Fuerteventura, Spain – May 25, 2013

Physical parameters of a Physical parameters of a sample of M dwarfs from sample of M dwarfs from

high-resolution near-high-resolution near-infrared spectrainfrared spectra

Carlos del Burgo

Collaborators:

J. T. Vila (UNINOVA)E. L. Martín, M. R. Zapatero Osorio (CAB)

S. Witte, Ch. Helling, P. Hauschildt (Hamburg Sternwarte)R. Deshpande (UCF)

Contents

O ObservationsO Data ReductionO Synthetic modelsO Preparation of the dataO Analysis and ResultsO Conclusions

NIRSPEC program

• Targets: 36 late-M dwarfs of magnitudes 7.16 < J < 12.93 and spectral types M5 – M9.5 (Phan-Bao N., et al., 2003, A&A, 401, 959)

• Dates: 2007 April 30th, June 24th – June 25th, October 25th – October 26th and December 23rd – 24th

• Instrumentation: NIRSPEC spectrograph, KECK II telescope (Hawaii, USA)

• Spectral range: ten/eleven orders in the J-band

• Resolving power: 22,000

Observations

Data Reduction I• ECHELLE/IRAF

• Spectra were got at 2 different positions along the slit

• Nodded images were taken to remove sky background and dark signal

• Flat-fielding using white light spectra

• Spectral calibration using arc line Ar, Kr, Xe + NIST database (line identification): rms ~ 0.5-1 Km/s

• Telluric atmospheric correction using A0-A2 stars

• Details in Zapatero-Osorio et al. 2006, ApJ, 647, 1405

Desphande et al. 2012

Zapatero Osorio et al. 2009

Data Reduction II

Some reduced spectra

Deshpande et al. 2012

1. Drift-PHOENIX code (for Teff < 3000 K) is a merger of the general purpose stellar atmosphere code PHOENIX (Hauschildt & Baron 1999) and the dust model Drift (Helling et al. 2008). The dust grains are composites and yield improved opacities in contrast to the grains in earlier models

2. PHOENIX version 16 (for Teff > 3000 K) includes a number of improvements compared to previous versions, such as a complete new equation of state for ions, molecules and condensation (ACES; Barman et al. 2011), updated opacity databases, and improved line profiles for atomic lines

Synthetic models I

Synthetic models II

Flow chart of Drift-Phoenix Dust formation mechanism

M-L and L-T transitionsDrift PHOENIXDrift PHOENIX

M dwarf models

M5

M3.5

M2

M1

M0

PHOENIX v16PHOENIX v16

1.Transformation to take into account the projected rotational velocity (vrot sini) of the objects using the formalism of Gray (Gray D. F., 1992, “The Observations and Analysis of Stellar Photospheres”, Cambridge University Press, 2nd. ed.)

2. Convolution with a Gaussian that mimics the instrumental profile along the dispersion axis.

3. Spectra were finally rebinned to the same resolution of the observations

4. Modelled spectra are normalized over the wavelength range corresponding to order 61

Preparation of the data I

Preparation of the data II

• A grid of synthetic models was generated: vrotsini: 0 to 75 Km s−1, steps of 1-2 Km s−1, Teff: 1000 and 4000 K with steps of 100 K, and logg: 3.5 and 5.5 (cgs) with steps of 0.5 dex

• Observed spectra were moved to vacuum wavelengths for a proper comparison with the theoretical models. This was done from a cross-correlation analysis with each individual synthetic spectra that allow us to determine RVs

Complementary data

• 2MASS J, H and Ks and WISE W1, W2, and W3 photometric bands

• Cross-correlation of the two catalogs

• SEDs and fit to the France Allard last generation of models available in VOSA, which routines were used to perform the fits of photometric data to those models

• In order to constrain the number of possible solutions provided by our large set of models, the root-mean-square RMS (vrad, vrotsini, Teff, log g) is obtained for each model. The best model is that with the minimum RMS

• For a detailed description see del Burgo et al. 2009

Analysis: observations vr models

M5.5 - J00045753-1709369

M9.5 - J1733189+463359M8.5 - J18353790+3259545

M6.0 - GJ406M5.0 - GJ1156

M8.0 - J22062280-2047058

M7.0 - J23312174-2749500

Just a few examples for ...

... order 64

J00045753-1709369M5.5

AverageTeff=3000 Klogg = 5.1 [cgs]vsini = 37 Km/s

Vsini= 40, 33 Km/s

J15460540+3749458

M7.5

Order 64Teff=2800 K logg = 5.5 [cgs] vsini = 22 Km/s

Order 60Teff=2300 K logg = 4.5 [cgs] vsini = 25 Km/s

Order 57Teff=3000 K logg = 5.0 [cgs] vsini = 25 Km/s

2MJ1733+4633

M9.5

Order 64Teff=2700 K logg = 5.5 [cgs] vsini = 30 Km/s

Order 60Teff=2100 K logg = 4.5 [cgs] vsini = 31 Km/s

Order 56Teff=2800 K logg = 4.5 [cgs] vsini = 20 Km/s

Conclusions

Effective temperatures obtained by means of the fits of stellar atmosphere models to i) J-band spectroscopy (R=22,000) and ii) near-infrared photometry show significant differences.

New improvements in stellar atmosphere models are required for cool dwarfs