X-ray observations of PSR B0355+54 and its pulsar wind nebula

We present X-ray data of the middle-aged radio pulsar PSR B0355+54. The XMM-Newton and Chandra observations show not only emission from the pulsar itself, but also compact diffuse emission extending ∼50″ in the opposite direction to the pulsar’s proper motion. Our analysis also indicates the presence of fainter diffuse emission extending ∼5′ from the point source. The morphology of the diffuse component is similar to the ram-pressure confined pulsar wind nebulae detected for other sources. We find that the compact diffuse component is well-fitted with a power-law, with an index that is consistent with the values found for other pulsar wind nebulae. The core emission from the pulsar can be characterized with a thermal plus power-law fit, with the thermal emission most likely originating in a hot polar cap.     

The XMM-Newton view of the yellow hypergiant IRC + 10420 and its surroundings

Among evolved massive stars likely in transition to the Wolf–Rayet phase, IRC + 10420 is probably one of the most enigmatic. It belongs to the category of yellow hypergiants and it is characterized by quite high mass loss episodes. Even though IRC + 10420 benefited of many observations in several wavelength domains, it has never been a target for an X-ray observatory. We report here on the very first dedicated observation of IRC + 10420 in X-rays, using the XMM-Newton satellite. Even though the target is not detected, we derive X-ray flux upper limits of the order of 1–3 × 10⁻¹⁴ erg cm⁻² s⁻¹ (between 0.3 and 10.0 keV), and we discuss the case of IRC + 10420 in the framework of emission models likely to be adequate for such an object. Using the Optical/UV Monitor on board XMM-Newton, we present the very first upper limits of the flux density of IRC + 10420 in the UV domain (between 1800 and 2250 Å and between 2050 and 2450 Å). Finally, we also report on the detection in this field of 10 X-ray and 7 UV point sources, and we briefly discuss their properties and potential counterparts at longer wavelengths.     

Evidence for a possible black hole remnant in the Type IIL Supernova 1979C

We present an analysis of archival X-ray observations of the Type IIL supernova SN 1979C. We find that its X-ray luminosity is remarkably constant at (6.5 ± 0.1) × 10³⁸ erg s^?1 over a period of 12 years between 1995 and 2007. The high and steady luminosity is considered as possible evidence for a stellar-mass (～5–10 M_⊙) black hole accreting material from either a supernova fallback disk or from a binary companion, or possibly from emission from a central pulsar wind nebula. We find that the bright and steady X-ray light curve is not consistent with either a model for a supernova powered by magnetic braking of a rapidly rotating magnetar, or a model where the blast wave is expanding into a dense circumstellar wind.     

Characteristics of planetary-scale waves simulated by a new venusian mesosphere and thermosphere general circulation model

We have developed a new general circulation model (GCM) for the venusian mesosphere and thermosphere (80-about 180 km). Our GCM simulations show that winds in the subsolar-to-antisolar direction (SS–AS) are predominant above about 90 km. A weak return flow of the SS–AS is seen below about 90 km. We performed GCM simulations imposing the planetary-scale waves (thermal tides, Rossby wave, and Kelvin wave) at the lower boundary. Although the diurnal and semidiurnal tides are damped below 95 km, the Rossby wave propagates up to around 130 km. However, the amplitude of the Rossby wave is too small (<1 m/s) to affect the general circulation. On the other hand, the Kelvin wave propagates up to about 130 km with a maximum zonal wind fluctuation of approximately 5.9 m/s on average. The amplitude of the Kelvin wave sometimes exceeds 10 m/s around the terminator. The Kelvin wave causes a temporal variation in the wind velocity at the altitude of the O₂-1.27 μm nightglow emission (about 95 km). Using a newly developed 1-D nightglow model and the composition distribution calculated from our GCM, we investigated the impact of the Kelvin wave on the nightglow distribution. Our results suggest that the Kelvin wave would cause temporal variations in the nightglow emission in the 23:50–00:20 LT region with an intensity of 1.1–1.3 MR and a period of approximately 4 days.     

The source of the helium visible lines in η Carinae

We assume that the helium-I lines emitted by the massive binary system η Carinae are formed in the acceleration zone of the less-massive secondary star. We calculate the Doppler shift of the lines as a function of orbital phase and of several parameters of the binary system. We find that a good fit is obtained if the helium lines are formed in the region where the secondary wind speed is v_zone = 430 km s⁻¹. The acceptable binary eccentricity is in the range 0.90 ≲ e ≲ 0.95, and the inclination angle (the angle between a line perpendicular to the orbital plane and the line of sight) is in the range 40° ≲ i ≲ 55°. Lower values of e require higher values of i, and vice versa. The binary system is oriented such that the secondary star is in our direction (closer to us) during periastron passage. The orbital motion can account in part to the Doppler shift of the peak in X-ray emission.     

Laboratory studies on the sputtering contribution to the sodium atmospheres of Mercury and the Moon

To ascertain the importance of sputtering by solar wind ions on the formation of a sodium exosphere around Mercury and the Moon, we have irradiated with 4 keV He ions, the Na bearing tectosilicates: albite, labradorite, and anorthoclase, as well as adsorbed Na layers deposited on albite and on olivine (a neosilicate that does not contain Na). Sodium at the surface and near surface (<40 Å) was quantified with X-ray photoelectron spectroscopy before and after each irradiation to determine the depletion cross section. We measured a cross section for sputtering of Na adsorbed on mineral surfaces, σ_s ≈ 1 × 10^?15 cm² atom^?1. In addition, mass spectrometric analyses of the sputtered flux show that a large fraction of the Na is sputtered as ions rather than as neutral atoms. These results have strong implications for modeling the sodium population within the mercurian and the lunar exospheres.     

Spectral behavior of the symbiotic nova AG Pegasi observed with IUE and HST

Ultraviolet spectra from the International Ultraviolet Explorer (IUE) and from the Hubble Space Telescope (HST) of the symbiotic novae AG Peg during the period 1978–1996 are analyzed. Some spectra showing the modulations of spectral lines at different times are presented. We determined the reddening from the 2200 Å feature, finding that E(B−V) = 0.10 ± 0.02. We studied N IV] at 1486 Å, C IV 1550 Å, and O III] at 1660 Å, produced in the fast wind from the hot white dwarf. The mean wind velocity of the three emission lines is 1300 km s⁻¹ (FWHM). The mean wind mass loss rate is ∼6 × 10⁻⁷ M_⊙ yr⁻¹. The mean temperature is ∼6.5 × 10⁵ K. The mean ultraviolet luminosity is ∼5 × 10³³ erg s⁻¹. The modulations of line fluxes in the emitting region at different times are attributed to the variations of density and temperature of the ejected matter as a result of variations in the rate of mass loss.     

The symbiotic system AG Draconis: Soft X-ray bremsstrahlung from the nebulae

The modeling of UV and optical spectra emitted from the symbiotic system AG Dra, adopting collision of the winds, predicts soft X-ray bremsstrahlung from nebulae downstream of the reverse shock with velocities > 150 km s^?1 and intensities comparable to those of the WD black body flux. At outbursts, the envelop of debris, which corresponds to the nebula downstream of the high velocity shocks (700–1000 km s^?1) accompanying the blast wave, absorbs the black body soft X-ray flux from the WD, explains the broad component of the H and He lines, and leads to low optical-UV–X-ray continuum fluxes. The high optical-UV flux observed at the outbursts is explained by bremsstrahlung downstream of the reverse shock between the stars. The depletion of C, N, O, and Mg relative to H indicates that they are trapped into dust grains and/or into diatomic molecules, suggesting that the collision of the wind from the WD with the dusty shells, ejected from the RG with a ～1 year periodicity, leads to the U-band fluctuations during the major bursts.     

Hβ line width and the UV–X-ray spectra of luminous AGN

The width of the broad Hβ emission line is the primary defining characteristic of the NLS1 class. This parameter is also an important component of Boroson and Green’s optical “Eigenvector 1” (EV1), which links steeper soft X-ray spectra with narrower Hβ emission, stronger Hβ blue wing, stronger optical Fe II emission, and weaker [O III] λ5007. Potentially, EV1 represents a fundamental physical process linking the dynamics of fueling and outflow with the accretion rate. We attempted to understand these relationships by extending the optical spectra into the UV for a sample of 22 QSOs with high quality soft-X-ray spectra, and discovered a whole new set of UV relationships that suggest that high accretion rates are linked to dense gas and perhaps nuclear starbursts. While it has been argued that narrow (BLR) Hβ means low Black Hole mass in luminous NLS1s, the C IV λ1549 and Lyα emission lines are broader, perhaps the result of outflows driven by their high Eddington accretion rates. We present some new trends of optical-UV with X-ray spectral energy distributions. Steeper X-ray spectra appear associated with stronger UV relative to optical continua, but the presence of strong UV absorption lines is associated with depressed soft X-rays and redder optical–UV continua.     

Io: Volcanic thermal sources and global heat flow

We have examined thermal emission from 240 active or recently-active volcanic features on Io and quantified the magnitude and distribution of their volcanic heat flow during the Galileo epoch. We use spacecraft data and a geological map of Io to derive an estimate of the maximum possible contribution from small dark areas not detected as thermally active but which nevertheless appear to be sites of recent volcanic activity. We utilize a trend analysis to extrapolate from the smallest detectable volcanic heat sources to these smallest mapped dark areas. Including the additional heat from estimates for “outburst” eruptions and for a multitude of very small (“myriad”) hot spots, we account for ～62 × 10¹² W (～59 ± 7% of Io’s total thermal emission). Loki Patera contributes, on average, 9.6 × 10¹² W (～9.1 ± 1%). All dark paterae contribute 45.3 × 10¹² W (～43 ± 5%). Although dark flow fields cover a much larger area than dark paterae, they contribute only 5.6 × 10¹² W (～5.3 ± 0.6%). Bright paterae contribute ～2.6 × 10¹² W (～2.5 ± 0.3%). Outburst eruption phases and very small hot spots contribute no more than ～4% of Io’s total thermal emission: this is probably a maximum value. About 50% of Io’s volcanic heat flow emanates from only 1.2% of Io’s surface. Of Io’s heat flow, 41 ± 7.0% remains unaccounted for in terms of identified sources. Globally, volcanic heat flow is not uniformly distributed. Power output per unit surface area is slightly biased towards mid-latitudes, although there is a stronger bias toward the northern hemisphere when Loki Patera is included. There is a slight favoring of the northern hemisphere for outbursts where locations were well constrained. Globally, we find peaks in thermal emission at ～315°W and ～105°W (using 30° bins). There is a minimum in thermal emission at around 200°W (almost at the anti-jovian longitude) which is a significant regional difference. These peaks and troughs suggest a shift to the east from predicted global heat flow patterns resulting from tidal heating in an asthenosphere. Global volcanic heat flow is dominated by thermal emission from paterae, especially from Loki Patera (312°W, 12°N). Thermal emission from dark flows maximises between 165°W and 225°W. Finally, it is possible that a multitude of very small hot spots, smaller than the present angular resolution detection limits, and/or cooler, secondary volcanic processes involving sulphurous compounds, may be responsible for at least part of the heat flow that is not associated with known sources. Such activity should be sought out during the next mission to Io.     

Preliminary results of the spectral analysis of Suzaku data of SW Ursae Majoris and BZ Ursae Majoris

Herein, we present the preliminary results of the spectral analysis of the Suzaku data of SW Ursae Majoris (SW UMa) and BZ Ursae Majoris (BZ UMa) which were obtained in their quiescent states. The aim of this study was to analyse 0.5–6.0 keV energy range X-ray photons of the Suzaku satellite and to determine their emission mechanisms and the areas where they were radiated from these two dwarf novae. No study on this energy range for BZ UMa has been reported in the literature. We analysed the Suzaku data in the (0.5–6.0) keV and in (0.5–2.5) keV energy bands of the systems separatelly to search for possible differences between the emission mechanisms in the energy ranges; however, none were found. We obtained the best-fitted spectral models, flux, luminosity, temperature and mass accretion rate values for the systems. The white dwarf radius of BZ UMa, which has not been reported in the literature, was found to be 6.88 × 10⁸ cm. From this study, we concluded that the mass accretion rate values for both systems were lower than the critical mass accretion rate value in the boundary layers of cataclysmic variables, which indicates that the boundary layers are composed of optically thin thermal X-ray emitting gas in their quiescent state; these results support those of previous studies regarding SW UMa and some studies regarding BZ UMa. Another result was that there can be a coronal structure above the boundary layer which act as soft X-ray emitter for SW UMa.     

Astrophysical and structural parameters of the open clusters NGC 6866, NGC 7062, and NGC 2360

We derive astrophysical and structural parameters of the poorly studied open clusters NGC 6866, NGC 7062, and NGC 2360 based on filtered 2MASS (J, J ? H) diagrams, and stellar radial density profiles. The field star decontamination technique is utilised for selecting high-probability cluster members. The E(B ? V) reddening values of the three clusters derived from 2MASS JHK_s agree with those inferred from UBV and uvby ? β photometries. We find that the core mass function slopes are flatter than the halo’s for the three clusters. The large core and cluster radii of NGC 6866 and NGC 2360 indicate an expanded core, which may suggest the presence of stellar mass black-holes. NGC 2360 is located in the third quadrant (? = 229°.80), where Giant Molecular Clouds are scarce that, together with its relatively large mass (～1800 m_⊙), might explain its longevity (～1.8 Gyr) in the Galaxy.     

Charting thermal emission variability at Pele,Janus Patera and Kanehekili Fluctus with the Galileo NIMS Io Thermal Emission Database (NITED)

Using the NIMS Io Thermal Emission Database (NITED), a collection of over 1000 measurements of radiant flux from Io’s volcanoes (Davies, A.G. et al. [2012]. Geophys. Res. Lett. 39, L01201. doi:10.1029/2011GL049999), we have examined the variability of thermal emission from three of Io’s volcanoes: Pele, Janus Patera and Kanehekili Fluctus. At Pele, the 5-μm thermal emission as derived from 28 night time observations is remarkably steady at 37 ± 10 GW μm^?1, re-affirming previous analyses that suggested that Pele an active, rapidly overturning silicate lava lake. Janus Patera also exhibits relatively steady 5-μm thermal emission (≈20 ± 3 GW μm^?1) in the four observations where Janus is resolved from nearby Kanehekili Fluctus. Janus Patera might contain a Pele-like lava lake with an effusion rate (Q_F) of ≈40–70 m³ s^?1. It should be a prime target for a future mission to Io in order to obtain data to determine lava eruption temperature. Kanehekili Fluctus has a thermal emission spectrum that is indicative of the emplacement of lava flows with insulated crusts. Effusion rate at Kanehekili Fluctus dropped by an order of magnitude from ≈95 m³ s^?1 in mid-1997 to ≈4 m³ s^?1 in late 2001.     

Spectral behavior of AE Aqr between high and low states in the UV

We present ultraviolet spectra of the AE Aqr binary system taken by the International Ultraviolet Explorer (IUE) during the period from 1978 to 1993, to accomplish a large scale study of what happens to the ultraviolet fluxes of different emission lines during different orbital phases. Five profiles of AE Aqr binary system show variations of line fluxes at different orbital phases are presented. We concentrated on studying N V emission line at 1240 Å, O I emission line at 1306 Å, He II emission line at 1640 Å, N III emission line at 1749 Å and Si III emission line at 1892 Å, produced in the line emitting gas (Eracleous et al., 1994, Eracleous and Horne, 1996), by calculating the line fluxes of these spectral lines. Our results show that there are spectral variations of line fluxes for the aforementioned emission lines at different times, similar to the light curves found for AE Aqr binary system by using ASCA, XMM – Newton and Chandra X-ray observations (Mauche, 2006). We attributed these spectral variations to the variations of the mass-transfer rate (Ikhsanov et al., 2004) and to the collisions between the compact blobs and the fluffy blobs, where the collisions are supersonic, shocking the gas, causing heating, then expansion (Eracleous et al., 1994, Eracleous and Horne, 1996, Horne, 2009).     

Latest results on Jovian disk X-rays from XMM-Newton

We present the results of a spectral study of the soft X-ray emission (0.2–2.5 keV) from low-latitude (‘disk’) regions of Jupiter. The data were obtained during two observing campaigns with XMM-Newton in April and November 2003. While the level of the emission remained approximately the same between April and the first half of the November observation, the second part of the latter shows an enhancement by about 40% in the 0.2–2.5 keV flux. A very similar, and apparently correlated increase, in time and scale, was observed in the solar X-ray and EUV flux.The months of October and November 2003 saw a period of particularly intense solar activity, which appears reflected in the behavior of the soft X-rays from Jupiter's disk. The X-ray spectra, from the XMM-Newton EPIC CCD cameras, are all well fitted by a coronal model with temperatures in the range 0.4–0.5 keV, with additional line emission from Mg XI (1.35 keV) and Si XIII (1.86 keV): these are characteristic lines of solar X-ray spectra at maximum activity and during flares.The XMM-Newton observations lend further support to the theory that Jupiter's disk X-ray emission is controlled by the Sun, and may be produced in large part by scattering, elastic and fluorescent, of solar X-rays in the upper atmosphere of the planet.     

Quantification of middle and lower cloud variability and mesoscale dynamics from Venus Express/VIRTIS observations at 1.74 μm

We present an analysis of VIRTIS-M-IR observations of 1.74 μm emission from the nightside of Venus. The 1.74 μm window in the near infrared spectrum of Venus is an ideal proxy for investigating the evolution of middle and lower cloud deck opacity of Venus because it exhibits good signal to noise due to its brightness, good contrast between bright and dark regions, and few additional sources of extinction beside the clouds themselves. We have analyzed the data from the first 407 orbits (equivalent to 407 Earth days) of the Venus Express mission to determine the magnitude of variability in the 1.74 μm radiance. We have also performed an analysis of the evolution of individual features over a span of roughly 5–6 h on two successive orbits of Venus Express. We find that the overall 1.74 μm brightness of Venus has been increasing through the first 407 days of the mission, indicating a gradual diminishing of the cloud coverage and/or thickness, and that the lower latitudes exhibited more variability and more brightening than higher latitudes. We find that individual features evolve with a time scale of about 30 h, consistent with our previous analysis. Analysis of the evolution and motion of the clouds can be used to estimate the mesoscale dynamics within the clouds of Venus. We find that advection alone cannot explain the observed evolution of the features. The measured vorticity and divergence in the vicinity of the features are consistent with evolution under the influence of significant vertical motions likely driven by a radiative dynamical feedback. We measure a zonal wind speed of around 65 m/s, and a meridional wind speed around 2.5 m/s by tracking the motion of the central region of the features. But we also find that the measured wind speeds depend strongly on the points chosen for the wind speed analysis.     

VISTA Variables in the Via Lactea (VVV): The public ESO near-IR variability survey of the Milky Way

We describe the public ESO near-IR variability survey (VVV) scanning the Milky Way bulge and an adjacent section of the mid-plane where star formation activity is high. The survey will take 1929 h of observations with the 4-m VISTA telescope during 5 years (2010–2014), covering ～10⁹ point sources across an area of 520 deg², including 33 known globular clusters and ～350 open clusters. The final product will be a deep near-IR atlas in five passbands (0.9–2.5 μm) and a catalogue of more than 10⁶ variable point sources. Unlike single-epoch surveys that, in most cases, only produce 2-D maps, the VVV variable star survey will enable the construction of a 3-D map of the surveyed region using well-understood distance indicators such as RR Lyrae stars, and Cepheids. It will yield important information on the ages of the populations. The observations will be combined with data from MACHO, OGLE, EROS, VST, Spitzer, HST, Chandra, INTEGRAL, WISE, Fermi LAT, XMM-Newton, GAIA and ALMA for a complete understanding of the variable sources in the inner Milky Way. This public survey will provide data available to the whole community and therefore will enable further studies of the history of the Milky Way, its globular cluster evolution, and the population census of the Galactic Bulge and center, as well as the investigations of the star forming regions in the disk. The combined variable star catalogues will have important implications for theoretical investigations of pulsation properties of stars.     

Star forming activities in W75N and DR21 – Are the two regions in collision?

We have observed the massive star formation region W75N in ¹²CO J = 3 ? 2 with KOSMA. The profile of ¹²CO J = 3 ? 2 indicated that besides the 9 km s^?1 component, there is another component of ?3 km s^?1, which is associated with another star formation region, DR21N, located to the north of DR21. We derived the physical and dynamical parameters of the core and high velocity gas associated with the two components separately. Star forming activities were investigated, including outflows and infall analysis. The two regions overlap in space and are not connected in velocity. We found that the cloud–cloud collision scenario may not apply for the DR21/W75N case.     

Direct wind measurements from November 2007 in Venus’ upper atmosphere using ground-based heterodyne spectroscopy of CO2 at 10 μm wavelength

Between November 23 and 28, 2007, the Cologne Tuneable Heterodyne Infrared Spectrometer THIS was installed at the McMath-Pierce Solar Telescope (Kitt Peak, Arizona, USA) to determine zonal wind velocities and to estimate the subsolar-to-antisolar flow. We investigate dynamics in the upper atmosphere of Venus by measuring the Doppler shift of fully-resolved non-LTE CO₂ emission lines at 959.3917 cm^?1 (10.423 μm), which probe a narrow altitude region in Venus’ atmosphere around 110 ± 10 km (～1 μbar). The results show no significant zonal wind velocity at the equator. An increase with latitude up to 43 ± 13 m/s at a latitude of 33°N was observed. This confirms the deduction of a minor influence of Venus superrotation at an altitude of 110 km from previous measurements in May 2007 (Sornig et al., 2008). The specific observing geometry enables estimating the maximum cross terminator velocity of the subsolar-to-antisolar flow at 72 ± 47 m/s.