(06-09-2020, 12:54 AM)TheManWhoSoldTheWorld Wrote:We need a livestream of @Jiggly_333 going in-depth on this thesis statement with Miles Davis and tea. Would pay good mons to see it.

(06-08-2020, 11:11 PM)Jiggly_333 Wrote:By "narrow lines of hydrogen emission", do you mean that the graph has a tight cluster into a line or do mean a steady, but small amount of emissions?

NVM: I looked up what a Balmer Line was.

(06-08-2020, 11:11 PM)Jiggly_333 Wrote:EDIT, again: Actually, I don't get how you'd classify Balmer Lines. Like, who decides the strength of the line shown from emissions from Star A vs emissions from Star B? It sounds really subjective because I guess you'd need to compare it to something in order to get the point across about how these emissions look different from other emissions. It should be read as "the Type IIn SNe shows narrow lines of hydrogen compared to..." Or do you mean that the Type IIn SNe is the only supernovae of the Type II class to continue to emit hydrogen while the others do their own things?

Another EDIT: I'm not blaming you, the guy you cited probably didn't explain it that well either.

(06-08-2020, 11:11 PM)Jiggly_333 Wrote:Tried to check your source, but got hit by a paywall because scholarly article publishers are bullshit.

(06-10-2020, 11:34 AM)infinitempg Wrote:Ah hah, okay. So the narrow lines mean that the actual width of the emission lines are narrow. The actual measured wavelength of the photons is shifted slightly by the velocity of the object emitting it (so if it's moving away from us, it's redder, and if it's moving towards us it's bluer). The faster it's going, the more shifted the wavelength becomes. Since these things are emitting homogeneously (every direction equally) it ends up with a bell curve shape - only the objects traveling directly away or towards us will have the strongest shift.

The narrow lines themselves come from the circumstellar medium surrounding the star, which is moving relatively slow (on the order of hundreds of km/s), and so all the photons scattered through the CSM do not get shifted that much. It has nothing to do with the intensity!

The intermediate width lines that I reference a lot come from the supernova interacting with said CSM - this moves faster (on the order of thousands of km/s) and so the wavelength shifts are larger - so we see that represented in the widths of those emission lines being larger as well.

You can see this in this image specifically:


The orange dashed line is representative of the narrower emission, while the blue is intermediate width. Because the width is directly related to how much Doppler shift there is, we can use the width of the emission to determine how fast those objects are expanding.



Ok there's a bit to unpack here. Balmer lines are simply the emission lines generated when an electron in a Hydrogen atom drops from a higher energy level down to the second energy level. These have very specific wavelengths because the energy gap between those levels is also very specific. H-Alpha (3 → 2) is at 6563 Angstroms, H-Beta (4 → 2) is at 4861 Angstroms, etc.

The strength of the lines comes from the intensity of the emission, or how bright it shows up. So, going back to the image of SN 2010jl that I posted above, the narrow line emission is significantly more intense than the intermediate line emission, as it peaks much higher in the y-axis of the graph.

Classification of SNe does, to an extent, become subjective. But that's simply because different SN display different patterns in their spectra and in their light curves (their brightness versus time). So, for example, the difference between a II-P and a II-L comes down to the fact that II-P stay luminous for much longer (and "plateau", hence -P). IIn's are special because they're the only SN that show the narrow line H-Alpha emission - no other SNe displays this. (Again, this is due to the CSM interaction generating narrow lines, as described above.)

Now, the difference between Type II and Type I is the presence of Hydrogen emission. Type I do not have any hydrogen emission (presumably because the progenitors to those explosions already rid themselves of their H) while Type II do.

I think this confusion is basically due to the fact that I very barely overviewed supernovae as a topic since my audience is much more likely to understand these things So that's partially my fault. Although, at the same time, I'm not sure how deeply I'd want to go into explaining SNe for this paper since that would take up even more pages.

(06-10-2020, 11:34 AM)infinitempg Wrote:Time to introduce you to the arXiv and the Astrophysics Data System! Just about every astrophysics paper ever written can be found on these sources, and everything on the arXiv is free to read for anyone, anywhere. ADS tends to give a link to both the publisher and the arXiv versions as well. There are always a few papers that require annoying money to read, but most of astro-ph is publicly accessible through these two websites

(06-10-2020, 11:34 AM)infinitempg Wrote:Also, I know today is #ShutDownSTEM day and I shouldn't really be doing this today, but I'm unemployed now so screw it. It's still important to talk about and understand the systemic racism inherent to the STEM community, and I would recommend scrolling through the #BlackInTheIvory hashtag on Twitter - it's very eye-opening and reminds us that the STEM field and community can be and still is very discriminatory towards black people and other minorities. A look at http://aawip.com/aawip-members/]the African American Women in Physics members list is pretty shocking in itself as there are only EIGHTEEN PhDs on the list. In the world. There's a lot of work that needs to be done to make STEM more accessible and welcoming from the ground up, and it's important that the community is aware of this and actively pursues methods to make things better.

(06-10-2020, 12:07 PM)Jiggly_333 Wrote:I'm very happy that the only important academic paper isn't behind a paywall. Unfortunately it's apparently impossible to link to, but here's the corresponding reddit post.

(06-10-2020, 12:41 PM)HalfEatenOnionBagel Wrote:I can't believe this exists