Outburst evolution, historic light curve and a flash-ionized nebula around the WZ Sge-type object PNV J03093063+2638031

We have monitored the 2014 superoutburst of the WZ Sge-type transient PNV J03093063+2638031 for more than four months, from V=11.0 maximum brightness down to V=18.4 mag, close to quiescence value, by obtaining BVRI photometry and low resolution fluxed spectroscopy. The evolution was normal and no late-time `echo' outbursts were observed. The absolute integrated flux of emission lines kept declining along the superoutburst, and their increasing contrast with the underlying continuum was simply the result of the faster decline of the continuum compared to the emission lines. Inspection of historical Harvard plates covering the 1899-1981 period did not reveal previous outbursts, neither `normal' nor 'super'. We discovered an extended emission nebula (radius ~1 arcmin) around PNV J03093063+2638031, that became visible for a few months as the result of photo-ionization from the superoutburst of the central star. It is not present on Palomar I and II sky survey images and it quickly disappeared when the outburst was over. From the rate at wich the inization front swept through the nebula, we derive a distance of ~120 pc to the system. The nebula is density bounded with an outer radius of 0.03 pc, and the absolute magnitude of the central star in quiescence is M(V)~14.2 mag. The electron density in the nebula is estimated to be 10(+5) cm(-3) from the observed recombination time scale. Given the considerable substructures seen across the nebula, a low filling factor is inferred. Similar nebulae have not been reported for other WZ Sge objects and the challenges posed to models are considered.Comment: Astronomy & Astrophysic

Developing positive attitude towards science and mathematics through motivational classroom experiences

This paper presents results of a survey among school children aged 10 to 14 years, who participated in science or mathematics workshops. It particularly relates to their interest and motivation determined immediately after the workshop had finished. A total of 70 workshops were held in elementary schools of Rijeka, Croatia, involving the participation of 1240 students aged from 10 to 14 years. The workshops were designed in order to encourage active engagement in class work and a deeper approach to learning stemming from meaningful involvement in a real problem related to everyday life. The results of the survey on student’s attitudes towards science and mathematics after the workshop indicated that students accept this type of lesson eagerly, they value demonstrations, applications and practical, hands-on experimentation, and that after this type of classroom activity they express positive attitude towards science and mathematics

Developing positive attitude towards science and mathematics through motivational classroom experiences

This paper presents results of a survey among school children aged 10 to 14 years, who participated in science or mathematics workshops. It particularly relates to their interest and motivation determined immediately after the workshop had finished. A total of 70 workshops were held in elementary schools of Rijeka, Croatia, involving the participation of 1240 students aged from 10 to 14 years. The workshops were designed in order to encourage active engagement in class work and a deeper approach to learning stemming from meaningful involvement in a real problem related to everyday life. The results of the survey on student’s attitudes towards science and mathematics after the workshop indicated that students accept this type of lesson eagerly, they value demonstrations, applications and practical, hands-on experimentation, and that after this type of classroom activity they express positive attitude towards science and mathematics

The nature and evolution of Nova Cygni 2006

AIMS: Nova Cyg 2006 has been intensively observed throughout its full outburst. We investigate the energetics and evolution of the central source and of the expanding ejecta, their chemical abundances and ionization structure, and the formation of dust. METHOD: We recorded low, medium, and/or high-resolution spectra (calibrated into accurate absolute fluxes) on 39 nights, along with 2353 photometric UBVRcIc measures on 313 nights, and complemented them with IR data from the literature. RESULTS: The nova displayed initially the normal photometric and spectroscopic evolution of a fast nova of the FeII-type. Pre-maximum, principal, diffuse-enhanced, and Orion absorption systems developed in a normal way. After the initial outburst, the nova progressively slowed its fading pace until the decline reversed and a second maximum was reached (eight months later), accompanied by large spectroscopic changes. Following the rapid decline from second maximum, the nova finally entered the nebular phase and formed optically thin dust. We computed the amount of formed dust and performed a photo-ionization analysis of the emission-line spectrum during the nebular phase, which showed a strong enrichment of the ejecta in nitrogen and oxygen, and none in neon, in agreement with theoretical predictions for the estimated 1.0 Msun white dwarf in Nova Cyg 2006. The similarities with the poorly investigated V1493 Nova Aql 1999a are discussed.Comment: in press in Astronomy and Astrophysic

On the Progenitor System of Nova V2491 Cygni

Nova V2491 Cyg is one of just two detected pre-outburst in X-rays. The light curve of this nova exhibited a rare "re-brightening" which has been attributed by some as the system being a polar, whilst others claim that a magnetic WD is unlikely. By virtue of the nature of X-ray and spectroscopic observations the system has been proposed as a recurrent nova, however the adoption of a 0.1 day orbital period is generally seen as incompatible with such a system. In this research note we address the nature of the progenitor system and the source of the 0.1 day periodicity. Through the combination of Liverpool Telescope observations with published data and archival 2MASS data we show that V2491 Cyg, at a distance of 10.5 - 14 kpc, is likely to be a recurrent nova of the U Sco-class; containing a sub-giant secondary and an accretion disk, rather than accretion directly onto the poles. We show that there is little evidence, at quiescence, supporting a ~ 0.1 day periodicity, the variation seen at this stage is likely caused by flickering of a re-established accretion disk. We propose that the periodicity seen shortly after outburst is more likely related to the outburst rather than the - then obscured - binary system. Finally we address the distance to the system, and show that a significantly lower distance (~ 2 kpc) would result in a severely under-luminous outburst, and as such favour the larger distance and the recurrent nova scenario.Comment: 5 pages, 3 images, accepted for publication in A&A as a research not

The Morphology of the Expanding Ejecta of V2491 Cygni (2008 N.2)

Determining the evolution of the ejecta morphology of novae provides valuable information on the shaping mechanisms in operation at early stages of the nova outburst. Understanding such mechanisms has implications for studies of shaping for example in proto-Planetary Nebulae. Here we perform morpho-kinematical studies of V2491 Cyg using spectral data to determine the likely structure of the ejecta and its relationship to the central system and shaping mechanisms. We use Shape to model different morphologies and retrieve their spectra. These synthetic spectra are compared with observed spectra to determine the most likely morphology giving rise to them, including system inclination and expansion velocity of the nova ejecta. We find the best fit remnant morphology to be that of polar blobs and an equatorial ring with an implied inclination of 80$^{+3}_{-12}$ degrees and an maximum expansion velocity of the polar blobs of 3100$^{+200}_{-100}$ km/s and for the equatorial ring 2700$^{+200}_{-100}$ km/s. This inclination would suggest that we should observe eclipses which will enable us to determine more precisely important parameters of the central binary. We also note that the amplitude of the outburst is more akin to the found in recurrent nova systems.Comment: 9 pages, 7 figures, accepted for publication in MNRA

Swift observations of the X-ray and UV evolution of V2491 Cyg (Nova Cyg 2008 No. 2)

We present extensive, high-density Swift observations of V2491 Cyg (Nova Cyg 2008 No. 2). Observing the X-ray emission from only one day after the nova discovery, the source is followed through the initial brightening, the Super-Soft Source phase and back to the pre-outburst flux level. The evolution of the spectrum throughout the outburst is demonstrated. The UV and X-ray light-curves follow very different paths, although changes occur in them around the same times, indicating a link between the bands. Flickering in the late-time X-ray data indicates the resumption of accretion. We show that if the white dwarf is magnetic, it would be among the most magnetic known; the lack of a periodic signal in our later data argues against a magnetic white dwarf, however. We also discuss the possibility that V2491 Cyg is a recurrent nova, providing recurrence timescale estimates.Comment: 12 pages, 8 figure (2 in colour), accepted for publication in MNRA