Related papers: Transient jets in V617 Sagittarii
A few Galactic objects are known to be variable sources of photons with energies above 100 GeV. These systems are mostly binaries, where variability can often be connected to the orbital period. Particle acceleration and gamma-ray…
We combine infrared spectra in the I, J, H and K bands together with JHK photometry to characterize the spectral type, luminosity class and distance to the infrared counterparts to five INTEGRAL sources. For SAX J18186-1703 and IGR…
Supergiant Fast X-ray Transients (SFXTs) represent the most extreme case of X-ray variability in High Mass X-ray Binaries hosting blue supergiant companions. Mainly discovered thanks to the INTEGRAL monitoring of the Galactic plane, these…
Inverse Compton Scattering (ICS) by a relativistic electron beam jet at GeV energies (emitted by a compact object as a NS, BH,...), a NSJ, onto thermal BBR photons (from a nearby stellar companion) may originate a collinear gamma jet (GJ).…
V4641 Sagittarii (V4641 Sgr) is a unique Galactic microquasar system featuring a stellar-mass black hole accreting matter from a massive companion. One of its intriguing features is the presence of relativistic radio jets almost…
A fraction of high-mass X-ray binaries are supergiant fast X-ray transients. These systems have on average low X-ray luminosities, but display short flares during which their X-ray luminosity rises by a few orders of magnitude. The leading…
The X-ray spectrum of the Galactic X-ray binary V4641 Sgr in outburst has been found to exhibit a remarkably broad emission feature above 4 keV, with inferred equivalent widths up to 2 keV. Such a feature was first detected during the X-ray…
Supergiant fast X-ray transients (SFXTs) are high mass X-ray binaries (HMXBs) hosting a neutron star and an OB supergiant companion. We examine the available Swift data, as well as other new or archival/serendipitous data, on three sources:…
Microquasars are potential $\gamma$-ray emitters. Indications of transient episodes of $\gamma$-ray emission were recently reported in at least two systems: Cyg X-1 and Cyg X-3. The identification of additional $\gamma$-ray-emitting…
Close Binary Supersoft X-ray Sources (CBSS) are considered strong candidates to SN Ia progenitors, but very few CBSS are known in our Galaxy. The galactic counterparts of the CBSS may be the V Sge stars, not detected in X-rays due to the…
We report here on the most recent results obtained on a new class of High Mass X-ray Binaries, the Supergiant Fast X-ray Transients. Since October 2007, we have been performing a monitoring campaign with Swift of four SFXTs (IGRJ17544-2916,…
Supergiant Fast X-ray Transients (SFXTs) are one of the most intriguing (and unexpected) results of the INTEGRAL mission. They are a new class of High Mass X-ray Binaries involving about 20 sources to date, with 8 firmly identified SFXTs…
The aim of this PhD Thesis is to characterize a representative sample of Supergiant X-ray Binaries (SGXBs) formed by 4 sources: XTE J1855-026, a classical SGXB with long-term stable X-ray flux; AX J1841.0-0535 and AX J1845.0-0433, two…
Very faint X-ray transients (VFXTs) are X-ray transients with peak X-ray luminosities ($L_X$) of $L_X\lesssim10^{36}$ erg/s, which are not well-understood. We carried out a survey of 16 square degrees of the Galactic Bulge with the Swift…
We analyze the two unclassified newly outbursting X-ray binary transients in the galactic center, Swift J174540.7-290015 and Swift J174540.2-290037, in an attempt to identify the nature of these sources. We engage in a thorough spectral…
The prototype of the Beta Cep class of pulsating stars, Beta Cep, rotates relatively slowly, and yet displays episodic Halpha emission. Such behaviour is typical of a classical Be star. For some time this posed a contradiction to our…
Non-thermal variable emission from radio to very-high energy gamma rays (VHE; >100 GeV) are the prime characteristics of gamma-ray binaries. The underlying physical processes leading to the observed VHE emission are not well understood, as…
We report observations which confirm the identity of the optical/IR counterpart to the Rossi X-ray Timing Explorer transient source XTE J0111.2-7317. The counterpart is suggested to be a B0-B2 star (luminosity class III--V) showing an IR…
INTEGRAL monitoring of the Galactic Plane in the last 5 years revealed a new subclass of High Mass X-ray Binaries (HMXBs), the Supergiant Fast X-ray Transients (SFXTs). They display flares lasting from minutes to hours, with peak luminosity…
In the last 15 years, 6 dedicated observation programs were carried out to monitor ~20 deg around the galactic center for transient activity above a few keV. Transient activity from low-mass X-ray binaries shows a strong preference for this…