Optical and X-ray emission from stable millisecond magnetars formed from the merger of binary neutron stars

The coalescence of binary neutron stars (NSs) may in some cases produce a stable massive NS remnant rather than a black hole. Due to the substantial angular momentum from the binary, such a remnant is born rapidly rotating and likely acquires a strong magnetic field (a `millisecond magnetar'). Magnetic spin-down deposits a large fraction of the rotational energy from the magnetar behind the small quantity of mass ejected during the merger. This has the potential for creating a bright transient that could be useful for determining whether a NS or black hole was formed in the merger. We investigate the expected signature of such an event, including for the first time the important impact of electron/positron pairs injected by the millisecond magnetar into the surrounding nebula. These pairs cool via synchrotron and inverse Compton emission, producing a pair cascade and hard X-ray spectrum. A fraction of these X-rays are absorbed by the ejecta walls and re-emitted as thermal radiation, leading to an optical/UV transient peaking at a luminosity of ~1e43-1e44 erg/s on a timescale of several hours to days. This is dimmer than predicted by simpler analytic models because the large optical depth of electron/positron pairs across the nebula suppresses the efficiency with which the magnetar spin down luminosity is thermalized. Nevertheless, the optical/UV emission is more than two orders of magnitude brighter than a radioactively powered `kilonova.' In some cases nebular X-rays are sufficiently luminous to re-ionize the ejecta, in which case non-thermal X-rays escape the ejecta unattenuated with a similar peak luminosity and timescale as the optical radiation. We discuss the implications of our results for the temporally extended X-ray emission that is observed to follow some short gamma-ray bursts (GRBs), including the kilonova candidates GRB 080503 and GRB 130603B.Comment: 13 pages, 8 figures, 2 appendices, submitted to MNRA

Supernova Fallback onto Magnetars and Propeller-powered Supernovae

We explore fallback accretion onto newly born magnetars during the supernova of massive stars. Strong magnetic fields (~10^(15) G) and short spin periods (~1-10 ms) have an important influence on how the magnetar interacts with the infalling material. At long spin periods, weak magnetic fields, and high accretion rates, sufficient material is accreted to form a black hole, as is commonly found for massive progenitor stars. When B ≾ 5 × 10^(14) G, accretion causes the magnetar to spin sufficiently rapidly to deform triaxially and produces gravitational waves, but only for ≈50-200 s until it collapses to a black hole. Conversely, at short spin periods, strong magnetic fields, and low accretion rates, the magnetar is in the "propeller regime" and avoids becoming a black hole by expelling incoming material. This process spins down the magnetar, so that gravitational waves are only expected if the initial protoneutron star is spinning rapidly. Even when the magnetar survives, it accretes at least ≈0.3 M_☉, so we expect magnetars born within these types of environments to be more massive than the 1.4 M_☉ typically associated with neutron stars. The propeller mechanism converts the ~10^(52)erg of spin energy in the magnetar into the kinetic energy of an outflow, which shock heats the outgoing supernova ejecta during the first ~10-30 s. For a small ~5 M_☉ hydrogen-poor envelope, this energy creates a brighter, faster evolving supernova with high ejecta velocities ~(1-3) × 10^4 km s^(–1) and may appear as a broad-lined Type Ib/c supernova. For a large ≳ 10 M_☉ hydrogen-rich envelope, the result is a bright Type IIP supernova with a plateau luminosity of ≳ 10^(43)erg s^(–1) lasting for a timescale of ~60-80 days

Possible identifications of the 3.4 micrometer feature

A feature at 3.4 micrometer was first detected in Comet Halley by the IKS spectrometer on board the Vega 1 probe; and subsequently from the ground. The feature has since been reported in Comet Wilson. The presence of the feature is of considerable interest for a number of reasons. First, it may represent the detection of a new parent molecule, and when combined with data from Giotto and Vega yield new information on cometary chemistry and the early solar system composition. Secondly, it may represent a link to the interstellar medium, the feature corresponds in wavelength and shape with an interstellar feature seen in absorption in a luminous star, towards the Galactic center known as GC-IRS7. The feature in turn is thought to be related with a growing family of unidentified infrared emission features seen in stellar objects, planetary nebulae, reflection nebulae, HII regions and extra galactic sources. These features occur at wavelengths 3.3, 3.4, 3.5, 6.2, 7.7, 8.6, and 11.25 micrometers. Further identification theory is given

Numerical Modeling of the Early Light Curves of Type IIP Supernovae

The early rise of Type IIP supernovae (SN IIP) provides important information for constraining the properties of their progenitors. This can in turn be compared to pre-explosion imaging constraints and stellar models to develop a more complete picture of how massive stars evolve and end their lives. Using the SuperNova Explosion Code (SNEC), we model the first 40 days of SNe IIP to better understand what constraints can be derived from their early light curves. We use two sets of red supergiant progenitor models with zero-age main sequence masses in the range between 9 Msol and 20 Msol. We find that the early properties of the light curve depend most sensitively on the radius of the progenitor, and thus provide a relation between the g-band rise time and the radius at the time of explosion. This relation will be useful for deriving constraints on progenitors from future observations, especially in cases where detailed modeling of the entire rise is not practical. When comparing to observed rise times, the radii we find are a factor of a few larger than previous semi-analytic derivations and generally in better agreement with what is found with current stellar evolution calculations.Comment: 8 pages, 7 figure

Multi-photon effects in energy losses spectra

Effect of radiation of many photons by a single electron traversing a target is discussed. When the summary energy of emitted photons (the energy losses spectrum) is measured only, the photon spectrum is distorted comparing with the photon spectrum in one interaction. Influence of this effect is discussed for the cases (1) bremsstrahlung (described by Bethe-Heitler formula), (2) the strong Landau-Pomeranchuk-Migdal effect and (3) transition radiation. Qualitative picture of the phenomenon is discussed in detail. Comparison with the recent SLAC experiment in relatively thick target (2.7% of the radiation length), where the effect of emission of many photons by a projectile is very essential, shows perfect agreement of the theory and data.Comment: LaTeX2.09, 19 pages, 5 PostScript figure

Laser anemometer measurements in a transonic axial-flow fan rotor

Laser anemometer surveys were made of the 3-D flow field in NASA rotor 67, a low aspect ratio transonic axial-flow fan rotor. The test rotor has a tip relative Mach number of 1.38. The flowfield was surveyed at design speed at near peak efficiency and near stall operating conditions. Data is presented in the form of relative Mach number and relative flow angle distributions on surfaces of revolution at nine spanwise locations evenly spaced from hub to tip. At each spanwise location, data was acquired upstream, within, and downstream of the rotor. Aerodynamic performance measurements and detailed rotor blade and annulus geometry are also presented so that the experimental results can be used as a test case for 3-D turbomachinery flow analysis codes

The External Validity of a Novel Contract-Relax Stretching Technique on Knee Flexor Range of Motion

INTRODUCTION: Compromised joint range of motion (ROM) can negatively affect the capacity to perform activities of daily living in clinical populations. Recently, similar improvements in dorsiflexion ROM were reported following dynamometry-based contract-relax (CR) stretching and modified CR stretching technique (stretch-return-contract [SRC]) where the contraction phase was performed "off stretch." As neither the impact of SRC on other muscle groups nor the ecological validity of SRC performed in an applied environment has been tested, the acute effects of both techniques in dynamometry- (CR dyna and SRC dyna ) and field-based (CR field and SRC field ) environments were compared with the hamstring muscle group. METHODS: Seventeen participants performed each of the four stretching conditions on separate days in a randomized order. Before and after the stretches, knee extension ROM and passive knee flexor moment were recorded on an isokinetic dynamometer. RESULTS: Significant (P .05) in any measure was found between conditions. CONCLUSIONS: These data confirm the acute efficacy of the SRC technique in the hamstring muscle group and demonstrate its ecological validity in an applied environment in healthy participants. As the field-based SRC technique was performed without partner assistance, when compared with classical PNF it represents an equally effective and practical stretching paradigm to support athletic and clinical exercise prescription

On the Insignificance of Photochemical Hydrocarbon Aerosols in the Atmospheres of Close-in Extrasolar Giant Planets

The close-in extrasolar giant planets (CEGPs) reside in irradiated environments much more intense than that of the giant planets in our solar system. The high UV irradiance strongly influences their photochemistry and the general current view believed that this high UV flux will greatly enhance photochemical production of hydrocarbon aerosols. In this letter, we investigate hydrocarbon aerosol formation in the atmospheres of CEGPs. We find that the abundances of hydrocarbons in the atmospheres of CEGPs are significantly less than that of Jupiter except for models in which the CH$_4$ abundance is unreasonably high (as high as CO) for the hot (effective temperatures $\gtrsim 1000$ K) atmospheres. Moreover, the hydrocarbons will be condensed out to form aerosols only when the temperature-pressure profiles of the species intersect with the saturation profiles--a case almost certainly not realized in the hot CEGPs atmospheres. Hence our models show that photochemical hydrocarbon aerosols are insignificant in the atmospheres of CEGPs. In contrast, Jupiter and Saturn have a much higher abundance of hydrocarbon aerosols in their atmospheres which are responsible for strong absorption shortward of 600 nm. Thus the insignificance of photochemical hydrocarbon aerosols in the atmospheres of CEGPs rules out one class of models with low albedos and featureless spectra shortward of 600 nm.Comment: ApJL accepte