I have just tried to report a recent observation of khi Cygni and was surprised to get an error message saying that theres is no star with the AUID I used (000-BDC-152). This is strange, since I have used this AUID for all observations reported so far this year without problems. I then looked into VSX and saw that khi Cyg has assigned AUID 000-BCJ-205. There is no information about a recent change in AUID and this leaves me wondering if there may be recent undocumented changes. I cannot help but think that there may have been some recent changes because a week or so ago I noticed that for a couple of days I could not use LCG (both versions) to plot light curves for khi Cyg.
Has anybody noticed this? Are there any changes that have not been documented?
Hi Hernan,
The answer starts with a question: why are you reporting objects using an AUID?
The AUID is an inhouse identifier, and as such, it may suffer from some internal changes that should not have any impact on the observers.
AUIDs shouldn't be used as star names because they aren't.
They are unique identifiers assigned to all stars with observations in the AID (the AAVSO International Database) and all comparison stars in VSD (The Comparison Star Database).
There is more information on AUIDs here.
And you can read:
"As an observer you may never come across an AUID or really need to know what, for example, the AUID of SS Del is (000-BCM-129, for the curious)."
And that is the case.
What happened with khi Cyg?
Even when they were supposed to be unique identifiers, due to different reasons some stars had more than one AUID.
- Another AUID may have been assigned during the transition from Harvard Designations to AUIDs when objects were not correctly cross-identified (old names like "VAR NE" were prone to mistakes).
- Another AUID may have been assigned when VSX was created more than ten years ago without realizing the same object already had an AUID in VSD (some variables have entries in VSD).
- At the early stages of VSX another AUID maye have been assigned for newly discovered variables that were also comparison stars in VSD (we introduced thorough checks years ago, the fact that a comparison star was not variable wasn't as easy to check as it is today with the large amount of survey data available).
Recently we corrected most (965) of these inconsistencies so all our databases have the same AUID for all objects. The VSD AUID was chosen as the priority AUID because that AUID is used to identify comparison stars in our observer's reports. When a variable star had a different AUID in VSD and in VSX, the VSD AUID replaced the VSX AUID. The goal was to get rid of these multiple AUIDs for the same object, because that is what unique identifiers are supposed to be: UNIQUE!
The change took place last thursday and users shouldn't have had any impact excepting the disappearance of all observations for a couple of hours when we were making the changes.
So that is the reason why khi Cyg has a different AUID now: its VSD AUID has replaced its VSX AUID.
We recommend that you do not pay attention to AUIDs when you report variable stars. Use the variable star name to do it.
Cheers,
Sebastian
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Sebastian Otero
VSX Team
American Association of Variable Star Observers
Thanks for your detailed answer, Sebastián.
I was using AUID's because I believed them to be true unique identifiers, and I thus trusted that by using them instead of names I could avoid ambiguities in naming stars. In fact AUID is an acceptable identifier in WebObs. Now I see that things are more complicated than I previously thought.
Cheers
Hernán
PD: Aprovecho para saludarte en castellano, paisano, y felicitarte por tu gran aporte a la ciencia de las estrellas variables!