María Rosa Zapatero Osorio (CAB, CSIC-INTA) › users › CONSOLIDER › SEA2010 › Charlas › ... · 2010-10-05 · M5 L0 L5 M5 L0 L5 It is in the near- and mid-infrared wavelengths

The infrared overluminosity of young, ultracool substellar objectsMaría Rosa Zapatero Osorio

(CAB, CSIC-INTA)

Collaborators: R. Rebolo (IAC), V. J. S. Béjar (IAC), J. Caballero (CAB), G. Bihain (IAC), C. Álvarez (GTC, IAC)

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Tuesday, October 5, 2010

Bihain et al. (2010)

Near-infrared spectra (NICS/TNG) of Pleiades late-M and L-type brown dwarfs.

Some show the “triangular” shape at around 1.6 µm even at the age of 120

Myr, a feature believed to be caused by a low-gravity atmosphere.

The Pleiades (120 Myr)


Cruz et al. (2009)

LiI

>550 L dwarfs known in the field. About 5-10% appear to have less than 300 Myr.


Rebolo et al. (1998)

G 196-3B, a young L3-type dwarf with lithium

Small proper motion companion located at 16” from a low-mass (M2.5)

star with significant X-ray emission.






The M2.5 star, G 19-3A, has spectroscopic

properties resembling those of young stars

members of a Per (~80 Myr) and the Pleiades (120 Myr). Likely age of the system < 300 Myr.






The M2.5 star, G 19-3A, has spectroscopic

properties resembling those of young stars

members of a Per (~80 Myr) and the Pleiades (120 Myr). Likely age of the system < 300 Myr.

ALFOSC/NOT spectrum confirmed the ultracool

nature of G 196-3B (Teff = 1870 K). We determined a

probable mass in the range 10-40 Mjup.


Cruz et al. (2009)

Optical spectroscopy (Keck and Gemini

data) of the young, field L-type dwarfs.

The atomic feature due to KI is very

sensitive to gravity. High gravity (≈ high

atmospheric pressure) produces

deeper alkaline lines.

It is believed these objects have ages in the interval 10-300

Myr.


2MASS J1146345+223053 (L3)

Kelu 1 (L2)

G 196 3B

KI H O2 FeH H O2KI COH O2

VOCrH,FeH

NaI

FeH

H O2

FeH H O2

Zapatero Osorio et al. (2010)


There are also gravity-sensitive spectral

features in the near-infrared wavelengths, like the “triangular” shape of the H-band, and the stronger H2O band at around 1.2 µm.


M5 L5L0

G196 3B

M5 L5L0

G 196-3B

In the visible, young and “old” field dwarfs show similar photometric properties.

The infrared overluminosity of young, ultracool substellar objects


M5 L0 L5M5 L0 L5

It is in the near- and mid-infrared wavelengths where we find discrepancies: the young field objects show redder colors than “old” dwarfs of similar spectral

classification.

G 196-3B

G 196-3A

G 196-3B

Other young sources

High-gravity dwarfs



M5 L0 L5 M5 L0 L5

It is in the near- and mid-infrared wavelengths where we find discrepancies: the young field objects show redder colors than “old” dwarfs of similar spectral

classification.

G 196-3B G 196-3B

High-gravity dwarfs




G 196-3B

With disk

Without disk


G 196-3B


M5 L0 L5

G 196-3B

Other young sources


This behavior is NOT reproduce by current theory of model atmospheres.

Lyon models

1 Myr10 Myr

100 Myr

500 Myr1 Gyr

L5L1M8


120 Myr 3 Myr

L0 L5 L0 L0L5 L5

??? Myr



G 196-3BField L2-L3BB 1800K

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I

KH

4.5

3.6

8.0

5.8

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The infrared overluminosity of young, ultracool substellar objects: G 196-3B.

The spectral energy distribution of G 196-3B is that of an L2-L3 source up to the H-band, but it is clearly overluminous at longer wavelengths.



Combined fluxField L2 L3G 196 3B

Black body 1400 K


The spectral energy distribution of G 196-3B is reasonably modeled by the combined flux of a field L2-L3 source (~2000 K) and a single-temperature

black-body of 1400 K with the same luminosity than the L2-L3 source.



Combined fluxField L2 L3G 196 3B

Black body 1400 K


The spectral energy distribution of G 196-3B is reasonably modeled by the combined flux of a field L2-L3 source (~2000 K) and a single-temperature

black-body of 1400 K with the same luminosity than the L2-L3 source.

A possible scenario: a low-gravity atmosphere with enshrouded upper atmospheric layers and/or a warm

dusty disk/envelope.




We are measuring the parallax of 10 of these young, field L dwarfs. Distance is a key parameter to break the degeneracy between age, mass, and luminosity.

Our sample is expected to lie at distances 10-50 pc.



For G 196-3, distance is fundamental to test evolutionary models (e.g., one single

isochrone must reproduce both the star and the substellar companion). Our preliminary

parallax measurement “sets” G 196-3A and B very close to the 20-50 Myr isochrones ( ). At these young ages, the mass of G 196-3B is close to the planetary borderline, i.e., 12

Mjup.

G 196-3B

G 196-3A



Conclusions:

Young (20-300 Myr), field L0-L5 dwarfs (very likely brown dwarfs with M = 10-40 Mjup) show infrared flux excesses, which are not explained by theory.

Distance is a critical parameter to determine the age and mass of these objects and to establish their properties.

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María Rosa Zapatero Osorio (CAB, CSIC-INTA) › users › CONSOLIDER › SEA2010 › Charlas › ... · 2010-10-05 · M5 L0 L5 M5 L0 L5 It is in the near- and mid-infrared wavelengths