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Multi-wavelength study of X-ray emitting A- and B-stars testing the companion hypothesis

Multi-wavelength study of X-ray emitting A- and B-stars testing the companion hypothesis Beate Stelzer Osservatorio Astronomico di Palermo N. Huelamo, S. Hubrig (ESO Chile) G. Micela (OA Palermo) H. Zinnecker (AI Potsdam) E. Guenther (TLS Tautenburg). Shock-excited winds.

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Multi-wavelength study of X-ray emitting A- and B-stars testing the companion hypothesis

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  1. Multi-wavelength study of X-ray emitting A- and B-stars testing the companion hypothesis Beate Stelzer Osservatorio Astronomico di Palermo N. Huelamo, S. Hubrig (ESO Chile) G. Micela (OA Palermo) H. Zinnecker (AI Potsdam) E. Guenther (TLS Tautenburg)

  2. Shock-excited winds No X-rays dissipation of magnetic fields fully radiative rad. core + convective envelope fully convective a2-dynamo ? turb. dynamo ? solar-like a-dynamo (in overshoot-layer) B5 A7 M3 O B A F G K M L lg(Lx /Lbol )= -3....-4 ? kT ~ ? Rot.-Act. Relation ? lg(Lx /Lbol )= -3....-4 kT ~ 1.0 keV Rotation-Activity Relation lg(Lx /Lbol )= -7 kT ~ 0.5 keV X-rays from late-B and early-A type Stars ? Dynamo should break down at SpT ~ A7...F3, But X-rays observed from late-B/early-A stars (Caillault & Zoonematkermani 1989, Schmitt et al. 1993, Berghöfer et al. 1996, Hünsch et al. 1998....) X-rays generated by (unknown) late-type companion stars ???

  3. WANTED: • Stars of early Sp.type (A,B) • with companion of late Sp.type (G, K, M) • Lindroos systems (Lindroos 1986) • = early-type star • with post-TTS companion • X-ray observations with ROSAT: • (Schmitt et al 1993; Huelamo et al. 2000) • companions emit X-rays • ~ 1/3 of the primaries detected • many systems not resolvable(ROSAT HRI 5“; ROSAT PSPC 20“) Huelamo et al. 2000: X-rays from Lindroos systems Testing the companion hypothesis: Early-type stars with companions identified by their Hardness Ratio ?

  4. Origin of X-rays from intermediate-mass stars Observational Strategy • Adaptive Optics observations (Search for cool companions) • X-ray follow-up obs. with high spatial resolution (Pinpointing the X-ray source) • IR spectroscopy of B/A stars (Search for closer companions) • IR spectroscopy of companions (Nature of the companions ?)

  5. Origin of X-rays from intermediate-mass stars Observational Strategy • Adaptive Optics observations (Search for cool companions)ADONIS/3.6m ESO Hubrig et al. (2001) 49 X-ray B-stars 19 companions Huelamo et al. (2001) 3 X-ray B-stars 1 companions Shatsky & Tokovinin(2002) 115 OB-stars 96 companionsNICS/3.6m TNG,La Palma3 nights in Aug 03 and Jan 04 (23 A-stars in northern hemisphere) • X-ray follow-up obs. with high spatial resolution (Pinpointing the X-ray source) • IR spectroscopy of B/A stars (Search for closer companions) • IR spectroscopy of companions (Nature of the companions ?)

  6. Origin of X-rays from intermediate-mass stars Observational Strategy • Adaptive Optics observations (Search for cool companions)ADONIS/3.6m ESO Hubrig et al. (2001) 49 X-ray B-stars 19 companions Huelamo et al. (2001) 3 X-ray B-stars 1 companions Shatsky & Tokovinin(2002) 115 OB-stars 96 companionsNICS/3.6m TNG,La Palma3 nights in Aug 03 and Jan 04 (23 A-stars in northern hemisphere) • X-ray follow-up obs. with high spatial resolution (Pinpointing the X-ray source)Chandra/ACIS: ~ 1“Stelzer et al. 2003, A&A 4075 B-stars + ca. 20 A/B-stars from the Chandra archive • IR spectroscopy of B/A stars (Search for closer companions) • IR spectroscopy of companions (Nature of the companions ?)

  7. Origin of X-rays from intermediate-mass stars Observational Strategy • Adaptive Optics observations (Search for cool companions)ADONIS/3.6m ESO Hubrig et al. (2001) 49 X-ray B-stars 19 companions Huelamo et al. (2001) 3 X-ray B-stars 1 companions Shatsky & Tokovinin(2002) 115 OB-stars 96 companionsNICS/3.6m TNG,La Palma3 nights in Aug 03 and Jan 04 (23 A-stars in northern hemisphere) • X-ray follow-up obs. with high spatial resolution (Pinpointing the X-ray source)Chandra/ACIS: ~ 1“Stelzer et al. 2003, A&A 4075 B-stars + ca. 20 A/B-stars from the Chandra archive • IR spectroscopy of B/A stars (Search for closer companions)Pilot study NTT/SofI and 2.2m Calar Alto/MAGIC (PI Huelamo) • IR spectroscopy of companions (Nature of the companions ?)

  8. Origin of X-rays from intermediate-mass stars Observational Strategy • Adaptive Optics observations (Search for cool companions)ADONIS/3.6m ESO Hubrig et al. (2001) 49 X-ray B-stars 19 companions Huelamo et al. (2001) 3 X-ray B-stars 1 companions Shatsky & Tokovinin(2002) 115 OB-stars 96 companionsNICS/3.6m TNG,La Palma3 nights in Aug 03 and Jan 04 (23 A-stars in northern hemisphere) • X-ray follow-up obs. with high spatial resolution (Pinpointing the X-ray source)Chandra/ACIS: ~ 1“Stelzer et al. 2003, A&A 4075 B-stars + ca. 20 A/B-stars from the Chandra archive • IR spectroscopy of B/A stars (Search for closer companions)Pilot study NTT/SofI and 2.2m Calar Alto/MAGIC (PI Huelamo) • IR spectroscopy of companions (Nature of the companions ?) • proposed for VLT (PI Hubrig)

  9. Sep. A – B: 2.3“ IR and X-ray images of late B-type MS Stars HD 1685 ADONIS ESO/3.6m K-band (Hubrig et al. 2001) Chandra ACIS-I (Stelzer et al. 2003) X-rays from A + B Offset X1 – A = 0.1“ Offset X2 – B = 0.1“

  10. ACIS-S ADONIS C A Huelamo, unpublished IR and X-ray images of late B-type MS Stars The Lindroos system HD 113703 X-rays from companions B + C No X-rays from primary A Result: Out of 11 systems with B-type MS-primary and IR “companion“ X-rays are detected from 10 (+1?) IR companions, all AO discovered IR objects emit X-rays 7 B-Stars even closer companions ? (1 is a SB) 12/15 HAeBe stars detected

  11. X-ray Spectra observed Chandra simulated Chandra based on ROSAT parameters ROSAT temperature too low, luminosity too high Spectrum needed to derive plasma properties ! X-ray spectra of of A/B-stars and of (cool) companions different ?

  12. Chandra data of MS B-stars and companions Lx / Lbol ratio according to Chandra Wind-driven stellar X-rays Upper limits for undetected B-stars below the value for wind-driven X-rays

  13. Chandra data of MS B-stars and companions ROSAT data of MS B-stars (companions unresolved) Lx / Lbol ratio according to Chandra Wind-driven stellar X-rays ROSAT: 10 sources Chandra: 18 sources + 8 upper limits

  14. Chandra data of MS B-stars and companions ROSAT data of MS B-stars (companions unresolved) Chandra data of HAeBe stars Lx / Lbol ratio according to Chandra Wind-driven stellar X-rays • Some HAeBe have low-mass companions • Intermediate Lx/Lbol (uncertain Lbol !)

  15. ----A------------------B-------------------O----- VB SB Singles? Lx , Lbol from Berghöfer et al. (1996) and Hünsch et al. (1998) Lx / Lbol ratio according to ROSAT ~ 2/3 of O-,B-,A-stars detected in the RASS are binaries ! See Poster E.29 (Schröder & Schmitt)

  16. ----A------------------B-------------------O----- VB SB Singles? Observed in IR with AO Lx , Lbol from Berghöfer et al. (1996) and Hünsch et al. (1998) Lx / Lbol ratio according to ROSAT 23 single A-type stars detected in the RASS observed with AO

  17. 30“ 10“ 15“ 20“ ghosts IR K-band images of HR7826 (SpT A3 V) No reports on binarity. TNG/NICS+AdOpt: Several faint objects within 30“ 2MASS: Several faint objects within 30“ • all 2 MASS sources recovered • further objects within 10“, unidentified in 2MASS

  18. 10“ 15“ 20“ 30“ IR K-band images of HR8307 (SpT A0 V) • 83 pc • lgLx = 30.6 (RASS; Huensch et al. 1998) • no companion detected in Speckle survey (McAlister et al. 1987)at detectable separation of 0.61“....1.36“ depending on P.A. TNG/NICS+AdOpt: double source, separation ~ 2“ 2MASS: One source at 29“ separation

  19. IR spectrum of HD 32964 HD 32964A SB: 2 components of ~2.4 Msun each HD 32964B Lindroos companion at 53“ (K5 V; probably unrelated) HD 32964C Adaptive Optics companion at 1.6“ The only Chandra X-ray source is HD32964 C.

  20. Comparison Spectra: IR spectrum of HD 32964 HD 32964A SB: 2 components of ~2.4 Msun each HD 32964B Lindroos companion at 53“ (K5 V; probably unrelated) HD 32964C Adaptive Optics companion at 1.6“ The only Chandra X-ray source is HD32964 C. Spectrum of the Adaptive Optics companion HD32964C.

  21. Baraffe et al. (1998) Undetected in X-rays Detected in X-rays IR CMD for „Companions“ Chandra sample 11 MS stars have 15 „companions“ (12 X-ray detected) 15 HAeBe stars have 9 „companions“ (4 X-ray detected) „Companions“ with .... ....no J-mag 7 ....not on PMS 5 ....likely on PMS 12

  22. Summary • Adaptive Optics observations: ADONIS/3.6m ESO Hubrig et al. (2001) 40 % of X-ray B-stars have companions at 0.2-14“NICS/3.6m TNG,La Palmadata in analysis several new objects in 23 X-ray A-stars • X-ray follow-up observations of AO targets:Chandra ACIS7(11) B-stars emit X-rays; X-ray properties similar to AO companions sub-arcsecond companions ? • IR spectroscopy of Chandra-detected B/A stars Pilot studies underway (NTT and Tautenburg): AO companions rediscovered; observations need careful setup

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