Call for monitoring of AG Dra by R. Galis & al.

[Paolo Berardi]

Thanks for your comments! Very bad weather also here now...

Peter, it should be very useful to be able to compare my NIR spectra with yours (similar setup). I'd like to understand if I have rightly corrected the continuum crossed by a lot of telluric lines/bands.

I use a red filter (Wratten #25, 1,25" diameter) bolted on a barrel, simply inserted in the Lhires III entrance (just a short strip of tape to compensate for the slight diameters difference). My guide camera (SX Lodestar) is very sensitive to the red wavelengths, so there are no big problems for guiding on faint targets too. May be that it also works with an orange or yellow longpass filter. In order to improve the efficiency we should use a 800-1000 nm blazed grating (I'm using the standard one). I think this could be a good way to use the versatile Lhires III spectrograph.

Paolo

[Francois Teyssier]

AG Dra last night

The faint absorption in the blue adge of H alpha is increasing. Can be en affect of orbital motion

He II intensity is decreasing

François

[Francois Teyssier]

Comments by Jaroslav Merc:

I measured the equivalent widths of the selected emission spectral lines from these two spectra (April 26 and May 9).

These results confirms the significant decrease of EWs of He II (-15%) and O VI 6825 (-13%). There is a less prominent descrease of EWs of He I 6678 (-6%), O VI 7082 (-6%) and Hbeta (-4%). There is also a small increase of EW of Halpha (+2%).

I have also calculated the ratio of the equivalent widths of lines He II and Hbeta which can be a good proxy to the temperature of the white dwarf and this ratio decreased from 0.87 (about 183 000 K) to 0.76 (about 174 000 K). Next evolution of AG Dra could be very interesting.


So, more data are needed! (subject to weather)

François

[Christian Buil]

AG Dra Halpha aspect the 6.92/05/2017 (comparison with 14.03/04 observation) :



(the 6/05 spectrum is taken with VHIRES-MO at R=48000 and a 200 mm Newton diameter only telescope - but 2-hours exposure).

Christian

[Peter Somogyi]

Thanks Paolo for the advices, bought an orange#21 filter (Made in Taiwan - nothing else info just the #21 number - matches the 'Wratten' numbering), basically just confirms your result - no real difference. Of course, did a punch through test at the UV end and found just bias level (without refocusing to UV). It's been put between scope and LHires III (on top of the APM 2.67x barlow) for this time.

Taking a K1 III star '48 Dra', it is possible to speculate what else features may be existing (shifting it by 3.5A some absorptions matching well, including the CaII triplet):

asdb_agdra_20170510_925_vs_48dra.png (42.45 KiB) Viewed 8219 times

Just the O I 8446 emission line and few little outstanding features are there. The O I 7774 has been left off, maybe trying to fit the next time. Also note the signal is getting halved at the CaII triplet end, according to what the above graph's noise level suggests.

Peter

[Francois Teyssier]

IF the measures of AAVSO are correct, it happens something in the system

AGDra.PNG (4.91 KiB) Viewed 8193 times

New spectra during the next nights is strongly requested

François

[Francois Teyssier]

Alert, and confirmation, by Rudolf Galis

according photometric observations (from AAVSO and other observers), AG Dra increased its brightness about 0.3 mag in B filter during last tree nights, what looks like as an expected outburst. It should be confirmed in next night or two, I hope. Rudolf Galis

I hope that the sky will be clear for everyone during the next nights!
Dealy coverage is expected

François

[Olivier GARDE]

My spectrum of AG Dra taken last night shows a decrease in intensities on the lines as H Alpha, Raman OIV and HeI 6678, but at the same time, the global magnitude of this star increase about 0,3.

[Paolo Berardi]

Thank you for the alert reporting François.

Peter, sorry I missed your answer. Thanks a lot for your confirmation about the NIR spectrum.

Very interesting observation Olivier. Can you do an evaluation about the continuum? From AAVSO lc it seems that B-band had a greater impact.

Paolo

[Francois Teyssier]

A reprendre après vérification des spectres
Modification du message le 17/05/2017



François