Questions tagged [spectroscopy]

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

42 questions with no upvoted or accepted answers
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What are realistic and unrealistic values for the high energy gamma ray spectral indices of pulsar wind nebulae?

This summer, I was working on a project fitting very high energy gamma ray spectra of the Crab Nebula, a pulsar wind nebula. At energies about $\sim$1 TeV, a simple power law suffices, i.e. $\phi(E)\...
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191 views

Does the current "fainting" of Betelgeuse show any spectral trends that differ from it's normal variability?

update: With all the newest news about including what the Dr. Becky video discusses as linked in How do magnetic fields mess with astronomers' observations? I'll bet this question can now be ...
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101 views

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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150 views

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 ...
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63 views

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 ...
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190 views

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 ...
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64 views

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\...
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184 views

Strong orange line in wood fire spectrum?

I just built a DIY spectroscope using a CD and after making some tests, I noticed a really strong emission line located in the orange-yellowish zone of the fire spectrum (specifically, burning wood). ...
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49 views

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 ...
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67 views

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 ...
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21 views

Estimate upper limits on flux values in the case of a non-detection?

I have ALMA data which are non-detections of some spectral lines in a protoplanetary disk. The data is in the form of spectral cubes. I am hoping to estimate an upper limit on the flux of each of the ...
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33 views

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 ...
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31 views

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 ...
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39 views

Why does X-shooter use double passes through prisms for Echelle cross-dispersion instead of gratings?

The catchy title Down-the-barrel observations of a multiphase quasar outflow at high redshift: VLT/X-shooter spectroscopy of the proximate molecular absorber at z=2.631 towards SDSS J001514+184212 ...
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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)=\...
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33 views

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/...
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19 views

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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31 views

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 ...
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71 views

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 ...
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344 views

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 ...
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99 views

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 ...
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2k views

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?
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423 views

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 ...
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54 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 ...
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28 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 ...
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26 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 ...
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27 views

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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31 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 ...
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35 views

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 ...
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50 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 ...
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35 views

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 "...
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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 ...
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218 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 ...
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87 views

What is an "Off Rowland-circle Telescope"?

The NASA Goddard news item NASA to Demonstrate New Star-Watching Technology with Thousands of Tiny Shutters says: The technology, called the Next-Generation Microshutter Array (NGMSA), will fly for ...
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68 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? ...
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45 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 ...
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34 views

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 ...
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62 views

How do you fit a model SED to an observed galaxy spectrum with photometric data?

I have a spectrum of a galaxy from HST data and SDSS data (resulting in a nearly continuous SED from the FUV~1000 Angstroms through infrared). I have created a model SED with the galaxy simulation ...
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87 views

Why does D4000 affect stellar age?

From my understanding D4000 is a ratio between the 'flux densities between 4050 and 4250 Angstroms and that between 3750 and 3950 Angstrom', from Poggianti et al (1997). However I do not understand ...
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74 views

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 ...
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27 views

Cause of complicated water vapor emission lines in red supergiants?

Why do some water vapor emission lines in red supergiants have a complicated structure with lower peaks to the left and to the right of the peak at the central frequency? It has something to do with ...
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30 views

Where to find all spectroscopic data about 28 CMa?

I am searching all available spectroscopic data (and particularly wavelength interval) of 28 CMa in the constellation Canis Majoris to measure radial velocities. Which database should I use?