Affiliation
American Association of Variable Star Observers (AAVSO)
Mon, 01/09/2017 - 18:54
Hi!
What are people here thinking about this story: https://www.newscientist.com/article/2110005-double-star-may-light-up-t…; ?
Link to preprint: http://www.calvin.edu/academic/phys/observatory/MergingStar/MolnarEtAl2…
Looks like KIC 9832227 is well within the reach of amateur observers.
CS
HBE
Hello All
I have been reading about this in a few articles and would like to submit observation data.
I see that there is a star chart at 1 deg FOV for KIC 9832227 with three comp stars available. This FOV is out of my FOV range and would like to use APASS stars within my FOV.
How do I refer to them as they do not have ID's yet, only coordinates?
John R
Interesting. I was able to plot a chart 2 degrees on a side using VSP, and suspect I could plot one with other FOVs as well. I just used the star's ID.
You are correct that there are no suitable comp stars within a 2 x 2 degree FOV as given by VSP, but there are many candidates if you look at SeqPlot. Trouble is that most of those are Tycho 2 stars, for which the accuracy is inadequate, given they are in the 12 - 13 V range. But there are also a fair number from APASS in the list.
A great opportunity to try out one of the great services of the AAVSO. Go to the main menu, then Observing/Variable Star Charts/Request Comparison Stars. There they lay out the instructions.
For your case, where there are some stars already available, you are supposed to use CHET ( https://www.aavso.org/chet ) the Chart Error tool. Just tell them you need comps for your FOV. If you go to VSX you can see what FOV's (ie VSP chart sizes) are currently supported. The sequence team is great and you will have your comps within days.
Let's hear it for our Sequence Team!
George
Hi George
I tried this before without much success in asking for comp stars.
I will try again and also look into the VSX page to look up charts sizes first.
Thanks
John R
Note that you won't get an email back from CHET when they handle your request. You need to go back to the CHET page and do a check. They've handled my requests within 2 days.
George
And there is even a movie trailer about it!
Cheers,
Sebastian
There is a new sequence for KIC 9832227.
Jim Jones
Sequence Team
Really? It is more than 2 hours since your post, and VSP is showing no comparison stars within a 2x2 degree rectangle centered on the target that are within 3 magnitudes of it. (But SeqPlot shows numerous candidates in the 12 - 13 range.)
Just checked. There are 5 comps within a F chart.
Many of the 12-13 mag stars shown in APASS have companions of various strengths. Cyg makes for a crowded field.
Jim Jones
We just extended the sequence and there are now 8 comps within an F chart.
Jim
Jim
Thanks! That was really fast, I am sure it will come in handt for alot of people.
John R
Jim
Thanks again.
I checked your selection and found that three of them were APASS stars that I had concidered using when i first posted the question.
Thanks again to you & your team!
John R
Thanks! It's just what I need.
While on the topic, I want to say that although I really appreciate what the sequence team does and, as a neophyte have no justification to complain, what you folks do seems mysterious in many ways to me. I don't want to go into details, but I have a number of examples of where it seems that the choices in the photometry table either do not match their values in SeqPlot, or are apparently not as good as those listed there. Also it is often the case that there is inadequate support in terms of numbers, colors and magnitude range for ensemble photometry, which is what we CMOS camera folks do. Like I said, I am not complaining, but merely wondering. Personally, I think it would be great if someone on the sequence team could find the time to write a tutorial or give a presentation at one of the AAVSO meetings, discussing the process of determining which stars are suitable as comps, why you prefer some catalogs over others, and similar things.
Again, thanks to the sequence team for your tireless work!
I have to admit that my retirement may have helped lead to this investigation. It was at the meeting organized on the occasion of my official retirement in 2013 that Larry Molnar and Daniel van Noord heard my former student Karen Kinemuchi give a talk about KIC 9832227. Intrigued, they began studies that would eventually lead to the prediction of a 2022 nova. It will certainly be cool if the event does happen as forecast.
Dear Horace,
There are several arguments putting the supposed 2022 explosion in doubt. First, the current period acceleration rate is two orders of magnitude (actually even 200 times) slower than that of V1309 Sco observed 8 years before the outburst! Pdot for KIC 9832227 was -5.4*10-9 in Kepler data, currently raising to -1*10-8. But V1309 Sco already had -2*10-6 in 2001! It took 129 years for V1309 Sco to reach that acceleration from the formal threshold of -1*10-8. Here the merging is predicted to occur in 5-6 years! Sounds inconsistent.
Another statistical argument against the possible Nova explosion is given by the authors in the article. The merging rate in our Galaxy is estimated to be 1 event in 10 years. Authors write that 13 stars in Milky Way should exceed the formal limit of -1*10-8 at any given moment of time. Now let's calclulate - what's the probability of one of those 13 stars to be brighter than 12.5m? There are about 5 million stars in the sky above that value, while there are more than 100 billion stars in our Galaxy. Chances of having one star brighther than 12.5m among those 13 with unusual acceleration are less than 1:1000! Of course, this is an indirect counterargument, just as any statistical one.
The paper says nothing about the critical acceleartion rate at which components will merge, neither what the orbital period should be at this moment. If we continue the analogy with V1309 Sco, the period derivative before the flare should exceed -2*10-6. Let's compute when KIC 9832227 will reach this value under the current acceleration rate.
If we look at Figure 14 in the article, we will see an exponent approximation based on two points. Pdot was -2*10-9 in 2007, and it has grown to almost -6*10-9 by 2013 (3x in 6 years). Even if the acceleration is exponential with a characteristic time of 6 years, then it is only 30 years in future when Pdot will grow by 35=243 times and will reach -2*10-6. Why 2022, again?!? At best 2043!
Denis in Moscow
Denis,
I should make clear that I am not involved with the current work on KIC 9832227, so that what I know is limited to what is in the preprint. I am certainly no expert on binaries like this, so you are likely more familiar with such systems than I. However, I suspect that your argument from the 5 million stars brighter than mag 12.5 needs to be tightened up a bit to come up with the probability for finding one candidate star brighter than that mag limit. Many stars in the Galaxy will be intrinsically faint red dwarf stars, either single or in binary systems. The sample of 5 million stars brighter than mag 12.5 is already tilted against such stars, so a total of 100 billion stars in the Galaxy is probably not the right comparison population. The probability by this method with a more appropriate comparison population is going to be more than 1 in 1000, isn't it? How much more would need calculating. The timescale the authors derive for the nova event depends critically, of course, on the validity of equation 3 in the preprint, and upon the parameters the authors adopt for KIC 9832227. I am sure that those issues will be being given increased attention after the recent publicity for the possible nova event. Will KIC 9832227 follow the predicted rate of period change? We should know that before the 2022 date.
Sounds like a fun one to add to the list. I see the 8 comps on a 20' chart.
Ray
GM All
In addition to "Bikeman's" articles this is the first one that got me interested.
I am sure and hopefull that there will more to come here at AAVSO on this object too.
http://www.skyandtelescope.com/uncategorized/stars-en-route-to-merger/
John R
> I am sure and hopefull that there will more to come here at AAVSO on this object too.
Indeed, I think this object and the associated prediction has quite some potential for outreach and new-observer-recruitment. It's an exciting prospect to see evidence for the predicted nova strengthen (or weaken, who knows) as more observations will come in over time.
In an interesting development, a re-examination of the data revealed that the original prediction of the binary system merging in ca 2022 was based on a typo in one of the cited papers. Interestingly, the pre-print of that paper still contains the correct numbers, but the final journal version had the typo. With the corrected data, it doesn't look like a red nova can be predicted to happen anytime soon (in an astronomical sense of "soon"), if at all.
https://www.skyandtelescope.com/astronomy-news/typo-no-binary-star-merg…
Too bad.
CS
HB