Optical studies of two LMC X-ray transients : RX J0544.1-7100 and RX J0520.5-6932

We report observations which confirm the identities of the optical counterpart to the transient sources RX J0544.1-7100 and RX J0520.5-6932. The counterparts are suggested to be a B-type stars. Optical data from the observations carried out at ESO and SAAO, together with results from the OGLE data base, are presented. In addition, X-ray data from the RXTE all-sky monitor are investigated for long term periodicities. A strong suggestion for a binary period of 24.4d is seen in RX J0520.5-6932 from the OGLE data.Comment: 6 pages, 7 figure

A Comprehensive Library of X-ray Pulsars in the Small Magellanic Cloud: Time Evolution of their Luminosities and Spin Periods

We have collected and analyzed the complete archive of {\itshape XMM-Newton\} (116), {\itshape Chandra\} (151), and {\itshape RXTE\} (952) observations of the Small Magellanic Cloud (SMC), spanning 1997-2014. The resulting observational library provides a comprehensive view of the physical, temporal and statistical properties of the SMC pulsar population across the luminosity range of $L_X= 10^{31.2}$--$10^{38}$~erg~s$^{-1}$. From a sample of 67 pulsars we report $\sim$1654 individual pulsar detections, yielding $\sim$1260 pulse period measurements. Our pipeline generates a suite of products for each pulsar detection: spin period, flux, event list, high time-resolution light-curve, pulse-profile, periodogram, and spectrum. Combining all three satellites, we generated complete histories of the spin periods, pulse amplitudes, pulsed fractions and X-ray luminosities. Some pulsars show variations in pulse period due to the combination of orbital motion and accretion torques. Long-term spin-up/down trends are seen in 12/11 pulsars respectively, pointing to sustained transfer of mass and angular momentum to the neutron star on decadal timescales. Of the sample 30 pulsars have relatively very small spin period derivative and may be close to equilibrium spin. The distributions of pulse-detection and flux as functions of spin-period provide interesting findings: mapping boundaries of accretion-driven X-ray luminosity, and showing that fast pulsars ($P<$10 s) are rarely detected, which yet are more prone to giant outbursts. Accompanying this paper is an initial public release of the library so that it can be used by other researchers. We intend the library to be useful in driving improved models of neutron star magnetospheres and accretion physics.Comment: 17 pages, 11 + 58 (appendix) figures. To appear in the Astrophysical Journal Supplemen

The binary period and outburst behaviour of the SMC X-ray binary pulsar system SXP504

A probable binary period has been detected in the optical counterpart to the X-ray source CXOU J005455.6-724510 = RX J0054.9-7245 = AXJ0054.8-7244 = SXP504 in the Small Magellanic Cloud. This source was detected by Chandra on 04 Jul 2002 and subsequently observed by XMM-Newton on 18 Dec 2003. The source is coincident with an Optical Gravitational Lensing (OGLE) object in the lightcurves of which several optical outburst peaks are visible at ~ 268 day intervals. Timing analysis shows a period of 268.6 +/- 0.1 days at > 99% significance. Archival Rossi X-ray Timing Explorer (RXTE) data for the 504s pulse-period has revealed detections which correspond closely with predicted or actual peaks in the optical data. The relationship between this orbital period and the pulse period of 504s is within the normal variance found in the Corbet diagram.Comment: Accepted by MNRAS. 1 LATEX page. 4 figure

A Free-Form Lensing Grid Solution for A1689 with New Mutiple Images

Hubble Space Telescope imaging of the galaxy cluster Abell 1689 has revealed an exceptional number of strongly lensed multiply-imaged galaxies, including high-redshift candidates. Previous studies have used this data to obtain the most detailed dark matter reconstructions of any galaxy cluster to date, resolving substructures ~25 kpc across. We examine Abell 1689 (hereafter, A1689) non-parametrically, combining strongly lensed images and weak distortions from wider field Subaru imaging, and we incorporate member galaxies to improve the lens solution. Strongly lensed galaxies are often locally affected by member galaxies, however, these perturbations cannot be recovered in grid based reconstructions because the lensing information is too sparse to resolve member galaxies. By adding luminosity-scaled member galaxy deflections to our smooth grid we can derive meaningful solutions with sufficient accuracy to permit the identification of our own strongly lensed images, so our model becomes self consistent. We identify 11 new multiply lensed system candidates and clarify previously ambiguous cases, in the deepest optical and NIR data to date from Hubble and Subaru. Our improved spatial resolution brings up new features not seen when the weak and strong lensing effects are used separately, including clumps and filamentary dark matter around the main halo. Our treatment means we can obtain an objective mass ratio between the cluster and galaxy components, for examining the extent of tidal stripping of the luminous member galaxies. We find a typical mass-to-light ratios of M/L_B = 21 inside the r<1 arcminute region that drops to M/L_B = 17 inside the r<40 arcsecond region. Our model independence means we can objectively evaluate the competitiveness of stacking cluster lenses for defining the geometric lensing-distance-redshift relation in a model independent way.Comment: 23 pages with 25 figures Replced with MNRAS submitted version. Some figures have been corrected and minor text edit

Free-form lens model and mass estimation of the high redshift galaxy cluster ACT-CL J0102-4915, "El Gordo"

We examine the massive colliding cluster El Gordo, one of the most massive clusters at high redshift. We use a free-form lensing reconstruction method that avoids making assumptions about the mass distribution. We use data from the RELICS program and identify new multiply lensed system candidates. The new set of constraints and free-form method provides a new independent mass estimate of this intriguing colliding cluster. Our results are found to be consistent with earlier parametric models, indirectly confirming the assumptions made in earlier work. By fitting a double gNFW profile to the lens model, and extrapolating to the virial radius, we infer a total mass for the cluster of $M_{200c}=(1.08^{+0.65}_{-0.12})\times10^{15}$M$_{\odot}$. We estimate the uncertainty in the mass due to errors in the photometric redshifts, and discuss the uncertainty in the inferred virial mass due to the extrapolation from the lens model. We also find in our lens map a mass overdensity corresponding to the large cometary tail of hot gas, reinforcing its interpretation as a large tidal feature predicted by hydrodynamical simulations that mimic El Gordo. Finally, we discuss the observed relation between the plasma and the mass map, finding that the peak in the projected mass map may be associated with a large concentration of colder gas, exhibiting possible star formation. El Gordo is one of the first clusters that will be observed with JWST, which is expected to unveil new high redshift lensed galaxies around this interesting cluster, and provide a more accurate estimation of its mass.Comment: 19 pages, 10 figures. Updated figure

The bright-end galaxy candidates at z ~ 9 from 79 independent HST fields

We present a full data analysis of the pure-parallel Hubble Space Telescope (HST) imaging observations in the Brightest of Reionizing Galaxies Survey (BoRG[z9]) in Cycle 22. The medium-deep exposures with five HST/WFC3IR+UVIS filter bands from 79 independent sightlines (~370 arcmin^2) provide the least biased determination of number density for z>9 bright galaxies against cosmic variance. After a strict two-step selection for candidate galaxies, including dropout color and photometric redshift analyses, and revision of previous BoRG candidates, we identify one source at z~10 and two sources at z~9. The z~10 candidate shows evidence of line-of-sight lens magnification (mu~1.5), yet it appears surprisingly luminous (MUV ~ -22.6\pm0.3 mag), making it one of the brightest candidates at z > 8 known (~ 0.3 mag brighter than the z = 8.68 galaxy EGSY8p7, spectroscopically confirmed by Zitrin and collaborators). For z ~ 9 candidates, we include previous data points at fainter magnitudes and find that the data are well fitted by a Schechter luminosity function with alpha ~ -2.1, MUV ~ -21.5 mag, and log phi ~ -4.5 Mpc^-3mag^-1, for the first time without fixing any parameters. The inferred cosmic star formation rate density is consistent with unaccelerated evolution from lower redshift.Comment: 18pages, 7figures, 6tables. accepted to the Astrophysical Journa

Through the Looking Glass: Bright, Highly Magnified Galaxy Candidates at z~7 Behind Abell 1703

We report the discovery of seven strongly lensed Lyman break galaxy (LBG) candidates at z~7 detected in Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) imaging of Abell 1703. The brightest candidate, called A1703-zD1, has an observed (lensed) magnitude of 24.0 AB (26 sigma) in the WFC3/IR F160W band, making it 0.2 magnitudes brighter than the z_850-dropout candidate recently reported behind the Bullet Cluster and 0.7 magnitudes brighter than the previously brightest known z~7.6 galaxy, A1689-zD1. With a cluster magnification of ~9, this source has an intrinsic magnitude of H_160 = 26.4 AB, a strong z_850 - J_125 break of 1.7 magnitudes, and a photometric redshift of z~6.7. Additionally, we find six other bright LBG candidates with H_160 band magnitudes of 24.9-26.4, photometric redshifts z~6.4 - 8.8, and magnifications mu~3-40. Stellar population fits to the ACS, WFC3/IR, and \Spitzer/IRAC data for A1703-zD1 and A1703-zD4 yield stellar masses (0.7 - 3.0) x 10^{9} M_sun, stellar ages 5-180 Myr, and star-formation rates ~7.8 M_sun/yr, and low reddening with A_V <= 0.7. The source-plane reconstruction of the exceptionally bright candidate A1703-zD1 exhibits an extended structure, spanning ~4 kpc in the z~6.7 source plane, and shows three resolved star-forming knots of radius r~0.4 kpc.Comment: 11 pages, 8 figures, 2 tables; ApJ, accepted for publicatio

Remarkable dynamics of nanoparticles in the urban atmosphere

Nanoparticles emitted from road traffic are the largest source of respiratory exposure for the general public living in urban areas. It has been suggested that the adverse health effects of airborne particles may scale with the airborne particle number, which if correct, focuses attention on the nanoparticle (less than 100 nm) size range which dominates the number count in urban areas. Urban measurements of particle size distributions have tended to show a broadly similar pattern dominated by a mode centred on 20–30 nm diameter particles emitted by diesel engine exhaust. In this paper we report the results of measurements of particle number concentration and size distribution made in a major London park as well as on the BT Tower, 160 m high. These measurements taken during the REPARTEE project (Regents Park and BT Tower experiment) show a remarkable shift in particle size distributions with major losses of the smallest particle class as particles are advected away from the traffic source. In the Park, the traffic related mode at 20–30 nm diameter is much reduced with a new mode at <10 nm. Size distribution measurements also revealed higher number concentrations of sub-50 nm particles at the BT Tower during days affected by higher turbulence as determined by Doppler Lidar measurements and indicate a loss of nanoparticles from air aged during less turbulent conditions. These results suggest that nanoparticles are lost by evaporation, rather than coagulation processes. The results have major implications for understanding the impacts of traffic-generated particulate matter on human health

High-dispersion spectroscopic monitoring of the Be/X-ray binary A0535+26/V725 Tau I: The long-term profile variability

We report on optical high-dispersion spectroscopic monitoring observations of the Be/X-ray binary A0535+26/V725 Tau, carried out from November 2005 to March 2009. The main aim of these monitoring observations is to study spectral variabilities in the Be disc, on both the short (a week or so) and long (more than hundreds of days) timescales, by taking long-term frequent observations. Our four-year spectroscopic observations indicate that the V/R ratio, i.e., the relative intensity of the violet (V) peak to the red (R) one, of the double-peaked H-alpha line profile varies with a period of 500 days. The H-beta line profile also varies in phase with the H-alpha profile. With these observations covering two full cycles of the V/R variability, we reconstruct the 2-D structure of the Be disc by applying the Doppler tomography method to the H-alpha and H-beta emission line profiles, using a rigidly rotating frame with the V/R variability period. The resulting disc structure reveals non-axisymmetric features, which can be explained by a one-armed perturbation in the Be disc. It is the first time that an eccentric disc structure is directly detected by using a method other than the interferometric one.Comment: (10 pages, 9 figures, accepted to MNRAS

Mice lacking C1q or C3 show accelerated rejection of minor H disparate skin grafts and resistance to induction of tolerance

Complement activation is known to have deleterious effects on organ transplantation. On the other hand, the complement system is also known to have an important role in regulating immune responses. The balance between these two opposing effects is critical in the context of transplantation. Here, we report that female mice deficient in C1q (C1qa(−/−)) or C3 (C3(−/−)) reject male syngeneic grafts (HY incompatible) at an accelerated rate compared with WT mice. Intranasal HY peptide administration, which induces tolerance to syngeneic male grafts in WT mice, fails to induce tolerance in C1qa(−/−) or C3(−/−) mice. The rejection of the male grafts correlated with the presence of HY D(b)Uty-specific CD8(+) T cells. Consistent with this, peptide-treated C1qa(−/−) and C3(−/−) female mice rejecting male grafts exhibited more antigen-specific CD8(+)IFN-γ(+) and CD8(+)IL-10(+) cells compared with WT females. This suggests that accumulation of IFN-γ- and IL-10-producing T cells may play a key role in mediating the ongoing inflammatory process and graft rejection. Interestingly, within the tolerized male skin grafts of peptide-treated WT mice, IFN-γ, C1q and C3 mRNA levels were higher compared to control female grafts. These results suggest that C1q and C3 facilitate the induction of intranasal tolerance