V442 And Be star in outburst

[Olivier Thizy]

Hello all,


My call for observation of V442 Andromedae was well received and thanks to several of you, at least one spectrum has been taken every night and most of the time several per night!

So here is as of september 4th the daily Halpha evolution since the outburst discovery on the night of august 21st:

V442 daily evolution aug21-sep3.JPG (130.31 KiB) Viewed 17028 times

The changes seem less pronounced for the past three nights but additional observations are required to confirm or not (again, my weather forecast are not great for next few nights). Note that no period has been searched/calculated yet as my focus is on data acquisition so far.

Last but not least spectra should of course be uploaded on BeSS database for further/detailed study.


Let's continue to observe this outburst with as much frequent spectra as possible,

Cordialement,
Olivier

[Christian Buil]

A VHIRES-MO spectrum of V442 And taken the 2.9/09/2017 at R=50 000 with a C9.25 telescope, and for the first for me,
by using a CMOS camera (ASI1600MM-C) on an echelle spectrograph. Detail of Halpha line and the full spectrum taken with VHIRES-MO.

Christian B

[Olivier Thizy]

Hello,


V442 And was in a more stable state for the past few days but - thanks to Joan Guarro Flo latest observations - there seems to be again some activity going on. Here are the daily graphs (one selected graph per night). The two graphs at the top are the one from Joan Guarro showing the double peak evolution again:

V442 And daily evolution

V442 daily evolution aug21-sep8.png (80.74 KiB) Viewed 16979 times

Based on Coralie Neiner suggestion, I measured V/R and V+R for all the spectra I have a copy of. I used MatLab with gaussian fit on two spectral domains; I did not model/remove the absorption so I guess this is a first "draft".

The V/R is showing an evolution (periodic? same period as the star around 2.6 days?) for approximately 10 days after the outburst discovery, then a more stable ratio, and now is back to variability again. It looks like the ejected material initially had the star momentum (and rotational period) then as it moved away it moved into a more Keplerian rotational behaviour (and different period); and more recently another ejection of material?

V/R

V442And V_R evolution aug21-sep8.png (13.35 KiB) Viewed 16979 times

At the same time, V+R is showing a smooth increase then a stabilization for the past few days. This tends to indicte that the V/R variation above are mainly due to material around the star NOT homogeneous:

V+R

V442And V-plus-R evolution aug21-sep8.png (11.33 KiB) Viewed 16979 times

Bottom line is that this is a very interesting Be star outburst and I encourage you to continue observing it. As usual, upload your spectra on BeSS but please send me a copy so I can update the data/graphs accordingly.

Cordialement,
Olivier Thizy

[Olivier Thizy]

Hello,


Thanks to Dong Li & Patrick Fosanelli recent observations, there is confirmation of the activity of V442 And after a short "quiet" period with Halpha emission showing variability, V/R variable again while V+R seems to remain more stable:

V442 daily evolution aug21-sep.JPG (138.95 KiB) Viewed 16938 times

V442And V_R evolution aug21-sep11.JPG (43.07 KiB) Viewed 16938 times

V442And V-plus-R evolution aug21-sep11.JPG (45.97 KiB) Viewed 16938 times

I folded V/R over the 2.615 days period; here is the result:

V442And V_R phased evolution aug21-sep11.JPG (40.86 KiB) Viewed 16938 times

Last but not least, I measured He I 6678 center and plotted it against the 2.615 days period:

V442And HeI6678 phased evolution aug21-sep11.JPG (37.46 KiB) Viewed 16938 times

Cordialement,
Olivier

[Olivier GARDE]

evolution of V442 And in 5 days

[Olivier Thizy]

Hello all,


Here is a quick status on V442 Andromedae Be star outburst since august 21st. The V+R graph is now showing a clear decrease:

V442And V-plus-R evolution aug21-sep15.JPG (31.38 KiB) Viewed 16898 times

The V/R graph is showing some variability but slower than the 2.6 days periodic variations that were clearly visible at the beginning of this emission phase:

V442And V_R evolution aug21-sep15.JPG (31.93 KiB) Viewed 16898 times

Here are the data folded over the 2.6 days (star rotation) period:

V442And V_R phased evolution aug21-sep15.JPG (31.56 KiB) Viewed 16898 times

Here is the updated daily specra graph:

V442 daily evolution aug21-sep15.JPG (150.23 KiB) Viewed 16898 times

Last but not least, I looked into BeSS archive were several emission phase have been recorded. I tried this view with a down arrow when no emission and a up arrow when emission is visible with size depending on the intensity of the line(s). From this graph, it looks like active (emission) phase last between 3 to 6 months while quiescence (no emission) phase last between 6 to ~21 months:

V442And_BeSS-history.png (34.87 KiB) Viewed 16898 times

This type of graph shows the importance of the BeSS Be star monitoring that started about ten days ago. Long term monitoring is giving us some statistics on the outburst events. And current short term regular monitoring - thanks to all the active observers involved with V442 And current outburst follow up - is giving some details on the outburst mechanism...


And for the fun, I have been working on remote observation. I observed last night from home... with fireplace heat and Star Trek Voyager serie on TV!

Remote_obs.jpg (61.77 KiB) Viewed 16896 times

Hre is a capture of last night observing session where the spectrum signal has been increasing as the target as rising up in the sly (and I suspect the sky transparency was getting better too):

Keep observing V442 And - and clear skies to all,

Cordialement,
Olivier

[Christian Buil]

V442 And spectrum taken the 12.939/09/2017 by using a modified VHIRES-MO (ASI1600MM-C detector):



Christian

[Olivier Thizy]

Hello,


V442 And is still very active, 30 days after the discovery of its outburst. There is a strong interest from Noël Richardson (university of Toledo) for our data. They have done some observation of their own and he is encouraging us to continue observing: "this seems like a rare opportunity to trace the mechanisms of how small ejections in Be stars operate to build a disk. Please keep observing!"


Here is the V/R graph showing variations. Note also a very good time coverage during last two days with Dong Li & I.

V442And V_R evolution aug21-sep20.JPG (34.05 KiB) Viewed 16829 times

There are now 95 spectra from 8 observers - any more high resolution (R>10000) observers to join the "party"?:

Capture.JPG (27.19 KiB) Viewed 16829 times

The V+R continues its decrease and it would be very interesting to see the future evolution:

V442And V-plus-R evolution aug21-sep20.JPG (33.31 KiB) Viewed 16829 times

And here is the updated daily graph evolution:

V442 daily evolution aug21-sep20.JPG (163.88 KiB) Viewed 16829 times

In summary: outburs is still in progress and Halpha emission line(s) continues to evolve over time. So it is a good time to observe, specially with R>10000 spectrographs. If you would like to observe, just follow BeSS procedure & standards, upload your spectra on the database and please send me a copy so I can update the graph with your data...

BeSS: http://basebe.obspm.fr/basebe/


Cordialement,
Olivier

[Olivier GARDE]

Last change in V442 And spectrum

[Olivier Thizy]

Hello,


128 spectra of V442 And (hd6226) have been collected since the outburst discovery on the night of augst 21st [still waiting for more observers to join in... ], for a total exposure time of 135 hours:

V442And Observers.JPG (26.14 KiB) Viewed 16741 times

I have a mea culpa to make - I did a mistake in the V & R calculation. Basically, I wanted to remove 0.9 on each measurements in order to compensate for the absorption line (until I find a way to model it); well I added the 0.9 instead. Here are the corrected data. They show very similar information, but more accurately!

The emission increased but is now in the decline as the V+R graph shows:

V442And V-plus-R evolution aug21-sep27.png (14.79 KiB) Viewed 16741 times

The V/R is still showing variability. I grouped in blue the variable phases, in green the more stable ones:

V442And V_R evolution aug21-sep27.png (23.72 KiB) Viewed 16741 times

A period analysis shows a period of 2.6852 days:

V442And V_R phased evolution aug21-sep27.png (31.69 KiB) Viewed 16741 times

This is very close to the period found on HeI 6678 stellar photospheric line, ie the star rotation itself:

V442And HeI6678 phased evolution aug21-sep27.png (23.96 KiB) Viewed 16741 times

The Halpha daily graph shows the evolution over time:

V442And daily Halpha evolution aug21-sep27.JPG (185.52 KiB) Viewed 16741 times

The Hbeta emission is now almost gone:

V442And daily Hbeta evolution aug21-sep27.JPG (169.63 KiB) Viewed 16741 times

More study should come out of those observations. This is clearly an excellent opportunity to study such small ejecta outburst. The emission should last for several weeks (couple of months?) so please keep observing. A SNR of 100 is prefered if you can. Of course, spectra should be uploaded in BeSS for archive and future study. Please send a copy to me (thizy@free.fr) so I can add it in this analysis.

Cordialement,
Olivier