Talk:T Pyxidis

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1966 or 1967?[edit]

The exact year of the last nova seems unclear. Some sources claim 1966, others 1967. I've kept 1966 because of this source:

Webbink, Ronald F., Mario Livio, and James W. Truran and Marina Orio. "The Nature of Recurrent Novae", The Astrophysical Journal, 314, 653-672, March 15, 1987.

Page 658: Link.


Quote: 

  ... It is known to have experienced outbursts in 1890, 1902, 1920, 1944, and 1966 ...
  ... The 1966 outburst required 32 days to reach maximum light, exhibited a relatively flat maximum, and then declined ...

~Styck 82.95.107.93 (talk) 12:50, 5 January 2010 (UTC)[reply]

Comments on outbusrt: The outburst started at the end of the year of 1966, peaked at its maximum brightness (V almost 6) at the beginning of 1967 and staid in high state for a few months (1967). So it is really an outburst that spread over the end of 1966 and the beginning of 1967. For more info [1]. Since the outburt started in 1966, many call it the 1966 outburst, but it peaked in 1967 and continued for several month into 1967, so other authors call it the 1967 outburst. Extragalacticalien (talk) 16:59, 17 February 2011 (UTC)[reply]

The 1966 outburst was first noticed on Dec 7, 1966, and the maximum brightness occurred on Jan 11, 1967. This is the source of the confusion. I believe convention is based on discovery date. Autkm (talk) 00:03, 7 January 2010 (UTC)[reply]

References

  1. ^ Catchpole, R.M., 1969, Monthly Notices of the Royal Astronomical Society, n.142, p.119

Distance[edit]

The distance to stars like this is very difficult to determine. The value 3260 light years is actually 1 kiloparsec (1000 parsecs). The implied precision in light years is misleading. The actual value could range significantly from that value. However, I think changing to a different unit or even correcting the number of significant figures would not accomplish enough to make it worth doing. Autkm (talk) 00:03, 7 January 2010 (UTC)[reply]

Comments on the distance: The distance as estimated by different groups ranges from about 1,000pc to 4000pc

[1050pc lower limit: [1]  ; 4000pc: [2]. 3500pc: [3] ; 1000pc: [4] ]

The implications of having a distance of only 1000pc against the more commonly accepted 3,500pc are significant, as many modeling [e.g. ][5] assumed 3,500pc and their results depend on this distance. I would suggest to modify the text to reflect the fact that the distance could be anywhere between 1,000pc and 3,500pc. Extragalacticalien (talk) 16:38, 17 February 2011 (UTC)[reply]

Having read several recent abstracts and articles on T Pyx, it appears the "accepted distance" is closer to 3.5 +/- 1 kpc. If I don't see arguments against this, I will make this change and add the necessary references. Autkm (talk) 18:31, 11 November 2011 (UTC)[reply]

I had trouble believing the high figures for the distance to T Pyx given the small size of the stars, but calculations yield the following.

  • The main-sequence star has a maximum mass of 0.17M☉. By interpolation in the [original table][6] from which the table under red dwarfs was taken, between the entries for M4 (0.20M☉) and M6 (0.10M☉), an absolute visual magnitude of MV = 13.5 is found, for a visual luminosity of 0.0035 that of the Sun.
  • At 4780 pc, T Pyx has a distance modulus of -13.4 magnitudes, and with an apparent magnitude of m = +15.5, the system has an absolute visual magnitude of MV = +2.1, or a system visual luminosity of 12.4 times that of the Sun (hence the red dwarf's contribution is insignificant).
  • Bolometric absolute magnitude of a black body is Mbol = M☉ - 2.5[4 log (Teff/T☉) + 2 log (R/R☉)].
  • From the graph in the discussion of white dwarfs, the radius for a white dwarf at the estimated mass of 0.7M☉ is 0.012 to 0.014R☉. Hence the bolometric magnitude is Mbol = 51.7 - 10 log Teff for R = 0.013 and T☉ = 5,800 K.
  • For the bolometric correction for hot stars, Girardi et al.[7] display a graph from which a linear relationship between the BC and the log of the effective temperature can be found: BC = C - 7.32 log Teff where C is a constant ranging from 30.0 to 30.75. Using a middling value of 30.4 for C, the absolute visual magnitude is MV = Mbol - BC = 21.3 - 2.68 log Teff, or Teff = 10^((21.3 - MV)/2.68).

Therefore the temperature can be estimated as follows:

Distance (kpc) MV Teff (K)
4.8 2.1 15,000,000
3.5 2.8 8,100,000
1.05 5.4 860,000

Multimegakelvin temperatures are consistent with frequent thermonuclear events on the surface, so one might think the large computed distances are realistic. However, a spherical black body 0.013R☉ in radius at a temperature of 15 million K would have a bolometric absolute magnitude of -19.9, for a luminosity of 2.95×1036 W, most of it in X-rays with λpeak = 0.19 nm. It would exceed the apparent X-ray brightness of Scorpius X-1 by a factor of 43,000. There is indeed a discrepancy with these data. Hieronymus Illinensis (talk) 05:50, 25 February 2018 (UTC)[reply]

References

  1. ^ Catchpole, R.M. 1969, Monthly Notices of the Royal Astronomical Society, #142, page 119
  2. ^ Kato, M. 1990, The Astrophysical Journal, #362, Letter, page 17
  3. ^ Selvelli, P., Cassatella, A., Gilmozzi, R., Gonzalez-Riestra, R. 2008, Astronomy and Astrophysics, vol.492, page 787.
  4. ^ Sion, E.M., Godon, P., & McClain, T. 2010, American Astronomical Society meeting #215, 416.27
  5. ^ Selvelli, P., Cassatella, A., Gilmozzi, R., Gonzalez-Riestra, R. 2008, Astronomy and Astrophysics, vol.492, page 787.
  6. ^ Kaltenegger, L.; Traub, W. A. (2009). "Transits of Earth-like Planets". The Astrophysical Journal. 698 (1): 519–527. doi:10.1088/0004-637X/698/1/519.
  7. ^ Girardi, L.; Dalcanton, J.; Williams, B.; et al. (2008). "Revised Bolometric Corrections and Interstellar Extinction Coefficients for the ACS and WFPC2 Photometric Systems". Publications of the Astronomical Society of the Pacific. 120 (867): 583–591. doi:10.1086/588526. {{cite journal}}: Explicit use of et al. in: |author4= (help)

AAVSO Light Curves[edit]

Are AAVSO Light Curves free to use? I used them to verify maximum magnitude, but if I can use it to show overall light curve, I will do so. Autkm (talk) 03:32, 20 April 2011 (UTC)[reply]

This article needs a rewrite[edit]

Many paragraphs are in flagrant contradictions with one another, and some just don't work well in their chronology. —Preceding unsigned comment added by 184.163.52.221 (talk) 05:30, 17 April 2011 (UTC)[reply]

Mankind survived or will survive?[edit]

"Mankind survived when the Crab Nebula went off at a distance of about 6500 light-years in the year 1054."

There is a contradiction in this sentence. If the Crab Nebula is at 6500 light-years, it will take at least 6500 years for its materials to reach Earth. So rendez-vous in year 5446?

Obviously that is referring to earth-time. It won't be ambiguous for another 2.5 millenia. Hopefully the English wording won't be relevant by then. See also Crab nebula. Aij (talk) 06:10, 8 March 2012 (UTC)[reply]
What? The previous response is non-sensical. SN 1054 became apparent to us in - guess when? That's right - 1054 (AD/CE)! That means that that's when it's electromagnetic radiation, including visible light, X-rays and gamma rays, reached us on earth and allowed us to see it, meaning that this radiation had already traveled the noted 6,500 years by then.

Reworded to remove ambiguity Hieronymus Illinensis (talk) 23:28, 24 February 2018 (UTC)[reply]

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