Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userA young hierarchical triple system harbouring a candidate debris disc
122
0
0.0
(
0
)
Authors
N.R. Deacon
Ask ChatGPT about the research
No Arabic abstract
We report the detection of a wide young hierarchical triple system where the primary has a candidate debris disc. The primary, TYC 5241-986-1 A, is a known Tycho star which we classify as a late-K star with emission in the X-ray, near and far-UV and Halpha suggestive of youth. Its proper motion, photometric distance (65-105 pc) and radial velocity lead us to associate the system with the broadly defined Local Association of young stars but not specifically with any young moving group. The presence of weak lithium absorption and X-ray and calcium H and K emission support an age in the 20 to ~125 Myr range. The secondary is a pair of M4.5+-0.5 dwarfs with near and far UV and Halpha emission separated by approximately 1 arcsec (~65-105 AU projected separation) which lie 145 arcsec (9200-15200 AU) from the primary. The primary has a WISE 22 micron excess and follow-up Herschel observations also detect an excess at 70 micron. The excess emissions are indicative of a 100-175 K debris disc. We also explore the possibility that this excess could be due to a coincident background galaxy and conclude that this is unlikely. Debris discs are extremely rare around stars older than 15 Myr, hence if the excess is caused by a disc this is an extremely novel system.
rate research
Read More
We present new imaging and spectroscopic data of the young Herbig star HD 144432 A, which was known to be a binary star with a separation of 1.47 arcsec. High-resolution NIR imaging data obtained with NACO at the VLT reveal that HD 144432 B itself is a close binary pair with a separation of 0.1 arcsec. High-resolution optical spectra, acquired with FEROS at the 2.2m MPG/ESO telescope in La Silla, of the primary star and its co-moving companions were used to determine their main stellar parameters such as effective temperature, surface gravity, radial velocity, and projected rotational velocity by fitting synthetic spectra to the observed stellar spectra. The two companions, HD 144432 B and HD 144432 C, are identified as low-mass T Tauri stars of spectral type K7V and M1V, respectively. From the position in the HRD the triple system appears to be co-eval with a system age of 6+/-3 Myr.
We present our analysis of HD~35502 based on high- and medium-resolution spectropolarimetric observations. Our results indicate that the magnetic B5IVsnp star is the primary component of a spectroscopic triple system and that it has an effective temperature of $18.4pm0.6,{rm kK}$, a mass of $5.7pm0.6,M_odot$, and a polar radius of $3.0^{+1.1}_{-0.5},R_odot$. The two secondary components are found to be essentially identical A-type stars for which we derive effective temperatures ($8.9pm0.3,{rm kK}$), masses ($2.1pm0.2,M_odot$), and radii ($2.1pm0.4,R_odot$). We infer a hierarchical orbital configuration for the system in which the secondary components form a tight binary with an orbital period of $5.66866(6),{rm d}$ that orbits the primary component with a period of over $40,{rm yrs}$. Least-Squares Deconvolution (LSD) profiles reveal Zeeman signatures in Stokes $V$ indicative of a longitudinal magnetic field produced by the B star ranging from approximately $-4$ to $0,{rm kG}$ with a median uncertainty of $0.4,{rm kG}$. These measurements, along with the line variability produced by strong emission in H$alpha$, are used to derive a rotational period of $0.853807(3),{rm d}$. We find that the measured $vsin{i}=75pm5,{rm km,s}^{-1}$ of the B star then implies an inclination angle of the stars rotation axis to the line of sight of $24^{+6}_{-10}degree$. Assuming the Oblique Rotator Model, we derive the magnetic field strength of the B stars dipolar component ($14^{+9}_{-3},{rm kG}$) and its obliquity ($63pm13degree$). Furthermore, we demonstrate that the calculated Alfv{e}n radius ($41^{+17}_{-6},R_ast$) and Kepler radius ($2.1^{+0.4}_{-0.7},R_ast$) place HD~35502s central B star well within the regime of centrifugal magnetosphere-hosting stars.
This paper presents the case of CoRoT LRa02_E2_0121, which was initially classified as a Neptune-size transiting-planet candidate on a relatively wide orbit of 36.3 days. Follow-up observations were performed with UVES, Sandiford, SOPHIE and HARPS. These observations revealed a faint companion in the spectra. To find the true nature of the system we derived the radial velocities of the faint companion using TODMOR - a two-dimensional correlation technique, applied to the SOPHIE spectra. Modeling the lightcurve with EBAS we discovered a secondary eclipse with a depth of ~0.07%, indicating a diluted eclipsing binary. Combined MCMC modeling of the lightcurve and the radial velocities suggested that CoRoT LRa02_E2_0121 is a hierarchical triple system with an evolved G-type primary and an A-type:F-type grazing eclipsing binary. Such triple systems are difficult to discover.
Time series of spectroscopic, speckle-interferometric, and optical long-baseline-interferometric observations confirm that $ u$ Gem is a hierarchical triple system. It consists of an inner binary composed of two B-type stars and an outer classical Be star. Several photospheric spectral lines of the inner components were disentangled, revealing two stars with very different rotational broadening ($sim$260 and $sim$140 kms$^{-1}$, respectively), while the photospheric lines of the Be star remain undetected. From the combined spectroscopic and astrometric orbital solution it is not possible to unambiguously cross-identify the inner astrometric components with the spectroscopic components. In the preferred solution based on modeling of the disentangled line profiles, the inner binary is composed of two stars with nearly identical masses of 3.3 M$_odot$ and the more rapidly rotating star is the fainter one. These two stars are in a marginally elliptical orbit ($e$ = 0.06) about each other with a period of 53.8 d. The third star also has a mass of 3.3 M$_odot$ and follows a more eccentric ($e$ = 0.24) orbit with a period of 19.1 yr. The two orbits are co-directional and, at inclinations of 79$^{circ}$ and 76$^{circ}$ of the inner and the outer orbit, respectively, about coplanar. No astrometric or spectroscopic evidence could be found that the Be star itself is double. The system appears dynamically stable and not subject to eccentric Lidov-Kozai oscillations. After disentangling, the spectra of the components of the inner binary do not exhibit peculiarities that would be indicative of past interactions. Motivations for a wide range of follow-up studies are suggested.
Hierarchical triple systems comprise a close binary and a more distant component. They are important for testing theories of star formation and of stellar evolution in the presence of nearby companions. We obtained 218 days of Kepler photometry of HD 181068 (magnitude of 7.1), supplemented by groundbased spectroscopy and interferometry, which show it to be a hierarchical triple with two types of mutual eclipses. The primary is a red giant that is in a 45-day orbit with a pair of red dwarfs in a close 0.9-day orbit. The red giant shows evidence for tidally-induced oscillations that are driven by the orbital motion of the close pair. HD 181068 is an ideal target for studies of dynamical evolution and testing tidal friction theories in hierarchical triple systems.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
