Transcript This is a first test slide - National Optical Astronomy

Boris Gänsicke
John Southworth John Thorstensen
Ilse Decoster
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
SDSS finds the period minimum spike
CV Evolution in a nutshell
• Angular momentum loss MB/GR
MB
GR
• Porb decreases down to Pmin
• Donor becomes degenerate BD
• Porb increases again
Howell et al. (2001)
Period bouncing
CV evolution in a nutshell
• Angular momentum loss MB/GR
• MB disrupted at P=3h
• At Pmin: donor  BD
• Spike at Pmin
1%
• Most systems post-bounce
GR
29%
MB
70%
Howell et al. 2001, ApJ 550, 897
Kolb & Baraffe 1999, MNRAS 309, 1034
Ritter 5 (1990): 167 CVs
Ritter & Kolb 6 (1998): 314 CVs
Ritter & Kolb 7.2 (2004): 518 CVs
CV evolution: theory & observations
• Pmin≈65min
• Spike @ Pmin
80 min!
selection effects?
(Ritter & Kolb 2004)
Of spikes and small numbers
114min
80 polars today
Hameury et al. (1990)
The PG CVs
no spike (see Pretorius)
- 35 CVs, of which 31 new
- 31 periods determined
(Ringwald PhD 1993, Thorstensen, and others)
CVs from the Hamburg Quasar Survey
spike?
- 96 CVs, of which 53 new
- 86 periods determined
... 24 HQS CVs with Porb=3-4h ...
(Gänsicke, Rodríguez-Gil, Aungwerojwit, Hagen, Engels, ...)
SDSS CVs
- 101 CVs, of which 90 new ITP time 2004/5 for SDSS CV follow-up:
70 nights WHT, TNG, INT, NOT & LT
- 45 periods determined
(Gänsicke et al.)
(Szkody et al. 2002, 2003, 2004)
SDSS CVs in DR7
?
- 281 CVs, of which 90 new
- 126 periods determined
(Szkody et al. 2002, 2003 , 2004 , 2005 , 2006 , 2007 , 2009)
10 years effort in 2 minutes
Period accurate to better than 3%
10 years effort in 2 minutes
Period accurate to better than 3%
10 years effort in 2 minutes
Period accurate to better than 3%
SDSS CVs differ significantly from previous samples
two-sided Kolmogorov-Smirnov test
new SDSS CVs
- old vs non: 52.2%
old SDSS CVs
- new vs non: 0.065%
non-SDSS CVs
why?
Gänsicke et al. 2008, MNRAS, submitted
Properties of SDSS CVs
“active” CVs in the spike
V844 Her
T Leo
SW UMa
EV UMa
GG Leo
Old (active) SDSS CVs with 80min<Porb<86min
SW UMa
T Leo
V844 Her
EV UMa
New SDSS CVs with 80min<Porb<86min
New (inactive) SDSS CVs with 80min<Porb<86min
New (inactive) SDSS CVs with 80min<Porb<86min
New (inactive) SDSS CVs with 80min<Porb<86min
eclipsing
poor data
polar
eclipsing
New (inactive) SDSS CVs with Porb>86min
New (inactive) SDSS CVs with Porb>86min
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
SDSS finds the period spike because of depth
“SDSS all”
“SDSS Quasar Survey”
“Hamburg Quasar Survey”
“Palomar Green”
Completeness: the QSO exclusion boxes
while excluded from the QSO programme, there are sufficient
spectra to inspect the kind of objects they contain.
-WD box: one faint CV
-A-star box: no CV
-WMDS box: 5 CVs with Porb>150min
 no effect on the period spike discussed here
non-SDSS-discovered CVs in the SDSS footprint
QSO survey limit
SDSS CV (re)identification efficiency
QSO survey limit
CV has re-discovered ~90% of the previously
known CVs with 17<g<19
Testing CV completeness by colour proximity
i<19.1: 66% complete
19.1<i<23: 13% complete
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
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
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