Robin Leadbeater

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Viewing 20 posts - 301 through 320 (of 1,188 total)
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  • in reply to: BAA AGM & Meeting. #584706
    Robin Leadbeater
    Participant

    The legal restrictions have been lifted but the wearing of face masks and social distancing where possible is still advised by both the government and NHS as ways to limit the spread. Personal freedom works both ways. A poll of members would be interesting. It could be that actually more members would attend provided modest precautions like face masks and social distancing were in place than would not attend because they do not wish to follow the guidelines. 

    in reply to: LL And rare outburst #584694
    Robin Leadbeater
    Participant

    Thanks Gary.

    The Taichi Kato paper was not published until 2004.

    https://ui.adsabs.harvard.edu/abs/2004PASJ…56S.135K/abstract

    I will send a correction to CDS

    Cheers

    Robin

    in reply to: Nova And 1979 ? #584683
    Robin Leadbeater
    Participant

    Here is the spectrum of BD+25 103, also  identified (likely incorrectly) in SIMBAD as Nova And 1979,  compared with an F2v standard 

    in reply to: LL And rare outburst #584682
    Robin Leadbeater
    Participant

    Hi Gary,

    Could “Nova And 1979” actually have been LL And with a position error?  See VSSC #83 1995 p7 and separate thread on “N And 1979”

    https://britastro.org/vss/VS0083.pdf

    (Your first VSSC after you took over directorship in 1995 by the looks)

    Robin

    in reply to: Nova And 1979 ? #584680
    Robin Leadbeater
    Participant

    The TA article

    http://articles.adsabs.harvard.edu/pdf/1979Astr…16..152.

    confusingly IAUC 3412 covers reports on several diverse objects including asteroid 1979QB

    http://www.cbat.eps.harvard.edu/iauc/03400/03401.html

    Cheers

    Robin

    in reply to: Nova And 1979 ? #584678
    Robin Leadbeater
    Participant

    Yes  that is a a copy of the IAUC with a request for observations. (confusingly that IAUC covers several diverse object discoveries)

    Could the difference be epoch 1950 for the IAU notification as opposed to epoch 2000 for Simbad”

    I was  comparing with the FK4 (1950) coordinates for the object in SIMBAD

    Cheers

    Robin

    in reply to: Nova And 1979 ? #584677
    Robin Leadbeater
    Participant

    The answer perhaps lies closer to home !

    From VSSC #83 page 7

    931207 LL And B.Marsden, CBAT, Paul Wild, Switzerland, Steve

    Howell, USA, T.Kato, Japan, Bruce Margon, USA Object reported as a ‘nova’ in IAUC 3412 (1979) seen again in outburst by Tony Vanmunster, Belgium 1993 Dec 7 mag 14.Ov. Confirmed by Poyner. Kato obtains CCD images at Ouda on Dec 9 V=14.0. Suggests position needs correction. Howell obtains spectra and paper planned!

    Robin

    in reply to: Nova And 1979 ? #584675
    Robin Leadbeater
    Participant

    Tracked down the discovery IAUCDifficult to say without knowing the precision of the coordinates given there but  they could be up to ~1 arcmin away from the ones in SIMBAD for this star so not sure yet where the association comes from

    in reply to: LL And rare outburst #584674
    Robin Leadbeater
    Participant

    A spectrum (R~500)

    Robin

    in reply to: Spectra of some planet eating white dwarfs #584653
    Robin Leadbeater
    Participant

    Ah interesting. I see that paper suggested Oxygen might be found as well through the same process. One was  found with just O in the spectrum, though by a suggested different mechanism where the He/H is stripped away.

    https://physicsworld.com/a/white-dwarf-with-nearly-pure-oxygen-atmosphere-surprises-astronomers/

    in reply to: Nova in Perseus #584652
    Robin Leadbeater
    Participant

    I see this has now faded to Vmag ~15 so  time for perhaps a last low resolution spectrum.  It shows a nebula type spectrum with strong forbidden emission lines, particularly [OIII] and a very weak almost undetectable continuum (The Y scale is relative to the continuum at 5500A and the signal/noise in the continuum is down in single figures). In fact I estimate 78% of the light in the V passband comes from just the [OIII] pair of lines at 4959/5007 A

    in reply to: Spectra of some planet eating white dwarfs #584650
    Robin Leadbeater
    Participant

    A quick literature search though brought up this reference which talks of WD with initial He atmospheres evolving an H dominated atmosphere through upward diffusion of H.

    https://arxiv.org/abs/2008.07469

    Anything heavier though I suspect must have been accreted.

    in reply to: Spectra of some planet eating white dwarfs #584649
    Robin Leadbeater
    Participant

    I don’t know how it relates to the progenitor but as I understand it, naked electron degenerate white dwarfs don’t show any spectral features and there are indeed some WD like that, designated spectral type DC.  The spectral features then come from a thin skin of accreted material, the heavier elements rapidly sinking into the interior to become part of the electron degenerate material so most show just H while others have He or a mix of H/He. You do also find some cool white dwarfs with Carbon in their spectrum, presumably also recently accreted.  

    in reply to: Spectra of some planet eating white dwarfs #584647
    Robin Leadbeater
    Participant

    Another interesting WD. No metals or Hydrogen, just  Helium

    in reply to: Fireball spectrum #584640
    Robin Leadbeater
    Participant

    Yes it was already clear in 2019 😉

    The OI 7774 line is possibly there under the 2nd order but out of focus

    in reply to: Nova in Hercules #584630
    Robin Leadbeater
    Participant

    Now at mag 16 but still within range of a very low resolution spectrum with the ALPY200.

    The spectrum with several forbidden nebula lines looks similar to that of  another very fast nova Sgr 1991 at similar age in Gray & Corbally , where the tentative line identifications come from

    Cheers

    Robin

    in reply to: VV Cep eclipse paper in JBAA #584619
    Robin Leadbeater
    Participant

     (is a 50% increase in effective radius due to pulsations feasible?)”

    Though of course a smaller change in radius would be sufficient depending on the path of the hot star behind the M star 

    in reply to: VV Cep eclipse paper in JBAA #584618
    Robin Leadbeater
    Participant

    Yes I agree. If the continuous brightness variations are  due to radial pulsations of the M star, these would produce changes in the effective radius (and opacity?)  of the M star. These could could asymmetrically shift the mid eclipse point dependent on their timing. (is a 50% increase in effective radius due to pulsations feasible?)

    Cheers

    Robin

    in reply to: VV Cep eclipse paper in JBAA #584614
    Robin Leadbeater
    Participant

    Hi Andy,

    The measurements pre 1997 were all based on the light curves which are indeed tricky to estimate the mid eclipse point from due to the continuing  brightness variability of the red giant throughout the eclipse seen in the AAVSO data in fig 5 of Hugh’s paper.  The photometry and spectroscopy were in good agreement within 7 days in 1998 though. 

    I have extracted  B-V  from the AAVSO data which is less influenced by brightness variations than using using V I think. I have marked Hugh’s spectroscopic mid eclipse and  the expected values based both on the earlier ephemeris and assuming a 60 day increase in period post 1978.

    Hugh’s value agrees well with the B-V data. The prediction based on a permanent increase in period is clearly not compatible  with the current data but perhaps there is enough wriggle room to say that the original ephemeris is ok and the 1997-1998 eclipse data (both spectroscopic and photometric) was anomalous for some reason? 

    Cheers

    Robin

    in reply to: VV Cep eclipse paper in JBAA #584615
    Robin Leadbeater
    Participant

    The argument for something to have happened though between 1978 and 1998 is convincing from fig 4 of the 1999 Graczyk et al paper if the error bars are to be believed

Viewing 20 posts - 301 through 320 (of 1,188 total)