9
votes
Integration of Plank curve of the Sun
There are two issues here: one of definitions and one of code.
First, the value you're expecting to get here -- 1361 Watts per square meter, the solar constant -- is the total flux received from the ...
- 37.3k
8
votes
Accepted
Integration of Plank curve of the Sun
There is two issues:
a) you have to use Earth distance to get the Solar constant, but you use 1pc ($10^{16}$m)instead of one astronomical unit (150 million kilometers, $1.5\cdot 10^{11}$m). That's a ...
- 20.5k
5
votes
Accepted
How is the difference of bolometric magnitudes not dependent on the stars' radii?
The R in that equation is the distance from the star to observer, not the star radius. The light emitted from the star is distributed uniformly on a sphere of radius R, and when the light arrives to ...
- 188
4
votes
Accepted
Flux density from brightness map
This expression is valid for low frequencies, including the case of the 1420 MHz hydrogen line. It arises from treating the source as a black body with temperature $T(\theta,\phi)$$^{\dagger}$, and ...
- 37.3k
4
votes
What do the negative values in FITS images mean?
Raw data from detectors is usually some sort of integer type, giving the number of "counts" detected during an integration period. So the values could be [0,65535] for 16-bit data, or [0,...
- 1,632
3
votes
Integration of Plank curve of the Sun
The integral of the Planck function over all wavelengths gives the surface flux at the photosphere of the Sun divided by pi.
In order to get the solar constant, you should multiply this by $\pi \times ...
- 158k
3
votes
Is the flux density independent of source-observer distance?
For the sake of clarity, I want to note that flux density and radiance are two different parameters. Radiance is the power per (projected) unit area per unit solid angle, and spectral radiance is the ...
- 37.3k
3
votes
Accepted
How do you carry errors for brightness magnitudes
You need to do what is called “propagation of uncertainties”. You can search to get more information on that, but briefly if you have some function $f(x)$ that depends on variable $x$, then the ...
- 4,914
2
votes
Accepted
How much does the equivalent width of a line change by the introduction of 5% scattered light?
Imagine your line as a rectangle of width $w$ and depth $d$ relative to a normalised continuum.
Without scattered light, the area blocked off by the line is $wd$ and if the continuum level is ...
- 158k
2
votes
Accepted
Using SDSS data / finding a catalog
From what I can see, you already found what you were looking for. The table you linked is the description of the data available in the Catalog Archive Server (CAS) database. All you have to do now is ...
- 131
2
votes
Accepted
How to access the raw time-series dataset of GOES X-Ray Flux?
You can use SunPy, check the Retrieving and analyzing GOES X-Ray Sensor (XRS) data example. There it explains how to download data with a time range and if wanted selecting the GOES satellite number.
...
- 393
2
votes
Accepted
Is there a way to convert a list of stellar fluxes to a star type?
There is no direct conversion from a flux to a spectral type, but the ratio of fluxes, or the equivalently, the difference in magnitudes in different bands (e.g. $B-V$, $J-K$ etc.), known as a colour ...
- 158k
2
votes
Accepted
Help converting Jansky/beam to erg s^-1
The luminosity of an object in general is
$$L=4\pi\cdot d^2\cdot F$$
where $d$ is the distance and $F$ the observed flux (power per unit area).
Now Jansky is a frequency specific flux defined as
$$1 ...
- 3,617
2
votes
How to convert Flux Density to Flux?
The unit of Jansky (Jy) is a flux density, measured in 10^-26 W/m^2/Hz , which is a frequency specific quantity. In order to get the flux, you have to integrate the flux density over frequency ...
- 3,617
2
votes
What do the flux letters mean? (U, B, V, R, I, G, J, H, K, u, g, r, i, z)
In the documentation of Simbad, it is written:
The magnitudes in Simbad are not always given in a single system. For instance, the "K" band includes K K' and Ks. For more details check the ...
- 31
2
votes
What do the flux letters mean? (U, B, V, R, I, G, J, H, K, u, g, r, i, z)
Each letter represents a filter that passes certain wavelengths of light and blocks others. The flux of the light that passes the filter is measured and that can be converted to a magnitude.
Some ...
- 127k
1
vote
I need clarity on the units in this flux equation
The equation is dimensionally incorrect, or at least the two "fluxes", represented by $F$ cannot have the same units.
Equivalent width is in units of wavelength, thus the units of $F_{\rm ...
- 158k
1
vote
How to get the flux from a synthetic spectrum in a bandpass, when only given specific luminosity times frequency?
You should not be dividing by wavelength in your first step. The values in each given wavelength interval have already the dimension of luminosity ($erg/s$), so you just have to divide these by $4\pi ...
- 3,617
1
vote
Accepted
Calculating the luminosity of a comet
I believe, givn the paucity of information in the question, that what is meant is that if the comet is only visible by virtue of light it reflects, then what is its luminosity.
This can be calculated ...
- 158k
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