Sources seen with INTEGRAL–ISGRI

Arash Bodaghee ISDC – Geneva ObservatoryCargèse, Corsica, April, 2006

Introduction

Population studies exist for soft X-ray surveys of the Milky Way (RXTE: Grimm et al., 2002). Now, INTEGRAL is filling in the gaps in the hard X- and γ-ray census of the galaxy (e.g. Lutovinov et al., 2004, Dean et al., 2005).

ISGRI: 10.7°×10.7° FOV, 0.7—2', 20—40/40—100 keV, all-sky survey (Bird et al., 2006).

So far, ISGRI has detected 326 sources, of which ∼100 were not previously known (≡ IGR).

Some IGR sources were followed-up by soft X-ray telescopes (e.g. XMM-Newton, Chandra, and RXTE) which provide:

access to the 1—10 keV portion of the spectrum (NH, Γ, and possible Fe lines).an improved position for the identification of counterparts at other wavelengths (especially important in the crowded galactic plane, bulge, and spiral arms).precise timing analysis for searching for spin and orbital periods, or QPOs.

⇒ These characteristics enable a more reliable source classification.

Classifications

Object classifications of all ISGRI and IGR sources detected so far.

7824%

299%

8025%

8025% 59

18%

326 ISGRI sources 120 IGR sources

6050%

3025%

2017%

76%

32%

Unclassified Misc. LMXB AGNHMXB

The ISGRI Universe

Longitude (l) vs. latitude (b) of all 326 ISGRI sources.

The ISGRI Universe

Longitude (l) vs. latitude (b) of all 326 ISGRI sources.

Spatial Distribution

Number of ISGRI sources (by type) per 10° bin of galactic longitude.

HMXBs are concentrated along the galactic plane and in the spiral arms, typical of a young stellar population.

LMXBs are found preferentially in the galactic bulge (and at high latitudes) as expected of an older population.

AGNs are distributed homogeneously.

Spatial Distribution

Number of ISGRI sources (by type) per 10° bin of galactic latitude.

HMXBs are concentrated along the galactic plane and in the spiral arms, typical of a young stellar population.

LMXBs are found preferentially in the galactic bulge (and at high latitudes) as expected of an older population.

AGNs are distributed homogeneously.

The ISGRI Milky Way

The Milky Way as viewed from above (spiral arm model from Vallée, 2002).

Absorption

Numerical distribution of NH reported for 205 ISGRI sources. IGR sources (40) are in red.

Absorption

Numerical distribution of NH reported for 165 ISGRI sources (excluding the 40 IGR sources which are in red.

Absorption

Numerical distribution of NH reported for 124 galactic ISGRI sources (excluding the 33 IGR sources which are in red.

<NH> ∼ 1.5⋅1022 at/cm2

σ ∼ 0.7

<NH> ∼ 6.9⋅1022 at/cm2

σ ∼ 0.6

Modulation

Numerical distribution of spin periods for 66 ISGRI sources, including 15 IGR sources in red.

Modulation

Numerical distribution of orbital periods for 75 ISGRI sources, including 9 IGR sources in red.

Modulation

The spin vs. orbital period diagram for 39 ISGRI sources. The IGR sources (6) are circled.

Thus far, most IGR sources in the Corbet diagram are in the region of purely wind-driven accretors.

Perspectives

Thanks to INTEGRAL, a coherent picture is emerging for the distribution of high-energy galactic sources. This will help us better understand the evolutionary scenarios of young and old stellar populations, heavily-absorbed sources, etc.

On average, galactic IGR sources are more heavily absorbed than the sources seen before INTEGRAL (instrumental selection effect). The most absorbed IGR sources are found towards the Norma Arm, which is the region with the highest formation rate of OB supergiant stars (Bronfman et al., 2000).

In general, ISGRI source populations follow the distributions that are expected from: the exposure time dedicated to each location of the sky.the evolution of each type of source.

Some IGR sources have yet to undergo follow-up observations in X-rays, so they lack refined positions for the identification of an optical/IR counterpart, a spectrum where we could access NH values, and timing analyses to search for modulations.

To partially address these unclassified sources, we proposed a Chandra observation campaign for 6 of them (AO8, PI: Bodaghee). When new IGR sources are discovered this year, we will trigger ToO observations for 4 of them with guaranteed RXTE time (PI: Rodriguez). We have also proposed Chandra ToO observations for 2 other new sources (AO8, PI: Paizis).

References

Bodaghee et al., 2006, in prep.

IGR J16318−4848: the galactic binary with the highest absorption known and INTEGRAL's first new source:“The properties of the absorbing and line-emitting material in IGR J16318−4848”Matt & Guainazzi, 2003, MNRAS, Vol. 341, p. 13 (arxiv.org/abs/astro-ph/0303626)

IGR J00291+5934: the fastest accretion-driven millisecond pulsar known:“Discovery of the accretion-powered millisecond X-ray pulsar IGR J00291+5934”Galloway et al., 2005, ApJ, Vol. 622, p. 45 (arxiv.org/abs/astro-ph/0501064)

IGR J16393−4643: a member of the growing class of heavily-absorbed supergiant X-ray pulsars:“IGR J16393−4643: a new heavily-obscured X-ray pulsar”Bodaghee et al., 2006, A&A, Vol. 447, p. 1027 (arxiv.org/abs/astro-ph/0510112)

INTEGRAL reference catalog:“High-energy sources before INTEGRAL. INTEGRAL reference catalog”Ebisawa et al., 2004, A&A, Vol. 411, p. 59 (arxiv.org/abs/astro-ph/0309101)

ISGRI survey catalogs:“The Second IBIS/ISGRI Soft Gamma-Ray Survey Catalog”Bird et al., 2006, ApJ, Vol. 636-2, p. 765“Global characteristics of the first IBIS/ISGRI catalogue sources: unveiling a murky episode of binary star evolution”Dean et al., 2005, A&A, Vol. 443, p. 4851 (arxiv.org/abs/astro-ph/0508291)

INTEGRAL HMXBs:“INTEGRAL insight into the inner parts of the Galaxy. High mass X-ray binaries”Lutovinov et al., 2005, A&A, Vol. 444, p. 821 (arxiv.org/abs/astro-ph/0411550)

INTEGRAL AGNs:“The First INTEGRAL AGN Catalog”Beckmann et al., 2006, ApJ, Vol. 638, p. 642 (arxiv.org/abs/astro-ph/0510530)

IGR sources:IGR Sources Page (J. Rodriguez: http://isdc.unige.ch/~rodrigue/html/igrsources.html).

RXTE XRBs:“The Milky Way in X-rays for an outside observer. Log(N)–Log(S) and luminosity function of X-ray binaries from RXTE/ASM data”Grimm et al., 2002, A&A, Vol. 391, p. 923 (arxiv.org/abs/astro-ph/0109239)