. The shortest inner period of 0.27d is found in the newly identified contact eclipsing pair belonging to the misaligned quadruple HIP 97922. The compact system HIP 102855 (periods 15.4 and 129 days) identified by Gaia is confirmed here and has additional companion at 6 arcseconds. This work contributes new data for the study of diverse architectures of stellar hierarchies in the field.

astro-ph.SR↗

arXiv2025

Characterizing TESS-Identified Quadruple and Higher Order Eclipsing Binaries: I. Speckle Imaging with DSSI and HRCam

NASA's TESS mission has unveiled a plethora of eclipsing binaries (EBs), among them hundreds of triples and higher order, hierarchical systems. These complex targets require follow-up observations to enable full characterization of system architectures and identify the most compact multiples expected to undergo the most dramatic dynamical evolution. We report first results from a long-term effort to perform such follow-up, focusing here on multi-band speckle imaging of a majority, 57, of the sample of 97 quadruple and higher order eclipsing binaries (Q+EBs) identified via TESS light curves by V. B. Kostov et al. (2022). Diffraction-limited imaging with the Differential Speckle Survey Instrument (DSSI) on the ARC 3.5-meter telescope and HRCam on the SOAR 4.1-m telescope reveals nearly 60% of the 57 to resolve into two sources separated by $\geq$ 0.03 arcseconds. For these partly resolved systems, we report derived characteristics (e.g., relative position angle, angular separation, and magnitude differences in multiple passbands) from the speckle imaging. We find those Q+EBs partly resolved with 4-m class telescopes to have significantly inflated Gaia parallax errors and large Gaia RUWE, particularly for systems with separations comparable to Gaia's resolution limit (~0.6 arcseconds). For unresolved systems we report upper limits on angular and linear projected separations. We find two partly resolved Q+EBs with wide linear separations having eclipse timing variations that are therefore candidates of higher than quadruple multiplicity. Finally, we demonstrate how speckle imaging of resolved Q+EBs during an eclipse can clarify which speckle-resolved Q+EB subsystem is associated with a particular set of TESS eclipses.

astro-ph.SR↗

arXiv2025

Spectroscopic Orbits of Subsystems in Multiple Stars. XI

Adding to the large radial velocity survey of nearby solar-type stars (summary in Tokovinin, 2023a), spectroscopic orbits are determined for four hierarchical systems: HIP 49442 (inner and outer periods of 164.55 d and 34 yr, respectively), HIP 55691 (2.4 and 415 yr), HIP 61465 (86.8 d), and HIP 78662C (0.82 d). Each system is discussed individually. Seven Gaia orbits of low-mass dwarfs, each with two additional resolved (interferometric and wide) companions, i.e. potential quadruples, are tested by monitoring radial velocities; five orbits are confirmed and two are refuted. Five of these systems are quadruples of 3+1 hierarchy, one is quintuple, and one is triple. Strengths and limitations of the Gaia data on multiple systems and the need of complementary observations are highlighted.

astro-ph.SR↗

arXiv2025

Southern binaries with the Zorro Speckle Camera @ Gemini-South

We present measurements in the context of a survey of southern hemisphere binary and multiple stellar systems observed with the Zorro Speckle dual diffraction-limited optical imaging camera on the 8.1m Gemini-South telescope carried out between 2019 and 2023. The overall motivation of our survey, as well as some initial results of these observations, are outlined to demonstrate the capabilities - and limitations - of Zorro. We report on the astrometric characterization of the instrument in terms of the precision and accuracy of our measurements and provide details of our custom-made data reduction pipeline. For targets with separations smaller than 0.4 arcsec, an overall precision of 1 mas in the radial and tangential directions is obtained, while the uncertainty in position angle is 0.2 deg. Relative astrometry and contrast brightness in the two Zorro filters at 562 and 832 nm are reported for 70 pairs on 64 distinct systems (six are triples). Eleven new binaries are found, mostly of small separations (down to 15 mas), and large brightness contrast (up to Delta m=6 in the red channel). Our results indicate that the Zorro instrument, when properly calibrated, delivers excellent quality data for visual binary studies of tight and/or faint companions.

astro-ph.SR↗

arXiv2025

The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems III: Aperture Masking Interferometric Observations of the star HIP 65426 at 3.8 um

We present aperture masking interferometry (AMI) observations of the star HIP 65426 at $3.8\,\rm{μm}$ as a part of the JWST Direct Imaging Early Release Science (ERS) program obtained using the Near Infrared Imager and Slitless Spectrograph (NIRISS) instrument. This mode provides access to very small inner working angles (even separations slightly below the Michelson limit of $0.5λ/D$ for an interferometer), which are inaccessible with the classical inner working angles of the JWST coronagraphs. When combined with JWST's unprecedented infrared sensitivity, this mode has the potential to probe a new portion of parameter space across a wide array of astronomical observations. Using this mode, we are able to achieve a $5σ$ contrast of $Δm{\sim}7.62{\pm}0.13$ mag relative to the host star at separations ${\gtrsim}0.07{"}$, and the contrast deteriorates steeply at separations ${\lesssim}0.07{"}$. However, we detect no additional companions interior to the known companion HIP 65426 b (at separation ${\sim}0.82{"}$ or, $87^{+108}_{-31}\,\rm{au}$). Our observations thus rule out companions more massive than $10{-}12\,\rm{M_{Jup}}$ at separations ${\sim}10{-}20\,\rm{au}$ from HIP 65426, a region out of reach of ground or space-based coronagraphic imaging. These observations confirm that the AMI mode on JWST is sensitive to planetary mass companions at close-in separations (${\gtrsim}0.07{"}$), even for thousands of more distant stars at $\sim$100 pc, in addition to the stars in the nearby young moving groups as stated in previous works. This result will allow the planning and successful execution of future observations to probe the inner regions of nearby stellar systems, opening an essentially unexplored parameter space.

astro-ph.EP↗

arXiv2025

Orbits of Six Triple Systems

Joint analysis of position measurements and radial velocities of six triple stellar systems is conducted to determine their inner and/or outer orbits. Accumulation of such data is needed to study the architecture of stellar hierarchies and its relation to the formation mechanisms. The inner periods in the six systems (HIP 11783, 64836, 72423, 84720, 89234, and 105404) range from 0.5 days to 44 yr. The shortest outer period of 3.34 yr is found in the compact triple HIP~105404 (BS Ind). The resolved triple system HIP 64836 has comparable inner and outer periods (5 and 30 yr), placing it near the limit of dynamical stability, while its quasi-circular and coplanar orbits suggest a 1:6 mean motion resonance. The periods in HIP 89234 (44 and ~450 yr) are also comparable, but the mutual orbit inclination is large, 54 degrees. Masses of the components are estimated and each system is discussed individually.

astro-ph.SR↗

arXiv2024

Searching for compact hierarchical triple systems candidates in astrometric binaries and accelerated solutions

Compact hierarchical triple (CHT) systems, where a tertiary component orbits an inner binary, provide critical insights into stellar formation and evolution. Despite their importance, the detection of such systems, especially compact ones, remains challenging due to the complexity of their orbital dynamics and the limitations of traditional observational methods. This study aims to identify new CHT star systems among Gaia astrometric binaries and accelerated solutions by analysing the radial velocity (RV) amplitude of these systems, thereby improving our understanding of stellar hierarchies. We selected a sample of bright astrometric binaries and accelerated solutions from the Gaia DR3 Non-Single Stars catalogue. The RV peak-to-peak amplitude was used as an estimator, and we applied a new method to detect potential triple systems by comparing the RV-based semi-amplitude with the astrometric semi-amplitude. We used available binary and triple star catalogues to identify and validate candidates, with a subset confirmed through further examination of the RV and astrometric data. Our analysis resulted in the discovery of 956 CHT candidates among the orbital sources as well as another 3,115 probable close binary sources in stars with accelerated solutions. Exploring the inclination, orbital period, and eccentricity of the outer companion in these CHT systems provides strong evidence of mutual orbit alignment, as well as a preference towards moderate outer eccentricities. Our novel approach has proven effective in identifying potential triple systems thereby increasing their number in the catalogues. Our findings emphasise the importance of combined astrometric and RV data analysis in the study of multiple star systems.

astro-ph.SR↗

arXiv2024

Orbits and masses in two triple systems

In an effort to determine accurate orbital and physical properties of a large number of bright stars, a method was developed to fit simultaneously stellar parameters (masses, luminosities, effective temperatures), distance, and orbits to the available data on multiple systems, namely the combined and differential photometry, positional measurements, radial velocities (RVs), accelerations, etc. The method is applied to a peculiar resolved triple system HIP 86286. The masses of its components estimated using observations and standard relations are 1.3, 0.9, and 0.9 Mmsun; the main star is a G8IV subgiant, while its two companions are main-sequence dwarfs. The inner and outer orbital periods are 35 and 287 years, respectively, and the orbits are nearly coplanar. The second system, HIP 117258, is an accelerating star with a resolved companion; its 35.7-yr orbit based on relative astrometry and precise RVs yields the secondary mass of 0.95 Msun, much larger than inferred from the photometry. The apparent paradox is explained by assuming that the secondary is a close pair of M-type dwarfs with yet unknown period.

astro-ph.SR↗

arXiv2024

Orbits of Binary Stars: from Visual Measures to Speckle Interferometry

Knowledge of the orbits of visual binary stars has always been one of the fundamentals of astronomy. Based historically on the visual measures, nowadays the orbits rely more (or exclusively) on the accurate speckle data. This prompts reconsideration of the methods of orbit calculation, undertaken here and illustrated by 20 examples, from accurate to drastically revised and tentative orbits. Good understanding and critical assessment of the input data is a key requirement, especially concerning visual measures. Combination of visual and speckle data is still needed for long-period binaries, but the relative weights must match their respective errors. When the orbit can be fully constrained only by accurate speckle data, the old measures should be ignored. Orbits can be classified into three grades: A - fully constrained, B - semi-constrained, and C - preliminary or tentative. Typical use cases of visual orbits are listed. Accurate parallaxes from Gaia, together with the orbits, will greatly expand the data on stellar masses. Continued speckle monitoring will be an essential complement to Gaia, but the vast amount of new pairs will restrict future work on orbits to the most interesting or relevant objects.

astro-ph.SR↗

arXiv2024

Performance of the Southern Astrophysical Research Telescope Speckle Instrument

The High Resolution Camera (HRCam) speckle imager at the 4.1 m Southern Astrophysical Research telescope is a highly productive instrument that has accumulated about 40K observations to date. Its performance (detected flux, level of the speckle signal, signal-to-noise ratio, and limiting magnitude) is studied here using both the actual data and realistic simulations, including the detector noise. In the calculation of the speckle power spectrum, signal clipping is essential to reduce the noise impact and maximize the sensitivity. Increasing exposure time of individual frames beyond 30 ms does not improve the limiting magnitude, which ranges from 11.5 to 14 mag under a seeing from 1.6" to 0.6" in the wide-band I filter. A gain of at least one magnitude is expected if the current electron multiplication CCD is replaced by a high-end CMOS detector with a sub-electron readout noise. This study will help in planning, executing, and automating future speckle observations with HRCam and other speckle imagers.

astro-ph.IM↗

arXiv2024

Verification of astrometrically accelerating stars from Hipparcos and Gaia: I. Methodology and application to HIP 44842

A large number of candidate binary stars with apparent acceleration on the sky has emerged from analysis of astrometric data collected by the Hipparcos, Tycho-2, and Gaia space missions. Although the apparent acceleration can serve as a relatively reliable indicator of binarity, it provides scarce information about the orbital and physical parameters of the components. With an emphasis on the search for stellar-mass black holes and neutron stars hidden in binary systems, we start a broader effort to characterize the most promising candidates using follow-up ground-based observations. Accurate quantification of orbital and physical parameters of systems with dim or invisible companions requires combination of Hipparcos, Gaia, and precision spectroscopic measurements. In this paper, we review the necessary steps in this implementation and describe the improved Hipparcos-Gaia sample of long-term astrometric accelerations which includes correction of sky-correlated systematic errors using the vector spherical decomposition method. As an example, we study one Hipparcos star with a large acceleration, HIP 44842, where the companion is revealed to be a normal main sequence star.

astro-ph.SR↗

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.

astro-ph.SR↗