AAVSO: American Association of Variable Star Observers

Proposal #188

Proposer (43151) Stewart Bean (sjbeanmail@aol.com) obscode: BENS
Assigned To(3663) Dirk Terrell
Date SubmittedFeb. 3, 2021

Multi color photometry of VW HYI through a superoutburst.

The last three superoutbursts have been separated by 163 days judged by folding the TESS lightcurves. This then predicts the next
superoutburst to start on JD 2459252 - which February 6th.

Hambsch F, J (AAVSO) took measurements in B and V for the paper "Modelling hystereses observed during dwarf-nova outbursts"
J.-M. Hameury, C. Knigge, J.-P. Lasota, F.-J. Hambsch and R. James, Astronomy & Astrophysics March 9, 2020 that covered two normal outbursts but not a superoutburst. See their data around JD 2458400.

In "Testing the disk instability model of cataclysmic variables" Guillaume Dubus et al A&A 617, A26 (2018) modelled a generic Dwarf Nova in superoutburst in the filters UBVRI in their Figure 1. Although this is not directly for VW HYI the model could be applied to VW HYI if required.

I have used the itel T30 scope to obtain the magnitudes for the BVRI filters recently - now in the AAVSO database.

VW HYI has a quiescence value of 14 mag for the V filter rising to 8 or 9 mag at the peak of outburst. This means a factor of 100 in brightness change though the superoutburst.

To measure VW Hyi in UBVRI though the next superoutburst.
Start: Asap
Finish. After the superoutburst on return to mag 14
Cadence: Daily.
Field is uncrowded, AAVSO sequence is available, works well but the U comp star values are not available at this time.


Stewart Bean (BENS)

Target RA (H.HH) Dec (D.DD) Magnitude Telescope Observation Frequency Expiration Date Proprietary Term
VW Hyi 4.153133 -71.29483 14.0–8.0 BSM_Berry Aug. 4, 2021 No


(4726) Kenneth Menzies — Feb. 5, 2021, 6:48 p.m.

Committed to Berry

(43151) Stewart Bean — Feb. 7, 2021, 9:02 a.m.


(43151) Stewart Bean — Feb. 8, 2021, 2:07 p.m.

VW Hyi now in outburst at V mag 9.3. on 8 Feb 2021 using itel T30.

(43151) Stewart Bean — Feb. 11, 2021, 1:41 p.m.

Based upon results from itel T30 the exposure ratios for the various filters are approx:
U 100
B 10
V 10
R 20
I 20

(43151) Stewart Bean — Feb. 13, 2021, 9:13 a.m.

Ken, Is all OK with Berry?

(43151) Stewart Bean — March 27, 2021, 4:43 p.m.

Hi, I have images now from BSM Berry 2. Thanks.

Point 1. 30 s exposure seems to be fine for even the quiescent stae so: No need for 60 s, 120 s or 180 s images for all filters.

Point 2. Vphot does not seem to recognise the filter "SR". Is this the Rc filter? If so how do I get Vphot to process it.

Thanks again ,

(43151) Stewart Bean — April 6, 2021, 4:39 p.m.

I have analysed the data so far and have noticed that the 30 second exposures are nearing saturation during a normal outburst. They will saturate when in superoutburst.

Request: Can the all the short exposures (30 s for I, SR, V and 60 s for B) be all reduced to 10 sec please.

All of the 120 s and 180 s exposures can remain as they are fine for the quiescent state.

(4726) Kenneth Menzies — April 7, 2021, 10:24 p.m.

Short exposures reduced.

You can rename SR filter to R. The transform coefficients take the SR filter into account and report magnitude as Cousins R (assuming you transform this data?).

(43151) Stewart Bean — April 10, 2021, 7:24 p.m.

I have renamed one set to R. Running Vphot I do get a reasonable looking result, but I have not "transformed" the data.

Can you explain the transform step please?


(4726) Kenneth Menzies — April 11, 2021, 2:43 p.m.

You should really ONLY report the SR filter mag IF you transform the SR filter image WITH a second or more filters. Do you see either the two color transform link or transformapplier link in VPhot? Try the two color transform first because it should be quite obvious what to do? TransformApplier takes a little more effort to explain. We should talk by email (kenmenstar@gmail.com) if necessary. There is some guidance in the VPhot forum.

The SR image gives a reasonable R magnitude only because the SR bandpass is similar (not identical) to the R bandpass.


(43151) Stewart Bean — April 19, 2021, 7:40 a.m.

The most recent images from Berry did not include the long exposure set. These give good S/N when VW Hyi is in quiescence.

Both short and long exposures are need for VW Hyi owing to its large dynamic range.


(43151) Stewart Bean — April 19, 2021, 1:05 p.m.

Today I did receive both long and short exposures . So all OK.

(43151) Stewart Bean — Feb. 10, 2022, 4:37 p.m.

VW Hyi is now in outburst at magnitude 9. The strategy of having both short and long exposures has worked. The short exposures avoid saturation in outburst. The longer exposures record the quiescent state well enough. However, I note that the total time allocated to this project is about one hour. I think that stacked 10 s exposures, for all filters, would be more efficient and work fine:

V 15x 300s in total including ~10s download from camera.
B 15x 300s "
I 15 x 300s
SR 15x 300s.

So the total time used for this project would be approx 1200 s which is about 3x less than at present.



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