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Register a new userA young spectroscopic binary in a quintuple system part of the Local Association
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Double-lined spectroscopic binaries (SB2) allow us to determine a lower limit of the masses of their components directly to test stellar models. In this work, our aim is to derive the orbital and physical parameters of GJ1284, a young SB2. We also revise the membership of this system and its two wide co-moving companions, GJ898 and GJ897AB, to a young moving group to assess, along with other youth indicators, their age. Afterwards, we compare the results from these analyses and the photometry of these systems with several pre-main-sequence evolutionary models. We determine the orbit of the GJ1284 system alongside its systemic velocity from high resolution spectra. Additionally, we use TESS photometry to derive the rotational period of the GJ1284 and its two wide companions. GJ1284 is a binary system located at approximately 16 pc with an eccentric orbit ($ e = 0.505 $) of 11.83 d period made up of an M2-M2.5 + M3-M3.5. The revised systemic velocity of $ gamma = 0.84 pm 0.14,mathrm{km,s}^{-1} $ suggests that it is a member of the Local Association. The kinematics together with other activity and youth indicators imply an age of 110-800 Myr for this system and its two companions. The isochronal ages derived from the comparison of the photometry with several evolutionary models are younger than the age estimated from the activity indicators for the three co-moving systems. The masses for the components of GJ1284, derived from their luminosity and age using the different models, are not consistent with the masses derived from the photometry, except for the PARSEC models, but are compatible with dynamical masses of double-lined eclipsing binaries with similar ages and spectral types. The effect of magnetic activity in the form of spots can reconcile to some extent the photometric and dynamical masses, but is not considered in most of the evolutionary models.
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Until now, HD 155448 has been known as a post-AGB star and listed as a quadruple system. In this paper, we study the system in depth and reveal that the B component itself is a binary and that the five stars HD 155448 A, B1, B2, C, and D likely form a comoving stellar system. From a spectroscopic analysis we derive the spectral types and find that all components are B dwarfs (A: B1V, B1: B6V, B2: B9V, C: B4Ve, D: B8V). Their stellar ages put them close to the ZAMS, and their distance is estimated to be ~2 kpc. Of particular interest is the C component, which shows strong hydrogen and forbidden emission lines at optical wavelengths. All emission lines are spatially extended in the eastern direction and appear to have a similar velocity shift, except for the [OI] line. In the IR images, we see an arc-like shape to the northeast of HD 155448 C. From the optical up to 10 micron, most circumstellar emission is located at distances between ~1.0 arcsec and 3.0 arcsec from HD 155448 C, while in the Q band the arc-like structure appears to be in contact with HD 155448 C. The Spitzer and VLT/VISIR mid-IR spectra show that the circumstellar material closest to the star consists of silicates, while polycyclic aromatic hydrocarbons (PAH) dominate the emission at distances >1 arcsec with bands at 8.6, 11.3, and 12.7 micron. We consider several scenarios to explain the unusual, asymmetric, arc-shaped geometry of the circumstellar matter. The most likely explanation is an outflow colliding with remnant matter from the star formation process.
To analyze the SACY (Search for Associations Containing Young stars) survey we developed a method to find young associations and to define their high probability members. These bona fide members enable to obtain the kinematical and the physical properties of each association in a proper way. Recently we noted a concentration in the UV plane and we found a new association we are calling ASYA (All Sky Young Association) for its overall distribution in the sky with a total of 38 bonafide members and an estimated age of 110 Myr, the oldest young association found in the SACY survey. We present here its kinematical, space and Li distributions and its HR diagram.
We present a quintuple star system that contains two eclipsing binaries. The unusual architecture includes two stellar images separated by 11 on the sky: EPIC 212651213 and EPIC 212651234. The more easterly image (212651213) actually hosts both eclipsing binaries which are resolved within that image at 0.09, while the westerly image (212651234) appears to be single in adaptive optics (AO), speckle imaging, and radial velocity (RV) studies. The A binary is circular with a 5.1-day period, while the B binary is eccentric with a 13.1-day period. The gamma velocities of the A and B binaries are different by ~10 km/s. That, coupled with their resolved projected separation of 0.09, indicates that the orbital period and separation of the C binary (consisting of A orbiting B) are ~65 years and ~25 AU, respectively, under the simplifying assumption of a circular orbit. Motion within the C orbit should be discernible via future RV, AO, and speckle imaging studies within a couple of years. The C system (i.e., 212651213) has a radial velocity and proper motion that differ from that of 212651234 by only ~1.4 km/s and ~3 mas/yr. This set of similar space velocities in 3 dimensions strongly implies that these two objects are also physically bound, making this at least a quintuple star system.
We present 3 mm ALMA continuum and line observations at resolutions of 6.5 au and 13 au respectively, toward the Class 0 system IRAS 16293-2422 A. The continuum observations reveal two compact sources towards IRAS 16293-2422 A, coinciding with compact ionized gas emission previously observed at radio wavelengths (A1 and A2), confirming the long-known radio sources as protostellar. The emission towards A2 is resolved and traces a dust disk with a FWHM size of ~12 au, while the emission towards A1 sets a limit to the FWHM size of the dust disk of ~4 au. We also detect spatially resolved molecular kinematic tracers near the protostellar disks. Several lines of the J=5-4 rotational transition of HNCO, NH2CHO and t-HCOOH are detected, with which we derived individual line-of-sight velocities. Using these together with the CS (J=2-1), we fit Keplerian profiles towards the individual compact sources and derive masses of the central protostars. The kinematic analysis indicates that A1 and A2 are a bound binary system. Using this new context for the previous 30 years of VLA observations, we fit orbital parameters to the relative motion between A1 and A2 and find the combined protostellar mass derived from the orbit is consistent with the masses derived from the gas kinematics. Both estimations indicate masses consistently higher (0.5< M1<M2<2 Msun) than previous estimations using lower resolution observations of the gas kinematics. The ALMA high-resolution data provides a unique insight into the gas kinematics and masses of a young deeply embedded bound binary system.
Mass, radius, and age are three of the most fundamental parameters for celestial objects, enabling studies of the evolution and internal physics of stars, brown dwarfs, and planets. Brown dwarfs are hydrogen-rich objects that are unable to sustain core fusion reactions but are supported from collapse by electron degeneracy pressure. As they age, brown dwarfs cool, reducing their radius and luminosity. Young exoplanets follow a similar behaviour. Brown dwarf evolutionary models are relied upon to infer the masses, radii and ages of these objects. Similar models are used to infer the mass and radius of directly imaged exoplanets. Unfortunately, only sparse empirical mass, radius and age measurements are currently available, and the models remain mostly unvalidated. Double-line eclipsing binaries provide the most direct route for the absolute determination of the masses and radii of stars. Here, we report the SPECULOOS discovery of 2M1510A, a nearby, eclipsing, double-line brown dwarf binary, with a widely-separated tertiary brown dwarf companion. We also find that the system is a member of the $45pm5$ Myr-old moving group, Argus. The systems age matches those of currently known directly-imaged exoplanets. 2M1510A provides an opportunity to benchmark evolutionary models of brown dwarfs and young planets. We find that widely-used evolutionary models do reproduce the mass, radius and age of the binary components remarkably well, but overestimate the luminosity by up to 0.65 magnitudes, which could result in underestimated photometric masses for directly-imaged exoplanets and young field brown dwarfs by 20 to 35%.
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