Transcient in Cygnus

Re: Transcient in Cygnus

Postby Paolo Berardi » Sun Jul 14, 2019 11:02 pm

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).

Image

Mag V ~ 9.51 during the observation.

Paolo
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Re: Transcient in Cygnus

Postby Forrest Sims » Mon Jul 15, 2019 7:05 am

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

Cheers
Woody
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TCP J21040470+4631129_20190715_231_Forrest Sims annotated.png
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Re: Transcient in Cygnus

Postby David Boyd » Mon Jul 15, 2019 8:53 am

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
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Re: Transcient in Cygnus

Postby David Boyd » Tue Jul 16, 2019 11:03 am

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
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Re: Transcient in Cygnus

Postby David Boyd » Wed Jul 17, 2019 11:18 am

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
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Re: Transcient in Cygnus

Postby Christian Buil » Wed Jul 17, 2019 4:40 pm

Here, use of a very small telescope for this type of target (see also http://www.spectro-aras.com/forum/viewtopic.php?f=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 :

Image

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Re: Transcient in Cygnus

Postby David Boyd » Fri Jul 19, 2019 9:04 am

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

tcpj21040470+4631129_20190713_928_D.Boyd.png
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Re: Transcient in Cygnus

Postby Paolo Berardi » Wed Jul 24, 2019 4:51 pm

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.

Image

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.

Image

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Re: Transcient in Cygnus

Postby David Boyd » Sun Jul 28, 2019 6:28 pm

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
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Re: Transcient in Cygnus

Postby Robin Leadbeater » Sun Jul 28, 2019 10:37 pm

Impressive stuff David (and Paolo) !
LHIRES III #29 ATIK314 ALPY 600/200 ATIK428 Star Analyser 100/200 C11 EQ6
http://www.threehillsobservatory.co.uk
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