Search

Roughly 10% of quasars are "radio-loud", producing copious radio emission in large jets. The origin of the low-level radio emission seen from the remaining 90% of quasars is unclear. Observing a sample of eight radio-quiet quasars with the Very Long Baseline Array, we discovered that their radio properties depend strongly on their Eddington ratio (r_Edd=L_AGN/L_Edd). At lower Eddington ratios (r_Edd < 0.3), the total radio emission of the AGN predominately originates from an extremely compact region, possibly as small as the accretion disk. At higher Eddington ratios (r_Edd > 0.3), the relative contribution of this compact region decreases significantly, and though the total radio power remains about the same, the emission now originates from regions >100 pc large. The change in the physical origin of the radio-emitting plasma region with r_Edd is unexpected, as the properties of radio-loud quasars show no dependence with Eddington ratio. Our results suggest that at lower Eddington ratios the magnetised plasma is likely confined by the accretion disk corona, and only at higher Eddington ratios escapes to larger scales. Stellar-mass black holes show a similar dependence of their radio properties on the accretion rate, supporting the paradigm which unifies the accretion onto black holes across the mass range., 17 pages, 4 figures, 6 tables. Accepted for publication in The Astrophysical Journal (ApJ)

The emission from the accreting black holes (BHs) in low-mass X-ray binaries (LMXBs) covers a broad energy band from radio to X-rays. Studying the correlations between emission in different energy bands during outbursts can provide valuable information about the accretion process. We analyse the simultaneous optical, ultraviolet (UV) and X-ray data of the BH-LMXB Swift J1753.5-0127 during its $\sim$ 12-year long outburst with the {\it Neil Gehrels Swift Observatory}. We find that the UV/optical and X-ray emission are strongly correlated during the hard states of the outburst. We fit the relation with a power-law function $F_{UV/optical} \propto F_{X}^{\beta}$ and find that the power-law index $\beta$ increases from $\sim$ 0.24 to $\sim$ 0.33 as the UV/optical wavelength decreases from $\sim$ 5400 \r{A} (V) to $\sim$ 2030 \r{A} (UVW2). We explore the possible reasons for this and suggest that in Swift J1753.5-0127 the UV/optical emission is dominated by a viscously heated accretion disc at large radii. We find that the data that deviate from the correlation correspond to the low-intensity peaks appeared in the X-ray band during the outburst, and suggest that these deviations are driven by the emission from the inner part of the accretion disc., Comment: 15 pages, 8 figures, 1 table, accepted by MNRAS

Powered by the rotational energy of a neutron star, studying pulsar wind nebulae (PWNe) is important for understanding the origin of the highest energy cosmic rays leptons in the Milky Way. HESS J1640-465, by virtue of being among the most luminous TeV sources in the galaxy, must accelerate a considerable number of leptons to PeV energies, and its association with PSR J1640-4631 – the first pulsar to have a braking index > 3, the result of NuSTAR observations – suggest these particles are produced in its PWN. To better understand the physical conditions under which these particles are generated, we will present new and updated measurements of the X-ray properties of the PWN associated with HESS J1640-465 in the soft (3-10 keV) and hard X-ray band (10-30 keV), derived primarily from NuSTAR observations. Using our results, we fit the broadband properties of our system using an evolutionary model of a PWN inside a SNR, which improves our understanding of the physical conditions under which these high energy particles are produced, allowing us to evaluate models for their acceleration.

Given their prominent role in galaxy evolution, it is of paramount importance to unveil galaxy interactions and merger events and to investigate the underlying mechanisms. The use of high-resolution data makes it easier to identify merging systems, but it can still be challenging when the morphology does not show any clear galaxy-pair or gas bridge. Characterising the origin of puzzling kinematic features can help to reveal complicated systems. Here, we present a merging galaxy, MaNGA 1-114955, in which we highlighted the superimposition of two distinct rotating discs along the line of sight. These counter-rotating objects both lie on the star-forming main sequence but display perturbed stellar velocity dispersions. The main galaxy presents off-centred star formation as well as off-centred high-metallicity regions supporting the scenario of recent starbursts, while the secondary galaxy hosts a central starburst which coincides with an extended radio emission, in excess with respect to star formation expectations. Stellar mass as well as dynamical mass estimates agree towards a mass ratio within the visible radius of 9:1 for these interacting galaxies. We suggest we are observing a pre-coalescence stage of a merger. The primary galaxy has accreted gas through a past first pericentre passage about 1 Gyr ago, and more recently from the secondary gas-rich galaxy, which exhibits an underlying active galactic nucleus (AGN). Our results demonstrate how a galaxy can hide another one and the relevance of a multi-component approach to study ambiguous systems. We anticipate our method to be efficient at unveiling the mechanisms taking place in a sub-sample of galaxies observed by the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, all exhibiting kinematic features of puzzling origin in their gas emission lines., 13 pages, 14 figures. Accepted for publication in Astronomy and Astrophysics

We report recent progress on the ongoing NuSTAR observational campaign of 8 TeV-detected pulsar wind nebulae (PWNe). This campaign constitutes a major part of our NuSTAR study of some of the most energetic TeV sources in our galaxy detected by VERITAS and HAWC. NuSTAR is the first focusing X-ray telescope operating above 10 keV in space with sub-arcminute angular resolution. Broad-band X-ray imaging and spectroscopy data, obtained by NuSTAR, allow us to probe sub-PeV electron populations through detecting synchrotron X-ray radiation. Our targets include PeVatron candidates detected by HAWC, the Boomerang nebula, PWNe crushed by supernova remnant shocks (or relic PWNe), and G0.9+0.1 in the Galactic Center. Using Fermi-LAT data and available TeV data, we aim to provide a complete, multi-wavelength view of a diverse class of middle-aged (~10-100 kyrs old) PWNe. Our NuSTAR analysis detected hard X-ray emission from the Eel and Boomerang PWNe and characterized their broad-band X-ray spectra most accurately. We plan to apply both time-evolution and multi-zone PWN models to multi-wavelength spectral energy distribution (SED) data over the radio, X-ray, GeV, and TeV bands. In this proceeding, we will review our observational campaign and discuss the preliminary results for some PWNe.

HAWC J1826-128 is one of the brightest Galactic TeV gamma-ray sources detected by the High Altitude Water Cherenkov (HAWC) Observatory, with photon energies extending up to nearly $\sim$100 TeV. This HAWC source spatially coincides with the H.E.S.S. TeV source HESS J1826-130 and the "Eel" pulsar wind nebula (PWN), which is associated with the GeV pulsar PSR J1826-1256. In the X-ray band, Chandra and XMM-Newton revealed that the Eel PWN is composed of both a compact nebula ($\sim$15") and diffuse X-ray emission ($\sim$6'$\times$2') extending away from the pulsar. Our NuSTAR observation detected hard X-ray emission from the compact PWN up to $\sim$20 keV and evidence of the synchrotron burn-off effect. In addition to the spatial coincidence between HESS J1826-130 and the diffuse X-ray PWN, our multi-wavelength spectral energy distribution (SED) analysis using X-ray and gamma-ray data establishes a leptonic origin of the TeV emission associated with the Eel PWN. Furthermore, our evolutionary PWN SED model suggests (1) a low PWN B-field of $\sim$1 $\mu$G, (2) a significantly younger pulsar age ($t \sim5.7$ kyr) than the characteristic age ($\tau= 14.4$ kyr) and (3) a maximum electron energy of $E_{max} = 2$ PeV. The low B-field as well as the putative supersonic motion of the pulsar may account for the asymmetric morphology of the diffuse X-ray emission. Our results suggest that the Eel PWN may be a leptonic PeVatron particle accelerator powered by the $\sim$6-kyr-old pulsar PSR J1826-1256 with a spin-down power of $3.6 \times 10^{36}$ erg s$^{-1}$., Comment: 19 pages, 12 figures

Galaxies in dense environments, such as groups and clusters, experience various processes by which galaxies gain and lose gas. Using data from the SDSS-IV MaNGA survey, we previously reported the discovery of a giant (6 -- 8 kpc in diameter) H$\alpha$ blob, Totoro, about 8 kpc away from a pair of galaxies (Satsuki and Mei) residing in a galaxy group which is experiencing a group-group merger. Here, we combine interferometric $^{12}$CO(1--0) molecular gas data, new wide-field H$\alpha$, $u$-band data, and published X-ray data to determine the origin of the blob. Several scenarios are discussed to account for its multi-wavelength properties, including (1) H$\alpha$ gas being stripped from galaxy Satsuki by ram-pressure; (2) a separated low-surface-brightness galaxy; (3) gas being ejected or ionized by an active galactic nucleus (AGN); and (4) a cooling intra-group medium (IGM). Scenarios (1) and (2) are less favored by the present data. Scenario (3) is also less likely as there is no evidence for an active ongoing AGN in the host galaxy. We find that the CO (cold) and H$\alpha$ (warm) gas coexist with X-ray (hot) structures; moreover, the derived cooling time is within the regime where molecular and H$\alpha$ gas are expected. The coexistence of gas with different temperatures also agrees with that of cooling gas in other systems. Our multi-wavelength results strongly suggest that the CO and H$\alpha$ gas are the product of cooling from the IGM at its current location, i.e., cooling has occurred, and may be ongoing, well outside the host-galaxy core., Comment: 23 pages, 10 figures, Accepted for publication in ApJ

The evolution of a pulsar wind nebula (PWN) depends on properties of the progenitor star, supernova, and surrounding environment. As some of these quantities are difficult to measure, reproducing the observed dynamical properties and spectral energy distribution (SED) with an evolutionary model is often the best approach in estimating their values. G21.5-0.9, powered by the pulsar J1833-1034, is a well observed PWN for which previous modeling efforts have struggled to reproduce the observed SED. In this study, we reanalyze archival infrared (IR; Herschel, Spitzer) and X-ray (Chandra, NuSTAR, Hitomi) observations. The similar morphology observed between IR line and continuum images of this source indicates that a significant portion of this emission is generated by surrounding dust and gas, and not synchrotron radiation from the PWN. Furthermore, we find the broadband X-ray spectrum of this source is best described by a series of power laws fit over distinct energy bands. For all X-ray detectors, we find significant softening and decreasing unabsorbed flux at higher energy bands. Our model for the evolution of a PWN is able to reproduce the properties of this source when the supernova ejecta has a low initial kinetic energy $E_{\mathrm{sn}} \approx 1.2 \times 10^{50}\,\mathrm{ergs}$ and the spectrum of particles injected into the PWN at the termination shock is softer at low energies. Lastly, our hydrodynamical modeling of the SNR can reproduce its morphology if there is a significant density increase of the ambient medium ${\sim} 1.8$ pc north of the explosion center., 24 pages, 15 figures, accepted for publication in The Astrophysical Journal (accepted manuscript); corrected typo in standard deviation equation of appendix

We report the stellar atmospheric parameters for 7503 spectra contained in the first release of the MaNGA stellar library (MaStar) in SDSS DR15. The first release of MaStar contains 8646 spectra measured from 3321 unique stars, each covering the wavelength range 3622 \AA\ to 10354 \AA\ with a resolving power of $R \sim$ 1800. In this work, we first determined the basic stellar parameters: effective temperature ($\rm T_{eff}$), surface gravity ($\log g$), and metallicity ($\rm[Fe/H]$), which best fit the data using an empirical interpolator based on the Medium-resolution Isaac Newton Telescope library of empirical spectra (MILES), as implemented by the University of Lyon Spectroscopic analysis Software (Koleva et al. 2008, ULySS) package. While we analyzed all 8646 spectra from the first release of MaStar, since MaStar has a wider parameter-space coverage than MILES, not all of these fits are robust. In addition, not all parameter regions covered by MILES yield robust results, likely due to the non-uniform coverage of the parameter space by MILES. We tested the robustness of the method using the MILES spectra itself and identified a proxy based on the local density of the training set. With this proxy, we identified 7503 MaStar spectra with robust fitting results. They cover the range from 3179K to 20,517K in effective temperature ($\rm T_{eff}$), from 0.40 to 5.0 in surface gravity ($\log g$), and from $-$2.49 to $+$0.73 in metallicity ($\rm[Fe/H]$)., Comment: 14 pages, 13 figures

We present broad-band X-ray spectroscopy of the energetic components that make up the supernova remnant (SNR) Kesteven 75 using concurrent 2017 Aug 17-20 XMM-Newton and NuSTAR observations, during which the pulsar PSR J1846-0258 is found to be in the quiescent state. The young remnant hosts a bright pulsar wind nebula powered by the highly-energetic (Edot = 8.1E36 erg/s) isolated, rotation-powered pulsar, with a spin-down age of only P/2Pdot ~ 728 yr. Its inferred magnetic field (Bs = 4.9E13 G) is the largest known for these objects, and is likely responsible for intervals of flare and burst activity, suggesting a transition between/to a magnetar state. The pulsed emission from PSR J1846-0258 is well-characterized in the 2-50 keV range by a power-law model with photon index Gamma_PSR = 1.24+/-0.09 and a 2-10 keV unabsorbed flux of (2.3+/-0.4)E-12 erg/s/cm^2). We find no evidence for an additional non-thermal component above 10 keV in the current state, as would be typical for a magnetar. Compared to the Chandra pulsar spectrum, the intrinsic pulsed fraction is 71+/-16% in 2-10 keV band. A power-law spectrum for the PWN yields Gamma_PWN = 2.03+/-0.03 in the 1-55 keV band, with no evidence of curvature in this range, and a 2-10 keV unabsorbed flux (2.13+/-0.02)E-11 erg/s/cm^2. The NuSTAR data reveal evidence for a hard X-ray component dominating the SNR spectrum above 10 keV which we attribute to a dust-scattered PWN component. We model the dynamical and radiative evolution of the Kes 75 system to estimate the birth properties of the neutron star, the energetics of its progenitor, and properties of the PWN. This suggests that the progenitor of Kes 75 was originally in a binary system which transferred most its mass to a companion before exploding., Comment: 13 pages, 6 figures, 4 tables; Latex, aastex63 style. Submitted to the Astrophysical Journal

Using a 16.2 hr radio observation by the Australia Telescope Compact Array (ATCA) and archival Chandra data, we found $>5\sigma$ radio counterparts to 4 known and 3 new X-ray sources within the half-light radius ($r_\mathrm{h}$) of the Galactic globular cluster NGC 6397. The previously suggested millisecond pulsar (MSP) candidate, U18, is a steep-spectrum ($S_\nu \propto \nu^\alpha$; $\alpha=-2.0^{+0.4}_{-0.5}$) radio source with a 5.5 GHz flux density of $54.7\pm 4.3~\mathrm{\mu Jy}$. We argue that U18 is most likely a "hidden" MSP that is continuously hidden by plasma shocked at the collision between the winds from the pulsar and companion star. The nondetection of radio pulsations so far is probably the result of enhanced scattering in this shocked wind. On the other hand, we observed 5.5 GHz flux of the known MSP PSR J1740-5340 (U12) to decrease by a factor of $>2.8$ during epochs of 1.4 GHz eclipse, indicating that the radio flux is absorbed in its shocked wind. If U18 is indeed a pulsar whose pulsations are scattered, we note the contrast with U12's flux decrease in eclipse, which argues for two different eclipse mechanisms at the same radio frequency. In addition to U12 and U18, we also found radio associations for 5 other Chandra X-ray sources, four of which are likely background galaxies. The last, U97, which shows strong H$\alpha$ variability, is mysterious; it may be either a quiescent black hole low-mass X-ray binary, or something more unusual., Comment: Accepted for publication in Monthly Notices of the Royal Astronomical Society. 18 pages, 9 figures, 4 tables

We present a multi-wavelength study of the active galactic nucleus in the nearby ($D=14.1$ Mpc) low mass galaxy IC 750, which has circumnuclear 22 GHz water maser emission. The masers trace a nearly edge-on, warped disk $\sim$0.2 pc in diameter, coincident with the compact nuclear X-ray source which lies at the base of the $\sim$kpc-scale extended X-ray emission. The position-velocity structure of the maser emission indicates the central black hole (BH) has a mass less than $1.4 \times 10^5~M_\odot$. Keplerian rotation curves fitted to these data yield enclosed masses between $4.1 \times 10^4~M_\odot$ and $1.4 \times 10^5~M_\odot$, with a mode of $7.2 \times 10^4~M_\odot$. Fitting the optical spectrum, we measure a nuclear stellar velocity dispersion $\sigma_* = 110.7^{+12.1}_{-13.4}$~{\rm km~s}$^{-1}.$ From near-infrared photometry, we fit a bulge mass of $(7.3 \pm 2.7) \times 10^8~M_\odot$ and a stellar mass of $1.4 \times 10^{10}~M_\odot$. The mass upper limit of the intermediate mass black hole in IC 750 falls roughly two orders of magnitude below the $M_{\rm BH}-\sigma_*$ relation and roughly one order of magnitude below the $M_{\rm BH}-M_{\rm Bulge}$ and $M_{\rm BH}-M_*$ relations -- larger than the relations' intrinsic scatters of (0.58 $\pm$ 0.09) dex, 0.69 dex, and (0.65 $\pm$ 0.09) dex, respectively. These offsets could be due to larger scatter at the low mass end of these relations. Alternatively, black hole growth is intrinsically inefficient in galaxies with low bulge and/or stellar masses, which causes the black holes to be under-massive relative to their hosts, as predicted by some galaxy evolution simulations., Comment: Accepted for publication in ApJ

We present 150 MHz, 1.4 GHz, and 3 GHz radio imaging (LoTSS, FIRST and VLASS) and spatially resolved ionized gas characteristics (SDSS IV-MaNGA) for 140 local ($z, 23 pages, 14 figures. Accepted for publication in The Astrophysical Journal

One way an Active Galactic Nucleus (AGN) influences the evolution of their host galaxy is by generating a large-scale (kpc-scale) outflow. The content, energetics, and impact of such outflows depend on the properties of both the AGN and host galaxy, and understanding the relationship between them requires measuring the properties of all three. In this paper, we do so by analyzing recent radio and optical integral field unit (IFU) spectroscopic observations of MaNGA 1-166919. Our results indicate that the bi-conical outflow in this galaxy is powered by a low-luminosity, low-Eddington ratio AGN ejecting material that drives ~100-200 km/s shocks into the surrounding interstellar medium (ISM) -- producing the hot, ionized gas and relativistic particles associated with the observed outflow. The energetics of the relativistic and ionized gas material produced at this shock are comparable, and both the mass outflow and kinetic power of the ionized gas in this outflow are higher than other AGN with similar bolometric luminosities. Lastly, while the host galaxy's total star formation rate is comparable to that of other star-forming galaxies with a similar stellar mass, there is evidence that the outflow both suppresses and enhances star formation in its immediate surroundings., 29 pages, 28 figures, 11 tables, accepted by The Astrophysical Journal for publication

We present optical, UV and X-ray monitoring of the short orbital period black hole X-ray binary candidate Swift J1753.5-0127, focusing on the final stages of its 12$-$year long outburst that started in 2005. From September 2016 onward, the source started to fade and within three months, the optical flux almost reached the quiescent level. Soon after that, using a new proposed rebrightening classification method we recorded a mini-outburst and a reflare in the optical light curves, peaking in February (V$\rm\sim$17.0) and May (V$\rm\sim$17.9) 2017, respectively. Remarkably, the mini-outburst has a peak flux consistent with the extrapolation of the slow decay before the fading phase preceding it. The following reflare was fainter and shorter. We found from optical colors that the temperature of the outer disk was $\sim 11$,000 K when the source started to fade rapidly. According to the disk instability model, this is close to the critical temperature when a cooling wave is expected to form in the disk, shutting down the outburst. The optical color could be a useful tool to predict decay rates in some X-ray transients. We notice that all X-ray binaries that show mini-outbursts following a main outburst are short orbital period systems ($, Comment: 12 pages, 4 figures, accepted for publication in ApJ

A new class of quiescent galaxies harboring possible AGN-driven winds has been discovered using spatially resolved optical spectroscopy from the ongoing SDSS-IV MaNGA survey. These galaxies, termed "red geysers", constitute $5-10\%$ of the local quiescent population and are characterized by narrow bisymmetric patterns in ionized gas emission features. Cheung et al. argued that these galaxies host large-scale AGN-driven winds that may play a role in suppressing star formation at late times. In this work, we test the hypothesis that AGN activity is ultimately responsible for the red geyser phenomenon. We compare the nuclear radio activity of the red geysers to a matched control sample with similar stellar mass, redshift, rest frame $NUV-r$ color, axis ratio and presence of ionized gas. We have used the 1.4 GHz radio continuum data from VLA FIRST survey to stack the radio flux from the red geyser and control samples. In addition to a 3 times higher FIRST detection rate, we find that red geysers have a 5$\sigma$ higher level of average radio flux than control galaxies. After restricting to rest-frame $NUV-r$ color $>$ 5 and checking mid-IR WISE photometry, we rule out star formation contamination and conclude that red geysers are associated with more active AGN. Red geysers and a possibly-related class with disturbed H$\alpha$ emission account for 40\% of all radio-detected red galaxies with $\rm log~(M_\star/M_\odot) < 11$. Our results support a picture in which episodic AGN activity drives large-scale-relatively weak ionized winds that may provide a feedback mechanism for many early-type galaxies., Comment: 15 pages, 10 figures, accepted for publication in the Astrophysical journal

We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and high signal-to-noise ratio in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially-resolved spectroscopy for thousands of nearby galaxies (median redshift of z = 0.03). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is mapping the galaxy, quasar, and neutral gas distributions between redshifts z = 0.6 and 3.5 to constrain cosmology using baryon acoustic oscillations, redshift space distortions, and the shape of the power spectrum. Within eBOSS, we are conducting two major subprograms: the SPectroscopic IDentification of eROSITA Sources (SPIDERS), investigating X-ray AGN and galaxies in X-ray clusters, and the Time Domain Spectroscopic Survey (TDSS), obtaining spectra of variable sources. All programs use the 2.5-meter Sloan Foundation Telescope at Apache Point Observatory; observations there began in Summer 2014. APOGEE-2 also operates a second near-infrared spectrograph at the 2.5-meter du Pont Telescope at Las Campanas Observatory, with observations beginning in early 2017. Observations at both facilities are scheduled to continue through 2020. In keeping with previous SDSS policy, SDSS-IV provides regularly scheduled public data releases; the first one, Data Release 13, was made available in July 2016., Published in Astronomical Journal

We present a measurement of the proper motion of the presumed pulsar in the evolved composite supernova remnant (SNR) MSH 15-56 whose pulsar wind nebula (PWN) has been disrupted by the supernova (SN) reverse shock. Using Chandra X-ray observations acquired over a baseline of 15 years, we measure a pulsar velocity of 720 (+290/-215) km/s and a direction of motion of 14 +/- 22 degrees west of south. We use this measurement to constrain a hydrodynamical model for the evolution of this system and find that its morphology is well-described by an SNR expanding in an ambient density gradient that increases from east to west. The effect of the density gradient and the pulsar's motion is an asymmetric interaction between the SN reverse shock and the PWN that displaces the bulk of the PWN material away from the pulsar, towards the northeast. The simulation is consistent with an SNR age of 11,000 years, an SN ejecta mass of 10 solar masses, and an average surrounding density of 0.4 cm^-3. However, a combination of a higher SN ejecta mass and ambient density can produce a similar SNR morphology at a later age., Comment: Accepted to ApJ

Since pulsar wind nebulae (PWNe) are the product of the interaction between the magnetized, highly relativistic particle outflow powered by a neutron star’s rotational energy and its surroundings, their emission is sensitive to the properties of the central neutron star, its pulsar wind, and surroundings. Therefore, a PWN’s broadband spectral energy distribution (SED) can be used to determine the physical characteristics of all the components of this system—including quantities difficult if not impossible to measure using other means. This is best done by fitting the observed SED of a PWN with a model for both the radiative and dynamical emission of the system. In this chapter, I will describe the physics behind the single-zone (“0D”) models most often used to interpret the properties of PWNe, discuss their advantages and shortcomings, as well as speculate on the future of this field.

The candidate black hole X-ray binary Swift J1753.5-0127 faded to quiescence in 2016 November, after a prolonged outburst that was discovered in 2005. Nearly three months later the system displayed renewed activity that lasted through 2017 July. Here, we present radio and X-ray monitoring over ~3 months of the renewed activity to study the coupling between the jet and the inner regions of the disk/jet system. Our observations cover low X-ray luminosities that have not historically been well-sampled (Lx~2e33 - 1e36 erg/s; 1-10 keV), including time periods when the system was both brightening and fading. At these low luminosities Swift J1753.5-0127 occupies a parameter space in the radio/X-ray luminosity plane that is comparable to "canonical" systems (e.g., GX 339-4), regardless of whether the system was brightening or fading, even though during its >11-year outburst Swift J1753.5-0127 emitted less radio emission from its jet than expected. We discuss implications for the existence of a single radio/X-ray luminosity correlation for black hole X-ray binaries at the lowest luminosities (Lx < 1e35 erg/s), and we compare to supermassive black holes. Our campaign includes the lowest luminosity quasi-simultaneous radio/X-ray detection to date for a black hole X-ray binary during its rise out of quiescence, thanks to early notification from optical monitoring combined with fast responses from sensitive multiwavelength facilities., 11 pages, 3 figures, 1 table. Accepted for publication in ApJ

By studying composite supernova remnants (SNRs), remnants which contain a pulsar wind nebula (PWN), it is possible to estimate physical properties of the progenitor explosion, central neutron star, and its pulsar wind that are difficult to measure directly. This is best done by fitting the dynamical and broadband spectral properties of a PWN with an evolutionary model for a PWN inside an SNR. We apply such a model to the composite SNR Kes 75, whose associated pulsar PSR J1846-0258 is thought to have an extremely strong surface magnetic field. If ∼3 M⊙ of mass was ejected in the supernova, our model suggests a normal or slightly subenergetic supernova in a low density environment. Additionally, for the measured pre-outburst braking index of p = 2.65, our model prefers an age of ∼430 years and an initial spin period P0 ∼ 0.2 s. Lastly, the magnetization of the pulsar wind and energy spectrum of particles injected at the termination shock are similar to those observed from other PWNe powered by less magnetized neutron stars. While further study is needed to verify these results, they are nominally inconsistent with strong neutron star magnetic fields resulting from very fast initial rotation. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report on the analysis of two deep XMM-Newton observations of the magnetar Swift J1834.9-0846 and its surrounding extended emission taken in March 2014 and October 2014, 2.5 and 3.1 years after the source went into outburst. The magnetar is only weakly detected in the first observation with an absorption corrected flux $F_{\rm 0.5-10 keV}\approx4\times10^{-14}$ erg s$^{-1}$ cm$^{-2}$, and a $3\sigma$ upper limit during the second observation of about $3\times10^{-14}$ erg s$^{-1}$ cm$^{-2}$. This flux level is more than 3 orders of magnitude lower than the flux measured at the outburst onset on September 2011. The extended emission, centered at the magnetar position and elongated towards the south-west, is clearly seen in both observations; it is best fit by a highly absorbed power-law (PL), with a hydrogen column density of $N_{\rm H}=8.0\times10^{22}$ cm$^{-2}$ and PL photon index $\Gamma=2.2\pm0.2$. Its flux is constant between the two observations at $F_{\rm 0.5-10 keV}=1.3\times10^{-12}$ erg s$^{-1}$ cm$^{-2}$. We find no statistically significant changes in the spectral shape or the flux of this extended emission over a period of 9 years from 2005 to 2014. These new results strongly support the extended emission nature as a wind nebula and firmly establish Swift J1834.9-0846 as the first magnetar to show a surrounding wind nebula. Further, our results imply that such nebulae are no longer exclusive to rotation-powered pulsars and narrow the gap between these two sub-populations of isolated neutron stars. The size and spectrum of the nebula are compatible with those of pulsar-wind nebulae but its radiative efficiency $\eta_{\rm X}=L_{\rm X}/\dot{E}\approx0.1$ is markedly high, possibly pointing to an additional wind component in Swift J1834.9-0846., Comment: 12 Pages, 7 Figures, accpeted for publication in ApJ

The nature of warm, ionized gas outside of galaxies may illuminate several key galaxy evolutionary processes. A serendipitous observation by the MaNGA survey has revealed a large, asymmetric H$\alpha$ complex with no optical counterpart that extends ≈8″ (≈6.3 kpc) beyond the effective radius of a dusty, starbursting galaxy. This H$\alpha$ extension is approximately three times the effective radius of the host galaxy and displays a tail-like morphology. We analyze its gas-phase metallicities, gaseous kinematics, and emission-line ratios and discuss whether this H$\alpha$ extension could be diffuse ionized gas, a gas accretion event, or something else. We find that this warm, ionized gas structure is most consistent with gas accretion through recycled wind material, which could be an important process that regulates the low-mass end of the galaxy stellar mass function., Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. SDSS-IV is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration. D.B. is supported by grant RSCF-14-22-00041. A.W. acknowledges support from a Leverhulme Early Career Fellowship. J.H.K. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) under grant number AYA2013-41243-P and thanks the Astrophysics Research Institute of Liverpool John Moores University for their hospitality, and the Spanish Ministry of Education, Culture and Sports for financial support of his visit there, through grant number PR2015-00512.

Quiescent galaxies with little or no ongoing star formation dominate the galaxy population above $M_{*}\sim 2 \times 10^{10}~M_{\odot}$, where their numbers have increased by a factor of $\sim25$ since $z\sim2$. Once star formation is initially shut down, perhaps during the quasar phase of rapid accretion onto a supermassive black hole, an unknown mechanism must remove or heat subsequently accreted gas from stellar mass loss or mergers that would otherwise cool to form stars. Energy output from a black hole accreting at a low rate has been proposed, but observational evidence for this in the form of expanding hot gas shells is indirect and limited to radio galaxies at the centers of clusters, which are too rare to explain the vast majority of the quiescent population. Here we report bisymmetric emission features co-aligned with strong ionized gas velocity gradients from which we infer the presence of centrally-driven winds in typical quiescent galaxies that host low-luminosity active nuclei. These galaxies are surprisingly common, accounting for as much as $10\%$ of the population at $M_* \sim 2 \times 10^{10}~ M_{\odot}$. In a prototypical example, we calculate that the energy input from the galaxy's low-level active nucleus is capable of driving the observed wind, which contains sufficient mechanical energy to heat ambient, cooler gas (also detected) and thereby suppress star formation., To be published in Nature on May 26th, 2016

The origin of the high-frequency radio emission detected from several magnetars is poorly understood. In this paper, we report the ~40 GHz properties of SGR J1745-29 as measured using Jansky Very Large Array (JVLA) and Robert C. Byrd Green Bank Telescope (GBT) observations between 2013 October 26 and 2014 May 31. Our analysis of a Q-band (45 GHz) GBT observation on 2014 April 10 resulted in the earliest detection of pulsed radio emission at high frequencies (>20 GHz); we found that the average pulse has a singly peaked profile with width ~75 ms (~2% of the 3.764 s pulse period) and an average pulsed flux density of ~100 mJy. We also detected very bright, short (, 9 pages, 4 figure, 2 tables, published in The Astrophysical Journal

We present an XMM-Newton observation of the long-overlooked radio source G350.1-0.3. The X-ray spectrum of G350.1-0.3 can be fit by a shocked plasma with two components: a high-temperature (1.5 keV) region with a low ionization time scale and enhanced abundances, plus a cooler (0.36 keV) component in ionization equilibrium and with solar abundances. The X-ray spectrum and the presence of non-thermal, polarized, radio emission together demonstrate that G350.1-0.3 is a young, luminous supernova remnant (SNR), for which archival HI and 12-CO data indicate a distance of 4.5 kpc. The diameter of the source then implies an age of only ~900 years. The SNR's distorted appearance, small size and the presence of 12-CO emission along the SNR's eastern edge all indicate that the source is interacting with a complicated distribution of dense ambient material. An unresolved X-ray source, XMMU J172054.5-372652, is detected a few arcminutes west of the brightest SNR emission. The thermal X-ray spectrum and lack of any multi-wavelength counterpart suggest that this source is a neutron star associated with G350.1-0.3, most likely a "central compact object", as seen coincident with other young SNRs such as Cassiopeia A., 6 pages, uses emulateapj. One B/W figure, one color figure. Minor text changes and update to Fig 2 following referee's report. ApJ Letters, in press

We present new observational results obtained for the Galactic non-thermal radio source G328.4+0.2 to determine both if this source is a pulsar wind nebula or supernova remnant, and in either case, the physical properties of this source. Using X-ray data obtained by XMM, we confirm that the X-ray emission from this source is heavily absorbed and has a spectrum best fit by a power law model of photon index=2 with no evidence for a thermal component, the X-ray emission from G328.4+0.2 comes from a region significantly smaller than the radio emission, and that the X-ray and radio emission are significantly offset from each other. We also present the results of a new high resolution (7 arcseconds) 1.4 GHz image of G328.4+0.2 obtained using the Australia Telescope Compact Array, and a deep search for radio pulsations using the Parkes Radio Telescope. We find that the radio emission has a flat spectrum, though some areas along the eastern edge of G328.4+0.2 have a steeper radio spectral index of ~-0.3. Additionally, we obtain a luminosity limit of the central pulsar of L_{1400} < 30 mJy kpc^2, assuming a distance of 17 kpc. In light of these observational results, we test if G328.4+0.2 is a pulsar wind nebula (PWN) or a large PWN inside a supernova remnant (SNR) using a simple hydrodynamic model for the evolution of a PWN inside a SNR. As a result of this analysis, we conclude that G328.4+0.2 is a young (< 10000 years old) pulsar wind nebula formed by a low magnetic field (10^51 ergs), low ejecta mass (M < 5 Solar Masses) supernova explosion which occurred in a low density (n~0.03 cm^{-3}) environment., 27 pages, 11 figures, accepted for publication in The Astrophysical Journal

On 27 December 2004, just the third giant flare was observed from a magnetar, in this case SGR 1806-20. This giant flare was the most energetic of the three, and analysis of a Very Large Array observation of SGR 1806-20 after the giant flare revealed the existence of a new, bright, transient radio source at its position. Follow-up radio observations of this source determined that initially, this source underwent a mildly relativistic one-sided expansion which ceased at the same time as a temporary rebrightening of the radio source. These observational results imply that the radio emission is powered by ∼1024 g of baryonic material which was ejected off the surface on the neutron star during the giant flare.

Neutron stars lose the bulk of their rotational energy in the form of a pulsar wind: an ultra-relativistic outflow of predominantly electrons and positrons. This pulsar wind significantly impacts the environment and possible binary companion of the neutron star, and studying the resultant pulsar wind nebulae is critical for understanding the formation of neutron stars and millisecond pulsars, the physics of the neutron star magnetosphere, the acceleration of leptons up to PeV energies, and how these particles impact the interstellar medium. With the SKA1 and the SKA2, it could be possible to study literally hundreds of PWNe in detail, critical for understanding the many open questions in the topics listed above., Comments: 10 pages, 3 figures, to be published in: "Advancing Astrophysics with the Square Kilometre Array", Proceedings of Science, PoS(AASKA14)

On 2004 Dec. 27, the soft gamma repeater (SGR) 1806-20 emitted the brightest giant flare (GF) ever detected from an SGR, with an (isotropic) energy release $\sim 100$ times greater than the only two other known SGR GFs. It was followed by a very bright, fading radio afterglow. Extensive follow-up radio observations provided a wealth of information with unprecedented astrometric precision, revealing the temporal evolution of the source size, along with densely sampled light curves and spectra. Here we expand on our previous work on this source, by explaining these observations within one self-consistent dynamical model. In this scenario, the early radio emission is due to the outflow ejected during the GF energizing a thin shell surrounding a pre-existing cavity, where the observed steep temporal decay of the radio emission seen beginning on day 9 is attributed to the adiabatic cooling of the shocked shell. The shocked ejecta and external shell move outward together, driving a forward shock into the ambient medium, and are eventually decelerated by a reverse shock. As we show in Gelfand et al. (2005), the radio emission from the shocked external medium naturally peaks when significant deceleration occurs, and then decays relatively slowly. The dynamical modeling of the collision between the ejecta and the external shell together with the observed evolution of the source size (which is nicely reproduced in our model) suggest that most of the energy in the outflow was in mildly relativistic material, with an initial expansion velocity $v/c \lesssim 0.7d_{15}$, for a distance of $15d_{15}$ kpc to SGR 1806-20. An initially highly relativistic outflow would not have produced a long coasting phase at a mildly relativistic expansion velocity, as was observed., 15 pages, 2 figures, clearer and more elaborate version; ApJ, in press

The extraordinary giant flare (GF) of 2004 December 27 from the soft gamma repeater (SGR) 1806-20 was followed by a bright radio afterglow. We present an analysis of VLA observations of this radio afterglow from SGR 1806-20, consisting of previously reported 8.5 GHz data covering days 7 to 20 after the GF, plus new observations at 8.5 and 22 GHz from day 24 to 81. We detect motion in the flux centroid of the afterglow, at an average velocity of 0.26 +/- 0.03 c (assuming a distance of 15 kpc) at a position angle of -45 degrees. This motion, in combination with the growth and polarization measurements, suggests an asymmetric outflow, mainly from one side of the magnetar. We find a deceleration in the expansion, from ~9 mas/day to, 5 pages, 3 figures, as accepted to ApJ Letters

We present the discovery of non-thermal radio and X-ray emission positionally coincident with the TeV $\gamma$-ray source HESS J1813--178. We demonstrate that the non-thermal radio emission is due to a young shell-type supernova remnant (SNR) G12.8--0.0, and constrain its distance to be greater than 4 kpc. The X-ray emission is primarily non-thermal and is consistent with either an SNR shell or unidentified pulsar/pulsar wind nebula origin; pulsed emission is not detected in archival ASCA data. A simple synchrotron+inverse Compton model for the broadband emission assuming that all of the emission arises from the SNR shell implies maximum energies of $(30-450)(B/10 microG)^{-0.5}$ TeV. Further observations are needed to confirm that the broadband emission has a common origin and better constrain the X-ray spectrum., Comment: Accepted to ApJ Letters; 5 pages, Figures 1 and 3 are in color. Small changes from original version

We compare a deep (37 ks) Chandra ACIS-S image of the M31 bulge to Local Group Survey narrow-band optical data and Very Large Array (VLA) radio data of the same region. Our precisely registered images reveal two new optical shells with X-ray counterparts. These shells have sizes, [S II]/H-alpha flux ratios, and X-ray spectral properties typical of supernova remnants (SNRs) with ages of 9$^{+3}_{-4}$ and 17$^{+6}_{-9}$ kyr. Analysis of complementary VLA data reveals the radio counterparts, further confirming that they are SNRs. We discuss and compare the properties and morphologies of these SNRs at the different wavelengths., Comment: 18 pages, 5 figures, accepted for publication in ApJ

While theoretical dust condensation models predict that most refractory elements produced in core-collapse supernovae (SNe) efficiently condense into dust, a large quantity of dust has so far only been observed in SN 1987A. We present the analysis of Spitzer Space Telescope, Herschel Space Observatory, Stratospheric Observatory for Infrared Astronomy (SOFIA), and AKARI observations of the infrared (IR) shell surrounding the pulsar wind nebula in the supernova remnant G54.1+0.3. We attribute a distinctive spectral feature at 21 $\mu$m to a magnesium silicate grain species that has been invoked in modeling the ejecta-condensed dust in Cas A, which exhibits the same spectral signature. If this species is responsible for producing the observed spectral feature and accounts for a significant fraction of the observed IR continuum, we find that it would be the dominant constituent of the dust in G54.1+0.3, with possible secondary contributions from other compositions, such as carbon, silicate, or alumina grains. The smallest mass of SN-formed dust required by our models is 1.1 $\pm$ 0.8 $\rm M_{\odot}$. We discuss how these results may be affected by varying dust grain properties and self-consistent grain heating models. The spatial distribution of the dust mass and temperature in G54.1+0.3 confirms the scenario in which the SN-formed dust has not yet been processed by the SN reverse shock and is being heated by stars belonging to a cluster in which the SN progenitor exploded. The dust mass and composition suggest a progenitor mass of 16$-$27 $\rm M_{\odot}$ and imply a high dust condensation efficiency, similar to that found for Cas A and SN 1987A. The study provides another example of significant dust formation in a Type IIP SN and sheds light on the properties of pristine SN-condensed dust., Comment: 16 pages, 3 tables, 11 figures, accepted for publication in ApJ

MaNGA (Mapping Nearby Galaxies at Apache Point Observatory) is a SDSS-IV survey that will obtain spatially resolved spectroscopy from 3600 \AA\ to 10300 \AA\ for a representative sample of over 10000 nearby galaxies. In this paper we present the analysis of nebular emission line properties in 14 galaxies obtained with P-MaNGA, a prototype of the MaNGA instrument. Using spatially resolved diagnostic diagrams we find extended star formation in galaxies that are centrally dominated by Seyfert/LINER-like emission, which illustrates that galaxy characterisations based on single fibre spectra are necessarily incomplete. We observe extended LINER-like emission (up to $\rm 1 R_{e}$) in three galaxies. We make use of the $\rm EW(H \alpha)$ to argue that the observed emission is consistent with ionisation from hot evolved stars. We derive stellar population indices and demonstrate a clear correlation between $\rm D_n(4000)$ and $\rm EW(H \delta_A)$ and the position in the ionisation diagnostic diagram: resolved galactic regions which are ionised by a Seyfert/LINER-like radiation field are also devoid of recent star formation and host older and/or more metal rich stellar populations. We also detect extraplanar LINER-like emission in two highly inclined galaxies, and identify it with diffuse ionised gas. We investigate spatially resolved metallicities and find a positive correlation between metallicity and star formation rate (SFR) surface density. We study the relation between N/O vs O/H on resolved scales. We find that, at given N/O, regions within individual galaxies are spread towards lower metallicities, deviating from the sequence defined by galactic central regions as traced by Sloan $3''$ fibre spectra. We suggest that the observed dispersion can be a tracer for gas flows in galaxies: infalls of pristine gas and/or the effect of a galactic fountain., Comment: 37 pages, 28 figures, accepted to MNRAS after minor revision, update references

This work reports on the detection of $\gamma$-ray emission coincident with the supernova remnant (SNR) SNR G5.7-0.1 using data collected by the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope. The SNR is believed to be interacting with molecular clouds, based on 1720 MHz hydroxyl (OH) maser emission observations in its direction. This interaction is expected to provide targets for the production of $\gamma$-ray emission from $\pi^0$-decay. A $\gamma$-ray source was observed in the direction of SNR G5.7-0.1, positioned nearby the bright $\gamma$-ray source SNR W28. We model the emission from radio to $\gamma$-ray energies using a one-zone model. Following consideration of both $\pi^0$-decay and leptonically dominated emission scenarios for the MeV-TeV source, we conclude that a considerable component of the $\gamma$-ray emission must originate from the $\pi^0$-decay channel. Finally, constraints were placed on the reported ambiguity of the SNR distance through X-ray column density measurements made using XMM-Newton observations. We conclude SNR G5.7-0.1 is a significant $\gamma$-ray source positioned at a distance of $\sim 3$ kpc with luminosity in the 0.1--100 GeV range of $L_{\gamma} \approx 7.4 \times 10^{34}$ erg/s., Comment: 8 pages, 5 figures, 1 table, Accepted for publication in ApJ

MSH 11-62 (G291.1-0.9) is a composite supernova remnant for which radio and X-ray observations have identified the remnant shell as well as its central pulsar wind nebula. The observations suggest a relatively young system expanding into a low density region. Here we present a study of MSH 11-62 using observations with the Chandra, XMM-Newton, and Fermi observatories, along with radio observations from the Australia Telescope Compact Array (ATCA). We identify a compact X-ray source that appears to be the putative pulsar that powers the nebula, and show that the X-ray spectrum of the nebula bears the signature of synchrotron losses as particles diffuse into the outer nebula. Using data from the Fermi LAT, we identify gamma-ray emission originating from MSH 11-62. With density constraints from the new X-ray measurements of the remnant, we model the evolution of the composite system in order to constrain the properties of the underlying pulsar and the origin of the gamma-ray emission., Comment: 12 Pages, 12 figures. Accepted for publication in the Astrophysical Journal

We present a new Chandra observation of supernova remnant (SNR) G350.1-0.3. The high resolution X-ray data reveal previously unresolved filamentary structures and allow us to perform detailed spectroscopy in the diffuse regions of this SNR. Spectral analysis demonstrates that the region of brightest emission is dominated by hot, metal-rich ejecta while the ambient material along the perimeter of the ejecta region and throughout the remnant's western half is mostly low-temperature, shocked interstellar/circumstellar medium (ISM/CSM) with solar-type composition. The data reveal that the emission extends far to the west of the ejecta region and imply a lower limit of 6.6 pc on the diameter of the source (at a distance of 4.5 kpc). We show that G350.1-0.3 is likely in the free expansion (ejecta-dominated) stage and calculate an age of 600-1200 years. The derived relationship between the shock velocity and the electron/proton temperature ratio is found to be entirely consistent with that of other SNRs. We perform spectral fits on the X-ray source XMMU J172054.5-372652, a candidate central compact object (CCO), and find that its spectral properties fall within the typical range of other CCOs. We also present archival 24 um data of G350.1-0.3 taken with the Spitzer Space Telescope during the MIPSGAL galactic survey and find that the infrared and X-ray morphologies are well-correlated. These results help to explain this remnant's peculiar asymmetries and shed new light on its dynamics and evolution.

Recent X-ray observations have proved to be very effective in detecting previously unknown supernova remnant shells around pulsar wind nebulae (PWNe), and in these cases the characteristics of the shell provide further clues on the evolutionary stage of the embedded PWN. However, it is not clear why some PWNe are still "naked". We carried out an X-ray observational campaign targeted at the PWN G54.1+0.3, the "close cousin" of the Crab, with the aim to detect the associated SNR shell. We analyzed an XMM-Newton and Suzaku observations of G54.1+0.3 and we model out the contribution of dust scattering halo. We detected an intrinsic faint diffuse X-ray emission surrounding a hard spectrum, which can be modeled either with a power-law (gamma= 2.9) or with a thermal plasma model (kT=2.0 keV.). If the shell is thermal, we derive an explosion energy E=0.5-1.6x10^51 erg, a pre-shock ISM density of 0.2 cm^-3 and an age of about 2000 yr. Using these results in the MHD model of PWN-SNR evolution, we obtain an excellent agreement between the predicted and observed location of the shell and PWN shock., Accepted for publication in A&A, 8 pages, 5 figures, full-res version at http://www.astropa.inaf.it/Library/OAPA_preprints/h14298.pdf

Using archival SDSS multi-epoch imaging data (Stripe 82), we have searched for the tidal disruption of stars by super-massive black holes in non-active galaxies. Two candidate tidal disruption events (TDEs) are identified. They have optical black-body temperatures 2 10^4 K and observed peak luminosities M_g=-18.3 and -20.4; their cooling rates are very low, qualitatively consistent with expectations for tidal disruption flares. Their properties are examined using i) SDSS imaging to compare them to other flares observed in the search, ii) UV emission measured by GALEX and iii) spectra of the hosts and of one of the flares. Our pipeline excludes optically identifiable AGN hosts, and our variability monitoring over 9 years provides strong evidence that these are not flares in hidden AGNs. The spectra and color evolution of the flares are unlike any SN observed to date, their strong late-time UV emission is particularly distinctive, and they are nuclear at high resolution, arguing against their being first cases of a previously-unobserved class of SNe or more extreme examples of known SN types. Taken together, the observed properties are difficult to reconcile with a SN or AGN-flare explanation, although an entirely new process specific to the inner few-hundred parsecs of non-active galaxies cannot be excluded. Our observed rate and method show the feasibility of obtaining a candidate TDE sample of hundreds of events and O(1) purity, using geometric resolution and host and flare color alone. A by-product of this work is quantification of the power-spectrum of extreme flares in AGNs., Comment: Accepted for publication in ApJ; 25 pages, 21 figures, 5 tables. The rate estimate of the first version has been moved to a separate, forthcoming paper

A pulsar wind nebula inside a supernova remnant provides a unique insight into the properties of the central neutron star, the relativistic wind powered by its loss of rotational energy, its progenitor supernova, and the surrounding environment. In this paper, we present a new semi-analytic model for the evolution of such a pulsar wind nebula which couples the dynamical and radiative evolution of the pulsar wind nebulae, traces the evolution of the pulsar wind nebulae throughout the lifetime of the supernova remnant produced by the progenitor explosion, and predicts both the dynamical and radiative properties of the pulsar wind nebula during this period. We also discuss the expected evolution for a particular set of these parameters, and show it reproduces many puzzling features of known young and old pulsar wind nebulae. The model also predicts spectral features during different phases of its evolution detectable with new radio and gamma-ray observing facilities. Finally, this model has implications for determining if pulsar wind nebulae can explain the recent measurements of the cosmic ray positron fraction by PAMELA and the cosmic ray lepton spectrum by ATIC and HESS., Comment: To be submitted to the Astrophysical Journal. Figures are included as GIF files, and a version containing the high-resolution figures is available http://cosmo.nyu.edu/~jg168/pwn/ms.pdf

Magnetars, neutron stars whose dipole component of their surface magnetic field has a strength of 1014 – 1015 G, are luminous sources in the X‐ray and γ‐ray regimes, but until recently were undetected at radio wavelengths. However, new observations have discovered several radio pulsars with magnetic field strength similar to that of magnetars, pulsed radio emission from transient Anomalous X‐ray Pulsar XTE J1810‐197, and continuum radio emission from Soft γ‐ray Repeater SGR 1806‐20 believed to be the result of the giant γ‐ray flare observed from this source of 27 December 2004. While the nature of the radio emission from these sources has yet to be determined, studying this emission is important in the determining the emission mechanism of the magnetars, the difference between magnetars and “normal” radio pulsars, and the physical mechanism behind magnetar giant flares.

We present X-ray, infrared and radio observations of the field centered on X-ray source 1E 1547.0-5408 in the Galactic Plane. A new Chandra observation of this source shows it is unresolved at arc-second resolution, and a new XMM observation shows that its X-ray spectrum is best described by an absorbed power-law and blackbody model. A comparison of the X-ray flux observed from this source between 1980 and 2006 reveals that its absorbed 0.5-10 keV X-ray flux decreased from ~2x10^-12 ergs cm-2 s-1 to ~3x10^-13 ergs cm-2 during this period. The most recent XMM observation allows us to put a 5 sigma confidence upper limit of 14% for the 0.5-10 keV peak-to-peak pulsed fraction. A near-infrared observation of this field shows a source with magnitude Ks = 15.9+/-0.2 near the position of 1E 1547.0-5408, but the implied X-ray to infrared flux ratio indicates the infrared emission is from an unrelated field source, allowing us to limit the IR magnitude of 1E 1547.0-5408 to >17.5. Archival radio observations reveal that 1E 1547.0-5408 sits at the center of a faint, small (4' diameter) radio shell, G327.24-0.13, which is possibly a previously unidentified supernova remnant. The X-ray properties of 1E 1547.0-5408 suggest that this source is a magnetar - a young neutron star whose X-ray emission is powered by the decay of its extremely strong magnetic field. The spatial coincidence between this source and G327.24-0.13 suggests that 1E 1547.0-5408 is associated with a young supernova remnant, supporting a neutron star interpretation. Additional observations are needed to confirm the nature of both 1E 1547.0-5408 and G327.24-0.13, and to determine if these sources are associated. If so, this pair will be an important addition to the small number of known associations between magnetars and supernova remnants., 11 pages, 5 figures, ApJ accepted