Nova in Centaurus TCP J14250600-5845360

[Terry Bohlsen]

Dear All
I have just received a LISA spectrograph and gave it its fitst light last night. I have only used a L200 spectrograph before but the weather has been to terrible over the last 6 months to use it.
A new transient was discovered in Centaurus last month but it hasn't been confirmed as a nova yet. I have been taking photometry of it but thought that it would make a good first light target for my new LISA. It is currently about mag V =11.5 but much brighter in R and I (R = 9.9 and I = 8.6).
I am using a vixen VC200L with a focal reducer and a ST8XME camera.
There are lots of lines in the spectrum but apart from Ha I'm not sure what the others are. I processed the images (5x 300secs) with LISA.
It this a spectrum typical of a nova?

Cheers

Terry Bohlsen
Armidale NSW

[Francois Teyssier]

Hi Terry,

Good shot for a first night !

Effectively (and strangely), it seems it's the first spêctrum of this bright transcient

http://www.cbat.eps.harvard.edu/unconf/ ... 45360.html

The spectrum could be a Fe Nova (narrow lines, often P Cygni profiles, Fe II lines are the most proeminent lines after the Balmer lines)

See : http://www.astronomie-amateur.fr/Projet ... Novae.html

Your graph is not easy to read because of the atypical tic of 1100 anströms. It should better to use 1000 or 500.

The spectral calibration looks erroneous (Ha line at 6590). Which soft did you use for calibration ? And what is the resolution ?


Could you send us a link to the dat or fit file ?


Best regards, and welcome among LISA observers ring !

François Teyssier

[Terry Bohlsen]

Thanks Francios
I used Isis for calibration. I think it is OK. Ha line measures at 6563 but it has a bifid top. Sorry about the strange axis label. It is just a screen capture from Spc Audace and this is the labels it put on it.
I have added a differnt one below from VSpec. I'm not certain of the resolution. I am very new at using Isis but the log file generated gave this info "Pouvoir de résolution : 645.3"
I will try to attach the .dat file as well.
Here is a different scren capture.

[Terry Bohlsen]

The dat file doesn't seem to attach so I have uploaded it to here
http://users.northnet.com.au/~bohlsen/A ... 20_580.dat

Cheers

Terry

[Francois Teyssier]

Hi Terry,

The general appearance is that of a nova Fe :
The most intense lines (after Balmer lines) are those of Fe (noticelly the multiplet 42 : 4924, 5018, 5069 and also those of 49 and 74 multiplet)
[OI] 7773 is proeminent ; it's generally the fist forbidden line to appear in Fe Nova

But :
- the forbidden lines are unusually broad for a Fe nova
- the Balmer and [OI] lines show a double peak
These features are typical of a He/N nova

So the nova should be a -unusual- Hybrid nova, i.e. a Fe nova which evolves rapidly to a He/N nova.
I note that it's a fast (or even very fast nova) with T3 ~ 15 days.
This is unusual for Fe novae (slow novae), but typical for He/N or hybrid nova

Before definitively concluding, you have to verify your spectrum (a bad focalisation of the star on the slit could show the same features : wide and double-peaked lines).
Is the spectrum narrow (about 5 pixels) ?

All the best

François Teyssier

[Christian Buil]

Hi Terry,

Congratulation for this first light (a nova!). A great shot !

Your spectrum look very well (thin and uniform spectral trace on your 2D image).
Also, the spectral calibration seem correct (but for a final verification take some spectra of cold star (F-G-K type)
for control the quality of spectral focus dependance and calibration - take care with a ST8 large CCD,
and also publish a neon lamp spectrum).

The examination of your 2D spectrum

http://i566.photobucket.com/albums/ss10 ... cenNo2.jpg

show possible cosmic rays impacts at the position of your 4323 and 4403 A features. Check by processing
only one or two images of your sequence. And also, follow François Teyssier recommandation: track
the time evolution of this existing star. Point also your telescope in the direction of Nova Oph, and more

A presence of spectroscopist southern observer is a real pleasure and sartisfactions

Christian Buil

[Francois Teyssier]

Hi Terry,

Your spectrum is very nice. The broad lines (for a Fe nova) are confirmed.

Here's a lines identification.

nova.png (10.52 KiB) Viewed 15845 times

It should be very interesting to get a new spectrum in the next days in order to confirm the evolution from Fe to He/N nova.

Best regards

François Teyssier

[Terry Bohlsen]

Hi Terry,

Congratulation for this first light (a nova!). A great shot !

Your spectrum look very well (thin and uniform spectral trace on your 2D image).
Also, the spectral calibration seem correct (but for a final verification take some spectra of cold star (F-G-K type)
for control the quality of spectral focus dependance and calibration - take care with a ST8 large CCD,
and also publish a neon lamp spectrum).

The examination of your 2D spectrum

http://i566.photobucket.com/albums/ss10 ... cenNo2.jpg

show possible cosmic rays impacts at the position of your 4323 and 4403 A features. Check by processing
only one or two images of your sequence. And also, follow François Teyssier recommandation: track
the time evolution of this existing star. Point also your telescope in the direction of Nova Oph, and more

A presence of spectroscopist southern observer is a real pleasure and sartisfactions

Christian Buil

Dear Christian
Thanks for the encouragement. You are correct about the cosmic ray hits. They are on 2 of the frames and are responsible for spikes you mention. I processed the remaining 3 frames and the spikes are not present. This however created more noise in the rest of the spectrum due to the loss of 2/5ths of the exposure. May be best just to delete the area of the spectrum.
How do I use a cold star to check the calibration?
I have taken images of A and B stars with H lines before but not F G K stars.

Cheers

Terry

[Terry Bohlsen]

Hi Terry,

Your spectrum is very nice. The broad lines (for a Fe nova) are confirmed.

Here's a lines identification.

nova.png

It should be very interesting to get a new spectrum in the next days in order to confirm the evolution from Fe to He/N nova.

Best regards

François Teyssier

Dear Francois
This is great. Thanks.
Sadly it is raining at present and will for another day or so. Hopefully I can take another spectra then.

[Terry Bohlsen]

I was able to take further spectra of this suspected nova lsat night. I took 11 x 300 sec exposures and have processed them in Isis. The result is almost identical to the previous spectra but with less depth to the notch in the Ha spectra.
The fit file is here
http://users.northnet.com.au/~bohlsen/A ... 24_444.fit
The spectra is below


How can this info be reported?