WISE Discovered Brown Dwarfs
The Wide-field Infrared Survey Explorer (WISE) is a space telescope that collected all-sky images at 3.4, 4.6, 12, and 22 microns. The 3.4 and 4.6 micron band's were designed specifically to identify cool sub-stellar objects. The WISE Brown Dwarf Team identified and spectroscopically confirmed more than 250 new M, L, T and Y dwarfs. I personally observed and/or reduced the spectra of ~130 of these sources, employing spectrographs at Palomar, Keck, Gemini, Hubble, IRTF, and Magellan. My 2013 paper reports the discovery of 87 new T dwarfs, three extremely red brown dwarfs, and 14 confirmed objects from the literature. From this expanded sample we find that 32% of late-type T dwarfs are blue relative to the spectral standards, while only 11% are redder than the standards. Comparison of the Y/J and K/J index to models suggests diverse atmospheric conditions and supports the possible re-emergence of clouds after the L/T transition.
MOSFIRE
I began working on the Multi-Object Spectrometer for Infra-Red Exploration (MOSFIRE) in early June 2009. This instrument allows for the simultaneous observation of up to 46 object in a single passband at R~3,500 across a 6.1'x6.1' field of view. In the lab I tested and assembled many of cryogenic mechanisms that went inside MOSFIRE, including the configurable-slit unit, filter wheel, pupil mechanism, detector head, rotator bearing, and focus mechanism. I also determined and implemented optical and mechanical changes to the off-the-shelf MAGIQ guider-head. In July 2010 we successfully acquired first light in the lab and on April 4th, 2012 we obtained first light on-sky at Keck. Since delivery I have worked on data reduction methods and DRP testing.
NTTS 155808-2219
The young, low-mass, triple system NTTS 155808-2219 (ScoPMS 20) was previously identified as a ~17 day period single-lined spectroscopic binary (SB) with a tertiary component at 0.21 arcsec. Using high-resolution infrared spectra, acquired with NIRSPEC on Keck II, both with and without adaptive optics (AO), we measured radial velocities (RVs) of all three components. Reanalysis of the single-lined visible light observations, made from 1987 to 1993, also yielded RV detections of the three stars. Combining visible light and infrared data to compute the orbital solution produces orbital parameters consistent with the single-lined solution and a mass ratio of q = 0.78 ± 0.01 for the SB. We discuss the consistency between our results and previously published data on this system, our RV analysis with both observed and synthetic templates, and the possibility that this system is eclipsing, providing a potential method for the determination of the stars' absolute masses. Over the ~20 year baseline of our observations, we have measured the acceleration of the SB's center of mass in its orbit with the tertiary. Long-term, AO imaging of the tertiary will eventually yield dynamical data useful for component mass estimates.
RX J0529.3+1210
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 infrared 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 yr orbit. A mass ratio close to unity, consistent with the high end of the 1σ 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 μm excess is detected, consistent with circumbinary dust. The properties of this binary and its membership in λ 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, the largest observed in a pre-main-sequence double-lined system to date, on the potential for planet formation.
BDSS
The NIRSPEC Brown Dwarf Spectroscopic Survey (BDSS) was initiated in 1999 by Ian McLean (UCLA) and Davy Kirkpatrick (IPAC) following deployment of NIRSPEC to Keck II and the discovery of brown dwarf candidates in the Two Micron All Sky Survey (2MASS). High quality near-infrared spectra for a large sample of M, L, and T dwarfs have been obtained by many members of the BDSS team since inception of the project. Moderate-resolution (R˜2,000) near-IR spectra include over 200 objects (approximately 20% field M dwarfs, 30% young M dwarfs, 10% M giants, 30% L dwarfs, and 10% T dwarfs). These medium-resolution data products include J-band (1.143-1.375 micron) coverage for every object and broader coverage (0.96-2.31 micron) for about 30 targets. High-resolution (R˜20,000) spectra consist primarily of cross-dispersed J-band (1.165-1.323 micron) observations, resulting in eight dispersion orders for ~70 objects (approximately 15% field M dwarfs, 40% young M dwarfs, 25% L dwarfs, and 20% T dwarfs). The BDSS Online Archive (BDSSarchive.org) described in this poster is a catalog of all observed objects, with published data available as reduced and extracted ascii files. Unpublished data are also available upon request. Other database updates, including a mutable table and links to reductions for multiple observational epochs, will be implemented in the near future. The sample size, wavelength coverage, spectral resolution, and high quality data makes the BDSS Online Archive a premier library of brown dwarf medium-to-high resolution near-infrared spectra.
