A SIMBOL-X View of Microquasars

Based on spectral simulations, I show how focusing of the X-ray radiations above 10 keV will open a new window for the study of microquasars. With simulations of soft and hard state spectra of Galactic sources, I discuss how SIMBOL-X can help to precisely measure the spin of black holes. Spectral study on short ~1 s time scales will also allow the accretion-ejection connections to be accessed, and the formation of jets possibly witnessed in X-rays. I then turn to external galaxies, and demonstrate that spectral studies of hard sources will be possible up to at least ~1 Mpc. For such sources, subtle spectral signatures (e.g. a reflection bump) will clearly be detected. I finally discuss the implications that these original results will bring on the physics of microquasars and black holes.Comment: 6 pages, 4 figures, invited talk submitted to the proceedings of "SIMBOL-X: the hard X-ray Universe in focus", conference, held May 14-16, 2007, Bologna (Italy

Calibrated Estimates of the Energy in Major Flares of GRS 1915+105

We analyze the energetics of the major radio flare of October 8 2005 in GRS 1915+105. The flare is of particular interest because it is one of the most luminous and energetic radio flares from a Galactic black hole that has ever been observed. The motivation is two-fold. One, to learn more about the energetics of this most extreme phenomenon and its relationship to the accretion state. The second is to verify if the calibrated estimates of the energy of major radio flares (based on the peak low frequency optically thin flux) derived from flares in the period 1996-2001 in Punsly & Rodriguez (2013), PR13 hereafter, can be used to estimate plasmoid energy beyond this time period. We find evidence that the calibrated curves are still accurate for this strong flare. Furthermore, the physically important findings of PR13 are supported by the inclusion of this flare: the flare energy is correlated with both the intrinsic bolometric X-ray luminosity, $L_{\mathrm{bol}}$, $\sim 1$ hour before ejection and $L_{\mathrm{bol}}$ averaged over the duration of the ejection of the plasmoid and $L_{\mathrm{bol}}$ is highly elevated relative to historic levels just before and during the ejection episode. A search of the data archives reveal that only the October 8 2005 flare and those in PR13 have adequate data sampling to allow estimates of both the energy of the flare and the X-ray luminosity before and during flare launch.Comment: To appear in MNRA

A connection between cellularization for groups and spaces via two-complexes

Let $M$ denote a two-dimensional Moore space (so $H_2(M; \Z) = 0$), with fundamental group $G$. The $M$-cellular spaces are those one can build from $M$ by using wedges, push-outs, and telescopes (and hence all pointed homotopy colimits). The question we address here is to characterize the class of $M$-cellular spaces by means of algebraic properties derived from the group $G$. We show that the cellular type of the fundamental group and homological information does not suffice, and one is forced to study a certain universal extension.Comment: 16 pages; some little corrections and improvements have been made. To appear in J. Pure and Applied Algebr

Ejection of the corona at State transitions: a common behaviour in microquasars?

The onset of most microquasar outbursts is characterized by a state transition between a Low/Hard State (LHS) and a High/Soft State (HSS). Besides drastic spectral and timing changes, this transition often shows a discrete ejection event detectable in the radio range. However, the exact nature of the ejected material and the mechanisms that give birth to these phenomena are yet to be unraveled. Recent simultaneous radio and X-ray observations on several sources point to a coronal nature of the ejected material. In the cases of GRS 1915+105, XTE J1550-564, and the 2002 outburst of GX 339-4, the flux of the Compton component decreases sharply just before an ejection is detected in the radio range. Finally, in the case of H1743-322, drastic physical changes occurred in the corona just before the state transition, compatible with the disappearance of part of this medium. Thus, the behaviour of at least 4 microquasars points in the direction of an ejection of the corona at the state transition, feature that is yet to be confirmed (or infirmed) in the case of other available sources.Comment: 4 pages, 2 figures, Proceedings of the 2nd International Simbol-X symposium held in Paris, 2-5 December 200

A Temporal Analysis Indicates a Mildly Relativistic Compact Jet in GRS~1915+105

Most of our knowledge of the radio morphology and kinematics of X-ray binary partially synchrotron self-absorbed compact jets (hereafter compact jets) is based on the observations of GRS~1915+105 which has the most prominent compact jet. Yet, the compact jet bulk velocity, $v$, is poorly constrained in the literature, $0.07 < v/c < 0.98$. In spite of this uncertainty, compact jets are often unified with relativistic jets in active galactic nuclei. We have estimated $v$ as part of a temporal analysis of GRS~1915+105 jets in "high plateau states" (HPS). We define the HPS as a state showing a hard X-ray spectrum and low level of long-term ($>10$s) X-ray activity associated with 15 GHz flux density $>70$ mJy for $>7$ consecutive days. The radio emission is associated with compact jet emission. Two HPS were monitored at 15 GHz during their termination with e-folding times of 3.8 hrs and 8.6 hrs. We combine this time scale with the scale of spatial variation of the linear source of a VLBA image preceding the fade of one of these HPS in order to estimate the jet speed. Our assumption that the reduction in radio emissivity propagates as an approximate discontinuity down the HPS jet (leaving a weak jet in its wake) indicates $0.17 <v/c< 0.43$. This agrees closely with the only other existing $v$ estimates that are derived directly from radio images, jet asymmetry produced by Doppler enhancement.Comment: To appear in Ap

Plus-construction for algebras over an operad, cyclic and Hochschild homologies up to homotopy

In this paper we apply homotopical localization to the framework of differential graded algebras over an operad. We get plus construction by performing nullification with respect to an universal acyclic algebra. This plus construction for Lie and Leibniz algebras up to homotopy yields two new homology theories for associative algebras. They are closely related to cyclic and Hochschild homologies. We also compute their first homology groups

Revealing the nature of high-mass X-ray binaries through multi-wavelength and statistical analyses

We summarize the results of our long-running campaign to help understand the nature of high-mass X-ray binaries (HMXBs), emphasizing recent Suzaku observations of IGR J16207-5129 and IGR J17391-3021. Thanks to the expanding ranks of HMXBs in our Galaxy, we are able to perform more reliable statistical analyses on the three currently-known sub-classes of HMXB: those with supergiant companions (SGXBs); those with Be companions (BEXBs); and the enigmatic Supergiant Fast X-ray Transients (SFXTs). We discuss new diagnostic tools, akin to the "Corbet diagram," in which HMXBs tend to segregate based on their dominant accretion mechanism. We show how SFXTs span across the divided populations of BEXBs and SGXBs, bolstering the intriguing possibility that some SFXTs represent an evolutionary link. The use of HMXBs as tracers of recent massive star formation is revisited as we present the first ever spatial correlation function for HMXBs and OB star-forming complexes. Our results indicate that at distances less than a few kpc from a given HMXB, it is more likely to have neighbors that are known massive-star forming regions as opposed to objects drawn from random distributions. The characteristic scale of the correlation function holds valuable clues to HMXB evolutionary timescales.Comment: 6 pages, 5 figures, to appear in proceedings of the 4th International MAXI Workshop in Tokyo, "The First Year of MAXI: Monitoring Variable X-ray Sources

Finite simple groups and localization

The purpose of this paper is to explore the concept of localization, which comes from homotopy theory, in the context of finite simple groups. We give an easy criterion for a finite simple group to be a localization of some simple subgroup and we apply it in various cases. Iterating this process allows us to connect many simple groups by a sequence of localizations. We prove that all sporadic simple groups (except possibly the Monster) and several groups of Lie type are connected to alternating groups. The question remains open whether or not there are several connected components within the family of finite simple groups.Comment: 17 pages. See also http://magma.unil.ch/jscherer/ The two last sections (especially that about preservation of simplicity by localizations) have been removed and will be the subject of a separate paper. Some proofs have been rewritten in a clearer styl

Is the ejection of the corona a general phenomenon in microquasars?

We study the evolution of some microquasars during their outbursts as observed with the X-ray telescopes RXTE and INTEGRAL. We focus on the interplay between the accretion disc, and the medium responsible for the production of the hard X-rays (the so-called corona). By comparing the behaviour of two sources (XTE J1550-564 and GRS 1915+105) at X-ray energies and radio wavelengths, we propose a scenario in which the discrete ejections are triggered in coincidence with soft X-ray peaks during the outburst. We also suggest, in those two sources, that the ejected material is the corona that is seen to disappear in coincidence with the X-ray maxima. We then turn to two other sources, XTE J1748-248, and XTE J1859+226, and study whether the same conclusions can be drawn from the existing multi-wave length (radio+X-ray) data.Comment: 10 pages, 7 figures, Proceedings of the 7th INTEGRAL workshop held in Copenhagen 8-11 September 200

Chandra observations of five INTEGRAL sources: new X-ray positions for IGR J16393-4643 and IGR J17091-3624

The Chandra High Resolution Camera observed the fields of five hard X-ray sources in order to help us obtain X-ray coordinates with sub-arcsecond precision. These observations provide the most accurate X-ray positions known for IGR J16393-4643 and for IGR J17091-3624. The obscured X-ray pulsar IGR J16393-4643 lies at R.A. (J2000) = 16:39:05.47, and Dec. = -46:42:13.0 (error radius of 0.6" at 90% confidence). This position is incompatible with the previously-proposed counterpart 2MASS J16390535-4642137, and it points instead to a new counterpart candidate that is possibly blended with the 2MASS star. The black hole candidate IGR J17091-3624 was observed during its 2011 outburst providing coordinates of R.A. = 17:09:07.59, and Dec. = -36:24:25.4. This position is compatible with those of the proposed optical/IR and radio counterparts, solidifying the source's status as a microquasar. Three targets, IGR J14043-6148, IGR J16358-4726, and IGR J17597-2201, were not detected. We obtained 3{\sigma} upper limits of, respectively, 1.7, 1.8, and 1.5 \times 10^-12 erg cm^-2 s^-1 on their 2-10 keV fluxes.Comment: 10 pages, 3 figures, accepted for publication in Ap