Tue, 10/16/2012 - 19:09
Steve O'Connor has been monitoring the symbiotic star AS 270 (18 05 33.73 -20 20 38.1) for awhile, and noted that it has risen by almost a magnitude over the past few months. He had it at V=13.33 on the night of October 14.
Continued V-band monitoring is encouraged in case the star is headed for a full outburst.
I estimated it at v=13.9 last night, just slightly brighter than the 14.1 two weeks ago. It appeared to show some flaring of a few tenths of magnitude.
Mike LMK
Looking at LCG, there appears to be about ~2 magnitude range of this variable between 12-14, looks almost like its on a half-day period or even shorter? I am wondering if this is real behavior, or some issue with the comp stars people are using? I haven't been able to follow it as much myself as I would like to get my own feel for it.
Mike LMK
Hi Mike,
The light curve is very curious, and it now looks like there are parallel tracks in the light curve separated by quite a lot. I'm not sure what's going on -- whether the star is doing something very strange, or there's something going on with the observations. I'll get in touch with the observers involved to investigate.
Matt
I have only uploaded 1 set of data for this star. I looked at the other data and there is a big spread. Something is wrong. I checked my measurements by uploading some images to VPhot and got similar results to my submitted data.
Some of the V measurements are actually CV measurements so these will be different.
I took a spectra at the same time as my photometry and it demonstrates an M type continuum but with very strong H and He emission lines. This will make the CV readings quite different to the V readings. Still doesn't explain the spread though.
Terry
Hi Terry,
Yes, Sara Beck discovered this morning that some of the very bright CCD data are unfiltered. I'll send a message to all of the recent observers to verify what methods they're using and whether the types of observations they're making are appropriate.
Nice spectrum by the way!
Matt
Hello
This sounds like another reason to separate the unfiltered V measurements from the V measurements. The light curve generator should be changed to only plot filtered V measurements when requested. If one wants to see the unfilted V measurements, they should select them in the LCG.
Its clear that unfiltered with V zero point is not the same as filtered V. This should go to the top of the list of bug fixes for the LCG.
Gary
Hi Gary,
the LCG does provide a mechanism for removing unfiltered observations. There are click-boxes in the input form to add/delete unfiltered observations. What needs to be changed is the color of plotted points, and this is part of the plan for LCG revision.
arne
[quote=HQA]
the LCG does provide a mechanism for removing unfiltered observations. There are click-boxes in the input form to add/delete unfiltered observations. What needs to be changed is the color of plotted points, and this is part of the plan for LCG revision.
arne
[/quote]
I tried checking and un-checking the "unfiltered" boxes, but it made no difference, the wide variation in measurements between mag 12-14 remains in the plot. It appears the mag 12 observations are both visual and V.
It sure would be nice for the LCG to give all information on a given point (observer, filter, comp stars, etc.) by mousing over or right clicking on a selected point, showing a popup floating info window or the like. Right now, its very difficult to identify the information on any given point in the plot, without time-consuming checking and un-checking of boxes to see what goes away or stays!
Mike LMK
I have removed my unfiltered data as they seem not appropriate for this star. I already started to use V filter two nights ago, but only submitted today.
They are in line with dta of observer NLX.
Josch HMB
Hello Arne
I just tried RZ Leo, JD 2456440 to present. With V unfiltered, I get 2 data points, 18.98 and 18.25 aprox at JD 6447 and 6452.
When I plot only V, I get these same 2 points along with the V filtered data. There is no way to get V only data without the V unfiltered data. Yes the points are all green, but they should not show up there.
Gary
Hi Gary,
That looks like a bug. I'll have someone look at it - thanks for pointing it out!
Arne
Whilst the CV measures seem to have become consistent now, the discrepancy between some visual measures is continuing, and maybe worse? There remains a set of visual observations around mag 12 or even brighter. I have observed this star 3 times, and never sen it brighter than 13.8 visually.
Could there be some mis-identification issue or chart problem which is causing this? It doesn't seem plausible the star is rapidly "switching" between mag 12 and 14 on short time scales.
Mike LMK
Hi Mike,
If you have suspicion that one or more observers may be incorrectly estimating or reporting their data, I recommend that you use Zapper, available on our website at the Data/Data Analysis menu, or directly at
http://www.aavso.org/zapper
and report the observations to HQ so that staff can investigate them. My guess is that these are upper limits, as other observations from the same observers at the same level are given as fainter thans, and they probably forgot to include the "<" sign in their report. Zapper is a good tool, and your careful eyes will be valuable in finding other potential problems. I thank you in advance for volunteering your effort!
Arne
Hi Arne, Ok I just submitted those in qestion by Zapper. I was a bit unsure of any issue with these observations because I have'nt that much experience with this star,and thus was posting comments here to get some better feedback first. Thanks,
Mike LMK
[quote=HQA]
Hi Mike,
If you have suspicion that one or more observers may be incorrectly estimating or reporting their data, I recommend that you use Zapper, available on our website at the Data/Data Analysis menu, or directly at
http://www.aavso.org/zapper
and report the observations to HQ so that staff can investigate them. My guess is that these are upper limits, as other observations from the same observers at the same level are given as fainter thans, and they probably forgot to include the "<" sign in their report. Zapper is a good tool, and your careful eyes will be valuable in finding other potential problems. I thank you in advance for volunteering your effort!
Arne
[/quote]
Hi Mike,
Thanks for zapping those observations. I also think that it was good for you to initiate discussion on this star in this forum. Everyone's focus on it has certainly made a big difference in the quality of the data.
I had actually written to one of the observers with questionable visual observations last Thursday but have not heard back from him yet so I have just marked the observations "discrepant". I can't write to the other observer because his email address is invalid, so that observation too has been marked discrepant.
Just so you (and other readers) know, when I find a situation like this or someone uses zapper to flag discrepant observations, and I agree that the observation is questionable, my usual procedure is to write to the observers first, asking them to check their records. Generally I get a response saying that they made a typo or that they don't feel confident about their identification of the star. If its a typo, either they will fix it or I will fix it for them if they prefer, once they tell me exactly how to correct it. If it is more a matter of being unsure, then I will evaluate the observation based on those of other observers around it and flag the observation as "discrepant" if warranted. If the observer tells me they are confident about their estimate then I have a harder time doing this and may wait for more data on the star. In any case, while this process is going on, I like to leave the questionable observations alone so it is easier for the observer to see them in context. That is why you may not always see an instant response from HQ when a suspicious observation is brought to our attention.
When an observer submits questionable data, I feel that it is important that they are notified privately and in as unbiased a manner as possible so that they can re-evaluate their own work and possibly learn from it or use more care in when observing that field in the future.
Sara Beck
AAVSO Technical Staff