The expanding dusty bipolar nebula around the nova V1280 Sco

V1280 Sco is one of the slowest dust-forming nova ever historically observed. We performed multi-epoch high-spatial resolution observations of the circumstellar dusty environment of V1280 Sco to investigate the level of asymmetry of the ejecta We observed V1280 Sco in 2009, 2010 and 2011 using unprecedented high angular resolution techniques. We used the NACO/VLT adaptive optics system in the J, H and K bands, together with contemporaneous VISIR/VLT mid-IR imaging that resolved the dust envelope of V1280 Sco, and SINFONI/VLT observations secured in 2011. We report the discovery of a dusty hourglass-shaped bipolar nebula. The apparent size of the nebula increased from 0.30" x 0.17" in July 2009 to 0.64" x 0.42" in July 2011. The aspect ratio suggests that the source is seen at high inclination. The central source shines efficiently in the K band and represents more than 56+/-5% of the total flux in 2009, and 87+/-6% in 2011. A mean expansion rate of 0.39+/-0.03 mas per day is inferred from the VISIR observations in the direction of the major axis, which represents a projected upper limit. Assuming that the dust shell expands in that direction as fast as the low-excitation slow ejecta detected in spectroscopy, this yields a lower limit distance to V1280 Sco of 1kpc; however, the systematic errors remain large due to the complex shape and velocity field of the dusty ejecta. The dust seems to reside essentially in the polar caps and no infrared flux is detected in the equatorial regions in the latest dataset. This may imply that the mass-loss was dominantly polar

SDSS J162520.29+120308.7 – a new SU Ursae Majoris star in the period gap

We report results of an extensive world-wide observing campaign devoted to the recently discovered dwarf nova SDSS J162520.29+120308.7 (SDSS J1625). The data were obtained during the July 2010 eruption of the star and in August and September 2010 when the object was in quiescence. During the July 2010 superoutburst, SDSS J1625 clearly displayed superhumps with a mean period of Psh = 0.095942(17) days (138.16 ± 0.02 min) and a maximum amplitude reaching almost 0.4 mag. The superhump period was not stable, decreasing very rapidly at a rate of ˙P = −1.63(14) × 10−3 at the beginning of the superoutburst and increasing at a rate of ˙P = 2.81(20) × 10−4 in the middle phase. At the end of the superoutburst, it stabilized around the value of Psh = 0.09531(5) day. During the first twelve hours of the superoutburst, a low-amplitude double wave modulation was observed whose properties are almost identical to early superhumps observed in WZ Sge stars. The period of early superhumps, the period of modulations observed temporarily in quiescence, and the period derived from radial velocity variations are the same within measurement errors, allowing us to estimate the most probable orbital period of the binary to be Porb = 0.09111(15) days (131.20 ± 0.22 min). This value clearly indicates that SDSS J1625 is another dwarf nova in the period gap. Knowledge of the orbital and superhump periods allows us to estimate the mass ratio of the system to be q ≈ 0.25. This high value poses serious problems for both the thermal and tidal instability (TTI) model describing the behaviour of dwarf novae and for some models explaining the origin of early superhumps

A STUDY OF THE EFFECT OF HYDROGEN SULFIDE ON CONVENTIONAL AND RESIN-MODIFIED GLASS-IONOMER DENTAL CEMENTS

The effect of aqueous hydrogen sulfide on the properties of a conventional and a resin-modified glass-ionomer dental cement has been determined. Specimens were stored for 1 week in (i) H₂S/glycerol/water, (ii) glycerol/water and (iii) pure water. After this time, the mass changes were determined, the pH of the solution was measured and the ion-content was determined, the latter by ICP-OES. There were significant differences in the mass uptake, pH change and ion release of the cements. Both showed significant gains in mass in both water and water/glycerol. In H₂S /water/glycerol Ketac Cem (a conventional glass-ionomer) showed an insignificant mass loss, and Fuji Plus showed a minor significant gain. Both materials altered the pH of all storage solutions significantly. The pH of the H₂S /water/glycerol medium increased whereas the pH of both pure water and water/glycerol went down. The ion release into glycerol/water was different from release into water, with sodium release being suppressed. The H₂S medium showed almost no differences from glycerol/water, indicating that the H₂S component has almost no effect on these cements. This leads to the conclusion that these cements can safely be used sub-gingivally even in patients where oral malodour suggests that reasonable amounts of H₂S may be present

SDSS J162520.29+120308.7 – A New SU Ursae Majoris Star in the Period Gap

We report results of an extensive world-wide observing campaign devoted to the recently discovered dwarf nova SDSS J162520.29+120308.7 (SDSS J1625). The data were obtained during the July 2010 eruption of the star and in August and September 2010 when the object was in quiescence

SDSS J162520.29+120308.7-a new SU Ursae Majoris star in the period gap

We report results of an extensive world-wide observing campaign devoted to the recently discovered dwarf nova SDSS J162520.29+120308.7 (SDSS J1625). The data were obtained during the July 2010 eruption of the star and in August and September 2010 when the object was in quiescence. During the July 2010 superoutburst, SDSS J1625 clearly displayed superhumps with a mean period of P-sh = 0.095942(17) days (138.16 +/- 0.02 min) and a maximum amplitude reaching almost 0.4 mag. The superhump period was not stable, decreasing very rapidly at a rate of. P = -1.63(14) x 10(-3) at the beginning of the superoutburst and increasing at a rate of. P = 2.81(20) x 10(-4) in the middle phase. At the end of the superoutburst, it stabilized around the value of P-sh = 0.09531(5) day