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Luhman 16AB: A Remarkable, Variable,
L/T Transition Binary at 2 pc
Adam J. Burgasser (UC San Diego) Jacqueline Faherty (U. Chile), Yuri Beletsky (Magellan Obs), Jacqueline
Radigan (STScI), Michael Gillon (U. Liege), Peter Plavchan (Caltech/IPAC), Nidia Morrell (Magellan Obs.), Rachel Osten (STScI), Rachel Street (LCO), Carl Melis (UC San Diego), Amaury Triaud (MIT) & Robert Simcoe (MIT)
WISE 1049-‐5319AB aka Luhman 16AB
Identified by Luhman (2013) in a proper motion/very cold source search of multi-‐epoch WISE data (2MASS dropouts).
µ = 2.78 “/yr, detection back in 1978
R = 18.6, J = 10.7, Ks = 8.8, W2 = 7.3
b = 5º (are you kicking yourself yet?)
d = 2.02±0.15 pc – 3rd closest system to Sun (closest to α Centauri)
Kinematics nominally consistent with normal field dwarf system, but a suggested association with Argus (Mamajek 2013)
http://xkcd.com/1212
Why is this source so awesome?
• It is a binary that is both well-‐separated (1”5) and relatively tight (3.1 AU, P ≈ 20-‐40 yr)
• It is a flux reversal binary straddling the L dwarf/T dwarf transition
• It is highly variable in the optical
Easy spectroscopic follow-‐up Resolved optical (Kniazev et al. 2013) and near-‐infrared (Burgasser et al. 2013) spectroscopy and photometry has been published,
Classified L7.5-‐L8 + T0-‐T0.5 optical & NIR
Why is this source so awesome?
• It is a binary that is both well-‐separated (1”5) and relatively tight (3.1 AU, P ≈ 20-‐40 yr)
• It is a flux reversal binary straddling the L dwarf/T dwarf transition
• It is highly variable in the optical
cf. SDSS 1534+1615AB (Liu et al. 2006) 2MASS 1404-‐3159AB (Looper et al. 2008) spectral binary candidates (Burgasser et al. 2010; Geiβler et al. 2011; Day-‐Jones et al. 2013)
Burgasser et al. (2013) also Kniazev et al. (2013)
A late bloomer?
Luhman 16A & B are both red and underluminous @ J for their spectral types; young and/or cloudy? (cf. Looper et al. 2008)
Burgasser et al. (2013)
L7-‐L8 T0-‐T1
Why is this source so awesome?
• It is a binary that is both well-‐separated (1”5) and relatively tight (3.1 AU, P ≈ 20-‐40 yr)
• It is a flux reversal binary straddling the L dwarf/T dwarf transition
• It is highly variable in the optical
ESO/TRAPPIST
Michael Gillon
Gillon et al. (2013) 4.87±0.01 hr binary period variability appears to originate from T dwarf
ATCA (5/2)
Keck/NIRSPEC IRTF/SpeX
IRTF/CSHELL
ESO/TRAPPIST Magellan/FIRE Magellan/MagE DuPont/Retrocam CTIO/Andicam CTIO/Las Cumbres
SAAO/ Las Cumbres
2013 April 22-‐28 Monitoring Campaign
NIR & Optical imaging and spectroscopy + radio interferometry Goals: characterize panchromatic variability, measure radial &
rotational velocities, search for magnetic emission
• ESO TRAPPIST
– optical variability: published (Gillon et al. 2013) • LCO/Retrocam + CTIO/Andicam + NTT/SofI
– optical and NIR variability: analysis underway (Radigan & Faherty) • Las Cumbres Chile + South Africa
– semi-‐continuous monitoring: analysis underway (Street) • Magellan/FIRE: NIR resolved moderate resolution (multi-‐epoch)
– improved RV & ΔRV and association membership: analysis complete (Faherty) – spectral variability: analysis underway (Faherty)
• Magellan/MagE: Optical resolved moderate resolution (multi-‐epoch) – spectral variability incl. Hα & Li I: analysis underway (Beletsky & Faherty)
• IRTF/SpeX: NIR resolved spectral monitoring
– component classification: submitted (Burgasser et al. 2013) – spectral variability: analysis underway (Burgasser)
• IRTF/CSHELL: NIR resolved high resolution – v sin i & ΔRV: analysis underway (Plavchan)
• Australian Telescope Compact Array – search for radio emission: analysis underway (Osten)
2013 April 22-‐28 Monitoring Campaign
SOFI/NTT monitoring • Apr 27 2013 (J. Radigan)
• Non-ideal conditions (2” seeing) – combined light photometry
• J and K alternating
• fastPhot mode: variable “shade” pattern frame to frame currently limiting data reduction
achromatic trends
color variation
Magellan/FIRE
0.8 1.0 1.2
Nor
mal
ized
Flu
x (F
)
1.4 1.6 1.8Wavelength (!m)
Luhman16A + L8 Standard
Luhman16B + T0 Standard
2.0 2.2 2.4
Faherty et al. (in prep)
Faherty et al. (in prep)
Magellan/FIRE
0.8 1.0 1.2
Nor
mal
ized
Flu
x (F
)
1.4 1.6 1.8Wavelength (!m)
Luhman16A + L8 Standard
Luhman16B + T0 Standard
2.0 2.2 2.4
0.95 1.00 1.05 1.10Wavelength (!m)
Nor
mal
ized
Flu
x (F
)
FeH
FeH
CH4+H20
Luhman 16A
Luhman 16B
2.00 2.05 2.10 2.15 2.20 2.25 2.30 2.35Wavelength (!m)
Norm
alize
d Fl
ux (F
) CO
CH4
CIA H2
Luhman 16A
Luhman 16B
1.15 1.20 1.25 1.30 1.35Wavelength (!m)
Norm
alize
d Fl
ux (F
)
Na
H2OFeH
CH4
1.45 1.50 1.55 1.60 1.65 1.70 1.75Wavelength (!m)
Nor
mal
ized
Flu
x (F
)
FeHCH4
Luhman 16A
Luhman 16B
Not an Argus member
1.242 1.245 1.248 1.251 1.254Wavelength (!m)
Norm
alize
d Fl
ux (F
)
Luhman 16A
Luhman 16B
2M1632 (L8 top)SD0151 (T1 bottom)
K I lines are strong, inconsistent with low surface gravity (Faherty et al. in prep)
With RV, kinematics are inconsistent with membership in any known moving group (Kniazev et al. 2013)
1.240 1.245 1.250 1.255Wavelength (!m)
0.4
0.6
0.8
1.0
1.2
Nor
mal
ized
F
1.15 1.20 1.25 1.30 1.35Wavelength (!m)
No
rmal
ized
Flux
(F)
Na
H2OFeH
CH4
K I lines: Teff and clouds
Luhman 16A Luhman 16B
1.240 1.245 1.250 1.255Wavelength (!m)
0.4
0.6
0.8
1.0
1.2
Nor
mal
ized
F
1.15 1.20 1.25 1.30 1.35Wavelength (!m)
No
rmal
ized
Flux
(F)
Na
H2OFeH
CH4
K I lines: Teff and clouds
Luhman 16A Luhman 16B
Burgasser et al. (2002); McGovern et al. (2004)
1.240 1.245 1.250 1.255Wavelength (!m)
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Abso
lute
F (1
0-17 e
rg/c
m2 /s
/!m
)1.15 1.20 1.25 1.30 1.35Wavelength (!m)
No
rmal
ized
Flux
(F)
Na
H2OFeH
CH4
K I lines: Teff and clouds
J-‐band continuum is dictated by cloud grain scattering
Luhman 16A Luhman 16B
1.165 1.170 1.175 1.180Wavelength (!m)
0.4
0.6
0.8
1.0
1.2
1.4
Nor
mal
ized
F
1.15 1.20 1.25 1.30 1.35Wavelength (!m)
No
rmal
ized
Flux
(F)
Na
H2OFeH
CH4
K I lines: Teff and clouds
Luhman 16A Luhman 16B
1.165 1.170 1.175 1.180Wavelength (!m)
0.4
0.6
0.8
1.0
1.2
1.4
1.6
Abso
lute
F (1
0-17 e
rg/c
m2 /s
/!m
)1.15 1.20 1.25 1.30 1.35Wavelength (!m)
No
rmal
ized
Flux
(F)
Na
H2OFeH
CH4
K I lines: Teff and clouds
1.17 µm continuum is dominated by H2O and CH4 opacity
Luhman 16A Luhman 16B
1.240 1.245 1.250 1.255Wavelength (!m)
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Abso
lute
F (1
0-17 e
rg/c
m2 /s
/!m
)
1.165 1.170 1.175 1.180Wavelength (!m)
0.4
0.6
0.8
1.0
1.2
1.4
1.6
Abso
lute
F (1
0-17 e
rg/c
m2 /s
/!m
)
1.15 1.20 1.25 1.30 1.35Wavelength (!m)
No
rmal
ized
Flux
(F)
Na
H2OFeH
CH4
K I lines: Teff and clouds
Luhman 16A Luhman 16B
1.160 1.165 1.170 1.175 1.180 1.185Wavelength (µm)
1700
1600
1500
1400
1300
1200
1100
Brig
htne
ss T
empe
ratu
re (K
)
1.235 1.240 1.245 1.250 1.255 1.260Wavelength (µm)
1700
1600
1500
1400
1300
1200
1100
Brig
htne
ss T
empe
ratu
re (K
)
1.15 1.20 1.25 1.30 1.35Wavelength (!m)
No
rmal
ized
Flux
(F)
Na
H2OFeH
CH4
K I lines: Teff and clouds
Luhman 16A Luhman 16B
ΔT = 100 K
shallow
deep
SpeX Spectroscopic Monitoring
Data
Model
Residuals
“Spectroscopic monitoring is a black art” -‐ anonymous
Luhman 16AB was monitored for 45 minutes with IRTF/SpeX during a downturn in TRAPPIST photometry NB: 1.2”-‐1.5” seeing, airmass = 3.4-‐3.5
Unambiguous Flux Reversal
0 10 20 30 40Pixels
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Profile
J K
1.0 1.2 1.4 1.6 1.8 2.0 2.2Wavelength (!m)
0
2•10-15
4•10-15
6•10-15
8•10-15
1•10-14
Appa
rent
F
Luhman 16A Luhman 16B
h4p://youtu.be/DIJx0flF6uc
6.2 6.4 6.6UT Time on 26 April 2013 (hours)
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15R
elat
ive
Flux
(B/A
) TRAPPIST light curve
Continuum Flux + 0.1
Band Flux - 0.1
Relative fluxes (B/A) show similar decline as broadband photometry
No difference between continuum and band fluxes
Consistent with a decline in B’s brightness, but better calibration is required
high resolution optical spectroscopy with
MIKE to measure ΔRV
v sin i measurements with CSHELL + 13CH4 gas cell (Anglada-‐Escudé et al. 2012)
multi-‐color continuous
photometry with the Las Cumbres
network
most stringent radio and Hα flux constraints for brown dwarfs
improved NIR spectral monitoring with HST/
WFC3 (cf. Apai et al. 2013)
tighter parallax and
proper motion
measures
let’s test those cloudy
atmosphere models! (cf. Leggett
et al. 2008)
MIR variability
with Spitzer/IRAC (cf. Heinze
et al. 2013)
orbit constraints, masses soon(astro + RV)
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