LONDON - April 2006 1

Persistent and TransientBlank Field Sources

A. Treves Insubria University, Italy

S. Campana Brera Observatory, Italy

M. Chieregato Insubria University, Italy – Zürich University, Switzerland

T. Nelson Wisconsin University

M. Orio Torino, Italy – Wisconsin University

LONDON - April 2006 2

Dim Isolated Neutron Stars (DINS) Residual Internal Energy

Interaction with the surrounding

N ~ 108 – 109

LONDON - April 2006 3

ROSAT – DINS

Blank Field Sources Low X-ray Luminosity: Lx ~ 1030 erg/s T < 100 eV d ~ 100 pc P ~ 5 – 10 s Absorption lines < 1 KeV

LONDON - April 2006 4

Outline of the Contribution BFS in the ROSAT HRI Wavelet Catalogue

(Chieregato et al., 2005, A&A 444, 69)

Progress in ROSAT BFS

Transient Blank Field Sources

Future perspectives

LONDON - April 2006 5

BFS from HRI Catalogue Blank Field Sources

fx > 2.7 x 10-13 erg/s

Nph>25

LONDON - April 2006 6

BFS – HRISource Flux 10-13

erg cm-2s-1

Prob.σ

Cts fx / fopt Opt.σ

0421-51persistent

6.5 14.0 742 >141 5.3

1357+18transient

3.5 4.2 112 >47 6.3

2007-48transient

3.0 4.3 55 >65 5.2

0433+15transient

2.9 4.2 34 >40 4.9

LONDON - April 2006 7

0421-57X-ray position and blue image

LONDON - April 2006 8

1357+18X-ray position and blue image

LONDON - April 2006 9

0421-57Spectral fits for PSPC observation

LONDON - April 2006 10

0421-57Power law spectral fits for PSPC observation

LONDON - April 2006 11

Progress in BSF – HRIReconsideration of 4 sources: 0433+15 is a fake 1357+18, 2007-48 are not spiky

X-ray (SWIFT – Campana) 1357+18 fx < 10-14 erg / s

Optical (WIYN – Orio) 1357+18 R > 23.4

LONDON - April 2006 12

If the two TBSF were real…

Total Number: THRI ~ 3 x 107 s Ω ~ 0.2 deg2

Isotropic N ~ 105 y -1

Extragalactic: unlikely

Gamma Ray Burst: unlikely

LONDON - April 2006 13

TBSF

Non Collapsed Companions: unlikely

White Dwarfs Neutron Stars

Relation with transient PSR?

Hiccups?

LONDON - April 2006 14

Progress

Search for BFS with fx ~ 10-14 erg / s

(Chandra, XMM, SWIFT)

X- and optical archives

LONDON - April 2006 15

What we expect(dreams?) DINS: accretion powered

TBFS

DINS cousins

Isolated Black Holes

Intermediate Mass Black Holes (ULX)