The Downside of EF Eridani

1. The Downside of EF Eridani Frederick M. Walter Stony Brook University • There’ve been strange things done to this former sun by the nearby white dwarf star. • The twisted yield of the magnetic field draws in matter from afar. • The CV crowd would gasp aloud if they could ever see • The very queer magnetosphere of EF Eridani.

2. The SMARTS EF Eri Team Tom Harrison (UNM) Steve Howell (NOAO) Stella Kafka (CalTech) Koji Mukai (GSFC) Axel Schwope (AIP) Paula Szkody (UW)

3. The Faces of EF Eridani 2 April 2008 29 August 2008

4. EF Eridani - a History • Counterpart of 2A 0311-227 • First detected in 1974 by Ariel V • Identified as a polar in 1978 • Bright soft X-ray source 1978 - 1997 • First reported low state: 1990 • Extended low state 1997 - 2009 • Brief high states in 2006, 2008 (2), 2009

5. EF Eridani: Characteristics • A polar • Orbital period: 81 minutes • Non-eclipsing • Primary: cool WD, T~ 9500K • Magnetic field ~ 12 MG • Secondary: unseen, M<0.05M Image: P. Marenfeld/NOAO

6. EF Eridani - Low State “It’s dead, Jim” Harrison et al. 2004

7. EF Eridani - Low State SMARTS 1.5m, 19 October 2004 Howell et al. 2006

8. EF Eridani - Light Curve SMARTS 1.3m/ANDICAM (plus some 0.9m)

9. EF Eridani - Phased Light Curve 21 August 2003 - 11 March 2009

10. Low State Ephemeris Based on the low state B light curve through August 2008 min = JD 2453716.61108 (heliocentric) P = 0.05626586 days (adopted) min = phase 0.41 in the Bailey et al. (1982) ephemeris

11. Light Curve Stability Colors represent different observing seasons

12. Light Curve Instability B~0.2 dm/dt ~1.e-14 M/yr Mini-accretion event - December 2006

13. EF Eridani - Phased Light Curve 10-13 December 2006

14. EF Eridani - Phased Light Curves Sinusoidal Fits I: 0.07 0.01 min: 0.73 0.02 V: 0.072  0.003 min: 0.05  0.01 B: 0.080  0.001 min: 0.994  0.002 U: 0.086  0.006 min: 0.01 0.01 21 August 2003 - 11 March 2009

15. EF Eridani - Phased Light Curves Sinusoidal Fits K: 0.57 0.02 min: 0.48 0.02 H: 0.70 0.03 min: 0.60  0.01 J: 0.35  0.06 min : 0.55  0.03 21 August 2003 - 11 March 2009

16. EF Eridani - Phased Light Curves Cyclotron Hot Spot

17. Wavelength Dependence Low state light curve UV points from Szkody et al. 2006

18. H from the Secondary? • It’s not quite dead, the spectra said, though the Hydrogen lines are weak • But they swerve and they bend and the velocity tends to imply a binary beat. • The near-infrared leads one instead to see that the donor is small • And the hydrogen plumes ought to consume the secondary in no time at all.

19. 5 years of low state H SMARTS 1.5m RC spectrograph

20. H on Small Telescopes. II CTIO 4.0m Feb 10-13 2008 Red: HBlue: H

21. H on a Big Telescope Gemini South/ GMOS 16 Feb 2009

22. Low State H- Trailed Spectrum GMOS-S 16 February 2009 70 x 60 seconds

23. Low State H Doppler Tomogram GMOS-S 16 February 2009 70 x 60 seconds • Caveats: • Relation of photometric phase to binary phase unknown • System  velocity unknown

24. The Last High State B mag; duration about 75 days • It continues today to perplex ’bout the way that the wind interacts with such passion. • Still it brightens some nights, at least at first sight, in a transient and tremulous fashion. • When it increases its light and the X-rays get bright you may think that it’s gonna stay high, • So you contact the team and push on with your scheme but in 2 months its gone from the sky.

25. H in the high state SMARTS/CTIO 1.5m RC

26. All Velocities +: high o: low (GMOS) -: low (4m)

27. High/Low State Comparison

28. Summary. I. • EF Eri has a stable low state. • The hot spot dominates at UBV • There are occasional mini-accretion episodes, with B up to 0.2 mag • Cyclotron emission dominates at JHK • No intermediate state has been seen. • The high state and low state H velocities • and tomograms show similarities … and differences. • H is not from the secondary, but is from the far side of the center of mass.

29. Summary. II. The secondary remains unseen. Even in the low state, accretion (including cyclotron) dominates. EF Eri: all accretion, all the time!

30. There’ve been strange things done to this former sun by the nearby white dwarf star. The twisted yield of the magnetic field draws in matter from afar. The CV crowd would gasp aloud if they could ever see The very queer magnetosphere of EF Eridani. It’s not quite dead, the spectra said, though the Hydrogen lines are weak But they swerve and they bend and the velocity tends to imply a binary beat. The near-infrared leads one instead to see that the donor is small And the hydrogen plumes ought to consume the secondary in no time at all It continues today to perplex ‘bout the way that the wind interacts with such passion. Still it brightens some nights, at least at first sight, in a transient and tremulous fashion. When it increases its light and the X-rays get bright you may think that it’s gonna stay high, So you contact the team and push on with your scheme but in 2 months its gone from the sky. There’ve been strange things done to this former sun by the nearby white dwarf star. The twisted yield of the magnetic field draws in matter from afar. The CV crowd would gasp aloud if they could ever see The very queer magnetosphere of EF Eridani.

31. High/Low State Comparison