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Register a new userPhotometric evolution, orbital modulation and progenitor of Nova Mon 2012
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We present and discuss accurate and densely mapped BVRI lightcurves of the neon Nova Mon 2012, supplemented by the evolution in Stromgren b and y bands and in the integrated flux of relevant emission lines. Our monitoring started with the optical discovery of the nova and extend to day +270, well past the end of the super-soft phase in X-rays. The nova displayed very smoothly evolving lightcurves. A bifurcation between y and V light-curves took place at the start of the SSS phase, and a knee developed toward the end of the SSS phase. The apparent magnitude of the nova at the unobserved optical maximum is constrained to +2.8=<V=<4.2. The appearance, grow in amplitude and then demise of a 0.29585 (+/-0.00002) days orbital modulation of the optical brightness was followed along the nova evolution. The observed modulation has a near-sinusoidal shape and a weak secondary minimum at phase 0.5. We favor an interpretation in terms of super-imposed ellipsoidal distortion of the Roche lobe filling companion and irradiation of its side facing the WD. Similar lightcurves are typical of symbiotic stars where a Roche lobe filling giant is irradiated by a very hot WD. Given the high orbital inclination, mutual occultation between the donor star and the accretion disk could contribute to the observed modulation. The optical+infrared spectral energy distribution of Nova Mon 2012 during the quiescence preceeding the outburst is nicely fitted by a early K-type main-sequence star (~K3V) at 1.5 kpc distance, reddened by E(B-V)=0.38, with a WD companion and an accretion disk contributing to the observed blue excess and moderate Halpha emission. A typical early K-type main-sequence star with a mass of ~0.75 Msun and a radius of ~0.8 Rsun, would fill its Roche lobe for a P=0.29585 day orbital period and a more massive WD companion.
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Nova Mon 2012 was the first classical nova to be detected as a high energy $gamma$-ray transient, by Fermi-LAT, before its optical discovery. We study a time sequence of high resolution optical echelle spectra (Nordic Optical Telescope) and contemporaneous NOT, STIS UV, and CHIRON echelle spectra (Nov 20/21/22). We use [O III] and H$beta$ line fluxs to constrain the properties of the ejecta. We derive the structure from the optical and UV line profiles and compare our measured line fluxes for with predictions using Cloudy with abundances from other ONe novae. Mon 2012 is confirmed as an ONe nova. We find E(B-V)=0.85$pm$0.05 and hydrogen column density $approx 5times 10^{21}$ cm$^{-2}$. The corrected continuum luminosity is nearly the same in the entire observed energy range as V1974 Cyg, V382 Mon, and Nova LMC 2000 at the same epoch after outburst. The distance, about 3.6 kpc, is quite similar to V1974 Cyg. The line profiles can be modeled using an axisymmetric bipolar geometry for the ejecta with various inclinations of the axis to the line of sight, 60 le i le 80 degrees, an opening angle of approx$70 deg, inner radius $Delta R/R(t)approx 0.4$ for permitted lines and less filled for forbidden lines. The filling factor $fapprox 0.1-0.3$ implying M(ejecta) $leq 6times 10^{-5}$M$_odot$. The ONe novae appear to comprise a single physical class with bipolar high mass ejecta, similarly enhanced abundances, and a common spectroscopic evolution within a narrow range of luminosities. The detected $gamma$-ray emission may be a generic phenomenon, common to all ONe novae, possibly to all classical novae, and connected with acceleration and emission processes within the ejecta (abstract severely truncated).
Of the 350 or more known Galactic classical novae, only a handful of them, the recurrent novae, have been observed in outburst more than once. At least eight of these recurrents are known to harbour evolved secondary stars, rather than the main sequence secondaries typical in classical novae. Here we present a selection of the work and rationale that led to the proposal of a new nova classification scheme based not on the outburst properties but on the nature of the quiescent system. Also outlined are the results of a photometric survey of a sample of quiescent Galactic novae, showing that the evolutionary state of the secondary can be easily determined and leading to a number of predictions. We discuss the implications of these results, including their relevance to extragalactic work and the proposed link to type Ia supernovae. We also present a summary of the work using the SMEI instrument to produce exquisite nova light-curves and confirmation of the pre-maximum halt.
We present a survey of M31 novae in quiescence. This is the first catalogue of extragalactic systems in quiescence and contains 37 spectroscopically confirmed novae from 2006 to 2013. We used Liverpool Telescope and Faulkes Telescope North images taken during outburst to identify accurate positions for each system. These positions were then transformed to archival Hubble Space Telescope (HST) images and we performed photometry on any resolvable source that was consistent with the transformed positions. As red giants in M31 will be resolvable in the HST images, we can detect systems with red giant secondaries. There are only a few confirmed examples of such systems in our Galaxy (e.g. RS Oph and T CrB). However, we find a much higher portion of the nova population in M31 may contain red giant secondaries. For some novae, coincident HST images had been taken when the nova was still fading, allowing us to produce light curves that go fainter than is possible to achieve for most extragalactic systems. Finally, we compare the M31 and Galactic quiescent nova populations.
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.
We present results from photometric monitoring of V900 Mon, one of the newly discovered and still under-studied object from FU Orionis type. FUor phenomenon is very rarely observed, but it is essential for stellar evolution. Since we only know about twenty stars of this type, the study of each new object is very important for our knowledge. Our data was obtained in the optical spectral region with BVRI Johnson-Cousins set of filters during the period from September 2011 to April 2021. In order to follow the photometric history of the object, we measured its stellar magnitudes on the available plates from the Mikulski Archive for Space Telescopes. The collected archival data suggests that the rise in brightness of V900 Mon began after January 1989 and the outburst goes so far. In November 2009, when the outburst was registered, the star had already reached a level of brightness close to the current one. Our observations indicate that during the period 2011-2017 the stellar magnitude increased gradually in each pass band. The observed amplitude of the outburst is about 4 magnitudes (R). During the last three years, the increase in brightness has stopped and there has even been a slight decline. The comparison of the light curves of the known FUor objects shows that they are very diverse and are rarely repeated. However, the photometric data we have so far shows that the V900 Mons light curve is somewhat similar to this of V1515 Cyg and V733 Cep.
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