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The UV Spectra of the WELS

The UV Spectra of the WELS. Wagner L. F. Marcolino (1,2). Francisco Xavier de Araujo (2). Helson B. M. Junior (2,3). Eduardo S. Duarte (3). (1) Laboratoire d'Astrophysique de Marseille (LAM) - France. (2) Observatorio Nacional (ON/MCT) - Brazil.

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The UV Spectra of the WELS

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  1. The UV Spectra of the WELS Wagner L. F. Marcolino(1,2) Francisco Xavier de Araujo(2) Helson B. M. Junior (2,3) Eduardo S. Duarte (3) (1) Laboratoire d'Astrophysique de Marseille (LAM) - France (2) Observatorio Nacional (ON/MCT) - Brazil (3) Centro Federal de Educacao Tecnologica (CEFET) - Brazil Tübingen, September 2007

  2. Introduction: Central stars of planetary nebulae that are H-deficient (neglecting O(He),RCB stars, etc): ~ 2-5 objects! ~ 40 objects ~ 75 objects [WC]-PG 1159 Stars PG 1159 Stars Mixed spectrum (abs+ems) (Werner & Herwig 2006) Mainly C IV and He II absorptions (Wesemael et al. 1985;Werner et al. 1997)(about 15 have PN associated) [WR] – Wolf-Rayets Broad, strong emissions of He, C, O (Crowther et al. 1998; Acker & Neiner 2003) late-type [WR] => early-type [WR] => [WC]-PG1159 => PG 1159 => non DA white dwarfs (e.g. Acker et al. 1996; Pena et al. 2001; Werner et al. 1992; Hamann 1997) (other sequences are possible/needed !) Tübingen, September 2007

  3. The “weak emission line central stars” - WELS: - First mention to WELS : Aller & Keyes (1985) - The definition : Tylenda et al. (1993) - 77 objects were studied: 39 classified as [WR] and 38 as WELS DEFINITION: Weak emissions (compared to [WR] stars) emission at 4650A (N III + C III + C IV) C IV 5805 (weak emission or absent) C III 5696A (weak emission or absent) Tübingen, September 2007

  4. The “weak emission line central stars” - example: Tübingen, September 2007

  5. Informations, questions and confusions about the WELS: - There are about 50 WELS known (Tylenda et al. 1993; Parthasarathy et al. 1998; Gorny et al. 2004) - What is their evolutionary status ? - Parthasarathy et al. (1998) : WELS are [WC]-PG 1159 stars ! [WCL] => [WCE] => WELS => PG 1159 => non DA - Pena et al. (2001;2003): WELS are not descendants of the [WR] stars (v_exp) - PNe analysis: Some WELS could be progenitors of [WO] stars (Gesick et al. 2006) - Other recent works (e. g. Girard et al. 2007) - Their physical parameters (e.g. Teff, vinf, Mdot) and chemical abundances remain unknown. - Most works were done in the optical part of the spectrum: We do not know their UV ! Tübingen, September 2007

  6. The UV Spectra of the WELS Tübingen, September 2007

  7. The Ultraviolet Spectra of the WELS: - We retrieved all the data available from the IUE database: 20 WELS (42 spectra selected) - line identifications and measurements of Wλ and fluxes for all lines (stellar and/or nebular) - measured terminal velocities for all objects presenting P-Cygni profiles - compared the results obtained to the two prototypes [WC]-PG1159 stars: A30 and A78 Tübingen, September 2007

  8. The Ultraviolet Spectra of the WELS: Group (1): Presence of a strong P-Cygni profile of C IV 1549 average Wλ(CIV) ~ 6 Tübingen, September 2007

  9. The Ultraviolet Spectra of the WELS: Group (2): Presence of a weak C IV 1549 in P-Cygni average Wλ(CIV) ~ 1 Tübingen, September 2007

  10. The Ultraviolet Spectra of the WELS: Group (3): Absence of P-Cygni's Wλ(CIV) ≥ 100 Tübingen, September 2007

  11. The UV of the [WC]-PG 1159 stars: Considered the prototypes of the [WC]-PG 1159 class (Werner & Herwig 2006)Note the simultaneous presence of N V 1238, O V 1371 and C IV 1549 Typical UV of most of the WELS with P-Cygni's Tübingen, September 2007

  12. The three exceptions : NGC 6543, NGC 6567 and NGC 6572 WELS in fact resembling the [WC]-PG 1159 stars Note: NGC 6567 was already considered a [WC]-PG 1159 star (Hamann 1996) Tübingen, September 2007

  13. Terminal Velocities Calibration provided by Prinja (1994): “Determining hot star wind terminal velocities from low-resolution IUE data” (A&A, 289, 221) a1 = 883, a2 = 259, a3 = 3 for C IV 1549 a1 = 2723, a2 = 621, a3 = 18 for N V 1238 Tübingen, September 2007

  14. ` Results: values concentrated in ~1000-1500 km/s much higher values: ~3000 km/s (C IV) Tübingen, September 2007

  15. ` Results: Terminal velocities distribution of H deficient CSPN Bin width is 500 km/s. Data for [WR] and PG 11 59 stars are from Koesterke (2001). Tübingen, September 2007

  16. ` Results: Central stars temperature distribution – Gesicki et al. (2006) Tübingen, September 2007

  17. ` Conclusions from the UV analysis: 1) We found that the WELS can be divided in three groups 2) The WELS are distinct from A 30 and A 78 ([WC]-PG1159 stars) - A 30 and A 78 show intense and simultaneous P-Cygni's in N V 1238, O V 1371 and C IV 1549 - The WELS present weak or no O V 1371 (the same is true for N V in a few cases) - Terminal velocities considerably lower than in [WC]-PG1159 stars - The situation is ambiguous for NGC 6543, NGC 6567 and NGC 6572 The question remains: What is their evolutionary status ? Tübingen, September 2007

  18. Quantitative analysis of WELS Tübingen, September 2007

  19. ` CMFGEN models for the WELS: Optical : ESO 1.52m Telescope (resolution of ~2Å) IUE satellite (resolution ~6Å) Tübingen, September 2007

  20. ` Preliminary results for Hen 2-12: - Very low mass-loss (about 10-9 solar mass/year) - Teff lower (< 100kK) than in A 30 and A 78 and in [WO] stars - Regarding the 4650Å feature: N V absorptions on its side ! N III lines could not be reproduced - More work under way... Tübingen, September 2007

  21. Hey, I know what the WELS are ! yeah, right! THANKS !

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