Affiliation
American Association of Variable Star Observers (AAVSO)
Fri, 05/17/2013 - 16:16
Just attended the Webinar presented by Jeno at the AAVSO Spring 2013 meeting. Neat stuff. I'll reiterate some questions that I had at the webinar here for everyone's benefit:
Will our optical observations be coordinated with your radio observations (observing at the same time)?
In which optical bands would we be working in?
Will observations be announced via AAVSO Alert/Special Notices?
Michael
Hi Michael. Sorry it took me a while to get back to you. Here are a few answers to your questions:
1. For our project, it will be very useful to get optical observations that occur at the same time as the radio observations *and* optical observations at other times. In other words, optical observations can provide useful information even if they are not coordinated with the radio observations.
2. A variety of bands would be great, if a particular target is bright enough, so that we can see how the color is evolving. But a comprehensive V-band light curve will also be important.
3. I will work with Matt Templeton to determine when Alerts or Special Notices are appropriate. I imagine that we will issue alerts for new eruptions and when a nova's behavior changes dramatically, but not for every radio observation.
Cheers,
Jeno
Thanks for aditional info Jeno. For an observation schedule outside of Alerts or Special Notices, you could post it here or share a Google drive spreeadsheet. You're in my circle at Google. Here is my profile: https://plus.google.com/u/0/104889693035082401323/
Michael
Hi Jeno,
Do you have any specific targets in mind for observation or should we just pick some from the "Nova in VSX" list posted in this forum? I recently obtained full access to the iTelescope network and thought I might get started with observations that would be useful.
Thanks.
Dave
Hi Dave. Thanks for asking about specific targets.
Two recent novae that we are monitoring in the radio are N Sco 2013 and N Cep 2013. Both are now fairly faint in the optical, but still very interesting.
The N Sco 2013 eruption began in early June, and the AAVSO light curve indicates that it currently has a V mag of ~17. But this nova has been forming dust, and so it might still be bright at H and K, and the source could also bounce back in the V band once the dust clears.
The N Cep 2013 eruption began in early Feb, 2013. We first detected it in the radio in 2013 March (ATel #4950). The last observation submitted to the AAVSO seems to be in 2013 April, at V~16.5.
And going back a little further in time, one of the most exciting recent discoveries in the field of nova research is that some novae produce detectable levels of gamma-ray emission. Since 2010, three nova have been detected at energies of greater than 100 MeV with the Fermi Large Area Telescope (Cheung 2013, arXiv:1304.3475). The first of these gamma-ray novae, V407 Cyg, resides within a symbiotic star. Many researchers (including my collaborators and I!) therefore initially concluded that gamma-ray production must be associated with the interaction between the ejecta from the white dwarf and the wind from the red giant.
But then Nova Sco 2012 and Nova Mon 2012 came along.
N Sco 2012 and N Mon 2012 do not appear to be have red-giant companion stars. So, something other than interaction with a wind from the companion must have generated the gamma rays. As part of what we call the EVLA Nova Project (or sometimes the JVLA Nova Project, since the Expanded Very Large Array was renamed the Jansky Very Large Array), we are using radio and X-ray observations to try to uncover shocks that might be responsible for have produced the gamma-rays in these novae. In N Sco 2012, the radio emission first rose, and then faded, and has recently been rising again.
We'd love to find out what N Sco 2012 is doing in the optical. If anyone is able to image this faint (V ~ 19) object, would you be willing to obtain some photometry and submit it to the AAVSO?
Thanks!
Jeno
Hi Jeno,
I have been observing N Mon 2012 very intensively the past season. Most of the AAVSO data are miy submission. ARe you interested in further observations? I see that Monoceros is already up in the monring sky at my remote site, so I could see what is the present brightness level.
It seems that I have mnissed N Sco 2012 as no observations are found in the AAVSO database from me. Or does this nova has a variable name by now?
Josch
Hello Jeno
I will be going to my observatory in NH tomorrow. Do you have any cadence preferences, or do you just want a couple of shots each night? I could also do a time series for an hour or so.
Gary
Hi Gary. At this point, it would be great just to get a sense of the current optical brightness of N Sco 12.
Then, *if* it is bright enough, an hour-long time series to search for flickering -- which would suggest that accretion disk is alive an well -- would be fantastic.
Cheers,
Jeno
Jeno,
Thanks for the information. I'll start working all the targets you identified (N Sco2013, N Cep 2013, N Sco 2012, and N Mon 2012). I already imaged N Cep 2013 last night since it was an easy target in view. I imaged in V, but some of the above comments indicate it might be good to include other filters...I'll do that as I go thru this.
Dave
Hello Jeno
Nova Sco 2012 was 16.5 last night in V. 22 data points in a 1.5 hour time series posted in db.
Verry marginal night. Shooting thru air mass of 4+. Uhgh!!
Gary
I obtained a single 180 sec V band image of V809 Cep (N Cep 2013) this morning with the Bradford Robotic Telescope. A quick look at the image showed that the nova's magnitude was 18.2V (+/- 0.2). There is a mag 16.7V star located about 8 arc-seconds NW of the nova, so observers should be careful to i.d. the nova correctly. This companion star is shown on the AAVSO "F" scale chart for the nova.
Bob
Bob (and Jeno),
I imaged N Cep 2013 on 7/6/2013 for 300 seconds and got V= 16.662 with an error of 0.046 and std=0.003 from VPHOT using iTelescope T16. I used 2 comp stars and a check star and was playing around with different combinations of comp/check stars. All results were similar but the data above was the best (lowest error) configuration.
I haven't uploaded this to AAVSO since the error is higher than they like. I want to look at this object again, perhaps with different filters, before making it "official" to AAVSO.
Also, Jeno, I imaged N Sco 2012-V1324 Sco for 300 seconds on 7/8/2013 (same scope) and got V=16.884 with an error of 0.088 and std=0.012 again using 2 comp and 1 check star. However, the image was blurry since there were high winds during the imaging period. I'll take another look at this nova and hopefully get more reliable results. But at least its a data point.
Dave
Dave,
When you last imaged N Cep 2013, did you also see the mag 16.7V star 8 arc-seconds to the NW?
Bob
Bob,
The target was V0809 (N Cep 2013) in the AAVSO data base as indicated by VPHOT, so the V magnitude should be as reported above. It corresponded to the RA/Dec for N Cep 2013/V0809 so I believe that the measurement is correct (i.e.,the correct target). I did see a bright star in the vacinity of this nova, but I had the annulus settings tight around N Cep 2013 so I don't think I was getting any noise from nearby objects.
I'll try to get another image within the next couple of days. Since your measurement was more recent than mine, maybe the thing has gone active. I'll post the results when I get something.
Dave
Dave,
I've never used VPHOT, but with MIRA, the aperture tends to jump to the nearby brighter star if I click on the fainter nova. I have to manually recenter the aperture. Does VPHOT center the aperture automatically or do you have click on each star manually?
Here is a link to an animated .gif that blinks an image taken in February (when the nova was near maximum brightness) with a POSS2 image from 1991:
http://i176.photobucket.com/albums/w189/walcom77/pnv_cep_02_feb_2013_I89_zpsd5880a86.gif
The animation is from this page:
http://remanzacco.blogspot.it/2013/02/possible-nova-in-cepheus.html
Note the 16th mag companion star just to the upper right of the nova.
Bob
Bob,
Things have gotten interesting!
After I responded to your message last night, I reimaged N Cep 2013.
I used a different scope (iTelescope T7...T16 was busy) with the same parameters (V for 300 seconds, etc.). This morning I analyzed the image with VPHOT using the same comp/check stars I used for the previous image.
Guess what??? The data showed V=17.898 with error=0.057 and std=0.020. This is close to your measurement from the other evening. It looks like this object has changed over the past 2 weeks.
So, here's a summary of my data. I'll image again in about a week and see what this thing is doing. At that point I may officially upload the data to AAVSO. Perhaps you can look at it again too.
7/6/2013: V=16.689;error=0.050;std=0.011
7/18/2013: V=17.898;error=0.057;std=0.020
Dave
Dave,
That is interesting. I just wanted to be sure that observers were looking at the nova and not the mag 16.7V star nearby. I have requested that BRT observe the nova again, but turn around with this scope is usually 2-3 weeks.
Perhaps we should start a new thread for this star (ie. "V809 Cep").
Bob
Hi Dave,
You might VPHOT-share the two images with HQA, and I'll take a look at them. My guess is that the faint variable was not correctly measured on 7/6, but a simple inspection should tell whether the nearby companion is brighter or the same brightness as the target.
Arne
Arne,
I uploaded both images of N Cep2013 to you. Please let me know if there are any problems with either of them and how to correct the problems.
I used stars 128, 138 as comp stars and 123 as the check star for both images. I know the errors are greater than AAVSO likes to see but this is (I think) the best I can come up with. Let me know if there are better ways to do this.
Thanks.
Dave
Hi Dave,
I looked at both images, and by simple visual inspection, it is pretty obvious that V809 Cep is about the same brightness in both, and definitely fainter than the 16.7mag close companion just to the NNW. I think the 2013-07-06 image has been mismeasured, with VPHOT perhaps snapping to the nearby brighter star for that image. I would not report your brighter 07-06 estimate. Let me pass these on to Geir and see how to solve this issue for the future.
Nice image quality, BTW!
Arne
Arne,
After I got your post this morning, I went back to both images and very carefully measured both of the stars (N Cep as well as the other object). I believe that you (and Bob) are correct that I was looking at the other star since they're so close.
Upon further analysis I determined that N Cep is indeed about V=18 and the other star is about V=16.6. VPHOT wasn't the problem, the guy using VPHOT was!!!
I'll fix the analysis for these and upload when everything is correct.
Thanks for the feedback. This really shows the power of these forums where we can work together to get it right and do good science.
Dave
Hi Dave,
Those numbers look reasonable. If you look at the current light curve, most of the observations are stuck at V=16.5 due to the nearby companion. Your V~18 measures sound more realistic to me, and you've placed a reasonable error bar on your faint measurement. I'd go ahead and submit.
Arne
Hi Josch,
Nova Sco 2012 == V1324 Sco
Nova Mon 2012 == V959 Mon
I have four BV measurements for V1324 Sco, taken with OC61 in April 2012, but nothing since then, and nothing for V959 Mon from OC61. I do have about 9 BVRI datasets for V959 Mon from BSM_South during the outburst. However, neither nova was extensively monitored by AAVSO observers (except you!), possibly due to the southern declinations for these two objects and their rapid fading.
I think a late-time observation of either nova, especially deep and filtered, would be useful. If you can do two filters, I'd go with B&V as those are the ones I'm using for my late-time nova survey from OC61 and TMO61.
Arne
Hi Arne,
thank you for this information.
I will see what is possible for N Mon 2012 as I could add snapshot observations to my script.
I have BVI filters, so could do V, I as I did the past season.
Josch
Hi Josch,
Thanks for taking another look at V959 Mon.
All novae since January 1, 2000 are on my observing list at OC61/TMO61, to get at least a single epoch deep BV pair. I've imaged 33 of the ~100 novae so far. Most are in pretty crowded regions, so obtaining photometry from the images is quite a challenge.
Arne