Erratum: The donor stars of cataclysmic variables

Authors

Errata

This article corrects:

  1. The donor stars of cataclysmic variables Volume 373, Issue 2, 484–502, Article first published online: 31 October 2006

E-mail: christian@astro.soton.ac.uk

The paper ‘The donor stars of cataclysmic variables’ was published in Mon. Not. R. Astron. Soc. 373, 484–502 (2006). We have recently discovered an error in the code that interpolates on the model atmosphere grid that was used in the paper. The error onlyaffects the brown dwarf regime of the semi-empirical donor sequence (M2≲ 0.080 M) and only the predicted photometric properties of these lowest mass donors. Below, we provide a corrected version of the donor sequence (Table 3 in the original paper; a high-resolution version is again available electronically), and also of Figs 8 and 10. The comparison between the donor sequence and the observations in the SpTPorb plane – shown in Fig. 9 of the paper – remains almost completely unaffected. The corrected sequence does turn over somewhat more steeply towards later SpTs at the very shortest periods shown in Fig. 9 (Porb≲ 1.5 h), but this is already beyond the range covered by the data.

Table 3.  The semi-empirical donor sequence for CVs. Orbital periods are in hours, masses, radii and luminosities in solar units, and effective temperatures in kelvin. UBVRI magnitudes are given on the Johnson–Cousins system (Bessell 1990), JHK magnitudes are on the CIT system (Elias et al. 1982a,b). The sequence provided here is abbreviated. A more complete sequence, using steps of 0.001 M and including the far-infrared L, L′ and M bands, is available in an electronic form – see the Supplementary Material section.
PorbM2R2Tefflog glog L2SpTMUMBMVMRMIMJMHMK
1.4620.0300.09510094.96428.50T37.8231.4026.4221.8919.0015.1415.1915.17
1.4200.0350.09811405.00328.74T35.3229.5525.7621.3318.3714.4214.5114.41
1.3840.0400.10012715.03728.96T33.5228.0925.0220.7517.8013.8913.8913.73
1.3530.0450.10314075.06729.15T32.2226.9224.2520.0917.1313.3813.3213.20
1.3260.0500.10515435.09429.33T31.1325.8923.3919.3216.4212.9112.7912.72
1.3020.0550.10716095.11829.42T30.8325.6423.0319.0916.2712.7812.5312.41
1.2810.0600.10916755.14129.51T31.6826.6723.0919.7117.2113.2712.2711.61
1.2680.0630.11017325.15329.57T31.2226.4122.6319.5817.2113.2112.0411.24
1.2900.0650.11317845.14829.65L6.729.8725.2821.7918.9116.5612.7411.7611.10
1.3340.0700.11818945.13929.79L2.628.9024.4221.1518.3615.9712.3211.4610.90
1.3770.0750.12320035.13129.93L3.728.9823.4421.2618.6815.8611.6210.9010.66
1.4180.0800.12823135.12430.21M9.024.9420.9218.9417.0214.4610.9310.269.96
1.4570.0850.13324775.11630.36M7.622.8619.5517.7216.0513.6910.599.959.63
1.4960.0900.13826415.11030.51M6.821.0318.2916.5915.1012.9610.289.669.34
1.5330.0950.14327265.10330.59M6.520.1117.6416.0014.6012.5710.109.489.17
1.5690.1000.14828125.09730.67M6.319.2917.0415.4414.1112.209.939.329.00
1.6380.1100.15729215.08630.79M5.918.3016.2914.7513.5011.729.679.078.76
1.7040.1200.16629885.07630.88M5.617.7015.8114.3013.1011.409.488.888.58
1.7680.1300.17530555.06630.96M5.317.1615.3813.9012.7411.129.298.718.40
1.8280.1400.18331035.05731.03M5.016.7615.0613.5912.4610.899.148.558.26
1.8860.1500.19231515.04931.10M4.816.3714.7413.3012.2010.689.008.428.12
1.9420.1600.20031855.04231.15M4.616.0814.5013.0711.9910.518.878.308.00
1.9960.1700.20732185.03531.20M4.415.8214.2812.8611.8010.368.758.187.89
2.0490.1800.21532465.02831.25M4.315.6014.0912.6811.6410.228.658.077.79
2.1000.1900.22332695.02131.29M4.215.4213.9312.5311.5010.108.557.987.69
2.1490.2000.23032925.01531.33M4.015.2413.7712.3811.369.988.457.887.60
3.1790.2000.29932924.78931.56M4.214.5913.1911.8510.839.447.887.317.02
3.5590.2500.34733764.75631.73M3.813.9512.5811.2710.298.957.476.906.63
3.9020.3000.39234364.72931.87M3.513.4812.1310.849.888.587.156.576.31
4.2180.3500.43434754.70631.98M3.313.1311.7910.519.578.296.896.316.05
4.5120.4000.47535224.68632.08M3.112.8011.4610.199.268.026.656.065.82
4.7880.4500.51435824.66932.18M2.812.4711.139.868.967.756.425.835.60
5.0500.5000.55236494.65332.27M2.512.1610.819.548.667.496.205.605.39
5.2990.5500.58837604.63932.38M2.011.7910.409.148.287.195.975.355.16
5.5370.6000.62338934.62632.49M1.411.429.978.707.886.885.735.084.93
5.7660.6500.65840654.61532.61M0.410.969.458.197.406.545.484.834.71
5.9850.7000.69142394.60432.73K7.010.468.947.706.946.205.244.624.52
6.1980.7500.72444604.59332.85K5.09.748.347.156.435.855.004.424.35
Figure 8.

Physical and photometric parameters along the CV donor sequence. In the left-hand column, we show the physical donor parameters (M2, Teff,2, R2 and L2) as a function of orbital period. In the middle column, the solid lines show the optical absolute magnitudes (MU, MB, MV and MR) as a function of Porb. Finally, in the right-hand column, the solid lines correspond to the red optical and near-infrared absolute magnitudes (MI, MJ, MH and MK). The wiggles in the photometric parameters near period minimum are due to switches in the model atmosphere grids used (BCAH98, DUSTY, COND; see the original paper for details). In the middle and right-hand columns, we also show estimates of the absolute magnitude sequences expected for the accretion-heated white dwarfs in CVs (dashed lines).

Figure 10.

Infrared absolute magnitudes of CVs as a function of Porb. Points correspond to absolute magnitudes for CVs with trigonometric parallaxes and reliable 2MASS observations. Colours correspond to various CV subtypes, as indicated (DN = dwarf nova; SU = SU UMa star; NL = non-magnetic nova-like; AM = AM Her star; IP = intermediate polar). Systems with Porb > 6 h are shown as open symbols. Solid lines show the tracks predicted by the semi-empirical donor sequence, and dotted lines show the tracks corresponding to the BCAH98 5-Gyr isochrone. The dashed lines show the CV donor tracks shifted by the average offset between the data points and the pure donor predictions. These offsets are ΔJ= 1.56, ΔH= 1.34 and ΔK= 1.21, and the dispersions around these offsets are σΔJ= 1.25, σΔH= 1.12 and σΔK= 1.07. The donor contributions to the infrared light are thus typically 24 per cent (J), 29 per cent (H) and 33 per cent (K). Assuming 100 per cent donor contributions to the infrared yields lower limits that underestimate the true distances by factors of 2.05 (J), 1.86 (H) and 1.75 (K) for our sample. Adopting the mean donor contributions yields distance estimates with errors amounting to factors of 1.78 (J), 1.69 (H) and 1.64 (K). None of these numbers is significantly different from those quoted in the original paper.

With the error fixed, brown dwarf donors are even fainter than indicated in the original paper. However, we remind the reader that the empirical and theoretical constraints used to construct the donor sequence become increasingly uncertain in the substellar regime. In any case, none of the main conclusions in the original paper is affected.

We also take this opportunity to correct a typographical error in equation (C5) of the original paper. The statistical variance on the residual Δi is

image((C5))

The b-term was accidentally omitted in the paper, but was correctly used in all calculations. We note that this term acts to push the slope of the logarithmic mass–radius relation away from inline image. This explains why the best-fitting mass–radius relation in the short-period regime is slightly steeper than might be suggested by visual inspection of Fig. 3. We note for completeness that the fit can be forced towards a standard least-squares solution by artificially increasing the value assumed for the intrinsic dispersion. As expected, the logarithmic slope then tends to a slightly shallower value of 0.60 in the short-period regime (compared to our actual best-bet value of 0.64 ± 0.02), and the donor mass at period minimum becomes Mbounce= 0.053 M (compared to our actual best-bet value of Mbounce= 0.063 ± 0.009 M).

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