Optical Observations of M81 Galaxy Group in Narrow Band [SII] and H_alpha Filters: Holmberg IX

We present observations of the nearby tidal dwarf galaxy Holmberg IX in M81 galaxy group in narrow band [SII] and H$\alpha$ filters, carried out in March and November 2008 with the 2m RCC telescope at NAO Rozhen, Bulgaria. Our search for resident supernova remnants (identified as sources with enhanced [SII] emission relative to their H$\alpha$ emission) in this galaxy yielded no sources of this kind, besides M&H 10-11 or HoIX X-1. Nevertheless, we found a number of objects with significant H$\alpha$ emission that probably represent uncatalogued HII regions.Comment: 8 pages, 5 figure

Discovery of a pulsar-powered bow shock nebula in the Small Magellanic Cloud supernova remnant DEMS5

We report the discovery of a new Small Magellanic Cloud pulsar wind nebula (PWN) at the edge of the supernova remnant (SNR) DEMS5. The pulsar powered object has a cometary morphology similar to the Galactic PWN analogues PSR B1951+32 and ´the mouse´. It is travelling supersonically through the interstellar medium.We estimate the pulsar kick velocity to be in the range of 700-2000 km s-1 for an age between 28 and 10 kyr. The radio spectral index for this SNR-PWN-pulsar system is flat (-0.29 ± 0.01) consistent with other similar objects. We infer that the putative pulsar has a radio spectral index of -1.8, which is typical for Galactic pulsars. We searched for dispersion measures up to 1000 cm-3 pc but found no convincing candidates with an S/N greater than 8. We produce a polarization map for this PWN at 5500 MHz and find a mean fractional polarization of P ∼ 23 per cent. The X-ray power-law spectrum (τ ∼ 2) is indicative of non-thermal synchrotron emission as is expected from PWN-pulsar system. Finally, we detect DEMS5 in infrared (IR) bands. Our IR photometric measurements strongly indicate the presence of shocked gas that is expected for SNRs. However, it is unusual to detect such IR emission in an SNR with a supersonic bow shock PWN.We also find a low-velocity HI cloud of ∼107 km s-1 that is possibly interacting with DEMS5. SNR DEMS5 is the first confirmed detection of a pulsar-powered bow shock nebula found outside the Galaxy.Fil: Alsaberi, Rami Z. E.. Western Sydney University; AustraliaFil: Maitra, C.. Max Planck Institut Für Extraterrestrische Physik; AlemaniaFil: Filipovic, M. D.. Western Sydney University; AustraliaFil: Bozzetto, L.M.. Western Sydney University; AustraliaFil: Haberl, F.. Max Planck Institut Für Extraterrestrische Physik; AlemaniaFil: Maggi, P.. Université de Strasbourg; FranciaFil: Sasaki, M.. Universitat Erlangen-Nuremberg; AlemaniaFil: Manjolovic, P.. Western Sydney University; AustraliaFil: Velovic, V.. University Of Belgrade; SerbiaFil: Kavanagh, P.. Dublin Institute For Advanced Studies; IrlandaFil: Maxted, N. I.. University Of New South Wales (unsw) Australia; AustraliaFil: Urosevic, D.. Isaac Newton Institute Of Chile; ChileFil: Rowell, G. P.. University of Adelaide; AustraliaFil: Wong, G. F.. University Of New South Wales (unsw) Australia; AustraliaFil: For, B. Q.. The University Ofwestern Australia; AustraliaFil: O'Brien, A. N.. Western Sydney University; AustraliaFil: Galvin, T. J.. Western Sydney University; AustraliaFil: Staveley-Smith, L.. The University Ofwestern Australia; AustraliaFil: Norris, R. P.. Western Sydney University; AustraliaFil: Jarrett, T.. University Of Cape Town; SudáfricaFil: Kothes, R.. National Research Council Canada; CanadáFil: Luken, K. J.. Western Sydney University; AustraliaFil: Hurley-Walker, N.. Curtin University; AustraliaFil: Sano, H.. Nagoya University; JapónFil: Onic, D.. University Of Belgrade; SerbiaFil: Dai, S. T.. Australia Telescope National Facility; AustraliaFil: Pannuti, G.. Morehead State University; Estados UnidosFil: Tothill, N. F. H.. Western Sydney University; AustraliaFil: Crawford, Evan. Western Sydney University; AustraliaFil: Yew, M.. Western Sydney University; AustraliaFil: Bojicic, I.. Western Sydney University; AustraliaFil: Dénes, H.. Netherlands Foundation For Research In Astronomy; BélgicaFil: McClure-Griffiths, N.. Australian National University; AustraliaFil: Gurovich, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Fukui, Y.. Nagoya University; Japó

Murchison Widefield Array and XMM-Newton observations of the Galactic supernova remnant G5.9+3.1

Aims. In this paper we discuss the radio continuum and X-ray properties of the so-far poorly studied Galactic supernova remnant (SNR) G5.9 + 3.1. Methods. We present the radio spectral energy distribution (SED) of the Galactic SNR G5.9 + 3.1 obtained with the Murchison Widefield Array (MWA). Combining these new observations with the surveys at other radio continuum frequencies, we discuss the integrated radio continuum spectrum of this particular remnant. We have also analyzed an archival XMM-Newton observation, which represents the first detection of X-ray emission from this remnant. Results. The SNR SED is very well explained by a simple power-law relation. The synchrotron radio spectral index of G5.9 + 3.1 is estimated to be 0.42 ± 0.03 and the integrated flux density at 1 GHz to be around 2.7 Jy. Furthermore, we propose that the identified point radio source, located centrally inside the SNR shell, is most probably a compact remnant of the supernova explosion. The shell-like X-ray morphology of G5.9 + 3.1 as revealed by XMM-Newton broadly matches the spatial distribution of the radio emission, where the radio-bright eastern and western rims are also readily detected in the X-ray while the radio-weak northern and southern rims are weak or absent in the X-ray. Extracted MOS1+MOS2+PN spectra from the whole SNR as well as the north, east, and west rims of the SNR are fit successfully with an optically thin thermal plasma model in collisional ionization equilibrium with a column density NH ~ 0.80 × 1022 cm−2 and fitted temperatures spanning the range kT ~ 0.14–0.23 keV for all of the regions. The derived electron number densities ne for the whole SNR and the rims are also roughly comparable (ranging from ~0.20f−1∕2 to ~0.40f−1∕2 cm−3, where f is the volume filling factor). We also estimate the swept-up mass of the X-ray emitting plasma associated with G5.9+3.1 to be ~46f−1∕2 M⊙.</jats:p

An analytical model for dust impact voltage signals and its application to STEREO/WAVES data

International audienceContext. Dust impacts have been observed using radio and wave instruments onboard spacecraft since the 1980s. Voltage waveforms show typical impulsive signals generated by dust grains.Aims. We aim at developing models of how signals are generated to be able to link observed electric signals to the physical properties of the impacting dust. To validate the model, we use the Time Domain Sampler (TDS) subsystem of the STEREO/WAVES instrument which generates high-cadence time series of voltage pulses for each monopole.Methods. We propose a new model that takes impact-ionization-charge collection and electrostatic-influence effects into account. It is an analytical expression for the pulse and allows us to measure the of amount of the total ion charge, Q, the fraction of escaping charge, ϵ, the rise timescale, τi, and the relaxation timescale, τsc. The model is simple and convenient for massive data fitting. To check our model’s accuracy, we collected all the dust events detected by STEREO/WAVES/TDS simultaneously on all three monopoles at 1AU since the beginning of the STEREO mission in 2007.Results. Our study confirms that the rise time largely exceeds the spacecraft’s short timescale of electron collection. Our estimated rise time value allows us to determine the propagation speed of the ion cloud, which is the first time that this information has been derived from space data. Our model also makes it possible to determine properties associated with the electron dynamics, in particular the order of magnitude of the electron escape current. The obtained value gives us an estimate of the cloud’s electron temperature – a result that, as far as we know, has never been obtained before except in laboratory experiments. Furthermore, a strong correlation between the total cloud charge and the escaping charge allows us to estimate the escaping current from the amplitude of the precursor, a result that could be interesting for the study of the pulses recently observed in the magnetic waveforms of Solar Orbiter or Parker Solar Probe, for which the electric waveform is saturated

Murchison Widefield Array and XMM-Newton observations of the Galactic supernova remnant G5.9+3.1

Aims. In this paper we discuss the radio continuum and X-ray properties of the so-far poorly studied Galactic supernova remnant (SNR) G5.9 + 3.1. Methods. We present the radio spectral energy distribution (SED) of the Galactic SNR G5.9 + 3.1 obtained with the Murchison Widefield Array (MWA). Combining these new observations with the surveys at other radio continuum frequencies, we discuss the integrated radio continuum spectrum of this particular remnant. We have also analyzed an archival XMM-Newton observation, which represents the first detection of X-ray emission from this remnant. Results. The SNR SED is very well explained by a simple power-law relation. The synchrotron radio spectral index of G5.9 + 3.1 is estimated to be 0.42 ± 0.03 and the integrated flux density at 1 GHz to be around 2.7 Jy. Furthermore, we propose that the identified point radio source, located centrally inside the SNR shell, is most probably a compact remnant of the supernova explosion. The shell-like X-ray morphology of G5.9 + 3.1 as revealed by XMM-Newton broadly matches the spatial distribution of the radio emission, where the radio-bright eastern and western rims are also readily detected in the X-ray while the radio-weak northern and southern rims are weak or absent in the X-ray. Extracted MOS1+MOS2+PN spectra from the whole SNR as well as the north, east, and west rims of the SNR are fit successfully with an optically thin thermal plasma model in collisional ionization equilibrium with a column density NH ~ 0.80 × 1022 cm−2 and fitted temperatures spanning the range kT ~ 0.14–0.23 keV for all of the regions. The derived electron number densities ne for the whole SNR and the rims are also roughly comparable (ranging from ~0.20f−1∕2 to ~0.40f−1∕2 cm−3, where f is the volume filling factor). We also estimate the swept-up mass of the X-ray emitting plasma associated with G5.9+3.1 to be ~46f−1∕2 M⊙.D. Onić, M. D. Filipović, I. Bojičić, N. Hurley-Walker, B. Arbutina, T. G. Pannuti, C. Maitra, D. Urošević, F. Haberl, N. Maxted, G. F. Wong, G. Rowell, M. E. Bell, J. R. Callingham, K. S. Dwarakanath, B.-Q. For, P. J. Hancock, L. Hindson, M. Johnston-Hollitt, A. D. Kapińska, E. Lenc, B. McKinley, J. Morgan, A. R. Offringa, L. E. Porter, P. Procopio, L. Staveley-Smith, R. B. Wayth, C. Wu and Q. Zhen