The SNEWS project (SuperNova Early Warning System) has teamed up with the AAVSO to launch this huge campaign and we need your help. If you are a bright star enthusiast, this project is for you!
The goal is to obtain long-term photometry of massive stars that might become supernovae in the forseeable future. Having a record of the star's behavior previous to the explosion is very important in order to understand how supernovae work. Of course, the chances of any of these objects exploding as SN during our lifetimes are very low, but... who knows?
INTRODUCTION
Supernovae are the ultimate variable stars. In distant galaxies, a previously indistinguishable star that ends its life in a supernova explosion may outshine its host galaxy in a spectacular blaze of glory. A visible supernova in our own galaxy is an exciting and ultimately historic event. Kepler’s supernova of 1604 subtly changed the course of scientific and Western cultural history. The nearby supernova SN1987A yielded a treasure trove of scientific information, still being studied after 30 years. The immense public interest in a possible Galactic supernova was seen during the great dimming of Betelgeuse (2019) in which AAVSO observations were of critical importance.
Supernovae are both tools and “laboratories” for modern astronomy and astrophysics. Type Ia supernovae are a standard candle for measuring the distances to far away galaxies and of astrophysical interest themselves. A core-collapse supernova (CCSN; Type II and others) is an important process by which heavy elements are created and scattered through the interstellar medium from which other stars and planets may form. They also create neutron stars and black holes. The scientific study of supernovae is hindered by the inability to precisely predict when a star will explode. Important information may only be found by studying the earliest moments of the light curve.
Nearby CCSN are of special scientific interest. However, they are very rare, perhaps occurring two to three times per century, often invisible to the naked eye. Therefore, the world’s scientific community is preparing for the next once-in-a-lifetime event.
Although the time of a supernova event cannot be predicted, an early alert system is operational that gives an alert of a CCSN in our galaxy or a nearby dwarf galaxy minutes to hours before for visible light reaches earth. The SuperNova Early Warning System (SNEWS) is a collaboration of particle physics experiments that detect the burst of neutrinos produced by the core-collapse process. These neutrinos leave the star at almost the moment of core collapse while other electromagnetic radiation escapes the dying star minutes to hours later, depending on the astrophysical details.
The SNEWS alert has been made available to prepare the astronomy community (professional and amateur) and the public for the imminent light from the SN. To sign up for the alert, find the sign up form on the website.
Recently, SNEWS and teams from the AAVSO collaboration have begun work together on several projects to prepare for the next galactic supernova. One project is to obtain long-term photometry on stars in the Milky Way that are candidates for core-collapse supernovae. These measurements could be of great scientific interest. While it is not likely that the light curves could predict an impending SN, after the fact the light curves of the star that actually explodes would yield unique and important scientific information.
THE TARGET LIST
al The initial list is made up of 192 bright supernova candidates and is available through a Google spreadsheet, which also contains a lot of useful information about the objects and the charts that may be used to observe them. It will be updated periodically if other targets of interest are selected.
The spreadsheet has links to AAVSO charts or special charts (see below) so you don't have to make them yourselves. Please see the Charts and Comparison Stars section below for more information.
The objects in the campaign are searchable using the VSX extended search options (click on the "More" button twice). There is a drop down menu in the "Campaign or Program" field and you will be able to select "SNEWS Campaign" and get a list of all the objects, or a subset if you narrow your search using the different parameters available.
The AAVSOnet and SNEWS
The AAVSOnet team is trying something new to support members who want to use the AAVSOnet telescopes to observe stars in the SNEWS target list. Instead of having to submit a proposal yourself the AAVSOnet is prepared to observe the whole list of candidate stars and have members subscribe to receive the images. We will use the google sheet where a member can put their obscode in the "AAVSOnet Requestor" column on the line of the target of choice. Then they can sit back and wait for a "You've got data" email telling you that your images have arrived.
How it is going to work:
- Users make entry into the Google spreadsheet
- Put your obscode in the column "AAVSOnet Requestor" on the line of the target star.
- If someone is there before you, add your obscode after theirs: If they decide to drop out and remove their obscode, you will be the next in line to receive the images.
- Note that some of the lines are greyed out and will not except an obscode. There will be a note why this star will not be observed.
- If you want the images delivered to your VPhot account, put "yes" in the VPhot column. Note that all AAVSOnet images are also delivered to a ftp directory under your obscode.
- Every couple days the entries from the google sheet's "Requestor" column will be transferred to the "Subscriber" column.
- After that the images coming through will be delivered to those in the "Subscriber" column.
- If there are already images arrived, unclaimed, these will be made available to you.
The images will be coming from one BSM telescope in the Northern Hemisphere and one from the South and use VI filters. Cadence will be nominally 10 days, though images may arrive more frequently as the system settles down.
Responsibilities
- As an AAVSOnet participant you are commiting to:
- check the images as they come in. Request exposure length changes and recentering as you see they are needed.
- Process the transformed photometry and submit to the AID. Since they are AAVSOnet scopes, there are transformation coefficients available on VPhot.
- Note that some fov's will include more than one SNEWS target. The Public spreadsheet will indicate which fields have multiple stars.
Do the photometry of them all!
- These images have included in their FITS header the entry PROJNAME=AAVSO_SNEWS_HQ_AUTO. This needs to be included in the notes when you submit your data to the AID. VPhot will do this for you automatically
- You are should manage your workload: add more stars if you have the time and they are available, or take your obscode off the list if you are swamped.
- Not all the targets will be suitable for the AAVSOnet BSM telescopes. You will need to sort that out with the help AAVSOnet staff or communicate issues on the AAVSO Community Slack workspace: there will be a channel "AAVSOnet_SNEWS"
API interface
There is a programming interface - an API - for requesting information from VSX about the SNEWS candidate stars. If you are writing code to support your work, you will want to take advantage of this. This will be especially helpful when the Alert comes out and you need to know where to look!
An example of the URL of the call is:
https://www.aavso.org/vsx/index.php?view=api.list&ra=14.09&dec=62.2&radius=3.0&campaign=SNEWS+campaign&format=json
In this case it will get you the SNEWS stars within 3 degrees of the center of Cassiopeia.
The pieces of the API are:
The prefix of the call: https://www.aavso.org/vsx/index.php?view=api.list&campaign=SNEWS+campaign
Then you specify what part of the sky you want to look at. (Note that all fields are in degrees.)
This can either be a circular FOV: &ra=14.09&dec=62.2&radius=3.0
Or you specify a box: &fromra=11.09&tora=17.09&fromdec=59.2&todec=65.2
Or if you don't specify a region, you get them all!
The result will come back in xml. If you prefer JSON, you add: &format=json
If you would like to know how many observations exist in the AID for these stars, add: &data=0
AAVSO Target Tool
The AAVSO Target Tool lets you filter the list of stars to those of your interest (e.g. SNEWS candidates) and it shows you which stars are in need of observation.
Here is how to use it:
- Go to the Target Tool and log in.
- Make sure your profile has the location of your observatory so the Target Tool can show you a list of star targets that you can actually see. Make sure you click "Show only targets that are visible tonight".
- The SNEWS targets are in the High Energy Targets group, so select that group and filter on it.
- Now go to the Notes column on the right and put in "SNEWS" and hit enter. Now you have the candidate stars all in a list.
- To sort the list by how long ago it was last observed, click on the "Last Observed" column heading until the arrow head points down.
- This list can be printed.
TIPS FOR OBSERVERS
There are targets of different amplitudes in the list. When selecting targets, we ask observers to pay special attention to the amplitude in order to maximize the use of their time and effort.
Visual observations are encouraged for those targets with the largest amplitudes (>0.3 mag.). The recommended observing cadence is weekly/twice a week (not more frequently, please).
This doesn't mean that the small-amplitude objects can't be observed visually because - as supernova candidates - these objects are supergiants and are unpredictable to some degree, but such observations should be spaced in time (not more than once a week) to avoid adding personal biases to the light curves. If a star is found to be displaying unexpected behavior (e.g. brightness inconsistent with the catalogued values), then more frequent observations are welcomed.
CCD/DSLR observations of stars with less than 0.1 mag. variation should be the priority for observers with electronic detectors. Observers are encouraged to use a V filter, but multicolor data are of course useful. Recommended observing cadence is one set of exposures (one per filter) weekly/twice a week. Getting light curves of all targets is more important than denser coverage of a single target. If increased activity is found in a target, please observe it more often, and as in many filters as possible.
Beware of saturation issues (!) because all these targets are *VERY BRIGHT*.
PEP observations are encouraged for all of these targets, as they are ideal for PEP. The filter and cadence recommendations are the same as for CCD/DSLR.
CHARTS and COMPARISON STARS
Pre-made charts for all targets are linked to in the Google spreadsheet. They are made with the recommended parameters, listed for your convenience, but nothing prevents you from plotting a different chart if it is more comfortable for you. The recommended fields of view include all the comparison stars that the Sequence Team selected for each target. Cells colored in green refer to binocular charts while orange cells indicate that those charts are "normal" ones. The binocular chart option is helpful to prevent charts from being cluttered with lots of comparison star labels that are not relevant to the campaign targets.
Naked eye targets
Some special charts have been made available for these objects and they are meant for visual observers. The charts included in the 10 Star Tutorials prepared for the Citizen Sky project are useful for some, while Otero charts are available for others*.
One object, alf Sco (Antares) does not have a chart, so observers already observing alf Sco may keep using the same comparison stars that have been using in the past . In the Remark column of the spreadhseet, you can find some recommended comparison stars in case you need them.
Electronic observers may want to select different comparison stars, closer to the variables and more suitable to their needs, and they can use the AAVSO Variable Star Plotter (VSP) to find them. If you can't find a suitable comparison star for your purposes in the current charts, please submit a CHET report to the Sequence Team.
If you need data in different bands, remember to create your own chart checking the different passband boxes.
*Note: Keep in mind that the header information in those charts may not be accurate since it is not based on the updated information that VSP takes directly from VSX!
SPECTROSCOPY
Spectroscopic observations might be requested in the future for interesting targets.
WHAT TO DO WITH YOUR OBSERVATIONS
If you submit your observations of SNEWS targets, to the AAVSO International Database (AID), they will be permanently available to researchers now and in the future free of charge.
You don't have to be an AAVSO member to submit your observations - everyone is welcome! You do have to have two things: an AAVSO web account (free), and an AAVSO Observer Code.
To create an AAVSO web account:
- go to the AAVSO homepage: https://www.aavso.org
- click Login (at the top of the homepage)
- click the Create New Account tab
- fill out the form (please give your real name in the First Name and Last Name (surname) fields)
To request an AAVSO Observer Code (please don't request one until you have observations to submit):
- log in to your AAVSO account (see above for instructions on creating one if you don't have one)
- click the "My Account" link at the top of the webpage
- click the Profile tab
- click "Request Observer Code"
- An email will be sent to you with your observer code. This code is a unique combination of letters and will never be assigned to anyone else.
When you have observations of SNEWS targets to submit, use the AAVSO's utility WebObs. On the WebObs page are links to information about the format of your observations, and options for uploading individual observations or a file.
DISCUSSION FORUM - TALK WITH EACH OTHER!
There is a SNEWS discussion forum on the AAVSO website: https://www.aavso.org/snews-campaign-forum
Please subscribe to it so you may receive emails of posts made there and be able to make posts yourself. You need to have a (free) AAVSO web account to be able to subscribe/post. If you don't have one, it takes just a few minutes to create (see above). You do not need an AAVSO Observer Code to participate in the forum.
LOOKING FOR MORE?
The first galactic supernova will be quite an event and people will be scrambling to observe as soon as possible. As such there are practice runs known as "fire drills" for this once-in-a-lifetime event. If you want to participate more actively you can sign up to receive more information and be a part of these fire drills here.
We'll be looking forward to your observations!