My first post in AAVSO forums.
I've been doing a binocular astronomy project to observe 100 double stars in Cygnus. Last night, while observing ARG 39, I noticed a third star not far from the primary which was not shown by Sky Safari. This happens occasionally due to data anomalies in Sky Safari catalogs. A 13th magnitude star was shown in the correct location, and I figured it was a data issue. But when I cross-checked SIMBAD today, I found that the Sky Safari data matches the SIMBAD listing for the star, and the corresponding DSS image. The star is UCAC4 697-080601, which is listed as having a visual magnitude of 13.63, but last night was something like 8.5-8.6. It is not shown as a variable star in the SIMBAD data I looked over, but possibly there are further listing with additional details? I observed it at 9:33 CDT on Sunday, September 24, 2023 with a 20x80 binocular on a p-gram mount.
I wasn't sure who to reach out to with this observation. I did send an email to the AAVSO Info address about it earlier today.
Thanks in advance for any help with finding out more about this star, or with reaching an appropriate contact.
Fiske Miles
Hello Fiske,
We got your email, but since you shared your experience in the forum, I will reply here.
First of all, you are looking at the wrong database for variable star variability.
The main source of information on variable stars is the AAVSO's Variable Star Index (VSX).
Go to the VSX search page and preferrably do a positional search (you need to click on the "More" button to get coordinate-based search options):
https://www.aavso.org/vsx/index.php?view=search.top
Since not all variable star catalogs may be in VSX (nowadays new lists are published very often), you should always check VizieR.
You don't need to go to an external site to perform that search, just scroll down to the External links dropdown menu in the VSX results page (after your positional search) and you will find a link to the VizieR results around the specified position.
In the case of UCAC4 697-080601, it turned out to be a Gaia DR3 variable, so I took the chance to add it to VSX.
It is an F-type star, likely a DSCT or GDOR variable. The amplitude is only 0.02 mag. and its mean V is 13.66, consistent with the value you took from SIMBAD, which comes from the UCAC4 catalog which, in turn, takes it from APASS.
https://www.aavso.org/vsx/index.php?view=detail.top&oid=2388159
It is a dwarf, and it is nearly impossible that an F-type dwarf has a 5 mag. flare, that is something only red dwarfs do.
Unfortunately, if there is no image that we can check, we can't help much. My guess is that this is an identification issue.
If you saw a 8.5 mag. star at that position, then what you saw was as bright as the components of the ARG 39 double you were observing, since its components have mag. V= 8.34 and V= 8.91.
What is the limiting magnitude with your binoculars?
Were you able to solve the AB components (separated by 15")?
I would come back to the field to look for the same patterns.
Maybe the field of view was different. Maybe it is a scale problem.
There are ASAS-SN observations the previous night:
2023-09-24.3525628 13.786 g 0.019
2023-09-24.3538200 13.808 g 0.019
2023-09-24.3550690 13.828 g 0.020
The star was normal.
Your observation was at 2023-09-25.106 (always use UT times, not local times).
I would recommend that you come back to the field and make sure you are looking at the right stars.
Please report your new results here!
Best wishes,
Sebastian
Hi, Sebastian.
Thank you so much for this guidance. I will review the data catalogs you suggest and will re-observe the star tonight.
Here are my observation notes for ARG 39 from Sunday evening. I was observing with an APM 20x80 ED MS binocular on a FarSight parallelogram mount from my urban driveway. Limiting magnitude for the instrument in that context would be something like 10.5 magnitude or maybe a little fainter. Thirteenth magnitude stars are well below what could be seen with it. About the best I can do from my yard is around 12th magnitude, and that is with a 127mm binocular telescope at higher magnification.
Here is an observing report from Sunday evening posted on Cloudy Nights, with an image of me with the APM 20x80 binocular. ;-) I was wrapping up a project to observe 100 double stars in Cygnus with 20x binoculars. Over the past few years I have logged hundreds of hours observing doubles with binoculars of various sizes from my yard and have become adept at star field navigation, to the point where I occasionally notice display errors in Sky Safari resulting from bad data points. Which is what I initially thought was the case with the ARG 39 observation. That SS simply had the wrong magnitude for what turned out to be the G component of the ARG 39 multiple star. But the SIMBAD data correlated with Sky Safari.
I will follow up after re-observing and consulting the appropriate variable star catalogs.
Thank you again for taking the time to review my observation and provide helpful suggestions.
Fiske Miles
explorethenightsky.com
I am puzzled by your detailed description because it seems to leave no room for speculation, but at the same time there is no easy explanation for what you saw.
It would have been great to keep observing at the moment the event took place to see if it was something fast, if the star remained bright for several minutes/hours, if its brightness varied, if it moved (= maybe a geostationary satellite), etc.
If you can still see something there, draw what you see.
There is another thing that does not support a long-lasting event: no alert was triggered by any of the sky surveys looking for transients, like ASAS-SN and ZTF. They detect transients in real time and after 3 days, we should have had something published already. 8.5-8.6 is really bright.
Cheers,
Sebastian
It is puzzling. Kind of fun, too. For one thing, it is great to know about additional databases to query.
Also, I observed the double over a period 10 minutes or so. Viewing it. Writing notes. Viewing it again. Writing more notes. At the time, I didn't really think that much of the surprise star, because it isn't that unusual with Sky Safari to misrepresent a given star. I mean the accuracy of the application is excellent overall, but out of millions of stars (I think in the Pro 7 version) some percentage has incorrect data.
Maybe a geo stationary satellite. It certain wasn't moving relative to the A/B components during the period I observed it. We'll see what I find tonight. ;-) (I don't have a problem owning my mistakes, BTW.)
And I'm interested in learning more about sky surveys looking for transients.
Mostly I just love studying the night sky with binoculars.
Fiske Miles
explorethenightsky.com
Hey, Sebastian.
Just back in from an observing session on my driveway, only interrupted once by gunfire. lol (Not a usual circumstance in our sleepy suburb.) At least it was a few blocks away and a quick 911 call resulted in patrol cars cruising by minutes later.
Anyway, I confused STF 2707 for ARG 39. So, your guess about it being an identification issue was exactly right. I was navigating from f2 and f1 Cygni to V2140 Cygni, to HIP 102635. And from there to what I thought was 51 Cygni, but in reality was HIP 101350. That 51 Cygni is 5.4 mag (similar in brightness to the 5.59 magnitude HIP 102635) while HIP 101350 is 6.98 magnitude should have been a clue I had the wrong reference star. I had flipped the filter on the Sky Safari list of Cygnus doubles to only show objects not already observed, and since I had previously observed STF 2707, it was not highlighted and I didn't notice its proximity to ARG 39. And etc. ;-) The star I actually observed is the C component of STF 2707. At least I got the magnitude and distance estimates close (8.64 and 55" from the A component). Let's just not worry about the position angle. (194.7* -- so south of the A component, not north.)
I am still going to explore the variable star databases you recommended and the sky surveys.
I made my observation of the actual ARG 39 system at 2023-09-28.135.
Best regards,
Fiske Miles
exporethenightsky.com