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Hydrogen-Deficient Stars: some statistics

Hydrogen-Deficient Stars: some statistics. Simon Jeffery Armagh Observatory. Hydrogen-Deficient Stars Discovery Classification Surveys Distribution Frequency. Williamina Fleming 1857-1911. Hydrogen-Deficient Stars.  Sgr. Fleming 1891 Ludendorff 1906 Joy & Humason 1923

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Hydrogen-Deficient Stars: some statistics

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  1. Hydrogen-Deficient Stars:some statistics Simon Jeffery Armagh Observatory Hydrogen-Deficient Stars Discovery Classification Surveys Distribution Frequency

  2. Williamina Fleming 1857-1911 Hydrogen-Deficient Stars

  3.  Sgr

  4. Fleming 1891 Ludendorff 1906 Joy & Humason 1923 Plaskett 1927 Payne 1925 Berman 1935 Struve & Sherman 1940 Greenstein 1940 “The spectrum of  Sgr is remarkable since the hydrogen lines are very faint and of the same intensity as the additional dark lines” H completely absent in R CrB Hydrogen lines were “greatly weakened by partial emission” in the spectrum of RCrB the simultaneous appearance of helium and metallic lines might be “due to a supernormal abundance of helium or to the star being an exaggerated form of pseudo-cepheid or giant” “The uniformity of composition of stellar atmospheres appears to be an established fact” R CrB  Sgr  Sgr Stars without hydrogen? reluctance irrefutable evidence ...somehow, a very substantial amount of hydrogen had been lost

  5. 1868: A bright yellow line at 587.49nm in the spectrum of the chromosphere of the Sun 1868: A yellow line in the solar spectrum, labelled D3,, concluded it was caused by an element unknown on earth and labeled it: λιος (helios). 1895: Isolated helium by treating cleveite with mineral acids. Actually looking for argon, but after removing N and O noticed a bright-yellow line that matched the D3 line seen in the Sun. Cleveite is an impure variety of uraninite. It has the composition UO2 with about 10% of the uranium substituted by rare earth elements. Helium is created by the alpha radiation of the uranium which is trapped (occluded) within the mineral 1907: Identifies alpha particle with He++ nucleus Pierre Jules Janssen: 1824-1907 Discovery of helium Sir Joseph Norman Lockyer: 1836-1920 Sir William Ramsay: 1852-1916 cleveite Lord Rutherford: 1871-1937

  6. Wolf & Rayet1857 Popper 1940’s Hofmeister 1940 Herbig 1968 Greenstein & Matthews Bidelman Warner 1967 Greenstein & Sargent 1974 Schmidt, Green & Leibert 1986 EC, HS, SDSS1990 - 2006 Stars with broad emission lines HD124448 FG Sge AM CVn “hydrogen-deficient carbon stars” -- a “portmanteau” expression for the lot Faint blue stars: sdO,sdB PG1159, sdOC, sdOD He-sdB, He-sdO Helium Stars?

  7. Jesse Greenstein Wallace Sargent faint blue stars in the Galactic halo Greenstein and Sargent 1974, ApJS 28, 157

  8. The Palomar-Green catalog of uv-excess stellar objects Green, Schmidt and Liebert 1986, ApJS 61, 305

  9. Hydrogen-Deficient Stars in the Galaxy • recent history • high mass • low mass • degenerates and rejuvenants

  10. 1985: Mysore

  11. 1991: Tutukov 1991, IAU Symp 145, 351

  12. Helium-rich B stars Wolf-Rayet Stars SN Ib [ Algols ] Ups Sgr variables Population I and massive helium stars

  13. Normal stellar evolution He-core burning Evolution of a 5M star Iben 1967, Ann Rev A&A 12, 215 Iben 1967, Ann Rev A&A 12, 215

  14. Helium-rich B orIntermediate He stars • CP MS B stars • 24 in catalogue of Drilling & Hill 1986 • Helium-variable: P~1-10d •  Ori E • dipole magnetic field ~104 G inclined ~90 • metal-poor magnetic caps • He-rich patches due to elemental segregation • corotating clouds? Bond & Levato 1976, PASP 88, 95 Fe-poor He-rich clouds Groote & Hunger 1997, AA 331, 250

  15. Wolf-Rayet stars • 1867: Charles Wolf and George Rayet at the Observatoire de Paris • Early-type stars with bright broad emission lines • Disagreement whether they were H-deficient up the the early 80’s • Found solely in spiral arms, associations and young clusters • N-rich and C-rich sequences WN and WC • H detected in about half • About 230 Wolf-Rayets in the Galaxy • (227: van der Hucht 2001) • 159 WRs <15m • 100 in the LMC, 12 in the SMC

  16. SN Ia SN Ib SN II-p SN II Type Ib Supernovae • similar to SN I • no H lines • no Si II at maximum • near star formation sites • strong He features Wheeler 1997, Sci.Am.

  17. SN Ib rates • Cappellaro et al. (1993) Ia: 0.39 +/- 0.19 SnuIb/c: 0.27 +/- 0.18 Snu II: 1.48 +/- 0.65 SNu.

  18.  Sgr • Spectrum~Ap • Campbell 1899, Cannon 1912 • composite variable • strong helium on metallic spectrum • H, H in emission • Plaskett 1928, Morgan 1935, Merrill 1939, Greenstein 1940 et seq.

  19.  Sgr Mp=3.0±0.3M Rp~60R Lp~105 L nHe/nH~104  Sgr P=138 d KS Per P=360d LSS 1922 P~55d LSS 4300 P~? ? BI Lyn P~?  Sgr variables • velocities close to circular orbits about galactic center • less than 200 pc from galactic plane • Pop I helium stars with M>MChandrasekhar • SN Ib progenitors ?

  20. The stellar atmosphere opacity problem • compare late B stars with  Sgr • similar Teff • similar gravity • same resolution

  21. Low-mass helium stars • R CrB stars • Extreme helium stars • He-sdB stars • He-sdO stars • H-def PN central stars • O(He) stars • PG1159 stars

  22. 1992: St Andrews

  23. R Coronae Borealis variables • ~ 35 known in galaxy,17 in the LMC (Clayton’s web page) • Irregular light fades (5m) • Low-amplitude pulsations • Hydrogen-deficient spectrum • Infrared excess R CrB R CrB

  24. Extreme Helium stars • Approx. 20 known in galaxy • Spectrum: A- and B- • Strong HeI • Narrow lines: supergiant • No Balmer lines • Strong N and C • Origin? - clues from • distribution • chemical composition • low-amplitude pulsations Comparison of spectrum of an extreme helium star with a helium-rich B star. Jaschek & Jaschek, 1987, The classification of stars, Cambridge

  25. Distribution and kinematics • concentrated towards gal. center • do not share galactic rotation • Galactic bulge • hence range of Z Jeffery, Drilling & Heber 1987, MNRAS 226, 317

  26. Helium-rich subdwarfs • He-sdO/sdB easily confused - need better classifications (cf Drilling et al. ) • PG definition (NGP) of sdOD same as for EHe stars found by Drilling in survey of OB+ stars (in plane) • HesdB: • Prototype PG1544+488- is a close binary! • Others JL87, LB1766, …- quite heterogeneous • PG survey: • sdO • sdOB • sdOC - He-sdO • sdOD - He-sdB • ~ 50 He-rich subdwarfs in 1996 catalogue: did not discriminate sdB/sdO • SDSS DR4 • He-sdB 5 • He-sdB: 11

  27. Hdef planetary nebulae central stars • Spectral-type [WC] • H-poor, C very strong • ~50 in 1996 list NGC6369 - HST/PC Hamann 1996, ASPC 96, 127 Hamann 1996, ASPC 96, 127

  28. O(He) stars • He II absorption • CIV, NV, OVI emission • 1996: 3 • 1998: 4 (=3+2-1) • GJJC1 = He-sdO • PN / no PN ~ 1 • “Same domain as PG1159 stars but considerably less metal rich” Rauch et al. 1998, A&A

  29. PG1716 PG1159 stars • Spectroscopically unusual in the PG survey • Very short-period mulit-periodic variables • Spectra - HeII, highly ionized C, N, in abs and emission • No PN

  30. Degenerates and Rejuvenants • H-def white dwarfs • AM CVn binaries • Born-again stars BPM 37093 (actually a DA, but it’s a neat picture!) Image: Keck Observatory

  31. H-deficient white dwarfs • H-dominated 4367 • DA 4008 H lines, no HeI or metal • DAx 236 H lines, other weak lines • DA+bin 123 DA+ms star • He-dominated 1009 • DB 332 HeI lines, no H or metal • DBx 65 • DO 32 He II, plus He I or H • DOx 15 • DQ 91 Carbon lines • DQx 21 • DZ 61 Metal lines, no H or He I • DC 358 Continuous spectrum • DZx 22 • Dx 12 (DD,DF,DG,DH,DK,DX) • Total 5376 Similar numbers (0.3dex) in SDSS DR4 catalogue (Eisenstein et al. 2006), but DB gap remains a real phenomenon. http://www.astronomy.villanova.edu/WDCatalog/index.html

  32. AM CVn stars Warner & Robinson 1972 • “HZ 29 is a peculiar, hydrogen deficient white dwarf with broad, apparently double absorption lines of He I” (Greenstein and Matthews 1957,1958) • Interacting binary white dwarfs: P~17 - 46 min • Accretion disk seen in high (optically thick) and low (thin) states, cf. CVs • 15 systems known (cf. 6 in 1996!) • (0) 1x10-6 -1 pc-3 (Roelofs et al. 2007) • Merger progenitors? • Probable GWR sources for LISA • Reviews: Warner 1995, Nelemans 2005

  33. Born-again stars • 3 in 100 years • Rare? • 3x107 / Gyr / Galaxy • Not so rare? • How does this compare with birth-rate of white dwarfs? • What fraction of p-AGB stars experience a late or very late thermal pulse? • FG Sge • V605 Aql • V4334 Sgr

  34. Problems to solve • Astronomy • statistics • distribution • Evolution • masses • origin and fate • links between classes • Physics • atmospheres • pulsations • mass loss • convection • nucleosynthesis

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