AAVSO Alert Notice 645 announces a campaign on LPVs in support of a maser study. Please see the notice for details and observing instructions.
Many thanks, and Good observing,
Elizabeth O. Waagen, AAVSO HQ
I observed (tried) NSVS J2041274+511326 last night the magnitude range was given in the 11 to about 13 range so I selected a 30 second exposure in V...the upshot I had to stack 112 subs in VPhot just to get a SNR of 3....hmmm I think the magnitude is more like 20....
That does seem faint. VSX's 2000 ephemeris predicts that we are at minimum, and the given 11-13 range is in R. The spectroscopic class isn't given, so assuming a typical Mira V-I color at minimum of perhaps 6-8, thus a minimum V-R of about 3-4, the VSX data suggest a current V mag of about 16-17.
Unfortunately, the VSX data is old, and AAVSO's Light Curve Generator v.1 is down today, so that's about the best we can predict for now. All I can suggest for this extremely red star is to try to observe in R or I as well.
Thank you Eric. I will try I sometime next week. Here are a couple of screen captures of the 112 sub stacked photometry. I was able to eek out an SNR of 5 in V. (All subs are fully calibrated , Vphot does not recognize AstroimageJ calibration headers so that's why it says calibration non..but they are fully calibrated..)
It's not a collimation problem is a filter adapter problem, the collimation on my setup is near perfect. The filters are supposed to be unmounted 36mm and the Photometric filters are 1.25 and mounted through an adapter which is off a little. Still pretty good for this kind of work and Exoplanet work.
If you look up this star on VizieR, you will see that it is very red (V-I~6). NSVS was observing unfiltered, and with no filter, red stars are much brighter than their true V magnitude. I am not surprised if this star is at minimum and you are using a true V filter that you are measuring 19th magnitude. You might try an I filter just to confirm the red color!
I'm used to submitting transformed V magnitudes, usually based on the B-V colors of the variable and comparison stars. These maser stars are so red, however, that I am using V-R and V-I colors instead. Last night (JD 245837.692) I got the following results for V349 Vul:
V = 12.875 (untransformed)
12.384 (transformed based on V-R)
13.121 (transformed based on V-I)
This seems like an awfully big range! Is one of these numbers likely to be better than the others? Should I go with the untransformed number? Should I submit the average?
I presume that the large differences stem from large deviations from a blackbody curve, due to absorption bands and interstellar reddening. Also, my transform coefficients are based on stars in M67, few of which are as red as the maser stars. So what is the best thing to do?
Yes, that's a good move. B-V colors make for very poor transforms (other than for B) for red stars, for which B magnitude has little to do with the vast bulk of the photon flux. Using > 100 model star spectra I demonstrated this in my SAS 2014 talk:
V-I color is pretty ideal for transforming V, R, and I observations of very red stars. Of course settings exposure times can be a headache, and one frequently has to bracket the first time around, but that's a different concern.
V-R can work too but the statistics are not as precise.
I wanted to say thanks for the great work by everyone so far with this campaign. I wanted to mention a couple of notes.
First, V Cas is also one of the sources on our list. It historically has great coverage by AAVSO, so I expect we'll be fine, but feel free to help out on that one if you can.
Second, the start of our VLA campaign was pushed back to November from October. They made some hardware upgrades at the VLA this summer and they need a little more time to finish up the current observing programs.
But thanks again everyone for the already great looking work! I can't wait to have the radio observations so that we can start comparing our results.
I have just submitted one measurement for each of the following:RT Aql, SX Cyg and AU Cyg. Acturally the pictures were shot by a friend, Remi Lacasse,whom I hope eventually will convert to variable stars.
He doesn't have photometric filters yet. Since he normally do color photos with RGB filters, I suggested he use the R filter for his pictures.
He also took pictures of V1655 Cyg and V1659 Cyg, but 5 minutes exposures were not enought to show these variables.Can they be that faint?
There are 19 stars in the AN 645 list, which only the top 4 appear to be in the Target Tool. Many others in the list are being actively observed as evidenced by their light curves. Would it be possible to have the rest of the AN 645 stars included in the Target Tool to make it easier to find those that have not been observed recently?
Thank you for letting me know that some of the target stars from Alert Notice 645 were not in the Target Tool - I must have been sidetracked while entering these stars and didn't finish! I have now added all of the stars in the campaign to the Target Tool for V and visual observations.
Thanks again, and Good observing!
Thanks everyone who has contributed to this effort. There are some really nice light curves for some of the sources. I try to download the light curves once a month to update my own records, but if I happen to forget, and you don't receive the alert, please be reassured that your observations are crucial to this campaign!
It looks like V1301 Cyg and V1659 Cyg are particularly difficult, and the light curves are needed to put the radio observations in context. Thus, I'm switching out those two sources from the radio program and am adding in the following two sources. They still may not be great, but maybe they are a little better.
- V0657 Cas
- V0850 Cas
All sources in this program should be very red so trying redder filters such as R and I might help for the weaker ones.
Thanks again for all of your help!
AAVSO Alert Notice 660 gives the revised target list for the LPV SiO maser campaign announced in AAVSO Alert Notice 645. The stars added, V657 Cas and V850 Cas, now have sequences; the stars V1301 Cyg and V1659 Cyg have been dropped. Please see Alert Notice 660 for details and observing instructions.
Many thanks, and good observing,
Elizabeth O. Waagen, AAVSO HQ
Thanks again to everyone who has contributed to this project. Our VLA observations have been successful so far, and we've been able to detect SiO maser emission for all of the stars in the sample. This is hopefully a good sign for our continued monitoring with the VLA until October 2019.
We recently submitted a second VLA request for a 2nd year of observations of these sources. This would take us from October 2019 to October 2020.
Your observations are vital to this program and I am grateful for everyone's hard work!
If you plot the AAVSO data of VX Cep from 245000 to the present, it can be seen that there have been several other maxima as bright as the current one. However, the earlier maxima did not have coverage of the complete cycle of variation, so observations are encouraged to provide this coverage and to assist in Dr. Stroh's maser campaign (AN 687)!
Many thanks, and Good observing,
I joined the campaign only after it was recently extended and wanted to see what I can do for FI Per.
After making a few measurements, I'm convinced now that one of the comp stars that is frequently used for FI Per is seriously off in the AAVSO photometry charts, e.g. the sequence X25004XX .
The star in question is
V: 14.684 (0.050)21
(B-V) 0.385 (0.087)
I. 14.315 (0.087)
However with an ensemble of 4 different comp stars, I get
V = 13.98 , I = 12.84
so the V mag is 0.7 mag off (!!),
Also a search in APASS gives V= 13.954 (0.051).
I guess I could just file a "bug" report for this star with the chart team, but since this comparison star was extensively used already for FI Per in the current campaign, a correction of its value might be quite disruptive? After all the campaign is (as I understand it) about the ephemerides of the Miras, and not so much about precision measurement of the magnitue per se. Yet this big difference between the recent and previously filed photometry for 000-BJZ-887 (almost a factor of 2!) could perhaps hint at some variability of that comp star itself..
So how can this be fixed/dealt with? Just leave it to the scientists requesting the campaign to figure out offsets between observers even as high as 0.7 mag?
Clear Skies and a happy New Year 2020
Removed label from existing 147 comp 000-BJZ-887. This would have ended up as a duplicate 140 label. Cleary the SDSS data for this star was bad.
Added 147 comp star 000-BNJ-742
Brad Walter, WBY
In the previous post Brad Walter reported that the original 147 (000-BJZ-887) for FI Per was removed and a new 147 (000-NBJ-742) added (thanks, Brad). To eliminate confusion in your reports about which star '147' is referring to, it is ESSENTIAL that you include the AUID of the star.
If you have used the original 147 (000-BJZ-887) in making your observations, it will be necessary for you to re-reduce your data, remove the old observations (using WebObs), and upload the revised ones. If you have trouble doing this, please let me know. In looking at the data submitted to the AID, I see 3 observers who used the 147 (000-BJZ-887) : DFS, EHEA, KNAA.
If you have charts for FI Per, please replace them with new ones that show the correct 147 to be used.
Many thanks, and Good observing,
I re-submitted corrected photometry, but then again I had only 4 data points,.., too bad for those who have many more spanning > 1 year.
As a sidenote: This is a bit unfortunate, I wasn't even the first to spot this error, back in Feb 2019 an observer added this comment to his/her observation "AAVSO HAVE INCORRECT VALUES FOR COMP STAR 14.7 "
Of course it is kind of super optimistic (to put it mildly) to hope that AAVSO staff has a chance to spot this in the stream of thousands of data points submitted each day. The days when observations were added to the files manually by a clerk are over, so if you spot errors, please report them directly to the staff (I cannot know whether that observer also did that, of course, but observation notes are not the place to do this).
I wanted to thank everyone again for your help with this project. We have ongoing VLA observations which will continue through October. The exact end date will depend on when the VLA observing semesters end which may change a little due to the covid situation.