<p>The paper you got your relation from states it is only valid for C_XP&lt;1.5.
i.e. For K-type stars and hotter. If you extrapolate a non-linear polynomial fit outside its limits of application then don't be surprised if it returns nonsense values.</p>
<p>You can then see (Fig 9) that the conversion from colour to temperature for redder colours and cooler stars becomes highly sensitive to metallicity, so unfortunately there is no one-to-one mapping between Bp-Rp colour and temperature for those stars.</p>
<p>You might have more luck using G-Rp, which should be less sensitive to metallicity.</p>

CC BY-SA 4.0
2022-04-28T20:46:38.587Z
2022-04-28T20:46:38.587Z
ProfRob
<p>The GAIA database includes <em><strong>teff_gspphot</strong></em> as an existing parameter. The methods used to calculate temperatures are complex, see for example:</p>
<p><a href="https://gea.esac.esa.int/archive/documentation/GDR2/Data_analysis/chap_cu8par/sec_cu8par_process/ssec_cu8par_process_priamteff.html" rel="nofollow noreferrer">https://gea.esac.esa.int/archive/documentation/GDR2/Data_analysis/chap_cu8par/sec_cu8par_process/ssec_cu8par_process_priamteff.html</a></p>
<p>&quot;<em>For our temperature estimation, we refrain from using a simplistic polynomial model, which would make too restrictive a-priori assumptions about the mathematical form of the colour-temperature relation. Instead, we use GBP−G and G−GRP as features to estimate Teff using extremely randomised trees (Geurts et al. 2006, hereafter ExtraTrees). This machine-learning algorithm comes up with a non-parametric model for the colour-temperature relation, which is far more general than a model of polynomial class.</em>&quot;</p>

CC BY-SA 4.0
2024-01-05T12:11:54.753Z
2024-01-05T12:25:51.583Z
2024-01-05T12:25:51.583Z
FleetFoot
<p>For just hobbyist purposes (3D starmap) - I'm trying to infer temperature from EDR3 data to make a rough assessment of stellar type.</p>
<p>I tried applying figure 2 from this doc:
<a href="https://arxiv.org/pdf/1008.0815.pdf" rel="noreferrer">https://arxiv.org/pdf/1008.0815.pdf</a></p>
<p><span class="math-container">$ \log(T_{\mathit{eff}}) = 3.999−0.654(C_{XP})+0.709(C_{XP})^2−0.316(C_{XP})^3 $</span></p>
<p>Where <span class="math-container">$C_{XP} = G_{BP} - G_{RP}$</span> (from Gaia TAP over Astroquery)</p>
<p>However, it seems to only work for G type stars when comparing for known <span class="math-container">$T_{\mathit{eff}}$</span> for the same stars identified in SIMBAD. So with that formula I get 5619 from SIMBAD but 5630 for the G type star.</p>
<p>However, for M stars, with temperature in SIMBAD of 3111, I'm getting values less than 1.</p>
<p>Is there another formula to use for dimmer (and brighter) stars? Or perhaps someone has done preprocessing that is available via TAP somewhere else?</p>
<p>Similarly, I'm curious if there are any groups out there that have identified possible binary/multi-star systems.</p>
<p><a href="https://gitlab.com/godotuniverse/galaxygen/-/blob/main/run_data.py" rel="noreferrer">https://gitlab.com/godotuniverse/galaxygen/-/blob/main/run_data.py</a></p>
<p>Thanks for any pointers!</p>

<temperature><gaia>
Is there a simple way to get $T_{\mathit{eff}}$ estimates for Gaia EDR3?
user25153
# Is there a simple way to get $T_{\mathit{eff}}$ estimates for Gaia EDR3?

(Asked by: username_0 on 2022-03-16)

For just hobbyist purposes (3D starmap) - I'm trying to infer temperature from EDR3 data to make a rough assessment of stellar type.

I tried applying figure 2 from this doc:
<https://arxiv.org/pdf/1008.0815.pdf>

$ \log(T\_{\mathit{eff}}) = 3.999−0.654(C\_{XP})+0.709(C\_{XP})^2−0.316(C\_{XP})^3 $

Where $C\_{XP} = G\_{BP} - G\_{RP}$ (from Gaia TAP over Astroquery)

However, it seems to only work for G type stars when comparing for known $T\_{\mathit{eff}}$ for the same stars identified in SIMBAD. So with that formula I get 5619 from SIMBAD but 5630 for the G type star.

However, for M stars, with temperature in SIMBAD of 3111, I'm getting values less than 1.

Is there another formula to use for dimmer (and brighter) stars? Or perhaps someone has done preprocessing that is available via TAP somewhere else?

Similarly, I'm curious if there are any groups out there that have identified possible binary/multi-star systems.

<https://gitlab.com/godotuniverse/galaxygen/-/blob/main/run_data.py>

Thanks for any pointers!

**Tags:** temperature, gaia

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## 2 answers

### Answer by username_1 on 2022-04-28. Score: 3

The paper you got your relation from states it is only valid for C\_XP<1.5.
i.e. For K-type stars and hotter. If you extrapolate a non-linear polynomial fit outside its limits of application then don't be surprised if it returns nonsense values.

You can then see (Fig 9) that the conversion from colour to temperature for redder colours and cooler stars becomes highly sensitive to metallicity, so unfortunately there is no one-to-one mapping between Bp-Rp colour and temperature for those stars.

You might have more luck using G-Rp, which should be less sensitive to metallicity.


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### Answer by username_2 on 2024-01-05. Score: 3

The GAIA database includes ***teff\_gspphot*** as an existing parameter. The methods used to calculate temperatures are complex, see for example:

<https://gea.esac.esa.int/archive/documentation/GDR2/Data_analysis/chap_cu8par/sec_cu8par_process/ssec_cu8par_process_priamteff.html>

"*For our temperature estimation, we refrain from using a simplistic polynomial model, which would make too restrictive a-priori assumptions about the mathematical form of the colour-temperature relation. Instead, we use GBP−G and G−GRP as features to estimate Teff using extremely randomised trees (Geurts et al. 2006, hereafter ExtraTrees). This machine-learning algorithm comes up with a non-parametric model for the colour-temperature relation, which is far more general than a model of polynomial class.*"


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