<p>Quoting from Wikipedia,</p>

<blockquote>
  <p>The bolometric magnitude Mbol, takes into account electromagnetic
  radiation at all wavelengths. It includes those unobserved due to
  instrumental pass-band, the Earth's atmospheric absorption, and
  extinction by interstellar dust. It is defined based on the luminosity
  of the stars. In the case of stars with few observations, it must be
  computed assuming an effective temperature. Classically, the
  difference in bolometric magnitude is related to the luminosity ratio
  according to:</p>
</blockquote>

<p>$ M_{bol,*} - M_{bol,sun} = -2.5log_{10}(\frac{L_*}{L_{sun}})$</p>

<blockquote>
  <p>In August 2015, the International Astronomical Union passed Resolution
  B2[7] defining the zero points of the absolute and apparent bolometric
  magnitude scales in SI units for power (watts) and irradiance (W/m2),
  respectively. Although bolometric magnitudes had been used by
  astronomers for many decades, there had been systematic differences in
  the absolute magnitude-luminosity scales presented in various
  astronomical references, and no international standardization. This
  led to systematic differences in bolometric corrections scales, which
  when combined with incorrect assumed absolute bolometric magnitudes
  for the Sun could lead to systematic errors in estimated stellar
  luminosities (and stellar properties calculated which rely on stellar
  luminosity, such as radii, ages, and so on).</p>
</blockquote>

<p>[leading to the accepted definition of]
$ M_{bol} = -2.5log_{10}(L_*) + 71.1974... $ , where the constant term is the zero-point luminosity $L_0$ .</p>

<p>Dunno if this helps, other than that you have to determine the spectral luminosity of the star in question. </p>

CC BY-SA 3.0
2017-04-17T13:00:33.850Z
2017-04-17T13:00:33.850Z
Carl Witthoft
<p>If we know a star's magnitudes from several bands(say u,g,r,i,z,J,H,k) and the star's distance, how to calculate Lbol?</p>

<p>Let's suppose the star has a black body spectrum. Is there any manual about the calculation? It's better to have a lot of technical details.</p>

CC BY-SA 3.0
2017-04-16T08:07:06.880Z
Are you looking​ for something more complicated than find a bolometric correction?
ProfRob
CC BY-SA 3.0
2017-04-16T08:39:45.243Z
@Rob yes, these objects are cool and bright in infrared, but I know their magnitudes from 2MASS and WISE, and even Sloan. Convert magnitudes to flux and fit using a blackbody model  is enough?
questionhang
CC BY-SA 3.0
2017-04-17T08:28:20.087Z
They are certainly not blackbodies. You would need to fit with proper stellar models.
ProfRob
CC BY-SA 3.0
2017-04-17T09:01:44.943Z
@Rob  If we know magnitudes and stellar type, how to calculate Lbol?
questionhang
CC BY-SA 3.0
2017-04-17T12:40:08.733Z
@Rob Do you know any table like this (https://sites.uni.edu/morgans/astro/course/Notes/section2/spectraltemps.html)? Perhaps a table is a more direct way for me, but spectral types are sort of sparse especially for cool objects in this table.
questionhang
CC BY-SA 3.0
2017-04-17T13:45:00.307Z
@Rob A table(especially for cool objects) does not appear in that question.
questionhang
CC BY-SA 3.0
2017-04-20T11:56:27.203Z
I have added a reference to a relevant table for cool objects.
ProfRob
<luminosity>
How to convert magnitudes to bolometric luminosity?
questionhang
# How to convert magnitudes to bolometric luminosity?

(Asked by: username_0 on 2017-04-15)

If we know a star's magnitudes from several bands(say u,g,r,i,z,J,H,k) and the star's distance, how to calculate Lbol?

Let's suppose the star has a black body spectrum. Is there any manual about the calculation? It's better to have a lot of technical details.

**Tags:** luminosity

> **Comments:**
> **username_1**: Are you looking​ for something more complicated than find a bolometric correction?  
> **username_0**: @Rob yes, these objects are cool and bright in infrared, but I know their magnitudes from 2MASS and WISE, and even Sloan. Convert magnitudes to flux and fit using a blackbody model  is enough?  
> **username_1**: They are certainly not blackbodies. You would need to fit with proper stellar models.  
> **username_0**: @Rob  If we know magnitudes and stellar type, how to calculate Lbol?  
> **username_0**: @Rob Do you know any table like this (https://sites.uni.edu/morgans/astro/course/Notes/section2/spectraltemps.html)? Perhaps a table is a more direct way for me, but spectral types are sort of sparse especially for cool objects in this table.  
> **username_0**: @Rob A table(especially for cool objects) does not appear in that question.  
> **username_1**: I have added a reference to a relevant table for cool objects.  

---

## 1 answers

### Answer by username_2 on 2017-04-17. Score: 1

Quoting from Wikipedia,

> The bolometric magnitude Mbol, takes into account electromagnetic
> radiation at all wavelengths. It includes those unobserved due to
> instrumental pass-band, the Earth's atmospheric absorption, and
> extinction by interstellar dust. It is defined based on the luminosity
> of the stars. In the case of stars with few observations, it must be
> computed assuming an effective temperature. Classically, the
> difference in bolometric magnitude is related to the luminosity ratio
> according to:

$ M\_{bol,\*} - M\_{bol,sun} = -2.5log\_{10}(\frac{L\_\*}{L\_{sun}})$

> In August 2015, the International Astronomical Union passed Resolution
> B2[7] defining the zero points of the absolute and apparent bolometric
> magnitude scales in SI units for power (watts) and irradiance (W/m2),
> respectively. Although bolometric magnitudes had been used by
> astronomers for many decades, there had been systematic differences in
> the absolute magnitude-luminosity scales presented in various
> astronomical references, and no international standardization. This
> led to systematic differences in bolometric corrections scales, which
> when combined with incorrect assumed absolute bolometric magnitudes
> for the Sun could lead to systematic errors in estimated stellar
> luminosities (and stellar properties calculated which rely on stellar
> luminosity, such as radii, ages, and so on).

[leading to the accepted definition of]
$ M\_{bol} = -2.5log\_{10}(L\_\*) + 71.1974... $ , where the constant term is the zero-point luminosity $L\_0$ .

Dunno if this helps, other than that you have to determine the spectral luminosity of the star in question.


---

