Cataclysmic variables from the Calan Tololo Survey II Spectroscopic periods

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(1)Mon. Not. R. Astron. Soc. 405, 621–637 (2010). doi:10.1111/j.1365-2966.2010.16487.x. Cataclysmic variables from the Calán–Tololo Survey – II. Spectroscopic periods T. Augusteijn,1 C. Tappert,2 T. Dall3 and J. Maza4 1 Nordic. Optical Telescope, Apartado 474, E-38700 Santa Cruz de La Palma, Spain de Astronomı́a y Astrofı́sica, Pontificia Universidad Católica, Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago, Chile 3 ESO, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München, Germany 4 Departamento de Astronomı́a, Universidad de Chile, Casilla 36-D, Santiago, Chile 2 Departamento. ABSTRACT. In this second paper on cataclysmic variables detected in the Calán–Tololo Survey we present time-resolved spectroscopy for the remaining eight systems without a measured orbital period. We derive orbital periods for all of these systems, where we find two objects with periods above the period gap and six systems with periods shorter than 2 h. We discuss the spectroscopic results and do not find any specific general reason why the period could not be determined from photometry. This does imply that to study the period distribution of a large sample of cataclysmic variables phase-resolved spectroscopy is required. We also looked at the general results for the cataclysmic variables in the Calán–Tololo Survey (CTS). Our main objective was to search for the (very) short-period cataclysmic variables that population-synthesis models indicate are missing from the observed sample. However, we find that the sample of cataclysmic variables detected in the CTS is not fundamentally different from the known sample and does not provide an explanation for the discrepancy between population-synthesis models and the observed sample. Key words: surveys – binaries: close – stars: dwarf novae – novae, cataclysmic variables.. 1 I N T RO D U C T I O N Cataclysmic variables (CVs) are close interacting binary systems in which a late-type star transfers matter via Roche lobe overflow on to a white dwarf. CVs are thought to evolve from wide, detached, binary stars. In the course of its nuclear evolution, the more massive star in these binaries expands, and transfer of its material at a high rate results in the binary entering a common-envelope configuration. Due to friction the binary components spiral-in towards each other. After the expulsion of the common envelope, the separation between the remaining white dwarf and the largely unaltered secondary star is decreased further by angular momentum loss via magnetic braking and/or gravitational radiation. As the orbital separation decreases the secondary will start to fill its Roche lobe and mass transfer will commence while the rate at which the separation decreases is diminished since the transfer of mass on to the primary will tend to increase the separation of the two components. For a comprehensive overview on CVs and their evolution see Warner (1995). The observed period distribution of CVs represents the principle test-bed for evolutionary models. Two striking features in the period distribution are a significant lack of systems in the period range. E-mail: [email protected] C. C 2010 RAS 2010 The Authors. Journal compilation . ∼2–3 h (the ‘period gap’), and a sharp cut-off in the distribution at ∼76 min (e.g. Knigge 2006). The period gap is usually explained by the ‘disrupted magnetic braking’ hypothesis which poses that the magnetic braking of the secondary star becomes inefficient as a source of angular momentum loss due to internal restructuring of the star as it becomes fully convective (Rappaport, Verbunt & Joss 1983; Spruit & Ritter 1983; Verbunt 1984; Taam & Spruit 1989). As a consequence, the time-scale of Roche lobe shrinkage – now mainly powered by the less efficient gravitational radiation – becomes longer than the time-scale of thermal adjustment, thus letting the secondary star contract to its thermal equilibrium size and detach from its Roche lobe and mass transfer ceases. This is thought to occur at the high-period end of the period gap and the CV evolves as a detached system through the period gap until gravitational radiation brings the Roche lobe back into contact with the stellar surface at the low-period end of the period gap. At this point mass transfer recommences, now at a much lower rate. The period minimum is explained by the continuous mass-loss causing the nuclear burning in the secondary to extinguish. The star will evolve to a degenerate state in which its size increases with decreasing mass and the system will evolve through a minimum in its orbital period (Paczynski & Sienkiewicz 1981; Rappaport, Joss & Webbink 1982). The latest theoretical models predict the minimum orbital period to be ∼ =70 min (Kolb & Baraffe 1999).. Downloaded from http://mnras.oxfordjournals.org/ at Pontificia Universidad CatÃ¯Â¿Â½lica de Chile on May 19, 2016. Accepted 2010 February 4. Received 2010 February 1; in original form 2009 September 30.

(2) 622. T. Augusteijn et al. orbital period we presented in the first paper (Tappert, Augusteijn & Maza 2004, hereafter Paper I) those six CVs whose light curves are modulated with the orbital period, and thus allowed us to derive this parameter by photometric means. In this paper we present time-resolved spectroscopy of the remaining eight systems with unknown period, including the known dwarf nova AG Hya. There are also several other surveys that in recent years have made significant contribution to the period distribution, e.g. the Hamburg–Quasar Survey (HQS; Gänsicke, Hagen & Engels 2002) and the Sloan Digital Sky Survey (Szkody et al. 2002, 2003, 2004, 2005). However, it should be noted that any such surveys are limited in representing the intrinsic population of CVs as provided by a volume-limited sample where one does not need to take the magnitude limit into account (see Pretorius et al. 2007). We discuss the results for the newly discovered CVs detected in the CTS, with an emphasis on why for the specific sources presented in this paper no well-defined photometric periods were found. We conclude with a discussion of the overall sample of sources detected in the CTS compared to the general sample of CVs. 2 DATA A N D A N A LY S I S Follow-up observations on the sample were conducted over a number of years on several telescopes, mostly situated at the La Silla Observatory of the European Southern Observatory (ESO). Fluxcalibrated spectra to secure the CV classification of the candidates were usually taken with DFOSC at the 1.54-m Danish telescope, and photometric light curves at the 90-cm Dutch telescope. Timeresolved spectroscopic data to determine the orbital period were obtained either at the 1.54-m Danish telescope or at the ESO 3.6-m telescope. See Table 1 for respective instrumental configurations. Data reduction was performed in the usual way, using IRAF routines for bias subtraction and flat-fielding. Differential light curves for the photometric data were established with respect to several suitable comparison stars. Calibrated magnitudes were computed by comparison to previously taken BVR photometry. The timeresolved spectroscopic data usually were not flux calibrated. In these cases, the brightness state of the star during the observations was determined by performing photometry on the acquisition frames, if available, and subsequent comparison with the calibrated data. Table 2 gives a summary of the observations. After the extraction and the wavelength calibration of the timeresolved spectra, the radial velocities of the Hα emission line were measured by fitting a single Gaussian profile. To analyse the radial velocities we used the method described by Scargle Scargle (1982) as implemented in MIDAS to search for periodic variations. An important point to take into account when analysing the data is that ‘FOSC’-like spectrographs as used in our observations (see Table 1) have the property that if the target moves perpendicular to the slit the whole spectrum moves in the dispersion (i.e. velocity) direction. Already the precise centring of the star can have an effect. As the resolution that is used is typically a few ×100 km s−1 this can have a significant effect. In general one would not expect these movements to affect the detection of any periodic variations much, but they can easily explain differences in systemic velocity between different observations or linear trends in the data from a single night which can affect the value for the best period as defined from a periodogram. Furthermore, the periodogram does not provide any statistical error estimate. For the above reasons we only take the period as indicated by the periodogram as a basis for a further analysis. This value for the period is then used for a full least-squares sinusoidal fit to the data C. C 2010 RAS, MNRAS 405, 621–637 2010 The Authors. Journal compilation . Downloaded from http://mnras.oxfordjournals.org/ at Pontificia Universidad CatÃ¯Â¿Â½lica de Chile on May 19, 2016. Models of the intrinsic population of CVs and of the expected observable population (e.g. Kolb 1993; Howell, Rappaport & Politano 1997; Stehle, Kolb & Ritter 1997) show significant discrepancies with respect to the actually observed population. Perhaps the most obvious ones of those are (i) the predicted period minimum is too short by several minutes; (ii) the significant increase of the evolutionary time-scales when a CV evolves past the minimum period should cause a pile-up of systems at the period minimum that is not observed in the period distribution of all known CVs (see, however, Gänsicke et al. 2009); (iii) only ∼50 per cent of the known CVs have periods below the gap (Ritter & Kolb 2003) as opposed to the predicted 99 per cent and (iv) the observed space density is a factor of 10–100 lower than expected (Patterson 1984; de Kool 1992; Kolb 1993; Ringwald 1996). Many of these discrepancies could in principle be due to the relatively bright magnitude cut-off of the sample of known CVs, which leads to a strong bias towards systems with high mass-transfer rates. One of the main effects of this is that the known sample of CVs is dominated by relatively distant, long-period systems while all studies indicate that the intrinsic population is dominated by (short-period) low mass transfer, and therefore intrinsically very faint CVs. Starting in 1996, we have conducted a survey of candidate CVs found in the Calán–Tololo Survey (CTS; Maza et al. 1989, and references therein). The CTS is an objective prism survey originally designed to search for emission-line galaxies, quasars and galaxies with strong ultraviolet excess using objective prism plates. The spectra cover the wavelength range from ∼5300 Å down to the atmospheric cut-off. The typical limiting magnitude of the plates is BJ ≈ 18.5, and the survey covers roughly 5150 deg2 , i.e. 1/8 of the whole sky, in the Southern hemisphere at Galactic latitudes |b| ≥ 20◦ . Our objective in searching for CVs in this survey is that by looking at high galactic latitudes the survey specifically limits the bias towards relatively bright, distant sources while it also should remove any potential bias due to crowding and extinction, which should provide a better way to look for those sources apparently missed in the observed sample of CVs. Surveys like the CTS are also especially suited as the low mass-transfer (in principle dwarf nova type) CVs that are predicted to dominate the intrinsic population and are apparently missing are expected to have a blue continuum and strong hydrogen emission lines (see e.g. fig. 6 in Patterson 1984). We note that results from the sample of CVs from the Sloan Digital Sky Survey (Gänsicke et al. 2009) seem to indicate that the strength of the hydrogen emission lines as measured by their equivalent width decreases again when going to very low mass-transfer rates (which might very well be because for those sources the spectra are dominated by emission from the white dwarf outshining the continuum from the accretion disc, effectively reducing the measured equivalent width). At the start of our survey in 1996 about half of the CTS plates had been searched, giving a sample of 59 candidate CVs. Followup observations confirmed 21 to be CVs, of which five were already known (AG Hya, RX J1007.5−2017, V436 Cen, LY Hya and QS Tel) and a further four (CM Phe, V1043 Cen, 1RXS J205652.1−301433 and CC Scl) have been independently discovered by other surveys in the meantime (Tappert, Augusteijn & Maza 2002). Of the 21 CVs, three systems (V436 Cen, LY Hya and QS Tel) had already a measured orbital period, while for four systems (CM Phe, 1RXS J205652.1−301433, TU Crt and V1043 Cen) the period has been measured by other authors (see for all the listed systems Table B1 for details). For the systems without a measured.

(3) CVs from the Calán–Tololo Survey – II.. 623. Table 1. Instrumental configurations. The spectral resolution refers to the full width at half-maximum (FWHM) at Hα. Telescope. Instrument. Grism/filter. Slit (arcsec). Range (Å). Resolution (Å). 1996-04 1996-04 1996-08 1996-10 1996-10 1997-04 1997-05 1998-05 2001-08 2002-07 2004-11 2005-02. 1.54 Danish 0.9 Dutch 2.2 MPI/ESO 0.9 Dutch 1.54 Danish 2.2 MPI/ESO 0.9 Dutch 1.54 Danish 1.54 Danish 3.6 ESO 3.6 ESO 3.6 ESO. DFOSC CCD EFOSC2 CCD DFOSC EFOSC2 CCD DFOSC DFOSC EFOSC2 EFOSC2 EFOSC2. 11 V 1 V 11 1 V 7 7 10 10 10. 1.0 – 1.0 – 1.5 1.0 – 1.5 1.5 1.0 1.0 1.0. 4400–9700 – 3800–9400 – 4400–9700 3800–9400 – 3800–6800 3800–6800 6300–8100 6300–8100 6300–8100. 13 – 30 – 16 28 – 5.1 5.1 5.6 5.3 5.3. Table 2. Log of observations. ndata gives the number of data points, texp the individual exposure time, t the time interval covered by the observations and Vav the average magnitude during the run. In the case of spectroscopic observations, the latter was determined from the target acquisition frames. CTCV. RA (J2000). Dec. (J2000). Date. HJD. Configuration. ndata. texp (s). t (h). V av. J0006−6900. 00 06 33.37. −69 00 33.2. J0333−4451. 03 33 20.58. −44 51 41.8. AG Hya. 09 50 29.85. −23 45 17.7. J1057−2156. 10 57 49.81. −21 56 58.0. J1226−2527. 12 26 17.37. −25 27 04.5. J1940−4724. 19 40 37.63. −47 24 48.8. J2056−3014. 20 56 52.04. −30 14 38.2. J2118−3412. 21 18 04.28. −34 13 42.8. 1996-10-05 1996-10-09 2001-08-29 2002-07-06 1996-10-01 1996-10-04 1996-10-09 2001-08-27 2001-08-28 2001-08-29 2001-08-30 2001-08-31 2002-07-07 2002-07-08 2004-11-17 2004-11-18 2005-02-15 1997-04-29 1997-05-01 1997-05-07 2005-02-16 2005-02-17 1996-04-13 1996-04-25 1997-05-06 2005-02-16 2005-02-17 1996-04-23 1996-04-28 1996-08-02 1998-05-31 1996-10-02 1996-10-09 2001-08-28 2002-07-07 1996-10-04 1996-10-09 1997-05-06 1997-05-07 1998-05-31. 245 0362 245 0366 245 2151 245 2462 245 0358 245 0361 245 0366 245 2149 245 2150 245 2151 245 2152 245 2153 245 2463 245 2464 245 3327 245 3328 245 3417 245 0568 245 0570 245 0576 245 3418 245 3419 245 0187 245 0199 245 0575 245 3418 245 3419 245 0197 245 0202 245 0298 245 0965 245 0359 245 0366 245 2150 245 2463 245 0361 245 0366 245 0575 245 0576 245 0965. D90/V 1.54D/11/1.5 1.54D/7/1.5 3.6/10/1.0 D90/V D90/V 1.54D/11/1.5 1.54D/7/1.5 1.54D/7/1.5 1.54D/7/1.5 1.54D/7/1.5 1.54D/7/1.5 3.6/10/1.0 3.6/10/1.0 3.6/10/1.0 3.6/10/1.0 3.6/10/1.0 2.2/1/1.0 D90/V D90/V 3.6/10/1.0 3.6/10/1.0 1.54D/11/1.0 D90/V D90/V 3.6/10/1.0 3.6/10/1.0 D90/V D90/V 2.2/1/1.0 1.54D/7/1.5 D90/V 1.54D/11/1.5 1.54D/7/1.5 3.6/10/1.0 D90/V 1.54D/11/1.5 D90/V D90/V 1.54D/7/1.5. 202 1 33 100 95 31 1 11 7 13 5 13 11 35 16 15 45 1 164 162 25 5 1 78 127 18 36 63 122 1 18 204 1 50 81 125 1 223 133 41. 45 2580 300–400 60–90 120 90 2700 300 400 400 600 500 240 240 600 600 600 420 60 90/120 600 600 1800 180/210 90 600 600 120 60/120 180 500 45 1200 300 90/180 60 900 30 30 240. 3.01 – 4.50 3.30 4.02 1.02 – 1.30 1.00 3.76 1.26 2.83 0.81 2.72 2.67 2.50 8.13 – 4.24 5.95 4.44 0.71 – 5.17 4.18 3.10 6.77 3.08 4.18 – 2.70 4.46 – 5.42 3.11 3.21 – 3.69 2.26 3.37. 15.3 15.9 – 15.8a 17.8 17.8 17.3 – – – – – 17.9a 18.5a – – – 17.7a 17.8 17.9 18.5 18.7 18.2 18.1 16.9 18.1 18.7 15.0 16.6 13.9 17.0 16.6 15.2 – 16.4a 16.4 16.4 15.5 15.5 16.2. aV. C. magnitude estimated using an average V − R value.. C 2010 RAS, MNRAS 405, 621–637 2010 The Authors. Journal compilation . Downloaded from http://mnras.oxfordjournals.org/ at Pontificia Universidad CatÃ¯Â¿Â½lica de Chile on May 19, 2016. Date.

(4) 624. T. Augusteijn et al.. in each observing night with sufficient data. This provides welldefined values and error estimates for the period, systemic velocity, radial-velocity amplitude and the time of superior conjunction (T sup ) for the emission line. In all cases the times of superior conjunction given in the paper correspond to times that the target was truly observed, which in some cases means that the T sup given is not close to the average time of the observations. However, in this way the times of superior conjunction should always be a good estimate even if the period used is not correct. 3 R E S U LT S. Figure 2. Periodogram of the radial-velocity measurements of CTCV J0006−6900 taken on 2001 August 29 (top) and 2002 July 6 (bottom).. 3.1 CTCV J0006−6900 The low-resolution spectrum of CTCV J0006−6900 is presented in Fig. 1. Time-resolved spectroscopy of CTCV J0006−6900 consists of observation taken on two nights nearly one year apart. The periodogram for each night presented in Fig. 2 show a clear signal at a frequency of ∼13 cycles d−1 . From a least-squares sinusoidal fit to the data from each night (shown as the drawn lines in Fig. 3) we derive periods of 0.0723(30) d (data from 2001 August 29) and 0.0803(14) d (2002 July 6), which are consistent within 3σ . Consistent results are also obtained for the radial-velocity amplitudes, 87(17) and 107(6) km s−1 , and the systemic velocities, 2(13) and 16(4) km s−1 , respectively. From this we conclude that the source has a stable periodic radial-velocity variation which we identify with the orbital period of the system. The T sup values for the emission line as derived from the fits are HJD 245 2151.6070(23) and 245 2462.906 53(68), respectively. The time-span between these times is too long to maintain the cycle count and derive an ephemeris. As a best period estimate we take the error-weighted mean of the periods derived for each night, which corresponds to Porb = 0.0790(12) d.. Figure 3. The radial velocities for the CTCV J0006−6900 data from 2001 August 29 (top) and 2002 July 6 (bottom). The solid curves in both plots give the best fit to each data set separately (see text).. Figure 4. Photometric light curve for CTCV J0006−6900 from 1996 October 5. The bar at the top gives the length of the spectroscopic period.. The high radial-velocity amplitude found for this source indicates that this source has a relatively high orbital inclination (see Section 4). The radial-velocity curves, presented in Fig. 3, do show distortions close to the phase of superior conjunction which might indicate the presence of a so-called rotational disturbance caused by the partial eclipse of an accretion disc. The light curve of the photometric observations presented in Fig. 4 shows a strong variation with an amplitude of V ∼ 0.6 mag which one would expect for a high-inclination source. However, during these observations the brightness apparently varies on a timescale significantly longer than the spectroscopic period. From our. Figure 1. Low-resolution spectrum of CTCV J0006−6900 (see Table 2 for details). C. C 2010 RAS, MNRAS 405, 621–637 2010 The Authors. Journal compilation . Downloaded from http://mnras.oxfordjournals.org/ at Pontificia Universidad CatÃ¯Â¿Â½lica de Chile on May 19, 2016. We have collected plots of Hα line profiles from the time-resolved spectra, and a table presents the equivalent widths of the most important emission lines for all obtained spectra (i.e. flux-calibrated as well as average spectra from the time-resolved data) in Appendix A. With the exception of AG Hya, all systems show the strong H and He I emission lines that are indicative of low mass-transfer systems. Other lines include He II λ4686, Fe II λ5173 and the O I triplet at λ7773. In Appendix B we give an overview of all CVs identified in our sample of candidate CVs from the CTS. In Appendix C we present finding charts for the previously unknown CVs presented in this paper..

(5) CVs from the Calán–Tololo Survey – II.. 625. Figure 7. The radial velocities for the CTCV J0333−4451 data from 2001 August (top) and 2002 July (bottom) folded at the most likely period (see text). The solid curves give the best fit for each data set separately (see text). Figure 6. Periodogram of the radial-velocity measurements of CTCV J0333−4451.. time coverage it is not clear if this variation is of periodic or irregular nature. We do note that the source was somewhat brighter during the photometric observations (see Table 2) and there seems to be a rising trend in the data which might indicate some kind of (low-amplitude) outburst which could have affected or masked an underlying orbital brightness variation. We also note that CTCV J0006−6900 likely can be identified with the variable AN 97.1933 discovered by Luyten (1933) from a plate survey of the southern sky. For this variable a brightness range of B ∼ 14.5–16.5 mag is reported, which indicates relatively small amplitude outbursts which is also consistent with the high inclination estimated for this source (see Section 4). The source was also detected on various occasions in a bright state by the All Sky Automated Survey (ASAS; Pojmanski 2002).1 3.2 CTCV J0333−4451 The low-resolution spectrum of CTCV J0333−4451 is presented in Fig. 5. Time-resolved spectroscopy of CTCV J0333−4451 consists of observations spread over seven nights in two consecutive years. The periodogram of all the data presented in Fig. 6 shows a very nice rather symmetric set of peaks caused by the window function of the observations centred on 15.9 cycles d−1 which we consider the most likely period. Although the overall distribution of the peaks argues against the peak at 16.9 cycles d−1 being the true period, it is only slightly lower than the peak at 15.9 cycles d−1 and we cannot exclude it as a significant alternative. Using a start period of 0.062 84 d we derive for the set of observations in each year from a least-squares sinusoidal fit (shown as the solid lines in Fig. 7) periods of 0.062 826(65) d (data from 2001 August) and 0.063 07(15) d (2002 July), which are consistent within 3σ . Also, consistent results are obtained for the radial-velocity 1 See. C. also http://www.astrouw.edu.pl/asas/. C 2010 RAS, MNRAS 405, 621–637 2010 The Authors. Journal compilation . Figure 8. Photometric light curve for CTCV J0333−4451 from 1996 October 1. The bars at the top and bottom correspond to the length of the two possible spectroscopic periods.. amplitudes, 74(11) and 67(6) km s−1 , and the systemic velocities, −5(8) and 21(5) km s−1 , respectively. From this we conclude that the source has a stable periodic radial-velocity variation which we identify with the orbital period of the system. The T sup values as derived from the fits are HJD 245 2151.9128(15) and 245 2464.893 13(99), respectively. The time-span between these times is too long to maintain the cycle count and derive an ephemeris. As a best period estimate we take the error-weighted mean of the periods derived for each data set, which corresponds to Porb = 0.062 864(60) d. Alternatively, assuming that the peak in the periodogram at 16.9 cycles d−1 corresponds to the true period we derive an error-weighted average period of 0.059 123(57) d. The values for radial-velocity amplitudes, the systemic velocities and the times of superior conjunction for the two data sets are within the errors the same as those derived for the most likely period. Brightness variations at neither of the proposed periods are obvious in the photometric observations presented in Fig. 8 which is characterized by strong, short-term variations with amplitudes up to 0.4 mag. This ‘flickering’ behaviour is rather typical in CVs and likely masks any underlying periodic variation.. Downloaded from http://mnras.oxfordjournals.org/ at Pontificia Universidad CatÃ¯Â¿Â½lica de Chile on May 19, 2016. Figure 5. Low-resolution spectrum of CTCV J0333−4451 (see Table 2 for details)..

(6) 626. T. Augusteijn et al.. Figure 9. Periodogram of the radial-velocity measurements of CTCV J0950−2345 (= AG Hya).. The only previously known system without a determined orbital period in our survey is AG Hya (which has our internal designation CTCV J0950−2345). AG Hya was discovered as an SS Cyg type variable by Boyce (1936) on Harvard plates (HV 7591). It was later included as an SU UMa candidate by Petit (1960), but did not meet the stricter definition of this subgroup by Vogt (1980). The quiescence magnitude was measured to V = 19.17 by Szkody (1987), who also provides an optical spectrum. The latter has rather low signal-to-noise ratio (S/N), but still presents the typical characteristics of a dwarf nova in quiescence. Time-resolved spectroscopy of AG Hya consists of observations spread over three nights – two consecutive nights and a single night ∼3 months later (see Table 2). The periodogram of all the data presented in Fig. 9 shows a very nice, rather symmetric set of broad peaks caused by 1-d aliasing due to the window function of the observations centred on a frequency 4.2 cycles d−1 . We cannot choose between the many, more finely spaced peaks in the main peak (effectively filling up the area below the broad peak in Fig. 9) caused by the gap of ∼3 months in the data. Using a start period of 0.238 d we derive for each set of observations from a least-squares sinusoidal fit periods of 0.237 79(92) d (data from 2004 November) and 0.2386(59) d (2005 February), which are consistent within 3σ . Also, consistent results are obtained for the radial-velocity amplitudes, 74(4) and 61(4) km s−1 , and the systemic velocities, 6(4) and 11(3) km s−1 , respectively. From this we conclude that the source has a stable periodic radial-velocity variation which we identify with the orbital period of the system. The T sup values as derived from the fits are HJD 245 3327.8250(27) and 245 3417.6281(24), respectively. As a best period estimate we take the error-weighted mean of the periods derived for each data set, which corresponds to Porb = 0.237 81(91) d. The time-span between the T sup values of 89.8031(36) d does allow us to provide a more refined estimate of the orbital period. Taking the period for the 2004 November data, the time-span corresponds to 377.7 ± 1.5 cycles. Assuming a 3σ range in this value the precise period of this system is expected to be 89.8031(36)/N, where N is an integer in the range 374–382 (0.235 09–0.240 12 d), with the most likely period (N = 378) being 0.237 5743(95) d. Doing a fit to all the data with a fixed period of 0.237 5743 d, we derive for the radial-velocity amplitude 67(3) km s−1 and for the systemic velocity 8(2) km s−1 , with a T sup of HJD 245 3417.6281(17). All the radial-velocity measurements folded at the most likely period is shown together with the best fit at this period in Fig. 10.. sample. The long orbital period indicates that this is an intrinsically bright system so it must be far away and relatively high above the Galactic plane. For dwarf novae the absolute brightness in outburst follows a well-defined relation as a function of orbital period (see Warner 1987; Harrison et al. 2004). AG Hya has been very well monitored especially over the past ∼10 yr by the AAVSO2 which indicates a visual magnitude in outburst of 14.3 mag which is consistent with the magnitude in outburst as listed in Downes, Webbink & Shara (1997).3 For the orbital period of AG Hya we derive (see Harrison et al. 2004) an absolute magnitude in outburst of MV = 3.74 mag, which indicates a distance of 1290 pc. However, the apparent magnitude of the source depends strongly on the inclination (e.g. Warner 1987) and the orbital inclination of AG Hya is probably low (see discussion in Section 4). Assuming the radial-velocity amplitude derived above reflects the orbital motion of the accretion disc centred on the white dwarf, and assuming typical values for the mass of the white dwarf and the secondary we estimate an orbital inclination for the system of i ∼ 25◦ . Following Warner (1987) this implies a (admittedly uncertain) correction to the apparent magnitude of −0.83 mag and a corresponding revised distance estimate of 1900 pc. We have also explored the possibility to estimate the distance using the brightness of the system in quiescence. From the data presented in fig. 1 of Beuermann (2006) (see also Beuermann et al. 1998) a simple relation can be derived between the absolute K magnitude of a star and its radius which can be combined with the radius orbital period relation for the secondary star in CVs obtained by Smith & Dhillon (1998) to derive MK = 10.57 − 7.38 × log[Porb (h)],4 and it follows that log d (pc) = mK /5 − 1.11 + 1.48 × log Porb (h). Observations presented by Hoard et al. (2002) give a magnitude of AG Hya in quiescence of K = 15.08 mag which indicates a distance of 1060 pc. This distance should be considered as a lower limit as the magnitude in quiescence might be contaminated by emission, e.g. from the accretion disc, so it is roughly consistent with the estimate based on the brightness of the system in outburst. This indicates that the source is at a distance well in excess of 1 kpc, i.e. it is at a height above the galactic plane of z > 375 pc. The expected scaleheight for CVs with an orbital period above the period gap is about 120 pc (see e.g. Pretorius et al. 2 See. http://www.aavso.org/ Hya was also detected on various occasions (apparently) in outburst by the ASAS. 4 Note that this effectively assumes that the secondary in a CV has the same surface brightness as a main-sequence star with the same radius. 3 AG. 3.3.1 An old system An interesting thing to note is that AG Hya has such a long-period system while its apparent brightness is one of the lowest in our C. C 2010 RAS, MNRAS 405, 621–637 2010 The Authors. Journal compilation . Downloaded from http://mnras.oxfordjournals.org/ at Pontificia Universidad CatÃ¯Â¿Â½lica de Chile on May 19, 2016. Figure 10. The radial-velocity measurements of the CTCV J0950−2345 (= AG Hya) data from 2004 November 17 and 18 () and 2005 February 15 (+) folded at the most likely period of 0.237 5743 d. The solid curve in the plot gives the best fit at this period.. 3.3 CTCV J0950−2345 (= AG Hya).

(7) CVs from the Calán–Tololo Survey – II.. 627. 2007) so AG Hya might be a relatively old system belonging to the thick-disc population (see Gilmore, Wyse & Kuijken 1989, and references therein).. 3.4 CTCV J1057−2156. Figure 11. Low-resolution spectrum of CTCV J1057−2156 (see Table 2 for details).. Figure 13. The radial velocities for the J1057−2156 data from 2005 February 16. The solid curves in the plot give the best fit to the data.. Figure 14. Photometric light curves of CTCV J1057−2156 from 1997 May 1 (top) and 1997 May 7 (bottom). For orientation, several cycles of the spectroscopic period have been indicated by horizontal lines with arbitrary zero-points.. Figure 15. Low-resolution spectrum of CTCV J1226−2527 (see Table 2 for details).. (see Section 4) it is not surprising that there are no very obvious orbital brightness variations. We also note that CTCV J1057−2156 likely can be identified with the variable AN 683.1936 discovered by Luyten (1937) from a plate survey of the southern sky. For this variable a brightness range of B ∼ 14.5 to <15.5 mag is reported. The source was also detected on various occasions in the bright state by the ASAS. 3.5 CTCV J1226−2527. Figure 12. Periodogram of the radial-velocity measurements of CTCV J1057−2156 taken on 2005 February 16. C. C 2010 RAS, MNRAS 405, 621–637 2010 The Authors. Journal compilation . The low-resolution spectrum of CTCV J1226−2527 is presented in Fig. 15. Time-resolved spectroscopy of CTCV J1226−2527 consists of two sets of observations taken on consecutive nights. The. Downloaded from http://mnras.oxfordjournals.org/ at Pontificia Universidad CatÃ¯Â¿Â½lica de Chile on May 19, 2016. The low-resolution spectrum of CTCV J1057−2156 is presented in Fig. 11. Time-resolved spectroscopy of CTCV J1057−2156 consists of a set of 25 observations taken during a night (2005 February 16) over a period of 4.4 h, and five measurements taken over a period of 40 min in the subsequent night (2005 February 17). The periodogram of the data from the first night, presented in Fig. 12, shows a single peak at ∼14.3 cycles d−1 , i.e. 0.07 d. Using a start period of 0.07 d we derive from a least-squares sinusoidal fit to the data from the first night a period of 0.0699(18) d with a radial-velocity amplitude of 18.4(2.5) km s−1 , and a systemic velocity of 63(2) km s−1 . As there is no indication of any other period in the radial-velocity data, we identify this period with the orbital period of this system. The T sup as derived from the fit is HJD 245 3418.6173(14). The radial-velocity measurements taken on 2005 February 16 folded at the orbital period are shown together with the best fit at this period in Fig. 13. The radial-velocity data of the second night are consistent with the results found for the first night, and they imply a refined value for the orbital period of either 0.067 99 or 0.073 10 d. However, the data in that night covers less than half the orbital period, and a systematic shift or measurement error could affect this estimate significantly, and we prefer the somewhat more conservative estimate for the period based on the data from the first night alone. As for the photometry, there are clearly longer term slow variations. The data from 1997 May 1 presented in Fig. 1 seem to be more or less consistent with the orbital period, but the 1997 May 7 data are not. Considering that this is likely a low-inclination system.

(8) 628. T. Augusteijn et al.. Figure 16. Periodogram of the radial-velocity measurements of CTCV J1226−2527.. Figure 18. Photometric light curves for CTCV J1226−2527 from 1996 April 25 (top) and 1997 May 6 (bottom). Note that the y-axes have different zero-points. For orientation, the length of the spectroscopic period has been indicated in both plots using arbitrary zero-points.. Figure 19. Periodograms for the photometric data for CTCV J1226−2527 from 1996 April 25 (top) and 1997 May 6 (bottom). Prior to the computation of these periodograms the respective long-term trends in the light curves were removed.. & Kolb 2003) where there are many Z-Cam and VY-Scl type dwarf novae that vary in their average brightness. There are also various (suspected) intermediate polar (IP; see e.g.Warner 1995) type sources that show brightness variations with periods in the range of the short-term brightness variations seen in this source and the precise classification of CTCV J1226−2527 is not very clear.. 3.6 CTCV J1940−4724 Low-resolution spectra of CTCV J1940−4724 in outburst and quiescence are presented in Fig. 20. Time-resolved spectroscopy of CTCV J1940−4724 consists of a set of 18 observations taken during a single night. The periodogram of the data presented in Fig. 21 shows a single peak at ∼13 cycles d−1 , i.e. 0.08 d. From a least-squares sinusoidal fit to the data we derive a period of 0.0809(30) d with a radial-velocity amplitude of 72(7) km s−1 , and a systemic velocity of −34(5) km s−1 . The folded radial-velocity data together with the best-fitting radial-velocity curve is presented in Fig. 22. As there is no indication of any other period in the radialvelocity data, we identify this period with the orbital period of this system. The T sup as derived from the fit is HJD 245 0965.7495(13).. Figure 17. The radial-velocity measurements of the CTCV J1226−2527 data from 2005 February 16 (+) and 2005 February 17 () folded at the spectroscopic period. The solid curve in the plot gives the best fit at this period. C. C 2010 RAS, MNRAS 405, 621–637 2010 The Authors. Journal compilation . Downloaded from http://mnras.oxfordjournals.org/ at Pontificia Universidad CatÃ¯Â¿Â½lica de Chile on May 19, 2016. periodogram of all the data presented in Fig. 16 shows a very nice, rather symmetric set of peaks caused by the window function of the observations centred on 6.4 cycles d−1 . There is no indication of any other periodic variation. Using a start period of 0.155 d we derive for each night of observations from a least-squares sinusoidal fit periods of 0.132(11) d (data from 2005 February 16) and 0.1618(35) d (2005 February 17), which are consistent within 3σ . Also, consistent results are obtained for the radial-velocity amplitudes, 125(10) and 125(10) km s−1 , and the systemic velocities, −23(12) and −40(7) km s−1 , respectively. From this we conclude that the source has a stable periodic radial-velocity variation which we identify with the orbital period of the system. The T sup values as derived from the fits are HJD 245 3418.7932(16) and 245 3419.7193(18), respectively. The timespan between these times is 0.9261(24) d which, taking the period for the 2005 February 17 data, corresponds to 5.72 ± 0.12 cycles. Assuming a 3σ range in this value, the only possible solution is N = 6, and the period of this system is 0.154 35(40) d. Doing a fit to all the data with a fixed period of 0.154 35 d, we derive for the radial-velocity amplitude 120(8) km s−1 and for the systemic velocity −24(6) km s−1 , with a T sup of HJD 245 3419.7192(16). The radial-velocity measurements folded at this period are shown together with the best fit in Fig. 17. Time-resolved photometric observations were taken on two occasions (see Table 2). The light curves from these observations are presented in Fig. 18. There are no clear variations at the orbital period, but the photometric data show long-term brightness variations over a period of several hours on top of the short-term variations. The time-scale for the short-term variations is very different being ∼30 min in the measurements from 1996 April 25 and ∼49 min in the measurements from 1997 May 6 (see Fig. 19), while the average brightness of the source is different by more than a magnitude between these observations. The orbital period of CTCV J1226−2527 is in the range of the orbital period distribution of CVs (see Ritter.

(9) CVs from the Calán–Tololo Survey – II.. Figure 23. Photometric light curves for CTCV J1940−4724 from 1996 April 23 (top) and 1996 April 28 (bottom). Note that the y-axes have different zero-points. For orientation, the length of the spectroscopic period has been indicated in both plots using arbitrary zero-points.. Figure 21. Periodogram of the radial-velocity measurements of CTCV J1940−4724.. Figure 24. Low-resolution spectrum of CTCV J2056−3014 (see Table 2 for details).. Figure 22. The radial-velocity measurements for the CTCV J1940−4724 data. The solid curve in the plot gives the best fit at the spectroscopic period.. On two occasions we have observed this source apparently in outburst. A spectrum taken on 1996 August 2 (top curve in Fig. 20) shows the typical spectrum of a dwarf nova in outburst with a steeply rising blue continuum and all emission lines except Hα hidden in the absorption troughs of an optically thick disc. Acquisition frames taken during these observations indicate a brightness ∼3 mag higher with respect to quiescence data. The photometric observations from 1996 April 23 (top panel in Fig. 23) show the system ∼1.5 mag brighter than quiescence, apparently slowly rising in brightness (V ∼ 0.16 mag over 3 h). This might have indicated the onset of an outburst, but any outburst must have been short-lived since the system was back in quiescence only 5 days later (bottom panel in Fig. 23). The source was also detected on various occasions (apparently) in outburst by the ASAS. 3.7 CTCV J2056−3014 The low-resolution spectrum of CTCV J2056−3014 is presented in Fig. 24. Time-resolved spectroscopy of CTCV J2056−3014 con C. C 2010 RAS, MNRAS 405, 621–637 2010 The Authors. Journal compilation . Figure 25. Periodograms for the radial-velocity observations of CTCV J2056−3014 taken on 2001 August 28 (top) and 2002 July 7 (bottom).. sists of two nights of observation taken nearly one year apart. The periodogram for each night as presented in Fig. 25 show a clear signal at a frequency of ∼13.5 cycles d−1 . From a least-squares sinusoidal fit to the observations of each night individually we derive periods of 0.0743(24) d (data from 2001 August 28) and 0.0725(19) d (2002 July 7), which are consistent within 3σ . Also, consistent results are obtained for the radial-velocity amplitudes, 59(10) and 84(6) km s−1 , and the systemic velocities, −23(7) and −47(4) km s−1 , respectively. From this we conclude that the source. Downloaded from http://mnras.oxfordjournals.org/ at Pontificia Universidad CatÃ¯Â¿Â½lica de Chile on May 19, 2016. Figure 20. Low-resolution spectra of CTCV J1940−4724 in outburst (top) and in quiescence (bottom). The outburst spectra have been scaled down by a factor of 2. For details of the observations see Table 2.. 629.

(10) 630. T. Augusteijn et al.. Figure 28. Periodogram for the photometric data of CTCV J2056−3014. Prior to the computation of the periodogram the long-term trend in the light curve was removed.. Figure 29. The photometric data of CTCV J2056−3014 folded at the ∼15.4 min (see text). Prior to the computation of the periodogram the long-term trend in the light curve was removed. The error bars indicate the error in the mean in each phase bin. The period is shown twice for clarity. Figure 27. Photometric light curve for CTCV J2056−3014 from 1996 October 2. For orientation, two cycles of the spectroscopic period have been indicated in the plot, using an arbitrary zero-point. Tick marks indicate the computed maxima for the ∼15.4 min signal. The zero-point for this sequence is marked by a cross.. rather typical for IP type CVs, while the very strong variations from cycle to cycle seen in Fig. 27 are not uncommon for IPs. CTCV J2056−3014 can likely be identified with the ROSAT X-ray source 1RXS J205652.1−301433 which also strengthens the credentials for the source being an IP. However, the source was also detected on a few occasions in a bright state by the ASAS indicating likely dwarf nova outburst. This does not exclude the possibility of the source being an IP, but might explain the detection of the source in X-rays. In any case, it is clear that the possible IP nature of this source needs confirmation, but it would be interesting as finding such a source with such a short orbital period is exceptional.. has a stable periodic radial-velocity variation which we identify with the orbital period of the system. The T sup values as derived from the fits are HJD 245 2150.6126(21) and 245 2463.837 16(91), respectively. The time-span between these times is too long to maintain the cycle count and derive an ephemeris. As a best period estimate we take the error-weighted mean of the periods derived for each night, which corresponds to Porb = 0.0732(15) d. The folded radial-velocity curves for the two different nights as presented in Fig. 26 show that due to the lower S/N (smaller telescope) the data from 2001 August 28 has a much higher scatter than the data from 2002 July 7. However, by directly comparing the curves there does not seem to be a significant difference. What is clear from the 2002 July 7 data is that the radial-velocity curve does not have a nice sinusoidal shape. This is likely due to an additional source of emission in the system which has a variable contribution to the line profile and the resulting observed radial velocity. Photometric observations of CTCV J2056−3014 obtained over a period of ∼4.5 h on 1996 October 2 are presented in Fig. 27. The light curve does not show any evidence of orbital modulation, but large short time-scale more or less periodic variations are present. A periodogram of the data after removing the low frequency variation in the light curve is presented in Fig. 28 and shows a strong coherent signal at a frequency of 93.3 cycles d−1 , corresponding to P ∼ 15.4 min. The average folded light curve shown in Fig. 29 has a more or less sinusoidal shape with a peak-to-peak amplitude of ∼15 per cent. The period, amplitude and light-curve shape are. 3.8 CTCV J2118−3412 The low-resolution spectrum of CTCV J2118−3412 is presented in Fig. 30. Time-resolved spectroscopy of CTCV J2118−3412 consists of a set of 41 observations taken during one night (2005 February 16) over a time-span of 3.4 h. The periodogram of the data presented in Fig. 31 shows a single peak at ∼13 cycles d−1 , i.e. a period of 0.075 d. From a least-squares sinusoidal fit to the data we derive a period of 0.0753(27) d with a radial-velocity amplitude of 49(5) km s−1 , and a systemic velocity of −65(4) km s−1 . The T sup as derived from the fit is HJD 245 0965.9058(14). A plot of the radial velocity as a function of time shows this periodic variation, but also shows a clear trend of the velocity with time. This is also reflected in the periodogram by the increase of power towards low frequencies. This might be an indication of a second, longer period variation in the radial velocity, but that period would have to be significantly longer (≥6 h) than the total time-span of the observations. However, such a long orbital period is unlikely and we believe this trend actually to be an instrumental effect (e.g. flexure of C. C 2010 RAS, MNRAS 405, 621–637 2010 The Authors. Journal compilation . Downloaded from http://mnras.oxfordjournals.org/ at Pontificia Universidad CatÃ¯Â¿Â½lica de Chile on May 19, 2016. Figure 26. The radial velocities for the CTCV J2056−3014 data from 2001 August 28 (top) and 2002 July 7 (bottom). The solid curves give the best fit for each data set separately..

(11) CVs from the Calán–Tololo Survey – II.. 631. Figure 31. Periodogram of the radial-velocity measurements of CTCV J2118−3412.. Figure 33. Photometric light curves are shown for CTCV J2118−3412 from 1996 October 4, 1997 May 6 and 1997 May 7 (top to bottom). For orientation, the spectroscopic period has been indicated by horizontal lines with arbitrary zero-points.. the source is ∼1 mag brighter and shows much higher amplitude V ≈ 0.5 mag variations. It is not clear if this indicates any outburst or more regular brightness variations of the system. The source was also detected on various occasions in a bright state by the ASAS. 4 DISCUSSION. Figure 32. The radial velocities for the CTCV J2118−3412 data. The solid curve gives the best fit including a linear trend (see text).. the instrument and/or the star moving within/out of the slit). We note that the integrated flux from the spectra do vary in time (see Fig. 34), but these variations are similar to those observed in the photometric data (see below) and are not correlated with the observed trend in velocity. From a least-squares sinusoidal fit including a linear trend to the data (shown as the solid line in Fig. 32) we derive a period of 0.0755(23) d with a radial-velocity amplitude of 39(4) km s−1 , and a systemic velocity of −65(3) km s−1 . The T sup as derived from the fit is HJD 245 0965.9049(13). The precise value of the systemic velocity remains doubtful, but we believe the later results for the period and radial-velocity amplitude to be more reliable. The best-fitting linear trend corresponds to a change in velocity of −471(72) km s−1 d−1 , or a total change of 66 km s−1 over the length of the observations. Photometric observations of CTCV J2118−3412 were obtained on three different nights and are presented in Fig. 33. The light curves do note show any obvious sign of variations at the orbital period but there is a clear difference in overall behaviour between the observations on 1996 October 4, and 1997 May 6 and 7. In the former the source is relatively faint at V ∼ 16.4 mag and shows a relatively low amplitude variation, while in the latter two nights C. C 2010 RAS, MNRAS 405, 621–637 2010 The Authors. Journal compilation . In the following we discuss the results from our search for CVs in the CTS from different viewpoints. In the first part we will look at the general properties of the systems presented in this paper, and in the second part we discuss the complete sample of CVs found in the CTS. We note that objects in the CTS were selected through visual inspection of the objective prism plates. As they were not the primary objectives of the survey, candidate CVs were generally only identified serendipitously and we expect the resulting sample of CVs presented here to be very incomplete and suffer from ill-defined selection effects. We here mostly limit ourselves to a comparison with the general known sample of CVs. 4.1 Newly discovered periods The general aim of the observations presented in this paper was to search for orbital radial-velocity variations for those sources discovered in the CTS for which no period was known and this could not be derived from the photometric observations like for those sources presented in Paper I. A summary of the results from the time-resolved spectroscopic observations is given in Table 3 where we present the radial-velocity amplitude and the width of the Hα emission used to derive the radialvelocity curves as a function of orbital period. A general property of interest is the orbital inclination of the systems. For example, a low inclination could explain why no clear photometric variations were detected for the system presented here (e.g. four out of the six systems presented in Paper I for which we derived the orbital period from photometric observations are eclipsing systems), but the inclination is also relevant for the question why these sources. Downloaded from http://mnras.oxfordjournals.org/ at Pontificia Universidad CatÃ¯Â¿Â½lica de Chile on May 19, 2016. Figure 30. Low-resolution spectrum of CTCV J2118−3412 (see Table 2 for details)..

(12) 632. T. Augusteijn et al. Table 3. Summary of the results. CTCV. Porb (d). J0333−4451 J1057−2156 J2056−3014 J2118−3412 J0006−6900 J1940−4724 J1226−2527 J0950−2345. 0.062 864b 0.0699 0.0732 0.0755 0.0790 0.0809 0.154 35 0.237 81c. K (km s−1 ). FWHMa. 69(5)a 18(3) 77(5)d 39(4) 105(6)d 72(7) 120(8) 67(3). 1510 540 1940 1330 1920 1470 1270 580. linewidth in km s−1 (see Fig. A1). period 0.059 123 d (see Section 3.2). c Exact period is (89.8031d)/N, where N ∈ 374–382. d Error-weighted average of separate measurements. a Hα. b Alternative. and J0006−6900 at the highest. Purely comparing the numbers, J1057−2156 would need to be close to face-on to avoid J0006−6900 being an eclipsing system. However, the photometric observations of these sources are not so clear. The light curve of J0006−6900 does show a rather high amplitude variation as expected for a high-inclination system (though there is no obvious sign of eclipses), but the time-scale of variations is too long compared to the orbital period, while J1057−2156 does show significant photometric variation but they are not consistent with the orbital period and might be dominated by variations in the accretion rate in this system. The linewidth for the longer period systems are both relatively low, but for these systems the emission from an accretion disc is expected to be dominated by emission from the outer, slower moving part of the disc. In any case, the radial-velocity amplitude and the linewidth do correlate for these systems as well and one can conclude that J1226−2527 has a relatively low inclination and J0950−2345 a relatively high inclination. Assuming the radial-velocity amplitude reflects the motion of the white dwarf, and assuming standard system parameters we derive approximate estimates of the inclination of i ∼ 70◦ and 25◦ for J1226−2527 and J0950−2345, respectively. The main conclusion to draw from the results presented here and in Paper I is that using photometric observations to search for variations at the orbital period is very uncertain and inefficient (only six out of the 14 sources for which we determined the period) with basically only providing reliable detection of the orbital period for eclipsing systems.. Figure 34. Spectrophotometric V magnitude for CTCV J2118−3412 from the time-resolved spectroscopy on 1998 May 31. For orientation, the spectroscopic period has been indicated by a horizontal line with arbitrary zeropoint.. were not discovered before (see below). If the line emission comes from the accretion disc centred on the white dwarf (and with all else being equal) its radial-velocity amplitude should increase with orbital period and inclination, while the linewidth should increase only as a function of inclination. It is true that the line might include some additional source of emission (see the radial-velocity curve for J2056−3014 presented in Fig. 26) which, e.g. might originate in the hotspot, but there is also no reason to believe that measuring the radial-velocity variations and widths of the same emission line in different sources would represent very different parts of the systems. In Fig. 35 we show the relation between the radial-velocity amplitude and the width of the Hα emission presented in Table 3 in graphical form, where the filled squares indicate the sources below the period gap. This figure shows the predicted relation between the radial-velocity amplitude and linewidth. Specifically, just looking at the short-period systems where the variation in period is small (the filled squares in Fig. 35) there is a rather tight relation between the radial-velocity amplitude and the linewidth, while the two longperiod systems have higher radial-velocity amplitudes for the same linewidth as expected. This shows that these values do give an indication of the global distribution in orbital inclination of the sample of sources presented here without making any specific assumptions about the precise origin of the line emission or the system parameters. We do note that the measured values of K all fall in the range expected for reasonable values of the system parameters. From the results we conclude that J1057−2156 likely has a low inclination, J2118−3412 a somewhat higher, J1940−4724, J0333−4451 and J2056−3014 all at intermediate inclinations. 4.2 Cataclysmic variables in the Calán–Tololo Survey We will now look at the general properties of the sample of CVs detected in the CTS. Of the 21 systems detected, 16 were previously unknown and for 14 of them we have determined the orbital period. Beyond the systems listed in this paper and in Paper I, the other sources were either known before or discovered independently and the orbital period have been determined by other people (see Section 1). C. C 2010 RAS, MNRAS 405, 621–637 2010 The Authors. Journal compilation . Downloaded from http://mnras.oxfordjournals.org/ at Pontificia Universidad CatÃ¯Â¿Â½lica de Chile on May 19, 2016. Figure 35. The radial-velocity amplitude versus the width as given by the FWHM (both in km s−1 ) of the Hα emission for the data presented in Table 3. The filled squares correspond to sources with orbital periods below the period gap (see text)..

(13) CVs from the Calán–Tololo Survey – II.. In Fig. 36 we show the period distribution of all the sources discovered in the CTS5 together with the distribution for ‘all’ CVs as derived from the catalogue of Ritter & Kolb (2003)6 and, for a more direct comparison to the sample from the CTS, the distribution for all CVs with |b| ≥ 20◦ . Although neither the sample of CVs detected in the CTS nor the sample of known CVs with a measured orbital period is a well-defined sample, there does not appear to be any fundamental difference between the distributions. The main thing to note is that there is no strong peak in the distribution for the CTS sources close to the period minimum. In fact, only one of the 21 sources from the CTS has a period below 85 min; so clearly our sample does not provide an explanation for the marked discrepancy between population-synthesis models and the observed sample. The fraction of ‘nova-like’ CVs (marked as ‘NL’ in the catalogue of Ritter & Kolb (2003), where we only include those classifications marked as certain) for all CVs is significantly higher at 21 per cent (20 per cent for all CVs with |b| ≥ 20◦ ) compared to that in the CTS (only one out of 21 sources). However, many of the sources classified as ‘NL’ do not show emission lines and will not be recognized in the CTS. As these types of CVs typically have long orbital periods this can actually largely explain the difference in the fraction of sources with short compared to long orbital periods. The fraction of strongly magnetic ‘polar’ type CVs (marked as ‘AM’. 5 Note. that distribution for the CTS sources is the same independent of the specific period that is selected for CTCV J0333−4451 (see Section 3.2). 6 From the catalogue we have included only those sources with a welldefined orbital period. To limit the sample to the local population and avoid obviously distant sources we have excluded all sources classified as (suspected) novae, recurrent novae and supersoft sources, and sources that are located in globular clusters. We also excluded the AM CVn type sources, as they are a population different from regular CVs, and the three exceptional sources V485 Cen, EI Psc and J1507+523 which are all likely examples of non-standard evolutionary paths. C. C 2010 RAS, MNRAS 405, 621–637 2010 The Authors. Journal compilation . in the catalogue of Ritter & Kolb 2003, where we again only include those classifications marked as certain) for all CVs is similar at 15 per cent (19 per cent for all CVs with |b| ≥ 20◦ ) compared to that in the CTS (19 per cent). A mild discrepancy is that two out of the four polars in the CTS have orbital periods above the period gap, while one would expect all four of the sources to have periods in or below the period gap. A formal Kolmogorov–Smirnov (KS) test shows a relatively large KS statistics of d = 0.23 when comparing the overall orbital period distribution for CVs from the CTS with that for ‘all’ CVs, giving a probability of only 23 per cent that they are drawn from the same parent distribution. The match is significantly better when comparing to the distribution of CVs with |b| ≥ 20◦ which gives d = 0.17 and a probability of 56 per cent. This likely reflects the general bias towards intrinsically bright (and more distant) long-period systems at low galactic latitude which should less affect the distribution of CVs from the CTS and that of CVs with |b| ≥ 20◦ in general. Specifically, the fraction of sources below, in, and above the period gap (here we assume the limits for the period gap as defined by Knigge 2006) is 51 per cent/9 per cent/40 per cent for all CVS, 59 per cent/8 per cent/34 per cent for all CVs with |b| ≥ 20◦ ) and 71 per cent/5 per cent/24 per cent for the CTS. We note that most of the targets have by now been detected in the ASAS (see Table B1) indicating that they were in reach of typical patrol plate surveys (e.g. the Harvard Plate Collection7 ; in fact, CTCV J0006−6900 and CTCV J1057−2156 were detected in such surveys, see Sections 3.1 and 3.4). That is, also in this aspect the sources detected in the CTS are not fundamentally different from the known sample of CVs but they basically were just not identified until now. Given the poorly defined selection effects we feel that any more detailed and in-depth analysis or comparison with other surveys is not warranted. However, the general set-up of the HQS (Hagen et al. 1995) is very similar to the CTS and we briefly compared our results with those of the survey for CVs in the HQS (Gänsicke et al. 2002; Aungwerojwit et al. 2006). In the HQS there is also no peak found at the period minimum in the orbital period distribution, but compared to that for the CTS the overall distribution for the HQS is weighted relatively strongly towards periods above the period gap. The main difference between the selection of the samples is that for the HQS the objective prism plates have been scanned and the spectra analysed digitally. We believe this to make the selection from the HQS more sensitive to spectra with relatively low equivalent width emission lines, something more likely to be found in longer period, which might explain the high incidence of long-period systems in the HQS compared to our sample. This might also explain why the HQS has a larger fraction of system with periods above the period gap when compared to the distribution of ‘all’ CVs, where the general sample of CVs is probably more biased against low-amplitude-outburst, long-period dwarf nova type CVs. For the sample from the CTS (and also the HQS) we conclude that it is not fundamentally different from the known sample of CVs, and do not represent a hitherto undetected part of the intrinsic population (specifically those source evolving past the period minimum). We note that this conclusion is completely in line with that recently presented by (Gänsicke et al. 2009) which show that you have to go to significantly fainter limiting magnitudes to detect these sources.. 7 See. http://www.cfa.harvard.edu/hco/plates.html. Downloaded from http://mnras.oxfordjournals.org/ at Pontificia Universidad CatÃ¯Â¿Â½lica de Chile on May 19, 2016. Figure 36. The distribution of orbital periods for CVs detected in the CTS (bottom) and the distribution for ‘all’ CVs (top) where the shaded area refers to those sources with |b| ≥ 20◦ (see text).. 633.

(14) 634. T. Augusteijn et al.. AC K N OW L E D G M E N T S We especially would like to thank Linda Schmidtobreick for performing the CTIO observations, and George Hau for making available the 2002 July observations at ESO. We also would like to acknowledge the reviewer whose comments significantly improved this paper. Parts of this research are based on observations made at ESO, proposal numbers 57.D-0704, 58.D-0549, 58.D-0551, 59.D-0368 and 74.D-0343. This work has made intensive use of the SIMBAD data base, operated at CDS, Strasbourg, France. The Digitized Sky Surveys were produced at the Space Telescope Science Institute under US Government grant NAG W-2166, based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. IRAF is distributed by the National Optical Astronomy Observatories. CT acknowledges financial support by FONDECYT grant 1051078. 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(15) CVs from the Calán–Tololo Survey – II.. 635. Table A1. Equivalent widths (in Å) of the most prominent emission lines. A blank field indicates that this part of the spectrum was not covered by the data, a ‘–’ indicates that the corresponding line was not detected. The last column gives the FWHM (in Å) of a single Gaussian fitted to the Hα line. CTCV. Date 4102. J0006−6900. J0333−4451. AG Hya. J1057−2156 J1226−2527 J1940−4724 J2056−3014. J2118−3413. 1996-10-09 2001-08-29 2002-07-06 1996-10-09 2001-08-29 2002-07-07 2004-11-17 2004-11-29 2005-02-15 1997-04-29 2005-02-16 1996-04-13 2005-02-17 1996-08-02 1998-05-31 1996-10-09 2001-08-28 2002-07-07 1996-10-09 1998-05-31. 34. 71. Balmer 4340 4861. 44. 66 61a. 91. 61 136a. 7. 7. 7. 50. 79. 81 65. – 53. – 62. 97. 102. – 90a 18 196a. 76. 114a 120a. 69. 4471. 5016. 78 62 91 109 129 90 18 10 19 108 117 102 130 9 98 41 243 158 104 123. 25 8. 18 11. 30 16. 16 35. 25 20. 44 46. –. –. <1. 23. 12. 30. 10. 35. – 16 4 27. – 14 3 25. – 28 7 79. 23 24. 20 16. 38 42. a Value b Line. C. He I 5876. 6563. includes nearby He I λ4922 line. is not resolved, i.e. FWHM is comparable to spectral resolution.. C 2010 RAS, MNRAS 405, 621–637 2010 The Authors. Journal compilation . 6678. 7065. 12 7 16 31 21 15 1 <1 1 14 13 16 12 – 12 6 40 27 21 21. 23. He II 4686. Fe II 5173. 23 15. 11 8. 18 28. 27 16. 11. 12 1 <1 1 18 9 17 16 – 7 26 11. OI 7773. 9. 12 1. –. 14. 11. 17. –. – 8 7 8. – 10 4 16. 10 16. 13 16. 6 6 – – – – 13 10. FWHM Hα 50 42 43 34 37 35 14 10 13 31b 12 28 28 33b 33 43 52 38 34 29. Downloaded from http://mnras.oxfordjournals.org/ at Pontificia Universidad CatÃ¯Â¿Â½lica de Chile on May 19, 2016. Figure A1. Selected line profiles of the CTCV sources, roughly sorted with respect to their average equivalent width (from left- to right-hand side and top to bottom)..

(16) 636. T. Augusteijn et al.. Table B1. mV refers to the observed brightness range in V for non-orbital variations (e.g. quiescence–outburst). For eclipsing systems, the out-of-eclipse value is given. For Porb the superscript ‘ec’ indicates if a system is eclipsing. The column ASAS refers to if a source has been detected in a bright state by the All Sky Automated Survey (Pojmanski 2002). RA (J2000). Dec. (J2000). mV. Porb (h). Other name. Typea. J0006−6900 J0021−5142 J0333−4451 J0549−4921 J0950−2345 J1007−2017 J1057−2156 J1103−2137 J1114−3740 J1226−2527 J1300−3052 J1313−3259 J1331−2940 J1928−5001 J1938−4612 J1940−4724 J2005−2934 J2056−3014 J2118−3412 J2315−3048 J2354−4700. 00:06:33.4 00:21:33.1 03:33:20.6 05:49:45.4 09:50:29.9 10:07:34.6 10:57:49.8 11:03:36.5 11:14:00.1 12:26:17.4 13:00:29.1 13:13:17.1 13:31:53.8 19:28:32.6 19:38:35.8 19:40:37.6 20:05:51.2 20:56:52.0 21:18:04.3 23:15:31.9 23:54:20.4. −69:00:33 −51:42:34 −44:51:42 −49:21:56 −23:45:18 −20:17:33 −21:56:58 −21:37:46 −37:40:49 −25:27:05 −30:52:57 −32:59:13 −29:40:59 −50:01:34 −46:12:56 −47:24:49 −29:34:58 −30:14:38 −34:13:43 −30:48:46 −47:00:20. 15.3 16.5–15.3 17.8 17.3–13.7 19.2–14.3 19.5–18.5 18.7–17.8 17.5–12.1 16.0–11.5 18.6–16.7 18.7–15.4 16.3–14.6 18.3–14.4 18.0 17.4–15.2 16.6–13.9 15.9 16.6–15.2 16.4–15.5 16.8 19.2. 1.90 6.45 1.51 1.93 5.71 3.47 1.68 1.97 1.50 3.70 2.14ec 4.19 1.80 1.68ec 2.33 1.94 1.51 1.76 1.81 1.40ec 1.57ec. AN 97.1933 CM Phe. dn nl? dn dn dn am dn dn dn dn? dn am dn am am dn dn ip? dn dn dn. AG Hya 1RXS J100734.4−201731 AN 683.1936 TU Crt V436 Cen. V1043 Cen, 1RXS J131317.1−325909 LY Hya 2EUVE J1928−50.0? QS Tel. 1RXS J205652.1−301433 CC Scl, EC 23128−3105. ASAS Y N N Y Y N Y Y Y N N Y N N N Y N Y Y Y N. Referenceb 2 7, 8, 18 2 1 2, 16 3, 12, 14 2 9, 10 6 2 1 13, 17 15 1, 11 4 2 1 2 2 1, 5 1. a Types:. am, polar; dn, dwarf nova; ip, intermediate polar; nl, nova-like. (1) Paper I, (2) this paper, (3) Beuermann & Thomas 1993, (4) Buckley et al. 1993, (5) Chen et al. 2001, (6) Gilliland 1982, (7) Hoard & Wachter 1998, (8) Hoard, Wachter & Kim-Quijano 2001, (9) Maza et al. 1992, (10) Patterson et al. 2003, (11) Potter, Augusteijn & Tappert 2005, (12) Ramsay & Cropper 2004, (13) Ramsay et al. 2004, (14) Reinsch et al. 1999, (15) Still et al. 1994, (16) Szkody 1987, (17) Thomas et al. 2000, (18) Woudt & Warner 2002.. b References:. Figure C1. Finding charts from the Digitized Sky Survey. Note that CTCV J2056−3014 appears in outburst.. C. C 2010 RAS, MNRAS 405, 621–637 2010 The Authors. Journal compilation . Downloaded from http://mnras.oxfordjournals.org/ at Pontificia Universidad CatÃ¯Â¿Â½lica de Chile on May 19, 2016. CTCV.

(17) CVs from the Calán–Tololo Survey – II.. This paper has been typeset from a TEX/LATEX file prepared by the author.. C. C 2010 RAS, MNRAS 405, 621–637 2010 The Authors. Journal compilation . Downloaded from http://mnras.oxfordjournals.org/ at Pontificia Universidad CatÃ¯Â¿Â½lica de Chile on May 19, 2016. Figure C1 – continued. 637.

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