Microquasars as sources of positron annihilation radiation

Guessoum, Nidhal; Jean, P.; Prantzos, Nikos

doi:10.1051/0004-6361:20065240

Cited by 50 publications

(80 citation statements)

References 65 publications

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“…The only exception is 4U 0614+091, for which we obtain a higher flux limit (8.7 × 10 −4 ph cm −2 s −1 ), because it is located in a sky region with a lower exposure. Among X-ray binaries (XRBs), microquasars (MQs) are promising galactic positron emitters (see Guessoum et al 2006). We therefore report the 511 keV upper limits for the X-ray Binaries classified as microquasars and detected by IBIS above 20 keV (Table 4).…”

Section: Kev Flux Upper Limit For Compact Sourcesmentioning

confidence: 99%

Searching for the 511 keV annihilation line from galactic compact objects with the IBIS gamma ray telescope

Cesare¹

2011

A&A

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Context. The first detection of a gamma ray line with an energy of about 500 keV from the center of our Galaxy dates back to the early seventies. Thanks to the astrophysical application of high spectral resolution detectors, it was soon clear that this radiation was due to the 511 keV photons generated by electron-positron annihilation. Even though the physical process are known, the astrophysical origin of this radiation is still a mystery. Aims. The spectrometer SPI aboard the INTEGRAL gamma-ray satellite has been used to produce the first all-sky map in light of the 511 keV annihilation, but no direct evidence of any 511 keV galactic compact objects has been found. Owing to its moderate angular resolution, these SPI data are still compatible with a distribution of point sources clustered in the bulge of our Galaxy. Thanks to the fine angular resolution and the large field of view, the IBIS imager on the INTEGRAL satellite gives us the unique opportunity to search for a possible 511 keV line from point sources associated to known objects, such as X-ray binaries, or supernovae, or even new ones. Methods. We present the first deep IBIS 511 keV all-sky map, obtained by applying standard analysis to about 5 years of data. Possible 511 keV signals are also searched over hour-day-month timescales. The IBIS sensitivity at 511 keV depends on the detector quantum efficiency at this energy and on the background. Both these quantities were estimated in this work. Results. We find no evidence of Galactic 511 keV point sources. With an exposure of 10 Ms, in the center of the Galaxy, we estimate a 1.6 × 10 −4 ph cm −2 s −1 flux 2 sigma upper limit. A similar limit is given in a wide area in the Galactic center region with similar exposures. The IBIS 511 keV flux upper limits for microquasars and supernova remnants detected in the hard X domain (E > 20 keV) are also reported. Conclusions. Our results are consistent with a diffuse e + e − annihilation scenario. If positrons are generated in compact objects, we expect that a significant fraction of them propagate in the interstellar medium before they are annihilated away from their birth places.

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Section: Kev Flux Upper Limit For Compact Sourcesmentioning

confidence: 99%

Searching for the 511 keV annihilation line from galactic compact objects with the IBIS gamma ray telescope

Cesare¹

2011

A&A

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“…cosmic rays). Only two astrophysical candidates remain as potentially important contributors: LMXRBs (Prantzos 2004a) or the microquasar variant of that class of sources (Guessoum et al 2006) and the supermassive black hole at the Galactic center (e.g. Cheng et al 2006, Totani 2006, Chernysov et al 2009 and references therein).…”

Section: Pos(integral 2010)018mentioning

confidence: 99%

“…That detection, the first ever of a cosmic radioactivity in γ-rays, showed that nucleosynthesis is still active in the Milky Way; however, the implied large amount of galactic 26 Al (∼2 M per Myr, assuming steady state) was difficult to accomodate in conventional models of galactic chemical evolution if SN were the main 26 Al source (Clayton 1984), since 27 Al would be overproduced in that case; however, if the "closed box model" assumption is dropped and infall is assumed in the chemical evolution model, that difficulty is removed, as subsequently shown by Clayton and Leising (1987).…”

Section: Historical Backgroundmentioning

confidence: 99%

Nucleosynthesis and gamma-ray lines

Prantzos¹

2011

Proceedings of 8th INTEGRAL Workshop “The Restless Gamma-Ray Universe” — PoS(INTEGRAL 2010)

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Astrophysical gamma-ray spectroscopy is an invaluable tool for studying nuclear astrophysics, supernova structure, recent star formation in the Milky Way and mixing of nucleosynthesis products in the interstellar medium. After a short, historical, introduction to the field, I present a brief review of the most important current issues. Emphasis is given to radioactivities produced by massive stars and associated supernova explosions, and in particular, those related to observations carried out by INTEGRAL: short-lived 44 Ti from CasA and long-lived 26 Al and 60 Fe from massive stars. The observed 511 keV emission from positron annihilation in the Galaxy and the role of stellar radioactivity and other potential positron sources are also discussed. Universe-Integral2010, September 27-30, 2010 Dublin Ireland * Speaker. 8th INTEGRAL Workshop The Restless Gamma-rayc Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.http://pos.sissa.it/ PoS(INTEGRAL 2010)018Nucleosynthesis and gamma-ray lines Nikos Prantzos Historical backgroundGamma-ray line astronomy with cosmic radioactivities was essentially founded with the landmark paper of Clayton, Colgate and Fishman (1969). That work clarified the implications of the production of 56 Ni (a doubly magic, and yet unstable nucleus) during explosive Si-burning in supernovae (SN). In particular, it opened exciting perspectives for γ-ray line astronomy, by suggesting that any supernova within the local group of galaxies woud be detectable in the characteristic γ-ray lines resulting from the radioactive decay of 56 Ni (lifetime τ Ni−56 =8.8 d) and its daughter nucleus 56 Co (τ Co−56 =0.31 y).In the 70's D. Clayton identified most of the radionuclides of astrophysical interest (i.e. giving a detectable γ-ray line signal); for that purpose, he evaluated their average SN yields by assuming that the corresponding daughter stable nuclei are produced in their solar system abundances 1 . Amazingly enough (or naturally enough, depending on one's point of view) his predictions of average SN radionuclide yields ( Table 2 in Clayton 1982) are in excellent agreement with modern yield calculations, based on full stellar models and detailed nuclear physics (see Fig. 1 in Prantzos 2004a). Only the importance of 26 Al (τ Al−26 =1.04 10 6 y) escaped Clayton's (1982) attention, perhaps because its daughter nucleus 26 Mg is mostly produced in its stable form, making the evaluation of the parent's yield quite uncertain. That uncertainty did not prevent Arnett (1977) and Ramaty and Lingenfelter (1977) from arguing that, even if only 10 −3 of solar 26 Mg is produced as 26 Al, the resulting Galactic flux from tens of thousands of supernovae (during the ∼1 Myr lifetime of 26 Al) would be of the order of 10 −4 cm −2 s −1 .In the case of 26 Al nature appeared quite generous, providing a γ-ray flux even larger than the optimistic estimates of Ramaty and Lingenfelter (1977): the HEAO-3 satellite detected the corresponding 1.8 MeV line from th...

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“…A new significant source of positrons seems quite unlikely since various recent reviews (e.g., Dermer & Murphy 2001;Knödlseder et al 2005;Guessoum, Jean, & Prantzos 2006) of the po-tential Galactic positron sources all conclude that supernovae are still the most plausible source, and that other suggested sources, including cosmic-ray interactions, novae, and various exotic processes, all appear to yield much weaker fluxes or are highly uncertain.…”

Section: New Source Of Positrons? -No!mentioning

confidence: 99%

Positron Propogation and the INTEGRAL/SPI 511 keV Bulge/Disk Ratio

Rothschild¹

2009

Proceedings of 7th INTEGRAL Workshop — PoS(Integral08)

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The Galactic bulge/disk ratio of 511 keV positron annihilation radiation measured by INTE-GRAL/SPI and the bulge/disk ratio of Galactic supernovae differ significantly. We show, however, that this difference can be understood in the context of a Galactic supernova origin of positrons from decay of nucleosynthetic 56 Ni, 44 Ti, and 26 Al, if the detailed propagation of these MeV positrons in the various phases of the interstellar medium is also taken into consideration. These relativistic positrons must first slow down to energies <10 eV before they can annihilate, and therefore can travel significant distances before annihilating. We show that about 72% of the positrons resulting from supernovae nucleosynthesis are born in the hot (10 6 K) tenuous phase of the interstellar medium, because of its large filling factor. However, they do not annihilate there because they stream out of this medium and either escape into the overlying halo, or slow down and annihilate in the much denser, warm (10 4 K) ionized and neutral phases -predominately the outer envelopes of molecular clouds. This propagation explains the observed shape of the 511 keV positron annihilation line and the ratio of the line to positronium continuum fluxes. Such propagation also explains the observed bulge/disk ratio of the annihilation radiation, since more than half of the positrons born in the disk escape into the bulge and halo. Further, we predict that the bulk of the broad (5.4 keV) component of the 511 keV line emission comes from the 0.5-1.5 kpc region of the bulge, while much of the narrow (1.3 keV) component of the line emission originates in the central 0.5 kpc. Note: Although a larger paper, on which this is based, has been revised and updated for the Astrophysical Journal, using more recent INTEGRAL measurements, this paper gives only what was presented at the meeting, and the conclusions are still the same.

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Microquasars as sources of positron annihilation radiation

Cited by 50 publications

References 65 publications

Searching for the 511 keV annihilation line from galactic compact objects with the IBIS gamma ray telescope

Searching for the 511 keV annihilation line from galactic compact objects with the IBIS gamma ray telescope

Nucleosynthesis and gamma-ray lines

Positron Propogation and the INTEGRAL/SPI 511 keV Bulge/Disk Ratio

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