sdss finds the period minimum spike boris gänsicke john southworth john thorstensen m dillon, p...
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SDSS finds the period minimum spike
Boris Gänsicke
John Southworth John Thorstensen
M Dillon, P Rodríguez-Gil, A Aungwerojwit, TR Marsh, P Szkody, SCC Barros, J Casares, D de Martino, PJ Groot, P Hakala, U Kolb, SP Littlefair,
IG Martínez-Pais, G Nelemans, MR Schreiber
Ilse Decoster
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CV Evolution in a nutshellH
ow
ell e
t al. (2
00
1)
• Angular momentum loss MB/GR
MBGR
• Porb decreases down to Pmin
• Donor becomes degenerate BD
• Porb increases again
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Period bouncing
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CV evolution in a nutshell
Howell et al. 2001, ApJ 550, 897Kolb & Baraffe 1999, MNRAS 309, 1034
70%
29%
1% • Most systems post-bounce
• Spike at Pmin
MB
GR
• Angular momentum loss MB/GR
• At Pmin: donor BD
• MB disrupted at P=3h
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Ritter 5 (1990): 167 CVs
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Ritter & Kolb 6 (1998): 314 CVs
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Ritter & Kolb 7.2 (2004): 518 CVs
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CV evolution: theory & observations
• Pmin≈65min
80 min!
(Ritter & Kolb 2004)
• Spike @ Pmin
selection effects?
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Of spikes and small numbers
Hameury et al. (1990)
114min
80 polars today
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The PG CVs
- 35 CVs, of which 31 new
- 31 periods determined
(Ringwald PhD 1993, Thorstensen, and others)
no spike (see Pretorius)
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CVs from the Hamburg Quasar Survey
- 96 CVs, of which 53 new
- 86 periods determined
(Gänsicke, Rodríguez-Gil, Aungwerojwit, Hagen, Engels, ...)
... 24 HQS CVs with Porb=3-4h ...
spike?
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SDSS CVs
(Szkody et al. 2002, 2003, 2004)
- 101 CVs, of which 90 new
- 45 periods determinedITP time 2004/5 for SDSS CV follow-up:70 nights WHT, TNG, INT, NOT & LT(Gänsicke et al.)
Recycled slide detected … recycled slide
detected …
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SDSS CVs in DR7
(Szkody et al. 2002, 2003 , 2004 , 2005 , 2006 , 2007 , 2009)
- 281 CVs, of which 90 new
- 126 periods determined
?
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10 years effort in 2 minutes
Period accurate to better than 3%
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10 years effort in 2 minutes
Period accurate to better than 3%
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10 years effort in 2 minutes
Period accurate to better than 3%
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SDSS CVs differ significantly from previous samples
new SDSS CVs
old SDSS CVs
non-SDSS CVs
- old vs non: 52.2%
- new vs non: 0.065%
two-sided Kolmogorov-Smirnov test
Gänsicke et al. 2008, MNRAS, submitted
why?
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Properties of SDSS CVs
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“active” CVs in the spike
V844 HerT LeoSW UMaEV UMaGG Leo
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Old (active) SDSS CVs with 80min<Porb<86min
SW UMa T Leo
V844 Her EV UMa
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New SDSS CVs with 80min<Porb<86min
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New (inactive) SDSS CVs with 80min<Porb<86min
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New (inactive) SDSS CVs with 80min<Porb<86min
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New (inactive) SDSS CVs with 80min<Porb<86min
eclipsing
poor data eclipsing
polar
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New (inactive) SDSS CVs with Porb>86min
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New (inactive) SDSS CVs with Porb>86min
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Some comments on the space density
- WD-dominated, or “WZ Sge” are often considered
post-period-bounce (candidate) systems…- Yes, SDSS finds many new “WZ Sge”… but,
they are all faint (g>17.6) and far (>150pc) away…
- …yet, no bias against finding nearby “WZ Sge”…
- “WZ Sge”s, bouncers or not, are not very common
- While Littlefair found good evidence for bouncers, they are all at Pmin
- Even SDSS has not found the predicted large population of period bouncers
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SDSS finds the period spike because of depth
“Palomar Green”
“Hamburg Quasar Survey”
“SDSS Quasar Survey”
“SDSS all”
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Completeness: the QSO exclusion boxes
-WD box: one faint CV-A-star box: no CV-WMDS box: 5 CVs with Porb>150min
while excluded from the QSO programme, there are sufficientspectra to inspect the kind of objects they contain.
no effect on the period spike discussed here
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non-SDSS-discovered CVs in the SDSS footprint
QSO survey limit
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SDSS CV (re)identification efficiency
CV has re-discovered ~90% of the previously known CVs with 17<g<19
QSO survey limit
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Testing CV completeness by colour proximity
i<19.1: 66% complete
19.1<i<23: 13% complete
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Selecting CV candidates via p.m. from GALEX/SDSS
1437 objects with- 5 p.m.- GALEX fluxes- SDSS spectra
all WD-cut QSO-cut
CV 67 67 63 11.3%
WD 601 169 113 31.5%
WDMS 398 368 308 55.2%
QSO 371 363 74 13.3%
Total 1437 967 558
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Selecting CV candidates via p.m. from GALEX/SDSS
3713 objects with- 5 p.m.- GALEX fluxes- no SDSS spectra
1689 candidates, expect- 191 CVs- 532 WDs- 932 WDMS binaries- 225 QSO
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Summary
• SDSS goes deeper than any survey before, and the SDSS CV population exhibits a period spike at Pmin=80min, but need accurate orbital periods
• The spectra of the majority of “spike” CVs are WD dominated, “WZ Sge”-like, but SDSS has still not found the predicted large population of period-bouncers.
• The SDSS CV population is 66-90% complete for 17<i<19, but completeness drops quickly below i=19.1 … and that’s where the WD-dominated CVs become more numerous!
• The “missing” SDSS CV population can be targeted via a selection combining optical/UV colours and proper motion