Browsing by Subject "edge-on disk"

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A Herschel Search for Cold Dust in Brown Dwarf Disks: First Results
(2012-01) Harvey, Paul M.; Henning, Thomas; Menard, Francois; Wolf, Sebastian; Liu, Yao; Cieza, Lucas A.; Evans, Neal J., II; Pascucci, Ilaria; Merin, Bruno; Pinte, Christophe; Harvey, Paul M.; Evans, Neal J., II
We report initial results from a Herschel program to search for far-infrared emission from cold dust around a statistically significant sample of young brown dwarfs. The first three objects in our survey are all detected at 70 mu m, and we report the first detection of a brown dwarf at 160 mu m. The flux densities are consistent with the presence of substantial amounts of cold dust in the outer disks around these objects. We modeled the spectral energy distributions (SEDs) with two different radiative transfer codes. We find that a broad range of model parameters provide a reasonable fit to the SEDs, but that the addition of our 70 mu m, and especially the 160 mu m, detection enables strong lower limits to be placed on the disk masses since most of the mass is in the outer disk. We find likely disk masses in the range of a few x 10(-6) to 10(-4) M(circle dot). Our models provide a good fit to the SEDs and do not require dust settling.
Spectroscopic Confirmation Of Young Planetary-Mass Companions On Wide Orbits
(2014-03) Bowler, Brendan P.; Liu, Michael C.; Kraus, Adam L.; Mann, Andrew W.; Kraus, Adam L.; Mann, Andrew W.
We present moderate-resolution ( R similar to 4000-5000) near-infrared integral field spectroscopy of the young (1-5 Myr) 6-14 M-Jup companions ROXs 42B b and FW Tau b obtained with Keck/OSIRIS and Gemini-North/NIFS. The spectrum of ROXs 42B b exhibits clear signs of low surface gravity common to young L dwarfs, confirming its extreme youth, cool temperature, and low mass. Overall, it closely resembles the free-floating 4-7 M-Jup L-type Taurus member 2MASS J04373705+2331080. The companion to FW Tau AB is more enigmatic. Our optical and near-infrared spectra show strong evidence of outflow activity and disk accretion in the form of line emission from [S II], [O I], H alpha, Ca II, [Fe II], Pa beta, and H-2. The molecular hydrogen emission is spatially resolved as a single lobe that stretches approximate to 0 ''.1 (15 AU). Although the extended emission is not kinematically resolved in our data, its morphology resembles shock-excited H-2 jets primarily seen in young Class 0 and Class I sources. The near-infrared continuum of FW Tau b is mostly flat and lacks the deep absorption features expected for a cool, late-type object. This may be a result of accretion-induced veiling, especially in light of its strong and sustained Ha emission (EW(H alpha)greater than or similar to 290 angstrom). Alternatively, FW Tau b may be a slightly warmer (M5-M8) accreting low-mass star or brown dwarf (0.03-0.15 M circle dot) with an edge-on disk. Regardless, its young evolutionary stage is in stark contrast to its Class III host FW Tau AB, indicating a more rapid disk clearing timescale for the host binary system than for its wide companion. Finally, we present near-infrared spectra of the young (similar to 2-10 Myr) low-mass (12-15 M-Jup) companions GSC 6214-210 B and SR 12 C and find they best resemble low- gravity M9.5 and M9 substellar templates.
Three Wide Planetary-Mass Companions To fw Tau, ROXs 12, And ROXs 42B
(2014-01) Kraus, Adam L.; Ireland, Michael J.; Cieza, Lucas A.; Hinkley, Sasha; Dupuy, Trent J.; Bowler, Brendan P.; Liu, Michael C.; Kraus, Adam L.
We report the discovery of three planetary-mass companions (M = 6-20 M-Jup) in wide orbits (rho similar to 150-300 AU) around the young stars FW Tau (Taurus-Auriga), ROXs 12 (Ophiuchus), and ROXs 42B (Ophiuchus). All three wide planetary-mass companions (PMCs) were reported as candidate companions in previous binary survey programs, but then were neglected for > 10 yr. We therefore obtained followup observations that demonstrate that each candidate is comoving with its host star. Based on the absolute M-K' magnitudes, we infer masses (from hot-start evolutionary models) and projected separations of 10 +/- 4 M-Jup and 330 +/- 30 AU for FW Tau b, 16 +/- 4 M-Jup and 210 +/- 20 AU for ROXs 12, and 10 +/- 4 M-Jup and 140 +/- 10 AU for ROXs 42B b. We also present similar observations for 10 other candidates that show that they are unassociated field stars, as well as multicolor JHK'L' near-infrared photometry for our new PMCs and for five previously identified substellar or planetary-mass companions. The near-infrared photometry for our sample of eight known and new companions generally parallels the properties of free-floating, low-mass brown dwarfs in these star-forming regions. However, five of the seven objects with M < 30 M-Jup are redder in K' - L' than the distribution of young free-floating counterparts of similar J - K' color. We speculate that this distinction could indicate a structural difference in circumplanetary disks, perhaps tied to higher disk mass since at least two of the objects in our sample are known to be accreting more vigorously than typical free-floating counterparts.