Pulsars in Globular Clusters with the SKA

Globular clusters are highly efficient radio pulsar factories. These pulsars can be used as precision probes of the clusters' structure, gas content, magnetic field, and formation history; some of them are also highly interesting in their own right because they probe exotic stellar evolution scenarios as well as the physics of dense matter, accretion, and gravity. Deep searches with SKA1-MID and SKA1-LOW will plausibly double to triple the known population. Such searches will only require one to a few tied-array beams, and can be done during early commissioning of the telescope - before an all-sky pulsar survey using hundreds to thousands of tied-array beams is feasible. With SKA2 it will be possible to observe most of the active radio pulsars within a large fraction of the Galactic globular clusters, an estimated population of 600 - 3700 observable pulsars (those beamed towards us). This rivals the total population of millisecond pulsars that can be found in the Galactic field; fully characterizing it will provide the best-possible physical laboratories as well as a rich dynamical history of the Galactic globular cluster system.Comment: 15 pages, 5 figures, to be published in: "Advancing Astrophysics with the Square Kilometre Array", Proceedings of Science, PoS(AASKA14)04

Detection of Bursts from FRB 121102 with the Effelsberg 100-m Radio Telescope at 5 GHz and the Role of Scintillation

FRB 121102, the only repeating fast radio burst (FRB) known to date, was discovered at 1.4 GHz and shortly after the discovery of its repeating nature, detected up to 2.4 GHz. Here we present three bursts detected with the 100-m Effelsberg radio telescope at 4.85 GHz. All three bursts exhibited frequency structure on broad and narrow frequency scales. Using an autocorrelation function analysis, we measured a characteristic bandwidth of the small-scale structure of 6.4$\pm$1.6 MHz, which is consistent with the diffractive scintillation bandwidth for this line of sight through the Galactic interstellar medium (ISM) predicted by the NE2001 model. These were the only detections in a campaign totaling 22 hours in 10 observing epochs spanning five months. The observed burst detection rate within this observation was inconsistent with a Poisson process with a constant average occurrence rate; three bursts arrived in the final 0.3 hr of a 2 hr observation on 2016 August 20. We therefore observed a change in the rate of detectable bursts during this observation, and we argue that boosting by diffractive interstellar scintillations may have played a role in the detectability. Understanding whether changes in the detection rate of bursts from FRB 121102 observed at other radio frequencies and epochs are also a product of propagation effects, such as scintillation boosting by the Galactic ISM or plasma lensing in the host galaxy, or an intrinsic property of the burst emission will require further observations.Comment: Accepted to ApJ. Minor typos correcte

The missing GeV {\gamma}-ray binary: Searching for HESS J0632+057 with Fermi-LAT

The very high energy (VHE; >100 GeV) source HESS J0632+057 has been recently confirmed as a \gamma-ray binary, a subclass of the high mass X-ray binary (HMXB) population, through the detection of an orbital period of 321 days. We performed a deep search for the emission of HESS J0632+057 in the GeV energy range using data from the Fermi Large Area Telescope (LAT). The analysis was challenging due to the source being located in close proximity to the bright \gamma-ray pulsar PSR J0633+0632 and lying in a crowded region of the Galactic plane where there is prominent diffuse emission. We formulated a Bayesian block algorithm adapted to work with weighted photon counts, in order to define the off-pulse phases of PSR J0633+0632. A detailed spectral-spatial model of a 5 deg circular region centred on the known location of HESS J0632+057 was generated to accurately model the LAT data. No significant emission from the location of HESS J0632+057 was detected in the 0.1-100 GeV energy range integrating over ~3.5 years of data; with a 95% flux upper limit of F_{0.1-100 GeV} < 3 x 10-8 ph cm-2 s-1. A search for emission over different phases of the orbit also yielded no significant detection. A search for source emission on shorter timescales (days--months) did not yield any significant detections. We also report the results of a search for radio pulsations using the 100-m Green Bank Telescope (GBT). No periodic signals or individual dispersed bursts of a likely astronomical origin were detected. We estimated the flux density limit of < 90/40 \mu Jy at 2/9 GHz. The LAT flux upper limits combined with the detection of HESS J0632+057 in the 136-400 TeV energy band by the MAGIC collaboration imply that the VHE spectrum must turn over at energies <136 GeV placing constraints on any theoretical models invoked to explain the \gamma-ray emission.Comment: 11 pages, 4 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society (MNRAS) Main Journa

Einstellungen und Selbstwirksamkeit von Lehrerinnen und Lehrern zur schulischen Inklusion in Deutschland - eine Analyse mit Daten des Nationalen Bildungspanels Deutschlands (NEPS)

In Deutschland wird der gemeinsame Unterricht von Schülerinnen und Schülern mit und ohne sonderpädagogischem Förderbedarf im Schulsystem stark ausgebaut. Als eine wichtige Voraussetzung für eine gelungene Umsetzung des gemeinsamen Unterrichts wird in der Forschung die Einstellungen der beteiligten Lehrerinnen und Lehrer zur Inklusion gesehen. Der vorliegende Bei- trag berichtet über die Selbstwirksamkeit und die allgemeine Einstellung zur Inklusion bei 130 Klassenlehrkräften in der der 2. Welle der Startkohorte 3 (6. Jahrgangsstufe) des Nationalen Bildungspanels (NEPS). Insgesamt haben die Regelschullehrkräfte eine positive Einstellung gegenüber der Inklusion, jedoch ist die Selbstwirksamkeit in Bezug auf Inklusion eher gering ausgeprägt. Die befragten Klassenlehrkräfte in Förderschulen trauen sich dagegen die Umsetzung des gemeinsamen Unterrichts eher zu. Gegenüber der Inklusion haben sie jedoch Bedenken und halten die Förderschule für den optimaleren Förderort für Schülerinnen und Schüler mit sonderpädagogischem Förderbedarf

A deep campaign to characterize the synchronous radio/X-ray mode switching of PSR B0943+10

We report on simultaneous X-ray and radio observations of the mode-switching pulsar PSR B0943+10 obtained with the XMM-Newton satellite and the LOFAR, LWA and Arecibo radio telescopes in November 2014. We confirm the synchronous X-ray/radio switching between a radio-bright (B) and a radio-quiet (Q) mode, in which the X-ray flux is a factor ~2.4 higher than in the B-mode. We discovered X-ray pulsations, with pulsed fraction of 38+/-5% (0.5-2 keV), during the B-mode, and confirm their presence in Q-mode, where the pulsed fraction increases with energy from ~20% up to ~65% at 2 keV. We found marginal evidence for an increase in the X-ray pulsed fraction during B-mode on a timescale of hours. The Q-mode X-ray spectrum requires a fit with a two-component model (either a power-law plus blackbody or the sum of two blackbodies), while the B-mode spectrum is well fit by a single blackbody (a single power-law is rejected). With a maximum likelihood analysis, we found that in Q-mode the pulsed emission has a thermal blackbody spectrum with temperature ~3.4x10^6 K and the unpulsed emission is a power-law with photon index ~2.5, while during B-mode both the pulsed and unpulsed emission can be fit by either a blackbody or a power law with similar values of temperature and photon index. A Chandra image shows no evidence for diffuse X-ray emission. These results support a scenario in which both unpulsed non-thermal emission, likely of magnetospheric origin, and pulsed thermal emission from a small polar cap (~1500 m^2) with a strong non-dipolar magnetic field (~10^{14} G), are present during both radio modes and vary in intensity in a correlated way. This is broadly consistent with the predictions of the partially screened gap model and does not necessarily imply global magnetospheric rearrangements to explain the mode switching.Comment: To be published on The Astrophysical Journa

Simultaneous X-ray, gamma-ray, and Radio Observations of the repeating Fast Radio Burst FRB 121102

We undertook coordinated campaigns with the Green Bank, Effelsberg, and Arecibo radio telescopes during Chandra X-ray Observatory and XMM-Newton observations of the repeating fast radio burst FRB 121102 to search for simultaneous radio and X-ray bursts. We find 12 radio bursts from FRB 121102 during 70 ks total of X-ray observations. We detect no X-ray photons at the times of radio bursts from FRB 121102 and further detect no X-ray bursts above the measured background at any time. We place a 5$\sigma$ upper limit of $3\times10^{-11}$ erg cm$^{-2}$ on the 0.5--10 keV fluence for X-ray bursts at the time of radio bursts for durations $<700$ ms, which corresponds to a burst energy of $4\times10^{45}$ erg at the measured distance of FRB 121102. We also place limits on the 0.5--10 keV fluence of $5\times10^{-10}$ erg cm$^{-2}$ and $1\times10^{-9}$ erg cm$^{-2}$ for bursts emitted at any time during the XMM-Newton and Chandra observations, respectively, assuming a typical X-ray burst duration of 5 ms. We analyze data from the Fermi Gamma-ray Space Telescope Gamma-ray Burst Monitor and place a 5$\sigma$ upper limit on the 10--100 keV fluence of $4\times10^{-9}$ erg cm$^{-2}$ ($5\times10^{47}$ erg at the distance of FRB 121102) for gamma-ray bursts at the time of radio bursts. We also present a deep search for a persistent X-ray source using all of the X-ray observations taken to date and place a 5$\sigma$ upper limit on the 0.5--10 keV flux of $4\times10^{-15}$ erg s$^{-1}$ cm$^{-2}$ ($3\times10^{41}$ erg~s$^{-1}$ at the distance of FRB 121102). We discuss these non-detections in the context of the host environment of FRB 121102 and of possible sources of fast radio bursts in general.Comment: 13 pages, 5 figures, published in Ap

The repeating Fast Radio Burst FRB 121102: Multi-wavelength observations and additional bursts

We report on radio and X-ray observations of the only known repeating Fast Radio Burst (FRB) source, FRB 121102. We have detected six additional radio bursts from this source: five with the Green Bank Telescope at 2 GHz, and one at 1.4 GHz at the Arecibo Observatory for a total of 17 bursts from this source. All have dispersion measures consistent with a single value ($\sim559$ pc cm$^{-3}$) that is three times the predicted maximum Galactic value. The 2-GHz bursts have highly variable spectra like those at 1.4 GHz, indicating that the frequency structure seen across the individual 1.4 and 2-GHz bandpasses is part of a wideband process. X-ray observations of the FRB 121102 field with the Swift and Chandra observatories show at least one possible counterpart; however, the probability of chance superposition is high. A radio imaging observation of the field with the Jansky Very Large Array at 1.6 GHz yields a 5$\sigma$ upper limit of 0.3 mJy on any point-source continuum emission. This upper limit, combined with archival WISE 22-$\mu$m and IPHAS H$\alpha$ surveys, rules out the presence of an intervening Galactic HII region. We update our estimate of the FRB detection rate in the PALFA survey to be 1.1$^{+3.7}_{-1.0} \times 10^4$ FRBs sky$^{-1}$ day$^{-1}$ (95% confidence) for peak flux density at 1.4 GHz above 300 mJy. We find that the intrinsic widths of the 12 FRB 121102 bursts from Arecibo are, on average, significantly longer than the intrinsic widths of the 13 single-component FRBs detected with the Parkes telescope.Comment: 18 pages, 5 figures. Accepted for publication in Ap

A Multi-telescope Campaign on FRB 121102: Implications for the FRB Population

We present results of the coordinated observing campaign that made the first subarcsecond localization of a Fast Radio Burst, FRB 121102. During this campaign, we made the first simultaneous detection of an FRB burst by multiple telescopes: the VLA at 3 GHz and the Arecibo Observatory at 1.4 GHz. Of the nine bursts detected by the Very Large Array at 3 GHz, four had simultaneous observing coverage at other observatories. We use multi-observatory constraints and modeling of bursts seen only at 3 GHz to confirm earlier results showing that burst spectra are not well modeled by a power law. We find that burst spectra are characterized by a ~500 MHz envelope and apparent radio energy as high as $10^{40}$ erg. We measure significant changes in the apparent dispersion between bursts that can be attributed to frequency-dependent profiles or some other intrinsic burst structure that adds a systematic error to the estimate of DM by up to 1%. We use FRB 121102 as a prototype of the FRB class to estimate a volumetric birth rate of FRB sources $R_{FRB} \approx 5x10^{-5}/N_r$ Mpc$^{-3}$ yr$^{-1}$, where $N_r$ is the number of bursts per source over its lifetime. This rate is broadly consistent with models of FRBs from young pulsars or magnetars born in superluminous supernovae or long gamma-ray bursts, if the typical FRB repeats on the order of thousands of times during its lifetime.Comment: 17 pages, 7 figures. Submitted to AAS Journal

The Full Spectrum Galactic Terrarium: MHz to TeV Observations of Various Critters

Multi-wavelength studies at radio, infrared, optical, X-ray, and TeV wavelengths have discovered probable counterparts to many Galactic sources of GeV emission detected by EGRET. These include pulsar wind nebulae, high mass X-ray binaries, and mixed morphology supernova remnants. Here we provide an overview of the observational properties of Galactic sources which emit across 19 orders of magnitude in energy. We also present new observations of several sources.Comment: 4 pages, 5 figures, Proceedings of the The 4th Heidelberg International Symposium on High Energy Gamma-Ray Astronomy, eds. Aharonian, Hofmann, Riege