Unanswered Questions
84 questions with no upvoted or accepted answers
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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 ...
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6
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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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6
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1
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Do narrow lines in the spectra of O- and B- type stars always indicate magnetic fields?
I was reading a paper on the differential emission measures of a set of hot O- and B- type stars. As the authors discuss in Section 3 (page 959), two stars, $\tau$ Sco and $\theta^1$ Ori C, have ...
CommunityBot
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5
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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 ...
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4
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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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4
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54
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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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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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4
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What can Jupiter's spectrograph tell us other than its rotational velocity?
I have data of a Jupiter's image and the spectra of each pixel in the image, and I am playing around to see what I can do with it.
I have managed to find Jupiter's rotational velocity by finding the ...
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4
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588
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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 ...
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4
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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 ...
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4
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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 ...
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4
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210
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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\...
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4
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131
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Spectral analysis of AGN (velocity dispersion of galaxy absorption, doppler shifts)
I was wondering what parameters I need to know/measure to calculate the velocity dispersion of a galaxy, specifically an AGN.
Also, I have spectra where there are blueshifted and redshifted ...
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Why MIT's Benjamin Rackham says "nearby ultracool dwarf SPECULOOS-3" would look "purplish-red, spotted, and flaring" from an airless orbiting planet?
May 15, 2024 MIT News article Newly discovered Earth-sized planet may lack an atmosphere includes the following:
“We can say from our spectra and other observations that the star has a temperature of ...
- 30.7k
3
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78
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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 ...
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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 ...
- 30.7k
3
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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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3
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191
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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 ...
- 30.7k
3
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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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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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3
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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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3
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590
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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 ...
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3
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468
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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 ...
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3
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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?
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3
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713
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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 ...
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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 ...
- 17.6k
2
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51
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How to identify Hydrogen lines of slitless spectrograph of Type A9 star
Hi I am analysing slitless spectrograph of type A9 star Canopus. Here is as sample of the spectrograph.
I basically did a simple summing up of the columns and added the data (as a simple spectrum co- ...
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56
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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 ...
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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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2
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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 ...
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