The Smallest Mass Ratio Young Star Spectroscopic Binaries

Prato, L.; Simon, M.; Mazeh, T.; McLean, Ian S.; Norman, Dara; Zucker, S.

doi:10.1086/339397

Cited by 79 publications

(104 citation statements)

References 38 publications

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“…We found these measurements, with uncertainties ranging from 0.5 to 0.9 km s −1 , were all consistent, albeit with lower precision, with those reported in Blake et al (2010) to within 1.6σ . While a forward-modeling approach would have likely produced better precision, our uncertainties are nevertheless roughly equivalent to contemporary NIRSPEC RV measurements of very cool dwarfs (e.g., Prato et al 2002;Zapatero Osorio et al 2007;Blake et al 2008Blake et al , 2010Rice et al 2010;Rodler et al 2012). Table 9 lists the final RV measurements for SDSS J0006−0852 for each epoch.…”

Section: Radial Velocity Measurementsmentioning

confidence: 69%

Discovery of a Very Low Mass Triple With Late-M and T Dwarf Components: Lp 704-48/SDSS J0006–0852ab

Burgasser

Luk

Dhital

et al. 2012

ApJ

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We report the identification of the M9 dwarf SDSS J000649.16−085246.3 as a spectral binary and radial velocity (RV) variable with components straddling the hydrogen-burning mass limit. Low-resolution near-infrared spectroscopy reveals spectral features indicative of a T dwarf companion, and spectral template fitting yields component types of M8.5 ± 0.5 and T5 ± 1. High-resolution near-infrared spectroscopy with Keck/NIRSPEC reveals pronounced RV variations with a semi-amplitude of 8.2 ± 0.4 km s −1 . From these we determine an orbital period of 147.6 ± 1.5 days and eccentricity of 0.10 ± 0.07, making SDSS J0006−0852AB the third tightest very low mass binary known. This system is also found to have a common proper motion companion, the inactive M7 dwarf LP 704-48, at a projected separation of 820 ± 120 AU. The lack of Hα emission in both M dwarf components indicates that this system is relatively old, as confirmed by evolutionary model analysis of the tight binary. LP 704-48/SDSS J0006−0852AB is the lowest-mass confirmed triple identified to date, and one of only seven candidate and confirmed triples with total masses below 0.3 M currently known. We show that current star and brown dwarf formation models cannot produce triple systems like LP 704-48/SDSS J0006−0852AB, and we rule out Kozai-Lidov perturbations and tidal circularization as a viable mechanism to shrink the inner orbit. The similarities between this system and the recently uncovered low-mass eclipsing triples NLTT 41135AB/41136 and LHS 6343ABC suggest that substellar tertiaries may be common in wide M dwarf pairs.

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Section: Radial Velocity Measurementsmentioning

confidence: 69%

Discovery of a Very Low Mass Triple With Late-M and T Dwarf Components: Lp 704-48/SDSS J0006–0852ab

Burgasser

Luk

Dhital

et al. 2012

ApJ

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“…Radial and Rotational Velocity: To measure the radial velocity (RV) and rotational velocity of J024902 ABC, we used IDL software to perform a cross-correlation (CC) analysis Bender & Simon 2008) with a suite of K5 − M5 RV templates taken from Prato et al (2002). These template stars were observed during FEROS runs in 2011 December and 2012 October and were reduced following the same methods as the science target.…”

Section: Feros Observations Of the J024902 Systemmentioning

confidence: 99%

Characterization of close visual binaries from the AstraLux Large M Dwarf Survey

Bergfors¹,

Brandner²,

Bonnefoy³

et al. 2015

Mon. Not. R. Astron. Soc.

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We present VLT/SINFONI J, H + K spectra of seven close visual pairs in M dwarf binary/triple systems, discovered or observed by the AstraLux M dwarf survey. We determine the spectral types to within ±1.0 subclasses from comparison to template spectra and the strength of K-band water absorption, and derive effective temperatures. The results are compared to optical spectral types of the unresolved binary/multiple systems, and we confirm that our photometric method to derive spectral types in the AstraLux M dwarf survey is accurate. We look for signs of youth such as chromospheric activity and low surface gravity, and find an age in the range 0.25 − 1 Gyr for the GJ 852 system. Strong Li absorption is detected in optical spectra of the triple system J024902 obtained with FEROS at the ESO-MPG 2.2 m telescope. The equivalent width of the absorption suggests an age consistent with the β Pic moving group. However, further observations are needed to establish group membership. Ongoing orbital monitoring will provide dynamical masses and thus calibration of evolutionary models for low mass stars.

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“…Its upper boundary, on the other hand, is not as well-defined. The lowest mass ratio known for a stellar spectroscopic companion to a solar-like star is 0.2 (Prato et al 2002;Mazeh et al 2003); however, as pointed out by Mazeh et al (2003), stellar systems with M 2 /M 1 < 0.2−0.3 have not been studied well yet. For the following consideration, a mass ratio of 0.08 is somewhat arbitrarily assumed as the upper value for the BD desert, but this is not confirmed by observations.…”

Section: Brown Dwarf Desertmentioning

confidence: 99%

Radial velocity survey for planets and brown dwarf companions to very young brown dwarfs and very low-mass stars in Chamaeleon I with UVES at the VLT

Joergens¹

2006

A&A

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We present results of a radial velocity (RV) survey for planets and brown dwarf (BD) companions to very young BDs and (very) low-mass stars in the Cha I star-forming cloud. Time-resolved high-resolution echelle spectra of Cha Hα 1-8 and Cha Hα 12 (M6-M8), B34 (M5), CHXR 74 (M4.5), and Sz 23 (M2.5) were taken with UVES at the VLT between 2000 and 2004. The precision achieved for the relative RVs range between 40 and 670 m s −1 and is sufficient to detect Jupiter mass planets around the targets. This is the first RV survey of very young BDs. It probes multiplicity, which is a key parameter for formation in an as yet unexplored domain, in terms of age, mass, and orbital separation. We find that the subsample of ten BDs and very low-mass stars (VLMSs, M < ∼ 0.12 M , spectral types M5−M8) has constant RVs on time scales of 40 days and less. For this group, estimates of upper limits for masses of hypothetical companions range between 0.1 M Jup and 1.5 M Jup for assumed orbital separations of 0.1 AU. This hints at a rather small multiplicity fraction for very young BDs/VLMSs, for orbital separations of < ∼ 0.1 AU and orbital periods of < ∼ 40 days. Furthermore, the non-variable objects demonstrate the lack of any significant RV noise due to stellar activity down to the precision necessary to detect giant planets. Thus, very young BDs/VLMSs are suitable targets for RV surveys for planets. Three objects of the sample exhibit significant RV variations with peak-to-peak RV differences of 2−3 km s −1 . For the highest mass object observed with UVES (Sz 23, ∼0.3 M ), the variations are on time scales of days, which might be explained by rotational modulation. On the other hand, the BD candidate Cha Hα 8 (M6.5) and the low-mass star CHXR 74 (M4.5) both display significant RV variations on times scales of > ∼ 150 days, while they are both RV constant or show only much smaller amplitude variations on time scales of days to weeks, i.e. of the rotation periods. A suggested explanation for the detected RV variations of CHXR 74 and Cha Hα 8 is that they are caused by giant planets or very low-mass BDs of at least a few Jupiter masses orbiting with periods of several months or longer. Thus, the presented RV data indicate that orbital periods of companions to very young BDs and (very) low-mass stars are possibly several months or longer, and that orbital separations are > ∼ 0.2 AU. This parameter range has not been covered for all targets yet, but will be probed by follow-up observations. Furthermore, we show that the scaled down equivalent to the BD desert found around solar-like stars would be a giant planet desert around BD and VLMS primaries, if formed by the same mechanism. The present data test its existence for the targets in the limited separation range of the survey. So far, no hints of companions in a "giant planet desert" have been found.

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The Smallest Mass Ratio Young Star Spectroscopic Binaries

Cited by 79 publications

References 38 publications

Discovery of a Very Low Mass Triple With Late-M and T Dwarf Components: Lp 704-48/SDSS J0006–0852ab

Discovery of a Very Low Mass Triple With Late-M and T Dwarf Components: Lp 704-48/SDSS J0006–0852ab

Characterization of close visual binaries from the AstraLux Large M Dwarf Survey

Radial velocity survey for planets and brown dwarf companions to very young brown dwarfs and very low-mass stars in Chamaeleon I with UVES at the VLT

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