1. 「 Subaru UM 」 ＠ NAOJ, 30 Jan 2008 Supernovae are NOT spherical: The result from late-time spectroscopy by FOCAS “Asphericity in Supernova Explosions from Late-Time Spectroscopy”, Keiichi Maeda et al., Science, 31 January issue (online version) Keiichi Maeda (@MPA → IPMU) MPA: Max-Planck-Institute for Astrophysics IPMU: Institute for the Physics and Mathematics of the Universe 1/15

2. 「 Subaru UM 」 ＠ NAOJ, 30 Jan 2008 Collaborators K. Maeda (MPA/IPMU) K. Kawabata (Hiroshima) P.A. Mazzali (MPA/Trieste) M. Tanaka (Tokyo) S. Valenti (ESO) K. Nomoto (Tokyo/IPMU) T. Hattori (Subaru) J. Deng (NAOC) E. Pian (Trieste) S. Taubenberger (MPA) M. Iye (NAOJ) T. Matheson (Tucson) A.V. Filippenko (UC Berkeley) K. Aoki (Subaru) G. Kosugi (NAOJ) Y. Ohyama (JAXA) T. Sasaki (Subaru) T. Takata (NAOJ) 2/15

3. 「 Subaru UM 」 ＠ NAOJ, 30 Jan 2008 Core-Collapse Supernovae (CC-SNe) (23rd Feb. 1987) The end product of a massive star （ M > 8 M  ） Core-collapse  Explosion （ E ~ 10 51 erg ） Origin of heavy elements. My talk is especially on “stripped” CC-SNe. –A subclass, a progenitor has lost its H envelope before the explosion. SN 1987A (not stripped)

4. 「 Subaru UM 」 ＠ NAOJ, 30 Jan 2008 The explosion mechanism(s) of Core-Collapse Supernovae (CC-SNe)? The explosion geometry of CC-SNe? Questions “Easier” questions 4/15

5. 「 Subaru UM 」 ＠ NAOJ, 30 Jan 2008 Why geometry? Theoretical scenarios –SASI, rotation, MHD, Collapser…(and so forth) (Some) Proposed scenarios predict bipolar explosions. The geometry is closely related to the explosion mechanism. Blondin+ 2003Kotake+ 2004MacFadyen & Woosley 1999 5/15

6. 「 Subaru UM 」 ＠ NAOJ, 30 Jan 2008 OK. Geometry seems important. But HOW CAN YOU LOOK INTO THAT? An SN is observed as a point source. –Only very few exceptions (e.g., 87A) Late-time spectroscopy (~ 1 year after the explosion)! –Optically thin (expansion) + simple velocity law (v ∝ r). 6/15 blueshift redshift wavelength

7. 「 Subaru UM 」 ＠ NAOJ, 30 Jan 2008 Spherical models ANY spherical distribution should produce “SINGLE-PEAKED” [OI] 6300&6363. –6363A component negligible at late-phase. –Negligible transfer effect to distort the line profile. –Irrespective the radial density distribution, you always have the maximum cross section at the supernova center. The line should peak at the rest wavelength. 7/15

8. 「 Subaru UM 」 ＠ NAOJ, 30 Jan 2008 Subaru/FOCAS Observation Spectroscopy@200day. –Faint (R ~ 20 – 24 mag). –Often fainter than a background diffuse HII region. ~ 0.5 – 4 hr by 8m! Subaru/FOCAS (+ VLT)! –KM, KK, MT + TH, KA. After subtracting possible biases (later), 15 SNe. Previously, only 3 SNe. 18 SNe = 6 times the previous sample!!! Previous This work 8/15

9. 「 Subaru UM 」 ＠ NAOJ, 30 Jan 2008 Observational Result Discovery of the double-peaked [OI] in at least 5 SNe (at most 9) out of 18. The double-peak is NOT an unusual features! Asphericity is a common feature in SNe!! 9/15

10. 「 Subaru UM 」 ＠ NAOJ, 30 Jan 2008 To be more quantitative: Aspherical models BP16 8 4 2 1 ρ 56 Ni(Fe) Ca O Spherical Fe ( 56 Ni) O At observations （＞ 1day ） A sequence of phenomenological (parameterized) models. Params.: BP (Asphericity), θ 10/15 Maeda+ 02, ApJ, 565, 405 Oxygen distributed in a disk.

11. 「 Subaru UM 」 ＠ NAOJ, 30 Jan 2008 Statistics of the [OI] profile! O < 30 o Z ： 0 deg R ： 90 deg 0 deg 30 deg 60 deg 90 deg Expected frequency 36% Singly Peaked Maeda+ 06, ApJ, 640, 854 Extreme Model BP8 Expected frequency 64% Doubly Peaked 11/15

12. 「 Subaru UM 」 ＠ NAOJ, 30 Jan 2008 Statistics of the [OI] profile BP8 = 64% double-peaked, BP2 = 34%, BP1 = 0%. BP8 vs BP2 double vs. single BP16 8 4 2 1 ρ 56 Ni(Fe) Ca O Spherical 12/15

13. 「 Subaru UM 」 ＠ NAOJ, 30 Jan 2008 Asphericity is a common feature, but HOW? Double peaked fraction = 28 – 50% (median 39%). –Uncertainty comes from “transitional” profiles. vs. BP8 predicts 64%, BP2 = 34%, and BP1 = 0%. Most, if not all, CC-SNe are NOT spherical. On average, CC-SNe are moderately aspherical. 13/15

14. 「 Subaru UM 」 ＠ NAOJ, 30 Jan 2008 Interpretation: Geometry of CC-SNe Average geometry of CC-SNe, Moderately aspherical. First observational support of recently proposed explosion scenarios. 14/15

15. 「 Subaru UM 」 ＠ NAOJ, 30 Jan 2008 Conclusions & Implication Core-collapse SNe do have asphericity. –Mildly(?) aspherical (consistent with model BP2). Not discussed in this talk, but important implication. –The average asphericity looks smaller than special, energetic SNe (Hypernovae). Previous study indicates a geometry similar to BP8 for a very ebergetic SN 1998bw (associated with a Gamma-ray burst). 15/15 Maeda+ 06, ApJ, 640, 854; Maeda 06, ApJ, 644, 385; Maeda+ 06, ApJ, 645, 1331; Tanaka+ 07, 668, L19