Gaia DR3 is out.
And almost 12 million variable stars come with it.
This will have a lot of implications in the variable star community.
They all have a type assigned.
Among them, several million variable stars have periods too.
To give you a rough idea on how amazing this is: the number of eclipsing binaries in this Gaia release is larger than the total number of objects in VSX (which is 2117852 right now).
As it happens with the ATLAS catalogue (and others), checking VizieR to see if the object is already known -even when it is not in VSX-, is mandatory.
The ATLAS catalogue has a lot of issues that make it difficult to import as is, but that will happen eventually.
We are assessing the quality of the Gaia DR3 variability catalogue but the fact that positions and identifications are excellent, will give this a high priority in our list of updates.
This means that finding a new variable star from now on will become a really difficult task.
We are already receiving several messages from individual researchers or groups that use to submit their findings to VSX, asking about this issue.
The short answer is that credit will have to be given to Gaia Collaboration.
For the objects without period information that may have a wrong classification, co-discovery credit might be obtained. We want to encourage observers to work on more complete and accurate analysis of individual objects. E.g. data mining different surveys, obtaining better (and standard) ranges and periods, etc.
Gaia DR3 also offers epoch photometry for lots of objects (available through VizieR) so Gaia data can now be used to complement other light curves.
It will take time to add all these objects to VSX, and in the meantime, keep in mind that you will have to check VizieR to see if the star you are analyzing has already been discovered as variable.
If it is in the Gaia list, you will have to provide the following reference:
Gaia collaboration; et al., 2022, Gaia Data Release 3 (Gaia DR3) Part 4 Variability
2022yCat.1358....0G
Even when this sounds "cataclysmic" (!) for people wanting to find new variable stars, I am sure there will still be things to be found. Gaia's cadence is not high and some interesting variables may have escaped detection.
Cheers,
Sebastian
Hi Sebastian.
You write: Gaia DR3 also offers epoch photometry for lots of objects (available through VizieR)
Might you explain the procedure to obtain data ?
Cheers
Franco
Hi Franco,
nothing weird. You just have to look for the Gaia DR3 part 1 catalogue entry in the list of VizieR results (e.g. after a positional search). In the case of variable stars, the fourth result for that catalogue will be the epoch photometry ("Light curves for a given object in bands G, BP and RP (555868797 rows) (epoch_photometry)".
You will have all G, BP and RP observations there.
You can use the VSX external links to go to VizieR instead of starting a new query from their site.
Cheers,
Sebastian
Thank, got it. But let me to do an example: ASASSN-V J060539.61-272641.9, classified in VSX ( and Gaia DR3) as YSO, but in ASAS-SN Var database is classified ROT (without period).
In Gaia DR3 I find this table: I/355/epphotGaia DR3 Part 1. Main source (Gaia Collaboration, 2022), with this footnote: Result truncated to 50 rows on a total of 56 matching rows
So can we only access the first 50 data? And how can we export columns to Excell (export all and then select?) or VStar ?
By the way, this subject seems to me to have a strange combining phase plot (ROT + EA) see: https://imgur.com/6ACiGQN
Cheers
Franco
Hi Franco,
The maximum number of lines displayed is valid for all catalogues and is set by you.
You have a dropdown menu in the left panel, under "preferences". Choose "Unlimited" and you will get all lines.
Just copying and pasting works well if you want to create a spreadsheet with the data, I do that (I have customized spreadsheet for each surveys data).
About your star, it is also in the ATLAS catalogue as ATO J091.4150-27.4449 and classifed as IRR (irregular). Although a period of 10.48 d. is possible according to their different period solutions (This is consistent with your findings)
YSO was the original classification the ASAS-SN Team sent to us, but then a lot of objects classified as such were found to be spurious (based on colours) so the ROT: classification was adopted. The "ROT:" class includes a lot of constant stars too so revising them is always a good project.
The ASAS-SN pre-processed light curve (it is always better to re-compute it and get all the available data, entering something like 4000 in the Number of days to go back field) shows variations between V= 13.35 and 13.83 and a typical light curve for a spotted star: mean magnitude and amplitude changes.
2MASS and WISE colours do not show infreared excess so there is no reason to classify this star as YSO. The Gaia DR3 parallax suggests it is a subgiant.
Your phase plot is telling us that it is eclipsing (then a binary!) so its proper classification is EA/RS.
You found the orbital period. We welcome a revision to VSX, you have to determine an epoch of mideclipse and the eclipse duration.
Then you can find the rotational period (similar but not the ame as the orbital period, that's why you see the changes in the light curve shape at maximum when plotted at the orbital period) and add an additional plot and a remark with the RS elements.
Great that you used SuperWASP data, but just stick to the ASAS-SN name in your plot.
Good analysis ;)
Sebastian
Thanks, I've already done some work, ASASSN data are from Sky-patrol with 3500d back, and I have plotted the rotational period that is slightly different (in fact eclipsis migrate over the rotational curve).
I've looked at SED in VizieR and seems to shows a W4 IR excess, but I'm not an expert...
I stumbled upon this subject via Zoouniverse SuperWASP program, so I have submitted it in talk, if team is not interested in studyng it, I'll submit to VSX revision, butI I think I need to have a clearance from the research team to do this.
Cheers
Franco
Gaia Data Release 3: All-sky classification of 12.4 million variable sources into 25 classes
Submitted on 30 Nov 2022 (v1), last revised 7 Mar 2023 (this version, v2)
Classification results comprise 12.4 million sources (selected from a much larger set of potential variable objects) and include about 9 million variable stars classified into 22 variability types in the Milky Way and nearby galaxies such as the Magellanic Clouds and Andromeda, plus thousands of supernova explosions in distant galaxies, 1 million active galactic nuclei, and almost 2.5 million galaxies... The latter contains 24 variability classes or class groups of periodic and non-periodic variables (pulsating, eclipsing, rotating, eruptive, cataclysmic, stochastic, and microlensing), with amplitudes from a few milli-magnitudes to several magnitudes.