Photometry and Spectroscopy of Flare Stars for TESS campaign

Affiliation
American Association of Variable Star Observers (AAVSO)
Mon, 08/22/2022 - 20:57

AAVSO Alert Notice 789 announces a campaign on 9 flare stars beginning immediately. Please see the notice for details and observing instructions.

The thread for this campaign is under the following forum:

- Campaigns and Observing Reports: https://www.aavso.org/flare-stars-tess-campaign-2022-2023

Please subscribe to this thread 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

Affiliation
American Association of Variable Star Observers (AAVSO)
About daily observations

Hello !!

I'm going to follow this campaign with V filter.

I would like to know how many daily observations are necessary for each star.

The AAVSO document seems to suggest that it should be an hour of observation for each. Please confirm.

Mario (MMAO)

Affiliation
American Association of Variable Star Observers (AAVSO)
Priority?

I was able to acquire a little over four hours on NSV 23386 last night with a J/C B filter at 90 seconds/exposure. In preparation I was able to get an SNR on the target of >190 with a 60 second exposure, but the comparison stars provided by AAVSO had a SNR <40. 

Which is more important to your campaign: a shorter cadence (<60 seconds) with low SNR comps. but maintaining >100 SNR on the target? Or a longer cadence (>=90 seconds) and higher SNR for comps? 

John Downing

DJCA

Affiliation
American Association of Variable Star Observers (AAVSO)
Correction

Further reading of the instructions in the alert notice have answered my question: "Set your exposure time based on SNR, and take images continuously, with no delay between exposures".  The information regarding whether or not to use two filters in the sequence was confusing to me.

As I only have one telescope I will be observing tonight in J/C V and B bands unless advised differently. Basing exposures on SNR >50 for the target should result in a shorter cadence. 

John Downing

DJCA

Affiliation
American Association of Variable Star Observers (AAVSO)
DSLR/Color CCD observations

I see in the alert notice that monochrome V band photometry is preferred to DSLR green. Is data transformed from TG to V useful for this campaign? I don't have a monochrome camera, but I have calibrated my system with one of the standard cluster fields and can contribute transformed V data

Affiliation
American Association of Variable Star Observers (AAVSO)
DSLR/Color observations

I think that de-Bayered TG photometry will be useful; and if you are shooting with a DSLR or color CCD, I suggest trying photometry reduction of the TB channel also.  Flares tend to be brighter in the blue than in yellow or red - see for example the flare on EV Lac on JD 2,459,838 that was observed in B- and V-band.  

Bob Buchheim

Affiliation
American Association of Variable Star Observers (AAVSO)
HIP 114066 Flare

Looks like I caught a flare on HIP 114066, from JD 2459851.66221 - 2459851.67304 the magnitude spiked...

10.626, 10.646, 10.639, 10.642, 10.529, 10.578, 10.585, 10.604, 10.603, 10.617, 10.620, 10.618, 10.624

This is the first I have seen from this target. :)

Darrell

Affiliation
American Association of Variable Star Observers (AAVSO)
Flare project Progress Report, and priorities for TESS Sector 57

Ref:  AAVSO Alert Notice789: Photometry and spectroscopy requested for 9 TESS targets

Thank you all for your participation in our flare star project!  Thirty people have contributed time-series photometry on one or more of our stars during TESS sectors 55-56, spanning longitudes from Europe/UK, to eastern North America and western North America.  Several of you have recorded flares (some small, some large) yielding a total of at least 25 flares that are visually apparent in the lightcurves.  Most of these were on EV Lac, but at least one on CR Dra, and a few on EQ Peg A.  Some of these flares were recorded with both photometry and spectroscopy, and several more in both B- and V-band photometry.  When we combine your observations with the TESS photometry, we will have a unique data set of multi-band and spectroscopic flare observations.

Those of you who concentrated on NSV 23386 and V383 Lac have seen your efforts rewarded with only “flat line” lightcurves.  Don’t be discouraged:  We expect to be able to use this data to place limits on the color and temperature of any small flares that TESS may have detected during your observations. This is something that wouldn't be possible without your data.  During TESS Sector 57 (which begins now) you can direct your attention to one of the more active stars.  To see what you might hope for, take a look at the AAVSO lightcurve of EV Lac on JD 2,459,838 where a nice flare was observed in both V-band (by Stephen Brincat) and B-band (by Ken Menzies).

TESS sector 56 comes to a close on September 30.  That means CR Dra and EQ Peg A fall off of the observing list, since they will no longer be in the TESS field of view.  Based on what we have seen from NSV 23386 and V383 Lac, they move to low priority.

For TESS Sector 57 (from September 30 through October 29), the priority #1 target is EV Lac, which has been a reliable flare producer.  Priority #2 is MCC 858 (aka HIP 114066), which is reported to have a flare rate nearly as high as EV Lac (one observable flare per 30-40 hours of observing).  Please adopt one of these stars and continue making long runs of time-series photometry and spectroscopy of these two through the end of October.

Good hunting!

Bob Buchheim (BHU)

Affiliation
American Association of Variable Star Observers (AAVSO)
Is it a flare ?

Hello everyone,
I think I caught a flare last night, but would like confirmation if possible.
Attach data of the moment of the increase in magnitude, the control star doesn't vary the magnitude in any time. I uploaded the observation to AAVSO.

EV LAC                              CONTROL: 000-BPL-016
HJD_UTC               MAG      +/-         MAG      +/-
----------------------------------  -------------------
2459857.37074      10.296    0.009      11.809    0.017
2459857.37158      10.301    0.009      11.810    0.017
2459857.37242      10.295    0.009      11.819    0.017
2459857.37326      10.288    0.009      11.808    0.017
2459857.37410      10.297    0.009      11.814    0.017
2459857.37493      10.296    0.009      11.808    0.017
2459857.37578      10.293    0.009      11.813    0.017
2459857.37661      10.298    0.009      11.813    0.017
2459857.37746      10.214    0.008      11.812    0.017
2459857.37829      10.267    0.008      11.809    0.017
2459857.37913      10.281    0.008      11.807    0.017
2459857.37997      10.280    0.008      11.808    0.017
2459857.38081      10.279    0.008      11.812    0.017
2459857.38165      10.278    0.009      11.810    0.017
2459857.38249      10.279    0.009      11.808    0.017
2459857.38332      10.280    0.009      11.811    0.017
2459857.38417      10.282    0.009      11.807    0.017
2459857.38500      10.279    0.009      11.800    0.017
2459857.38585      10.282    0.009      11.806    0.017
2459857.38668      10.278    0.009      11.806    0.017

Affiliation
American Association of Variable Star Observers (AAVSO)
V-band flare candidate

Hi, nekkar (Mario?):  The graph certainly looks real.  It is interesting how your flare fades promptly (~3 minutes after peak), but then stabilizes for quite a while, and doesn't reach the pre-flare brightness until about 20 minutes after the peak.  

Since the flares occur randomly (as far as we can tell), timing -- and luck -- play into the flare star project.  Stephen Brincat was on EV Lac (in B-band) for much of the night, but had to stop just 5 minutes before your flare flashed.

Cheers,

Bob Buchheim  

Affiliation
American Association of Variable Star Observers (AAVSO)
Flare candidate

Dear Bob,
Thank you very much for your quick response.
It made me very happy that you think it's a flare.
I did 135 exposures at 70" with an Astrodon V photometric filter, and the table I've shown is a reduction. I've enlarged it a bit so you can see that the stabilization at magnitude 10,290 occurred much later.
It is a pity that it isn't possible upload graphs here, because it is curious to see the stability of the observations and suddenly a notable jump.
My best wishes to you and the rest of the observers.

Mario Morales Aimar (MMAO)

2459857.36907      10.298    0.009      11.808    0.017
2459857.36990      10.289    0.009      11.803    0.017
2459857.37074      10.296    0.009      11.809    0.017
2459857.37158      10.301    0.009      11.810    0.017
2459857.37242      10.295    0.009      11.819    0.017
2459857.37326      10.288    0.009      11.808    0.017
2459857.37410      10.297    0.009      11.814    0.017
2459857.37493      10.296    0.009      11.808    0.017
2459857.37578      10.293    0.009      11.813    0.017
2459857.37661      10.298    0.009      11.813    0.017
2459857.37746      10.214    0.008      11.812    0.017
2459857.37829      10.267    0.008      11.809    0.017
2459857.37913      10.281    0.008      11.807    0.017
2459857.37997      10.280    0.008      11.808    0.017
2459857.38081      10.279    0.008      11.812    0.017
2459857.38165      10.278    0.009      11.810    0.017
2459857.38249      10.279    0.009      11.808    0.017
2459857.38332      10.280    0.009      11.811    0.017
2459857.38417      10.282    0.009      11.807    0.017
2459857.38500      10.279    0.009      11.800    0.017
2459857.38585      10.282    0.009      11.806    0.017
2459857.38668      10.278    0.009      11.806    0.017
2459857.38753      10.289    0.009      11.815    0.017
2459857.38836      10.281    0.009      11.813    0.017
2459857.38919      10.290    0.009      11.816    0.017
2459857.39004      10.285    0.009      11.811    0.017
2459857.39087      10.290    0.009      11.812    0.017
2459857.39172      10.288    0.009      11.813    0.017
2459857.39255      10.292    0.009      11.816    0.017
2459857.39339      10.289    0.009      11.810    0.017
2459857.39423      10.286    0.009      11.816    0.017
2459857.39507      10.292    0.009      11.816    0.017
2459857.39591      10.294    0.009      11.812    0.017
2459857.39675      10.284    0.009      11.813    0.017
2459857.39760      10.295    0.009      11.811    0.017

Affiliation
American Association of Variable Star Observers (AAVSO)
EV Lac Oscillations

Hi All,

I did a full night's time series on EV Lac last night (North America) in V filter, and it seems from the data, that I didn't see any flares, but the star was oscillating a quite a bit. Made a nice sine-like wave and then by the end of the night settled out into a straight line, which has been more the norm for this star, at least that I have seen so far. It looks like Charles Cynamon caught part of this behavior in B filter as well.  Of course, the clouds are moving in on me now. Anybody have any idea of the cause of this oscillating behavior?

 

Darrell

Affiliation
American Association of Variable Star Observers (AAVSO)
JD 2459863 EV Lac

Hi Darrell:

Note that your lightcurve from this night is noticeably brighter that the preceding V-band nights; and that Charles Cynamon's B-band is similarly much brighter than the preceding B-band nights

It appears that there was a monster flare, that started sometime before JD 0.3 and was fading for the next 8-12 hours.  David Boyd was on EV Lac starting at about JD 0.3, and the star was very bright at that time (Bmag ~ 9.8), and faded over his next ~6 hrs of observation (he missed the peak -- the flare apparently began before he started observing).  It was still much brighter than the star's normal quiescent state at the end of David's observing run.  Charles Cynamon's B-band lightcurve started about JD 0.7, with the star still abnormally bright (but fading).  You and he probably both observed the continued decline of this monster flare.  On David's lightcurve (not yet posted to AAVSO), there are a series of smaller flares during the decay.  You are probably seeing a continuation of that phenomenon.

When we get the TESS photometry of this night (in a few months) and combine it with any other spectroscopy observations, this flare is likely to generate some very interesting analyses.

Bob B.

Affiliation
British Astronomical Association, Variable Star Section (BAA-VSS)
JD 2459863 EV Lac

I think I might have got a few hours of this decline in B Band. Starting later than David's with a peak magnitude of about 10.3 amd a minimum around 11.6 with smaller flares taking place during the decline. I posted mine a few hours ago.

 

Tony 

Affiliation
American Association of Variable Star Observers (AAVSO)
Oscillations?

Sorry if these questions are dumb.

I can certainly understand why the spikes in luminosity are caused by flares. But what are the "down side" of the sine-like wave caused by? Is the star pulsating, the actual "surface" growing and then shrinking? Is the whole star sort of ringing like a bell from the shock of the monster flare?

 

Darrell 

Could you post a link to a…

Could you post a link to a graph (maybe upload the graph to google drive if there's not some other better way)?

https://academic.oup.com/mnras/article/482/4/5553/5224549

The paper I linked above, and some of the references in it, discuss quasi-periodicities in stellar flares.

One thing to be careful about is that it's really easy to "detect" fake periods in short segments of data.  By short I mean short compared to the period.  If there is just sporadic variability, it's common for it to look like there is a period with about 3-5 cycles of the period detected.  Astronomers call this "red noise", and this article addresses the problem nicely:

https://articles.adsabs.harvard.edu/pdf/1978ComAp...7..103P

So if you have only a few cycles of the apparent sinusoid, it's probably just that there are many correlated flares going off in a way that makes it look like there's a period.  If you have a dozen cycles of the period, it's probably real.  There are a lot of papers in literature reporting spurious periods because people don't understand this.

 

 

 

Affiliation
American Association of Variable Star Observers (AAVSO)
TESS In Safe Mode

Oh man. TESS Went into safe mode on Oct. 10th. Guess it missed the big flare on the 11th. Bummer.

Should this effort continue?

 

Darrell

Affiliation
American Association of Variable Star Observers (AAVSO)
Continue observing ...

Hi, Darrell:  Yes, a bit of a bummer, but hopefully short-lived.  Meanwhile, ground-based observations in photometry (one or two filters) plus spectroscopy provide a wonderful data set for analysis of any flares detected, even absent TESS photometry.  So, I'd say "keep observing" while we await a return of TESS coverage.

Cheers,

Bob B.

Affiliation
American Association of Variable Star Observers (AAVSO)
New EV Lac flare

Hello !!

I have uploaded to AAVSO an observation from last night (2022-10-14) where a flare can be seen in EV Lac, but it had already started when I started the observation.
Is there a site where I  can see the confirmation of flares?

Cheers

Mario

Image removed.

Affiliation
American Association of Variable Star Observers (AAVSO)
TESS Sector 58 has begun -- new target priority

[I am a bit late at posting this note from Dr. James Jackman to the AAVSO forum – Bob B.]

TESS sector 58 began on Oct 29. Sadly, TESS will move on from our old favourite EV Lac to observe MCC 858 (= HIP 114066) and HD 160934. A quick check reveals that HD 160934 is visible to TESS for a long duration, so has been included in multiple sectors. However, it is currently not very visible from the ground. Therefore, those who wish to keep conducting observations simultaneously with TESS will want to focus on MCC 858.

On this note - I want to mention that the next two sectors are focused on earlier type stars. As we know from MCC 858, we likely won't be observing the whoppers we've seen from EV Lac recently. This is due in part to the change in contrast between the flare spectrum (a blue event) and the quiescent star in a given filter. Earlier type stars have bluer quiescent spectra than later type stars, meaning that for a flare of a given energy the contrast will be reduced. Although, a quick search of the AAVSO B band lightcurve for MCC 858 shows at least 6 flare candidates and signs of rotational modulation that will be fascinating to compare to the TESS data (to tease out star spot temperatures for this young star). 

However, these stars will really show what we can do. Plus, any event that is detected in TESS but not in ground-based data is still useful. Photometry will be used to measure upper limits on flare temperatures. This will be especially useful for these earlier type stars, as we currently don't know how often K and early M stars have flares with temperatures of 15,000, 20,000 and even up to 40,000K. Upper limits will give us some of this information and tell us how much ultraviolet emission these flares throw out. Spectroscopy will tell us the relative energies emitted in specific lines, informing future flare models and energy budgets. As above as well, multi-colour photometry and spectroscopy of the quiescent stars will also be interesting to study how variable they are outside of flaring, and to try and measure star spot temperatures.