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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).

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Fuerteventura, Spain – May 25, 2013

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  1. 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) Fuerteventura, Spain – May 25, 2013

  2. Contents • Observations • Data Reduction • Synthetic models • Preparation of the data • Analysis and Results • Conclusions

  3. Observations • 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

  4. 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

  5. Desphande et al. 2012

  6. Data Reduction II Zapatero Osorio et al. 2009

  7. Some reduced spectra

  8. Deshpande et al. 2012

  9. Synthetic models I • Drift-PHOENIX code (for Teff < 3000 K) is a merger of the general purpose stellar atmosphere code PHOENIX (Hauschildt & Baron1999) 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 • 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

  10. Synthetic models II Flow chart of Drift-Phoenix Dust formation mechanism

  11. M-L and L-T transitions Drift PHOENIX

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

  13. Preparation of the data I • 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.) • Convolution with a Gaussian that mimics the instrumental profile along the dispersion axis. • Spectra were finally rebinned to the same resolutionof the observations • Modelled spectra are normalized over the wavelength range corresponding to order 61

  14. 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

  15. 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

  16. Analysis: observations vr 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

  17. Just a few examples for ... M5.0 - GJ1156 M6.0 - GJ406 M5.5 - J00045753-1709369 M7.0 - J23312174-2749500 ... order 64 M9.5 - J1733189+463359 M8.0 - J22062280-2047058 M8.5 - J18353790+3259545

  18. J00045753-1709369 M5.5 Average Teff=3000 K logg = 5.1 [cgs] vsini = 37 Km/s Vsini= 40, 33 Km/s

  19. J15460540+3749458 M7.5 Order 64 Teff=2800 K logg = 5.5 [cgs] vsini = 22 Km/s Order 60 Teff=2300 K logg = 4.5 [cgs] vsini = 25 Km/s Order 57 Teff=3000 K logg = 5.0 [cgs] vsini = 25 Km/s

  20. 2MJ1733+4633 M9.5 Order 64 Teff=2700 K logg = 5.5 [cgs] vsini = 30 Km/s Order 60 Teff=2100 K logg = 4.5 [cgs] vsini = 31 Km/s Order 56 Teff=2800 K logg = 4.5 [cgs] vsini = 20 Km/s

  21. 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

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