Accreting Brown Dwarf and Disc, Spectra and Photometry Nathan Mayne , Tim Harries
TORUS model
We have used the TORUS radiative transfer code which is described
in
Harries (2000), including the subsequent refinements i.e.
addition of AdaptiveMeshRefinement (AMR) introduced in
Harries et al (2004) . TORUS uses the criterion of
Lucy (1999) in a radiative equilibrium algorithm. The code
can also calculates Vertical hydrostatic equilibrium for the disc,
as described in
Tannirkulam et al (2007). The code also includes a treatment
of dust sublimation where the initial temperatures in the grid are
derived and the grid is then progressively filled to increasing
optical depth limits and temperatures recalculated, with the dust
reaching the dust sublimation temperature being destroyed at each
step.
Grid Description:
These webpages describe and allow access to models and results
from different grids. The details of the parameter coverage and
physics included in each grid can be found in the table below:
Adhoc: STATUS=COMPLETE A grid designed to explore the
effects of accretion on disc structure, including variable dust
sublimation and vertical hydrostatic equilibirum (as well as
analytical structures). SEDs derived using isotropuc scattering. The
results of this grid have been published in Mayne and
Harries (2010) and are discussed throughout these pages using the
term "Adhoc" grid.

Input parameter

Values (number of values)


Stellar parameters

Stellar Interior Model

Dusty'00 Chabrier et al (2000)

Stellar Atmosphere Model

AMESDusty Chabrier et al (2000)

Age (Gyrs)

0.001 and 0.01 (2)

Mass (M_{sol})

0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07 and 0.08 (8)

Rotation period (days)

0.5 and 5 (2)

Accretion rate (log(M_{acc}/M_{sol}^{yr})

12, 11, 10, 9, 8, 7 and 6 (7)

Areal coverage (%)

1 and 10 (2)

Disc parameters

Disc mass (M_{*})

(0.0) 0.01 and 0.001 (2,3)

Disc outer radius (AU)

100 and 300 (2)

Vertical hydrostatic equilibrium (or analytic structure)

yes and no (2)

Dust sublimation

Variable dust sublimation (1)

Scattering

Isotropic (1)

α (β) (for analytic models)

2.00 (1.00), 2.10 (1.10) and 2.25 (1.25)

Inclinations (deg) (for nonzero disc mass)

0, 27, 39, 48, 56, 64, 71, 77, 84 and 90 (10)

Total Models

448 (naked stars, 448 SEDs), 17,92 (vertical hydro, 17,920 SEDs), 5376 (analytic models, 53760 SEDs). 72128 SEDs total.


SemiEmpirical: STATUS=COMPLETE A grid designed for the
derivation of stellar parameters. Disc structures use analytically
described density distributions and dust sublimation radii, SEDs are
derived using full Mie phase scattering. This grid is currently in
preparation and is termed the "Semiemp" grid.

Input parameter

Values (number of values)


Stellar parameters

Stellar Interior Model

M_{*}<0.02M_{sol}: Dusty'00 Chabrier et al (2000).
M_{*}>=0.02M_{sol}: BACH98 Baraffe et al (1998).

Stellar Atmosphere Model

T_{eff}<1400K:AMESCond Chabrier et al (2000)
1400K< T_{eff}<2500K: AMESDusty Chabrier et al (2000)^{(1)}
T_{eff}>2500K: NextGen Hauschildt et al (1999)

Age (Gyrs)

0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009 and 0.01 (10)

Mass (M_{sol})

0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30 and 1.40 (23)

Rotation period (days)

1 and 5 (2)

Accretion rate (log(M_{acc}/M_{sol}^{yr})

12 (1)

Areal coverage (%)

10 (1)

Disc parameters

Disc mass (M_{*})

(0.0) 0.01 and 0.001 (2,3)

Disc outer radius (AU)

50 and 100 (2)

Vertical hydrostatic equilibrium (or analytic structure)

no (1)

Dust sublimation

Analytical sublimation radius (1)

Scattering

Full Mie phase (1)

α (β) (for analytic models)

2.00 (1.00), 2.10 (1.10) and 2.25 (1.25)

Inclinations (deg) (for nonzero disc mass)

0, 27, 39, 48, 56, 64, 71, 77, 84 and 90 (10)

Total Models

460 (naked stars, 460 SEDs). 55200 for disc systems, 55660 SEDs total.

(1) Between 1700 and 1400K the AMESSettl atmospheres are being introduced but currently experimental.
Broadband Photometry and Monochromatic Fluxes
In addition to the magnitudes and colours derived and analysed in
Mayne and
Harries (2010), which are accesible through the Isochrones and Mass Tracks tool,
we have derived magnitudes for several other filter sets. We have also
derived monochromatic fluxes for each of the filters used.
Magnitudes
( Table of response function sources)
The magnitudes are defined using:
M=2.5Log_{10}(Number of
e^{})Zeropoint.
If you would like magnitudes or fluxes for another filter set please
email: nathan@astro.ex.ac.uk. The filters are named as SET_BAND, so a
Bessell U filter is named bessell_U.
Integration and Zeropoints
( Table of zeropoints)
Dependent on whether the responses used are in e^{}/Photon
or in e^{}/(Unit Energy), integration was performed over
either photons or energy (as described in Bessell
et al. 2000, in λ space).
Zeropoints either came from literature sources or were derived
using a Vega spectrum.
Monochromatic fluxes
( Table of assumed SED shape and
effective/central λ's)
Derivation of monochromatic fluxes requires a knowledge of the
assumed SED shape used for each filter set. Each quoted monochromatic
flux is essentially the value of the flux at a given central or
effective λ derived by taking the integrated flux and distributing
it over an assumed SED shape (across the filter response). Effectively
this means integration over the filter response for our input SEDs
must be modified allowing quotation of a monochromatic flux comparable
to observation. Essentially, we are asking what would an observer
(with no knowledge of the underlying SED) quote as a monochromatic
flux for this filter. For our data we have two main cases:
(1) Flat=λ F_{λ} ∝
Constant
(2) 10,000K BB=λ^{4} F_{λ} ∝
Constant
We adopt (1) as a default and quote fluxes derived in this fashion if
no other assumption is explicit. Integration then proceeds (dependent
on the form of the response function) across the filter response
modified for each case, with a similar process as explained in
Appendix A of
Thomas Robitaille's thesis.
Basically, as,
E=∫ U(λ) F_{λ}[actual]R(λ)dλ/(∫
R_{λ}dλ) = ∫
U(λ) F_{λ}[assumed]R(λ)dλ/(∫
R_{λ}dλ),
where U(λ)=1 for a R(λ) in e^{}/(Unit
energy) or λ/(hc) for R(λ) in e^{}/Photons,
and λ F_{λ}[assumed] ∝ Either case (1)
or (2) above≡
λ_{0}F_{ λ0}[quoted].
Meaning the assumed SED shape must be substituted into the flux
integration. Therefore to quote monochromatic fluxes for each filter
requires the assumed SED shape and effective/central λ.
Details, values and tables.
The filter prefix names and response function sources (and units)
are all listed in this table.
The suffix names, zeropoints (and source), assumed SED shapes,
effective/central λ's and bandwidths are also available in this table.
If uploading Spectras for fitting please use a two column (ascii)
space separated file, with wavelength in the first and flux in the
second column (uncertainties, if included then should be placed in the
third column). Fluxes and wavelengths must be in one of the supported
units (see Fitting tool options). Comment lines
must be preceded by a # and appear at the top of the file (not
interspersed in the data). NOTE, this option can now be used to
include a collection of monochromatic fluxes.
