Abstract Through the Backyard Worlds: Planet 9 citizen science project we discovered a late-type L dwarf co-moving with the young K0 star BD+60 1417 at a projected separation of 37″ or 1662 au. The secondary—CWISER J124332.12+600126.2 (W1243)—is detected in both the CatWISE2020 and 2MASS reject tables. The photometric distance and CatWISE proper motion both match that of the primary within ∼1 σ and our estimates for a chance alignment yield a zero probability. Follow-up near-infrared spectroscopy reveals W1243 to be a very red 2MASS ( J – K s = 2.72), low surface gravity source that we classify as L6–L8 γ . Its spectral morphology strongly resembles that of confirmed late-type L dwarfs in 10–150 Myr moving groups as well as that of planetary mass companions. The position on near- and mid-infrared color–magnitude diagrams indicates the source is redder and fainter than the field sequence, a telltale sign of an object with thick clouds and a complex atmosphere. For the primary we obtained new optical spectroscopy and analyzed all available literature information for youth indicators. We conclude that the Li i abundance, its loci on color–magnitude and color–color diagrams, and the rotation rate revealed in multiple TESS sectors are all consistent with an age of 50–150 Myr. Using our re-evaluated age of the primary and the Gaia parallax, along with the photometry and spectrum for W1243, we find T eff = 1303 ± 31 K, log g = 4.3 ± 0.17 cm s −2 , and a mass of 15 ± 5 M Jup . We find a physical separation of ∼1662 au and a mass ratio of ∼0.01 for this system. Placing it in the context of the diverse collection of binary stars, brown dwarfs, and planetary companions, the BD+60 1417 system falls in a sparsely sampled area where the formation pathway is difficult to assess.
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Discovery of a Low-mass Comoving System Using NOIRLab Source Catalog DR2
Abstract We present the discovery of a low-mass comoving system found by means of the NOIRLab Source Catalog DR2. The system consists of the high proper-motion star LEHPM 5005 and an ultracool companion 2MASS J22410186-4500298 with an estimated spectral type of L2. The primary (LEHPM 5005) is likely a mid-M dwarf but over-luminous for its color, indicating a possible close equal mass binary. According to the Gaia EDR3 parallax of the primary, the system is located at a distance of 58 ± 2 pc. We calculated an angular separation of 7.″2 between both components, resulting in a projected physical separation of 418 au.
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- NSF-PAR ID:
- 10350054
- Date Published:
- Journal Name:
- Research Notes of the AAS
- Volume:
- 5
- Issue:
- 8
- ISSN:
- 2515-5172
- Page Range / eLocation ID:
- 196
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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ABSTRACT Episodic accretion is a low-mass pre-main sequence phenomenon characterized by sudden outbursts of enhanced accretion. These objects are classified into two: protostars with elevated levels of accretion that lasts for decades or more, called FUors, and protostars with shorter and repetitive bursts, called EXors. HBC 494 is a FUor object embedded in the Orion Molecular Cloud. Earlier Atacama Large (sub-)Millimeter Array (ALMA) continuum observations showed an asymmetry in the disc at 0${_{.}^{\prime\prime}}$2 resolution. Here, we present follow-up observations at ∼0${_{.}^{\prime\prime}}$03, resolving the system into two components: HBC 494 N (primary) and HBC 494 S (secondary). No circumbinary disc was detected. Both discs are resolved with a projected separation of ∼0${_{.}^{\prime\prime}}$18 (75 au). Their projected dimensions are 84 ± 1.8 × 66.9 ± 1.5 mas for HBC 494 N and 64.6 ± 2.5 × 46.0 ± 1.9 mas for HBC 494 S. The discs are almost aligned and with similar inclinations. The observations show that the primary is ∼5 times brighter/more massive and ∼2 times bigger than the secondary. We notice that the northern component has a similar mass to the FUors, while the southern has to EXors. The HBC 494 discs show individual sizes that are smaller than single eruptive YSOs. In this work, we also report 12CO, 13CO, and C18O molecular line observations. At large scale, the 12CO emission shows bipolar outflows, while the 13CO and C18O maps show a rotating and infalling envelope around the system. At a smaller scale, the 12CO and 13CO moment zero maps show cavities within the continuum discs’ area, which may indicate continuum over-subtraction or slow-moving jets and chemical destruction along the line of sight.
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Abstract The eclipsing binary IT Librae is an unusual system of two B-type stars that is situated about 1 kpc above the Galactic plane. The binary was probably ejected from its birthplace in the disk, but the implied time of flight to its current location exceeds the evolutionary lifetime of the primary star. Here we present a study of new high-dispersion spectroscopy and an exquisite light curve from the Kepler K2 mission in order to determine the system properties and resolve the timescale discrepancy. We derive a revised spectroscopic orbit from radial-velocity measurements and determine the component effective temperatures through comparison of reconstructed and model spectra (
T 1= 23.8 ± 1.8 kK,T 2= 13.7 ± 2.5 kK). We use the Eclipsing Light Curve code to model the K2 light curve, and from the inclination of the fit we derive the component masses (M 1= 9.6 ± 0.6M ⊙,M 2= 4.2 ± 0.2M ⊙) and mean radii (R 1= 6.06 ± 0.16R ⊙,R 2= 5.38 ± 0.14R ⊙). The secondary star is overluminous for its mass and appears to fill its Roche lobe. This indicates that IT Librae is a post-mass-transfer system in which the current secondary was the mass donor star. The current primary star was rejuvenated by mass accretion, and its evolutionary age corresponds to the time since the mass transfer stage. Consequently, the true age of the binary is larger than the ejection time of flight, thus resolving the timescale discrepancy. -
Aims. HD 206893 is a nearby debris disk star that hosts a previously identified brown dwarf companion with an orbital separation of ∼10 au. Long-term precise radial velocity (RV) monitoring, as well as anomalies in the system proper motion, has suggested the presence of an additional, inner companion in the system. Methods. Using information from ongoing precision RV measurements with the HARPS spectrograph, as well as Gaia host star astrometry, we have undertaken a multi-epoch search for the purported additional planet using the VLTI/GRAVITY instrument. Results. We report a high-significance detection over three epochs of the companion HD 206893c, which shows clear evidence for Keplerian orbital motion. Our astrometry with ∼50−100 μarcsec precision afforded by GRAVITY allows us to derive a dynamical mass of 12.7$ ^{+1.2}_{-1.0} $ M Jup and an orbital separation of 3.53$ ^{+0.08}_{-0.06} $ au for HD 206893c. Our fits to the orbits of both companions in the system use both Gaia astrometry and RVs to also provide a precise dynamical estimate of the previously uncertain mass of the B component, and therefore allow us to derive an age of 155 ± 15 Myr for the system. We find that theoretical atmospheric and evolutionary models that incorporate deuterium burning for HD 206893c, parameterized by cloudy atmosphere models as well as a “hybrid sequence” (encompassing a transition from cloudy to cloud-free), provide a good simultaneous fit to the luminosity of both HD 206893B and c. Thus, accounting for both deuterium burning and clouds is crucial to understanding the luminosity evolution of HD 206893c. Conclusions. In addition to using long-term RV information, this effort is an early example of a direct imaging discovery of a bona fide exoplanet that was guided in part by Gaia astrometry. Utilizing Gaia astrometry is expected to be one of the primary techniques going forward for identifying and characterizing additional directly imaged planets. In addition, HD 206893c is an example of an object narrowly straddling the deuterium-burning limit but unambiguously undergoing deuterium burning. Additional discoveries like this may therefore help clarify the discrimination between a brown dwarf and an extrasolar planet. Lastly, this discovery is another example of the power of optical interferometry to directly detect and characterize extrasolar planets where they form, at ice-line orbital separations of 2−4 au.more » « less
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Abstract The inerter pendulum vibration absorber (IPVA) is integrated between a spar and an annulus floater using a ball-screw mechanism to study its wave energy conversion potential. Hydrodynamic stiffness, added mass, and radiation damping effects on the spar-floater system are characterized using the boundary element method. It is found that a 1:2 internal resonance via a period-doubling bifurcation in the system is responsible for nonlinear energy transfer between the spar-floater system and the pendulum vibration absorber. This nonlinear energy transfer occurs when the primary harmonic solution of the system becomes unstable due to the 1:2 internal resonance phenomenon. The focus of this paper is to analyze this 1:2 internal resonance phenomenon near the first natural frequency of the system. The IPVA system when integrated with the spar-floater system is shown to outperform a linear coupling between the spar and the floater both in terms of the response amplitude operator (RAO) of the spar and one measure of the energy conversion potential of the system. Finally, experiments are performed on the IPVA system integrated with single-degree-of-freedom system (without any hydrodynamic effects) to observe the 1:2 internal resonance phenomenon and the nonlinear energy transfer between the primary mass and the pendulum vibration absorber. It is shown experimentally that the IPVA system outperforms a linear benchmark in terms of vibration suppression due to the energy transfer phenomenon.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3847/2515-5172/ac1f9c
