Spectral analysis of BD+30°623, the peculiar binary central star of the planetary nebula NGC 1514★

Abstract

NGC 1514 is a complex planetary nebula with a peculiar binary central star (BD+30• 623) consisting of a cool star and a hot companion. To date, the parameters of the two stars have not been firmly stablished. We present a detailed spectral analysis of BD+30• 623 based on intermediate-resolution CAFOS optical spectra and IUE ultraviolet spectra with the goal of deriving the parameters of the two stars. For this purpose, we used an extensive composite grid of Kurucz and Tübingen NLTE Model-Atmosphere spectra. From the fitting procedure, in terms of the minimum χ 2 method, the best models obtained correspond to an HorizontalBranch A0 star with T eff = 9850±150 K, log g = 3.50±0.25, and a hot companion with T eff between 80000 K and 95000 K and a log g ≃ 5.5. To our knowledge, this is the first time that the parameters of both stars have been determined accurately through a detailed spectroscopic analysis.

The long-period binary central stars of the planetary nebulae NGC 1514 and LoTr 5

“…The poor fit and general scatter of the points is almost certainly attributable to the rotational velocity of the star, which, while not extreme (∼40 km s −1 ; Greenstein 1972), is much higher than the amplitude of the orbital motion. Aller et al (2015) found that the cool A-type component could either be on the HB with mass ∼0.55 M or, alternatively, a post-MS star with mass ∼3 M . While the observed radial velocity amplitude ratio (and therefore mass ratio) of the SB2 binary has a large uncertainty that is mainly due to the large scatter in the velocities of the cool component, we can safely state that the mass ratio, q, is 2.…”

“…The more detailed analysis of Aller et al (2015) found the spectrum of the hot component to be consistent with an sdO classification and the cool component to be an A0-type star that is most likely in a horizontal branch (HB) evolutionary phase, although the possibility that the star is a more massive post-main-sequence (post-MS) star could not be ruled out (see also Méndez et al 2016). Montez et al (2015) showed the CS to be a compact source of X-rays, the potential origin of which they were unable to constrain.…”

“…2), obtained over a timespan of nearly 2711 days, with synthetic spectra produced individually for each component. For the cool component, the synthetic spectrum fit from Aller et al (2015) was used, while for the hot component a synthetic spectrum with parameters identical to those of Aller et al (2015), but with solar abundances (their spectrum includes only H and He), was produced using the TMAP package (Werner et al 2003). • 623 with selected features from both hot (blue) and cool (red) components marked.…”

The Two Central Stars of NGC 1514: Can They Actually Be Related?*

“…The spectrum of the cooler star has been sufficiently described in the literature (see e.g. Greenstein 1972 andAller et al 2015). The high spectral resolution and high signal-to-noise ratio of the Espadons spectra permit a good description of the hot star features.…”

“…There is no evidence of strong mass loss in the optical spectrum. If Aller et al (2015) are correct, and some H is present on the surface, then the spectral type, in the system of Méndez (1991), is O(H). Figures 1 and 2 show the result of co-adding the 12 Espadons spectrograms.…”