Identification of seven persistent low-luminosity pulsators. Ramanpreet Kaur University of Amsterdam

Transcription

1 Identification of seven persistent low-luminosity pulsators Ramanpreet Kaur University of Amsterdam Physics of neutron stars St Petersburg, Russia

2 Low-luminosity pulsators Slowly pulsating (Ps > 150s) Luminosity ergs -1 Persistent Initial studies expects them to be Be/X-ray binaries or Intermediate Polars (IPs). Present in the Galactic plane. However their nature is not yet known.

3 Different pulsators supergiant HMXB neutron star

4 Different pulsators supergiant HMXB neutron star LMXB

5 Different pulsators supergiant HMXB IP neutron star LMXB

6 What makes these sources special?

7 What makes these sources special? A

8 What makes our sources special?

9 What makes our sources special? Classical Be/X-ray binaries have moderately eccentric orbits (e> 0.3). Pfahl et al. (2002) proposed a class of Be/X-ray binaries which has low-eccentricities (e<0.2) and long orbital periods (> 30 d). It is possible only if these eccentricities are primordial. Which means that these sources would have formed in a different type of supernova explosion without or with a small kick to the neutron star. e.g. X-Per/4U (837s). Proposed sources - RXJ (Haberl et al. 1998a, 1998b), RX J , RX J (Reig et al. 1999). Source name Pulse period SAX J s SAX J s AX J s AX J s AX J s AX J s AX J s

10 Selection criterion ASCA and BeppoSAX Galactic plane surveys Pulse periods > 150s Hard X-ray spectrum (Γ 1.0) X-ray luminosity = ergs -1 These selections helped us to exclude anomalous X-ray pulsars, LMXB pulsars and to some extend IPs also.

11 Observations Chandra - to identify X-ray counterparts XMM-Newton - spectral and timing analysis ESO-NTT imaging - to identify nearinfrared counterparts ESO-VLT nir spectroscopy - to study the near-infrared counterparts.

12 Chandra SAX J BeppoSAX error circle

13 Chandra SAX J BeppoSAX error circle

14 ESO-NTT (NIR) SAX J Chandra error circle

15 XMM-Newton

16 XMM-Newton SAX J

17 XMM-Newton SAX J

18 XMM-Newton SAX J

19 X-ray timing SAX J Ps 170s Spin period derivative = 6.34 x 10-9 s/s

20 X-ray timing SAX J Ps 170s Spin period derivative = 6.34 x 10-9 s/s

21 SAX J NIR imaging Supergiant or a O-type star - > outside the Galaxy late-type ms star < 1.3 kpc. ms B-type star - > 4 9 kpc. late-type giant - > 2 11 kpc.

22 SAX J Spin Ps X-ray Spectral period derivative spectra type LMXB HMXB IPs

23 SAX J Spin Ps X-ray Spectral period derivative spectra type LMXB HMXB IPs

24 SAX J Spin Ps X-ray Spectral period derivative spectra type LMXB HMXB IPs

25 SAX J Spin Ps X-ray Spectral period derivative spectra type LMXB HMXB IPs

26 SAX J Spin Ps X-ray Spectral period derivative spectra type LMXB HMXB IPs

27 AX J Spin Ps X-ray Spectral period derivative spectra type LMXB HMXB IPs

28 normalized counts SAX J SAX J B13 B12 B Hip (G2V) wavelength (microns)

29 SAX J B-Gamma 1.4 SAX J normalized counts Hip (G2V) wavelength (microns)

30 normalized counts AX J AX J B13 B12 B Hip G IV wavelength (microns)

31 Stellar spectral classification - Richard O. Gray and Christopher J. Corbally

32 Stellar spectral classification - Richard O. Gray and Christopher J. Corbally

33 Be/X-ray binary

34 Be/X-ray binary Reig 2011

35 Conclusions. Sources (SAX J , AX J ) which showed H absorption lines are either HMXBs or IMXBs. AX J is likely HMXBP. Three of our sources (AX J , AX J , AX J ) are likely IPs. SAX J likely IP or LMXB. It is possible that the three HMXBs belong to the persistent Be/X-ray binaries class. However they could also well be members of some other unexplored class of sources at lowluminosities.