An Etymological Dictionary of Astronomy and Astrophysics

A → Wolf-Rayet star whose spectrum is dominated by emission lines of ionized nitrogen: N II 3995 Å, N III 4634-4661 Å, N III 5314 Å, N IV 3479-3484 Å, N IV 4058 Å, N V 4603 Å, N V 4619 Å, and N V 4933-4944 Å. This type is divided in sub-types WN2 to WN11.

See also: W short for Wolf-Rayet star, N for → nitrogen.

A → Wolf-Rayet star whose spectrum is dominated by emission lines of ionized nitrogen: N II 3995 Å, N III 4634-4661 Å, N III 5314 Å, N IV 3479-3484 Å, N IV 4058 Å, N V 4603 Å, N V 4619 Å, and N V 4933-4944 Å. This type is divided in sub-types WN2 to WN11.

See also: W short for Wolf-Rayet star, N for → nitrogen.

An object showing signatures of both → WN Wolf-Rayet stars and → WC Wolf-Rayet stars
in the same spectrum, originating from individual stars rather than from WN + WC → binary systems. Such a WN/WC signature implies that the surface composition of the star is → nitrogen and → carbon enriched. This hybrid state results from a mixing process between He-burning → convective core and the overlying nitrogen enriched layers. According to model predictions, this situation corresponds to a short transition phase, lasting 10³ to 10⁴ years, during which a WN star evolves into a WC star. The WN/WC stars so far detected are all of early types.

See also: → WN Wolf-Rayet; → WC Wolf-Rayet.

An object showing signatures of both → WN Wolf-Rayet stars and → WC Wolf-Rayet stars
in the same spectrum, originating from individual stars rather than from WN + WC → binary systems. Such a WN/WC signature implies that the surface composition of the star is → nitrogen and → carbon enriched. This hybrid state results from a mixing process between He-burning → convective core and the overlying nitrogen enriched layers. According to model predictions, this situation corresponds to a short transition phase, lasting 10³ to 10⁴ years, during which a WN star evolves into a WC star. The WN/WC stars so far detected are all of early types.

See also: → WN Wolf-Rayet; → WC Wolf-Rayet.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N III 4634-4641, 5314 Å as strong as N II 3995 Å, Balmer lines, He I with → P Cygni profile.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N III 4634-4641, 5314 Å as strong as N II 3995 Å, Balmer lines, He I with → P Cygni profile.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N II 3995 Å as strong as He II 4686 Å, N III 4634-4641, 5314 Å weak or absent, Balmer lines, He I with → P Cygni profile.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N II 3995 Å as strong as He II 4686 Å, N III 4634-4641, 5314 Å weak or absent, Balmer lines, He I with → P Cygni profile.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N V 4603, 4619 Å weak or absent,He II 4686 Å strong.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N V 4603, 4619 Å weak or absent,He II 4686 Å strong.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N V 4603, 4619 Å present, N IV 3479-3484, 4058 Å absent.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N V 4603, 4619 Å present, N IV 3479-3484, 4058 Å absent.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N IV 3479-3484, 4058 Å very weaker than N V 3479-3484, 4058 Å and N III 4634-4641, 5314 Å weak or absent.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N IV 3479-3484, 4058 Å very weaker than N V 3479-3484, 4058 Å and N III 4634-4641, 5314 Å weak or absent.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A new type of → Wolf-Rayet stars found in the → Large Magellanic Cloud (LMC). These stars have both strong → emission lines, as well as → He II lines and → Balmer lines in absorption and spectroscopically resemble a → WN3 and → O3V binary pair. However, they are visually too faint to be WN3+O3 V → binary systems. So far nine WN3/O3 types have been detected, making up ~ 6% of the population of LMC WRs. Their temperatures are estimated to be around 100,000 K, a bit hotter than the majority of → WN Wolf-Rayet stars (by around 10,000 K) although a few hotter WNs are known. The abundances are what you would expect for → CNO equilibrium. However, most anomalous are their → mass-loss rates which are more like that of an → O star than a WN star. While their evolutionary status is uncertain, their low mass-loss rates and → wind velocities suggest that they are not products of homogeneous evolution. It is possible instead that these stars represent an intermediate stage between O stars and WNs. Since WN3/O3 stars are unknown in the Milky Way, their formation would depend upon → metallicity (Neugent et al., 2017, arxiv:1704.05497).

See also: → WN3; → O3; → star.

A new type of → Wolf-Rayet stars found in the → Large Magellanic Cloud (LMC). These stars have both strong → emission lines, as well as → He II lines and → Balmer lines in absorption and spectroscopically resemble a → WN3 and → O3V binary pair. However, they are visually too faint to be WN3+O3 V → binary systems. So far nine WN3/O3 types have been detected, making up ~ 6% of the population of LMC WRs. Their temperatures are estimated to be around 100,000 K, a bit hotter than the majority of → WN Wolf-Rayet stars (by around 10,000 K) although a few hotter WNs are known. The abundances are what you would expect for → CNO equilibrium. However, most anomalous are their → mass-loss rates which are more like that of an → O star than a WN star. While their evolutionary status is uncertain, their low mass-loss rates and → wind velocities suggest that they are not products of homogeneous evolution. It is possible instead that these stars represent an intermediate stage between O stars and WNs. Since WN3/O3 stars are unknown in the Milky Way, their formation would depend upon → metallicity (Neugent et al., 2017, arxiv:1704.05497).

See also: → WN3; → O3; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N IV 3479-3484, 4058 Å about N V 3479-3484, 4058 Å and N III 4634-4641, 5314 Å
weak or absent.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N IV 3479-3484, 4058 Å about N V 3479-3484, 4058 Å and N III 4634-4641, 5314 Å
weak or absent.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N IV 3479-3484, 4058 Å stronger than N V 3479-3484, 4058 Å and N III 4634-4641, 5314 Å weak or absent.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N IV 3479-3484, 4058 Å stronger than N V 3479-3484, 4058 Å and N III 4634-4641, 5314 Å weak or absent.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N III 4634-4641, 5314 Å as strong as N IV 3479-3484, 4058 Å as strong as N V 3479-3484, 4058 Å.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N III 4634-4641, 5314 Å as strong as N IV 3479-3484, 4058 Å as strong as N V 3479-3484, 4058 Å.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N III 4634-4641, 5314 Å about N IV 3479-3484, 4058 Å and N V 3479-3484, 4058 Å present, but weak.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N III 4634-4641, 5314 Å about N IV 3479-3484, 4058 Å and N V 3479-3484, 4058 Å present, but weak.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WNh type → Wolf-Rayet (→ WN6 star) with → absorption lines in its spectrum that have not been attributed to the presence of a → companion. For example → NGC 3603-A1.

See also: The letter “a” indicating → absorption; → WNh type.

A → WNh type → Wolf-Rayet (→ WN6 star) with → absorption lines in its spectrum that have not been attributed to the presence of a → companion. For example → NGC 3603-A1.

See also: The letter “a” indicating → absorption; → WNh type.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N III 4634-4641, 5314 Å stronger than N IV 3479-3484, 4058 Å, N III weaker than He II 4686 Å, He I weak with → P Cygni profile.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N III 4634-4641, 5314 Å stronger than N IV 3479-3484, 4058 Å, N III weaker than He II 4686 Å, He I weak with → P Cygni profile.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N III 4634-4641, 5314 Å very stronger than N IV 3479-3484, 4058 Å,
N III about He II 4686 Å, and He I with → P Cygni profile.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N III 4634-4641, 5314 Å very stronger than N IV 3479-3484, 4058 Å,
N III about He II 4686 Å, and He I with → P Cygni profile.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N III 4634-4641, 5314 Å stronger than N II 3995 Å, N IV 3479-3484, 4058 Å absent, He I with → P Cygni profile.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

A → WN Wolf-Rayet star whose spectrum shows the following emission line characteristics: N III 4634-4641, 5314 Å stronger than N II 3995 Å, N IV 3479-3484, 4058 Å absent, He I with → P Cygni profile.

See also: W, from → Wolf-Rayet; N, from → nitrogen; → star.

In theoretical models, a → Wolf-Rayet star without hydrogen at its surface (< 10^-5 in number) and with surface carbon abundance smaller than nitrogen abundance.

See also: W short for Wolf-Rayet star, N for → nitrogen, E for early.

In theoretical models, a → Wolf-Rayet star without hydrogen at its surface (< 10^-5 in number) and with surface carbon abundance smaller than nitrogen abundance.

See also: W short for Wolf-Rayet star, N for → nitrogen, E for early.

A → WN Wolf-Rayet star which is hydrogen rich. WNh stars are initially more massive and have lost relatively little mass compared to other WR stars. It is suggested that these types are core hydrogen burning → main sequence objects. The most massive stars currently known are all WNh stars rather than O-type main sequence stars.

See also: WN, from → WN Wolf-Rayet; h, from → hydrogen.

A → WN Wolf-Rayet star which is hydrogen rich. WNh stars are initially more massive and have lost relatively little mass compared to other WR stars. It is suggested that these types are core hydrogen burning → main sequence objects. The most massive stars currently known are all WNh stars rather than O-type main sequence stars.

See also: WN, from → WN Wolf-Rayet; h, from → hydrogen.

In theoretical models, a → Wolf-Rayet star with hydrogen at its surface (> 10^-5 in number). A star enters the Wolf-Rayet phase as a WNL, then may evolve through the sequence WNL → WNE, → WC, → WO. It can end its evolution at any of these stages.

See also: W short for Wolf-Rayet star, N for → nitrogen, L for late.

In theoretical models, a → Wolf-Rayet star with hydrogen at its surface (> 10^-5 in number). A star enters the Wolf-Rayet phase as a WNL, then may evolve through the sequence WNL → WNE, → WC, → WO. It can end its evolution at any of these stages.

See also: W short for Wolf-Rayet star, N for → nitrogen, L for late.