Transcient in Cygnus

[Paolo Berardi]

Hi all,

Robin, thanks for the very interesting paper. Last spectrum for 14.858/07/2019. Lhires III and 1200 l/mm grating (R ~6000).



Mag V ~ 9.51 during the observation.

Paolo

[Forrest Sims]

And my contribution on TCP J21040470+4631129 taken with my LISA late evening 2019-07-14.

Cheers
Woody

[David Boyd]

This shows the change in the spectrum of the dwarf nova over 24 hrs as its V mag faded from 9.14 to 9.52, a flux reduction of 30%. The B-V colour index was unchanged at -0.22.

tcpj21040470+4631129_20190713_928_D.Boyd.png (37.91 KiB) Viewed 12624 times

David

[David Boyd]

Another spectrum 24 hrs later shows a further reduction in the continuum flux level. The V mag used to flux calibrate the spectrum is now 9.76. Assuming the continuum flux at this stage is primarily from the accretion disc, the auto-planck function in Vspec gives a disc temperature around 30,000K which is reducing slowly.

tcpj21040470+4631129_20190713_928_D.Boyd.png (45.74 KiB) Viewed 12588 times

David

[David Boyd]

The continuing good weather has enabled me to get one more spectrum showing a further reduction in flux, now at magnitude V=9.92, and the colour index is becoming slightly less blue at B-V=-0.19.

tcpj21040470+4631129_20190713_928_D.Boyd.png (46.42 KiB) Viewed 12567 times

David

[Christian Buil]

Here, use of a very small telescope for this type of target (see also http://www.spectro-aras.com/forum/viewt ... =45&t=2358), a Maksutov 127 mm Sky Watcher + UVEX for a resolution power of R=1200 at 550 (R=1400 at 656 nm) for cover all the visual spectral domain (+ the beginning of UV). Date 15.9/07/2019 :



Christian

[David Boyd]

The gradual fading continues. Emission lines are weaker or have disappeared. V mag now 10.36.

tcpj21040470+4631129_20190713_928_D.Boyd.png (52.6 KiB) Viewed 12504 times

David

[Paolo Berardi]

Hi all,

my last attempt to a time-resolved spectroscopy for July 23 (16 x 600 s). The DN has reached V mag 11 yesterday.



Each profile was wavelength calibrated using the Ar-Ne lamp frames taken before and after each target frame (averaged) to reduce the harmful effects of the spectrograph mechanical flexures.

Below the concurrent V photometry obtained with a small telescope mounted parallel to the C9.25. On top, the colored bars represent the 16 x 600 sec frames timeline.



Paolo

[David Boyd]

Time resolved spectroscopy of the dwarf nova with a LISA spectrograph at R~1000 on 5 nights between 13 and 18th July provided 73 spectra, each a 300 sec integration. Each session lasted about 1.6 hrs, longer than the binary orbital period. SNR per spectrum fell from ~100 at V=9.1 to ~50 at V=10.4. Each spectrum was cross correlated with respect to the first spectrum taken each night to find their relative radial velocities. Period analysis of these relative radial velocities gave three strong signals with frequencies separated by the expected 1 c/d aliases. One of these periods, 0.05335 ± 0.00017 d, agreed with the orbital period derived from photometry. Phasing the RV data on this period gave the following phased RV plot. The rms residual to a fitted sine function (assuming the orbit is circular) is 6.5 km/s.

TCP J21040470+4631129 Relative RV plot 13-18 July.png (16.76 KiB) Viewed 12340 times

David

[Robin Leadbeater]

Impressive stuff David (and Paolo) !