Fuerteventura, Spain – May 25, 2013 Physical parameters of a sample of M dwarfs from high- resolution near-infrared 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 Observations O Data Reduction O Synthetic models O Preparation of the data O Analysis and Results O Conclusions

NIRSPEC program Targets: 36 late-M dwarfs of magnitudes 7.16 < J < and spectral types M5 – M9.5 (Phan-Bao N., et al., 2003, A&A, 401, 959) Dates: 2007 April 30 th, June 24 th – June 25 th, October 25 th – October 26 th and December 23 rd – 24 th 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 ~ 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 Data Reduction II

Some reduced spectra

Deshpande et al. 2012

1. Drift-PHOENIX code (for T eff < 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 T eff > 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-PhoenixDust formation mechanism

M-L and L-T transitions Drift PHOENIX

M dwarf models M5 M3.5 M2 M1 M0 PHOENIX v16

1.Transformation to take into account the projected rotational velocity (v rot 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: v rot sini: 0 to 75 Km s −1, steps of 1-2 Km s −1, T eff : 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 (v rad, v rot sini, T eff, 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 Analysis: observations vr models

M5.5 - J M9.5 - J M8.5 - J M6.0 - GJ406M5.0 - GJ1156 M8.0 - J M7.0 - J Just a few examples for order 64

J M5.5 Average T eff =3000 K logg = 5.1 [cgs] vsini = 37 Km/s Vsini= 40, 33 Km/s

J M7.5 Order 64 T eff =2800 K logg = 5.5 [cgs] vsini = 22 Km/s Order 60 T eff =2300 K logg = 4.5 [cgs] vsini = 25 Km/s Order 57 T eff =3000 K logg = 5.0 [cgs] vsini = 25 Km/s

2MJ M9.5 Order 64 T eff =2700 K logg = 5.5 [cgs] vsini = 30 Km/s Order 60 T eff =2100 K logg = 4.5 [cgs] vsini = 31 Km/s Order 56 T eff =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