Limb Darkening Coefficients Calculation: Understanding Bandpass Selection

  • Context: Undergrad 
  • Thread starter Thread starter natski
  • Start date Start date
Click For Summary

Discussion Overview

The discussion revolves around the calculation of limb darkening coefficients, specifically focusing on the selection of bandpass wavelengths and their corresponding values. Participants explore various bandpass systems and seek clarification on their definitions and applications in astrophysics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Natski seeks confirmation on the interpretation of 'bandpass' as a range of wavelengths for limb darkening coefficient calculations.
  • Natski requests a catalogue or index for the wavelength values corresponding to bandpass names like Hipparcos, Tycho B, and V bands.
  • Some participants provide background on the Hipparcos and Tycho lists, noting their significance in astrometric data.
  • One participant mentions the Stromgren and Johnson bandpass systems but struggles to find specific wavelength values.
  • A reference to a review article on standard photometric systems is suggested as a resource for understanding bandpasses.
  • A participant shares approximate wavelength ranges for near-infrared bands R, I, J, H, and K but expresses uncertainty about the exactness of these values.
  • Discussion includes a mention of a more recent set of limb-darkening coefficients from Claret (2000) as a potential resource.
  • Participants discuss the context of their inquiries, with one mentioning a modeling project and the need to adapt existing code.
  • There is a reference to an "Against The Mainstream" conjecture, indicating a potentially controversial or unconventional theory being discussed.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding bandpass definitions and their applications, with no consensus reached on the specific wavelength values or the implications of the discussed theories.

Contextual Notes

Some participants indicate uncertainty about the exact wavelength ranges for certain bandpasses and the reliability of the sources they reference. The discussion includes references to historical models and conjectures that may not be widely accepted.

Who May Find This Useful

This discussion may be useful for individuals interested in astrophysics, particularly those working with photometric systems, limb darkening coefficients, or related modeling projects.

natski
Messages
262
Reaction score
2
Hi everyone,

I found some useful code to predict limb darkening coefficients on http://www.fiu.edu/~vanhamme/limdark.htm. I understand all of the inputs to this program except the selection of 'bandpass'.

I am assuming that anyone bandpass refers to a range fo wavelengths for which the calculation of the limb darkening coefficients will be valid. Can someone please just first confirm that this interpretation is correct?

Secondly, the author uses names such as Hipparcos, Tycho B and V bands which don't really mean anything to me, so I need some kind of catalogue or index which gives the corresponding wavelength values in S.I. for each bandpass name. If anyone knows what these names refer to or a good online catalogue or something, please please post it!

Thanks in advance,
Natski
 
Astronomy news on Phys.org
natski said:
Hi everyone,

I found some useful code to predict limb darkening coefficients on http://www.fiu.edu/~vanhamme/limdark.htm. I understand all of the inputs to this program except the selection of 'bandpass'.

I am assuming that anyone bandpass refers to a range fo wavelengths for which the calculation of the limb darkening coefficients will be valid. Can someone please just first confirm that this interpretation is correct?

Secondly, the author uses names such as Hipparcos, Tycho B and V bands which don't really mean anything to me, so I need some kind of catalogue or index which gives the corresponding wavelength values in S.I. for each bandpass name. If anyone knows what these names refer to or a good online catalogue or something, please please post it!

Thanks in advance,
Natski


Hipparcos was a satellite launched in 1989 that returned parallax and astrometric data on roughly 120,000 objects with high precision. The list of objects are known as the Hipparcos list. Another list of less precise measurements, known as the Tycho list contains about a million objects. I've only seen Tycho 1 and Tycho 2 used to describe this data... perhaps the Tycho B list is the Tycho 2? The V band refers to the bandpass of wavelengths measured, in this case it means the green-yellow (visible) portion of the spectrum.

Color index
the catalog
 
Two fo the most commonly quoted bandpass systems seem to be Stromgren uvby Johnson UBV. I cannot find any actual values for the wavelength passes though despite a couple of hours of heavy Googlage... any ideas??
 
I found http://www.aavso.org/pipermail/aavso-photometry/2003-December/000111.html which explains the Stromgren system... just need to find Johnson UBV now...
 
Last edited by a moderator:
try this. especially reference #1.

A review article for you.

STANDARD PHOTOMETRIC SYSTEMS
Michael S. Bessell
Annual Review of Astronomy and Astrophysics, September 2005, Vol. 43, Pages 293-336
(doi: 10.1146/annurev.astro.41.082801.100251)
 
Last edited:
Yup, thank-you very much chemisttree
 
Does anyone know what wavelengths the near-infrared bands R, I, J, H & K correspond to?
 
Hi Natski,

R: 500-776nm
I: 648-746nm
J: 1007-1433nm
H: 1323-1937nm
K: 1800-2580nm

More or less; I just pulled this out of a fortran code I have, but the exactness of the bounds seems circumspect to me. If you can get a copy of Allen's Astrophysical Quantities, I bet that'll have the wavelength range for these bandpasses.

As an aside, a more recent set of limb-darkening coefficients can be found in Claret (2000) (http://adsabs.harvard.edu/abs/2000A&A...363.1081C), if you're interested.

Can I ask, having seen all your posts, what exactly it is that you're doing?
 
Good question, FTL. It's an ATM trojan horse.
 
  • #10
I can't really go into too much detail because this is the world wide web afterall. I'm doing some modelling and just needed to correct some code I got provided with many unfamiliar aspects to it. I was basically trying to change the code from quadratic to Claret-style limb darkening.
 
  • #11
Chronos said:
Good question, FTL. It's an ATM trojan horse.

ATM?
 
  • #12
An "Against The Mainstream" conjecture. This model was refuted about a century ago.
 
  • #13
OK, I'll bite... What theory are you referring to?
 

Similar threads

Undergrad Some questions about Cosmic Microwave Background radiation
  • · Replies 13 ·
Replies
13
Views
7K