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Robin, congratulations on contributing to the debate! I would be surprised if varying the mass for the explosion in a 2 WD merger scenario did not lead to a variation in luminosity, though maybe the mass range is not significant. I thought there was a lack of good quality measures to any great distance where Type Ia’s are used, but I must admit that I’ve not looked into this in great detail.
Andrew, I think there might be difficulties in getting supernova explosions in core collapse supernova models but not a WD that reaches the Chandrasekha mass limit. I have a recollection of reading somewhere in the past couple of years that modelling revealed that certain stellar mass ranges could lead to explosions while others may collapse to a black hole without creating a supernova.
Cheers,
Andy
I only saw then end of the program so I am not sure if they mentioned this as a possible cause.
The standard theory is that Type Ia supernova are all about the same luminosity as they are caused by the explosion of a white dwarf when it reaches the Chandrasekha mass limit. This holds true if matter is slowly added to the white dwarf so that it goes bang at exactly Chandrasekha mass. Hence a standard mass for the explosion, a standard luminosity, and so you can work out how far away it is.
I’ve heard of the possibility that you could also get a Type Ia supernova by the merger of two white dwarfs. They could have various masses, so the mass and luminosity of a Type Ia would not be a set value. This would cause problems with the determination of the Hubble Constant using this approach. I am not sure if this has now been discounted, or something that is quietly overlooked.
Andy
Hi John,
Finding detailed information about a specific star can be a challenge. The detailed information is often written by professionals, especially when it comes to spectroscopy. Though if it is an ARAS target, then someone on the ARAS forum may know more.
This may be too technical, but you can search for journal articles using ADS (SAO/NASA Astrophysics Data System). The below link is to an ADS search for ‘uv aur’ in the journal abstracts:
https://ui.adsabs.harvard.edu/#search/q=abs%3A%22uv%20aur%22&sort=date%20desc%2C%20bibcode%20desc&p_=0
Scanning through journal articles can sometimes throw up a useful annotated spectrum, a list of spectral lines, or useful information in the abstract without needing to read the whole article.
Cheers,
Andy
Hi Mike,
I agree it would be great to be able to subscribe to notifications of new posts to different forum topic areas. This isn’t possible at present but I have added it to a list of requests maintained by the BAA Website Operations Team. Just to set expectations this may not be possible and if it is then it may be a while before it is implemented.
There is a page that shows the forum posts in order of last comment date, the most recent ones at the top.
https://www.britastro.org/forum/active
So if you’ve not visited the website for a while you can look here to see all the posts since your last visit. You can get to this page by clicking the ‘See more’ link at the bottom of the 4 most recent topics.
Best wishes,
Andy
Hi Andrew,
I am sure this topic is fine and may well interest other BAA members.
I can’t answer your exact question, but I have experience which may be relevant. I am a part-time self funded mature Astronomy PhD student at the University of Exeter. I pay for my PhD course fees and living expenses by working 3 days a week, and doing my study/research 3 days a week. This can make for a busy life but it is rewarding in the non-financial sense!
I did look at funded PhD places but there is lots of competition for them. My employer kindly agreed to let me go part-time so I could spend 2 days a week at university, on the understanding with the university that I would also spend a day of my weekends doing study/research.
Since then I have changed jobs and I now do a variety of jobs, mostly IT. This includes working part-time for the BAA doing a mix of office and IT work, so this isn’t pure astronomy work but it is interesting. To avoid any confusion, I also do some voluntary activities for the BAA, like managing the Photometry and Spectroscopy databases.
I am about to start demonstrating at university, another source of income which may be available to MSc/PhD students at other universities.
I have considered other sources of income which may be relevant to astronomy/physics graduates. There are websites which allow registered people to bid for small scale IT build work in different programming languages. It may be possible to find tutoring work in astronomy, physics or maths. I have also seen planetarium and astronomy educator roles come up at museums, and while these aren’t necessarily part-time it can be worth asking.
Good luck and let us know how you get on,
Andy
Hi Robin,
Unfortunately the sticky posts is not working properly. I just tried removing and adding back the ‘sticky’. At first it was at the top of the Spectroscopy forum with the word sticky next to it, but as soon as another post was added the word ‘sticky’ vanished and it moved down the list.
I have added it to the list of Website Operations Team tasks, though it might need to wait until the next website upgrade to fix it.
Cheers,
Andy
Hi John,
There aren’t any official BAA spectroscopy campaigns, though notifications of requests from researchers are sometimes posted to the BAA forum. See Robin’s recent posts for requested spectra on X Per from Dr Paul Roche.
https://www.britastro.org/node/15515
https://www.britastro.org/node/15540
The VSS also runs an Yahoo alert group where any targets of interest or requests for observations are posted, and this includes requests for spectroscopy.
https://groups.yahoo.com/neo/groups/baavss-alert/info
I think a list of current targets is a great idea, though we’d need a volunteer to maintain a list.
Cheers,
Andy
Hi Lars,
To avoid any possible confusion. Live streaming is only possible where the meeting is at a venue that is able to provide the live streaming for us. Thus far that has only been possible at the Institute of Physics in London, and so this should not be expected for Winchester or other venues.
Whenever possible we try to record meetings (different to live streaming and much easier from a technical point of view) so they may be added to the website for members to watch.
Cheers,
Andy
Another point to bear in mind, for the same aperture you will need a more robust mounting for a long tube telescope than for a short tube telescope. Telescope mountings are often overlooked and I agree with David’s comments. A good mounting makes a huge difference to usability and enjoyment of a telescope.
I am not trying to put you off a refractor, as a good refractor is a joy to use. However, the long distance from the eyepiece to the mount will multiply up any small movements in the mount and tripod.
Andy
Hi Paul,
The telescope type is in the visual observation spreadsheet. This is quite old, dating back to the submission format for the old text file database that was created in the 1990’s when database field size mattered. Today this is not so much of a problem, but I’ve not bothered changing the spreadsheet since it is what the VSS observers are used to.
In the visual spreadsheet there is a comment if you hover your mouse of the ‘Type’ field on the ‘Observer Details’ tab. R is for reflector and G is for refractor (Glass). In fact this does not really matter and you could type ‘refractor’, ‘reflector’, ‘Meade 8’, ‘C11’, etc. The only limit on the visual spreadsheet is the total length of all the instruments must not exceed 255 characters. The database upload process checks this and will tell you if this limit is exceeded.
In the photometry spreadsheet it is the ‘Telescope Short Description’ on the ‘ObsvEqmt’ sheet that matters. This does not actually need to be very short as the description can be up to 255 characters, though if anyone uses this much text I think they are being too descriptive 😉 Examples are:
- RC 0.6m f/8
- Meade 14 LX200R on AP1200
For collaborative efforts, it is best to setup an observer code to cover all the collaborators and a special login.
Cheers,
Andy
I have setup a page for the 2019 meeting in the events area of the website.
If anyone knows of cheap or even free venues we could use then please let me know via the forum or by emailing me. They ideally need to be in easy reach of public transport as otherwise we’ll need to setup a taxi service 😉
I had wondered about somewhere in central Birmingham? There is also the Northamptonshire Natural History Society venue that has been used for BAA meetings in the past. Though I’d struggle to get there before 11am and might have to leave before 5pm.
Andy
Hi Tony,
When creating the response curve in BASS do not tick “Free Draw” or “Linearise”. You should find that neither is needed unless you have a particular problem you need to overcome. The “Free Draw” means you can click anywhere, which is usually a bad thing as it means you can click outside the response curve. Leaving it unticked forces each point you click to sit on the curve. Of course the proof of whether it works is always to see if your standard star spectrum is adjusted to be a good match to the Miles or other reference spectrum.
Where possible, I try to make all the spectra I take fall on roughly the same vertical position on the CCD chip. This is a tip I picked up from Olivier Thizy at one of the workshops. It is not essential, but he recommended it as a technique to get the maximum accuracy from spectra. While, flat fields, rotation, tilt, wavelength calibration should all work to allow you to place the spectrum anywhere on the chip, by placing the spectrum in the same physical location on the chip it means these corrections need to do ‘less work’. That is always a good thing as it means the corrections tweak the result rather than have to be relied on for large corrections. In reality my spectra are never exactly on top of the same chip position, but I try to get within a few pixels.
It might be an idea to send the workflow to John for comment before publishing. With my tutorial I posted it to the BASS Yahoo Group, and I got useful feedback from the user community enabling me to improve the tutorial. My preference would be not to have the “Lamp”, “Standard” and “Target” as 3 separate top level streams. Instead using the top level sections of the tutorial as the top level streams. That way it enforces the same geometric corrections on each image or master image.
Cheers,
Andy
Hi Tony,
I am glad you are finding the tutorial useful. While ISIS is great for bulk reliable processing, BASS is very flexible and relatively easy to use.
Robin gives good advice on the hot pixels. Similarly I would suggest trying to locate the position(s) in one of the raw spectrum images, then compare that to your master dark frame. When creating a hot pixel map in BASS, you should use your master dark frame, that way you do not need to worry about clipping out any of the spectrum. Then you simply apply the same hot pixel map to all images.
If it turns out to be a frame specific problem, probably a cosmic ray hit, then the BASS “Cosmic, Hot & Cold Pixel Removal” tool allows you to select any size of sub-region to work on and set the threshold. If it is on a single image you could zoom in on the problem region, setting a very small rectangle around the hot pixel, and set the threshold to just pick out that pixel. How well this works will depend on whether the pixel(s) stand out above the spectrum intensity. There is also a tool for editing 1D profiles, but this really should be used as a last resort, and I would be tempted to ditch the sub-frame is there is a low intensity cosmic ray hit that is proving troublesome to remove.
That is a useful workflow you have shared. The one bit that jumps out to me is whether you are applying identical rotate, tilt and active binning regions across all your images. The first 2 of these are particularly important, though for best results you also want the same active binning region. When I use BASS I have all the images loaded, so I can apply the same identical corrections to all images in one go, rather than process the calibration, standard star and target star images separately. Noting this easiest performed on the stacked calibration, standard star and target star images rather than all the individual sub-exposures.
Also, just to check you are not really drawing the response/continuum curve freehand. With BASS you select points in the raw response profile that avoid absorption/emission lines, or any other nasty sharp features, so you get a nice smooth curve.
Cheers,
Andy
Thanks for pointing that out Robin, I have now removed it. I suspect it was an accident made by the person who created the meeting.
No problem John. This is just a preference and I have seen some people who do post the same item to more than one forum. Personally I find that harder to follow as then you have to check 2 threads for updates.
It is always a little tricky when a topic can cover more than one forum category.
I tend not to look at the individual forums unless I am looking for a historic post. Instead I look at the lower right hand side of the web pages, where the 4 threads with the most recent activity are shown. To look back further I click on ‘See more’ as this takes you to a full list of forum posts in descending date order. That way I can be sure I don’t miss anything.
Cheers,
Andy
