Questions tagged [spectroscopy]

Questions about the measurement of light waves whereby the wavelength is classified by its position in the electromagnetic spectrum.

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What are the pros and cons of different types of echelle spectrograph cross-dispersers?

Echelle spectrographs, operating at high resolving power, typically consist of an echelle grating with a low numbers of lines/mm, used with high diffraction orders (often $n=$50-100). To separate the ...
ProfRob's user avatar
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Need help understanding stellar spectroscopy data from ESO

The European Southern Observatory webpage has a web page that has tabular spectrogram data from A. J. Pickles, University of Hawaii. There are over 130 .dat files there. Each one represents a ...
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Why does titanium oxide around Betelgeuse produce this particular sawtooth-shaped absorption spectrum?

Betelgeuse Just Isn’t That Cool: Effective Temperature Alone Cannot Explain the Recent Dimming of Betelgeuse suggests that the recent dimming might be caused by increased optical absorption by dust ...
uhoh's user avatar
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How does SDSS estimate photometric redshift of sources?

I'm looking through the data in SDSS DR 12: ...
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What happens to the non-fusion formed metals in stars?

Let’s consider a population I star of some given metallicity. I know that depending on the type of star, different structures are possible with convection zones and radiative zones trading around ...
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A simple echelle spectrograph for viewing solar spectrum

On the Astrosurf website here, someone has designed a deceptively simple echelle spectrograph for viewing solar spectrum. Briefly, light from an optical fiber falls on an echelle grating and which is ...
AChem's user avatar
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How is the roll of the Hubble telescope around its axis and the dispersive direction(s) of it's spectrometer(s) managed?

Reading Dupree et al. 2020 Spatially Resolved Ultraviolet Spectroscopy of the Great Dimming of Betelgeuse (also in arXiv and summarized in Phys.org's Hubble finds that Betelgeuse's mysterious dimming ...
uhoh's user avatar
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How significant is the effect of galactic rotation on line broadening of carbon monoxide?

In class the other day, we were discussing observations of rotational transitions of carbon monoxide, namely, the $J=1\to0$ and $J=2\to1$ lines. We originally had assumed that both lines would have ...
HDE 226868's user avatar
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How to calculate magnitudes in photometry?

I have a passband filter $b$ and a spectrum (SED) $f_{\lambda}(\lambda)$. Often the formula I find to get the flux in that filter $F_b$ is $$F_{b}=\dfrac{\int f_{\lambda}(\lambda) T_{b}(\lambda)d\...
Catarina Alves's user avatar
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What instruments do amateur astronomers use in their ground based telescopes in order to avoid atmospheric absorption/telluric contamination?

What instruments do amateur astronomers use in their ground based telescopes in order to avoid atmospheric absorption/telluric contamination? For example, when an astronomer observes a celestial body ...
Arjun's user avatar
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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 ...
gangio's user avatar
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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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Is there a tool to convert N-body RAMSES simulation file formats to GADGET 2 format in Python?

I am looking for a way to convert RAMSES files to GADGET-2 binary files because I want to use the package SimSpin (https://github.com/kateharborne/SimSpin/blob/master/R/make_simspin_file.R) which is ...
Jerome's user avatar
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How were "microshutters" or other multiplexed or multi-object techniques first used in Astronomical spectroscopy?

This answer to How will microshutter arrays be used in the James Webb and future space telescopes? explains how multiple objects can be selected so that the throughput of a spectrometer can be ...
uhoh's user avatar
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What is the difference between spectroscopy, spectrography and spectrometry?

Spectroscopy is the study of spectra, spectrography is the writing of the spectra, and spectrometry is the measure of spectra. So from an etymological perspective, there is no real difference between ...
usernumber's user avatar
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How does the ESPRESSO Echelle spectrograph fold the spectrum so nicely?

The CBC News Technology and Science Q&A This ESPRESSO machine doesn't make coffee but scans the skies for habitable planets includes a nice description of ESPRESSO (Echelle SPectrograph for Rocky ...
uhoh's user avatar
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What is meant by ionization states?

I am going through the theory of Saha equation but I am not able to understand the concept of ionisation state? What are ionization states actually?
Rian's user avatar
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How to use spectral profiles to determine luminosity class?

I know the luminosity classes are: Ia-0 ( Hypergiants ), Ia ( bright supergiants ), ... , VII ( white dwarf ). I also have learned that you can use the presence of absorption lines ( ie. use spectral ...
user2738698's user avatar
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H-alpha velocity fields of spirals falling into a cluster

What kind of impact would you expect ram pressure stripping / tidal interactions / harassment / interactions with the cluster potential (etc!) to have on the h-alpha velocity fields of infalling ...
astro person's user avatar
2 votes
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Calculate change in spectral line intensity for a change in temperature

I am trying to do some simple modelling of spectral line emission. I am starting with some ALMA observations of a protoplanetary disk, where the emission from a particular molecule at frequency 344GHz ...
lucas's user avatar
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How can I compute reasonable errors on my Gaussian fits to the observed strong optical lines of interest?

I'm fitting Gaussians to optical lines spanning from H-beta to Sulfur using Astropy's Gaussian (https://docs.astropy.org/en/latest/api/astropy.modeling.functional_models.Gaussian1D.html) model with a ...
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How does one estimate the mass of a galaxy using the Balmer break region?

I am currently reading the recent astrophysical paper "A population of red massive galaxies ~600Myr after the Big Bang'. In the first paragraph/abstract it mentions, "It has been difficult ...
shram's user avatar
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Is there any open data base for raw spectroscopy data?

I'm msc. student in physics and will start my thesis in a month. We are in search of a topic with my thesis professor and we talked about many ideas. After all, "what will this give us ...
Ege Tunç's user avatar
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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 ...
trynerror's user avatar
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Calculate the uncertainty in measured flux density from an integrated intensity map

I have some ALMA data, in the form of a spectral cube, which I have integrated along the velocity axis to create an integrated intensity ('moment 0') map. The integrated intensity map shows emission ...
lucas's user avatar
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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 ...
Robert Mifsud's user avatar
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Would Atlas Pro's prediction about the color of plant in Kepler-186F work as a biosignature to search for life?

The Atlas Pro video that prompted this question is this. Tl;dr: it is argued that due to the different spectrum of radiation emitted by Kepler-186 and what is known about the evolution of ...
Rubén Crespo's user avatar
2 votes
0 answers
17 views

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)=\...
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How to remove radial velocity effects of an exoplanet from the host star spectra?

I have a spectra of an M dwarf and I would like to remove the Doppler shift effects due to a known exoplanet, with known planetary parameters, from the whole spectra of the star. I have shifted/...
Mukul Kumar's user avatar
2 votes
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61 views

What happens to the Fourier Transform of the Measured Spectrum?

What happens when you double the width of the entrance slit of a spectrograph, in turn letting in twice as much light, would there be an improvement in the Fourier transform of the measured spectral ...
Jay D's user avatar
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Line Flux Ratios in Active galaxies

Good day to everyone. I wanted to know what is the importance of estimation of line flux ratios in active galaxies? What does it help in characterizing? As in Lyman $\alpha /$Carbon IV, or Mg II$/$...
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Correction to inverse square law for cosmology

While reading about the discovery of quasars and the spectroscopic analysis of 3C 273 in this paper by Maarten Schmidt, I came across the following quote: At these distances, corrections to ...
Jim421616's user avatar
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2 votes
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Source for Identification of Balmer Hydrogen Absorption Lines

I'm working on an assignment, where I have to classify stars using the raw data of the telescope. I'm now trying to calibrate the pixel to armstrong ratio, and for that I need to identify the ...
condosz's user avatar
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Can all astronomical signals be considered Gaussian noise?

While studying the techniques astronomers use to mitigate radio frequency interference (RFI) I found it's often assumed that astronomical signals are (band-limited) Gaussian noise. Is this a ...
Fachicon's user avatar
1 vote
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23 views

Obtaining Transit Spectrum for Celestial Bodies Using JWST NIRSPEC

I've recently been tasked with obtaining transit spectrum data for some fascinating celestial bodies, including Ceres, Enceladus, Ganymede, Io, and Titan. The goal is to compare their transit spectra ...
starry_explorer's user avatar
1 vote
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19 views

Using Gaia Passbands with L_nu coordinates

I am trying to find the coordinates of my bundles of gas on the gaia ($G, G_{bp}-G_{rp}$) hr diagram. I have its spectrum in $\nu L_\nu$ coordinates. Thus far, my attempts have mainly been to ...
Berkin's user avatar
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1 vote
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Space telescope spectroscopic data for stellar classification using Wien's law

My goal is to make a simple project which consists of classifying stars by applying Wien's displacement law. I need public spectroscopic data about different stars from a space telescope, so that I ...
periwwinkle's user avatar
1 vote
0 answers
54 views

How do nuJ(nu) units work?

I'm working with (Nublado) Cloudy, which is essentially a spectral modelling tool for stellar matter. Using the software, I model my own stellar object and obtain its continuum. According to Hazy, ...
Berkin's user avatar
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1 vote
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Determining the rotation curve of a galaxy via given spectroscopic data

Here is the data analysis question from IOAA-2011, 1. Weighing a galaxy: The image 8.2 shows a photograph of the spiral galaxy NGC 7083, which lies at a distance of 40 Mpc, and image 8.3 a fragment of ...
samuraiwarrior's user avatar
1 vote
0 answers
61 views

Could we optically observe metallic hydrogen in space?

As many calculations have been done on whether metallic hydrogen is metastable or not in low-pressure environment, It occurred to me that by the fact that we have not observed any metallic hydrogen so ...
C-Consciousness's user avatar
1 vote
0 answers
205 views

Relationships between G magnitude, Johnson V magnitude, and spectral type of stars?

I'm simulating a population of binary stars for a summer research project. I'm adding uncertainties to my simulated observables such as angular position and radial (line of sight) velocity. I'm using ...
Sofia Splawska's user avatar
1 vote
0 answers
60 views

Error of bisector method

How to determine the error of bisector velocity span? I have found the article below, but I do not know what all quantities mean. What is the number of lines in the mask? How to find out x? How to ...
Elena Greg's user avatar
1 vote
0 answers
99 views

H alpha - double peak (Be star)

What is the double peak in this case, please? What does the third mean? Many thanks
Elena Greg's user avatar
1 vote
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36 views

Any examples of a gas object temperature from Doppler broadening along one axis turning out to be wrong because velocity spread was not isotropic?

Discussions under Mass of the stellar cluster (not the whole galaxy) lead me to mention that when an actual temperature is inferred from a Doppler-broadened line profile (rather than just a linewidth ...
uhoh's user avatar
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1 vote
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Astrophysical particle spectroscopy; narrow-line particle sources (charged or uncharged) for things other than photons? Have any been detected?

Is Cosmic Ray Astronomy a thing? Is there an equivalent of the red shift effect for cosmic rays? have got me thinking and under this answer I've commented: That's a good point; there aren't as many ...
uhoh's user avatar
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1 vote
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Are falling evaporating bodies (FEBs) and exocomets the same thing? How does one know they're falling and evaporating?

Looking for a (short) list of comets with heliocentric escape velocity I stumbled upon Wikipedia's exocoments which like exoplanets, are bound to other stars. I should have been looking for "...
uhoh's user avatar
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1 vote
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410 views

How to calculate Equivalent Width of a spectrum with continuum at 0

I am trying to calculate the Equivalent Width of emission lines of a spectrum whose continuum is at 0, making the calculation of the EW impossible. I have the spectrum of a transient in a galaxy, so ...
Polemarco's user avatar
1 vote
0 answers
75 views

Does Nickel show up in spectra of Nova?

Does a nova, not a supernova, get hot enough that nickel is produced despite its formation by fusion being an endothermic reaction? If nickel is made, does it make it out of the star into the nebula? ...
Wayfaring Stranger's user avatar
1 vote
0 answers
80 views

Relation between oscillator strengths $\log{gf}$ and the Einstein $A$-coefficient, rotational quantum number,

I'm analyzing the spectra of M dwarfs. Some authors characterize the lines with the oscillator strengths $\log{gf}$ while others follow different paths with the Einstein $A$-coefficient. I would like ...
T. Silva's user avatar
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1 vote
0 answers
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what/how do we mean/derive statistical equilibrium equation of certain energy levels?

While reading the research paper "Excitation of the Fe XIII Spectrum in the Solar Corona" by D.R. Flower and G. Pineau des Forets in the summary I found the concept of statistical equilibrium equation ...
Amartya Mondal's user avatar