Calibrating Ultracool Dwarfs: Optical Template Spectra, Bolometric Corrections, and χ Values<sup>1</sup>

Schmidt, Sarah J.; West, Andrew A.; Bochanski, John J.; Hawley, Suzanne L.; Kielty, Collin

doi:10.1086/677403

Cited by 31 publications

(39 citation statements)

References 72 publications

(102 reference statements)

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“…We did not consider the spectral type uncertainties because they do not have a significant effect on the BC values beyond the adopted BC error; from early-through mid-Ls, the J-and K-band BCs vary little to within a few subtypes. This behavior is also present in other BC determinations available in the literature (e.g., Leggett et al 2001;Dahn et al 2002;Golimowski et al 2004;Schmidt et al 2014).…”

Section: Masses and σ Orionis Mass Functionsupporting

confidence: 79%

Optical and Near-infrared Spectra of σ Orionis Isolated Planetary-mass Objects

Osorio

Béjar

Ramírez

2017

ApJ

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We have obtained low-resolution optical (0.7-0.98 µm) and near-infrared (1.11-1.34 µm and 0.8-2.5 µm) spectra of twelve isolated planetary-mass candidates (J = 18.2-19.9 mag) of the 3-Myr σ Orionis star cluster with a view to determining the spectroscopic properties of very young, substellar dwarfs and assembling a complete cluster mass function. We have classified our targets by visual comparison with high-and low-gravity standards and by measuring newly defined spectroscopic indices. We derived L0-L4.5 and M9-L2.5 using high-and low-gravity standards, respectively. Our targets reveal clear signposts of youth, thus corroborating their cluster membership and planetary masses (6-13 M Jup ). These observations complete the σ Orionis mass function by spectroscopically confirming the planetary-mass domain to a confidence level of ∼75 percent. The comparison of our spectra with BT-Settl solar metallicity model atmospheres yields a temperature scale of 2350-1800 K and a low surface gravity of log g ≈ 4.0 [cm s−2 ], as would be expected for young planetary-mass objects. We discuss the properties of the cluster least-massive population as a function of spectral type. We have also obtained the first optical spectrum of S Ori 70, a T dwarf in the direction of σ Orionis. Our data provide reference optical and near-infrared spectra of very young L dwarfs and a mass function that may be used as templates for future studies of low-mass substellar objects and exoplanets. The extrapolation of the σ Orionis mass function to the solar neighborhood may indicate that isolated planetarymass objects with temperatures of ∼200-300 K and masses in the interval 6-13-M Jup may be as numerous as very low-mass stars.

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Section: Masses and σ Orionis Mass Functionsupporting

confidence: 79%

Optical and Near-infrared Spectra of σ Orionis Isolated Planetary-mass Objects

Osorio

Béjar

Ramírez

2017

ApJ

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“…In particular, the optical spectrum of 2M0335+23 is definitely "earlier" (warmer) than young M9 brown dwarf 2MASS J06085283-2753583 (Cruz et al 2003) which may be a BPMG member (Rice et al 2010) or more likely a 40-Myr-old Columba member (Liu et al 2016). The observed Hα emission line strength of EW≈ 5Å imply log Hα/L bol ≈ −5.5 (Schmidt et al 2014b). Despite 2M0335+23's rapid rotation and youth, this places it in the bottom half of the M7 activity range (Schmidt et al 2014a).…”

Section: Target Characteristicsmentioning

confidence: 95%

K2 Ultracool Dwarfs Survey. II. The White Light Flare Rate of Young Brown Dwarfs

Gizis

Paudel

Mullan

et al. 2017

ApJ

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We use Kepler K2 Campaign 4 short-cadence (one-minute) photometry to measure white light flares in the young, moving group brown dwarfs 2MASS J03350208+2342356 (2M0335+23) and 2MASS J03552337+1133437 (2M0355+11), and report on long-cadence (thirty-minute) photometry of a superflare in the Pleiades M8 brown dwarf CFHT-PL-17. The rotation period (5.24 hr) and projected rotational velocity (45 km s −1 ) confirm 2M0335+23 is inflated (R ≥ 0.20R ) as predicted for a 0.06M , 26-Myr old brown dwarf βPic moving group member. We detect 22 white light flares on 2M0335+23. The flare frequency distribution follows a power-law distribution with slope −α = −1.8 ± 0.2 over the range 10 31 to 10 33 erg. This slope is similar to that observed in the Sun and warmer flare stars, and is consistent with lower energy flares in previous work on M6-M8 very-low-mass stars; taken the two datasets together, the flare frequency distribution for ultracool dwarfs is a power law over 4.3 orders of magnitude. The superflare (2.6 × 10 34 erg) on CFHT-PL-17 shows higher energy flares are possible. We detect no flares down to a limit of 2 × 10 30 erg in the nearby L5γ AB Dor Moving Group brown dwarf 2M0355+11, consistent with the view that fast magnetic reconnection is suppressed in cool atmospheres. We discuss two multi-peaked flares observed in 2M0335+23, and argue that these complex flares can be understood as sympathetic flares, in which a fast-mode MHD waves similar to EUV waves in the Sun trigger magnetic reconnection in different active regions.

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“…The activity strength for the W11 DR7 M0-M6 dwarfs was calculated based on their measured EW and the χ-spectral type relation from , and for the M7-M9 dwarfs in the BUD sample using the relation from Schmidt et al (2014). Activity strength as a function of spectral type for the DR7 M dwarfs (M0-M6) and the BUD sample (M7-M9) is shown in Figure 6.…”

Section: Tablementioning

confidence: 99%

Boss Ultracool Dwarfs. I. Colors and Magnetic Activity of M and L Dwarfs

Schmidt

Hawley

West

et al. 2015

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119

205

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We present the colors and activity of ultracool (M7-L8) dwarfs from the Tenth Data Release of the Sloan Digital Sky Survey (SDSS). We combine previous samples of SDSS M and L dwarfs with new data obtained from the Baryon Oscillation Sky Survey (BOSS) to produce the BOSS Ultracool Dwarf (BUD) sample of 11820 M7-L8 dwarfs. By combining SDSS data with photometry from 2MASS and the Wide-field Infrared Sky Explorer (WISE) mission, we present ultracool dwarf colors from3 as a function of spectral type, and extend the SDSS-2MASS-WISE color locus to include ultracool dwarfs. Thei z, -i J, andz J colors provide the best indication of spectral type for M7-L3 dwarfs. We also examine ultracool dwarf chromospheric activity through the presence and strength of Hα emission. The fraction of active dwarfs rises through the M spectral sequence until it reaches ∼90% at spectral type L0. The fraction of active dwarfs then declines to 50% at spectral type L5; no Hα emission is observed in the late-L dwarfs in the BUD sample. The fraction of active L0-L5 dwarfs is much higher than previously observed. The strength of activity declines with spectral type from M7 through L3, after which the data do not show a clear trend. Using one-dimensional chromosphere models, we explore the range of filling factors and chromospheric temperature structures that are consistent with Hα observations of M0-L7 dwarfs. M dwarf chromospheres have a similar, smoothly varying range of temperature and surface coverage, while L dwarf chromospheres are cooler and have smaller filling factors.

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Calibrating Ultracool Dwarfs: Optical Template Spectra, Bolometric Corrections, and χ Values¹

Cited by 31 publications

References 72 publications

Optical and Near-infrared Spectra of σ Orionis Isolated Planetary-mass Objects

Optical and Near-infrared Spectra of σ Orionis Isolated Planetary-mass Objects

K2 Ultracool Dwarfs Survey. II. The White Light Flare Rate of Young Brown Dwarfs

Boss Ultracool Dwarfs. I. Colors and Magnetic Activity of M and L Dwarfs

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Calibrating Ultracool Dwarfs: Optical Template Spectra, Bolometric Corrections, and χ Values1

Cited by 31 publications

References 72 publications

Optical and Near-infrared Spectra of σ Orionis Isolated Planetary-mass Objects

Optical and Near-infrared Spectra of σ Orionis Isolated Planetary-mass Objects

K2 Ultracool Dwarfs Survey. II. The White Light Flare Rate of Young Brown Dwarfs

Boss Ultracool Dwarfs. I. Colors and Magnetic Activity of M and L Dwarfs

Contact Info

Product

Resources

About

Calibrating Ultracool Dwarfs: Optical Template Spectra, Bolometric Corrections, and χ Values¹