A Sub-Saturn Mass Planet, MOA-2009-BLG-319Lb

We report the gravitational microlensing discovery of a sub-Saturn mass planet, MOA-2009-BLG-319Lb, orbiting a K- or M-dwarf star in the inner Galactic disk or Galactic bulge. The high-cadence observations of the MOA-II survey discovered this microlensing event and enabled its identification as a high-magnification event approximately 24 hr prior to peak magnification. As a result, the planetary signal at the peak of this light curve was observed by 20 different telescopes, which is the largest number of telescopes to contribute to a planetary discovery to date. The microlensing model for this event indicates a planet-star mass ratio of q = (3.95 ± 0.02) × 10^(–4) and a separation of d = 0.97537 ± 0.00007 in units of the Einstein radius. A Bayesian analysis based on the measured Einstein radius crossing time, t_E, and angular Einstein radius, θ_E, along with a standard Galactic model indicates a host star mass of M_L = 0.38^(+0.34)_(–0.18) M_☉ and a planet mass of M_p = 50^(+44)_(–24) M_⊕, which is half the mass of Saturn. This analysis also yields a planet-star three-dimensional separation of a = 2.4^(+1.2)_(–0.6) AU and a distance to the planetary system of D_L = 6.1^(+1.1)_(–1.2) kpc. This separation is ~2 times the distance of the snow line, a separation similar to most of the other planets discovered by microlensing

SDSS J131339.98+515128.3: A new gravitationally lensed quasar selected based on near-infrared excess

We report the discovery of a new gravitationally lensed quasar, SDSS J131339.98+515128.3, at a redshift of 1.875 with an image separation of 1.24". The lensing galaxy is clearly detected in visible-light follow-up observations. We also identify three absorption-line doublets in the spectra of the lensed quasar images, from which we measure the lens redshift to be 0.194. Like several other known lenses, the lensed quasar images have different continuum slopes. This difference is probably the result of reddening and microlensing in the lensing galaxy. The lensed quasar was selected by correlating Sloan Digital Sky Survey (SDSS) spectroscopic quasars with Two Micron All Sky Survey (2MASS) sources and choosing quasars that show near-infrared (IR) excess. The near-IR excess can originate, for example, from the contribution of the lensing galaxy at near-IR wavelengths. We show that the near-IR excess technique is indeed an efficient method to identify lensed systems from a large sample of quasars.Comment: Accepted to MNRAS, 8 pages, 7 figure

The Role of Interactions in an Electronic Fabry-Perot Interferometer Operating in the Quantum Hall Effect Regime

Interference of edge channels is expected to be a prominent tool for studying statistics of charged quasiparticles in the quantum Hall effect (QHE) [A. Stern (2008), Ann. Phys. 1:204; C. Chamon et al. (1997), Phys. Rev. B, 55:2331]. We present here a detailed study of an electronic Fabry-Perot interferometer (FPI) operating in the QHE regime [C. Chamon et al. (1997), Phys. Rev. B, 55:2331], with the phase of the interfering quasiparticles controlled by the Aharonov-Bohm (AB) effect. Our main finding is that Coulomb interactions among the electrons dominate the interference, even in a relatively large area FPI, leading to a strong dependence of the area enclosed by the interference loop on the magnetic field. In particular, for a composite edge structure, with a few independent edge channels propagating along the edge, interference of the outmost edge channel (belonging to the lowest Landau level) was insensitive to magnetic field; suggesting a constant enclosed flux. However, when any of the inner edge channels interfered, the enclosed flux decreased when the magnetic field increased. By intentionally varying the enclosed area with a biased metallic gate and observing the periodicity of the interference pattern, charges e (for integer filling factors) and e/3 (for a fractional filling factor) were found to be expelled from the FPI. Moreover, these observations provided also a novel way of detecting the charge of the interfering quasiparticles.Comment: 8 pages, 8 figure

A Very Large Array Search for 5 GHz Radio Transients and Variables at Low Galactic Latitudes

We present the results of a 5 GHz survey with the Very Large Array (VLA) and the expanded VLA, designed to search for short-lived (≾1 day) transients and to characterize the variability of radio sources at milli-Jansky levels. A total sky area of 2.66 deg^2, spread over 141 fields at low Galactic latitudes (b≅6-8 deg), was observed 16 times with a cadence that was chosen to sample timescales of days, months, and years. Most of the data were reduced, analyzed, and searched for transients in near real-time. Interesting candidates were followed up using visible light telescopes (typical delays of 1-2 hr) and the X-ray Telescope on board the Swift satellite. The final processing of the data revealed a single possible transient with a peak flux density of f_ν≅2.4 mJy. This implies a transient's sky surface density of κ(f_ν > 1.8 mJy) = 0.039^(+0.13 +0.18)_(–0.032,–0.038) deg^(–2) (1σ, 2σ confidence errors). This areal density is roughly consistent with the sky surface density of transients from the Bower et al. survey extrapolated to 1.8 mJy. Our observed transient areal density is consistent with a neutron star's origin for these events. Furthermore, we use the data to measure the source variability on timescales of days to years, and we present the variability structure function of 5 GHz sources. The mean structure function shows a fast increase on ≈1 day timescale, followed by a slower increase on timescales of up to 10 days. On timescales between 10 and 60 days, the structure function is roughly constant. We find that ≳30% of the unresolved sources brighter than 1.8 mJy are variables at the >4σ confidence level, presumably mainly due to refractive scintillation

ULAS J234311.93-005034.0: A gravitational lens system selected from UKIDSS and SDSS

We report the discovery of a new gravitational lens system. This object, ULAS J234311.93-005034.0, is the first to be selected by using the new UKIRT Infrared Deep Sky Survey (UKIDSS), together with the Sloan Digital Sky Survey (SDSS). The ULAS J234311.93-005034.0 system contains a quasar at redshift 0.788 which is doubly imaged, with separation 1.4". The two quasar images have the same redshift and similar, though not identical, spectra. The lensing galaxy is detected by subtracting point-spread functions from R-band images taken with the Keck telescope. The lensing galaxy can also be detected by subtracting the spectra of the A and B images, since more of the galaxy light is likely to be present in the latter. No redshift is determined from the galaxy, although the shape of its spectrum suggests a redshift of about 0.3. The object's lens status is secure, due to the identification of two objects with the same redshift together with a lensing galaxy. Our imaging suggests that the lens is found in a cluster environment, in which candidate arc-like structures, that require confirmation, are visible in the vicinity. Further discoveries of lenses from the UKIDSS survey are likely as part of this programme, due to the depth of UKIDSS and its generally good seeing conditions.Comment: Accepted by MNRA

Far-Ultraviolet to Near-Infrared Spectroscopy of A Nearby Hydrogen Poor Superluminous Supernova Gaia16apd

We report the first maximum-light far-Ultraviolet to near-infrared spectra (1000A - 1.62um, rest) of a H-poor superluminous supernova, Gaia16apd. At z=0.1018, it is one of the closest and the UV brightest such events, with 17.4 (AB) magnitude in Swift UV band (1928A) at -11days pre-maximum. Assuming an exponential form, we derived the rise time of 33days and the peak bolometric luminosity of 3x10^{44}ergs^-1. At maximum light, the estimated photospheric temperature and velocity are 17,000K and 14,000kms^-1 respectively. The inferred radiative and kinetic energy are roughly 1x10^{51} and 2x10^{52}erg. Gaia16apd is extremely UV luminous, emitting 50% of its total luminosity at 1000 - 2500A. Compared to the UV spectra (normalized at 3100A) of well studied SN1992A (Ia), SN2011fe(Ia), SN1999em (IIP) and SN1993J (IIb), it has orders of magnitude more far-UV emission. This excess is interpreted primarily as a result of weaker metal line blanketing due to much lower abundance of iron-group elements in the outer ejecta. Because these elements originate either from the natal metallicity of the star, or have been newly produced, our observation provides direct evidence that little of these freshly synthesized material, including 56Ni, was mixed into the outer ejecta, and the progenitor metallicity is likely sub-solar. This disfavors Pair-Instability Supernova (PISN) models with Helium core masses >=90Msun, where substantial 56Ni material is produced. Higher photospheric temperature of Gaia16apd than that of normal SNe may also contribute to the observed far-UV excess. We find some indication that UV luminous SLSNe-I like Gaia16apd could be common. Using the UV spectra, we show that WFIRST could detect SLSNe-I out to redshift of 8.Comment: 19 pages. Match with the version accepted in Ap

Discovery of Multiply Imaged Galaxies behind the Cluster and Lensed Quasar SDSS J1004+4112

We have identified three multiply imaged galaxies in Hubble Space Telescope images of the redshift z=0.68 cluster responsible for the large-separation quadruply lensed quasar, SDSS J1004+4112. Spectroscopic redshifts have been secured for two of these systems using the Keck I 10m telescope. The most distant lensed galaxy, at z=3.332, forms at least four images, and an Einstein ring encompassing 3.1 times more area than the Einstein ring of the lensed QSO images at z=1.74, due to the greater source distance. For a second multiply imaged galaxy, we identify Ly_alpha emission at a redshift of z=2.74. The cluster mass profile can be constrained from near the center of the brightest cluster galaxy, where we observe both a radial arc and the fifth image of the lensed quasar, to the Einstein radius of the highest redshift galaxy, ~110 kpc. Our preliminary modeling indicates that the mass approximates an elliptical body, with an average projected logarithmic gradient of ~-0.5. The system is potentially useful for a direct measurement of world models in a previously untested redshift range.Comment: 5 pages, 3 figures. Accepted by ApJL. High resolution version of the paper can be found at: http://wise-obs.tau.ac.il/~kerens/papers.htm

The Lensed Arc Production Efficiency of Galaxy Clusters: A Comparison of Matched Observed and Simulated Samples

We compare the statistical properties of giant gravitationally lensed arcs produced in matched simulated and observed cluster samples. The observed sample consists of 10 X-ray selected clusters at redshifts z ~ 0.2 imaged with HST by Smith et al. The simulated dataset is produced by lensing the Hubble Deep Field, which serves as a background source image, with 150 realizations (different projections and shifts) of five simulated z = 0.2 clusters from a LambdaCDM N-body simulation. The real and simulated clusters have similar masses, the real photometric redshift is used for each background source, and all the observational effects influencing arc detection in the real dataset, including light from cluster galaxies, are simulated in the artificial dataset. We develop, and apply to both datasets, an objective automatic arc-finding algorithm. We find consistent arc statistics in the real and in the simulated sample, with an average of ~ 1 detected giant (length to width ratio >= 10) arc per cluster and ~ 0.2 giant luminous (R<22.3 mag) arc per cluster. Thus, taking into account a realistic source population and observational effects, the clusters predicted by LambdaCDM have the same arc-production efficiency as the observed clusters. If, as suggested by other studies, there is a discrepancy between the predicted and the observed total number of arcs on the sky, it must be the result of differences between the redshift dependent cluster mass functions, and not due to differences in the lensing efficiency of the most massive clusters.Comment: 13 pages, Accepted by ApJ, High resolution version of the paper can be found at: ftp://wise3.tau.ac.il/pub/assafh/horesh_arcs_stat_2005.ps.gz, Arc-finding algorithm available at: http://wise-obs.tau.ac.il/~assafh/ ; A comment was added ; A missing x-axis label in Fig. 7 was adde