Questions tagged [spectra]

Questions about the observed frequency range of the electromagnetic radiation of a celestial object.

Filter by
Sorted by
Tagged with
2
votes
0answers
27 views

How to algorithmically distinguish between different types of nebulae?

I remember that there are five types of nebulae: Planetary nebulae have not much to do with planets, but are emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red ...
0
votes
1answer
316 views

How to shift an AGN X-ray spectrum to rest frame

I have limited information to shift a spectrum (in the X-ray 0.5-10 keV bandpass) from redshift $z=2$ to the rest frame. I have a plot of normalized (photon) counts s$^{−1}$ keV$^{−1}$ as a function ...
1
vote
0answers
39 views

What is the gravitational wave spectrum of an ellipsoid neutron star like?

If the star is ellipsoid instead a sphere, the wave should be rich of harmonics, not only (2*orbital frequency). Can these harmonics behave the same way, i.e. they appear/disappear together and drift (...
5
votes
1answer
353 views

Why is the flux density and amplitude different for galaxies than stars?

This might be a simple question, but I'm having a hard time answering it myself - or at least answer it correctly, I think. I'm sitting with different spectrals; many for stars and one for a galaxy. ...
3
votes
1answer
636 views

How to correct observed flux densities for redshift

Say I have a spectrum of a galaxy at a redshift $z$, in flux density units of erg/s/cm^2/Angstrom. I'd like to recover the spectrum (in the same flux density units) at z=0, i.e. at its rest ...
0
votes
1answer
19 views

Where to find spectra from Las Campanas Redshift Survey?

I am interested in the optical spectrum of a galaxy. In SIMBAD the reference for the redshift of my galaxy is the Las Campanas Redshift Survey. Hence I am looking for the optical spectrum from which ...
3
votes
1answer
35 views

What does the “a” at the end of a spectral type mean?

Looking at the chart for spectral type peculiarities (here), I noticed that the letter a was missing from the chart. This seems to be an error, as the star Vega has spectral type A0Va, with the a ...
0
votes
0answers
24 views

Where can I find galaxy spectra (in the form of FITS files)?

I know there's SDSS and I tried searching for the spectra through the navigate and explore tool under CAS as well as by using RA/Dec coordinates under SAS, but every single time it comes out with 0 ...
1
vote
1answer
162 views

What (actually) does “peculiar periodic spectral modulations” refer to in this preprint?

I saw this ArXiv preprint after reading about it in the popular media. I can not even understand the beginning of the introduction (much less the whole paper): INTRODUCTION A Fourier transform ...
3
votes
2answers
170 views

Broadband spectrum of Sun

Broadband spectrum is one which is inclusive of all the observed wavelength ranges. In the case of the BB spectra of our Sun, there is a sharp (non-differentiable) kink in the curve in the UV-range (...
9
votes
1answer
868 views

Why does the Sun deviate from a typical blackbody spectrum in the S band?

This is sort of a follow-up to this question, and my answer to it. The graph I see here details the radio (and other frequencies) emission of the sun. What's most notable and interesting to me is the ...
1
vote
0answers
29 views

How to convert between spectra given in terms of velocity (km/s) to wavelength spectra?

I have H alpha spectra of H II regions in our galaxy. In the paper, the x-axis is in units of km/s and the corresponding line width as well. From this, how can I get equivalent width of the H alpha ...
17
votes
2answers
881 views

Problem regarding the absorption lines of the sun

Some of the wavelengths of light that are emitted from the sun will be absorbed by atoms in the outer layer of the sun and also the atmosphere of the sun, and we see this as absorption lines in the ...
3
votes
0answers
41 views

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 ...
1
vote
1answer
68 views

How to isolate H$_\alpha$ from Nitrogen doublet emission lines

I am trying to find out line intensity and FWHM of H$_\alpha$6565 emission line from a quasar spectrum obtained from SDSS DR-14Q. Visual inspection of spectrum shows H$_\alpha$ being contaminated with ...
2
votes
1answer
77 views

How is spectroscopy used to deduce what an object is made of?

Spectroscopy is an analysis of light (or other EM wavelengths) that is often used by scientists to examine what an object is made from or contains. Apologies if this is a stupid question, but this ...
1
vote
0answers
16 views

How do you create a continuum mask in Python or IDL for a star? [closed]

I'm learning how to model stellar spectra using the IDL code, Spectroscopy Made Easy (SME), and its Python counterpart, PySME. Has anyone used these programs before? As you can see from the first ...
0
votes
0answers
34 views

Converting from $\mathrm{W \: m^{-2}}$ to $\mathrm{Jy \: km \: s^{-1}}$

Suppose I observe a spectral line with rest frequency $\nu_0$ and integrated flux density $F = 10^{-26} \mathrm{W/m^2}$. Is the following line of reasoning correct? $1 \: \mathrm{Jy} = 10^{-26} \: \...
3
votes
2answers
145 views

How does a cross dispersed spectrum look like in a reality (from echelle spectrographs)?

I am an analytical chemist with some interest in amateur spectroscopy. Since astronomers use echelle spectrographs to study the high resolution spectrum of the stars, someone suggested to post the ...
1
vote
0answers
43 views

Is there any synthetic spectrum software for neutron star?

Is there any software that can calculate the emergent spectrum of a neutron star photosphere, for Teff is about 1e7K, density is above 1e21-1e22 cm^-3 ? Output line wavelength is about 0-100A is ...
3
votes
1answer
171 views

How long do hot X-ray sources last?

Some X-ray sources in nebulae are caused by hot materials in the millions of degrees that formed in supernovae. What's the cooling rate of this stuff? How long does it stay this hot? If we would take ...
1
vote
2answers
71 views

Is there a way to know if there are/are not solar-system-like systems of objects without a star?

There's an extremely high amount of variation in All of Known Existence. We do see many many stars, with an extensive amount of evidence for planets orbiting around stars. However, is there are way to ...
1
vote
1answer
56 views

How to calculate the redshift of a line in a bunch of line spectra?

If in a spectra, there are many lines, mixed with gravitational redshift and non-redshift lines. For example, in this paper, they identify lines both redshifted and no-redshifted. Then how can i ...
1
vote
1answer
61 views

What does “the depth of the 13.0 Å feature differs by 7 sigma from zero” mean?

In a paper I've read, I have seen the following: In view of the noise levels, it is difficult to perform such a search effectively using statistical significance criteria only. We will therefore ...
2
votes
1answer
51 views

Does anyone have spectra on exoplanet HD 219134b? How could one know either way?

I have foraged through the internet to no avail. Is there a way to systematically check if spectra from a given exoplanet has been reported, like a catalog or list of references, or is a literature ...
1
vote
1answer
58 views

How to calculate the statistically significant level for a guassian line profile?

In some papers, they fit a line profile with gaussian model. For example, in this paper, fig 1 draw three gauss line profile, O VII, O VIII, and Ne IX. But the data seems noisy and the gaussian height ...
1
vote
1answer
76 views

How to use spectral flux density data while using Planck's law giving spectral radiance?

I'm currently working on a fun project in my free time where I'm trying to calculate the temperature, among other things, of stars based on their spectra. Since I have essentially no prior experience ...
4
votes
1answer
223 views

Identifying common galaxy spectral lines

How does one identify the common galaxy absorption lines (e.g. Na, Mg, K, etc.) and emission lines (H-alpha, O III, S II, etc.) by just looking at a galaxy spectrum (like the one below)? I need to ...
2
votes
1answer
45 views

Radial velocity curves

When I measure RV in a program for more spectral lines, will it be equivalent? I mean I measure RVs of a line in blue spectral region, RVs of a line in red spectral region... Many thanks.
5
votes
1answer
65 views

What is the physical interpretation of the derivative of the emitted and observed wavelength?

The flux F of an event at redshift $z$ is related to its luminosity L as $$F=\dfrac{L}{4\pi d_L^2}\,,$$ where $d_L\equiv d_L(z)$ is the luminosity distance between us (the observer) and the event (...
2
votes
0answers
78 views

What is the spectral energy distribution (SED)?

I see the SED being referred to as several different things and now I am confused about what it actually is and what are its units. In particular, I find the SED Wikipedia page not understandable. ...
1
vote
0answers
34 views

Absorption line in quasar spectrum

I have quasar spectrum which includes emission and absorption lines. I need to find absorption lines in between 2 wavelength. How can I do it with coding?
3
votes
1answer
66 views

Nebula and its colors

A Nebula has bright awesome colors that include red, blue, green, orange, white, etc? They're result of excitation of electrons. Is there a clear explanation as to which color is attributed to an ...
6
votes
1answer
210 views

How does the black hole at the center of M87 look like in the visible spectrum?

I learned here that the picture of the black hole we saw all over the news was a false color image, based on the radio spectrum emissions. How would the black hole at the center of M87 look like when ...
1
vote
0answers
147 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 ...
8
votes
2answers
731 views

How exactly will DESI simultaneously capture individual spectra from 5,000 galaxies using optical fibers?

The BBC News article Telescope tracks 35 million galaxies in Dark Energy hunt says: The aim of the five-year programme is to shed light on Dark Energy - the mysterious force thought to drive an ...
2
votes
2answers
48 views

What does the opacity of a molecular transition mean?

In particular, what does it mean when a line (e.g, emission line in stellar wind) is optically thick or thin. I know what an optically think/thick medium is, but how does this concept compare to ...
4
votes
1answer
48 views

How to model and subtract nebular emission lines from stellar spectrum

I have optical stellar spectra from a star forming region with spatially varying nebular background. I want to subtract the nebular lines from the stellar spectra (which are varying in intensity from ...
1
vote
0answers
35 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 ...
2
votes
1answer
53 views

Where can I find a good solar irradiance chart for the infrared?

I'm trying to understand the results of the ExoMars Trace Gas Orbiter vs the Mars Express in terms of their abilities to find methane on the surface of Mars. The solution that I'm coming to is that it ...
2
votes
1answer
54 views

Examples of absorption lines for main sequence stars

Where might I find a detailed table or figure containing the absorption lines and their corresponding wavelengths for each type of main sequence star? I'm trying to get the chemical abundance of ...
6
votes
1answer
421 views

Where can I find a database of galactic spectra?

I was wondering where spectra of galaxies at various redshifts are to be found. I'm looking for ones that can be used to find the recessional velocity of the galaxy and eventually the Hubble Constant. ...
2
votes
2answers
188 views

Using emission lines to determine redshift of a quasar

I am attempting this past paper question and am not sure how to tackle this, this is not homework! :) The spectrum of a distant quasar shows two broad emission lines with observed wavelengths of ...
11
votes
1answer
896 views

Recording Spectral Lines at Home

I was wondering if it would be possible to record the emission/absorption spectra of stars without expensive spectroscopy equipment. Would it be possible to somehow utilize diffraction grating? I own ...
3
votes
0answers
155 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). ...
2
votes
1answer
75 views

What is “g-98” in plots of stellar spectra?

I was looking to find some example carbon star spectra and came across this page on the Harvard website which shows several plots of carbon star spectra. The horizontal axis is labelled as wavelength ...
2
votes
1answer
795 views

How to differentiate elements that have same spectral lines in a star?

Suppose that iron and calcium have a spectral line with the same wavelength. How would you determine which element is present in the atmosphere of a star if you found this line in its spectrum?
1
vote
0answers
22 views

Polarization of an emission line

Say I have a flux density spectrum of a galaxy, as well as polarization spectra for the object in U, Q, and P. I want to find the polarization of some emission line in the spectrum. First, I can fit a ...
3
votes
3answers
143 views

Is there a far away probe that has recorded the light spectrum from Earth as if it were an exoplanet?

We analyze the light spectrum of stars and distant planets to know characteristics like: chemical composition, temperature, mass, etc. Starting from the same principle, a probe at the border of the ...
0
votes
0answers
128 views

Smoothing an SED with binning

I have an (observed) SED of a galaxy, and am attempting to match model SEDs to it. To do this I need to be able to see its shape better, which would involve some sort of smoothing of the spectrum. I ...