Brian McBreen

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

OMC: An Optical Monitoring Camera for INTEGRAL Instrument description and performance

The Optical Monitoring Camera (OMC) will observe the optical emission from the prime targets of the gamma- ray instruments onboard the ESA mission INTEGRAL, with the support of the JEM-X monitor in the X-ray domain. This capability will provide invaluable diagnostic information on the nature and the physics of the sources over a broad wavelength range. Its main scientific objectives are: (1) to monitor the optical emission from the sources observed by the gamma- and X-ray instruments, measuring the time and intensity structure of the optical emission for comparison with variability at high energies, and (2) to provide the brightness and position of the optical counterpart of any gamma- or X-ray transient taking place within its field of view. The OMC is based on a refractive optics with an aperture of 50 mm focused onto a large format CCD (1024 2048 pixels) working in frame transfer mode (1024 1024 pixels imaging area). With a field of view of 5 5 it will be able to monitor sources down to magnitude V = 18. Typical observations will perform a sequence of dierent integration times, allowing for photometric uncertainties below 0.1 mag for objects with V 16.

An ISOCAM survey through gravitationally lensing galaxy clusters - I. Source lists and source counts for A370, A2218 and A2390

PCT No. PCT/DE89/00650 Sec. 371 Date Mar. 6, 1991 Sec. 102(e) Date Mar. 6, 1991 PCT Filed Oct. 12, 1989 PCT Pub. No. WO90/04702 PCT Pub. Date May 3, 1990.A partial flue gas stream is used for the production of electrical energy and/or heating and operational heat by utilizing combustion heat from fossil fuels, prior to combustion dried in an indirectly heated fluidized bed dryer, with combustion flue gas used as a carrier medium for the fluidized bed dryer. The mixture of flue gases and steam, deriving from the drying process, is after an intermediate treatment, if necessary, discharged with the main flue gas stream.

Temporal properties of gamma ray bursts as signatures of jets from the central engine

A comprehensive temporal analysis has been performed on the 319 brightest GRBs with T90 > 2s from the BATSE current catalog. The GRBs were denoised using wavelets and subjected to an automatic pulse selection algorithm as an objective way of identifying pulses and quantifying the eects of neighbouring pulses. The number of statistically signicant pulses selected from the sample was greater than 3000. The rise times, fall times, full-widths at half-maximum (FWHM), pulse amplitudes and pulse areas were measured and the frequency distributions are presented here. All are consistent with lognormal distributions provided the pulses are well separated. The distribution of time intervals between pulses is not random but compatible with a lognormal distribution when allowance was made for the 64 ms time resolution and a small excess (5%) of long duration intervals that is often referred to as a Pareto-L evy tail. The time intervals between pulses are most important because they may be an almost direct measure of the activity in the central engine. Lognormal distributions of time intervals also occur in pulsars and SGR sources and therefore provide indirect evidence that the time intervals between pulses in GRBs are also generated by rotation powered systems with super-strong magnetic elds. A range of correlations are presented on pulse and burst properties. The rise and fall times, FWHM and area of the pulses are highly correlated with each other. The pulse amplitudes are anticorrelated with the FWHM. The time intervals between pulses and pulse amplitudes of neighbouring pulses are correlated with each other. It was also found that the number of pulses, N, in GRBs is strongly correlated with the fluence and duration and that can explain the well known correlation between duration and fluence. The GRBs were sorted into three categories based on N i.e. 3 N 12, 13 N 24 and N 25. The properties of pulses before and after the strongest pulse were compared for three categories of bursts. No major dierences were found between the distributions of the pulse properties before and after the strongest pulse in the GRB. However there is a strong trend for pulses to have slower rise times and faster fall times in the rst half of the burst and this pattern is strongest for category 3 N 12. This analysis revealed that the GRBs with large numbers of pulses have narrower and faster pulses and also larger fluences, longer durations and higher hardness ratios than the GRBs with smaller numbers of pulses. These results may be explained by either homogeneous or inhomogeneous jet models of GRBs. The GRBs with larger number of pulses are closer to the axis if varies with the opening angle of the jet and the imprint of the jet is preserved in the pulse structure of the burst. The distribution of the number of pulses per GRB broadly reflects the beaming by the jet.

The awakening of BL Lacertae: observations by Fermi, Swift and the GASP-WEBT

Since the launch of the Fermi satellite, BL Lacertae has been moderately active at ?-rays and optical frequencies until 2011 May, when the source started a series of strong flares. The exceptional optical sampling achieved by the GLAST–AGILE Support Program of the Whole Earth Blazar Telescope in collaboration with the Steward Observatory allows us to perform a detailed comparison with the daily ?-ray observations by Fermi. Discrete correlation analysis between the optical and ?-ray emission reveals correlation with a time lag of 0 ± 1 d, which suggests cospatiality of the corresponding jet emitting regions. A better definition of the time lag is hindered by the daily gaps in the sampling of the extremely fast flux variations. In general, optical flares present more structure and develop on longer time-scales than corresponding ?-ray flares. Observations at X-rays and at millimetre wavelengths reveal a common trend, which suggests that the region producing the mm and X-ray radiation is located downstream from the optical and ?-ray-emitting zone in the jet. The mean optical degree of polarization slightly decreases over the considered period and in general it is higher when the flux is lower. The optical electric vector polarization angle (EVPA) shows a preferred orientation of about 15°, nearly aligned with the radio core EVPA and mean jet direction. Oscillations around it increase during the 2011–2012 outburst. We investigate the effects of a geometrical interpretation of the long-term flux variability on the polarization. A helical magnetic field model predicts an evolution of the mean polarization that is in reasonable agreement with the observations. These can be fully explained by introducing slight variations in the compression factor in a transverse shock waves model.

Temporal properties of the short gamma-ray bursts

A temporal analysis has been performed on a sample of 100 bright gamma-ray bursts (GRBs) with T90 2 s. The two sub-classes of GRBs appear to have the same emission mechanism which is probably caused by internal shocks. They may not have the same progenitors because of the generic nature of the reball model.

Flares from a candidate Galactic magnetar suggest a missing link to dim isolated neutron stars

Magnetars are young neutron stars with very strong magnetic fields of the order of 1014–1015 G. They are detected in our Galaxy either as soft γ-ray repeaters or anomalous X-ray pulsars. Soft γ-ray repeaters are a rare type of γ-ray transient sources that are occasionally detected as bursters in the high-energy sky. No optical counterpart to the γ-ray flares or the quiescent source has yet been identified. Here we report multi-wavelength observations of a puzzling source, SWIFT J195509+261406. We detected more than 40 flaring episodes in the optical band over a time span of three days, and a faint infrared flare 11 days later, after which the source returned to quiescence. Our radio observations confirm a Galactic nature and establish a lower distance limit of ∼3.7 kpc. We suggest that SWIFT J195509+261406 could be an isolated magnetar whose bursting activity has been detected at optical wavelengths, and for which the long-term X-ray emission is short-lived. In this case, a new manifestation of magnetar activity has been recorded and we can consider SWIFT J195509+261406 to be a link between the ‘persistent’ soft γ-ray repeaters/anomalous X-ray pulsars and dim isolated neutron stars.A. J. Castro-Tirado, A. de Ugarte Postigo, J. Gorosabel, M. Jeĺınek, T. A. Fatkhullin, V. V. Sokolov, P. Ferrero, D. A. Kann, S. Klose, D. Sluse, M. Bremer, J. M. Winters, D. Nuernberger, D. Pérez-Ramı́rez, M. A. Guerrero, J. French, G. Melady, L. Hanlon, B. McBreen, F. J. Aceituno, R. Cunniffe, P. Kubánek, S. Vitek, S. Schulze, A. C. Wilson, R. Hudec, J. M. González-Pérez, T. Shahbaz, S. Guziy, S. B. Pandey L. Pavlenko, E. Sonbas, S. A. Trushkin, N. N. Bursov, N. A. Nizhelskij and L. Sabau-Graziati

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

We have observed the cluster Abell 2218 (z = 0.175) with ISOCAM on board the Infrared Space Observatory using two filters, LW2 and LW3, with reference wavelengths of 6.7 and 14.3 μm, respectively. We detected 76 sources down to 54 and 121 μJy (50% completeness levels) at 6.7 and 14.3 μm, respectively. All these sources have visible optical counterparts. We have gathered optical and near-infrared magnitudes for 60 of the 67 non-stellar optical counterparts to the ISOCAM sources, as well as redshifts for 43 of them. We have obtained acceptable and well constrained fits to the observed spectral energy distributions (SEDs) of 41 of these sources, using the GRASIL models of Silva et al. (1998), and have determined their total infrared luminosities (L IR s) and star formation rates (SFRs). The SEDs of 20 (out of 27) ISOCAM cluster members are best fit by models with negligible ongoing star formation, and no major episode of star formation in the last 1 Gyr. Their SEDs resemble those of 5-10 Gyr old early-type galaxies. A slightly higher, but still very mild, star-formation activity is found among the remaining cluster sources, which are mostly spirals. The median IR luminosity of the 27 ISOCAM cluster sources is L IR = 6 x 10 8 L ○. . The ISOCAM-selected cluster galaxies have indistinguishable velocity and spatial distributions from those of the other cluster galaxies, and do not contribute significantly to the Butcher-Oemler effect. 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 moderate ongoing star formation, with a significant fraction of their stellar mass formed in the last ∼1 Gyr. Their SEDs resemble those of massive star-forming spirals or starburst galaxies, observed close to the maximum of their star formation activity, but not necessarily during the short-lived starburst event. The median redshift of these field galaxies is z ≃ 0.6. Their L IR s span almost two orders of magnitudes, from ∼10 10 L ○. to 10 12 L ○. , with a median of 1.2 x 10 11 (eight of the 14 field sources are LIRGs). The SFRs of these 14 ISOCAM-selected field sources range from 2 to 125 M ○. yr -1 , with a median value of 22 M ○. yr -1 . We compare our findings with those obtained in other ISOCAM cluster and field surveys.

A search for rapid optical variability in radio-quiet quasars

The detection of rapid variability on a timescale of hours in radio-quiet quasars (RQQSOs) could be a powerful discriminator between starburst, accretion disc and relativistic jet models of these sources. This paper contains an account of a dedicated search for rapid optical variability in RQQSOs. The technique used differential photometry between the RQQSO and stars in the same field of view of the CCD. The 23 RQQSOs that were observed all have high luminosities (), and 22 of these sources are at redshifts . The total amount of observation time was about 60 hours and these observations are part of an ongoing programme, started in September 1990, to search for rapid variability in RQQSOs. No evidence for short-term variability greater than about 0.1 magnitudes was detected in any of the 23 sources, however long-term variability was recorded for the radio-quiet quasar PG 2112+059. The finding charts are included here because they identify the RQQSO and the reference stars used in the photometry, and hence are available for use by other observers. The unusual properties of two RQQSOs that were not included in our source list are noted. X-ray results reveal that PG 1416-129 is variable on a timescale of days and that the remarkable source IRAS 13349+2438 varied by a factor of two on a timescale of a few hours. The latter source displayed blazar type behaviour in X-rays and implies that relativistic beaming may occur in at least some RQQSOs. Radio results also indicate the presence of jets in at least some RQQSOs.

Infrared Space Observatory Observations of Hickson Compact Group 31 with the Central Wolf-Rayet Galaxy NGC 1741

Hickson Compact Group (HCG) 31, consisting of the Wolf-Rayet galaxy NGC 1741 and its irregular dwarf companions, was observed using the Infrared Space Observatory. The deconvolved ISOCAM maps of the galaxies using the 7.7 and 14.3 ?m (LW6 and LW3) filters are presented, along with ISOPHOT spectrometry of the central starburst region of NGC 1741 and the nucleus of galaxy HCG 31A. Strong mid-IR emission was detected from the central burst in NGC 1741, along with strong polycyclic aromatic hydrocarbon (PAH) features and a blend of features, including [S?IV] at 10.5 ?m. The 14.3/6.75 ?m flux ratio, for which the 6.75 ?m flux was synthesized from the PHT-S spectrum, and 14.3/7.7 ?m flux ratio suggest that the central burst within NGC 1741 may be moving toward the poststarburst phase. Diagnostic tools including the ratio of the integrated PAH luminosity to the 40-120 ?m infrared luminosity and the far-infrared colors reveal that despite the high surface brightness of the nucleus, the properties of NGC 1741 can be explained in terms of a starburst and do not require the presence of an active galactic nucleus. The Tycho catalog star Tyc 04758 466 1, with mV = 11.3 and spectral type F6, was detected at 7.7 and 14.3 ?m.