arXiv subjects

B. McBreen

Publications and source records attributed to B. McBreen.

At least 37 records · Page 2Linked to original sources

arXiv2005

The galaxies in the field of the nearby GRB980425/SN1998bw

We present spectroscopic observations of ESO 184-G82, the host galaxy of GRB980425/SN1998bw, and six galaxies in its field. A host redshift of z=0.0087+/-0.0006 is derived, consistent with that measured by Tinney et al. (1998). Redshifts are obtained for the six surrounding galaxies observed. Three of these galaxies lie within 11 Mpc of each other, confirming the suggestion that some of these galaxies form a group. However, all of the field galaxies observed lie at significantly greater distances than ESO 184-G82 and are therefore not associated with it. The host galaxy of GRB980425/SN1998bw thus appears to be an isolated dwarf galaxy and interactions with other galaxies do not seem to be responsible for its star formation.

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arXiv2005

INTEGRAL and XMM-Newton observations of the low-luminosity and X-ray rich burst GRB 040223

GRB 040223 was observed by INTEGRAL and XMM-Newton. GRB 040223 has a peak flux of (1.6+/-0.13) x10^-8 ergs cm^-2 s^-1, a fluence of (4.4+/-0.4)x10^-7 ergs cm^-2 and a steep photon power law index of -2.3+/-0.2, in the energy range 20-200 keV. The steep spectrum implies it is an x- ray rich GRB with emission up to 200 keV and E_peak < 20 keV. If E_peak is < 10 keV, it would qualify as an x-ray flash with high energy emission. The x-ray data has a spectral index beta_x = -1.7+/-0.2, a temporal decay of t^(-0.75+/-0.25) and a large column density of (1.8 x 10^22) cm^-2. The luminosity-lag relationship was used to obtain a redshift (z = 0.1+0.04-0.02). The isotropic energy radiated in gamma-rays and x-ray luminosity after 10 hours are factors of 1000 and 100 less than classical GRBs. GRB 040223 is consistent with the extrapolation of the Amati relation into the region that includes XRF 030723 and XRF 020903.

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arXiv2005

ISO observations of the interacting galaxy Markarian 297: with the powerful supernova remnant 1982aa

Markarian (Mkn) 297 is a complex system with two interacting galaxies. Observations were made with ISO using ISOCAM, ISOPHOT and LWS. We present ISOCAM maps at 6.7, 7.7, 12 and 14.3 microns which, with PHT-S spectrometry of the central interacting region, probe the dust obscured star formation and dust properties. ISOCAM reveals that the strongest emission region in the four MIR bands is completely unremarkable at visible and near-IR (e.g. 2MASS) wavelengths, and does not coincide with the nuclear region of either colliding galaxy. It shares this striking characteristic with the overlap region of the colliding galaxies in the Antennae (NGC 4038, 4039), the intragroup region of Stephan's Quintet, and IC 694 in the interacting system Arp 299. At 15 microns, the hidden source in Mkn 297 is, respectively, 14.6 and 3.8 times more luminous than the hidden sources in the Antennae (NGC 4038/4039) and Stephan's Quintet. Numerical simulations indicate that we see the Mkn 297 interaction about 1.5 x 10e8 years after the collision. ISOCAM shows knots and ridges of emission. The 14.3/7.7 micron ratio map implies widespread strong star formation. Strong emission features were detected in the ISOPHOT spectrum, while [OI], [OIII] and [CII] emission lines were seen with LWS. Using data from the three instruments, luminosities and masses for two dust components were determined. The total infrared luminosity is approximately 10e11 L_sol, marginally a LIRG. A 1979 supernova generated one of the most powerful known radio remnants (SN 1982aa) close to the strongest MIR source and identified with star forming region 14 in the optical. This exceptional supernova explosion may have been accompanied by a GRB, and a search for a GRB in this direction in contemporaneous satellite data is recommended.

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arXiv2005

ISO observations of the Wolf-Rayet galaxies NGC 5430, NGC 6764, Mrk 309 and VII Zw 19

Observations of four WR galaxies (NGC 5430, NGC 6764, Mrk 309 and VII Zw 19) using the Infrared Space Observatory are presented here. ISOCAM maps of NGC 5430, Mrk 309 and NGC 6764 revealed the location of star formation regions in each of these galaxies. ISOPHOT spectral observations from 4 to 12 microns detected the ubiquitous PAH bands in the nuclei of the targets and several of the disk star forming regions, while LWS spectroscopy detected [OI] and [CII] emission lines from two galaxies, NGC 5430 and NGC 6764. Using a combination of ISO and IRAS flux densities, a dust model based on the sum of modified blackbody components was successfully fitted to the available data. These models were then used to calculate new values for the total IR luminosities for each galaxy, the size of the various dust populations, and the global SFR. The derived flux ratios, the SFRs, the high L(PAH)/L(40-120 microns) and F(PAH 7.7 microns)/F(7.7 microns continuum) values suggest that most of these galaxies are home to only a compact burst of star formation. The exception is NGC 6764, whose F(PAH 7.7 microns)/F(7.7 microns continuum) value of 1.22 is consistent with the presence of an AGN, yet the L(PAH)/L(40-120 microns) is more in line with a starburst, a finding in line with a compact low-luminosity AGN dominated by the starburst.

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arXiv2005

Out of the darkness: the infrared afterglow of the INTEGRAL burst GRB 040422 observed with the VLT

GRB 040422 was detected by the INTEGRAL satellite at an angle of only 3 degrees from the Galactic plane. Analysis of the prompt emission observed with the SPI and IBIS instruments on INTEGRAL are presented. The IBIS spectrum is well fit by the Band model with a break energy of Eo=56+/-2 keV and Epeak=41+/-3 keV. The peak flux is 1.8 10^(-7) erg/cm2/s and fluence 3.4 10^(-7) erg/cm2 in the range 20-200 keV. We then present the observations of the afterglow of GRB 040422, obtained with the ISAAC and FORS 2 instruments at the VLT less than 2 hours after the burst. We report the discovery of its near-infrared afterglow, for which we give here the astrometry and photometry. No detection could have been obtained in the R and I bands, partly due to the large extinction in the Milky Way. We re-imaged the position of the afterglow two months later in the Ks band, and detected a likely bright host galaxy. We compare the magnitude of the afterglow with a those of a compilation of promptly observed counterparts of previous GRBs, and show that the afterglow of GRB 040422 lies at the very faint end of the distribution, brighter only than that of GRB 021211, singled out later and in the optical bands, and GRB 040924 after accounting for Milky Way extinction. This observation suggests that the proportion of dark GRBs can be significantly lowered by a more systematic use of 8-m class telescopes in the infrared in the very early hours after the burst.

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arXiv2005

Gamma-ray bursts and other sources of giant lightning discharges in protoplanetary systems

Lightning in the solar nebula is considered to be one of the probable sources for producing the chondrules that are found in meteorites. Gamma-ray bursts (GRBs) provide a large flux of gamma-rays that Compton scatter and create a charge separation in the gas because the electrons are displaced from the positive ions. The electric field easily exceeds the breakdown value of ~1 V m^-1 over distances of order 0.1 AU. The energy in a giant lightning discharge exceeds a terrestrial lightning flash by a factor of ~10^12. The predicted post-burst emission of gamma-rays from accretion into the newly formed black hole or spin-down of the magnetar is sufficiently intense to cause a lightning storm in the nebula that lasts for days and is more probable than the GRB because the radiation is beamed into a larger solid angle. The giant outbursts from nearby soft gamma-ray repeater sources (SGRs) are also capable of causing giant lightning discharges. The total amount of chondrules produced is in reasonable agreement with the observations of meteorites. Furthermore in the case of GRBs most chondrules were produced in a few major melting events by nearby GRBs and lightning occurred at effectively the same time over the whole nebula, and provide accurate time markers to the formation of chondrules and evolution of the solar nebula. This model provides a reasonable explanation for the delay between the formation of calcium aluminium inclusions (CAIs) and chondrules.

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arXiv2004

INTEGRAL and XMM-Newton Observations of GRB040106

On January 6th 2004, the IBAS burst alert system triggered the 8th gamma-ray burst (GRB) to be located by the INTEGRAL satellite. The position was determined and publicly distributed within 12s, prompting ESA's XMM-Newton to execute a ToO observation just 5 hours later, during which an X-ray afterglow was detected. The GRB had a duration ~52s with two distinct pulses separated by \~42s. Here we present the results of imaging and spectral analyses of the prompt emission from INTEGRAL data and the X-ray afterglow from XMM-Newton data. The gamma-ray spectrum is consistent with a single power-law of photon index -1.72 +/- 0.15. The fluence (20-200 keV) was 8.2 x 10^-7 erg cm^-2. The X-ray afterglow (F_nu (t) propto nu^-beta_X t^-delta) was extremely hard with beta_X = 0.47 +/- 0.01 and delta = 1.46 +/- 0.04. The 2-10 keV flux 11 hours after the burst was 1.1 x 10^-12 erg cm^-2 s^-1. The time profile of the GRB is consistent with the observed trends from previous analysis of BATSE GRBs. We find that the X-ray data are not well-fit by either a simple spherical fireball or by a speading jet, expanding into a homogeneous medium or a wind environment. Based on previously determined correlations between GRB spectra and redshift, we estimate a redshift of ~0.9^+0.5_-0.4 (1 sigma) and a lower limit on the isotropic radiated energy of ~5 x 10^51 erg in this burst.

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arXiv2004

The XMM-LSS survey. Survey design and first results

We have designed a medium deep large area X-ray survey with XMM - the XMM Large Scale Structure survey, XMM-LSS - with the scope of extending the cosmological tests attempted using ROSAT cluster samples to two redshift bins between 0<z<1 while maintaining the precision of earlier studies. Two main goals have constrained the survey design: the evolutionary study of the cluster-cluster correlation function and of the cluster number density. The results are promising and, so far, in accordance with our predictions as to the survey sensitivity and cluster number density. The feasibility of the programme is demonstrated and further X-ray coverage is awaited in order to proceed with a truly significant statistical analysis. (Abridged)

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arXiv2004

Gamma-ray bursts and X-ray melting of material as a potential source of chondrules and planets

The intense radiation from a gamma-ray burst (GRB) is shown to be capable of melting stony material at distances up to 300 light years which subsequently cool to form chondrules. These conditions were created in the laboratory for the first time when millimeter sized pellets were placed in a vacuum chamber in the white synchrotron beam at the European Synchrotron Radiation Facility (ESRF). The pellets were rapidly heated in the X-ray and gamma-ray furnace to above 1400 C melted and cooled. This process heats from the inside unlike normal furnaces. The melted spherical samples were examined with a range of techniques and found to have microstructural properties similar to the chondrules that come from meteorites. This experiment demonstrates that GRBs can melt precursor material to form chondrules that may subsequently influence the formation of planets. This work extends the field of laboratory astrophysics to include high power synchrotron sources.

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arXiv2004

Gamma-ray bursts and X-ray melting of material to form chondrules and planets

Chondrules are millimeter sized objects of spherical to irregular shape that constitute the major component of chondritic meteorites that originate in the region between Mars and Jupiter and which fall to Earth. They appear to have solidified rapidly from molten or partially molten drops. The heat source that melted the chondrules remains uncertain. The intense radiation from a gamma-ray burst (GRB) is capable of melting material at distances up to 300 light years. These conditions were created in the laboratory for the first time when millimeter sized pellets were placed in a vacuum chamber in the white synchrotron beam at the European Synchrotron Radiation Facility. The pellets were rapidly heated in the X-ray and gamma-ray furnace to above 1400C melted and cooled. This process heats from the inside unlike normal furnaces. The melted spherical samples were examined with a range of techniques and found to have microstructural properties similar to the chondrules that come from meteorites. This experiment demonstrates that GRBs can melt precursor material to form chondrules that may subsequently influence the formation of planets. This work extends the field of laboratory astrophysics to include high power synchrotron sources.

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arXiv2004

ISOCAM Observations of Intermediate-redshift Galaxy Clusters at 7 and 15 microns

The gravitationally lensing clusters A370, A2218, A1689 and CL0024+1654 were observed with the Infrared Space Observatory (ISO) using ISOCAM at 6.7 and 14.3 microns (hereafter 7 and 15 microns respectively). A total of 178 sources were detected in the whole set, 70 of them being cluster objects. The spectral energy distribution of a subset of sources was calculated using GRASIL. The results for the total infrared luminosity and the estimation of the star formation rate are presented for the non stellar objects for which the SED has been determined. The majority of the cluster galaxies in A2218 are best fit by models of quiescent ellipticals. In Cl0024+1654, most of the galaxies lying on the Butcher-Oemler region of the colour-magnitude diagram are best fit by disk galaxies, while those on the main sequence area have in general SEDs corresponding to post-starburst galaxies. The population of each cluster is compared with the field population, as well as with the population of other clusters. A significant number of Luminous IR Galaxies (LIRGs) is detected in CL0024+1654, while only one LIRG has been observed in total in A370, A1689, and A2218. This result supports the link between LIRGs in clusters and recent or ongoing cluster merger activity as well as the need for extending the observations to the outer parts of clusters.

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arXiv2004

An ISOCAM survey through gravitationally lensing galaxy clusters. II. The properties of infrared galaxies in the A2218 field

We observed the cluster Abell 2218 (z=0.175), with ISOCAM on board the Infrared Space Observatory, using two filters with reference wavelengths of 6.7 and 14.3 microns. We detected 67 extragalactic mid-infrared sources. Using the ``GRASIL'' models of Silva et al. (1998) we have obtained acceptable and well constrained fits to the observed spectral energy distributions (SEDs) of 41 of these sources, for which additional optical/near-infrared magnitudes, and, in some cases, redshifts, were available. We have then determined the total infrared luminosities and star formation rates (SFRs) of these 41 sources, of which 27 are cluster members and 14 are field galaxies at a median redshift z~0.6. The SEDs of most of the ISOCAM cluster members are best fit by models with negligible star formation in the last ~1 Gyr. The 7 faintest cluster members have a slightly higher, but still very mild, star-formation activity. The ISOCAM-selected cluster galaxies appear to be an unbiased subsample of the overall cluster population. If A2218 is undergoing a merger, as suggested by some optical and X-ray analyses, then this merger does not seem to affect the mid-infrared properties of its galaxies. The SEDs of most ISOCAM-selected field sources are best fit by models with significant ongoing (and recent) star formation, resembling those of massive star-forming spirals or (post)starburst galaxies. Their median SFR is 22 solar masses per year. Eight of the 14 field sources are Luminous IR Galaxies. (Abridged)

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arXiv2004

Clusters of galaxies in the mid-infrared

We describe the results of observations of galaxy clusters conducted with ISOCAM on-board the Infrared Space Observatory. Our research is aimed at understanding the processes driving galaxy evolution in dense environments, free from the bias of dust extinction. The results reveal quite a complex picture: the star-formation activity of cluster galaxies does not show a simple evolution with redshift, but also depends on the dynamical status and evolutionary history of the clusters.

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arXiv2004

Preliminary INTEGRAL Analysis of GRB040106

On January 6th 2004, the IBAS burst alert system triggered the 8th gamma-ray burst (GRB) to be detected by the INTEGRAL satellite. The position was determined and publicly distributed within 12s, enabling ESA's XMM-Newton to take advantage of a ToO observation just 5 hours later during which the x-ray afterglow was detected. Observations at optical wavelengths also revealed the existence of a fading optical source. The GRB is ~52s long with 2 distinct peaks separated by ~24s. At gamma-ray energies the burst was the weakest detected by INTEGRAL up to that time with a flux in the 20-200 keV band of 0.57 photons/cm^2/s. Nevertheless, it was possible to determine its position and extract spectra and fluxes. Here we present light curves and the results of imaging, spectral and temporal analyses of the prompt emission and the onset of the afterglow from INTEGRAL data.

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arXiv2004

XMM-Newton observations of the BL Lac MS0205.7+3509: a dense, low-metallicity absorber

The high-frequency-peaked BL Lac, MS0205.7+3509 was observed twice with XMM-Newton. Both X-ray spectra are synchrotron-dominated, with mean 0.2--10keV fluxes of 2.80+/-0.01 and 3.34+/-0.02 E-12 erg/cm^2/s. The X-ray spectra are well fit by a power-law with absorption above the Galactic value, however no absorption edges are detected, implying a low metallicity absorber (Z_\sun = 0.04(+0.03)(-0.01)) or an absorber with redshift above one (best-fit z=2.1 for an absorber with solar abundances). In either case the absorbing column density must be ~9E21 cm^-2. A new optical spectrum is presented, with a MgII absorption doublet detected at z=0.351, but no other significant features. The optical spectrum shows little reddening, implying a low dust to gas ratio in the absorber. MS0205.7+3509 must therefore be viewed through a high column density, low-metallicity gas cloud, probably at z=0.351 and associated with the galaxy that has been shown to be within ~2" of the BL Lac.

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arXiv2004

INTEGRAL Spectrometer Analysis of GRB030227 & GRB030131

The spectrometer SPI on board INTEGRAL is capable of high-resolution spectroscopic studies in the energy range 20keV to 8MeV for GRBs which occur within the fully coded field of view (16 degrees corner to corner). Six GRBs occurred within the SPI field of view between October 2002 and November 2003. We present results of the analysis of the first two GRBs detected by SPI after the payload performance and verification phase of INTEGRAL.

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arXiv2003

Similarities in the temporal properties of gamma-ray bursts and soft gamma-ray repeaters

Magnetars are modelled as sources that derive their output from magnetic energy that substantially exceeds their rotational energy. An implication of the recent polarization measurement of GRB 021206 is that the emission mechanism may be dominated by a magnetic field that originates in the central engine. Similarities in the temporal properties of SGRs and GRBs are considered in light of the fact that the central engine in GRBs may be magnetically dominated. The results show that 1) the time intervals between outbursts in SRG 1806-20 and pulses in GRBs are consistent with lognormal distributions and 2) the cumulative outputs of SGRs and GRBs increase linearly with time. This behaviour can be successfully modelled by a relaxation system that maintains a steady state situation.

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arXiv2003

INTEGRAL Spectrometer SPI's GRB detection capabilities. GRBs detected inside SPI's FoV and with the anticoincidence system ACS

The spectrometer SPI, one of the two main instruments of the INTEGRAL spacecraft, offers significant gamma-ray burst detection capabilities. In its 35 deg (full width) field of view SPI is able to localise gamma-ray bursts at a mean rate of ~ 0.8/month. With its large anticoincidence shield of 512 kg of BGO crystals SPI is able to detect gamma-ray bursts quasi omni-directionally with a very high sensitivity. Burst alerts of the anticoincidence shield are distributed by the INTEGRAL Burst Alert System. In the first 8 months of the mission about 0.8/day gamma-ray burst candidates and 0.3/day gamma-ray burst positions were obtained with the anticoincidence shield by interplanetary network triangulations with other spacecrafts.

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