Affiliation
American Association of Variable Star Observers (AAVSO)
Wed, 12/05/2012 - 00:05
Hi,
As leader of the YSO group at AAVSO, I am interested in running a campaign to try and find UX Orionis-type stars among the less well-known 'Algol' stars. UX Ori stars (UXORs) are young stars engaged in the formation of planetary systems and which show Algol-like falls due to obscuration by accreting planetesimals in the circumstellar disc. For this reason, certain stars (BO Cep for example) were once classed as Algol-type stars but have later turned out to be UXORs!
Since YSOs are strongly found in low galactic latitudes, the campaign would only search among those stars in, or close to, the plane of the milky way.
Anyone interested?
What's different from the YSO campaign? Are there different targets? Is it just a matter of looking at light curves that are (slowly) accumulating for those stars?
Jim Roe
Hi, Mike,
Very interesting indeed.
In the course of the VSX revisions, I remember having reclassified some from E to UXOR. From the top of my head, KR Mus was one of them, classified as E by Hipparcos.
There are a lot that seem to be in need of a revision. BO Cep is still not classified as UXOR so I'll revise it tomorrow.
If you have a list of known UXORs that could be used to update VSX, it would be helpful.
Cheers,
Sebastian
Buenas tardes Sebastian!
(Sorry, no inverted ! on this keyboard)
I don't have a list to hand at the moment, but I know there aren't that many (yet). The GCVS page is no good, since the variable types there are all ISA, INSA and so on. Personally I was planning to start using some selected stars, having a look for IR excess and then going to ASAS with the likely candidates.
-from memory, some UXORs: BO, IL, SV, YZ Cep, MQ Cas, WW Vul, XX Sct (I think). Also, some stars classified as RCBs may be UXORs as well! I had today's variable on the home page, RZ Vul, as a possible, but in this case I don't think it is. Always good to look at though!
Folks,
Remember that considerable progress has been made on cleaning up RCB classifications. In case you aren't a member (yet!) of the R CrB forum, I call attention to our recent paper:
http://arxiv.org/abs/1211.2475
Cheers,
Doug
The non-Mira and low-galactic latitude non-RCBs in our Table 5 might be worth a scan for UXORs.
Cheers,
Doug
Mike, thanks for bringing those to my attention, I'll check them.
Doug, in fact, Patrick and I checked that list (I think there are still some left to check) and several miras, RV Tauris and UXORs came up from it.
The 4 UXORs candidates are TYC 7672-563-1, TYC 8999-807-1, ASAS J070615-1904.4 and 2MASS J16544896-4032517 and have been revised in VSX.
Cheers,
Sebastian
Hi Sebastian,
Glad to hear it! I am always wildly impressed by how quickly the VSX team makes use of new variable star information!
Cheers,
Doug
Folks,
It would be useful and instructive to compile a set of UXOR lightcurves in a single location. Does such a resource exist?
Cheers,
Doug
Hi, Mike:
You had written: "-from memory, some UXORs: BO, IL, SV, YZ Cep, MQ Cas, WW Vul, XX Sct (I think)"
I checked the literature and the surveys for data on those stars and revised their VSX entries. Only SV Cep and WW Vul were previously catalogued as UXORs.
I could confirm the UXOR nature of BO and IL Cep, MQ Cas and XX Sct but failed to do that for YZ Cep. More obervations needed.
I'll be adding some more on the days to come. So a VSX search by type will reveal the ones already confirmed in VSX.
Cheers,
Sebastian
As I
Cheers Sebastian,
As I said, I was working from memory (in fact I was upbraided by John Greaves for including YZ Cep as an UXOR!) so, no hard feelings! Certainly the variations of YZ Cep make it look like UXOR. The jury is still out on RZ Psc, a most peculiar star, which I didn't mention.
Caveat, I am a newbie to CCD Ph. and to YSO's. Inspired by this group I started a project a year ago aimed at systematic surveying of YSO's. As I can't establish a visual program from my home, I have had to undertake to construct a remote ccd system located at the local astronomy club observatory.
This has been quite a project over a year in progress; building and assembling the physicallyfeacility, then the operating software challenge and observing database. For the last month now the program has been gathering data finally and I am now wading through the process of setting up the reduction system and finally begun posting data. It would seem from images reduced today, that I caught RZ Psc in a plunge. Looks like the first one in some years.
I am interested in your proposal. At the moment I have 160+ stars in my lineup, this based upon what was (or I thought was) available in charts for YSO's visible from my latitude (+35) with a horizon block at 30 degs and minimum magnitudes brighter than 17 or so. Even so I have had to request a lot of updates and some corrections to the charts. It has been my intention to ask for new charts to match your observing list here. But am open to any set of YSO's.
At the moment the system can grab about 160 images a night, some of these being duplicate shots taken on time available basis, the emphasis being on getting at least one image of every star that is up during the night on the list. Ultimately, I intend to include B filter images in these extras shots. It occurs that I might want to change my imaging of suspected UXOR's to include B on the base imaging session. It would be interesting to see how the B-V were to change in a drop vs base period.
Cripes! Sorry that I hadnt replied to this interesting post earlier, forgive me. Actually both B and R are useful when UXORs fade. Brightening in B happens because, as the fade is caused by some kind of obscuration, a fade in longer wavelengths (including visual) sets in, so that most of the radiation we see is that which is scattered from the obscuring dust (the same phenomenon which produces our blue skies!)
Multiwavelength observations are also interesting with other YSOs. The example that stands out is the recent - about 2 years ago - very deep fade of V730 Cep to below mag 16, which I caught myself (visual) but which correlated with an increase in longer wavelengths, suggesting that whatever caused the visual fading was re-radiating from the forming star itself - probably a gas clump or early-stage planetesimal. This episode went on for some time (on a human timescale of course). Although V730 Cep is a T Tau rather than an UXOR the processes causing the variations seem to be similar.
How is excess IR defined? I have seen this several times and have not been able to understand how that is determined. Thanks Bruce
Dust around YSOs produces an infrared excess that can be seen as the star being redder in longer wavelengths.
When you compare the colors in the optical with the infrared colors, you see that the excess is not affecting the optical colors meaningfully so the difference between, e.g. B-V and J-K, is evident.
E.g.:
A normal A6 star will have B-V= 0.16 and J-K= 0.08 (J-K always smaller than B-V) but an A6e UXOR will typically have something like B-V= 0.30 and J-K= 1.50 (J-K always larger than B-V).
That is a useful way to separate UXORs from eclipsing binaries.
Cheers,
Sebastian