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Register a new userThe orbital ephemeris of the classical nova RR Pictoris: presence of a third body?
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Added by
Irma Fuentes Morales
Publication date
2016
fields
Physics
and research's language is
English
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The ex-nova RR Pic presents a periodic hump in its light curve which is considered to refer to its orbital period. Analyzing all available epochs of these hump maxima in the literature, and combining them with those from new light curves obtained in 2013 and 2014, we establish an unique cycle count scheme valid during the past 50 years, and derive an ephemeris with the orbital period 0.145025959(15) days. The O - C diagram of this linear ephemeris reveals systematic deviations which could have different causes. One of them could be a light-travel-time effect caused by the presence of a hypothetical third body near the star/brown dwarf mass limit, with an orbital period of the order of 70 years. We also examine the difficulty of the problematic of detecting sub-stellar or planetary companions of close red-dwarf white-dwarf binaries (including cataclysmic variables), and discuss other possible mechanisms responsible for the observed deviations in O - C. For RR Pic, we propose strategies in order to solve this question by new observations.
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We present an analysis of all available time-resolved photometry from the literature and new light curves obtained in 2013-2014 for the old nova RR Pictoris. The well-known hump light curve phased with the orbital period reveals significant variations over the last 42 years in shape, amplitude and other details which apparently are caused by long-term variations in the disc structure. In addition we found evidence for the presence of superhumps in 2007, with the same period (~9% longer than the orbital period), as reported earlier by other authors from observations in 2005. Possibly, superhumps arise quickly in RR Pic, but are sporadic events, because in all the other observing runs analysed no significant superhump signal was detected. We also determined an actual version of the Stolz--Schoembs relation between superhump period and orbital period, analysing separately dwarf novae, classical novae and nova-like stars, and conclude that this relation is of general validity for all superhumpers among the cataclysmic variables (CVs), in spite of small but significant differences among the sub-types mentioned above. We emphasize the importance of such a study in context with the still open question of the interrelation between the different sub-classes of CVs, crucial for our understanding of the long-term CV evolution.
Combining with our newest CCD times of light minimum of EM Cygni, all 45 available times of light minimum including 7 data with large scatters are compiled and the updated O-C analysis is made. The bestfit for the O-C diagram of EM Cygni is a quadratic-plus-sinusoidal fit. The secular orbital period decrease rate -2.5(pm 0.3)x10^{-11} s s^{-1} means that magnetic braking effect with a rate of mass loss via stellar wind, 2.3x10^{-10}Msunyr^{-1}, is needed for explaining the observed orbital period decrease. Moreover, for explaining the significant cyclical period change with a period of sim 17.74(pm 0.01)yr shown in the O-C diagram, magnetic activity cycles and light travel-time effect are discussed in detail. The O-C diagram of EM Cygni cannot totally rule the possibility of multi-periodic modulation out due to the gaps presented after 25000 cycles. Based on the hypothesis of a K-type third star in literature, light trave-time effect may be a more plausible explanation. However, the low orbital inclination of the third body (sim 7.4 degree) suggests that the hypothetic K-type third star may be captured by EM Cygni. But assuming the spectral contamination from a block of circumbinary material instead of a K-type third star, the third star may be a brown dwarf in case of the coplanar orbit with parent binary.
We collected rich series of RV measurements covering last 110 years and photometric observations from the past 6 primary eclipses, complemented them by our new observations and derived a new precise ephemeris and an orbital solution of epsilon Aur.
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).
The morphology and optical spectrum of IPHASXJ210205+471015, a nebula classified as a possible planetary nebula, are however strikingly similar to those of ATCnc, a classical nova shell around a dwarf nova. To investigate its true nature, we have obtained high-resolution narrow-band [O III] and [N II] images and deep GTC OSIRIS optical spectra. The nebula shows an arc of [N II]-bright knots notably enriched in nitrogen, whilst an [O III]-bright bow-shock is progressing throughout the ISM. Diagnostic line ratios indicate that shocks are associated with the arc and bow-shock. The central star of this nebula has been identified by its photometric variability. Time-resolved photometric and spectroscopic data of this source reveal a period of 4.26 hours, which is attributed to a binary system. The optical spectrum is notably similar to that of RWSex, a cataclysmic variable star (CV) of the UXUMa nova-like (NL) type. Based on these results, we propose that IPHASX J210205+471015 is a classical nova shell observed around a CV-NL system in quiescence.
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