arXiv subjects

R. Terrier

Publications and source records attributed to R. Terrier.

At least 55 records · Page 3Linked to original sources

arXiv2011

Discovery of an Energetic 38.5 ms Pulsar Powering the Gamma-ray Source IGR J18490-0000/HESS J1849-000

We report the discovery of a 38.5 ms X-ray pulsar in observations of the soft gamma-ray source IGR J18490-0000 with the Rossi X-ray Timing Explorer (RXTE). PSR J1849-0001 is spinning down rapidly with period derivative 1.42E-14 s/s, yielding a spin-down luminosity 9.8E36 erg/s, characteristic age 42.9 kyr, and surface dipole magnetic field strength 7.5E11 G. Within the INTEGRAL/IBIS error circle lies a point-like XMM-Newton and Chandra X-ray source that shows evidence of faint extended emission consistent with a pulsar wind nebula (PWN). The XMM-Newton spectrum of the point source is well fitted by an absorbed power-law model with photon index Gamma(PSR) = 1.1 +/- 0.2, N_H = (4.3+/-0.6)E22 cm^-2, and F(PSR;2-10keV) = (3.8+/-0.3)E-12 erg/s/cm^2, while the spectral parameters of the extended emission are Gamma(PWN) = 2.1 and F(PWN;2-10 keV) = 9E-13 erg/s/cm^2. IGR J18490-0000 is also coincident with the compact TeV source HESS J1849-000. For an assumed distance of 7 kpc in the Scutum arm tangent region, the 0.35-10 TeV luminosity of HESS J1849-000 is 0.13% of the pulsar's spin down energy, while the ratio F(0.35-10 TeV)/F(PWN; 2-10 keV) of approx. 2. These properties are consistent with leptonic models of TeV emission from PWNe, with PSR J1849-0001 in a stage of transition from a synchrotron X-ray source to an inverse Compton gamma-ray source.

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arXiv2010

Fading hard X-ray emission from the Galactic Centre molecular cloud Sgr B2

The centre of our Galaxy harbours a 4 million solar mass black hole that is unusually quiet: its present X-ray luminosity is more than 10 orders of magnitude less than its Eddington luminosity. The observation of iron fluorescence and hard X-ray emission from some of the massive molecular clouds surrounding the Galactic Centre has been interpreted as an echo of a past flare. Alternatively, low-energy cosmic rays propagating inside the clouds might account for the observed emission, through inverse bremsstrahlung of low energy ions or bremsstrahlung emission of low energy electrons. Here we report the observation of a clear decay of the hard X-ray emission from the molecular cloud Sgr B2 during the past 7 years thanks to more than 20 Ms of INTEGRAL exposure. The measured decay time is compatible with the light crossing time of the molecular cloud core . Such a short timescale rules out inverse bremsstrahlung by cosmic-ray ions as the origin of the X ray emission. We also obtained 2-100 keV broadband X-ray spectra by combining INTEGRAL and XMM-Newton data and compared them with detailed models of X-ray emission due to irradiation of molecular gas by (i) low-energy cosmic-ray electrons and (ii) hard X-rays. Both models can reproduce the data equally well, but the time variability constraints and the huge cosmic ray electron luminosity required to explain the observed hard X-ray emission strongly favor the scenario in which the diffuse emission of Sgr B2 is scattered and reprocessed radiation emitted in the past by Sgr A*. Using recent parallax measurements that place Sgr B2 in front of Sgr A*, we find that the period of intense activity of Sgr A* ended between 75 and 155 years ago.

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arXiv2010

Discovery of a highly energetic pulsar associated with IGR J14003-6326 in a young uncataloged Galactic supernova remnant G310.6-1.6

We report the discovery of 31.18 ms pulsations from the INTEGRAL source IGR J14003-6326 using the Rossi X-ray Timing Explorer (RXTE). This pulsar is most likely associated with the bright Chandra X-ray point source lying at the center of G310.6-1.6, a previously unrecognised Galactic composite supernova remnant with a bright central non-thermal radio and X-ray nebula, taken to be the pulsar wind nebula (PWN). PSR J1400-6325 is amongst the most energetic rotation-powered pulsars in the Galaxy, with a spin-down luminosity of Edot = 5.1E+37 erg.s-1. In the rotating dipole model, the surface dipole magnetic field strength is B_s = 1.1E+12 G and the characteristic age tau_c = P/2Pdot = 12.7 kyr. The high spin-down power is consistent with the hard spectral indices of the pulsar and the nebula of 1.22 +/- 0.15 and 1.83 +/- 0.08, respectively, and a 2-10 keV flux ratio F_PWN/F_PSR ~ 8. Follow-up Parkes observations resulted in the detection of radio emission at 10 and 20 cm from PSR J1400-6325 at a dispersion measure of ~ 560 cm-3 pc, which implies a relatively large distance of 10 +/- 3 kpc. However, the resulting location off the Galactic Plane of ~ 280 pc would be much larger than the typical thickness of the molecular disk, and we argue that G310.6-1.6 lies at a distance of ~ 7 kpc. There is no gamma-ray counterpart to the nebula or pulsar in the Fermi data published so far. A multi-wavelength study of this new composite supernova remnant, from radio to very-high energy gamma-rays, suggests a young (< 1000 yr) system, formed by a sub-energetic (~ 1E+50 ergs), low ejecta mass (M_ej ~ 3 Msun) SN explosion that occurred in a low-density environment (n_0 ~ 0.01 cm-3).

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arXiv2009

The 4th IBIS/ISGRI soft gamma-ray survey catalog

In this paper we report on the fourth soft gamma-ray source catalog obtained with the IBIS gamma-ray imager on board the INTEGRAL satellite. The scientific dataset is based on more than 70Ms of high quality observations performed during the first five and a half years of Core Program and public observations. Compared to previous IBIS surveys, this catalog includes a substantially increased coverage of extragalactic fields, and comprises more than 700 high-energy sources detected in the energy range 17--100 keV, including both transients and faint persistent objects which can only be revealed with longer exposure times. A comparison is provided with the latest Swift/BAT survey results.

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arXiv2009

Soft gamma-ray constraints on a bright flare from the Galactic Center supermassive black hole

Sagittarius A* (Sgr A*) is the supermassive black hole residing at the center of the Milky Way. It has been the main target of an extensive multiwavelength campaign we carried out in April 2007. Herein, we report the detection of a bright flare from the vicinity of the horizon, observed simultaneously in X-rays (XMM/EPIC) and near infrared (VLT/NACO) on April 4th for 1-2 h. For the first time, such an event also benefitted from a soft gamma-rays (INTEGRAL/ISGRI) and mid infrared (VLT/VISIR) coverage, which enabled us to derive upper limits at both ends of the flare spectral energy distribution (SED). We discuss the physical implications of the contemporaneous light curves as well as the SED, in terms of synchrotron, synchrotron self-Compton and external Compton emission processes.

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arXiv2009

Detection of very-high-energy gamma-ray emission from the vicinity of PSR B1706-44 with H.E.S.S

The energetic pulsar PSR B1706-44 and the adjacent supernova remnant (SNR) candidate G 343.1-2.3 were observed by H.E.S.S. during a dedicated observational campaign in 2007. A new source of very-high-energy (VHE; E > 100 GeV) gamma-ray emission, HESS J1708-443, was discovered with its centroid at RA(J2000) = 17h08m10s and Dec(J2000) = -44d21', with a statistical error of 3 arcmin on each axis. The VHE gamma-ray source is significantly more extended than the H.E.S.S. point-spread function, with an intrinsic Gaussian width of 0.29 +/- 0.04 deg. Its energy spectrum can be described by a power law with a photon index Gamma = 2.0 +/- 0.1 (stat) +/- 0.2 (sys). The integral flux measured between 1-10 TeV is ~17% of the Crab Nebula flux in the same energy range. The possible associations with PSR B1706-44 and SNR G343.1-2.3 are discussed.

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arXiv2009

Bursting behavior of the Galactic Center faint X-ray transient GRS 1741.9-2853

The neutron star low-mass X-ray binary GRS 1741.9-2853 is a known type-I burster of the Galactic Center. It is transient, faint, and located in a very crowded region, only 10 arcmin from the supermassive black hole Sgr A*. Therefore, its bursting behavior has been poorly studied so far. In particular, its persistent emission has rarely been detected between consecutive bursts, due to lack of sensitivity or confusion. This is what made GRS 1741.9-2853 one of the nine "burst-only sources" identified by BeppoSAX a few years ago. The physical properties of GRS 1741.9-2853 bursts are yet of great interest since we know very little about the nuclear regimes at stake in low accretion rate bursters. We examine here for the first time several bursts in relation with the persistent emission of the source, using INTEGRAL, XMM-Newton, and Swift observations. We investigate the source flux variability and bursting behavior during its 2005 and 2007 long outbursts. The persistent luminosity of GRS 1741.9-2853 varied between ~1.7 and 10.5 10^36 erg s^-1, i.e. 0.9-5.3% of the Eddington luminosity. The shape of the spectrum as described by an absorbed power-law remained with a photon index Gamma ~ 2 and a column density $N_{\rm H} ~ 12 10^22 cm^-2 throughout the outbursts. We discovered 11 type-I bursts with INTEGRAL, and inspected 4 additional bursts: 2 recorded by XMM-Newton and 2 by Swift. From the brigthest burst, we derive an upper limit on the source distance of ~7 kpc. The observed bursts characteristics and source accretion rate suggest pure helium explosions igniting at column depths y_{ign} ~ 0.8-4.8 10^8 g cm^-1, for typical energy releases of ~1.2-7.4 10^39 erg.

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arXiv2008

The Full Spectrum Galactic Terrarium: MHz to TeV Observations of Various Critters

Multi-wavelength studies at radio, infrared, optical, X-ray, and TeV wavelengths have discovered probable counterparts to many Galactic sources of GeV emission detected by EGRET. These include pulsar wind nebulae, high mass X-ray binaries, and mixed morphology supernova remnants. Here we provide an overview of the observational properties of Galactic sources which emit across 19 orders of magnitude in energy. We also present new observations of several sources.

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arXiv2008

INTEGRAL SPI All-Sky View in Soft Gamma Rays: Study of Point Source and Galactic Diffuse Emissions

We have processed the data accumulated with INTEGRAL SPI during 4 years (~ 51 Ms) to study the Galactic ``diffuse'' emission morphology in the 20 keV to 8 MeV energy range. To achieve this objective, we have derived simultaneously an all-sky census of emitting sources and images of the Galactic Ridge (GR) emission. In the central radian, the resolved point source emission amounts to 88%, 91% and 68% of the total emission in the 25-50, 50-100 and 100-300 keV domains respectively. We have compared the GR emission spatial distribution to those obtained from CO and NIR maps, and quantified our results through latitude and longitude profiles. Below 50 keV, the SPI data are better traced by the latter, supporting a stellar origin for this emission. Furthermore, we found that the GR emission spectrum follows a power law with a photon index ~ 1.55 above 50 keV while an additional component is required below this energy. This component shows a cutoff around 30 keV, reinforcing a stellar origin, as proposed by Krivonos et al. (2007). The annihilation diffuse emission component is extracted simultaneously, leading to the determination of the related parameters (positronium flux and fraction). A specific discussion is devoted to the annihilation line distribution since a significant emission is detected over a region as large as ~80 degrees by ~10 degrees potentially associated with the disk or halo surrounding the central regions of our Galaxy.

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arXiv2007

New Companions for the lonely Crab? VHE emission from young pulsar wind nebulae revealed by H.E.S.S

The deeper and more extended survey of the central parts of the Galactic Plane by H.E.S.S. during 2005-2007 has revealed a number of new point-like, as well as, extended sources. Two point-like sources can be associated to two remarkable objects around "Crab-like" young and energetic pulsars in our Galaxy: G21.5-0.9 and Kes 75. The characteristics of each of the sources are presented and possible interpretations are briefly discussed.

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arXiv2007

44Ti nucleosynthesis gamma-ray lines with SIMBOL-X

In this contribution we discuss the 44Ti nucleosynthesis gamma-ray lines and their visibility with SIMBOL-X from simulations based on its expected sensitivity and spectro-imaging capabilities. The 44Ti radioactive nucleus can provide invaluable information on the details of supernova explosions. Its lifetime of about 85 yrs makes it the best indicator of the youth of these stellar explosions through its three gamma-ray lines at 67.9, 78.4 keV and 1.157 MeV. We focus on the youngest Galactic supernova remnants, namely: Cassiopeia A, for which the location and Doppler-velocity estimates of the 44Ti-emitting regions in the remnant would offer for the first time a unique view of nucleosynthesis processes which occurred in the innermost layers of the supernova; SN 1987A, in the Large Magellanic Cloud, whose progenitor is known, and for which the expected measurement of these lines would greatly constrain the stellar evolution models; Tycho and Kepler SNRs for which 44Ti lines have never been detected so far. The issue of the "young, missing and hidden" supernova remnants in the Galaxy will also be addressed using SIMBOL-X observations at the position of the 44Ti excesses that wide-field instruments like those onboard INTEGRAL and SWIFT/BAT should be able to reveal.

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arXiv2007

The 3rd IBIS/ISGRI soft gamma-ray survey catalog

In this paper we report on the third soft gamma-ray source catalog obtained with the IBIS/ISGRI gamma-ray imager on board the INTEGRAL satellite. The scientific dataset is based on more than 40 Ms of high quality observations performed during the first three and a half years of Core Program and public IBIS/ISGRI observations. Compared to previous IBIS/ISGRI surveys, this catalog includes a substantially increased coverage of extragalactic fields, and comprises more than 400 high-energy sources detected in the energy range 17-100 keV, including both transients and faint persistent objects which can only be revealed with longer exposure times.

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arXiv2006

XMM-Newton observations of HESS J1813-178 reveal a composite Supernova remnant

We present X-ray and 12CO(J=1-0) observations of the very-high-energy (VHE) gamma-ray source HESS J1813-178 with the aim of understanding the origin of the gamma-ray emission. Using this dataset we are able to undertake spectral and morphological studies of the X-ray emission from this object with greater precision than previous studies. NANTEN 12CO(J=1-0) data are used to search for correlations of the gamma-ray emission with molecular clouds which could act as target material for gamma-ray production in a hadronic scenario. The NANTEN 12CO(J=1-0) observations show a giant molecular cloud of mass 2.5 10^5 M$_{\sun}$ at a distance of 4 kpc in the vicinity of HESS J1813-178. Even though there is no direct positional coincidence, this giant cloud might have influenced the evolution of the gamma-ray source and its surroundings. The X-ray data show a highly absorbed non-thermal X-ray emitting object coincident with the previously known ASCA source AX J1813-178 showing a compact core and an extended tail towards the north-east, located in the centre of the radio shell-type Supernova remnant (SNR) G12.82-0.2. This central object shows morphological and spectral resemblance to a Pulsar Wind Nebula (PWN) and we therefore consider that the object is very likely to be a composite SNR. We discuss the scenario in which the gamma-rays originate in the shell of the SNR and the one in which they originate in the central object. We demonstrate, that in order to connect the core X-ray emission to the VHE gamma-ray emission electrons have to be accelerated to energies of at least 1 PeV.

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arXiv2006

On the nature of the hard X-ray source IGR J2018+4043

We found a very likely counterpart to the recently discovered hard X-ray source IGR J2018+4043 in the multi-wavelength observations of the source field. The source, originally discovered in the 20-40 keV band, is now confidently detected also in the 40-80 keV band, with a flux of (1.4 +/- 0.4) x 10(-11) erg cm(-2) s(-1). A 5 ks Swift observation of the IGR J2018+4043 field revealed a hard point-like source with the observed 0.5-10 keV flux of 3.4(+0.7)(-0.8) x 10(-12) erg cm(-2) s(-1) (90% confidence level) at alpha = 20h18m38.55s, delta = +40d41m00.4s (with a 4.2" uncertainty). The combined Swift-INTEGRAL spectrum can be described by an absorbed power-law model with photon index gamma = 1.3 +/- 0.2 and N_H = 6.1(+3.2)(-2.2) x 10(22) cm(-2). In archival optical and infrared data we found a slightly extended and highly absorbed object at the Swift source position. There is also an extended VLA 1.4 GHz source peaked at a beam-width distance from the optical and X-ray positions. The observed morphology and multiwavelength spectra of IGR J2018+4043 are consistent with those expected for an obscured accreting object, i.e. an AGN or a Galactic X-ray binary. The identification suggests possible connection of IGR J2018+4043 to the bright gamma-ray source GEV J2020+4023 (3EG J2020+4017) detected by COS B and CGRO EGRET in the gamma-Cygni SNR field.

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arXiv2006

The signature of 44Ti in Cassiopeia A revealed by IBIS/ISGRI on INTEGRAL

We report the detection of both the 67.9 and 78.4 keV 44Sc gamma-ray lines in Cassiopeia A with the INTEGRAL IBIS/ISGRI instrument. Besides the robustness provided by spectro-imaging observations, the main improvements compared to previous measurements are a clear separation of the two 44Sc lines together with an improved significance of the detection of the hard X-ray continuum up to 100 keV. These allow us to refine the determination of the 44Ti yield and to constrain the nature of the nonthermal continuum emission. By combining COMPTEL, BeppoSAX/PDS and ISGRI measurements, we find a line flux of (2.5 +/- 0.3)*10(-5) cm(-2) s(-1) leading to a synthesized 44Ti mass of 1.6 (+0.6-0.3)*10(-4) solar mass. This high value suggests that Cas A is peculiar in comparison to other young supernova remnants, from which so far no line emission from 44Ti decay has been unambiguously detected.

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arXiv2006

Multi-resolution analysis of the H.E.S.S. Galactic Survey Sources and Search for Counterparts in CO and HI data

From May to July 2004, the central radian of the Galactic Plane was scanned by the H.E.S.S. (High Energy Stereoscopic System) telescopes at energies above 200 GeV. This survey was performed from -$3^o$ to +$3^o$ in latitude, for a total of 230 hours, revealing eight new VHE sources at a significance level greater than 6$σ$(standard deviations). We present a multi-resolution analysis of these sources based on a continuous wavelet transformation (CWT). Using CO and HI data, we investigate the possible associations of the potential counterparts proposed in [1], with sites of enhanced interstellar matter density.

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arXiv2006

An INTEGRAL/IBIS view of Young Galactic SNRs through the 44Ti gamma-ray lines

We present preliminary results of INTEGRAL/IBIS observations on Cas A, Tycho and Vela Junior Supernova remnants in the line emission of 44Ti. This radioactive nucleus is thought to be exclusively produced in supernovae during the first stages of the explosion. It has a lifetime of about 87 y and is then the best indicator of young SNRs, as exemplified by the detection of 44Ti in the youngest known Galactic SNR Cas A with GRO/COMPTEL and latter with BeppoSAX. In this paper, we will focus on this SNR for which we confirm the detection of 44Ti and point out the importance to know the nature of the hard X-ray continuum, the Tycho SNR, for which no indication of 44Ti was ever reported, and Vela Junior, for which the claimed detection of 44Ti with COMPTEL is still controversial. The INTEGRAL/IBIS observations bring new constraints on the nature of these SNRs and on the nucleosynthesis which took place during the explosions.

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arXiv2005

INTEGRAL detection of hard X-rays from NGC 6334: Nonthermal emission from colliding winds or an AGN?

We report the detection of hard X-ray emission from the field of the star-forming region NGC 6334 with the the International Gamma-Ray Astrophysics Laboratory INTEGRAL. The JEM-X monitor and ISGRI imager aboard INTEGRAL and Chandra ACIS imager were used to construct 3-80 keV images and spectra of NGC 6334. The 3-10 keV and 10-35 keV images made with JEM-X show a complex structure of extended emission from NGC 6334. The ISGRI source detected in the energy ranges 20-40 keV and 40-80 keV coincides with the NGC 6334 ridge. The 20-60 keV flux from the source is (1.8+-0.37)*10(-11) erg cm(-2) s(-1). Spectral analysis of the source revealed a hard power-law component with a photon index about 1. The observed X-ray fluxes are in agreement with extrapolations of X-ray imaging observations of NGC 6334 by Chandra ACIS and ASCA GIS. The X-ray data are consistent with two very different physical models. A probable scenario is emission from a heavily absorbed, compact and hard Chandra source that is associated with the AGN candidate radio source NGC 6334B. Another possible model is the extended Chandra source of nonthermal emission from NGC 6334 that can also account for the hard X-ray emission observed by INTEGRAL. The origin of the emission in this scenario is due to electron acceleration in energetic outflows from massive early type stars. The possibility of emission from a young supernova remnant, as suggested by earlier infrared observations of NGC 6334, is constrained by the non-detection of 44Ti lines.

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