wrote:
I'm currently working with the infrared flux method (irfm). This
method, is based on the idea that the ratio between the bolometric and
the monochromatic flux (in the infrared) gives you and estimate of the
stellar temperature.

What are you using for the bolometric flux?

So, to get back to my problems, I need to make the ratio between the
bolometric and the monochromatic flux at a chosen wavelength (in the
IR). To have the monochromatic flux I use a model atmosphere (Kurucz)
.....
So, the Kurucz model tell me about the monochromatic flux. In first
approximation the idea is ok, but the risky thing is that a
monochromatic flux at my chosen wavelength can be dominated by
absorption lines. My thinking is therefore to compute the in-band flux
(thus avoiding trouble with absorption lines), and then pick up the
isophotal wavelength corresponding to the in-band flux.

I am not certain, but it looks to me as though you are going about this
backwards. You have some photometric measurement you are trying to
match, right? That measurement is done with a known bandpass. So it
seems to me you want to integrate the model spectrum over the
measurement bandpass and ask what temperature for the model best
matches the data.

Steve Willner (who is not sure why Google won't put his last name in
the From header line)