Forum Replies Created
-
Posts
-
There is an absolutely stunning high resolution echelle spectrum covering 3750-9300A in the BAA database from Joan Guarro Flo taken 20210809.838 using an amateur designed (by Tim Lester) home built remotely operated instrument. (zoom in to view the narrow P Cygni lines from the stellar wind superimposed on the broad nova ejecta lines) An impressive example of the progress in amateur spectroscopy since the last outburst.
Cheers
Robin
“The narrow unshifted feature comes from the circumsystem material from previous outbursts”
Correction that should be ….from interaction with the relatively slow moving red giant wind. This looks a good reference for the evolution of the optical spectrum in the 2006 outburst
https://academic.oup.com/mnras/article/474/3/4211/4768437
Robin
This is only the start! (The narrow unshifted feature comes from the circumsystem material from previous outbursts). If it follows earlier outburst there is lots more strangeness to come. Watch for highly ionised coronal lines (like [Fe X, XI, XIV] and [A X] etc) produced as the shock heats the gas to 1 million K plus. There is an interesting account of taking spectra early in the 1958 outburst by George Wallerstein in the 2005 S&T article.
Robin
A series of spectra from 2006 taken using a Star Analyser.
http://www.threehillsobservatory.co.uk/astro/spectra_24.htm
I expect there will be many more spectra this time
Cheers
Robin
I was thinking I might offset some of the cost (~0.3%) by applying for a Ridley grant but unfortunately I see the conditions specifically exclude travel expenses.
Robin
Sounds it is a common issue eg
https://www.cloudynights.com/topic/600195-vixen-porta-ii-slow-mo-knob-fix-for-some/
If the shaft is the same diameter, swap them out for something like these perhaps?
EDIT: from the one review on there it seems it is indeed a good solution for the porta mount
https://www.rothervalleyoptics.co.uk/skywatcher-slow-motion-cable-set.htm
(other retailers are available)
Cheers
Robin
After a brief plateau of a few days the brightness started dropping rapidly last night and the emission in the core of the Balmer absorption lines has increased.
Robin
Again excellent agreement with mine ~2 hrs later (using a different MILES reference star HD192640) though the the blueward absorption in the H alpha line is not resolved in the R 500 ALPY spectrum
Robin
Significantly fainter in the spectrograph guider tonight and the spectrum has changed completely once again with a host of strong broad emission lines appearing.
Robin
The H alpha emission line has weakened further and is now showing a P Cygni profile (velocity ~600km/s). The rest of the spectrum now resembles that of a G/K star photosphere but with some additional absorption lines, particularly in the red at ~7106/7766 A (The other features in that area are Tellurics)
Cheers
Robin
The spectrum has changed significantly in the past few days. Except for a relatively weak narrow H alpha emission, all the other lines previously in emission are now either missing or in net absorption.
Cheers
Robin
Hi Nick,
I guess that is Nova Vul 2021 not 2001. Is that from Dan Green ? I wondered why he was asking about my instrumentation this afternoon. He must have posted it before I replied
Cheers
Robin
The evolution to an Fe II type nova as I highlighted in my spectrum from 24th July has now been confirmed
https://www.astronomerstelegram.org/?read=14816
Cheers
Robin
“As an engineer the FITS standard is pretty much the kind of thing that I would expect a scientist to write…”
As someone who spent a career sat astride that particular fence I would have to agree !
Either way it sounds like the ZWO software is definitely non compliant though
Cheers
Robin
Nick said “The FITS “standard” is irritatingly vague about things like this ..”
According to this document, in 1997 the IAU recognised this confusion and standardised DATE-OBS as the start time
https://www.cv.nrao.edu/fits/documents/standards/year2000.txt
“4.2) Henceforth, DATE-OBS shall be assumed to refer to the start of an
observation. Other interpretations must be clearly explained in the comment field.”
Cheers
Robin
The BeSS fits standard used in the spectroscopy database specifies optionally DATE-END for the end time but I think it is rarely used and DATE-OBS (start time) and EXPTIME is normally used
“Date-Time of start of exposure ● Keyword = DATE-OBS (mandatory except if DATE-END and EXPTIME are present) ● Format: char (70 char max) ● Mandatory format: yyyy-mm-ddThh :mm:ss[.ss…] ● Example: 2006-02-25T13 :34 :43.5543
Date-Time of End of Exposure ● Keyword = DATE-END (mandatory except if DATE-OBS and EXPTIME are present) ● Format: char (70 char max) ● Mandatory format: yyyy-mm-ddThh :mm:ss[.ss…] ● Example: 2006-02-25T13 :34 :43.5543
Exposure Time ● Keyword = EXPTIME (mandatory except if DATE-OBS and DATE-END are present) ● Format: float ● Units: seconds ● Valid Range: >= 0
There has been significant evolution in the spectrum, the He I N II C II lines being replaced by Fe II lines as the classification Atel suggested might happen
Cheers
Robin
The intensity of the emission component of the Balmer lines and of the He II emission which have gradually been increasing has significantly reduced tonight. Is this expected behaviour or signs of a further outburst ?
Cheers
Robin
Christian Knigge also suggested following the He II / H beta region at higher resolution looking for RV variations. Here is 4 hour time series at 10 minutes cadence from last night with the LHIRES at R~2000 . Not sure there is much to see above the noise though (SNR in a 10 min exposure is ~50)
The average
and the individual spectra (rectified)
_20210721_068_Leadbeater.png)
