published, but the study is early or one-sided: only part of the Kepler data, or no spectroscopy of its own
Worth checking for better spectra. The published values are KepI's, from a low-resolution classification spectrum (NOT/ALFOSC grism #6 or #14 at R ~ 600, or WHT at R ~ 1400). Held here are better data: a mean of 11 NOT grism #16 spectra from 2010 and a mean of 24 WHT ISIS spectra. Pablo et al. (2012) was published early and may not have waited for the updated spectroscopy -- CHECK with J. H. Telting and M. D. Reed whether this star was included in the spectroscopic survey and whether a better mean exists.
| reference | Pablo et al. 2012, MNRAS 422, 1343; Baran & Winans 2012, AcA 62, 343 |
| title | Seismic evidence for non-synchronization in two close sdB+dM binaries from Kepler photometry |
| Kepler data used | quarters Q5 to Q8, 2010 March to 2011 March |
| pulsations | High-overtone g modes. A sequence with equal period spacings is present but many more modes depart from it than in KIC 11179657. Rotational splitting of the pulsation frequencies shows the sdB rotates far too slowly to be synchronised with the orbit |
| orbit | Inclination approximately 80 deg; companion mass at least ~0.089 Msun and, from the tidal argument, below 0.26 Msun. A preliminary radial-velocity amplitude of 36 +- 2 km/s is quoted from Telting et al. (2011) |
| atmospheric parameters | Teff 27300 +- 200 K, log g 5.43 +- 0.03, quoted from Ostensen et al. (2010) -- the paper carries no spectroscopy of its own |
| the spectrum behind it | The published values are KepI's, from a low-resolution classification spectrum (NOT/ALFOSC grism #6 or #14 at R ~ 600, or WHT at R ~ 1400). Held here are better data: a mean of 11 NOT grism #16 spectra from 2010 and a mean of 24 WHT ISIS spectra. Pablo et al. (2012) was published early and may not have waited for the updated spectroscopy -- CHECK with J. H. Telting and M. D. Reed whether this star was included in the spectroscopic survey and whether a better mean exists. |
| note | A photometric study. Its result -- that neither sdB is tidally synchronised despite the close orbit -- is the same question the Toby project is asking of 2M1938+4603. |
Paper: Pablo12.pdf, in /home/roy/sync/old/sddoc.
| observation | telescope | date | n | S/N | FWHM [Å] | Teff [K] | log g | log n(He)/n(H) | residual | χ² |
|---|---|---|---|---|---|---|---|---|---|---|
| NOT | NOT / ALFOSC_FASU | 2010-05-18 | 11 | 92.3 | 2.14 | 25708 ± 173 | 5.396 ± 0.028 | -2.61 ± 0.07 | 2.05% | 1.46 |
| WHT ★ | WHT / ISIS blue arm | 2010-07-02 | 24 | 247.1 | 1.80 | 26649 ± 57 | 5.463 ± 0.010 | -2.48 ± 0.03 | 1.10% | 2.34 |
★ marks the observation adopted for the sample table — the one with the smallest residual, which is what says how well the model reproduces the spectrum. Signal-to-noise does not.
The line fit gives a temperature and a gravity but says nothing about size. Held at those parameters, the broadband spectral energy distribution has one free scale — the angular diameter — and the Gaia parallax turns that into a radius. Then M = gR²/G, which is linear in g: a tenth of a dex in gravity is 26 per cent in mass, so this is where the gravity scale bites hardest.
| distance [pc] | 2782 |
| parallax error [%] | 13.6 (per cent; the mass error is twice this) |
| E(44−55) [mag] | 0.136 (0.118–0.154) |
| … the dust map | 0.1298 (SFD×disk(f=0.98)) |
| log Θ [rad] | -11.514 +0.010 −0.010 |
| R [R☉] | 0.189 +0.030 −0.023 |
| M [M☉] | 0.379 +0.140 −0.094 |
| L [L☉] | 16.2 +5.6 −3.7 |
Bamberg v25 ATLAS12 through the real filter curves, reddened by Fitzpatrick (1999) — its A(5500)/E(B−V) is 3.03, so this E(B−V) and the E(44−55) of Heber's group are the same number to under one per cent. Prescribed at 26649 K and log g 5.463 from WHT, with 25 of the fitted bands and reduced χ² 0.07. The gravity error carried into the mass is 0.050 dex — the scatter between telescopes, not the formal error, because the formal one would claim a two per cent mass.
Bands left out: Johnson:B, GALEX:NUV, GALEX:FUV, WISE:W1, WISE:W2, GAIA/GAIA3:G, GAIA/GAIA3:Gbp, GAIA/GAIA3:Grp, SDSS:u, SDSS:g, SDSS:r, SDSS:i, SDSS:z, SDSS:u/SDSS:u', SDSS:g/SDSS:g', SDSS:r/SDSS:r', SDSS:i/SDSS:i', SDSS:z/SDSS:z', Johnson:U, Johnson:V, Cousins:U.
| reference | U. Heber, September 2026: KIC2991403_photometry_results1.pdf |
| his fit | with 27300 +- 500 K / 5.43 +- 0.07: E(44-55) 0.146 +0.005 -0.008, log Theta -11.517 +0.007 -0.008, R 0.180 +0.030 -0.022, M 0.30 +0.13 -0.09, L 16 |
| reproduced here | Reproduced here on the same prescription: log Theta -11.508, R 0.191, M 0.358. The radius agrees to 6 per cent and the mass to within a quarter of its own error bar. |
| how they compare | The reddening does not agree as well: 0.174 here against his 0.146. His fit had U and 2MASS J, H and K; at V = 17.0 the VizieR merge returns no 2MASS at all for this star, so the reddening here rests on the optical alone and is the weakest of the three. |
| note | The one target of the three where the mass barely moves between the published gravity and this one -- 5.43 to 5.463 is 0.03 dex. What dominates its error is the parallax: 0.36 +- 0.05 mas is a 14 per cent distance, so the mass cannot be pinned to better than about 30 per cent whatever the spectroscopy does. |