a detailed study with both a full pulsation analysis and dedicated spectroscopy
| reference | Baran et al. 2015, A&A 573, A52 |
| title | KIC 8302197: a non-rotating or low-inclination pulsating subdwarf B star |
| Kepler data used | Q5-17 |
| pulsations | 30 significant modes; no multiplets at all, explained by either very slow rotation (> ~1000 d) or a pole-on orientation; mode identification rested on period spacing alone |
| spectra behind it | NOT/ALFOSC grism #16 and WHT, resolutions 0.22 nm and 0.17 nm respectively; twelve radial velocities bound any orbital amplitude |
| atmospheric parameters | Teff 27450 +- 200 K, log g 5.438 +- 0.033, log(nHe/nH) -2.56 +- 0.07 (NLTE) |
| earlier values | Ostensen et al. (2011, KepVI) derived 26400 +- 300 / 5.32 +- 0.04 / -2.7 +- 0.1 from a WHT/ISIS classification spectrum; superseded |
| the spectrum behind it | Baran et al. used NOT/ALFOSC grism #16 and WHT; both means are here, and the resolutions they quote (2.2 and 1.7 A) are the ones used in this project. |
| note | The quoted NOT and WHT resolutions, 2.2 and 1.7 A, are the values this project uses for those setups. |
Paper: Baran15a.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 | 2011-06-01 | 10 | 124.7 | 2.22 | 26656 ± 122 | 5.433 ± 0.019 | -2.56 ± 0.04 | 1.49% | 2.06 |
| WHT ★ | WHT / ISIS blue arm | 2010-07-27 | 2 | 109.5 | 2.00 | 26535 ± 126 | 5.456 ± 0.021 | -2.54 ± 0.04 | 1.27% | 1.32 |
| WHT-2009 | WHT / ISIS blue arm | 2009-07-16 | 1 | 57.2 | 5.00 | 25918 ± 243 | 5.326 ± 0.042 | -2.66 ± 0.14 | 2.29% | 1.57 |
| WHT1 | WHT / ISIS blue arm | 2010-07-27 | 1 | 77.7 | 1.85 | 26710 ± 181 | 5.478 ± 0.032 | -2.64 ± 0.07 | 1.62% | 1.21 |
| WHT2 | WHT / ISIS blue arm | 2010-07-28 | 1 | 58.7 | 2.03 | 26655 ± 229 | 5.417 ± 0.039 | -2.49 ± 0.08 | 1.98% | 1.13 |
★ 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] | 2161 |
| parallax error [%] | 8.3 (per cent; the mass error is twice this) |
| E(44−55) [mag] | 0.102 (0.088–0.116) |
| … the dust map | 0.1314 (SFD×disk(f=0.97)) |
| log Θ [rad] | -11.397 +0.008 −0.008 |
| R [R☉] | 0.192 +0.018 −0.015 |
| M [M☉] | 0.386 +0.090 −0.071 |
| L [L☉] | 16.5 +3.3 −2.5 |
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 26535 K and log g 5.456 from WHT, with 29 of the fitted bands and reduced χ² 0.10. 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, 2MASS:H, 2MASS:J, 2MASS:Ks, WISE:W1, WISE:W2, WISE:W3, WISE:W4, 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.
not/, wht/, wht1/, wht2/ and wht2009/ are copies of the original fitprof22 working directories from data/spek/kepler (K08302197 and KepVI/sdB/J19310+4413), kept as they were run, each with the line list of its own era. None holds an sp.spek, so fitk1 does not read them; fits/ holds the two raw WHT exposures. The live directories are NOT/ (NOT mean of 10), WHT/ (WHT mean of 2), WHT1/ and WHT2/ (the two exposures behind that mean) and WHT-2009/ (the earlier R300B run), all linked to the master. The 2010 fits of the WHT spectra used vsini = 29 km/s, which the Python fitter cannot do; folding it into the instrumental profile instead is worth about 25 K and 0.004 dex.