X-ray and Near-IR Studies of Be/X-ray Binaries

1. X-ray and Near-IR Studies of Be/X-ray Binaries SachindraNaik Physical Research Laboratory, Ahmedabad

2. X-ray Binaries • Most brightest X-ray sources in the sky • Two stars in the system rotate around the common center of mass • The compact object is either a White Dwarf, Black Hole or a Neutron star • Classified into two types : High Mass X-ray Binaries (HMXBs) and Low Mass X-ray Binaries (LMXBs). SachindraNaik, PRL

3. X-ray Binaries SachindraNaik, PRL

4. Be/X-ray Binaries Be/X-ray binaries form the largest subclass (about 2/3) of HMXBs. The orbit of the compact object is wide and highly eccentric, limiting interactions with the circumstellar disk to the periastron passage. Be/X-ray binaries are generally quiescent. X-ray outbursts seen in these objects are due to interactions between the compact object and the circumstellar disk of Be star. • Among the ~96 HMXB pulsars, 67% of the identified systems are Be/X-ray systems.

5. Be/X-ray Binaries SachindraNaik, PRL

6. Binary X-Ray Pulsars • Flux of matter falling from stellar wind or/and Roche lobe overflow • Interaction of matter with the magnetic field at the magnetospheric radius • Formation of accreting slabs or columns of matter at the polar caps : Source of X-ray radiation • Transport of X-ray radiation through a strongly magnetized plasma SachindraNaik, PRL

7. Pulse Profiles of X-ray Pulsars Single-peaked or double peaked, depending on the visibility of magnetic poles of the neutron star. Sachindra Naik, PRL

8. Pulse Profiles of Persistent HMXB Pulsars SMC X-1, HMXB, PP- 0.71s Cen X-3, HMXB, PP- 4.8s LMC X-4, HMXB, PP-13.5s Raichur & Paul 2006 Li-Wei et al. 2010 Naik & Paul 2004

9. Pulse Profiles of Persistent HMXB Pulsars GX 301-2, HMXB, PP- ~681 s 4U 1538-52, HMXB, PP- 528.24 s Suchy et al. 2012 Robba et al. 2001

10. Pulse Profiles of accreting pulsars in 20-35 keV Bildsten et al. 1997

11. Pulse Profiles of Transient HMXB Pulsars 1A 1118-61 : Spin Period = 407.5 s, Maitra et al. 2012 GX 304-1 : Spin Period = ~272 s, Devasia et al. 2011

12. Pulse Profiles of Transient HMXB Pulsars LS V + 44 17: Spin Period ~ 205 s. Usui et al. 2012 GRO J1008-57: Spin Period = ~93.74 s Naik et al. 2011

13. Pulse Profiles of Transient HMXB Pulsars EXO 2030+375: Spin Period = 41.41 s Naik et al. 2012

14. Pulse Profiles of A0535+262 Outburst Quiescent Mukherjee & Paul 2005 Naik et al. 2008

15. Pulse Profiles of A0535+262 at different luminosity levels Bildsten et al. 1997

16. Broad-band Spectra in XRBPs can be characterized by following components • Continuum Spectrum • Line of sight absorption • Soft excess • Emission line features • Cyclotron resonance features Endo et al. 2000 All these components vary with respect to pulse phase and orbital phase! SachindraNaik, PRL

17. Broad-band Spectra in XRBPs Dal Fiume et al. 1998 SachindraNaik, PRL

18. Cyclotron lines in accretion powered X-ray pulsars Cyclotron resonance features (CRFs) in X-ray pulsars are due to resonant scattering of the line of sight X-ray photons against electrons (and protons) embedded in magnetic fields (1011–1013Gauss). A method to estimate the magnetic field of X-ray pulsars [Ea = 11.6 x B12(1+z)-1keV] (where B12 is in the units of 1012 Gauss)

19. Cyclotron lines with Suzaku (A0535+262 & Her X-1) Ea ~ 45 keV Terada et al. (2006); Naik et al. (2008) Ea ~ 36 keV, Enoto et al. (2008) SachindraNaik, PRL

20. Luminosity Dependent Change of Ea(Ginga Obs. Of 4U0115+63) Recurrent transient pulsar, sp=3.6 s, op=24.3 d, D ~ 7 kpc 1990 Obs. L = 14×1037 erg/s 1991 Obs. L = 2×1037 erg/s 11.3 & 22 keV 17 keV Mihara et al. 2004 SachindraNaik, PRL

21. Luminosity Dependent Change of Ea A0535+262 : Caballero et al. 2007 4U0115+63 : Nakajima et al. 2006 SachindraNaik, PRL

22. Partial covering absorption model for Be/X-ray Binary Pulsar (GROJ1008-57) Pulse Period ~ 93.74 s, Orbital Period ~ 260 days Naik et al. 2011 SachindraNaik, PRL

23. Partial covering absorption model for Be/X-ray Binary Pulsar 1A1118-61 SachindraNaik, PRL Maitra et al. 2012

24. Partial covering absorption model for Be/X-ray Binary Pulsar EXO 2030+375 with ionized absorber with neutral absorber Naik et al. 2012

25. Be/X-ray Binary Pulsars (X-ray Properties) • Regular outbursts (Type I) are seen during periastron passage • of the neutron star • Pulse profiles are characterized by the presence of narrow dips • during the outbursts. • Dips are found to be strongly energy dependent. • Broad-band spectra of these transient pulsars are better • explained in terms of partial covering high energy cut-off • power law model. • Pulse phase resolved spectroscopy confirms the presence of • additional column density at the dip phases. • Dips are explained in terms of absorption in the accretion • stream that is phase locked with the neutron star. Sachindra Naik, PRL

26. Be/X-ray Binary Pulsars (IR/Optical Properties) SachindraNaik, PRL

27. Optical/Near-IR observations of Be/X-ray Binaries Episodes of circumstellar disc loss : A0535+262 Haigh et al. (1999) A giant X-ray flare in early 1994, accompanied by a fading in optical and IR bands and a reduction in equivalent width of Hα line was also detected in A0535+262 (Clark et al. 1998).

28. Optical/Near-IR observations of Be/X-ray Binaries Episodes of circumstellar disc loss : V635 Cas (γCas) Cycle AStarting with the disc-less state in 1992 and lasting until disc-less state in 1997. Two outbursts in May 1994 and Nov. 1995. Cycle B: Disc-less state in 1997. Type II outburst in March 1999. Negueruela et al. (2001)

29. Near-IR observations of Be/X-ray binaries Observation campaign carried out to understand the X-ray and near-IR properties of selective Be/X-ray binaries at various orbital phases. Observations were carried out using the 1.2 m telescope at Mt. Abu. Photometric and spectroscopic observations in J (1.08-1.34 μm), H (1.52-1.74 μm), K (2.01-2.2 μm) bands using the Near-Infrared Imager/Spectrometer with a 256×256 HgCdTe NICMOS3 array. Sachindra Naik, PRL

30. Near-IR observations of Be/X-ray Binary A0535+262 A0535+262 is a ~103 s Be/X-ray binary pulsar. The binary companion HDE 245770 is an O9.7-B0 IIIe star in a relatively wide eccentric orbit (e=0.47) with an orbital period of ~111 days. SachindraNaik, PRL Naik et al. 2012

31. Near-IR observations of Be/X-ray Binary A0535+262 SachindraNaik, PRL Naik et al. 2012

32. Near-IR observations of Be/X-ray Binary A0535+262 Naik et al. 2012 SachindraNaik, PRL

33. Be/X-ray Binary 4U 0352+30/X Persei X Persei is a bright Be star which is the optical/IR counterpart of X-ray pulsar 4U 0352+30 (pulse period ~835 s). Orbit of the binary system is moderately eccentric (e=0.11) with orbital period of ~250 d. Episode of complete disc loss during 1988 May–1989 June, characterized by significant optical fading by ~0.6 magnitude. Similar optical fading was also seen in 1994 Oct. – 1995 Oct. Norm. Hα (6563 Å) spectra of X Per (1987 Sep. – 1995 Feb. (Clark et al. 2001), part of 13 years of monitoring of X Per. SachindraNaik, PRL

34. Near-IR observations of X Persei SachindraNaik, PRL Mathew, Banerjee, Naik, Ashok et al. 2012a, 2012b

35. Near-IR observations of X Persei

36. Near-IR observations of X Persei

37. Near-IR observations of X Persei Line equivalent widths Line flux Possibility of an X-ray outburst in future???

38. Near-IR observations of X Persei Sachindra Naik, PRL

39. Line emitting regions in Be star (δSco) • H-band (λ0 = 1.65 μm, Δλ = 0.28 μm) • K-band (λ0 = 2.18 μm, Δλ = 0.4 μm ) • Hαλ 6563 Å, He I λ2.0583 μm, Br γλ2.1657 μm Millan-Gaber et al. (2010) SachindraNaik, PRL

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41. Emission lines in Be stars FeII 5317Å profiles of δ Cen. Dark areas denote σ < 0 and bright ones σ > 0. Hanuschik et al. (1995)

42. X-ray & Optical observations of Be/X-ray Binary A0535+262 Camero-Arranz et al. 2012 SachindraNaik, PRL