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. X-rays from late-B and early-A type Stars ? Shock-excited winds No X-rays OBAFGKMLOBAFGKML dissipation of magnetic fields M3A7 B5 solar-like  -dynamo (in overshoot-layer)   -dynamo ? turb. dynamo ? fully radiative rad. core + convective envelope fully convective lg(L x /L bol )= -7 kT ~ 0.5 keV lg(L x /L bol )= -3....-4 kT ~ 1.0 keV Rotation-Activity Relation lg(L x /L bol )= -3....-4 ? kT ~ ? Rot.-Act. Relation ? 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. Testing the companion hypothesis: Huelamo et al. 2000: X-rays from Lindroos systems Early-type stars with companions identified by their Hardness Ratio ? 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“)

4. 1.Adaptive Optics observations (Search for cool companions) 2.X-ray follow-up obs. with high spatial resolution (Pinpointing the X-ray source) 3.IR spectroscopy of B/A stars (Search for closer companions) 4.IR spectroscopy of companions (Nature of the companions ?) Origin of X-rays from intermediate-mass stars Observational Strategy

5. 1.Adaptive Optics observations (Search for cool companions) ADONIS/3.6m ESO Hubrig et al. (2001)49 X-ray B-stars19 companions Huelamo et al. (2001)3 X-ray B-stars1 companions Shatsky & Tokovinin(2002)115 OB-stars 96 companions NICS/3.6m TNG,La Palma 3 nights in Aug 03 and Jan 04 (23 A-stars in northern hemisphere) 2.X-ray follow-up obs. with high spatial resolution (Pinpointing the X-ray source) 3.IR spectroscopy of B/A stars (Search for closer companions) 4.IR spectroscopy of companions (Nature of the companions ?) Origin of X-rays from intermediate-mass stars Observational Strategy

6. 1.Adaptive Optics observations (Search for cool companions) ADONIS/3.6m ESO Hubrig et al. (2001)49 X-ray B-stars19 companions Huelamo et al. (2001)3 X-ray B-stars1 companions Shatsky & Tokovinin(2002)115 OB-stars 96 companions NICS/3.6m TNG,La Palma 3 nights in Aug 03 and Jan 04 (23 A-stars in northern hemisphere) 2.X-ray follow-up obs. with high spatial resolution (Pinpointing the X-ray source) Chandra/ACIS: ~ 1“ Stelzer et al. 2003, A&A 407 5 B-stars + ca. 20 A/B-stars from the Chandra archive 3.IR spectroscopy of B/A stars (Search for closer companions) 4.IR spectroscopy of companions (Nature of the companions ?) Origin of X-rays from intermediate-mass stars Observational Strategy

7. 1.Adaptive Optics observations (Search for cool companions) ADONIS/3.6m ESO Hubrig et al. (2001)49 X-ray B-stars19 companions Huelamo et al. (2001)3 X-ray B-stars1 companions Shatsky & Tokovinin(2002)115 OB-stars 96 companions NICS/3.6m TNG,La Palma 3 nights in Aug 03 and Jan 04 (23 A-stars in northern hemisphere) 2.X-ray follow-up obs. with high spatial resolution (Pinpointing the X-ray source) Chandra/ACIS: ~ 1“ Stelzer et al. 2003, A&A 407 5 B-stars + ca. 20 A/B-stars from the Chandra archive 3.IR spectroscopy of B/A stars (Search for closer companions) Pilot study NTT/SofI and 2.2m Calar Alto/MAGIC (PI Huelamo) 4.IR spectroscopy of companions (Nature of the companions ?) Origin of X-rays from intermediate-mass stars Observational Strategy

8. 1.Adaptive Optics observations (Search for cool companions) ADONIS/3.6m ESO Hubrig et al. (2001)49 X-ray B-stars19 companions Huelamo et al. (2001)3 X-ray B-stars1 companions Shatsky & Tokovinin(2002)115 OB-stars 96 companions NICS/3.6m TNG,La Palma 3 nights in Aug 03 and Jan 04 (23 A-stars in northern hemisphere) 2.X-ray follow-up obs. with high spatial resolution (Pinpointing the X-ray source) Chandra/ACIS: ~ 1“ Stelzer et al. 2003, A&A 407 5 B-stars + ca. 20 A/B-stars from the Chandra archive 3.IR spectroscopy of B/A stars (Search for closer companions) Pilot study NTT/SofI and 2.2m Calar Alto/MAGIC (PI Huelamo) 4.IR spectroscopy of companions (Nature of the companions ?) proposed for VLT (PI Hubrig) Origin of X-rays from intermediate-mass stars Observational Strategy

9. IR and X-ray images of late B-type MS Stars HD 1685 X-rays from A + B Offset X 1 – A = 0.1“ Offset X 2 – B = 0.1“ ADONIS ESO/3.6m K-band (Hubrig et al. 2001) Sep. A – B: 2.3“ Chandra ACIS-I (Stelzer et al. 2003)

10. 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 ACIS-S ADONIS C A Huelamo, unpublished IR and X-ray images of late B-type MS Stars The Lindroos system HD 113703

11. X-ray Spectra simulated Chandra based on ROSAT parameters observed Chandra 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. L x / L bol ratio according to Chandra Chandra data of MS B-stars and companions Upper limits for undetected B-stars below the value for wind-driven X-rays Wind-driven stellar X-rays

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

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

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

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

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

18. IR K-band images of HR8307 (SpT A0 V) TNG/NICS+AdOpt: double source, separation ~ 2“ 2MASS: One source at 29“ separation 30“ 20“ 15“ 10“ 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.

19. IR spectrum of HD 32964 HD 32964ASB: 2 components of ~2.4 M sun each HD 32964BLindroos companion at 53“ (K5 V; probably unrelated) HD 32964CAdaptive Optics companion at 1.6“ The only Chandra X-ray source is HD32964 C.

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

21. 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-mag7....not on PMS5....likely on PMS12 Baraffe et al. (1998) Undetected in X-rays Detected in X-rays

22. 1.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 Palma data in analysisseveral new objects in 23 X-ray A-stars 2.X-ray follow-up observations of AO targets: Chandra ACIS 7(11) B-stars emit X-rays; X-ray properties similar to AO companions sub-arcsecond companions ? 3.IR spectroscopy of Chandra-detected B/A stars Pilot studies underway (NTT and Tautenburg): AO companions rediscovered; observations need careful setup Summary