I'm quite new in the variable star business, though I've been an amateur astronomer for over three decades. I've been visually estimating variables for about a year now. Last night, February 14th, 20.40 UT, I was trying to estimate the brightness of AA Aurigae with a 12" dobsonian at 90x and 169x, when I noticed something was off. Star 122 on the chart (X26200BCF) was as bright, or even a hair brighter, than 114! It was much brighter than stars 125 and 127. AA Aur itself was a little fainter than 114, but 122 was brighter than it, which obviously doesn't make sense.
So, obviously something is wrong here, if I'm not mistaken. A quick look at Digitized Sky Survey seems to show that 122 is indeed fainter than 114 at that time.
It's overcast here tonight and will likely be for the whole week, so I can't take another look until it clears again.
1) For the moment, I have suspended the 122 label and it will no longer show as a comp star.
2) It is listed in the VSX as GSC 02953-01495 and the type is CST... which suggests that it was possibly noted as variable in some past survey but the fact is that it has remained a constant and there are several thousands of observations in the AAVSO data base that show it to have been constant...
HOWEVER, it is quite possible that you may be the first observer to have noted and OB/variability and you should report your observation and continue to observe.
Thanks for reporting this and congrats on the observation.
Tim Crawford, Sequence Team
ps- I now need to try and find something to fill the comp gap between 114 and 125
CloudyNights member KMAO has found an old AAVSO chart, that shows the star as suspected variable, so someone in the past must have noticed something unusual about it.
Post #6. Chart # 063444a(e)
If you select to show all variable stars as a VSP option (as shown below) it will show this star as a variable on any chart you select... it has been this way since the star was first placed within the VSX data base as GSC 02953-01495... you might also explore CST designated variable types as well as use the VSX to look up this particular star: https://www.aavso.org/vsx/
What Other Variable Stars Should Be Marked?
None GCVS All
All part of the learning process
But if it was in…
But if it was in the database as a variable all along (which I don't doubt), then why was it used as a comparison star????
the star is in VSX because it was once suspected to be variable. It is not in the database as "variable". It is classified as CST which stands for "constant". We do not delete formerly suspected variables from VSX because of historical reasons and because we may have data in the AAVSO International Database (like in this case).
VSP should probably not plot (or at least have an option to hide) objects that are classified as non-variable (VSX has 4 flags: V= variable; N= non-variable; S= suspected variable and Not checked). This might be a feature to incorporate in a future release.
For now, everything in VSX will show up in VSP if you check the "show all variables" option.
this star has been marked as a suspected variable several decades ago based on visual observations but there was never a confirmation for such variability.
Years of observations from the NSVS, APASS and ASAS-SN databases show no variability, with the star remaining constant around V= 12.22. AAVSO data in the AID shows the same thing.
The most recent observation from ASAS-SN was made at 2021-02-12.3058 and shows nothing unusual.
The star is a solar- type G1 dwarf and according to Gaia EDR3 it has a companion 0.5" apart (what we see is the combined magnitude of two 13th mag. stars).
About reporting your observation to The Astronomer's Telegram, I do not recommend to do so. The brightening should be confirmed, a visual observation is not enough to reclassify it or issue such a publication.
This forum post is a good way to alert the community so they can take a look and confirm your sighting or not.
CCD/DSLR observations would be required. If no filters are used, observations that show the star at minimum should also be secured in the upcoming days to be sure the zero points are okay.
When the next ASAS-SN observation is online we will also be able to compare it with other data.
There are several comparison stars that were marked as variable on charts in the past when there were no photometric surveys to check and most of them have eventually been reclassified as constant.
So let's see if someone else can obtain photometry that supports variability.
Hi Tim and Sebastian
Thanks for your help. I'm currently working with a friend to get a remote scope on it. Hopefully it's still in eruption.