Binaries play a critical role in the formation, evolution, and fundamental properties of planets, stars, and stellar associations. Observational studies in these areas often include a mix of observations aimed at detecting or ruling out the presence of stellar companions. Rarely can non-detections rule out all possible binary configurations. Here we present MOLUSC, our framework for constraining the range of properties of unseen companions using astrometric, imaging, and velocity information. We showcase the use of MOLUSC on a number of systems, ruling out stellar false positives in the signals of HIP67522b, and DS Tuc Ab. We also demonstrate how MOLUSC could be used to predict the number of missing companions in a stellar sample using the ZEIT sample of young planet hosts. Although our results are not significant, with a larger sample MOLUSC could be used to see if close-in planets are less common in young binary systems, as is seen for their older counterparts.
Single-line spectroscopic binaries recently contribute to the stellar-mass black hole discovery, independently of the X-ray transient method. We report the identification of a single-line binary system LTD064402+245919, with an orbital period of 14.50 days. The observed component is a subgiant with a mass of 2.77$\pm$0.68M$_{\odot}$, radius 15.5$\pm$2.5R$_{\odot}$, effective temperature $T_{\rm eff}$ 4500$\pm$200K, and surface gravity log\emph{g} 2.5$\pm$0.25dex. The discovery makes use of the LAMOST time-domain (LAMOST-TD) and ZTF survey. Our general-purpose software pipeline applies the Lomb…
We present a new and computationally efficient method for characterizing very low mass companions using low resolution ($R\sim$30) near-infrared ($YJH$) spectra from high contrast imaging campaigns with integral field spectrograph (IFS) units. We conduct a detailed quantitative comparison of the efficacy of this method through tests on simulated data comparable in spectral coverage and resolution to the currently operating direct imaging systems around the world. In particular, we simulate Project 1640 data as an example of the use, accuracy, and precision of this technique. We present results…
In this paper, we develop a spectral differential technique with which the dynamical mass of low-mass companions can be found. This method aims at discovering close companions to late-type stars by removing the stellar spectrum through a subtraction of spectra obtained at different orbital phases and discovering the companion spectrum in the difference spectrum in which the companion lines appear twice (positive and negative signal). The resulting radial velocity difference of these two signals provides the true mass of the companion, if the orbital solution for the radial velocities of the pr…
Barium stars are one of the important probes to understand the origin and evolution of slow neutron-capture process elements in the Galaxy. These are extrinsic stars, where the observed s-process element abundances are believed to have an origin in the now invisible companions that produced these elements at their Asymptotic Giant Branch phase of evolution. We have attempted to understand the s-process nucleosynthesis, as well as the physical properties of the companion stars through a detailed comparison of observed elemental abundances of 10 barium stars with the predictions from AGB nucleos…
GQ Lup B is a young and accreting, substellar companion that appears to drive a spiral arm in the circumstellar disk of its host star. We report high-contrast imaging observations of GQ Lup B with VLT/NACO at 4-5 $μ$m and medium-resolution integral field spectroscopy with VLT/MUSE. The optical spectrum is consistent with an M9 spectral type, shows characteristics of a low-gravity atmosphere, and exhibits strong H$α$ emission. The $H-M'$ color is $\gtrsim$1 mag redder than field dwarfs with similar spectral types and a detailed analysis of the spectral energy distribution (SED) from optical to …
Radio astrometry of nearby, low-mass stars has the potential to be a powerful tool for the discovery and characterization of planetary companions. We present a Very Large Array survey of 172 active M dwarfs at distances of less than 10 pc. Twenty nine stars were detected with flux densities greater than 100 microJy. We observed 7 of these stars with the Very Long Baseline Array at milliarcsecond resolution in three separate epochs. With a detection threshold of 500 microJy in images of sensitivity 1 sigma ~ 100 microJy, we detected three stars three times (GJ 65B, GJ896A, GJ 4247), one star tw…
The percentage of massive main sequence OB stars in binary systems is thought to be as high as 100%. However, very few Galactic binary red supergiants (RSGs) have been identified, despite the fact that these stars are the evolved descendants of OB stars. As shown in our recent paper, binary RSGs will likely have B-type companions, as dictated by stellar evolution considerations. Such a system will have a very unique photometric signature due to the shape of the spectral energy distribution. Using photometric cutoffs it should therefore be possible to detect candidate RSG+B star binary systems.…
A major outstanding question regarding the formation of planetary systems is whether wide-orbit giant planets form differently than close-in giant planets. We aim to establish constraints on two key parameters that are relevant for understanding the formation of wide-orbit planets: 1) the relative mass function and 2) the fraction of systems hosting multiple companions. In this study, we focus on systems with directly imaged substellar companions, and the detection limits on lower-mass bodies within these systems. First, we uniformly derive the mass probability distributions of known companion…
All transiting planet observations are at risk of contamination from nearby, unresolved stars. Blends dilute the transit signal, causing the planet to appear smaller than it really is, or produce a false positive detection when the target star is blended with an eclipsing binary. High spatial resolution adaptive optics images are the best way of resolving undetected contaminants. Here we present companions and detection limits for 12 Kepler candidates, of which 4 have companions within 4 arcsec. One system (KOI 1537) consists of two similar-magnitude stars separated by 0.1 arcsec, while KOI 17…
TESS has proven to be a powerful resource for finding planets, including those that orbit the most prevalent stars in our galaxy: the M dwarfs. Identification of stellar companions (both bound and unbound) has become a standard component of the transiting planet confirmation process in order to assess the level of light curve dilution and the possibility of the target being a false positive. Studies of stellar companions have also enabled investigations into stellar multiplicity in planet-hosting systems, which has wide-ranging implications for both exoplanet detection and characterization, as…
Detecting and Characterizing Companions with a Calibrated Gaia DR2, DR3, and Hipparcos Catalog (G23H)
NRC Herzberg Astronomy and Astrophysics（国家研究委员会赫茨伯格天文学与天体物理学研究所）；Department of Physics and Astronomy, University of Victoria（维多利亚大学物理与天文系）；Heising-Simons Foundation（海辛-西蒙斯基金会）；Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles（加州大学洛杉矶分校地球、行星与空间科学系）；Department of Physics, University of California, Santa Barbara（加州大学圣塔芭芭拉分校物理系）；Department of Astronomy & Astrophysics, University of California, San Diego（加州大学圣地亚哥分校天文与天体物理学系）；Department of Astronomy, New Mexico State University（新墨西哥州立大学天文系）
The Transiting Exoplanet Survey Satellite (TESS) is conducting a two-year wide-field survey searching for transiting exoplanets around nearby bright stars that will be ideal for follow-up characterization. To facilitate studies of planet compositions and atmospheric properties, accurate and precise planetary radii need to be derived from the transit light curves. Since 40 - 50% of exoplanet host stars are in multiple star systems, however, the observed transit depth may be diluted by the flux of a companion star, causing the radius of the planet to be underestimated. High angular resolution im…
CoRoT-2 is one of the most unusual planetary systems known to date. Its host star is exceptionally active, showing a pronounced, regular pattern of optical variability caused by magnetic activity. The transiting hot Jupiter, CoRoT-2b, shows one of the largest known radius anomalies. We analyze the properties and activity of CoRoT-2A in the optical and X-ray regime by means of a high-quality UVES spectrum and a 15 ks Chandra exposure both obtained during planetary transits. The UVES data are analyzed using various complementary methods of high-resolution stellar spectroscopy. We characterize th…
It has been suggested that besides stellar companions, substellar objects in close orbits may be able to trigger mass loss in a common envelope phase and form hot subdwarfs. In an ongoing project we search for close substellar companions combining time resolved high resolution spectroscopy with photometry. We determine the fraction of as yet undetected radial velocity variable systems from a sample of 27 apparently single sdB stars to be 16%. We discovered low-mass stellar companions to the He-sdB CPD-20 1123 and the pulsator KPD 0629-0016. The brown dwarf reported to orbit the eclipsing binar…
Because of the diversity of stellar masses and orbital sizes of binary systems, and the complex interaction between star-star, star-planet and planet-planet, it has been difficult to fully characterize the planetary systems associated with binary systems. Here, we report high-precision astrometric observations of the low-mass binary system GJ 896AB, revealing the presence of a Jupiter-like planetary companion (GJ 896Ab). The planetary companion is associated to the main star GJ 896A, with an estimated mass of 2.3 Jupiter masses and an orbit period of 284.4 days. A simultaneous analysis of the …
Massive stars in binaries can give rise to extreme phenomena such as X-ray binaries and gravitational wave sources after one or both stars end their lives as core-collapse supernovae. Stars in close orbit around a stellar or compact companion are expected to explode as "stripped-envelope supernovae", showing no (Type Ib/c) or little (Type IIb) signs of hydrogen in the spectra, because hydrogen-rich progenitors are too large to fit. The physical processes responsible for the stripping process and the fate of the companion are still very poorly understood. Aiming to find new clues, we investigat…
We conducted speckle imaging observations of 53 stellar systems that were members of long-term radial velocity (RV) monitoring campaigns and exhibited substantial accelerations indicative of planetary or stellar companions in wide orbits. Our observations were made with blue and red filters using the Differential Speckle Survey Instrument at Gemini-South and the NN-Explore Exoplanet Stellar Speckle Imager at the WIYN telescope. The speckle imaging identifies eight luminous companions within two arcseconds of the primary stars. In three of these systems (HD 1388, HD 87359, and HD 104304), the p…
The stellar initial mass function (IMF) is a key property of stellar populations. There is growing evidence that the classical star-formation mechanism by the direct cloud fragmentation process has difficulties reproducing the observed abundance and binary properties of brown dwarfs and very-low-mass stars. In particular, recent analytical derivations of the stellar IMF exhibit a deficit of brown dwarfs compared to observational data. Here we derive the residual mass function of brown dwarfs as an empirical measure of the brown dwarf deficiency in recent star-formation models with respect to o…
The Demographics of Binary Companions to Stripped-Envelope Supernovae: Confronting Observations with Population Synthesis
Foundation for Research and Technology（研究与技术基金会）；Space Telescope Science Institute（太空望远镜科学研究所）；University of Toronto（多伦多大学）；Carnegie Institution for Science（卡内基科学促进会）；Northwestern University（西北大学）；Caltech/IPAC（加州理工学院/IPAC）；University of Washington（华盛顿大学）
We present an updated analysis of LHS 6343, a triple system in the Kepler field which consists of a brown dwarf transiting one member of a widely-separated M+M binary system. By analyzing the full Kepler dataset and 34 Keck/HIRES radial velocity observations, we measure both the observed transit depth and Doppler semiamplitude to 0.5% precision. With Robo-AO and Palomar/PHARO adaptive optics imaging as well as TripleSpec spectroscopy, we measure a model-dependent mass for LHS 6343 C of 62.1 +/- 1.2 M_Jup and a radius of 0.783 +/- 0.011 R_Jup. We detect the secondary eclipse in the Kepler data …
HD 8673 hosts a massive exoplanet in a highly eccentric orbit (e=0.723). Based on two epochs of speckle interferometry a previous publication identified a candidate stellar companion. We observed HD 8673 multiple times with the 10 m Keck II telescope, the 5 m Hale telescope, the 3.63 m AEOS telescope and the 1.5m Palomar telescope in a variety of filters with the aim of confirming and characterizing the stellar companion. We did not detect the candidate companion, which we now conclude was a false detection, but we did detect a fainter companion. We collected astrometry and photometry of the c…
We present the TESS discovery of the LHS 1678 (TOI-696) exoplanet system, comprised of two approximately Earth-sized transiting planets and a likely astrometric brown dwarf orbiting a bright ($V_J$=12.5, $K_s$=8.3) M2 dwarf at 19.9 pc. The two TESS-detected planets are of radius 0.70$\pm$0.04 $R_\oplus$ and 0.98$\pm$0.06 $R_\oplus$ in 0.86-day and 3.69-day orbits, respectively. Both planets are validated and characterized via ground-based follow-up observations. HARPS RV monitoring yields 97.7 percentile mass upper limits of 0.35 $M_\oplus$ and 1.4 $M_\oplus$ for planets b and c, respectively.…
Within the NaCo-ISPY exoplanet imaging program, we aim at detecting and characterizing the population of low-mass companions at wide separations ($\gtrsim$10AU), focusing in particular on young stars either hosting a known protoplanetary disk or a debris disk. R CrA is one of the youngest (1-3 Myr) and most promising objects in our sample because of two previous studies that suggested the presence of a close companion. Our aim is to directly image and characterize the companion for the first time. We observed R CrA twice with the NaCo instrument at VLT in the $L'$ filter with a one year time b…
Variability in the time series brightness of a star on a timescale of 8 hours, known as 'flicker', has been previously demonstrated to serve as a proxy for the surface gravity of a star by Bastien et al. (2013). Although surface gravity is crucial for stellar classification, it is the mean stellar density which is most useful when studying transiting exoplanets, due to its direct impact on the transit light curve shape. Indeed, an accurate and independent measure of the stellar density can be leveraged to infer subtle properties of a transiting system, such as the companion's orbital eccentric…
Directly imaged planets and substellar companions are key targets for the characterization of self-luminous atmospheres. Their photometric appearance at 4-5 $μ$m is sensitive to the chemical composition and cloud content of their atmosphere. We aim at systematically characterizing the atmospheres of directly imaged low-mass companions at 4-5 $μ$m. We want to homogeneously process the data and compile a photometric library at thermal wavelengths of these mostly young, low-gravity objects. In this way, we want to find trends related to their spectral type and surface gravity by comparing with is…
We used the Project 1640 near-infrared coronagraph and integral field spectrograph to observe 19 young solar type stars. Five of these stars are known binary stars and we detected the late-type secondaries and were able to measure their JH spectra with a resolution of R\sim30. The reduced, extracted, and calibrated spectra were compared to template spectra from the IRTF spectral library. With this comparison we test the accuracy and consistency of spectral type determination with the low-resolution near-infrared spectra from P1640. Additionally, we determine effective temperature and surface g…
With the development of extreme high contrast ground-based adaptive optics instruments and space missions aimed at detecting and characterizing Jupiter- and terrestrial-mass planets, it is critical that each target star be thoroughly vetted to determine whether it is a viable target given both the instrumental design and scientific goals of the program. With this in mind, we have conducted a high contrast imaging survey of mature AFGKM stars with the PALAO/PHARO instrument on the Palomar 200 inch telescope. The survey reached sensitivities sufficient to detect brown dwarf companions at separat…
Using numerical modeling and a grid of synthetic spectra, we examine the effects that unresolved binaries have on the determination of various stellar atmospheric parameters for SEGUE targets measured using the SEGUE Stellar Parameter Pipeline (SSPP). To model undetected binaries that may be in the SEGUE sample, we use a variety of mass distributions for the primary and secondary stars in conjunction with empirically determined relationships for orbital parameters to determine the fraction of G-K dwarf stars, as defined by SDSS color cuts, that will be blended with a secondary companion. We fo…
Characterizing the Post-Red Supergiant binary system AFGL 4106 and its complex nebula with SPHERE/VLT
Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange（蔚蓝海岸大学、蔚蓝海岸天文台、法国国家科学研究中心、拉格朗日实验室）；Departamento de Física, Universidad de Santiago de Chile（圣地亚哥德智利大学物理系）；Center for Interdisciplinary Research in Astrophysics and Space Exploration (CIRAS), USACH（天体物理学与太空探索跨学科研究中心（CIRAS））；Royal Observatory of Belgium（比利时皇家天文台）；School of Physics & Astronomy, University of Leeds（利兹大学物理与天文学学院）
We present a method to characterize statistically the parameters of a detached binary sample - binary fraction, separation distribution, and mass ratio distribution - using noisy radial-velocity data with as few as two, randomly spaced, epochs per object. To do this, we analyze the distribution of DRVmax, the maximum radial-velocity difference between any two epochs for the same object. At low values, the core of this distribution is dominated by measurement errors, but for large enough samples there is a high-velocity tail that can effectively constrain the parameters of the binary population…
