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1700 1720 1740 1760 1780 1800 Wavelength (A) V1668 Cyg JD 2443819.20 1700 1720 1740 1760 1780 1800 Wavelength (A) V1668 Cyg JD 2443819.20 Fig. 9.20. Development of the high-resolution IUE line structures during the nebular phase for the CO nova V1668 Cyg 1978. Notice the Hen 1640 A line showing the 'canonical' narrow emission spikes indicative of a ring-like spectrum. A fundamental consideration for modeling and interpreting the light curve is therefore clear from the profiles the ejecta are...

Novae an historical perspective

Nova, abbreviated from stella nova, means new star (the plural form is stellae novae). Although the Merriam-Webster dictionary indicates its etymological origin to be in New (Renaissance) Latin, the term is in fact found in C. Plinius Secundus, Naturae Historia, Book 2, chapter XXIV, written around AD 75 (Pliny, 1855) Idem Hipparchus novam stellam in aevo suo genitam deprehendit eiusque motu, qua die fulsit, ad dubitationem est adductus, anne hoc saepius fieret moverenturque et eae, quas...

The soft component

The most prominent spectral feature is the soft component, which is a clear signature of the ongoing hydrogen burning on top of the white dwarf. Its origin and behaviour can be best interpreted in terms of the TNR model of the nova outburst (see, for example, Starrfield (1989) and Chapter 4). Fits to the SEDs of the super-soft phase allow temperature, luminosity and the absorbing column density NH to be derived. However, one general problem which affects all spectral fits is the absorption of...

Shortterm variability

Classical novae are highly variable sources, both on longer time-scales of weeks and months, and on short time-scales of minutes to hours and days. Several unusual features were found in the X-ray light curve of V1494 Aql. After the expanding shell had become transparent to the soft X-ray radiation from the white dwarf, V1494 Aql was observed on days 300 and 303, when hydrogen burning was still going on, in two segments of 8 and 17 ks, respectively, using the LETG+HRC-S on Chandra (Drake et...

Hydrogenburning outbursts and critical heliumlayer masses

Giannone & Weigert, 1967 Starrfield, Sparks & Truran, 1974a,b), just one cycle was followed prior to a hydrogen-burning thermonuclear outburst. Paczynski and Zytkow (1978) followed the development of several successive flashes for a range of mass-accretion rates, showing that outburst strength increases with each cycle. They also identified mass-accretion rates that lead to steady state hydrogen burning at high surface temperatures. In their work, and in similar...

Meaning Of Lfr And Cfr In Novae

The region around the Mg II h + k lines for two models with Jf 10 000 K (upper panel) and Tf 15 000 K (lower panel). The dotted curves give the spectrum obtained if line blanketing by Fe II lines is neglected the full curves give the synthetic spectra including FeII line blanketing in addition to the Mg II lines. The significant change in the Mg II h + k line profiles due to overlapping Fe II lines is very apparent in this plot and demonstrates the importance of a proper treatment of...

Spectral evolution during eruption

There is a wealth of literature on the dramatic changes that take place in the spectra of novae from maximum down to eventual quiescence. Modern analyses continue to refer to the various taxonomic classes that were first introduced by McLaughlin (1942, 1944) and emphasized by Payne-Gaposchkin (1957), but there is now also a modern classification scheme for the emission line evolution which is more physically based (Williams, 1990, 1992). It remains an extraordinary fact that despite the...

A zerothorder model for CV evolution

Assuming that the mass of a typical white dwarf component is and remains constant at 1M and that the birthrate of CVs is independent of the initial mass of the donor for initial donor mass Md < 1.54 M , a simple but illustrative model of CV evolution can be constructed (Iben, Fujimoto & MacDonald, 1992a). This model makes use of results described in Section 3.6. 3.4.1 CV number density versus mean accretion rate At time t, let n(Md, t) dMd be the number in the entire Galaxy of CVs for...

Preface to the first edition

Some years ago we blundered, almost by accident, into the field of classical novae. Our prime interest at the time was in their dust formation properties and infrared development however, it soon became evident that a full understanding of this relatively restricted aspect of the nova outburst could not be achieved without considering all aspects of the nova phenomenon. Fortunately, from our point of view, the 1970s was a decade during which several significant advances were made in the...

Light curves during eruption

Example Novae Light Curves

Modern studies of nova light curves still depend largely on the descriptions introduced 50 or more years ago. Almost all novae rise rapidly (1-3 d) and are not then sufficiently well observed to warrant division into types. To quantify the very different rates of decline from maximum light, Payne-Gaposchkin (1957) introduced the 'speed classes' listed in Table 2.2 (where it will be noted that there are no 'normal' novae, they are either fast or slow cf. dwarf and giant stars). The notation tn...

Frequency and Galactic distribution of novae

The frequency of classical nova discoveries over the past century, corrected for non-uniformity of coverage in time, is shown in Table 2.1 (Duerbeck, 1990). In the range 4 < mV < 6 the values do not increase as fast as expected, showing that many bright novae go undetected. At fainter magnitudes the increase is due to the contribution of novae in the Galactic bulge. The total mean detected nova rate is 3 yr-1. There are so many factors that lead to incompleteness in nova searches (seasonal,...

Novae as distance indicators

Given both their high outburst luminosities ( 7 > MV > 9), which make them among the most luminous objects in the cosmos, and their frequent outbursts (30yr 1 in a typical spiral galaxy like the Milky Way Shafter, 2002), novae are of obvious interest as extragalactic distance indicators (de Vaucouleurs, 1978 van den Bergh, 1981 van den Bergh & Pritchet, 1986 Jacoby et al., 1992 Livio, 1992 Della Valle & Livio, 1995 Livio, 1997 Gilmozzi & Della Valle, 2003). In addition to being up...

Wavelength In Microns

The NeII 12.8 m forbidden line in the spectrum of QU Vul on day 140 was the strongest such line relative to the continuum ever observed in an astrophysical source. From Gehrz, Grasdalen and Hackwell (1985). Fig. 8.6. The Ne vi X7.6 m forbidden line in the spectrum of V1974 Cyg on day 264. Note that Ne ii X12.8 m is barely detectable at this stage. From Gehrz et al. (1994). Fig. 8.6. The Ne vi X7.6 m forbidden line in the spectrum of V1974 Cyg on day 264. Note that Ne ii X12.8 m is...

Relationships among amplitude rate of decline absolute magnitude and expansion velocity

The most direct correlation of nova properties, independent of distance and reddening, is that of amplitude of eruption versus tn. For both parameters there can be problems of measurement, especially for the fainter novae tn requires good photometric coverage of the maximum stages (and the maximum itself may often be missed, even for the brightest novae), and the amplitude (or range) of eruption, A mmin - mmax, can only be measured if and when the nova has settled down as an identifiable...

Relationship of classical novae to supernovae of Type Ia

Supernovae of Type Ia (SNe Ia) are those supernovae in which neither hydrogen nor helium is seen in any spectra obtained during the outburst. They have similar light curves, which can be further calibrated (Phillips, 1993), making them excellent standard candles to redshift z > 1 (Filippenko, 1997). Thus, they have become extremely important because they can be used to determine the structure and evolution of the Universe (Leibundgut, 2000, 2001, and references therein). Supernovae Ia are...

Mean mass transfer rates in CVs and symbiotic stars

The first order of business is an estimate of long-term, time-averaged, mass-transfer rates. We bypass the complications associated with the formation of an accretion disk and of the dwarf-nova discharges of this disk, focusing exclusively on the accretion rate averaged over many classical nova-producing cycles. 3.3.1 Mass transfer driven by a magnetic stellar wind The development here follows that of Tutukov (1983 see also Iben & Tutukov, 1984b Iben, Fujimoto & MacDonald, 1992a). The...

Radio imagery

With reference to Figure 12.1, a typical nova can theoretically be resolved by a radio array such as MERLIN whilst still on the optically thick, rising part of the radio light curve. From a simple model of radio evolution given in Chapter 7, we can derive equations for the peak flux, angular size at peak and time to peak. Thus typically, 1 yr after outburst, at the time of maximum in the radio light curve, the surface brightness at 5 GHz, S5 300 Jy per beam with MERLIN (cf. 50 Jy per beam...

References

Baade, W., 1929, Inaugural lecture, Hamburg, Jan. 30, 1929, quoted by D. E. Osterbrock (2001), Walter Baade. Princeton Princeton University Press, p. 57. Baade, W., & Zwicky, F., 1934, PNAS, 20, 254. Bertaud, C., 1951, Ann. Astrophys., 14, 199. Biermann, L., 1939, Z. Astrophys., 18, 344. Biot, E., 1843a, Catalogue des cometes observ es en Chine depuis l'an 1230jusqu' l'an 1640 de notre re (extrait du supplement du Wen-hian-thoung-khao, et de la grande Collection des vingt-cinq historiens de...

GK Persei

There are several remarkable features associated with GK Per that make it distinct and worthy of individual attention. It may provide a valuable insight not only into the evolution of nova binary systems, but also into the physics of supernova remnants and planetary nebulae. The nova outburst in February 1901 was accompanied some months later by rapidly expanding nebulosities on arcminute size scales (Ritchey, 1901). Couderc (1939) was the first to formulate detailed models of these...

Novae and related stars

In the General Catalogue of Variable Stars Kholopov, 1985 , the novae split into three hardly used groups according to speed class are counted among the cataclysmic variables. Other types in this category are the novalike stars, the recurrent novae, the supernovae Types I and II , the U Gem stars subdivided into SS Cyg, SU UMa and Z Cam stars , and finally the Z And or symbiotic stars. It was already mentioned that in the beginning of variable star research, novae formed a class of their own,...

H2 H H H H

Reactions of this type result from collisional excitation of the vibrational ladder, leading to excitation into the vibrational continuum. As a result they are highly sensitive to both the density and the temperature. A severely limiting factor in the calculations is our extremely poor comprehension of the photoreaction cross-sections reaction rates. Also, unlike the 'cold' assumption made in interstellar chemical calculations, the issue is further complicated by the fact that the molecules are...

Remarks on CVs and symbiotic stars as Type Ia supernova precursors

Assuming that a Type Ia supernova is an exploding CO white dwarf, the question is can the accretor in a CV or symbiotic star retain and convert into carbon and oxygen enough matter to reach the critical CO core mass of 1.37 M Since the maximum initial mass of a CO white dwarf is 1.1 M , the question becomes, can 0.27 M of hydrogen-rich material be retained In the case of CVs, there is direct observational evidence that much of the accreted mass is lost in consequence of a combination of...