اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدRX J0942.7-7726AB: an isolated pre-main sequence wide binary
137
0
0.0
(
0
)
تأليف
Simon J. Murphy
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We report the discovery of two young M-dwarfs, RX J0942.7-7726 (M1) and 2MASS J09424157-7727130 (M4.5), that were found only 42 arcsec apart in a survey for pre-main sequence stars surrounding the open cluster eta Chamaeleontis. Both stars have congruent proper motions and near-infrared photometry. Medium-resolution spectroscopy reveals that they are coeval (age 8-12 Myr), codistant (100-150 pc) and thus almost certainly form a true wide binary with a projected separation of 4000-6000 AU. The system appears too old and dynamically fragile to have originated in eta Cha and a traceback analysis argues for its birth in or near the Scorpius-Centaurus OB Association. RX J0942.7-7726AB joins a growing group of wide binaries kinematically linked to Sco-Cen, suggesting that such fragile systems can survive the turbulent environment of their natal molecular clouds while still being dispersed with large velocities. Conversely, the small radial velocity difference between the stars (2.7 pm 1.0 km/s) could mean the system is unbound, a result of the coincidental ejection of two single stars with similar velocity vectors from the OB association early in its evolution.
قيم البحث
اقرأ أيضاً
The young system RX J0529.3+1210 was initially identified as a single-lined spectroscopic binary. Using high-resolution infrared spectra, acquired with NIRSPEC on Keck II, we measured radial velocities for the secondary. The method of using the infra
red regime to convert single-lined spectra into double-lined spectra, and derive the mass ratio for the binary system, has been successfully used for a number of young, low-mass binaries. For RX J0529.3+1210, a long- period(462 days) and highly eccentric(0.88) binary system, we determine the mass ratio to be 0.78+/-0.05 using the infrared double-lined velocity data alone, and 0.73+/-0.23 combining visible light and infrared data in a full orbital solution. The large uncertainty in the latter is the result of the sparse sampling in the infrared and the high eccentricity: the stars do not have a large velocity separation during most of their ~1.3 year orbit. A mass ratio close to unity, consistent with the high end of the one sigma uncertainty for this mass ratio value, is inconsistent with the lack of a visible light detection of the secondary component. We outline several scenarios for a color difference in the two stars, such as one heavily spotted component, higher order multiplicity, or a unique evolutionary stage, favoring detection of only the primary star in visible light, even in a mass ratio ~1 system. However, the evidence points to a lower ratio. Although RX J0529.3+1210 exhibits no excess at near-infrared wavelengths, a small 24 micron excess is detected, consistent with circumbinary dust. The properties of this binary and its membership in Lambda Ori versus a new nearby stellar moving group at ~90 pc are discussed. We speculate on the origin of this unusual system and on the impact of such high eccentricity on the potential for planet formation.
K2 observations of the weak-lined T Tauri binary V928 Tau A+B show the detection of a single, asymmetric eclipse which may be due to a previously unknown substellar companion eclipsing one component of the binary with an orbital period $>$ 66 days. O
ver an interval of about 9 hours, one component of the binary dims by around 60%, returning to its normal brightness about 5 hours later. From modeling of the eclipse shape we find evidence that the eclipsing companion may be surrounded by a disk or a vast ring system. The modeled disk has a radius of $0.9923,pm,0.0005,R_*$, with an inclination of $56.78,pm, 0.03^circ$, a tilt of $41.22,pm,0.05^circ$, an impact parameter of $-0.2506,pm,0.0002,R_*$ and an opacity of 1.00. The occulting disk must also move at a transverse velocity of $6.637,pm,0.002,R_*,mathrm{day}^{-1}$, which depending on whether it orbits V928 Tau A or B, corresponds to approximately 73.53 or 69.26 $mathrm{km s}^{-1}$. A search in ground based archival data reveals additional dimming events, some of which suggest periodicity, but no unambiguous period associated with the eclipse observed by K2. We present a new epoch of astrometry which is used to further refine the orbit of the binary, presenting a new lower bound of 67 years, and constraints on the possible orbital periods of the eclipsing companion. The binary is also separated by 18 ($sim$2250 au) from the lower mass CFHT-BD-Tau 7, which is likely associated with V928 Tau A+B. We also present new high dispersion optical spectroscopy that we use to characterize the unresolved stellar binary.
Statistics of low-mass pre-main sequence binaries in the Orion OB1 association with separations ranging from 0.6 to 20 (220 to 7400 au at 370 pc) are studied using images from the VISTA Orion mini-survey and astrometry from Gaia. The input sample bas
ed on the CVSO catalog contains 1137 stars of K and M spectral types (masses between 0.3 and 0.9 Msun), 1021 of which are considered to be association members. There are 135 physical binary companions to these stars with mass ratios above ~0.13. The average companion fraction is 0.09+-0.01 over 1.2 decades in separation, slightly less than, but still consistent with, the field. We found a difference between the Ori OB1a and OB1b groups, the latter being richer in binaries by a factor 1.6+-0.3. No overall dependence of the wide-binary frequency on the observed underlying stellar density is found, although in the Ori OB1a off-cloud population these binaries seem to avoid dense clusters. The multiplicity rates in Ori OB1 and in sparse regions like Taurus differ significantly, hinting that binaries in the field may originate from a mixture of diverse populations.
We present results of our study of the close pre-main sequence spectroscopic binary CVSO 104 in Ori OB1, based on data obtained within the PENELLOPE legacy program. We derive, for the first time, the orbital elements of the system and the stellar par
ameters of the two components. The system is composed of two early M-type stars and has an orbital period of about 5 days and a mass ratio of 0.92, but contrarily to expectations does not appear to have a tertiary companion. Both components have been (quasi-)synchronized, but the orbit is still very eccentric. The spectral energy distribution clearly displays a significant infrared excess compatible with a circumbinary disk. The analysis of HeI and Balmer line profiles, after the removal of the composite photospheric spectrum, reveals that both components are accreting at a similar level. We also observe excess emission in H$alpha$ and H$beta$, which appears redshifted or blueshifted by more than 100 km/s with respect to the mass center of the system depending on the orbital phase. This additional emission could be connected with accretion structures, such as funnels of matter from the circumbinary disk. We also analyze the optical companion located at about 2.4 from the spectroscopic binary. This companion, that we named CVSO 104B, turns out to be a background Sun-like star not physically associated with the PMS system and not belonging to Ori OB1.
Stellar components in binaries are subject to tidal forces which influence asteroseismic properties. Tidally pertubed pulsations have been reported for different objects but none of these are in their pre-main sequence phase of evolution. This makes
RS Cha, consisting of two $delta$ Scuti stars and with pulsational characteristics influenced by tidal effects , the first such object observed. We aim to investigate the pulsational properties of the eclipsing binary RS Cha in terms of the theory of tidally perturbed pulsations. Based on photometric time series obtained from the TESS satellite, we performed binary modelling using PHOEBE to interpret the binary light curve and to allow the investigation of the pulsations of both components in RS Cha. We modelled the detrended light curve with the superposition of linear modes. The frequencies were then interpreted as self excited modes perturbed by tidal forces. We find evidence for tidally perturbed modes, which enables the identification of pulsation modes. RS Cha mainly exhibits dipole modes, while one prominent $l=2$ or $l=3$ mode is also inferred. The latter verifies previous results from spectroscopic time series. This work shows that RS Cha is an ideal candidate to test the theory of tidally perturbed pulsations within the framework of asteroseismic modelling. The identification of multiple pulsation modes using this theory is unprecedented and will be a keystone in the future of pre-main sequence asteroseismology. However, amplitude modulation caused by the changing light ratio during the orbital phase in an eclipsing binary also plays a significant role, which can complicate mode identification.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
