# Tag Info

7

The brown dwarf "limit" is about $0.072 M_{\odot}$ at solar metallicity (e.g. Chabrier et al. 2000) and is composition dependent. It gets a little higher in metal-poor gas and a little lower in metal-rich gas. $0.064 \pm 0.012 M_\odot$ (the third significant figure is superfluous) is within one error bar of that limit, which in itself is only a 68% ...

4

You can calculate the absolute magnitude of a star: $$M=m-5\log_{10}(\frac{d}{10\,\text{pc}})$$ where $M$ is absolute magnitude, $m$ is apparent magnitude and $d$ is the distance. Then you take a look at the HR diagram. One can easily see, that you need two data to obtain the third one, but we have only one data (absolute magnitude). That means, that you ...

2

Yes. Stars (those objects that are supported by hydrogen fusion) can be as cool as spectral type L2. Brown dwarfs can be as warm as M4/5 when they are young. i.e. there isn't a clear spectral type Vs mass relationship. It depends on age too.

2

$\eta$ Cassiopeiae A has an estimated mass of 0.972 M$_\odot$, an estimated temperature of 5973 K, and a B-V color index of ~0.58[1]. In addition to the spectrum of the star, we look at these and other properties when attempting to classify main sequence stars. You can see a table [here] which shows the bulk properties of each spectral type that we can use ...

2

The website on Main sequence stars fromr the Austalian national telescope facility lists star mass, temperature and life span: Mass/MSun Luminosity/LSun T=Effective Temperature/K Radius/RSun t=Main sequence lifespan/yrs 0.10 $3×10^{-3}$ 2,900 0.16 $2×10^{12}$ 0.50 0.03 3,800 0.6 $2×10^{11}$ 0.75 0.3 5,000 0.8 $3×10^{10}$ 1.0 1 6,000 1.0 $1×10^{10}$ 1.5 ...

1

I think the issue you are going to have here is that the position of a star in the HR diagram - which amounts to saying what the (2 dimensional) spectral type is - does not just depend on its mass. The Vogt-Russell theorem says that the position of a star on the HR diagram depends on its mass, its composition and crucially, how its chemical elements are ...

1

The spectral type of a star is determined by looking at its spectrum. Sometimes authors will use other, approximate, relationships between spectral type and colour or mass, or they will look at the spectrum compared with standard templates in different wavelength regions. These are all possible reasons why different sources might suggest slightly different ...

1

That I know there is the XHIP catalog via VizieR and you can enter a range in UMag (or B- and V-band) for example of -20 .. 20. Check the box SpType and Tc to get also the spectral type and temperature (double check the literature for the quantities you need) On the column on the left titled Preferences, set the quantity max to unlimited (it's the number of ...

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