MV Lyrae: Entering the period gap?

MV Lyrae was studied on about 2000 photographic plates of the Moscow, Odessa and Sonneberg collections. A brief review of these results in comparison with literature data is given. The object might be a unique system, entering the period gap. Outbursts are observed in the minimum state, which may be possibly explained by the trigger mechanism for the radiation-induced mass outflow from the secondary, underfilling its Roche lobe.     

IGR J16547-1916/1RXS J165443.5-191620—a new intermediate polar from the INTEGRAL galactic survey

We present the results of our optical identification of the X-ray source IGR J16547-1916 detected by the INTEGRAL observatory during a deep all-sky survey. Analysis of the spectroscopic data from the SWIFT and INTEGRAL observatories in the X-ray energy band and from the BTA (Special Astrophysical Observatory) telescope in the optical band has shown that the source is most likely an intermediate polar—an accreting white dwarf with the mass ofM _WD μ 0.85M _⊙ binary system. Subsequent studies of the object’s rapid variability with the RTT-150 telescope have confirmed this conclusion by revealing periodic pulsations of its optical emission with a period of ≈550 s.     

Multiwavelength spectral and high time resolution observations of SWIFT J1753.5−0127: new activity?

We have conducted an extensive observational campaign of SWIFT J1753.5−0127 during 2007 June after its bright outburst episode in 2005. We have performed multiband optical photometry, optical spectroscopy, X-ray spectroscopy and timing and ULTRACAM optical photometry simultaneously in three bands. Both the optical spectrum and the X-ray spectrum along with enhanced brightness in broad-band photometry point to recent increased activity. We analyse the different spectral regions, finding a smooth optical continuum with a remarkable lack of lines and a very blue component modulated with a period of 3.2 h and a hard power-law X-ray spectrum. Both the X-ray and optical power spectra are flat at low frequencies up to the 0.1 Hz (10 s) range, then decreasing roughly as a power law consistent with flickering. Furthermore, the optical data show quasi-periodic oscillations near 0.08 Hz (13 s). Together with a dynamical and autocorrelation analysis of the light curves we attempt to construct a complete physical picture of this intriguing system.     

What is the nature of RX J0720.4–3125?

RX J0720.4–3125 has recently been identified as a pulsating soft X-ray source in the ROSAT all-sky survey with a period of 8.391 s. Its spectrum is well characterized by a blackbody with a temperature of 8 × 10⁵ K. We propose that the radiation from this object is thermal emission from a cooling neutron star. For this blackbody temperature we can obtain a robust estimate of the object's age of ∼ 3 × 10⁵ yr, yielding a polar field ∼ 10¹⁴ G for magnetic dipole spin-down and a value of P compatible with current observations.     

The micro-glitch in PSR B1821−24: a case for a strange pulsar?

The single glitch observed in PSR B1821−24, a millisecond pulsar in M28, is unusual on two counts. First, the magnitude of this glitch is at least an order of magnitude smaller  (Δν/ν∼ 10⁻¹¹)  than the smallest glitch observed to date. Secondly, all other glitching pulsars have strong magnetic fields with   B ≳ 10¹¹ G  and are young, whereas PSR B1821−24 is an old recycled pulsar with a field strength of  2.25 × 10⁹ G  . We have earlier suggested that some of the recycled pulsars could actually be strange quark stars. In this work, we argue that the crustal properties of such a strange pulsar are just right to give rise to a glitch of this magnitude, explaining the scarcity of larger glitches in millisecond pulsars.     

The phenomenon of the galaxy NGC 6286: A forming polar ring or a superwind?

We present our observations of the pair of interacting galaxies NGC 6285/86 carried out with the 6-m Special Astrophysical Observatory (SAO) telescope using 1D and 2D spectroscopy. The observations of NGC 6286 with a long-slit spectrograph (UAGS) near the Hα line revealed the rotation of the gaseous disk around an axis offset by 5″–7″ from the photometric center and a luminous gas at a distance up to 9 kpc in a direction perpendicular to the galactic plane. Using a multipupil fiber spectrograph (MPFS), we constructed the velocity fields of the stellar and gaseous components in the central region of this galaxy, which proved to be similar. The close radial velocities of the pair and the wide (5′×5′) field of view of the scanning Fabry-Perot interferometer (IFP) allowed us to simultaneously obtain images in the Hα and [N II]λ6583 lines and in the continuum, as well as to construct the radial velocity fields and to map the distribution of the [N II]λ6583/Hα ratio for both galaxies. Based on all these data, we studied the gas kinematics in the galaxies, constructed their rotation curves, and estimated their masses (2 × 10¹¹M_⊙ for NGC 6286 and 1.2 × 10¹⁰M_⊙ for NGC 6285). We found no evidence of gas rotation around the major axis of NGC 6286, which argues against the assumption that this galaxy has a forming polar ring. The IFP observations revealed an emission nebula around this galaxy with a structure characteristic of superwind galaxies. The large [N II]λ6583/Hα ratio, which suggests the collisional excitation of its emission, and the high infrared luminosity are additional arguments for the hypothesis of a superwind in the galaxy NGC 6286. A close encounter between the two galaxies was probably responsible for the starburst and the bipolar outflow of hot gas from the central region of the disk.     

Observations of the extreme-ultraviolet transient RE J1255+266: a short outburst of a WZ Sge system?

We present a previously unpublished ROSAT Wide Field Camera observation of the transient source RE J1255+266 made just 4 d before the discovery observations. The source is not detected, limiting the duration of the outburst to be less than expected for a superoutburst of a WZ Sge system.
We also present a marginal detection of X-ray emission from RE J1255+266 using ASCA . The most probable luminosity is 6×10²⁹ erg s⁻¹, which is very similar to WZ Sge itself.
We discuss the nature of the source in the light of these observations, and conclude that it is most probably a WZ Sge system, but that the observed outburst must have been a normal dwarf nova outburst.     

The stellar system HIP 101227: is it a binary,a triple or a quadruple system?

In this paper, we present the analysis of the stellar system HIP 101227 to determine the actual number of components in the system, and their properties. We use dynamical modeling and complex spectrophotometric(involving atmospheric modeling) techniques with recent data, to determine the physical properties and orbital solution for the system, respectively, with better accuracy than past studies. Based on our analysis, we found that the system is more consistent with being a quadruple rather than a binary or a triple system as suggested by previous studies. The total mass of the system determined from our SED analysis is 3.42 ± 0.20 M, which is distributed almost equally between the four stars. The stars are found to be zero-age main sequence stars; i.e., at the last stage of pre-main sequence, with age less than 200 Myr and spectral types K0. All four stars have very similar physical characteristics, suggesting that the fragmentation process is the most likely theory for the formation and evolution of the system.     

The potential for photosynthesis in hydrothermal vents: a new avenue for life in the Universe?

We perform a quantitative assessment for the potential for photosynthesis in hydrothermal vents in the deep ocean. The photosynthetically active radiation in this case is from geothermal origin: the infrared thermal radiation emitted by hot water, at temperatures ranging from 473 up to 673 K. We find that at these temperatures the photosynthetic potential is rather low in these ecosystems for most known species. However, species which a very high efficiency in the use of light and which could use infrared photons till 1300 nm, could achieve good rates of photosynthesis in hydrothermal vents. These organisms might also thrive in deep hydrothermal vents in other planetary bodies, such as one of the more astrobiologically promising Jupiter satellites: Europa.     

Is SN 2006X from a WD + MS system with optically thick wind?

The single-degenerate channel is widely accepted as the progenitors of type Ia supernovae (SNe Ia). Following the work of Meng et al. (2009a), we reproduced the birth rate and age of supernovae like SN 2006X by the single-degenerate model (WD + MS) with an optically thick wind, which may imply that the progenitor of SN 2006X is a WD + MS system.     

V 361 Lyrae: An exotic binary system with a “Hot Spot” between the components?

A phenomenological model for V 361 Lyr is proposed. Probably it is a binary system which consists of a mass accreting primary star with mass of about M₁ ≈ 0·81 M⊙ and radius R₁ ≈ (6.1 ± 0·4) · 10¹⁰ cm and a mass losing secondary with about M₂ ≈ 0·77 M⊙ and R₂ ≈ 5.8 · 10¹⁰ cm. The secondary fills its Roche lobe, but the primary is something smaller than this lobe, contrary to the models of W UMa-type systems. So the hot spot appears in the atmosphere of the primary, but not in a disk, like in cataclysmic variables. The luminosity of the hot spot, L = (6-15) · 10³² erg/s, is large enough to be the main emission source of the system in visible light. So phenomenologically the object may be somewhat between W UMa-type stars and cataclysmic variables.     

Radio properties of the Shapley Concentration — II. J1324–3138: a remnant of a radio galaxy in the Abell cluster A3556?

In this paper we present a detailed study of the radio galaxy J1324–3138, located at a projected distance of 2 arcmin from the centre of the Abell cluster of galaxies A3556, belonging to the core of the Shapley Concentration, at an average redshift of z  = 0.05. We have observed J1324–3138 over a wide range of frequencies: at 327 MHz (VLA), 843 MHz (MOST), and at 1376, 2382, 4790 and 8640 MHz (ATCA).   Our analysis suggests that J1324–3138 is a remnant of a tailed radio galaxy, in which the nuclear engine has switched off and the radio source is now at a late stage of its evolution, confined by the intracluster gas. The radio galaxy is not in pressure equilibrium with the external medium, as is often found for extended radio sources in clusters of galaxies. We favour the hypothesis that the lack of observed polarized radio emission in the source is a result of Faraday rotation by a foreground screen, i.e. the source is seen through a dense cluster gas, characterized by a random magnetic field.   An implication of the head–tail nature of the source is that J1324–3138 is moving away from the core of A3556 and that, possibly, a major merging event between the core of A3556 and the subgroup hosting J1324–3138 has already taken place.     

The unusual X-ray light curve of GRB 080307: the onset of the afterglow?

Swift -detected GRB 080307 showed an unusual smooth rise in its X-ray light curve around 100 s after the burst, at the start of which the emission briefly softened. This 'hump' has a longer duration than is normal for a flare at early times and does not demonstrate a typical flare profile. Using a two-component power-law-to-exponential model, the rising emission can be modelled as the onset of the afterglow, something which is very rarely seen in Swift -X-ray light curves. We cannot, however, rule out that the hump is a particularly slow early-time flare, or that it is caused by upscattered reverse shock electrons.     

SDSS J121606.5+280648.5: a helium-core white dwarf in an eclipsing binary system?

A comparison of Palomar Observatory Sky Survey (POSS) and Sloan Digital Sky Survey (SDSS) images showed SDSS J121606.5+280648.5 to have increased in brightness by nearly two magnitudes since 1955. SDSS J121606.5+280648.5 turned out to be a low-mass white dwarf having a less luminous cool companion, probably a late-type Main Sequence dwarf. A possible explanation of brightening is that the companion eclipsed the white dwarf at the time the POSS plate was obtained. If SDSS J121606.5+280648.5 is an eclipsing binary, further study should help establish circumstances in which rapid mass loss occurs on the Red Giant Branch (RGB).