SN 2007gr: a Normal Type Ic Supernova with a Mildly Relativistic Radio Jet?

A nearby type Ic supernova, SN 2007gr was observed with the EVN in two epochs 60 days apart (second observation also included the Green Bank Telescope). In both cases one of the EVN stations was the Westerbork Synthesis Radio Telescope (WSRT), which recorded the observational data not only in the VLBI mode, but also in its normal interferometric mode. Thus it provided an important reference observation. In the first epoch the fluxes measured by the VLBI network and the WSRT alone match well. However in the second epoch the peak brightness observed in the VLBI experiment is much lower than the total flux recorded by the WSRT. There could be multiple reasons for this discrepancy: a resolution effect, coherence losses in VLBI, or extended emission contaminating the WSRT measurement. With new WSRT observations we costrain the level of background emission and find that there is still a difference between the corrected total flux density and the VLBI peak brightness. If one assumes that this is dominated by resolution, this would correspond to an average apparent expansion speed of ~0.4c

High-z radio starbursts host obscured X-ray AGN

We use Virtual Observatory methods to investigate the association between radio and X-ray emission at high redshifts. Fifty-five of the 92 HDF(N) sources resolved by combining MERLIN+VLA data were detected by Chandra, of which 18 are hard enough and bright enough to be obscured AGN. The high-z population of microJy radio sources is dominated by starbursts an order of magnitude more active and more extended than any found at z<1 and at least a quarter of these simultaneously host highly X-ray-luminous obscured AGN.Comment: 4 pages, 2 figures, To appear in the proceedings of 'At the Edge of the Universe' (9-13 October 2006, Sintra, Portugal

AGN and starbursts at high redshift: High resolution EVN radio observations of the Hubble Deep Field

We present deep, wide-field European VLBI Network (EVN) 1.6 GHz observations of the Hubble Deep Field (HDF) region with a resolution of 0.025 arcseconds. Above the 210 microJy/beam (5sigma) detection level, the EVN clearly detects two radio sources in a field that encompasses the HDF and part of the Hubble Flanking Fields (HFF). The sources detected are: VLA J123644+621133 (a z=1.013, low-luminosity FR-I radio source located within the HDF itself) and VLA J123642+621331 (a dust enshrouded, optically faint, z=4.424 starburst system). A third radio source, J123646+621404, is detected at the 4sigma level. The VLBI detections of all three sources suggest that most of the radio emission of these particular sources (including the dusty starburst) is generated by an embedded AGN.Comment: 4 pages, 1 figure; Accepted by Astron. & Astrophys Letters ... See http://www.nfra.nl/~mag/hdf_evn.htm

Constraints on H_0 from the Central Velocity Dispersions of Lens Galaxies

We employ Schwarzschild's method of orbit modeling to constrain the mass profiles of the central lens galaxies in Q0957+561 and PG 1115+080. We combine the measured central projected stellar velocity dispersions of these galaxies with the self-similar radial profiles of the rms velocity and of the Gauss-Hermite moment h_4 observed in nearby galaxies for 0 < R < 2 R_eff. For Q0957+561, we find a 16% uncertainty in the galaxy mass, and formal 2-sigma limits on the Hubble constant of H_0 = (61 +13/-15) km/s/Mpc. For PG 1115+080, we find that none of the viable lens models can be ruled out, so that H_0 is not yet strongly constrained by this system.Comment: Revised version accepted by ApJ: slightly modified results for both lens sytems. 18 pages, with 7 inline Postscript figures, LaTeX, aaspp4.sty; postscript paper w/figs (490 kb) also available at http://cfa-www.harvard.edu/~romanow/orbit.post.v2.ps.g

The Sudden Death of the Nearest Quasar

Galaxy formation is significantly modulated by energy output from supermassive black holes at the centers of galaxies which grow in highly efficient luminous quasar phases. The timescale on which black holes transition into and out of such phases is, however, unknown. We present the first measurement of the shutdown timescale for an individual quasar using X-ray observations of the nearby galaxy IC 2497, which hosted a luminous quasar no more than 70,000 years ago that is still seen as a light echo in `Hanny's Voorwerp', but whose present-day radiative output is lower by at least 2 and more likely by over 4 orders of magnitude. This extremely rapid shutdown provides new insights into the physics of accretion in supermassive black holes, and may signal a transition of the accretion disk to a radiatively inefficient state.Comment: 4 pages, 2 figures. Astrophysical Journal Letters, in pres

Wind assessment for micro wind turbines in an urban environment

Wind flow in urban environments could be seen as a potential source of energy. This form of energy could be exploited by means of micro wind turbines placed along the existing infrastructures. To test this, an outdoor campaign was organised, which recorded the wind characteristics at different locations around a highway noise barrier in Delft, the Netherlands. The real-time data set was validated with a two-dimensional Computational Fluid Dynamics study. Both the influence of the high turbulence and the inflow angle on the positioning of the micro wind turbines are assessed for the case of perpendicular flow towards the plane of the noise barrier. Results indicated that integrating micro wind turbines with the noise barriers proves advantageous due to the flow velocity increment downstream. Lastly, a noise assessment was conducted in order to determine the optimal spacing between micro wind turbines, which impacts its social acceptance

Micro-Jy radio sources in the z=0.83 cluster MS1054-03

An extremely deep 5 GHz radio observation is presented of the rich cluster MS1054-03 at redshift z=0.83. 34 radio sources are detected down to a 32 micro-Jy (6 sigma), compared to about 25 expected from previous blank field radio source count determinations; the sources giving rise to these excess counts lie within 2 arcmins (700 kpc) of the cluster centre. Existing imaging and spectroscopy has provided optical identifications for 21 of the radio sources and redshifts for 11, of which 8 are confirmed cluster members. 4 of these 8 confirmed cluster sources are associated with close galaxy pairs (10-25 kpc projected offset) of similar magnitude, implying that the radio source may be triggered by an interaction. However, although MS1054-03 has a very high fraction (17%) of on-going mergers (separations <~ 10 kpc), no radio emission is detected towards any of these merger events, setting a mean upper limit of 10 Msun/yr for any star formation associated with these mergers. This supports a hypothesis that low luminosity radio sources may be onset by initial weak interactions rather than direct mergers. The host galaxies of the other four confirmed cluster radio sources are all isolated, and show a range of morphologies from early-type to Sc. A comparison between the emission line and radio luminosities suggests that two of these four radio sources are low-luminosity AGN, whilst for at least one of the other two the radio emission is associated with on-going star formation. All of the radio sources associated with the galaxy pairs appear more likely AGN than starburst origin. The overall proportion of radio sources associated with AGN in this cluster (>75%) is higher than at these flux density levels in the field (40-50%).Comment: 19 pages LaTeX, including 8 figures. Accepted for publication in MNRAS. Version with higher resolution figures available from http://www.roe.ac.uk/~pnb/papers.htm

What are the odds? Identifying factors related to competitive success in powerlifting

Background: The ability for athletes to gain a competitive advantage over their opponents is well recognised. At times, this advantage may be considered a marginal gain. However, in the context of competition, marginal advantages may be the difference between winning and losing. This investigation explores how competition factors influence the odds of competitive success (i.e. winning) in powerlifting (PL) to assist athletes and coaches in achieving a competitive advantage. Methods: A cross-sectional, retrospective analysis of competition data from raw/classic, Australian powerlifting competitions 2010–2019 was conducted. Data included 10,599 competition entries (males: n = 6567 [62%], females: n = 4032 [38%]). Independent t-tests were used to compare continuous data between sexes or winners and non-winners at an event. Cohen’s d and the 95% confidence interval (d [95% CI]) were calculated. Univariate odds of winning an event based on independent variables (age [irrespective of category], sex, body weight and weight of first lift attempt [regardless of success]), were assessed by separate simple logistic regression. Results: When compared to males, the odds of winning for females were 50% greater (OR [95% CI] 1.500 [1.384, 1.625]; P \u3c 0.001). Athletes who had larger first lift attempts (Squat: + 7.0 kg P \u3c 0.001, Bench Press: + 3.2 kg P \u3c 0.001, and Deadlift: + 6.1 kg P \u3c 0.001and competed for a longer period (winners: 401 vs non-winners: 304 days, P \u3c 0.001) had an increased likelihood winning. Age was associated with increased odds of success for males (OR [95% CI] 1.014 [1.009, 1.019], P \u3c 0.001) per additional year of age for males, but not females (P = 0.509). Conclusions: Multiple factors appear to contribute to the likelihood of winning a PL competition. These results may help coaches to develop competition and training strategies that optimise athletes’ likelihood of competitive success in PL

Anharmonic double-phonon excitations in the interacting boson model

Double-$\gamma$ vibrations in deformed nuclei are analyzed in the context of the interacting boson model. A simple extension of the original version of the model towards higher-order interactions is required to explain the observed anharmonicities of nuclear vibrations. The influence of three- and four-body interactions on the moments of inertia of ground- and $\gamma$-bands, and on the relative position of single-$\gamma$ and double-$\gamma$ bands is studied in detail. As an example of a realistic calculation, spectra and transitions of the highly $\gamma$-anharmonic nuclei $^{164}$Dy, $^{166}$Er, and $^{168}$Er are interpreted in this approach.Comment: 38 pages, TeX (ReVTeX). 15 ps figures. Submitted to Phys. Rev.

First e-VLBI observations of Cygnus X-3

We report the results of the first two 5 GHz e-VLBI observations of the X-ray binary Cygnus X-3 using the European VLBI Network. Two successful observing sessions were held, on 2006 April 20, when the system was in a quasi-quiescent state several weeks after a major flare, and on 2006 May 18, a few days after another flare. At the first epoch we detected faint emission probably associated with a fading jet, spatially separated from the X-ray binary. The second epoch in contrast reveals a bright, curved, relativistic jet more than 40 milliarcseconds in extent. In the first, and probably also second epochs, the X-ray binary core is not detected, which may indicate a temporary suppression of jet production as seen in some black hole X-ray binaries in certain X-ray states. Spatially resolved polarisation maps at the second epoch provide evidence of interaction between the ejecta and the surrounding medium. These results clearly demonstrate the importance of rapid analysis of long-baseline observations of transients, such as facilitated by e-VLBI.Comment: Accepted for publication as a letter in MNRA