I recently began a small project targeting some M-class variables near V426 Oph, a possible Z Cam I am following. My thought was to pick miras that have no published period in VSX and follow them through to establish periods. A second side project was to see if there are any other variables in the FOV (40x30’). It occurred to me that this might be a good group project. Not everyone can take weekly data, but if the group is large enough we could get the data coverage we need. There are lots of miras with no periods. Many of these are not suitable for amateur work (at least with my set-up) because they have faint companions or field stars immediately adjacent to them, but some are well isolated and could be followed for a couple of seasons. Several of my targets are in the 11-16th magnitude range, so they are measurable. And, who know what else might show up as undiscovered or under-characterized?
Opinions about such a project are welcome: (1) Worthwhile? (2) Would the results be publishable? If yes to 1 and 2: Any professional help available to mentor a group of self-selected participants and keep us in line?
Thanks for any input,
Ed
Hi Ed -
I've done a DSLR nova search for a number of years and have a big archive of images. Mira stars are the bane of the search, dipping in and out of the limiting magnitude and requiring untold hours of searching to establish identities (I don't have an automated pipeline). I would say that most that I track down don't have any observations at all in the AAVSO database (southern skies) and I've often thought that given unlimited free time it might be a good exercise to populate the database. The data would be poor in photometric terms but useful for periodicity, changes etc. But then I think, well, if you wanted info on these stars you could simply go to places like ASAS, (& APASS?) and pull up a light curve!
So I don't really know what the answer is! Good luck with the project anyway.
Cheers -
Rob Kaufman, KBJ
Thanks Rob: In fact a check of ASAS eliminated one of the possible targets (see my other post). Very good advice!
Ed
Hi Ed,
Count me in. I'm always on the lookout for a group project. I have been following Bulletin stars through their minima since Bulleitn 73. I normally oberver these stars every 7-10 days. I would welcome adding this project to monitor other Miras in-between times. And yes, I think it is a worthwhile project for the simple reason to establish their periods. Publishable? Yes, for the same reason, and, as you say, we may find some other interesting things worth publishing.
Michael
Excellent, Michael. We are now a team of 2, hopefully we can get others. I have three targets in Oph picked out that seem promising.
V0877 Oph, V0834 Oph, V874 Oph
I had also picked V0422 Oph, but ASAS beat me to that one.
Please feel free to suggest others or to question these.
Ed
I personally like "2-fers". As long as the Miras are secondary targets, with their photometry acquired while imaging your ZCam stars, measuring their brightness is a win-win situation. That is why my normal practice is to extract photometry for every star in every image (and we've done that with all of the AAVSOnet images since it is my software that is used to process them). CCD cameras have a great multiplexing advantage, so why not make use of that feature? So I support a project like Ed describes.
If instead you consider starting up such a project with the Miras as your primary targets, then you should think about what you are trying to achieve. Measuring the light curve of another Mira, especially if you are only going to do it for a few years at best, does not have great scientific value, unless there is something unusual about that particular Mira. If the goal is to provide periods, that is still a ~5yr project as you need a minimum of 3 cycles, and preferably 5 cycles, before you can get a good handle on the period (and remember, Miras sorta repeat, which is why multiple cycles are really helpful). You may have some other goal, or just think the star is in a pretty field - those are all valid reasons for embarking on such studies.
There are two GCVS-related projects that I've often thought might be useful. There are hundreds (if not thousands) of variables with uncertain IDs, uncertain periods, uncertain classification. It would be nice to clean up the catalog. There are also hundreds of stars with remarks like "this has a unique light curve". Those stars might warrant careful study, especially if they have been ignored by the professionals.
In all cases, do your research before starting on such projects. Check the available photometry in databases like CRTS, ASAS, SuperWASP, NSVS, etc. Look at the reference papers and see if a good study has already been done on the selected stars. Pick those where you can contribute something new.
Arne
Arne:
I think my project was not well thought out. Yes, I did screen ASAS, but not NSVS. Sure enough, my initial NSVS search turned up all of the targets as analyzed in Williams et al. (2004). The periods are not well established.
So prehaps the appropriate question is: Would it be worth correlating the "0" period records in the AAVSO database with various surveys and porting the periods obtained through these various surveys into the AAVSO database to reflect the fact that some have periods but no AAVSO obsevations?
Ed
NSVS on its own will fail to give periods for most miras (excepting the short period ones) because it only lasted 1 year (1999-2000). So most of the periods published in the NSVS lists are plain wrong.
In those cases you will find miras which do have periods but it would be better if they didn't have them...
Combining the data spanning 1 year with data from ASAS-3 if available (several years = several cycles), APASS, CRTS (if not saturated, so only for faint miras) or other source will give us more cycles and we will be able to find a period.
One warning though: NSVS magnitudes are unflitered (R1 in VSX which stands for ROTSE-I) and they will be ~2.5 mag. brighter for the typical miras. Amplitudes will be more or less 50% smaller than V and due to the NSVS resolution the results will probably include nearby stars (closer than 55" or so) which will shrink the amplitude even more.
So combining data is not a straightforward thing but fitting maxima will be enough most of the time if we have a complete light curve to derive a meaningful period.
Those results can be reported to VSX, don't mix the "AAVSO database"concept which refers to the AID where we submit observations, with the "VSX database" where we bring the information on each variable and we can add the newly determined elements based on survey (or our own) data.
Cheers,
Sebastian
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Sebastian Otero
VSX Team
American Association of Variable Star Observers
Thanks for you excellent advice in both messages, Sebastian. Now that you and Arne have guided me to the major resources let me think about what I might be able to do in the way of a project. My first newbie attempt was premature, I shall strive to do better.
Ed
That is an interesting project, but as Rob and Arne mentioned, there are public databases containing data on a lot of the stars that currently have no period published. So a period can *already* be found right now. That is a good data-mining project.
On the other hand, VSX is being constantly updated and correcting wrong IDs and determining elements for GCVS stars with no information is part of this process.
216 GCVS identifications were corrected in VSX only by myself and groups like the Dauban Survey have been reporting several more of these cases. Patrick has been importing lots of updates to GCVS stars over the years that also meant some IDs corrected.
So the first advice is always checking VSX for the last up-to-date data on your variable.
If the star has no period published, look for photometric data on surveys. You have the LInk-outs section in VSX that will take you to all the relevant data.
If your aim is to find periods, focus on the stars with no survey coverage so the visual observations will have more value.
E.g.: the other day I revised some of the stars being discussed here because sequences had been requestd for them. I didn't know they were going to be part of this project, but ASAS-3 data were available for some so, for instance, V0877 Oph (http://www.aavso.org/vsx/index.php?view=detail.top&oid=21363) and V0879 Oph (http://www.aavso.org/vsx/index.php?view=detail.top&oid=21365) now do have a period.
This might be the case for several stars. So check that.
You might submit a revision to VSX in these cases using ASAS-3 data. Or CRTS or NSVS (combining them if there are data in more than one survey if that improves the solution).
This kind of revisions are always welcomed to VSX and then you'll end up with a clean sample of stars that do need observations.
Cheers,
Sebastian
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Sebastian Otero
VSX Team
American Association of Variable Star Observers
Hi Ed, Arne, Sebastian, all
One thing that may be of use here being able to combine various observation sources (AID, ASAS, NSVS, CSS, SuperWASP etc) using VStar's "additive load" capability.
Let me know if you want to know more or if I can help. I wouldn't mind making a modest contribution to a project like this as well (time permitting), even if only to use it to improve the plug-ins or add new ones, but alo of course because it's interesting and worthwhile. With the other things I'm doing, small, point contributions to such a project make the most sense for me right now.
David
Hi Ed,
Your proposed project does sound interesting and I am sure it has the potential to produce some interesting results. As noted by Arne, this is ideal for second tier stars and should not really distract from the usual program stars.
As also mentioned by Arne, for Mira stars it would be desirable to obtain observations of consecutive maxima over a number of cycles for a better determination of the true period and character of the star and allow Sebastian to fill in a few more gaps in the VSX data. And who knows what interesting or unusual stars this may uncover.
During the mid 1990s, I commenced a similar unofficial program to monitor a number of little studied southern Mira and red stars for which there was no period or epoch for maximum brightness then listed in the GCVS. Over the following decade this produced usable results for NSV4189 = V371 Hya, NSV1710 = EO Eri, NSV5087 = V600 Car, DI Car, IY Car, SW Hor, X Mus, V407 Sco, NSV19431 and YY Cen. Those results were initially published through the old VSS RASNZ Publications and more recently the JAAVSO.
In most cases the observations spanned between 10 and 20 years so some patience and persistence is required, especially in cases where the star’s cycle brought it to maximum brightness coincident with solar conjunction.
Introduction of the ASAS3 and what seemed to be the impending doom of visual observation killed my inspiration for this project (something I now regret) and there are still a number of similar stars for which I have sufficient data to be of some use. Perhaps this will inspire me to resurrect that draft material.
Also bear in mind that the catalogue and VSX data obtained from surveys such as ASAS3 are not always accurate, as is the case for a few stars from my unpublished list (more inspiration?). Your proposed program could confirm or improve the currently accepted catalogue detail on little studied stars and who knows what else may come to light so why not!
Peter Williams WPX
Heathcote NSW