Affiliation
American Association of Variable Star Observers (AAVSO)
Tue, 07/11/2023 - 16:14
AAVSO Alert Notice 828 announces a campaign beginning immediately on the SU UMa-type cataclysmic variable V844 Her. Please see the notice for details and observing instructions.
There are threads for this campaign under the following AAVSO forums:
- Campaigns and Observing Reports: https://www.aavso.org/v-844-her-campaign
- Cataclysmic Variables: https://www.aavso.org/v-844-her-campaign-01
Please subscribe to these threads if you are participating in the campaign so you can be updated. Join in the discussion or ask questions there!
Many thanks, and Good observing,
Elizabeth O. Waagen, AAVSO HQ
We took a look at V844 Her last night with the Notre Dame campus scope (the Sarah L. Krizmanich telescope). It was near its typical quiescent mag of 17.
It has had two "normal" outbursts since the last super-outburst, although we might have missed a super-outburst when V844 Her was behind the Sun. Either way, I think we are due for a super-outburst soon.
I see several observations in the AAVSO database added in the past week. In particular, Ian Sharpe has done a few time-series observations. Thank you! This sort of observation will be critical when the outburst does happen.
Good observing!
Peter
I just…
Thanks Peter,
I just uploaded another run of 166 exposures from last night.
Best Regards
Ian Sharp.
Greetings,
I would normally do this type of observing. However, the weather for the last 4 months or so here in central Virginia has been cloudy, dismal & rain around the frontal boundaries and then the new clear. The new clear in central Virginia means smoke or worse heavy smoke from the Canadian fires. The smoke layer normally is in the mid-altitudes occasionally at the surface and sometimes at high altitudes. In the last four months we have had maybe 3 or 4 photometric nights and I use that term very loosely.
Getting too old do be doing this anyway...
Jim DeYoung
I know what you mean. Our best weather is when the wind is from the northwest, but that direction now brings the smoke from Canada. Certainly at 17th mag, the conditions are not great. But when V844 Her goes into outburst, even smoke will be no match for 13th mag!
Peter
All,
The paper describing the new periodicity in V844 Her has arrived on the astro-ph server:
https://arxiv.org/abs/2308.10344
The 29-min periodicity was seen only during an outburst caught by TESS. It is not observed during quiescence by TESS, X-rays, or optical ground-based monitoring.
There is some evidence of the signal in Arto Oksanen's photometry series in the AAVSO database from an outburst in 2006. I am hoping that we can get great time-series coverage during the up-coming outburst (arriving soon I hope).
Peter
Thanks for the update Peter. Hoping for clear weather when the super-outburst arrives...
-Walt
All,
Jim DeYoung just reported that V844 Her was unusually bright last night. This may be the start of an outburst - normal or super, it is too early to tell. At V=16.79, it is about twice the brightness it has been. In superoutburst it can reach V~12.
Please do intensify monitoring this star to see if it continues to rise. If this is an outburst, I ask that long time-series photometry be obtained. The unusual period detected in TESS is 29 minutes. The signal is rather weak compared to the superhumps that will exist. So time-series lasting 2 hours or more are needed. And photometry on several consecutive nights is ideal.
This may only be a blip, but it does look promising.
Peter
Hello Everyone. I wanted to let people know that are interested in this star, that it appears to be very bright right now. Using AUID 000-BBX-846 which is 12.352 mag as a reference, I am getting 12.252 V-mag for V844 Her, (about 0.1 mag difference in quick look photometry using MaximDL). if I am identifying it correctly, which is near its peak brightness for it according to the chart. I will follow it for as long as I can tonight. I took a look at the AAVSO light curves from a a couple weeks ago and it is not this bright. Maybe I am misidentfying it? Anyhow, I thought I should let people know just in case something is happening.
Hello Everyone. I wanted to let people know that are interested in this star, that it appears to be very bright right now. Using AUID 000-BBX-846 which is 12.352 mag as a reference, I am getting 12.252 V-mag for V844 Her, (about 0.1 mag difference in quick look photometry using MaximDL). if I am identifying it correctly, which is near its peak brightness for it according to the chart. I will follow it for as long as I can tonight. I took a look at the AAVSO light curves from a a couple weeks ago and it is not this bright. Maybe I am misidentfying it? Anyhow, I thought I should let people know just in case something is happening.
All,
This does look like the real thing. I'm looking at V844 Her now and it is near it is 12th mag, typical of its superoutbursts.
The outburst should decay 3 mags over 2 weeks. It is this entire period where TESS detected the 29 min periodicity. So long time-series over the next two weeks will be very useful.
Good observing!
Peter
Only 25 minutes before the clouds rolled in. A very short time serie in V-filter :-) Is already in database.
Hello Everyone. I wanted to let people know that are interested in this star, that it appears to be very bright right now. Using AUID 000-BBX-846 which is 12.352 mag as a reference, I am getting 12.252 V-mag for V844 Her, (about 0.1 mag difference in quick look photometry using MaximDL). if I am identifying it correctly, which is near its peak brightness for it according to the chart. I will follow it for as long as I can tonight. I took a look at the AAVSO light curves from a a couple weeks ago and it is not this bright. Maybe I am misidentfying it? Anyhow, I thought I should let people know just in case something is happening.
AAVSO Alert Notice 834 reports on the outburst of V844 Her and important instructions from Principal Investigator Dr. Peter Garnavich. Please see the notice for details.
There are threads for this campaign under the following AAVSO forums:
- Campaigns and Observing Reports: https://www.aavso.org/v-844-her-campaign
- Cataclysmic Variables: https://www.aavso.org/v-844-her-campaign-01
Please subscribe to these threads if you are participating in the campaign so you can be updated. Join in the discussion or ask questions there!
Many thanks, and Good observing,
Elizabeth O. Waagen, AAVSO HQ
Hi,
I just finished a 2.5 hour series (BVR) on V844 Her. I don't have time tonight to do my full analysis and submit my data, but I do have a preliminary plot of V-C for B, V and R. I used the 10.6 mag star in the AAVSO chart X29311IF as my comp star. The rms of my K-C data is ~< 0.01 mag for B,V & R. My plot suggests a periodicity, but not of the 29 min. mentioned in the Alert Notice 834. I will try to get the data submitted asap.
Tony...
Here's the link to the graph: V844HerPrelimPhotGraph.png
All,
We got 2.5-hours on V844 Her last night with the Krizmanich telescope on the Notre Dame campus. It was clear that a 0.15 mag amplitude oscillation has developed with a period consistent with superhumps.
Clouds have moved in, so it will be a few nights before we can get more data during the superoutburst.
Peter
Detectada pulsación de 85 minutos y 0,26 mag. De ampliación. Tres pulsos en 3,20. .inutls de seguimiento el día 10042023.
ATE,
Your detection of an 85 min pulsation is consistent with the superhumps developing. Thanks for your observations.
Peter
Hi all,
Just added an hour of data using V filter from Spain. It's coming out at around mag 14.1 with not much variability over the hour, although more than the check star.
Cheers
Ian.
Ian,
You might check which star you have identified as V844 Her. Others have been getting a brighter magnitude and significant variations.
Peter
Well! How…
Hi Peter,
Well! How extraordinarily embarrassing! I had indeed identified the wrong star. Never happened before!
Very many apologies. I've replaced the uploaded values and now mine agree closely to others.
Best Regards
Ian.
Peter / All,
I submitted almost 2.5 hrs of observations earlier this morning. They agreed closely with other observations from MXD and SRIC but seemed to be biased high by about 0.05 mag. Maybe this is insignificant to the time series analysis but I am curious why, maybe due to my choice of comp stars. When I get time this evening I plan on reviewing my analysis performed in Lesvephotometry. I also plan on another 2+ hr collection tonight given the execllent conditions here in central New Mexico. After that I will be out of the country for a couple weeks and unfortunately unable to continue contributing. This is fun. Thanks!
Daniel Bailey
(BIY)
I submitted some data I got over the last 2 nights and it doesn't seem to agree with what others have done. I double checked and I seem to be doing everything correctly.
Darrell Lee
LRDB
So evidently I just need to make a post about it, then go back and check my data one more time and THEN see my mistake. Now my data agrees with other observations. Can somebody give me a clue on how to remove the bad data?
Darrell Lee
LRDB
I'm not sure you can delete data that has been uploaded. When you click on a point you can report a problem, but I am not sure that is the best solution.
Peter
Hi Darrell,
To delete observations you have submitted to the AID, log in to your account and go to WebObs. Choose the Search for Observations option. On the form that comes up, choose "My Observations" and if you want to see data on V844 Her only, put V844 Her into the Star field. Click Search. Your observations of V844 Her will be shown. Tick the box next to each observation you want to delete, and then click the Delete link at the bottom of the page. You'll be asked to confirm your delete request.
If you have any problems with this, please email me (eowaagen@aavso.org).
Best wishes, and good observing,
Elizabeth
Thanks so much. I deleted them all and will resubmit good data after the Astros beat Minnesota Twins. ;)
Darrell Lee
LRDB
It'll be a while, then. ;) (Yes, I know the current score, but the Twins are more than capable of coming back).
I resubmitted my 2 nights of data and it looks much better. I am covered in clouds until Saturday, which is a bummer. By that time the Astros will be leading the Rangers in the American League Championship Series by 1 game. ;)
Darrell Lee
LDRB
All,
V844 Her is now in day 10 of its superoutburst. It is now around V~13.5. It should level off and then, in another 5 days, begin a steep fade to 16th. Please continue to get as long time-series as you can so we can look for the 29-minute oscillation. This is particularly interesting as it makes its big fade. Around 16th mag, the superhump amplitude weakens and we expect the 29-min periodicity to dominate the variations.
The Swift Satellite has so far made two visits to V844 Her. Thank you all again for monitoring this star so we could get the observations triggered early.
Good skies!
Peter
After about 1 1/2 hours of observing tonight (7:50 pm - 9:30pm EDST) a preliminary light curve shows bumps at about 30 minutes. Will continue observing until V844 drops out of sight (~10:30 pm).. Superhumps are quite faint.. About same amplitude as the 30 minute bumps.
Don (CDK)
Peter
As the fade continues, are there certain points in time that could be especially useful to have data for, or, now that you have some perspective on this cycle, are there certain other filters or specific cadences that could give added value to the remaining observations? With all the observation locations available within your AAVSO observing team, it seem likely someone could be positioned to gather data at almost any time if there are stages in the dimming process of particular interest.
Also, when the dust settles on this Alert, could you perhaps take a few minutes and provide a few insights into specific research goals you have for the data?
Thanks and good luck!
Gary
Gary,
Thanks for the question. There are a number of things we plan to do with this wonderful data set.
1) Put all the light curves together and look for changes in the amplitude of the 29-minute. There was a hint in the TESS data that the height of the signal was related to the phase of the superhumps - which is odd.
2) Correlate the 29-minute optical signal with the Swift x-ray flux. We have a couple of Swift visits and several more planned during the fading.
3) In a few days, the superoutburst will fade quickly to about 16th mag. It will be hard to get good light curves for many, as it is faint and the time before V844 Her is too low to get a long time-series is short. But the 29-minute signal may be very strong at this point.
I think the good time to stop getting data is when people can't get an hour long of time-series any more. That is probably in a week or two.
Peter
Thanks for the goals…
Peter,
Thanks for the goals of this interesting project! I've been running about 3 hrs max deep into the high airmass and a clear filter. I figure that the timing of the 29 minute signal is just as important as the absolute photometry. I can now see the approx. 30 minute signals in the raw photometry light curve without any frequency analysis. This star is fascinating! Apparently there is the analog of a phase transition in the transparency, intensity, shape, ... of the accretion disk as the superoutbursts come and go.
Don (CDK)
All,
After a week of cloudy skies I was able to get a time series on V844 Her. The superhumps are weak and the 29-minute periodicity is clearly seen. It also faded by about 0.3 mag over two hours, so it looks to be ending the superoutburst. Within a day or so It should reach 16th mag and then begin a slow decline to quiescence. Once V844 Her returns to quiescence, the 29-minute signal is no longer detectable.
Thank you all for your observations! The archived light curve of this superoutburst is spectacular.
Peter
I have about 3 nights, 2 hrs each night, of data on V844 Her, but the internet service out here in the rural area I am at for this week is so slow I can't get the data submitted. It'll have to wait until next week when I am back in the city. Sorry.
Darrell Lee
LDRB
Peter
I have several observations scheduled for Sun and Monday. Are we beyond the time when they'd bring any value?
Gary
Gary,
Observations over the next several days will be useful. I think the 29 minute period may be the biggest signal now that V844 Her has declined to 16th mag. Looking at the data in the archive from last night there seems to be a very large amplitude of 0.3 mag. So if you can get an hour and a half or two, that would be great. 16th may be tough though.
I'm going to try on Sunday or Monday nights when it is supposed to clear off here.
Peter
All,
I got two hours on V844 Her last night...followed it way down into the haze. There were variations, but no sign of the 29-min oscillation. I think the system has pretty much returned to its quiescent state. No more time-series are needed. Thank you all!
Peter
I uploaded my data from last week today. I hope you find it useful.
Darrell Lee
LDRB