2.5 Summary
In this Chapter, we outlined the tools needed to reduce and analyse spectroscopic data, with special emphasis in the MagE spectrograph. We have shown the benefits of using the indirect imaging technique, Doppler tomography, and presented new methods to exploit these advan- tages to dynamically constraint CBs parameters. We have also presented a review of more classic methods and introduced the bootstrap as a reliable method to estimate uncertainties.
Three
Emission Line Tomography of the Short
Period Cataclysmic Variables CC Scl
and V2051 Oph
This Chapter is based on:
“Emission line tomography of the short period cataclysmic variables CC Scl and V2051 Oph”
P. Longa-Pena; D. Steeghs; T. Marsh
Monthly Notices of the Royal Astronomical Society 2014, 447 (3): p149-159
CC Scl and V2051 Oph were the first test subjects of the methods described in Chapter 2. In this Chapter, we present time resolved spectra of CC Scl and V2051 Oph obtained with MagE. In Section 3.3.3 we derive dynamical constraints on the radial velocities of the system compo- nents to estimate the mass ratio (q) of these two short period CVs. We present the first results of our method to estimate the value of the phase zeroΦ0,K1,Kem and hence to constrain the value ofq by calculating a K-correction. Furthermore, we used a variation from the Doppler to- mography secondary emission method, to constrain the value of the systemic velocityγ(Section 2.4). We also use the traditional methods of radial velocity determination, double Gaussian fit and diagnostic diagrams of the disc lines (Section 3.3.2) and present the performance of these methods for different lines against the Doppler map-based techniques.
3.1 Introduction
CC Scl was independently discovered as the ROSAT source 1RXS J2315532.3-304855 (Schwope et al., 2000) and in the Edinburgh-Cape Blue Object Survey as EC 23128-3105 (Chen et al. (2001)). From time resolved spectroscopy, Chen et al. derived an orbital period of 0.0584(2)d,K1=35±
66 CHAPTER 3. EMISSION LINE TOMOGRAPHY OF CC SCL AND V2051 OPH
10 km/s and 0.06<q<0.09. They also reported a possibly transient feature resembling an eclipse present in some of their photometric light curves. This feature was also reported by Tappert, Augusteijn, & Maza (2004).
Ishioka et al. (2001a) presented a significant amount of photometry covering a six-month baseline, finding superhumps and classifying CC Scl as a SU UMa type dwarf nova. They de- tected a super hump period of 0.078 d, which is 30% larger than the orbital period. This would be the largest fractional superhump excess in a SU UMa type followed by the 7.7% excess ob- served in TU Men. During an outburst in November 2011, Woudt et al. (2012) attempted to re- fine the orbital period photometrically, proposingPor b=0.00450801(6)d. They also identified a periodicity of 389.49 s that was associated with the WD spin period and would classify CC Scl as a super-humping intermediate polar below the period gap.
Recently, Kato (2014) have confirmed CC Scl as an eclipsing system. They presented a light curve showing a brief and shallow eclipse that was used to further refine the ephemeris and determine an accurate orbital period of the system (B J D)=2456668.00638(9)+0.058567233(8)E. The period proposed by Woudt et al. (2012) is inconsistent with the eclipse period. The period- icity detected by Wouldt et al. (2012) was most likely not the orbital period, since they observed the system during outburst.
V2051 Oph was discovered by Sanduleak (1972). It is classified as an eclipsing SU Uma type CV. Kiyota & Kato (1998) confirmed this classification, using the photometric detection of superhumps in the light curve of V2051 Oph during outburst.
Baptista et al. (1998) used ground-based high-speed eclipse photometry and HST spec- troscopy to derive the binary geometry and to estimate the masses. They reported a mass ratio of
q=0.19±0.03, an inclination ofi=83o±2oand the respective masses to beM1=0.78±0.06M¯ andM2=0.15±0.03M¯. Their photometric model would result in a projected radial velocity for the white dwarf ofK1=83±12 km/s while the secondary would move withK2=436±11 km/s.
ThisK1value is in excellent agreement with radial velocity analysis by Papadaki et al. (2008), who
findK1=84.89±12.22 km/s.
Another remark about V2051 Oph is its accretion disc asymmetry, as suggested by the eclipse mapping from Saito & Baptista (2006) and Baptista et al. (2007). This asymmetry is also found in the spectra of Steeghs et al. (2001).
Without a detection of the secondary star or a fortuitous inclination that leads to eclipses, it is difficult to derive robust binary parameters for many short period CVs. Nearly all the con- straints of orbital parameters of non eclipsing systems are limited to the study of the Balmer emission lines. The, until recently neglected, Ca II triplet, however, has proven to be an aus- picious candidate for orbital parameter constraints as shown by van Spaandonk et al. (2010). Despite the relative weakness of the Ca II triplet with respect to the Balmer lines, it is commonly found in short period CVs and can be used to track the secondary star better than the Balmer