Hydrogen- Deficient Stars: some statistics Simon Jeffery Armagh Observatory Hydrogen-Deficient Stars Discovery Classification Surveys Distribution Frequency
Jan 30, 2016
Hydrogen-Deficient Stars:some statistics
Simon Jeffery
Armagh Observatory
Hydrogen-Deficient Stars
Discovery
Classification
Surveys
Distribution
Frequency
Hydrogen-Deficient Stars
Williamina Fleming 1857-1911
Sgr
Stars without hydrogen? 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
reluctance
irrefutable evidence
...somehow, a very substantial amount of hydrogen had been lost
Discovery of helium 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
Sir Joseph Norman Lockyer: 1836-1920
Sir William Ramsay: 1852-1916
cleveite
Pierre Jules Janssen: 1824-1907
Lord Rutherford: 1871-1937
Helium Stars? Wolf & Rayet
1857 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
faint blue stars in the Galactic halo
Greenstein and Sargent 1974, ApJS 28, 157
Jesse Greenstein Wallace Sargent
The Palomar-Green catalog of uv-excess stellar objects
Green, Schmidt and Liebert 1986, ApJS 61, 305
Hydrogen-Deficient Stars in the Galaxy recent history high mass low mass degenerates and rejuvenants
1985: Mysore
1991:
Tutukov 1991, IAU Symp 145, 351
Population I and massive helium stars
Helium-rich B stars Wolf-Rayet Stars SN Ib [ Algols ] Ups Sgr variables
Normal stellar evolution
Iben 1967, Ann Rev A&A 12, 215
Evolution of a 5M star
Iben 1967, Ann Rev A&A 12, 215
He-core burning
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?
He-richFe-poor
clouds
Groote & Hunger 1997, AA 331, 250
Bond & Levato 1976, PASP 88, 95
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
Type Ib Supernovae similar to SN I
no H lines no Si II at maximum
near star formation sites strong He features
SN IaSN IbSN II-pSN II
Wheeler 1997, Sci.Am.
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.
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.
Sgr variables 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~?
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 ?
The stellar atmosphere opacity problem
compare late B stars with Sgr similar Teff
similar gravity same resolution
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
1992: St Andrews
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 CrBR CrB
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
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
Helium-rich subdwarfs
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
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
Hdef planetary nebulae central stars
Spectral-type [WC] H-poor, C very strong ~50 in 1996 list
Hamann 1996, ASPC 96, 127
NGC6369 - HST/PC
Hamann 1996, ASPC 96, 127
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
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
PG1716
Degenerates and Rejuvenants
H-def white dwarfs
AM CVn binaries
Born-again stars
Image: Keck Observatory
BPM 37093 (actually a DA, but it’s a neat picture!)
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
AM CVn stars “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
Warner & Robinson 1972
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 SgeV605 AqlV4334 Sgr
Problems to solve Astronomy
statistics distribution
Evolution masses origin and fate links between classes
Physics atmospheres pulsations mass loss convection nucleosynthesis