1. Pulsating WD Paula Szkody, Anjum Mukadam, Boris Gaensicke, Arne Henden + AAVSO, Atsuko Nitta, Ed Sion, Dean Townsley Wild Stars March 16, 2009 Tantalizing Hints from CVs with Pulsating WDs

2. Why study WD pulsators ? Pulsations probe inner stellar structure uniform density; pulsations penetrate the inner 99% of white dwarf Asteroseismology allows determination of:  Mass (total and H layer)  Rotation rate  Core Composition  Cooling rate

3. Why study accreting WD pulsators ? Find effects of accretion on pulsations  Heating due to accretion  Increase in angular momentum  Changing surface composition  Changing stellar mass

4. White dwarfs show non-radial g-modes on account of their high gravity Periods of 100s to 1000s These modes are characterized by quantum numbers (k,l,m) similar to atomic orbitals k is #nodes between surface and center l is # nodes on surface (borders between hot and cool zones) m is # on surface that pass through pole of rotation axis

5. Modes of Pulsation l = 1 m = 1 m = 0 l = 2 m = 1 m = 0 Stellar Surface see www.whitedwarf.org

6. Ideal short term seismology ● Find a star with many (~10) pulsation modes ● Identify the quantum numbers for each mode ● Use WD pulsation models to get a unique fit to the observed periods Model fit Temperature, stellar mass H/He layer masses Model luminosity Distance to star Multiplet structure Magnetic field or rotation Model core composition 12 C, 16 O nuclear reaction rate in RG stage

7. 3 major questions: 1) where is the instability strip for accreting pulsators? 2) what are the affects of accretion and outbursts? 3) is there any hope of pulling out mass, spin, etc?

8. Instability Strips for Non-Interacting White Dwarf Pulsators ZZ Ceti 11000-12000K 25000K Our question: where is the instabilty strip for accreting pulsators?

9. Step 1: Find some Accreting Pulsators Cataclysmic Variables at quiescence with very short ~80-90 min orbital periods so accretion rate at a minimum 10 -13 M  /yr 90% of the optical light comes from the white dwarf So it’s possible to detect white dwarf pulsations! 13 known accreting pulsators to date Need:

10. It’s a short history (1998-2009): GW Lib7617.0650,370,230Warner & van Zyl 1998 SDSSJ1610-018119.0609,347I. Woudt & Warner 2004 SDSSJ2205+118320.3575,475,330II. Warner & Woudt 2004 SDSSJ0131-098218.5595,335,260II. Warner & Woudt 2004 V455 And (HS)8116.5300-360Araujo-Betancor et al. 2005 PQ And8119.5634,1283 Vanlandingham et al,Patterson et al 2005 REJ1255+26611918.01344,1236,668Patterson et al 2005 SDSSJ1514+4519.7559IV. Nilsson et al 2006 SDSSJ1339+488317.6641IV. Gansicke et al 2006 SDSSJ0745+458619.11010,647V. Mukadam et al 2007 SDSSJ0919+088118.2260IV. Mukadam et al 2007 SDSSJ1507+526718.31140,660,500IV. Patterson et al 2008 SDSS0804+518517.9756V. Pavlenko 2008 P orb (min) V (mag) P pulse (sec) Ref

11. signature of pulsating, accreting WDs

12. Step 2: Get UV data Ly  region allows best T determination Pulse amplitudes 6-17 x larger in UV

13. UV time-series spectroscopy Space Telescope Imaging Spectrograph (STIS) 1150-1750A with 1A resolution, time-tag HST Advanced Camera for Surveys (ACS) Solar Blind Channel (SBC) 1200-1900Å 6-40A resolution, 1 min integrations Co-added Spectrum & Light Curve HST Programs 2002/2008 UV data on 9 so far until SM4!

14. Ground data are necessary: We need to know the optical state (to make sure object is at quiescence - HST insists) Simultaneous UV & opt pulsation amplitudes are needed to determine the mode

15. HST Obs AAVSO + help  HST picks week months in advance  AAVSO issues alert/web page ~ 2 wks-1 month before HST  AAVSO monitors  HST gives date/time 1 week prior to obs  ground obs 24 hr prior t akes halt off  HST observes with ground support GW Lib Jan 17, 2002 STIS V455 And Oct 24, 2002 STIS snap SDSS0131 Jun 18, 2005 SBC SDSS2205 May 23, 2005 SBC SDSS1610 June 30, 2005 SBC PQ And Sep 13 2007 SBC SDSS0745 Nov 1, 2007 SBC SDSS0919 Nov 14, 2007 SBC SDSS1339 Jan 25, 2008 SBC Object Date Instrument

16. fits with 2 component WD: 63% at 13,300K, 37% at 17,100K STIS on GW Lib

17. 16,500 WD model Accretion disk SBC Fit to HST spectrum of SDSSJ0745+45

18. 10,000K WD 12,000K WD 15,000K WD HST data SDSS0745 16,500K WD SDSS data UV + opt with WD models

19. V455 And = HS 2331+39 10,000K 20,000K 12,000K 11,000K STIS + Calar Alto data on

20. 12001600 18001400 HST data on PQ And SBC SBC+opt+WD models 15000 12000 10000 12,000K

21. Temperatures from HST UV spectroscopy Spectral Fits by Boris Gansicke Uncertainties ~ 1000K GW LibJan17, 2002STIS15,400 V455 AndOct 24, 2002STIS (snap)10,500 SDSS2205+11 May 23,2005SBC15,000 SDSS0131-09 Jun 18, 2005SBC14,500 SDSS1610-01 Jun 30, 2005SBC14,500 PQ AndSep 13, 2007SBC12,000 SDSS0745+45 Nov 1, 2007SBC16,500 SDSS0919+08 Nov 14, 2007SBC13,500 SDSS1339+48 Jan 25, 2008SBC12,500 Object Date Instrument Temp (K) SDSS1507+52 Littlefair et al 2007 eclipse phot 11,000

22. Latest ZZ Cet instability strip (Gianninas, Bergeron, Fontaine, 2009) High mass DA WDs can get up to ~14000K log g T eff (K) Is the T difference a Mass difference?

23. (Arras, Townsley & Bildsten 2006, ApJ, 643, L119) Helium Abundance < 0.38 Instability Strip like ZZ Ceti stars @11000-12000K Helium abundance > 0.38 Additional instability strip @ 15000K Helium Abundance > 0.48 Strips merge into a wide strip 11000-16000K Is the difference based on mass and evolution? Is it a Composition Difference?

24. Past HST observations show CVs with WDs T’s that should place them in the instability strip but they don’t show pulsations Of 7 WZ Sge stars with WD = 12-16000K, no obvious pulsations in EG Cnc, LL And, AL Com, HV Vir, WX Cet, VY Aqr, EF Peg Is this lack of data or lack of pulsations? Another part of the enigma:

25. STIS data on EG Cnc T=12,300K WD Szkody, Gansicke, Sion & Howell, 2002, ApJ, 574, 950

26. Optical data on SDSS 1339+48 - telescope and cadence matter 1.2m, 70s int 3.6m, 20s int

27. Further Clues come from the pulsation analysis... The first 4 observations were classic cases: UV periods same as optical UV/opt amplitude ~ 6-17 as predicted by theory

28. GW Lib HST-STIS Szkody, Gansicke, Howell, Sion 2002, ApJ Orb 1 Orb 2 Orb 4 Orb 3

29. Szkody et al. (2007, ApJ, 658,1188) P=214s P=608s P=576s in 2005

30. DA model for log g=8 by Atsuko Nitta with (Szkody et al. ApJ 658, 2007) T eff = 14,500 T eff = 12,500 UV+optical data allow fit to mode SDSS1610-01 608s pulsation T from spectrum = 14,500K

31. Then it got complicated: PQ And showed optical but no UV pulse SDSSJ0745 and others showed no pulse in opt or UV!

32. 1285s 2337s UV/Opt amplitude < 1! l=3?

33. GW Lib650,370,230 6-17 SDSS0131581,213,792136 SDSS1610608,221 6 SDSS2205575,475,3305756 PQ And c1263none<1 SDSS07451166-1290none SDSS0919260none SDSS1339 c642230,210? V455 And c419,336,310No obs SDSS1514571none REJ1255+26 1344,1236, 654,582 none<2 Object Opt Periods (s) UV Periods (s) UV/opt amp Summary of Pulsations

34. Optical Data prior to HST on Long Period Pulsator SDSS0745+4538 Light curvesFourier transforms

35. But in 2007: Orb P

36. SDSS0745+4538 2005-2006 2007 30 Oct 31 Oct 1 Nov 2 Nov 6 peaks/ 7200 sec = pulsation1.5 peaks/ 7200s = orbital

37. This accreting pulsator stopped pulsating between 2006 -2007! No respectable ZZ Ceti stops pulsating! [Anjum] The Catalina Sky Survey detected an outburst of SDSS0745+45 in Oct 2006 - did this matter? BUT

38. Unknown SOB occurred or Accreting pulsators have changing temperature, mass, angular momentum & surface composition ??? We need long-term observations for each pulsator! Possible Reasons for non- detection of pulsations:

39. GW Lib P = 650, 376, 236s Long monitoring shows that amplitudes can change (Van Zyl et al 2004, MNRAS)

40. Patrick Woudt SAAO long term monitoring of pulsator SDSS0131 From Szkody et al. ApJ 658, 1188, 2007 HST data June 2005 showed P=214s 214s 600s 335s

41. 3 major questions: 1) where is the instability strip for accreting pulsators? 2) what are the affects of accretion and outbursts? 3) is there any hope of pulling out mass, spin, etc?

42. Known Outbursts of Accreting Pulsators: PQ And (1938, 1967, 1988) GW Lib (1983, 2007) V455 And (2007) REJ1255+26 (1994) SDSS0745+45 (2006) SDSS0804+51 (2006)

43. Pulsation Period: Means of measuring T eff ? Mukadam et al. 2005

44. AAVSO data plotted by Matt Templeton Apr12 07 more GALEX May, June 2008 May,June 07 GALEX WIYN,APO May29,June 1 (387+/-5s? 19 mma) ULTRACAM (Copperwheat et al. 2009) GW Lib outburst

45. 13 months past outburst

46. A new periodicity is apparent 1 yr after outburst but not seen in UV ??? Before outburst: P=650, 370, 230s After outburst: P=1145+/-3 s Mar-June 2008 Copperwheat et al. 2009 MNRAS: Mar-Apr 1154+/-10s June 21 296s 1145s

47. CTIO 4m spectrum: Tom Harrison Apr 2008 Boris fit: T wd = 23,000K, log g=8.46 Quiescent WD T=15,000K V~16.3

48. V V455 And 2007-2009 AAVSO data plotted by Matt Templeton Sept 07 V455 And

49. Pre SOB Post SOB spinpulse? 1 yr past outburst:

50. 2 systems like this now known Phot P ~ 43 min Spect P = 85 min Spectra look like pulsators 0804+51 Pre-outburst photometry

51. Pavlenko Dec 2008 astro-ph Feb 06 Oct 06 Feb 07 Jan 08May 08

52. Oct 06 Feb 07 Pavelenko astro- ph 2008 Jan 08 Pulse P = 756s Did this system move INTO the instability strip after outburst? No pulsations in pre-outburst data

53. Past HST data Model 10,500K WD Maybe we can solve this in the next HST cycle with T, mass measurements 12500K COS time for GW Lib (high T) and V455 And (low T)

54. 3 major questions: 1) where is the instability strip for accreting pulsators? 2) what are the affects of accretion and outbursts? 3) is there any hope of pulling out mass, spin, etc?

55. Coordinated Campaign on SDSS1610-01 May 2007

56. Nice power spectrum but no additional pulsation periods!

57. If triplet is due to WD rotation : P=4.8days! van Zyl et al (2004) found similar result for GW Lib: splitting implied rotation P =7.3d! other causes of splitting - magnetic field?

58. 3 major questions: 1) where is the instability strip for accreting pulsators? 11,000 - 16,000K 2) what are the affects of accretion and outbursts? pulsations disappear, mode splitting 3) is there any hope of pulling out mass, spin, etc? difficult - need many more modes and data

59. What remains to be done to make progress: Observationally : find the rest of the pulsators (SDSSVI,VII, lit) fill in the temperatures of the instability strip monitor GW Lib and V455 And as WDs return to T quies have more campaigns to look for multiplet structure Theoretically: find a way to make pulsations disappear explain fine structure in pulse include WD spin, composition in models