no detailed study of the Kepler data; the survey papers mention it, but a survey is not a study
The star was found in the first Kepler Blue Star (KBS) survey. No pulsations were detected in the Kepler data, so the target was left behind and nothing was ever published on it. KIC 1868650 = 2M 1926+3720.
| survey / pre-Kepler mention | For, Edelmann, Green, Drechsel, Nesslinger & Fontaine 2008, ASP Conf. Ser. 392 -- identified KBS 13 as a reflection-effect sdB+dM binary. A detailed study, but it PREDATES Kepler, so the Kepler data remain unpublished. No copy is in the local library. |
| survey archive | A LAMOST DR11 spectrum is here as LAMOST/, fitted in the LAMOST sample: 29243 +- 152 / 5.824 +- 0.021, against 28990 / 5.740 from the Bok spectrum. Three further DR11 epochs are available. |
| observation | telescope | date | n | S/N | FWHM [Å] | Teff [K] | log g | log n(He)/n(H) | residual | χ² |
|---|---|---|---|---|---|---|---|---|---|---|
| BOK ★ | bok / bcspeclamps | 2006-07-06 | 5 | nan | 9.00 | 28990 ± 32 | 5.740 ± 0.008 | -1.70 ± 0.01 | 0.96% | 5.57 |
| LAMOST | LAMOST | 1 | 153.0 | 2.50 | 29243 ± 152 | 5.824 ± 0.021 | -1.62 ± 0.02 | 1.06% | 0.98 |
★ 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] | 578 |
| parallax error [%] | 1.4 (per cent; the mass error is twice this) |
| E(44−55) [mag] | 0.082 (0.072–0.094) |
| … the dust map | 0.1306 (SFD×disk(f=0.55)) |
| log Θ [rad] | -10.900 +0.006 −0.006 |
| R [R☉] | 0.161 +0.003 −0.003 |
| M [M☉] | 0.523 +0.068 −0.060 |
| L [L☉] | 16.6 +0.8 −0.8 |
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 28990 K and log g 5.740 from BOK, with 32 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, SDSS:r, WISE:W3, WISE:W4, GAIA/GAIA3:G, GAIA/GAIA3:Gbp, GAIA/GAIA3:Grp, SDSS:u, SDSS:g, 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, 2MASS:J, 2MASS:H, 2MASS:Ks, WISE:W1, WISE:W2, PAN-STARRS/PS1:y — the last of these was not excluded by rule but clipped, sitting beyond five sigma of a model that fits its neighbours.
| note | No SED fit. The merged photometry does not describe one star: it puts SDSS g at 15.6 mag between Gaia BP at 13.5 and V at 13.7, and SDSS i at 17.5 where Gaia RP says 14.2 -- a spread of 5.4 mag across the optical, which no stellar spectrum does. At galactic latitude +9.8 this is blending in a crowded field, and the fit reaches a reduced chi-square of 256 trying to reconcile it. Fixing it means going back to the individual catalogues with a tighter match radius rather than taking the VizieR merge. |
A cool companion and extra reddening both redden the model, so the reddening is HELD rather than fitted -- at the one-star value where that agreed with the dust map, and at the map's value where it did not, since there the disagreement IS the companion.
| companion Teff [K] | 3500 |
| … log g (held) | 4.50 |
| R1 [R☉] | 0.1602 |
| R2 [R☉] | 0.2891 |
| main-sequence R at that T [R☉] | 0.360 |
| R2 over that | 0.80 |
| Δχ² over one star | 37.8 |
| reduced χ² | 0.15 |
| excess over one star | 3.0 sigma on WISE:W1 |
| bands put back for it | 2MASS:J, 2MASS:H, 2MASS:Ks, WISE:W1, WISE:W2 |
| reddening | 0.082 (held) |
| verdict | rejected |
Not adopted. the companion temperature railed at the 3500 K edge of the grid, so neither it nor the radius it implies is a measurement
bok/ is a copy of the fitprof22 working directory from data/spek/kepler/KepI/KBS13, with the source frame kbs13.fits brought in from KepI/Betsy beside it. It holds no sp.spek, so fitk1 does not read it. The live directory is BOK/, linked to the master. Bok 2.3m B&C at 2.76 A/px and about 9 A resolution: only ~200 pixels enter the fit and the continuum-window noise model underestimates sigma on a spectrum this heavily rebinned, so reduced chi-square runs high while the residual rms stays normal. Rosie/BOK is the same instrument and behaves the same way.