CP Pup Research Articles

TESS light curves of cataclysmic variables – I – Unknown periods in long-known stars

ABSTRACT Cataclysmic variables (CVs) exhibit a plethora of variable phenomena many of which require long, uninterrupted light curves to reveal themselves in detail. The month long data sets provided by TESS are well suited for this purpose. TESS has the additional advantage to have observed a huge number of stars, among them many CVs. Here, a search for periodic variations in a sample of CVs of the novalike and old novae subtypes is presented. In 10 of the 15 targets either previously unseen positive or negative superhumps or unusual features in known superhumps are identified. The TESS light curves demonstrate that the occurrence of superhumps in these types of CVs is not an exception but quite common. For 8 systems new or improved values for the orbital period are measured. In TV Col the long-sought optical manifestation of the white dwarf spin period is first seen in form of its orbital sideband. The mystery of multiple photometric periods observed in CP Pup in the past is explained by irregularly occurring anomalous states which are reflected in the light curve.

On the nature of CP Pup

We present new X-ray and optical spectra of the old nova CP Pup (nova Pup 1942) obtained with Chandra and the CTIO 4m telescope. The X-ray spectrum reveals a multi-temperature optically thin plasma reaching a maximum temperature of 36$^{+19}_{-16}$ keV absorbed by local complex neutral material. The time resolved optical spectroscopy confirms the presence of the $\sim$1.47 hr period, with cycle-to-cycle amplitude changes, as well as of an additional long term modulation which is suggestive either of a longer period or of non-Keplerian velocities in the emission line regions. These new observational facts add further support to CP Pup as a magnetic cataclysmic variable (mCV). We compare the mCV and the non-mCV scenarios and while we cannot conclude whether CP Pup is a long period system, all observational evidences point at an intermediate polar (IP) type CV.

The old nova CP Puppis: a carbon nova and asynchronous polar?

Context. CP Pup (Nova Pup 1942) showed outburst and quiescent characteristics indicating a very massive white dwarf, yet the standard spectroscopic dynamical analysis assuming an accretion disk yields an extremely low value for the white dwarf mass. However, some physical parameters and the accretion geometry are still poorly known.

NOVAE WITH LONG-LASTING SUPERSOFT EMISSION THAT DRIVE A HIGH ACCRETION RATE

We identify a new class of novae characterized by the post-eruption quiescent light curve being more than roughly a factor of ten brighter than the pre-eruption light curve. Eight novae (V723 Cas, V1500 Cyg, V1974 Cyg, GQ Mus, CP Pup, T Pyx, V4633 Sgr, and RW UMi) are separated out as being significantly distinct from other novae. This group shares a suite of uncommon properties, characterized by the post-eruption magnitude being much brighter than before eruption, short orbital periods, long-lasting supersoft emission following the eruption, a highly magnetized white dwarf, and secular declines during the post-eruption quiescence. We present a basic physical picture which shows why all five uncommon properties are causally connected. Most novae do not have adequate accretion for continuous hydrogen burning, but some can achieve this if the companion star is nearby (with short orbital period) and a magnetic field channels the matter onto a small area on the white dwarf so as to produce a locally high accretion rate. The resultant supersoft flux irradiates the companion star and drives a higher accretion rate (with a brighter post-eruption phase), which serves to keep the hydrogen burning and the supersoft flux going. The feedback loop cannot be perfectly self-sustaining, so the supersoft flux will decline over time, forcing a decline in the accretion rate and the system brightness. We name this new group after the prototype, V1500 Cyg. V1500 Cyg stars are definitely not progenitors of Type Ia supernovae. The V1500 Cyg stars have similar physical mechanisms and appearances as predicted for nova by the hibernation model, but with this group accounting for only 14% of novae.

NEW X-RAY OBSERVATIONS OF THE OLD NOVA CP PUPPIS AND OF THE MORE RECENT NOVA V351 PUPPIS

We present X-ray observations of the field containing Nova Puppis 1942 (CP Pup) and Nova Puppis 1991 (V351 Pup), done with ASCA in 1998, and with XMM-Newton in 2005. The X-ray and UV luminosity of CP Pup seem to have remained approximately constant since the last X-ray observations of the 1980'ies, while the optical luminosity has decreased. The X-ray properties of this nova are explained by a high mass white dwarf accreting at low rate, in agreement with the nova theory given the large amplitude and other characteristics of the 1942 outburst. Assuming a distance of 1600 pc, the X-ray luminosity of CP Pup is L=2.2 x 10(33) erg/s in the 0.15-10 keV range covered with EPIC, compatible with a magnetic system. The RGS grating spectrum shows a few prominent emission lines, and it is fitted with a cooling flow with mass accretion rate mdot <= 1.6 x 10(-10) msol/year. We detected also the O VII complex at 21.6-21.8 A that does not arise in the cooling flow. Most likely this feature originates in a wind or in the nova shell. The RGS and EPIC spectra are fitted only with thermal models with a very high shock temperature, T>60 keV, indicating a white dwarf with M>1.1 M(sun). The X-ray flux is modulated with the spectroscopic period of 1.47 hours detected in the optical. Since CP Pup is not an eclipsing system, this is better understood if magnetic accretion occurs: we discuss this possibility and its implications in detail. V351 Pup (N Pup 1991) was detected with XMM-Newton, but not with ASCA. It is a faint, non-super-soft X-ray source with luminosity L(x) =~ 3 x 10(31) erg/s, a factor of 50 less than measured with ROSAT in 1993.

On the possibility of systematizing classical novae by light curve type. II. Observational characteristics of novae and groups

The separation of novae into groups, proposed in Part 1 of this paper, is discussed: it is based on the criterion of the shape of the light curve, plotted on “outburst amplitude-logarithm of shell radius ” scales. The observational characteristics of novae belonging to certain groups are considered. Novae of the GQ Mus group may be characterized by x ray emission. The proposed separation of novae into groups may be related to the structure of the shell ejected in the outburst. Novae with smooth light curves have ellipsoidal shells without pronounced nonuniformities. Novae with temporary fading or with brightness fluctuations in the transitional stage of the outburst have ellipsoidal shells with a nonuniform distribution of matter (equatorial and tropical belts in novae of the DQ Her group, an equatorial belt for the RR Pic group, and a patchy structure for the CP Pup group). Relationships among certain parameters of novae are considered: absolute stellar magnitude, outburst amplitude, shell expansion velocity, etc. From the “depth of temporary fading in the transitional stage of the outburst-shell expansion velocity” dependence it can be concluded that the kinetic energy of the shell may be a constant for novae of the DQ Her group.

On the possibility of systematizing classical novae by light curve type. I. Type criteria

Nova light curves, plotted on “outburst amplitude-logarithm of main shell radius” axes, have differences that can be systematized. As a result of a survey of over 90 novae, nova groups that are typical in light curve shape have been distinguished: DQ Her, CP Pup, RR Pic, PU Vul, V1974 Cyg, CP Lac, and GQ Mus. The light curve criterion is supplemented by other characteristics. The DQ Her group includes only novae having dust formation in the ejected shell. The GQ Mus group combines certain novae with smooth light curves that are separated into several subgroups with respect to outburst amplitude and the duration of the light curve section before the transitional stage, but for which the linear section of the light curve has the same slope.

Deep optical imaging of nova remnants: a southern sky sample

We present an optical imaging study of 20 southern sky nova remnants which has resulted in the discovery of four previously unknown nova shells — those of V842 Cen, RR Cha, DY Pup and HS Pup. The study has also revealed previously unobserved features in three other known shells — those of BT Mon, CP Pup and RR Pic. The images of BT Mon, V842 Cen, RR Cha, DY Pup and HS Pup have been processed using several deconvolution algorithms (Richardson–Lucy, maximum entropy and CLEAN) in addition to straightforward point-source subtraction in an attempt to resolve the shells from the central stars. The use of four different methods enables us to make a qualitative judgment of the results. Notably, the shell of RR Pic displays tails extending outwards from clumps in the main ejecta similar to those previously detected in DQ Her.

Predicting the future of superhumps in classical nova systems

Oscillations observed in the light curve of Nova V1974 Cygni 1992 since summer 1994 have been interpreted as permanent superhumps. From simple calculations based on the Tidal-Disk Instability model of Osaki, and assuming that the accretion disc is the dominant optical source in the binary system, we predict that the nova will evolve to become an SU UMa system as its brightness declines from its present luminosity by another 2-3 magnitudes. Linear extrapolation of its current rate of fading (in magnitude units) puts the time of this phase transition within the next 2-4 years. Alternatively, the brightness decline will stop before the nova reaches that level, and the system will continue to show permanent superhumps in its light curve. It will then be similar to two other old novae, V603 Aql and CP Pup, that still display the permanent superhumps phenomenon 79 and 55 years, respectively, after their eruptions. We suggest that non-magnetic novae with short orbital periods could be progenitors of permanent superhump systems.

CP Puppis - No ordinary old nova

We present spectrophotometric data for the old nova CP Puppis (Nova Puppis 1942) that demonstrates the simultaneous existence of two distinct periods for the system. We find that the photometric period of 0.06834(7) day is 11 percent longer than the spectroscopic period. We also present Doppler tomographic images of CP Pup that indicate the existence of an accretion disk in the system. Finally, we interpret the observational evidence in terms of a DQ Herculis model and an SU Ursae Majoris model for CP Pup. While the evidence mildly supports both interpretations, it is insufficient for us to conclusively classify CP Pup as either a DQ Her system or an SU UMa system.

Nitrogen recombination lines and abundance in nova shells

view Abstract Citations (8) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Nitrogen Recombination Lines and Abundance in Nova Shells Escalante, Vladimir ; Dalgarno, Alexander Abstract The observed intensities of N II lines in the DQ Her, CP Pup, and T Aur nova shells are compared with theoretical predictions. It is concluded that the relative intensities can be explained with excitation by recombination. The nitrogen abundances obtained from the line intensities relative to hydrogen have values about 400 to 700 times the solar abundance. Publication: The Astrophysical Journal Pub Date: March 1991 DOI: 10.1086/169752 Bibcode: 1991ApJ...369..213E Keywords: Atomic Recombination; Line Spectra; Nitrogen Atoms; Novae; Recombination Reactions; Stellar Envelopes; Abundance; Atomic Excitations; Nuclear Fusion; Astrophysics; ATOMIC PROCESSES; NEBULAE: ABUNDANCES; STARS: NOVAE full text sources ADS | data products SIMBAD (3)

Photoionization modelling of metal-enriched nova shells

A photoionization model has been developed to investigate the physical conditions in old nova shells with large metal abundances. Atomic rates at low temperatures are included in the model so that the evolution of shells can be traced from their hot, early stages to their later cool phases. X-ray processes are also included. A situation in which a region of lowest temperature but highest ionization can exist at the inner edge of a nebula is demonstrated. A non-uniform density distribution (1/R2) is compared with a uniform density and the observational consequences discussed. The shell of the old nova, CP Pup, is analyzed in detail and its evolution during its constant-luminosity phase traced. The CNO abundances, nitrogen in particular, must be enhanced with respect to solar values to explain the observations. The strongest emission from the shell during most of its constant-luminosity phase was from N III 57 μm and was also responsible for most of the cooling in the gas. Conflicting reports on the distance to nova CP Pup are examined, from which a distance of 800 pc is determined.

Low-temperature recombination coefficients and nova-shell abundances

Capture-collision-cascade models developed for calculating recombination specta of H I, He I and CNO ions from a neutral to a doubly ionised state are described. The results of computations at low temperatures, i.e. between 321.5 and 2500 K, are presented. Forbidden-line fluxes, formed by recombination, are also listed. The data are used to check the line identification in the spectra of the cool nova shells of DQ Her, T Aur and CP Pup.

ONeMg novae and the evolution of their shells

The properties of ONeMg novae are summarized and compared with the features seen in the optical spectra of old classical novae. None of the old novae had ejection velocities as high as those of the ONeMg novae. Photo-ionization models of nova shells are used to trace how the ejecta from ONeMg novae should evolve, and to predict what old ONeMg nova shells should look like. Finally, the model developed for CP Pup is used with enhanced neon abundances to see the effect it has on the evolution of the shell. A neon enhancement of between 10 and 100 times the solar abundance would most probably not have been noticed in the spectra of this object.

CP Puppis: Another V1500 Cyg?

As first pointed out by Warner (1985), the overall properties of CP Pup and V1500 Cyg are very similar: both were very fast, very large amplitude novae with ~ 0.3 mag photometric humps at roughly the orbital period. Neither variation is strictly periodic (Patterson 1979; Warner 1985). Variable circular polarization (with period slightly different from the orbital period) has been found in V1500 Cyg showing that its white dwarf is strongly magnetic and has broken synchronism with the secondary star (Stockman, Schmidt &amp; Lamb 1988). In contrast, no circular polarization has been found in CP Pup. Nonetheless, does the slight difference between the photometric and spectroscopic periods indicate it is also a magnetic system (Warner 1985; Bianchini et al. 1985a)?New photometric and spectroscopic data for CP Pup are reported which resolve the aliases and confusion in the periods found by Bianchini et al. (1985a,b), Warner (1985) and Duerbeck et al. (1987) and allow an examination of the evidence for its magnetic nature.

Cool Envelopes of Post-Novae Constraints on the Decline of the White Dwarf

Some post-novae, e.g. DQ Her, CP Pup, T Aur, have cool envelopes, Te &lt; 1000K. As has been shown by Ferland et al. (1984) this effect is primarily due to large overabundances of the CNO elements which at low densities can very effectively cool off the nebular gas through infra-red lines.We have constructed an extensive grid of photoionization models in order to study the exact conditions required for the electron temperature to drop to such low values. As can be seen in Figs. 1 to 4, our results can be summarized as follows.1- The abundance of oxygen which is the dominant coolant in the conditions considered has to be at least 10 times the solar value (with C and N accordingly overabundant).2- The gas density, n, has to be below 1000cm−3.3- The effective temperature of the ionizing source, Teff, has to be below 2 105K.4- The ionization parameter U = QH / (4πr2nc) (QH: number of ionizing photons emitted per second by the central source, r: radius of the envelope) has to be between a certain range, typically 10−2 &lt; U &lt; 10−3, whose exact limits, however, depend on other parameters such as Teff and the abundances.

Spectroscopic Observations of the Southern Old Novae CP Pup and V841 Oph

AbstractNew spectroscopic observations of the old nova CP Pup suggest most probable orbital period of 0.061375 days. First systematic monitoring of the very old nova V841 Oph reveals orbital motion with a most probable period of about 0.6 days. A slightly eccentric solution at P = 0.3755 days is less probable.

On the nature of the old nova CP Puppis

We report on nearly 48 hr of high speed photometry of the exnova CP Pup, obtained at Sutherland or Mount Stromlo, and 23 hr of spectroscopic coverage from Sutherland, during the period 1985–88. Analysis of the photometry and radial velocities derived from the spectroscopy gives a modulation period of 0.06143 d, free from the alias problems inherent in previous work, and identical for both photometry and spectroscopy. This period will not fit the earlier data of Warner and this, together with substantial amplitude variations in the photometric modulation, suggest the presence of more than one photometric periodicity. Measurements of the radial velocity semi-amplitude give values of |$\sim 200\,\text{km s}^{-1}$| near the emission line centres, decreasing to |$\sim 120\,\text{km s}^{-1}$| in the line wings, but with variations in phase across the line profile. A related V/R effect is seen. There is evidence for repetitive fine structure in the line profiles, but at a level too low to study in detail with the present spectra. If the K velocity of |$\sim 120\,\text{km s}^{-1}$| is representative of the motion of the white dwarf, unreasonable values of the white-dwarf mass and orbital inclination are derived. No compelling evidence has emerged from the present study to suggest that CP Pup is a magnetic cataclysmic variable, although further study of the behaviour of the photometric modulation may elucidate this question.

Spectroscopic analysis of the extended shells around the novae CP Puppis and T. Pyxidis

view Abstract Citations (70) References (31) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectroscopic analysis of the extended shells around the novae CP Pupand T Pyx. Williams, R. E. Abstract Spectral scans have been obtained of the spatially resolved shells surrounding the novae CP Pup and T Pyx. The CP Pup shell is similar to the DQ Her envelope in being moderately ionized, but quite cold. It emits an unusual spectrum in which nitrogen recombination lines, including forbidden N II formed by recombination, are unusually strong, signifying an extreme nitrogen enrichment, with N/H about 0.1 by number. The strongest optical CNO recombination lines expected from a moderately ionized gas are considered, but no heavy elements other than nitrogen are definitely present. The recurrent nova T Pyx has a shell, apparently ejected in the 1966 outburst, whose spectrum is very similar to that of a planetary nebula. The shell is hot and probably photoionized by radiation from the nova, but is lacking in the strong CNO enhancements characteristic of all classical nova shells so far studied. Publication: The Astrophysical Journal Pub Date: October 1982 DOI: 10.1086/160328 Bibcode: 1982ApJ...261..170W Keywords: Astronomical Spectroscopy; Nebulae; Novae; Accretion Disks; Emission Spectra; Ion Recombination; Line Spectra; Nitrogen; Stellar Models; Astrophysics full text sources ADS | data products SIMBAD (3)