Questions tagged [spectra]
Questions about the observed frequency range of the electromagnetic radiation of a celestial object.
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Supernova remnant spectral lines
I have some trouble to find which spectral lines are the ones in this SNR N49 fitted spectrum.
They are at 1.3 keV, 1.9keV, 2.5keV, 3.2keV, 3.95keV and maybe at 0.65keV and 6.8keV (approximately).
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Stellar classification spectral lines: chemical abundance vs temperature
I'm an amateur who watched the Cosmos episode on Cecilia Payne's contributions to stellar classification, which I liked. I've been going down a rabbit hole on this and and I have a question for ...
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What causes the Balmer Jump?
To quote Wikipedia:
Balmer Jump is caused by electrons being completely ionized directly from the second energy level of a hydrogen atom (bound-free absorption), which creates a continuum absorption ...
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Which stars are elliptical galaxies constituted by?
I know that elliptical galaxies are old galaxies, with almost no star formation and an old stellar population. This can be seen by their dominantly red spectra in the optical. I am trying to get a ...
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How do amateur astronomers do stellar spectroscopy?
This question consists of 2 parts:
How can amateur astronomers measure the spectrum of stars?
In addition to diffraction gratings, what equipment do they use (like telescopes, and the focal length ...
user47732
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Reduced chi square value
I am currently plotting a continuum of observed data. I need to check the effectiveness of the fitted continuum with the reduced chi-square method. Ideally, should the reduced chi-square value ...
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Provided a relative flux v/s wavelength plot, how can I calculate the radial velocity of an exoplanet? [closed]
I imagine the relativistic version of the Doppler effect would be appropriate but I'm not entirely sure since flux is a measure of intensity. Alternatively, where could I find redshift data for ...
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Natural line width from absorption lines
Emission lines have a certain natural width. Due to the uncertainty principle systems that spontaneously decay or produce radiation have a fundamental energy blur, and their radiation has a ...
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Different types of line broadening in stellar and galactic spectra
When analyzing stellar and galactic spectra with spectrographs, the spectral lines get broadened from the instrument. Why do the spectral lines get broadened after the light moves through the ...
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What objects in the night sky have the narrowest range of visible light
What objects visible to the naked eye at night have the narrowest spectrum of visible light reaching the earth. Put another way, Which objects are most visible as a specific color or colors rather ...
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Have we detected spectra of exotic atoms in stars?
I was reading this wikipedia article on positronium (a type of exotic atom) and noticed it mentioned that positronium has a spectra (of course).
So naturally this makes me wonder, have we looked at ...
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General questions about SDSS
I'm considering doing research on SDSS spectral classification (STAR, GALAXY, QSO) with machine learning for my school dissertation. Not sure if this is an appropriate place for these kinds of ...
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How can I estimate a stars surface temperature, luminosity, radius, and lifetime only knowing it's solar mass and peak wavelength? [duplicate]
For example: if a 10 solar mass star emits light at a peak wavelength of λ = 300nm.
How can I calculate a stars surface temperature, luminosity, radius, and lifetime with this infomation?
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How does instrumental dispersion work?
I am trying to understand the mathematical formulation of instrumental dispersion in galaxy and star spectra. Let $x=ln(\lambda)$. Assuming that the galaxy spectra G(x) is composed of many identical ...
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How to obtain exoplanets transmission spectra from JWST's NIRISS data of WASP96?
I was having a look at JWST's NIRISS data of WASP96 (specifically at the x1dints fits file which should be already calibrated). From this, I would like to obtain a result in a fashion similar to the ...
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How to find the resolution of a spectrum?
I have been tasked to find the spectral resolution of some synthetic spectra (wavelength in Angstroms vs. flux) of different stars and degrade them to the resolution of observed spectra. But I am not ...
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How are plage regions related to the density of medium and velocity FeII ions?
During a literature review (abstract), I found that the intensity of FeII (298.5 nm) ions in the last solar minimum was higher than the two previous solar minima 21 & 22. The velocity of FeII ions ...
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How to fit LOSVD of a galaxy with gauss hermite parametrization
I have recovered the following LOSVD from an elliptical galaxy, that I now want to fit a gauss-hermite-parametrization to and derive the kinematical parameters rotational velocity, velocity dispersion ...
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When measuring the spectrum of an object at the zenith, is it better to orient the spectroscopic slit N-S of E-W?
If you were to measure the spectrum of an object while it's exactly at the zenith, how should you orient the slit of the spectrograph to minimise atmospheric dispersion? Is North-South or East-West ...
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How to convert spectra to log-wavelength and interpolate them into linear spacing in log-wavelength
I want to write a function that cross correlates a spectrum with a quasar template
I’d like to ask you how can I convert my flux density vs wavelength spectrum to log-wavelength. It’s not clear to me ...
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S/N binning of 2D spectral galactic data
I have the 2D spectrum of the ellipical galaxy NGC 4697 taken by a long slit spectrograph. The x-direction (horizontal) corresponds to wavelength and the y-direction (vertical) corresponds to distance ...
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What happened to the reemitted photons during recombination?
To my understanding, the Cosmic Microwave Background Radiation (CMBR) is light released during the recombination epoch where the formation of neutral hydrogen atoms allowed for a sudden drop in the ...
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what is the difference between Composite Stellar Population and Galaxy Spectral Energy Distribution?
I am reading Conroy et al. (2013), an extensive review on Stellar Population Synthesis technique, and I really can't get the difference between Composite Stellar Population and Spectral Energy ...
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How to handle empty tables returned by astroquery Nist.query() in Python?
I'm writing a code to extract wavelengths of certain species of atoms/ions in a given wavelength range using the Nist.query() command of the Python package ...
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How to calculate S/N in galaxy absorption spectra?
I want to calculate the S/N of an galaxy absorption spectrum.
I therefore chose a part of the spectrum which contains very little to none absorption features and should be only made up of noise and ...
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Meaning of "blue continuum spectrum"?
The textbook Astrophysics in a Nutshell, talks about the "blue continuum spectrum" in relation to the spectrum of an AGN:
I know that a continuum spectrum is caused by the interaction of a ...
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How to find x-values of fourier-transformed correlation functions in velocity space?
I am trying to extract the kinematic parameters (rotation velocity, velocity dispersion, ...) of an elliptical galaxy by extracting the kinematical broadening function using the FCQ-Algortihm first ...
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Are there any SuperCam spectra available?
A lot of pictures from the SuperCam, the NavCam or the Mastcam onboard the Perseverance rover are available online (for instance on the NASA and JPL websites). Have any SuperCam spectra been made ...
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How to remove redshift from galaxy spectra in Python?
Hello I extracted a spectrum from the central region of the 2D spectrum of the major axis from NGC 4697 (I just took a central row in the 2D data set, see this question for more information: How to ...
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How far can a star's visual colour deviate from black body radiation?
The primary driver of a star's colour is its temperature, by way of black-body radiation.
Black body radiation restricts stellar colour to a narrow slice of the full RGB spectrum.
However, all stars ...
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starting from SSP spectra to evaluate galaxy spectrum and observed mag
I know that the galaxy spectrum, namely the flux per unit wavelength versus the wavelength, is the sum of the Simple Stellar Population (SSP) spectra at a fixed redshift (e.g. similar to eq. 1 in ...
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Spectra of different stellar classes?
I'm beyond an amateur, but I've been failing to find this information and it makes me think I'm missing something.
Anyway: I am trying to write a procedurally generated simulation that includes ...
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Spectral lines of the Sun?
If I remember correctly, the pp chain and (partially) the CNO cycle are the dominating set of reactions in our Sun. On the other hand, the composition of the Sun has many more elements/isotopes than ...
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How to extract galaxy spectra for different radii in Python for spectra taken by long slit spectrograph?
I am trying to extract the kinematics from the elliptical galaxy NGC 4697 using the Fourier Correlation Quotient (FCQ) algorithm described by Bender (http://adsabs.harvard.edu/full/1990A%26A...229.....
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What type of spectrum does the Wolf-Rayet star WR137 have?
Is it an Emission Spectra or an Absorption Spectra?
I think that it's an absorption spectrum, but then why is the light intensity curve focused on elements that should not be in the star in this case, ...
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Question regards to Kirchhoff’s Laws (of spectroscopy)
In the book "Horizons: exploring the universe-Cengage learning (2018)", page 210, it states that:
Observational evidence can tell you how nova explosions occur. As the explosion begins, ...
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Derive LOSVD from galaxy spectrum, using fourier method
I am trying to implement a programm, that derives the kinematics (specifically the kinematic parameters: mean rotation velocity, velocity, dispersion, hermite coefficients h3 and h4) from an ...
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Why doesn't the Sun produce an emission spectrum?
I have read that the reason why the Sun produces an absorption spectrum is because the temperature drops as you go away from the center, such that as the various layers of the atmosphere of the sun ...
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Astronomical data bases express spectra in flux density, e.g. ergs/s/cm2/Angstrom( or Hz) how can I calculate the flux, i.e. ergs/s/cm2?
I have light spectral data from astronomy data bases in flux density (flux/Angstrom or flux/Hz) and would like to calculate the flux. How can I calculate the flux from the flux density?
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Why is He I 6678.151 line used for investigating variations in Be stars?
Why is He I 6678.151 line used for investigating variations in Be stars? I mean, for instance, asymmetry and radial velocity. Many thanks
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H alpha - double peak (Be star)
What is the double peak in this case, please? What does the third mean? Many thanks
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Cosmic variance - Fourier Transform - a few precisions
I have posted initially on physics exchange but none answer, so I try my chance here (I am going to delete the physics exchange one) :
I cite an original report of a colleague :
If we are interested ...
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Logarithmic rebinning and continuum removal of stellar spectra
I am trying to learn how to derive the line of sight velocity distributions from galaxy spectrum to extract kinematical parameters like rotational velocity and velocity dispersion. Therefore I need to ...
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Flux vs. Velocity representation of spectra?
I'm looking for a basic explanation of the flux vs. velocity representation of a spectrum and how it's obtained from the regular flux vs. wavelength representation. A good example of this is in Arav ...
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How to determine the temperature of a star according to the strength of the line in the spectra?
Based on the comments, I have changed some things.
Below is a graph showing the relative strength of $H_\gamma$ and Fe I lines of two stars. Which star is hotter?
This is a question from the book:An ...
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How would one estimate the rotation period of a star from its spectrum?
The figure is shown; the measurements were taken on two consecutive observing nights. The Ordinate is the flux normalized to continuum and the abscissa is the wavelength scale. You can see the "...
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Finding galaxy spectra in SDSS Catalog by object name
I am looking to find galaxy spectra of early type elliptical galaxies in the SDSS catalog by the objects name. See: https://dr12.sdss.org/advancedSearch. I dont know how to find out the PLATEID of my ...
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Spectra: What is that Supposed to Mean?
I've found this website (click here for the link), the link leads you to a problem about the velocity Andromeda is going towards the Milky way galaxy, and you can try three approaches. I like to ...
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working with stellar spectra in fits format in python
Hey I am new to working with astronomical data in Python. I wanted to start working with stellar spectra and I am having trouble with the data. To get a first look I just wanted to plot a spectra (...
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Is threre a relation between relative or absolute error and standard deviation for ratio of power spectra?
I have to compute the variance on this ratio, that is to say on the observable $O$ :
$$O=\left(\frac{C_{\ell, \mathrm{gal}, \mathrm{sp}}^{\prime}}{C_{\ell, \mathrm{gal}, \mathrm{ph}}^{\prime}}\right)=\...