We investigate the intrinsic shapes of starless cores in the Orion GMC, using the prestellar core sample of Nutter and Ward-Thompson (2007), which is based on submillimeter SCUBA data. We employ a maximum-likelihood method to reconstruct the intrinsic distribution of ellipsoid axial ratios from the axial ratios of projected plane-of-the-sky core ellipses. We find that, independently of the details of the assumed functional form of the distribution, there is a strong preference for oblate cores of finite thickness. Cores with varying finite degrees of triaxiality are a better fit than purely axisymmetric cores although cores close to axisymmetry are not excluded by the data. The incidence of prolate starless cores in Orion is found to be very infrequent. We also test the consistency of the observed data with a uniform distribution of intrinsic shapes, which is similar to those found in gravoturbulent fragmentation simulations. This distribution is excluded at the 0.1% level. These findings have important implications for theories of core formation within molecular clouds.
In this chapter we review the properties of the Orion outlying clouds at b < -21 degrees. These clouds are located far off the Orion giant molecular cloud complex and are in most cases small cometary-shaped clouds, with their head pointing back towards the main Orion clouds. A wealth of data indicate that star formation is ongoing in many of these clouds. The star formation in these regions might have been triggered due to the strong impact of the massive stars in the Orion OB association. Some of the clouds discussed here may be part of the Orion-Eridanus bubble. An overview on each individua…
We suggest that the Orion A cloud is gravitationally collapsing on large scales, and is producing the Orion Nebula Cluster due to the focusing effects of gravity acting within a finite cloud geometry. In support of this suggestion, we show how an elliptical rotating sheet of gas with a modest density gradient along the major axis can collapse to produce a structure qualitatively resembling Orion A, with a fan-shaped structure at one end, ridges or filaments along the fan, and a narrow curved filament at the other end reminiscent of the famous integral-shaped filament. The model produces a loca…
We present results of phase-referencing VLBI observations of water maser sources in Orion-Monoceros Molecular Clouds with VERA (VLBI Exploration of Radio Astrometry), which is newly constructed Japanese VLBI network. Main topics of this poster are (1) the aim of one of the first scientific projects for VERA "3-Dimensional Structure and Kinematics of Orion-Monoceros Molecular Cloud Complex"; (2) current status (sensitivity and astrometric accuracy) of phase-referencing VLBI observations with VERA; and (3) results of VLBI observations of water sources in Orion-Monoceros Molecular Clouds with VER…
We use the 2MASS Second Incremental Release Point Source Catalog to investigate the spatial distribution of young stars in the Perseus, Orion A, Orion B, and MonR2 molecular clouds. After subtracting a semi-empirical model of the field star contamination from the observed star counts, stellar surface density maps are used to identify compact clusters and any stellar population found more uniformly distributed over the molecular cloud. Each cloud contains between 2 to 7 clusters, with at least half of the cluster population found in a single, rich cluster. In addition, a distributed stellar pop…
We have used the SHARP polarimeter at the Caltech Submillimeter Observatory to map the polarization at wavelengths of 350 and 450 micron in a ~2 x 3 arcmin region of the Orion Molecular Cloud. The map covers the brightest region of the OMC-1 ridge including the Kleinmann-Low (KL) nebula and the submillimeter source Orion-south. The ratio of 450-to-350 micron polarization is ~ 1.3 +/- 0.3 in the outer parts of the cloud and drops by a factor of 2 towards KL. The outer cloud ratio is consistent with measurements in other clouds at similar wavelengths and confirms previous measurements placing th…
Large scale mapping observations of the 3P1-3P0 fine structure transition of atomic carbon (CI, 492 GHz) and the J=3-2 transition of CO (346 GHz) toward the Orion A molecular cloud have been carried out with the Mt. Fuji submillimeter-wave telescope. The observations cover 9 square degrees, and include the Orion nebula M42 and the L1641 dark cloud complex. The CI emission extends over almost the entire region of the Orion A cloud and is surprisingly similar to that of 13CO(J=1-0).The CO(J=3-2) emission shows a more featureless and extended distribution than CI.The CI/CO(J=3-2) integrated inten…
The balloon-borne submillimeter instrument PRONAOS has observed one square degree areas towards the Orion and M17 molecular clouds. The 2' - 3.5' resolution maps obtained in four wide wavelength bands between 200 microns and 600 microns, exhibit the dust distribution in these regions. We analyze the temperature and spectral index of the dust, and we show the anticorrelation between these two parameters. We derive estimations of the ISM column densities and masses in these regions.
With its cometary appearance and a reflection nebula near its edge facing some bright Orion stars, the Lynd's cloud L1616 shows ample evidence for being affected by one or more of these massive stars. To estimate its mass and star formation efficiency as well as to determine if it is gravitationally bound, we mapped this cloud in J=1${\rightarrow}$0 transitions of $^{12}$CO and $^{13}$CO. It is found that the distribution of the emission in the line {\it wings} show clear evidence for substantial mass motions. Also, the ``virial'' mass of the cloud is found to be five times the actual cloud ma…
We present results of optical spectroscopic and photometric observation of the pre-main sequence stars associated with the cometary shaped dark cloud Lynds 1622, and 12CO and 13CO observations of the cloud. We determined the effective temperatures and luminosities of 14 pre-main sequence stars associated with the cloud from their positions in the Hertzsprung--Russell diagram, as well as constructed their spectral energy distributions using optical, 2MASS and Spitzer IRAC and MIPS data. We derived physical parameters of L1622 from the molecular observations. Our results are not compatible with …
The Orion star formation complex is the nearest region of on-going star formation that continues to produce both low and high mass stars. Orion is discussed in the larger context of star formation in the Solar vicinity over the last 100 Myr. The Orion complex is located on the far side of the Gould's Belt system of clouds and young stars throughwhich our Solar systemis drifting. A review is given of the overall structure and properties of the Orion star forming complex, the best studied OB association. Over the last 12 Myr, Orion has given birth to at least ten thousand stars contained in a ha…
We present initial results from a survey of the Orion A and B molecular clouds made with the InfraRed Array Camera (IRAC) onboard the Spitzer Space Telescope. This survey encompasses a total of 5.6 square degrees with the sensitivity to detect objects below the hydrogen burning limit at an age of 1 Myr. These observations cover a number of known star forming regions, from the massive star forming clusters in the Orion Nebula and NGC 2024, to small groups of low mass stars in the L1641. We combine the IRAC photometry with photometry from the 2MASS point source catalog and use the resulting seve…
The Orion Molecular Cloud 2/3 region (hereafter, OMC-2/3) and the reflection nebula NGC 1977 encompass a section of the Orion A molecular cloud undergoing vigorous star forming activity. One of the richest assemblages of protostars in the nearest 500 pc is seen in OMC-2/3, while NGC 1977 contains a cluster of over 100 young stars. In this review, we present a census of the protostars, pre-main sequence stars, and young brown dwarfs in these regions. These are identified through sub-millimeter surveys, far-red to near-infrared imaging and spectroscopy with ground-based telescopes, mid-infrared …
Diffuse far-ultraviolet stellar emission scattered by dust grains has been observed in a region near the Orion Nebula. In addition to the scattered stellar continuum, emission and absorption features produced by molecular hydrogen have been identified. In this Letter, we present an analysis of this absorption and fluorescent emission from molecular hydrogen in Orion. We model the spectra obtained with the Far Ultraviolet Spectroscopic Explorer using optical depth templates and a fluorescent emission code. These results are surprising because previous studies have found little ultraviolet absor…
Hierarchical structure from stellar clusters, to subgroups, to associations and star complexes is discussed in the context of the Orion stellar grouping and its origin. The analogous structure in gas clouds is also reviewed, with an emphasis on general fractal properties and mass distribution functions. The distinction between the cloud, cluster, and stellar mass functions is discussed in terms of different sampling statistics for hierarchically structured clumps in clouds with an interclump medium.
We present full resolution (~0.2mas, ~0.1 A.U.) Very Long Baseline Interferometry maps of the v=1, J=1-0 SiO masers in the Orion-KL nebula. The morphology and turbulent nature of the maser emission argues against models in which the masers form in an expanding and rotating protostellar disk. Rather, we find that the symmetry evident in the SiO maser emission points towards its genesis in a bipolar outflow. Water masers which also appear towards Orion-KL are known to share the velocity profile and double peaked characteristics of the SiO maser emission yet form much further away from the protos…
The ``integral-shaped filament'' of the Orion A giant molecular cloud was mapped in N2H+, and its northern end, the OMC-2/3 region was observed also in HC3N and CCS. The N2H+ distribution is similar to the dust continuum distribution, except for the central part of the Orion Nebula. The distribution of H13CO+ holds resemblance to that of dust continuum, but the N2H+ distribution looks more similar to dust continuum distribution. The N-bearing molecules, N2H+ and NH3 seem to be more intense in OMC-2, compared with the H13CO+ and CS distribution. We identified 34 cloud cores from N2H+ data. Over…
We present the polarization images in the $J$, $H$, & $Ks$ bands of the Orion Molecular Cloud 1 South region. The polarization images clearly show at least six infrared reflection nebulae (IRNe) which are barely seen or invisible in the intensity images. Our polarization vector images also identify the illuminating sources of the nebulae: IRN 1 & 2, IRN 3, 4, & 5, and IRN 6 are illuminated by three IR sources, Source 144-351, Source 145-356, and Source 136-355, respectively. Moreover, our polarization images suggest the candidate driving sources of the optical Herbig-Haro objects for the first…
We conducted deep NIR imaging observations of the Orion molecular cloud 2 and 3 using QUIRC on the 88-inch telescope of the University of Hawaii. Our purposes are 1) to generate a comprehensive NIR source catalog of these star forming clouds, and 2) to identify the NIR counterpart of the Chandra X-ray sources that have no counterpart in the 2MASS catalog. Our J-, H-, and K-band observations are about 2 mag deeper than those of 2MASS, and well match the current Chandra observation. We detected 1448 NIR sources, for which we derived the position, the J-, H-, and K-band magnitude, and the 2MASS c…
We present submillimeter polarimetry at 850 micron toward the filamentary star-forming region associated with the reflection nebulosity NGC 2068 in Orion B. These data were obtained using the James Clerk Maxwell Telescope's SCUBA polarimeter. The polarization pattern observed is not consistent with that expected for a field geometry defined by a single mean field direction. There are three distinct distributions of polarization angle, which could represent regions of differing inclination and/or field geometry within the filamentary gas. In general, the polarization pattern does not correlate …
The first polarimetric images of the OMC-3 region of the Orion A filamentary molecular cloud are presented. Using the JCMT, we have detected polarized thermal emission at 850 microns from dust along a 6' length of the dense filament. The polarization pattern is highly ordered and is aligned with the filament throughout most of the region. The plane-of-sky magnetic field direction is perpendicular to the measured polarization. The mean percentage polarization is 4.2% with a 1 sigma dispersion of 1%. This region is part of the integral-shaped filament, and active star formation is ongoing along …
We have observed several cloud cores in the Orion B (L1630) molecular cloud in the 2-1 transitions of C18O, C17O and 13C18O. We use these data to show that a model where the cores consist of very optically thick C18O clumps cannot explain their relative intensities. There is strong evidence that the C18O is not very optically thick. The CO emission is compared to previous observations of dust continuum emission to deduce apparent molecular abundances. The abundance values depend somewhat on the temperature but relative to `normal abundance' values, the CO appears to be depleted by about a fact…
We report the results of a new large scale survey of the Orion-Monoceros complex of molecular clouds made in the J = 1->0 line of CO with the Harvard-Smithsonian 1.2m millimetre-wave telescope. The survey consists of 52,288 uniformly spaced spectra that cover an area of 432 square degrees on the sky and is the most sensitive large-scale survey of the region to date. Distances to the constituent molecular clouds of the complex, estimated from an analysis of foreground and background stars, have provided information on the three dimensional structure of the entire complex.
We have developed an empirical and effective set of criteria, based on the 2MASS colors, to select candidate classical T Tauri stars (CTTS). This provides a useful tool to study the young stellar population in star-forming regions. Here we present our analysis of the bright-rimmed clouds (BRCs) B 35, B 30, IC 2118, LDN 1616, LDN 1634, and Orion East to show how massive stars interact with molecular clouds to trigger star formation. Our results support the radiation-driven implosion model in which the ionization fronts from OB stars compress a nearby cloud until the local density exceeds the cr…
The three dimensional structure of the brightest part of the Orion Nebula is assessed in the light of published and new data. We find that the widely accepted model of a concave blister of ionized material needs to be altered in the southwest direction from the Trapezium, where we find that the Orion-S feature is a separate cloud of very optically thick molecules within the body of ionized gas, which is probably the location of the multiple embedded sources that produce the outflows that define the Orion-S star formation region. Evidence for this cloud comes from the presence of H2CO lines in …
We have carried out a high spectral resolution line survey towards the Orion Kleinmann-Low (KL) cluster from 44-188 um. The observations were taken with the Long Wavelength Spectrometer (LWS) in Fabry-Perot mode, on board the Infrared Space Observatory (ISO). A total of 152 lines are clearly detected and a further 34 features are present as possible detections. The spectrum is dominated by the molecular species H2O, OH and CO, along with [OI] and [CII] lines from PDR or shocked gas and [OIII], [NIII] lines from the foreground M42 HII region. Several isotopic species, as well as NH3, are also d…
A census of classical T Tauri stars and Herbig Ae/Be stars has been performed around the Orion-Eridanus Superbubble which is ionized and created by the Ori OB1 association. This sample is used to study the spatial distribution of newborn stars, hence the recent star formation sequence, in the region that includes two giant molecular clouds (Orion A and B) and additional smaller clouds (NGC 2149, GN 05.51.4, VdB 64, the Crossbones, the Northern Filament, LDN 1551, LDN 1558, and LDN 1563). Most of the molecular clouds are located on the border of the Superbubble, and associated with H-alpha fila…
Polarized 850 micron thermal emission data of the region OMC-3 in the Orion A molecular cloud are presented. These data, taken in 1998 with the SCUBA polarimeter mounted on the James Clerk Maxwell Telescope, have been re-reduced using improved software. The polarization pattern is not suggestive of a uniform field structure local to OMC-3, nor does the orientation of the vectors align with existing polarimetry maps of the OMC-1 core 20' to the south. The depolarization toward high intensity regions cannot be explained by uniform field geometry except in the presence of changing grain structure…
We present high angular resolution 1.3 mm continuum, methyl cyanide molecular line, and 7 mm continuum observations made with the Submillimeter Array and the Very Large Array, toward the most highly obscured and southern part of the massive star forming region OMC1S located behind the Orion Nebula. We find two flattened and rotating molecular structures with sizes of a few hundred astronomical units suggestive of circumbinary molecular rings produced by the presence of two stars with very compact circumstellar disks with sizes and separations of about 50 AU, associated with the young stellar o…
We obtained near infrared (NIR) imaging with the Subaru Telescope of the class 0 protostar candidates in the Orion Molecular Cloud-3, two of which were discovered to have X-ray emission by the Chandra X-ray Observatory. We found strong evidence for the class~0 nature of the X-ray sources. First, our deep K-band image shows no emission brighter than 19.6 mag from both of these X-ray sources. Since class I protostars or class II T Tauri stars should be easily detected in the NIR with this sensitivity, the lack of K-band detection suggests that they are likely much more obscured than class I prot…
We observed the HH24-26 region in the L1630 Orion molecular cloud complex with the X-ray observatory ASCA in the 0.5$-$10 keV band. X-ray emission was detected from the T Tauri star SSV61 and from the region where the Class I protostars SSV63E and SSV63W are located (hereafter SSV63E+W). The spectra of both SSV63E+W and SSV61 are well explained by an optically thin thermal plasma model. The spectrum of the T Tauri star SSV61 has a low temperature of $kT=0.9$ (0.7$-$1.2) keV and a moderate absorption of $N_{\rm{H}}=1.3$ (0.9$-$1.7) $\times10^{22}$ cm$^{-2}$, while that of the protostar SSV63E+W…
The Chandra Orion Ultradeep project (COUP) observation described in a companion paper by Getman et al. provides an exceptionally deep X-ray survey of the Orion Nebula Cluster and associated embedded young stellar objects. Membership of the region is important for studies of the stellar IMF, cluster dynamics, and star formation. The COUP study detected 1616 X-ray sources. In this study we confirm cloud membership for 1315 stars, identify 16 probable foreground field stars having optical counterparts with discrepant proper motions, and classify the remaining 285 X-ray sources, of which 51 are li…
Context: To follow the early evolution of stars we need to understand how young stars accrete and eject mass. It is generally assumed that the FU Orionis phenomenon is related to the variations in the disk accretion, but many questions remain still open, in particular because of the rarity of FU Ori type stars. Aims: We explore here the characteristics of the outburst and of the environment of one new object, discovered recently in the in the active star formation region containing RNO127, within the Cygnus OB7 dark cloud complex. Methods: We present an extensive optical and near-infrared stud…
We present high sensitivity and high angular resolution images of the high velocity (vLSR>30kms^-1) CO emission in the J=1-0 and J=2-1 lines of the Orion KL region. These results reveal the morphology of the high-velocity CO emission at the most extreme velocities. High velocity emission have been only detected in two regions: BN/KL (IRc2/I) and Orion-S. The Orion-S region contains a very young (dynamical age of 10^3years), very fast (~110kms^-1) and very compact (<0.16pc) bipolar outflow. From the morphology of the high-velocity gas we estimate that the position of the powering source must be…
We present results from a survey of a 1300 arcmin^2 region of the Orion B South molecular cloud, including NGC 2024, NGC 2023, and the Horsehead Nebula (B33), obtained using the Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope. Submillimeter continuum observations at 450 microns and 850 microns are discussed. Using an automated algorithm, 57 discrete emission features (``clumps'') are identified in the 850 micron map. The physical conditions within these clumps are investigated under the assumption that the objects are in quasi-hydrostatic equilibrium. The…
Using the imaging polarimeter for the Submillimeter Common User Bolometric Array at the James Clerk Maxwell Telescope, we have detected polarized thermal emission at 850 micron from dust toward three star-forming core systems in the Orion B molecular cloud: NGC 2071, NGC 2024 and LBS 23N (HH 24). The polarization patterns are not indicative of those expected for magnetic fields dominated by a single field direction, and all exhibit diminished polarization percentages toward the highest intensity peaks. NGC 2024 has the most organized polarization pattern which is centered consistently along th…
We have analyzed HST ACS and WFPC2 new and archival images of eight HII regions to look for new proto-planetary disks (proplyds) similar to those found in the Orion Nebula. We find a wealth of features similar in size (though many are larger) to the bright cusps around the Orion Nebula proplyds. None of them, however, contains a definitive central star. From this, we deduce that the new cusps may not be proplyds, but instead are fragments of molecular cloud material. Out of all the features found in the eight HII regions examined, only one, an apparent edge-on silhouette in M17, may have a cen…
We present results from a 2300 arcmin^2 survey of the Orion A molecular cloud at 450 and 850 micron using the Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope. The region mapped lies directly south of the OMC1 cloud core and includes OMC4, OMC5, HH1/2, HH34, and L1641N. We identify 71 independent clumps in the 850 micron map and compute size, flux, and degree of central concentration in each. Comparison with isothermal, pressure-confined, self-gravitating Bonnor-Ebert spheres implies that the clumps have internal temperatures T_d ~ 22 +/- K and surface pre…
We present wide-field near-IR images of Orion A. K and H2 1-0S(1) images of a contiguous 8 sqr degree region are compared to photometry from Spitzer and dust-continuum maps obtained with MAMBO and SCUBA. We also measure proper motions for H2 features in 33 outflows. We increase the number of known H2 outflows in Orion A to 116. A total of 111 H2 flows were observed with Spitzer; outflow sources are identified for at least 72 of them. The MAMBO 1200 micron maps cover 97 H2 flows; 57 of them are associated with Spitzer sources and dust cores or extended emission. The H2 jets are widely distribut…
We present an analysis of J, H, and K time series photometry obtained with the southern 2MASS telescope over a 0.84 x 6 deg^2 region centered near the Orion Nebula Cluster. These data are used to establish the near-infrared variability properties of pre-main-sequence stars in Orion on time scales of 1-36 days, 2 months, and 2 years. A total of 1235 variable stars are identified, ~93% of which are associated with the Orion A molecular cloud. The variable stars exhibit a diversity of photometric behavior with time, including cyclic fluctuations, aperiodic day-to-day fluctuations, eclipses, slow …
In this study, we investigate the shapes of starless and protostellar cores using hydrodynamic, self-gravitating adaptive mesh refinement simulations of turbulent molecular clouds. We simulate observations of these cores in dust emission, including realistic noise and telescope resolution, and compare to the observed core shapes measured in Orion by Nutter & Ward-Thompson (2007). The simulations and the observations have generally high statistical similarity, with particularly good agreement between simulations and Orion B. Although protostellar cores tend to have semi-major axis to semi-minor…
Unbiased molecular line surveys are a powerful tool for analyzing the physical and chemical parameters of astronomical objects and are the only means for obtaining a complete view of the molecular inventory for a given source. The present work stands for the first such investigation of a photon-dominated region. The first results of an ongoing millimeter-wave survey obtained towards the Orion Bar are reported. The APEX telescope in combination with the APEX-2A facility receiver was employed in this investigation. We derived the physical parameters of the gas through LVG analyses of the methano…
Cornerstone molecules (CO, H_2CO, CH_3OH, HCN, HNC, CN, CS, SO) were observed toward seven sub-millimeter bright sources in the Orion molecular cloud in order to quantify the range of conditions for which individual molecular line tracers provide physical and chemical information. Five of the sources observed were protostellar, ranging in energetics from 1 - 500L_sun, while the other two sources were located at a shock front and within a photodissociation region (PDR). Statistical equilibrium calculations were used to deduce from the measured line strengths the physical conditions within each …
We report a detection in the interstellar medium of an infrared transition within the electronic ground state of the deuterated hydrogen molecule, HD. Through a deep integration with the Short-Wavelength-Spectrometer on ISO, the pure rotational v=0-0 R(5) line at 19.43um was detected toward the Orion (OMC-1) outflow at its brightest H_2 emission region, Peak 1. The ~20" beam-averaged observed flux of the line is (1.84 +- 0.4) 10^-5 erg cm^-2 s^-1 sr^-1. Upper flux limits were derived for sixteen other rotational and ro-vibrational HD lines in the wavelength range 2.5 to 38 um. We utilize the r…
We have mapped four massive cores in Orion using the \ammonia (J,K) = (1,1) and (J,K) = (2,2) inversion transitions, as part of our effort to study the pre--protostellar phase of massive star formation. These cores were selected to be quiescent, i.e. they contain no apparent IR sources and are not associated with any molecular outflows. These cores are one order of magnitude more massive than dark cloud cores and have about twice the line width. This paper focuses on their temperature structure. We find a statistically significant correlation between the gas kinetic temperature and the gas col…
In order to obtain a census of the pre-stellar and star-forming molecular cores, we have begun an unbiased survey in CS and N2H+ of the L1630 and L1641 molecular clouds. The use of these two molecular species enables us to quantify and disentangle the effects of depletion often seen in CS observations of dense cores. The spectral line data will provide essential kinematical information not present in similar studies of the sub-millimeter dust-continuum, enabling us to examine the overall core to core velocity dispersion and study the effects of infall and outflows around known sub-mm and infra…
Most stars form as members of large associations within dense, very cold (10-100 K) molecular clouds. The nearby giant molecular cloud in Orion hosts several thousand stars of ages less than a few million years, many of which are located in or around the famous Orion Nebula, a prominent gas structure illuminated and ionized by a small group of massive stars (the Trapezium). We present X-ray observations obtained with the X-ray Multi-Mirror satellite XMM-Newton revealing that a hot plasma with a temperature of 1.7-2.1 million K pervades the southwest extension of the nebula. The plasma, origina…
We present the results of a wide-area mapping of the far-infrared continuum emission toward the Orion complex by using a Japanese balloon-borne telescope. The 155-um continuum emission was detected over a region of 1.5 deg^2 around the KL nebula with 3' resolution similar to that of the IRAS 100-um map. Assuming a single-temperature model of the thermal equilibrium dust, maps of the temperature and the optical depth were derived from the 155 um intensity and the IRAS 100 um intensity. The derived dust temperature is 5 - 15 K lower and the derived dust optical thickness were derived from the 15…
Forty new low mass members with spectral types ranging from M4-M9 have been confirmed in the Orion Molecular Cloud 2/3 region. Through deep, I, z', J, H, K photometry of a 20' x 20' field in OMC 2/3, we selected brown dwarf candidates for follow-up spectroscopy. Low resolution far-red and near-infrared spectra were obtained for the candidates, and 19 young brown dwarfs in the OMC 2/3 region are confirmed. They exhibit spectral types of M6.5-M9, corresponding to approximate masses of 0.075-0.015 M_solar using the evolutionary models of Baraffe et al. (1998). At least one of these bona fide youn…
