Original article can be found at: http://www.aanda.org/----Copyright The European Southern ObservatoryPeer reviewe

Jones, H.R.A.

Lyubchik, Y.

Pavlenko, Y.

Pinfield, D.J.

Tennyson, J.

Astronomy and Astrophysics

English

arXiv

We present results of modelling the bulk of the spectral energy distribution (0.45–5 μm) for GJ406 (M6V). Synthetic spectra were calculated using the NextGen model atmospheres of Hauschildt et al. [6] and the incorporate line lists for H2O, TiO, CrH, FeH, CO, MgH molecules as well as the VALD line list of atomic lines. The computed water partition function is in a good agreement with the one obtained by Vidler & Tennyson [14]. A comparison of synthetic and observed spectra gives Teff = 2900 ± 100 K for this late M-dwarf.The William Herschel Telescope and United Kingdom Infrared Telescope are operated for the Particle Physics and Astronomy Research Council (PPARC). ISO is an ESA project with the participation of ISAS and NASA funded from member states. HST is a NASA project funded in part by ESA. This work was partially supported by a PPARC visitors grants from PPARC and the Royal Society. YP’s studies are partially supported by a Small Research Grant from American Astronomical Society. This research has made with the use of the SIMBAD database, operated at CDS, Strasbourg, France

Lyubchik, Yu.

Pavlenko, Ya.V.

Pinfield, D.

Наукова електронна бібліотека періодичних видань НАН України (Vernadsky National Library of Ukraine)

SPECTRAL ENERGY DISTRIBUTION FOR GJ406Yu. Lyubchik1, Ya. V. Pavlenko1, H. R. A. Jones2, J. Tennyson3, D. Pinﬁeld21Main Astronomical Observatory, NAS of Ukraine27 Akademika Zabolotnoho Str., 03680 Kyiv, Ukrainee-mails: lyu@mao.kiev.ua, yp@mao.kiev.ua2Centre for Astrophysics Research, Science and Technology Research Centre, University of HertfordshireCollege Lane, Hatﬁeld, Hertfordshire AL10 9AB, UKe-mail: hraj@star.herts.ac.uk3Department of Physics and Astronomy, University College LondonGower Street, London WC1E 6BT, UKWe present results of modelling the bulk of the spectral energy distribution (0.45–5μm) for GJ406(M6V). Synthetic spectra were calculated using the NextGen model atmospheres of Hauschildtet al. [6] and the incorporate line lists for H2O, TiO, CrH, FeH, CO, MgH molecules as well asthe VALD line list of atomic lines. The computed water partition function is in a good agreementwith the one obtained by Vidler & Tennyson [14]. A comparison of synthetic and observed spectragives Teﬀ = 2900 ± 100 K for this late M-dwarf.INTRODUCTIONThe spectral energy distributions for several model atmospheres with eﬀective temperatures around 3000 Kwere computed and compared with the observed ﬂuxes of GJ406. Using this procedure we pursue severalgoals. First, we test the quality of the existing molecular and atomic line lists. Second, we investigatethe possibility for the use of the NextGen model atmospheres to compute the spectral energy distribution oflate type dwarfs.OBSERVATIONSTable 1 lists the information on observational spectra used for our investigations. The observed ﬂuxes are shownin Fig. 1.Table 1. Observational dataWaverange, μm Instrument (conﬁguration) Telescope Date0.35 – 0.56 ISIS (blue arm) WHT 2001 Jan 290.55 – 0.80 ISIS (red arm) WHT 2001 Jan 290.79 – 1.20 NICMOS (G096) HST 1998 June 191.05 – 1.95 NICMOS (G141) HST 1998 June 191.3 – 2.59 NICMOS (G206) HST 1998 June 192.48 – 2.60 SWS (06 1A) ISO 1996 June 262.60 – 2.75 SWS (06 1A) ISO 1996 June 262.74 – 2.90 SWS (06 1A) ISO 1996 June 262.88 – 3.02 SWS (06 1B) ISO 1996 June 263.03 – 3.23 CGS4 (150 l/mm) UKIRT 1993 April 203.21 – 3.40 CGS4 (150 l/mm) UKIRT 1993 April 203.36 – 3.75 CGS4 (75 l/mm) UKIRT 1992 May 73.76 – 4.15 CGS4 (75 l/mm) UKIRT 1992 May 74.51 – 4.90 CGS4 (75 l/mm) UKIRT 1992 October 26c© Yu. Lyubchik, Ya. V. Pavlenko, H. R. A. Jones, J. Tennyson, D. Pinﬁeld, 2004279 0 1 2 3 4 5 6 7 0.5  1  1.5  2  2.5  3  3.5  4  4.5  5Flux FνWavelength (micron)nmlkjihgfedcbaa) ISIS (blue arm) on WHT at 2001 Jan 29b) ISIS (red arm) on WHT at 2001 Jan 29c) NICMOS (G096) on HST at 1998 June 19d) NICMOS (G141) on HST at 1998 June 19e) NICMOS (G206) on HST at 1998 June 19f) SWS (06 1A) on ISO at 1996 June 26 g) ibidh) ibidi) SWS (06 1B) on ISO at 1996 June 26j) CGS4 (150 l/mm) on UKIRT at 1993 20 Aprilk) ibidl) CGS4 (75 l/mm) at 1992 May 7m) ibidn) CGS4 (75 l/mm) 1992 October 26Figure 1. Observational data used for our analysis. The wavelength coverage of various instruments is shown 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0  0.5  1  1.5  2  2.5  3  3.5  4  4.5  5Normalised Flux F ν + ConstWavelength (micron)H2OCOCrHFeHTiOVALDFigure 2. Contribution of diﬀerent molecules to the formation of spectrum of GJ406PROCEDURESynthetic spectra were computed for the NextGen model atmospheres [6] with the following parameters: eﬀectivetemperatures Teﬀ = 2600–3600 K, log g = 5.0, solar metallicity [1] and microturbulent velocity vt = 2 km/s.Calculations of synthetic spectra were carried out by using the program WITA6 [10] assuming LTE, hydrostaticequilibrium for an one-dimensional model atmosphere and absence of sources and sinks of energy. The equationsof the ionization-dissociation equilibrium were solved for media consisting of atoms, ions, and molecules. Wetook into account about 100 components [10]. The constants for equations of the chemical balance were takenfrom [13].Molecular line data were taken from various sources. The 1H162 O lines were calculated using the AMESdatabase [9]. The partition functions of H2O were also calculated from these data (see [11]). The 12C16O and13C16O line lists were calculated by Goorvitch [4]. The CO partition functions were taken from [5], a TiO linelist – from [12]. CN lines were taken from CDROM 18 by Kurucz [8], CrH and FeH lines – from [2] and [3],respectively. An atomic line list was taken from VALD [7].The relative importance of the diﬀerent opacities contributing to our synthetic spectra is shown in Fig. 2.280 0 1 2 3 4 5 6 0.5  1  1.5  2  2.5  3  3.5  4  4.5  5Normalised Flux F λWavelength(micron)GJ4062600/5.0 0 1 2 3 4 5 6 0.5  1  1.5  2  2.5  3  3.5  4  4.5  5Normalised Flux F λWavelength(micron)GJ4062800/5.0 0 1 2 3 4 5 6 0.5  1  1.5  2  2.5  3  3.5  4  4.5  5Normalised Flux F λWavelength(micron)GJ4063000/5.0Figure 3. Fits of the GJ406 spectra to the theoretical spectra computed for the NextGen model atmospheres281RESULTSDependence of fits on input parametersWe computed synthetic spectra using various input parameters such as eﬀective temperatures, gravities, metal-licities, microturbulent velocities. And we found that temperature has a relatively greater eﬀect on the spectrathan metallicity and gravity. A temperature change of 200 K is roughly equivalent to a change in metallicity of0.5 dex or a gravity of log g = 1.Fits to GJ406 spectraFits of our synthetic spectra, which were computed for the NextGen model atmospheres with diﬀerent Teﬀ ,to the GJ406 spectrum are shown in Fig. 3. Previous studies have considered GJ406 as a typical M6 dwarf,therefore, log g = 5.0 was adopted. From our comparison of computed and observed spectra we assumedTeﬀ = 2900 ± 100 K.Acknowledgements. TheWilliam Herschel Telescope and United Kingdom Infrared Telescope are operated forthe Particle Physics and Astronomy Research Council (PPARC). ISO is an ESA project with the participationof ISAS and NASA funded from member states. HST is a NASA project funded in part by ESA. This workwas partially supported by a PPARC visitors grants from PPARC and the Royal Society. YP’s studies arepartially supported by a Small Research Grant from American Astronomical Society. This research has madewith the use of the SIMBAD database, operated at CDS, Strasbourg, France.[1] Anders E., Grevesse N. Abundances of the elements - Meteoritic and solar // Geodynamics and GeochemistryActa.–1989.–53.–P. 197–214.[2] Burrows A., Ram R. S., Bernath P., et al. New CrH Opacities for the Study of L and Brown Dwarf Atmospheres //Astrophys. J.–2002.–577.–P. 986–992.[3] Dulick M., Bauschlicher C. W., Burrows A., et al. Line Intensities and Molecular Opacities of the FeH F 4Δi−X4ΔiTransition // Astrophys. J.–2003.–594.–P. 651–663.[4] Goorvitch D. Infrared CO line for the X 1 Sigma(+) state // Astrophys. J. Suppl. Ser.–1994.–95.–P. 535–552.[5] Gurvitz L. V., Weitz I. V., Medvedev V. A. Thermodynamic properties of individual substances.–Moscow: Nauka,1989. (in Russian).[6] Hauschildt P. H., Allard F., Baron E. The NextGen Model Atmosphere Grid for 3000≤Teﬀ ≤ 10,000 K // Astro-phys. J.–1999.–512.–P. 377–385.[7] Kupka F., Piskunov N., Ryabchikova T. A., et al. VALD-2: Progress of the Vienna Atomic Line Data Base //Asron. and Astrophys. Suppl. Ser.–1999.–138.–P. 119–133.[8] Kurucz R. L. CDROMs 1–22, Harvard–Smithsonian Observatory.–1993.[9] Partrige H., Schwenke D. J. The determination of an accurate isotope dependent potential energy surface for waterfrom extensive ab initio calculations and experimental data // Chem. Phys.–1997.–106.– P. 4618–4639.[10] Pavlenko Ya. Lithium Lines in the Spectra of M Dwarfs: UX Tau C // Astron. Rep.–2000.–44.–P. 219–226.[11] Pavlenko Ya. Modeling the Spectral Energy Distributions of L Dwarfs // Astron. Rep.– 2001.–45.–P. 144–156.[12] Plez B. A new TiO line list // Astron. and Astrophys.–1998.–337.–P. 495–500.[13] Tsuji T. Molecular abundances in stellar atmospheres. II // Astron and Astrophys.–1973.–23.–P. 411–431.[14] Vidler M., Tennyson J. Accurate partition function and thermodynamic data for water // J. Chem. Phys.–2000.–113.–P. 9766–9771.282

Kinematika i fizika nebesnyh tel (Online)

Spectral energy distribution for GJ406

We present results of modelling the bulk of the spectral
energy distribution (0.35–5 μm) for GJ406 (M6V). Synthetic
spectra were calculated using the NextGen, Dusty and Cond model
atmospheres and incorporate line lists for H2O, TiO, CrH, FeH,
CO, MgH molecules as well as the VALD line list of atomic lines.
A comparison of synthetic and observed spectra gives Teff = $2800\pm 100$ K. We determine $M_{\rm bol}  = 12.13  \pm 0.10$
for which evolutionary
models by Baraffe et al. (2003, A&A, 402, 711) suggest an age of around 0.1–0.35 Gyr consistent with its high activity. The age and
luminosity of GJ406 correspond to a wide range of plausible masses
(0.07–0.1  $M_{\odot}$)

Ya. V. Pavlenko

H. R. A. Jones

Yu. Lyubchik

J. Tennyson

D. J. Pinfield

EDP Sciences OAI-PMH repository (1.2.0)

University of Hertfordshire Research Archive

91 v a nA l t e n a

CDROMs 1-22, Harvard-Smisthonian ObservatoryYa. V. Pavlenko et al.: SEDs of GJ406 717

in Ultra low mass star formation and evolution,

We present results of modelling the bulk of the spectral energy distribution (0.45 - 5 μm ) for GJ406

(M6V). Synthetic spectra were calculated using the NextGen model atmospheres of Hauschildt et al. (1999) and

incorporate line lists for H2O, TiO, CrH, FeH, CO, MgH molecules as well as the VALD line list of atomic lines.

The computed water partition function is in a good agreement with Vider & Tennyson (2000). A comparison of

synthetic and observed spectra give Teff= 2800 ± 100 K. For Mbol = 12.14m we thus derive an age of t = 0.2 -

0.3 Gyr and a mass M = 0.09 MΘfor this archetypal late M-dwarf

Pavlenko, Ya. V.

UCL Discovery

CDROMs 1-22, Harvard-Smisthonian Observatory.

in “Ultra low mass star formation and evolution”,

Physics der Sternatmospharen,

The general catalogue of trigomometric stellar parameters (4-th rev.ed: Schenrctady: L.Davis).

Thermodynamic properties of individual substances.

Spectral energy distribution for GJ406

Abstract

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Наукова електронна бібліотека періодичних видань НАН України (Vernadsky National Library of Ukraine)

EDP Sciences OAI-PMH repository (1.2.0)

University of Hertfordshire Research Archive

UCL Discovery