NEW H<sub>2</sub>COLLISION-INDUCED ABSORPTION AND NH<sub>3</sub>OPACITY AND THE SPECTRA OF THE COOLEST BROWN DWARFS

Saumon, D.; Marley, Mark S.; Abel, Martin; Frommhold, Lothar; Freedman, Richard

doi:10.1088/0004-637x/750/1/74

Cited by 121 publications

(186 citation statements)

References 98 publications

Supporting

Mentioning

180

Contrasting

Order By: Relevance

“…The spectrum of GJ 758 B is not well-matched by other empirical data of similar objects, specifically T6-T8 SpeX Prism standards, especially in the H band peak near 1.58 μm. K c data at 2.1 μm does not seem to be a discriminator for spectral type, but such longer wavelength data (including L′ and Ms, Janson et al 2011, not shown in figure) will be important in establishing g log , T eff , [Fe/H], and cloud cover from current (e.g., Morley et al 2012;Saumon et al 2012;Allard 2014) and future improved atmospheric models.…”

Section: Model Atmospheresmentioning

confidence: 99%

Project 1640 Observations of Brown Dwarf GJ 758 B: Near-infrared Spectrum and Atmospheric Modeling

Nilsson

Veicht

Godfrey

et al. 2017

ApJ

View full text Add to dashboard Cite

The nearby Sun-like star GJ 758 hosts a cold substellar companion, GJ 758 B, at a projected separation of 30 au, previously detected in high-contrast multi-band photometric observations. In order to better constrain the companion's physical characteristics, we acquired the first low-resolution (R ∼ 50) near-infrared spectrum of it using the high-contrast hyperspectral imaging instrument Project 1640 on Palomar Observatory's 5 m Hale telescope. We obtained simultaneous images in 32 wavelength channels covering the Y, J, and H bands (∼952-1770 nm), and used data processing techniques based on principal component analysis to efficiently subtract chromatic background speckle-noise. GJ 758 B was detected in four epochs during 2013 and 2014. Basic astrometric measurements confirm its apparent northwest trajectory relative to the primary star, with no clear signs of orbital curvature. Spectra of SpeX/IRTF observed Tdwarfs were compared to the combined spectrum of GJ 758 B, with χ 2 minimization suggesting a best fit for spectral type T7.0±1.0, but with a shallow minimum over T5-T8. Fitting of synthetic spectra from the BT-Settl13 model atmospheres gives an effective temperature T eff =741±25 K and surface gravity =  g log 4.3 0.5 dex (cgs). Our derived best-fit spectral type and effective temperature from modeling of the low-resolution spectrum suggest a slightly earlier and hotter companion than previous findings from photometric data, but do not rule out current results, and confirm GJ 758 B as one of the coolest sub-stellar companions to a Sun-like star to date.

show abstract

Section: Model Atmospheresmentioning

confidence: 99%

Project 1640 Observations of Brown Dwarf GJ 758 B: Near-infrared Spectrum and Atmospheric Modeling

Nilsson

Veicht

Godfrey

et al. 2017

ApJ

View full text Add to dashboard Cite

show abstract

“…FeH), weak or absent metal oxides (e.g. VO and CO), and enhanced collision-induced H2 absorption (CIA H2;Bates 1952;Borysow, Frommhold, & Moraldi 1989;Borysow, Jorgensen, & Fu 2001;Abel et al 2012;Saumon et al 2012) in the nearinfrared (NIR).…”

mentioning

confidence: 99%

Primeval very low-mass stars and brown dwarfs – I. Six new L subdwarfs, classification and atmospheric properties

Zhang

Pinfield

Galvez-Ortiz

et al. 2016

Mon. Not. R. Astron. Soc.

View full text Add to dashboard Cite

We have conducted a search for L subdwarf candidates within the photometric catalogues of the UKIRT Infrared Deep Sky Survey and Sloan Digital Sky Survey. Six of our candidates are confirmed as L subdwarfs spectroscopically at optical and/or nearinfrared wavelengths. We also present new optical spectra of three previously known L subdwarfs (WISEA J001450.17-083823.4, 2MASS J00412179+3547133 and ULAS J124425.75+102439.3). We examined the spectral type and metallicity classification of subclasses of known L subdwarfs. We summarized the spectroscopic properties of L subdwarfs with different spectral types and subclasses. We classify these new L subdwarfs by comparing their spectra to known L subdwarfs and L dwarf standards. We estimate temperatures and metallicities of 22 late-type M and L subdwarfs by comparing their spectra to BT-Settl models. We find that L subdwarfs have temperatures between 1500 and 2700 K, which are higher than similar-typed L dwarfs by around 100-400 K depending on different subclasses and subtypes. We constrained the metallicity ranges of subclasses of M, L, and T subdwarfs. We also discussed the spectral-type and absolute magnitude relationships for L and T subdwarfs.

show abstract

“…Those data were used to place the object in a diagram of M W 2 versus J − W 2, where W 2 is a band from the Widefield Infrared Survey Explorer (Wright et al 2010) that is similar to [4.5] from Spitzer. The position of WISE 0855-0714 in that diagram was better reproduced by cloudy models than cloudless models (Morley et al 2012(Morley et al , 2014aSaumon et al 2012), which was interpreted as evidence of water ice clouds. However, Luhman & Esplin (2014) demonstrated that WISE 0855-0714 was roughly midway between those cloudless and cloudy models in a similar diagram of M 4.5 versus J −[4.5], and that its position was best matched by cloudless models that employed nonequilibrium chemistry (Saumon & Marley 2008;Saumon et al 2012).…”

Section: Discussionmentioning

confidence: 91%

“…The position of WISE 0855-0714 in that diagram was better reproduced by cloudy models than cloudless models (Morley et al 2012(Morley et al , 2014aSaumon et al 2012), which was interpreted as evidence of water ice clouds. However, Luhman & Esplin (2014) demonstrated that WISE 0855-0714 was roughly midway between those cloudless and cloudy models in a similar diagram of M 4.5 versus J −[4.5], and that its position was best matched by cloudless models that employed nonequilibrium chemistry (Saumon & Marley 2008;Saumon et al 2012). After measuring photometry for WISE 0855-0714 in several additional near-IR bands, Schneider et al (2016) and found that no single suite of models provided a clearly superior match to the observed spectral energy distribution (SED), and that all of the models differed significantly from the data.…”

Section: Discussionmentioning

confidence: 91%

Photometric Monitoring of the Coldest Known Brown Dwarf With the Spitzer Space Telescope*

Esplin

Luhman

Cushing

et al. 2016

ApJ

View full text Add to dashboard Cite

Because WISE J085510.83−071442.5 (hereafter WISE 0855-0714) is the coldest known brown dwarf (∼ 250 K) and one of the Sun's closest neighbors (2.2 pc), it offers a unique opportunity for studying a planet-like atmosphere in an unexplored regime of temperature. To detect and characterize inhomogeneities in its atmosphere (e.g., patchy clouds, hot spots), we have performed time-series photometric monitoring of WISE 0855-0714 at 3.6 and 4.5 µm with the Spitzer Space Telescope during two 23 hr periods that were separated by several months. For both bands, we have detected variability with peak-to-peak amplitudes of 4-5% and 3-4% in the first and second epochs, respectively. The light curves are semi-periodic in the first epoch for both bands, but are more irregular in the second epoch. Models of patchy clouds have predicted a large increase in mid-IR variability amplitudes (for a given cloud covering fraction) with the appearance of water ice clouds at T eff <375 K, so if such clouds are responsible for the variability of WISE 0855-0714, then its small amplitudes of variability indicate a very small deviation in cloud coverage between hemispheres. Alternatively, the similarity in mid-IR variability amplitudes between WISE 0855-0714 and somewhat warmer T and Y dwarfs may suggest that they share a common origin for their variability (i.e., not water clouds). In addition to our variability data, we have examined other constraints on the presence of water ice clouds in the atmosphere of WISE 0855-0714, including the recent mid-IR spectrum from Skemer et al. (2016). We find that robust evidence of such clouds is not yet available.

show abstract

NEW H₂COLLISION-INDUCED ABSORPTION AND NH₃OPACITY AND THE SPECTRA OF THE COOLEST BROWN DWARFS

Cited by 121 publications

References 98 publications

Project 1640 Observations of Brown Dwarf GJ 758 B: Near-infrared Spectrum and Atmospheric Modeling

Project 1640 Observations of Brown Dwarf GJ 758 B: Near-infrared Spectrum and Atmospheric Modeling

Primeval very low-mass stars and brown dwarfs – I. Six new L subdwarfs, classification and atmospheric properties

Photometric Monitoring of the Coldest Known Brown Dwarf With the Spitzer Space Telescope*

Contact Info

Product

Resources

About

NEW H2COLLISION-INDUCED ABSORPTION AND NH3OPACITY AND THE SPECTRA OF THE COOLEST BROWN DWARFS

Cited by 121 publications

References 98 publications

Project 1640 Observations of Brown Dwarf GJ 758 B: Near-infrared Spectrum and Atmospheric Modeling

Project 1640 Observations of Brown Dwarf GJ 758 B: Near-infrared Spectrum and Atmospheric Modeling

Primeval very low-mass stars and brown dwarfs – I. Six new L subdwarfs, classification and atmospheric properties

Photometric Monitoring of the Coldest Known Brown Dwarf With the Spitzer Space Telescope*

Contact Info

Product

Resources

About

NEW H₂COLLISION-INDUCED ABSORPTION AND NH₃OPACITY AND THE SPECTRA OF THE COOLEST BROWN DWARFS