1. 赤外線天文衛星「あかり」による 新星の近赤外分光観測
左近　樹、尾中 敬、田中雅臣、守屋 尭(東京大学)、
新井彰、植村誠、川端弘治 (広島大学)
AKARI IRC チーム、新星サイエンス検討チーム、

2. 新星
古典新星 (Gehrz et al. 1998)
-- a phenomenon resulting from the accretion of matters in the atmosphere
　　of red-giant or red-dwarf companion onto the white dwarf.
Observed Nova rate in the Galaxy ; 35±11yr-1 (Shafter 1997)
The mean mass returned by a nova outburst into the ISM; 2x10-4M☉
 7x10-3M☉ yr-1 of processed matter is ejected by novae into the ISM
cf. Supernovae rate ~0.02yr-1 in a galaxy
The mean mass returned by a supernova into the ISM; 3M ☉
 0.06 M☉ yr-1 of processed matter is ejected by supernova into the ISM
宇宙の化学進化に対する新星の貢献
・Less than ~0.3% of the interstellar matter in the Galaxy
・Only about 0.1% of the Galactic “stardust”
・a significant fraction of the 26Al (t1/2~7.2 x 105yr) that exists in Galactic matter
Theoretical studies suggest that large amount of 22Na and 26Al can be produced
in outbursts of ONeMg WDs (Weiss & Truran 1990; Nofar et al. 1991);
 possible candidates that are responsible for the 22Ne (Black 1972) and
26Mg (Truran 1985) anomalies found in meteorites (Gehrz et al. 1998)

3. 新星の赤外線観測 CO Novae および ONeMg Novae の赤外スペクトル進化
Hot ejecta gas is initially seen as an expanding photosphere or “fireball”
When the expanding material becomes optically thin, free-free and line emission dominate
1). CO Novae; 比較的低質量(e.g., MWD<1.1M☉)のCO 白色矮星
　　　　　の表面上での熱核暴走(thermonuclear runaway ;TNR)
- いくつかのケースでfree-free 期に続いてダスト形成が報告
　 (e.g., V2362 CYGNI; Lynch et al. 2008)
2). ONeMg Novae; 比較的質量の大きな(e.g., MWD>1.1M☉)の
　　　　　ONeMg 白色矮星の表面上での熱核暴走(TNR)
- free-free 期に引き続いて coronal emission-line 期を迎える
- いくつかの例外を除いて観測的にダスト形成の報告は
　　　ほとんどない (e.g., V1974 CYGNI; Woodward et al )

4. 赤外線天文衛星「あかり」 JAXA/ISAS mission for infrared astronomy
with ESA participation
Telescope with 685mm SiC Mirror
cooled by 179l LHe
& mechanical coolers
2 instruments: IRC & FIS
Launched on Feb. 22, 2006
Successfully performed near-
to far-infrared observation
LHe: 2006 May Aug
(phases I&II)
Warm mission: 2008 June –
(phase III; 2-5mm imag. & spec.)

5. 「あかり」衛星 近・中間赤外線カメラ 近赤外分光素子の波長透過率特性 NIR dispersers
AKARI’s spectroscopic ability in the near-infrared
in the warm mission is quite unique and valuable
Two Near-Infrared Dispersers
with different spectral resolution power
Near-Infrared Prism (NP)
Near-Infrared Grism (NG)
Effective Coverage Dispersion
NP mm-5.5mm 　 mm/pix at 3mm
NG mm-5.0mm mm/pix
The 1-s noise-equivalent flux
for slit-less spectroscopy at the ecliptic poles
Phases I&II Phase III
NP ~0.05mJy ~0.1mJy
NG ~0.1mJy ~0.2mJy

6. あかり衛星による新星の観測 Phase 3-II AKARI Open Time Program:
Spectral Evolution of Novae in the Near-Infrared
based on AKARI Observation (SENNA; PI: I. Sakon)
Discovery approved observation schedules
phase 3-II-1# phase 3-II-2#2
V1213 CENTAURUS Mar ○ ○
V5582 SAGITTARII Feb 2009 　　　　　　　　 × ○
V679 CARINAE Nov 2008　　　　　　　　 ○　　　　　　　　　 ○
V5580 SAGITTARII Nov × ○
QY MUSCAE Sep ○ ○
V1309 SCORPII Sep 2008　　　　　　　　　○ ○
V2468 CYGNI Mar ○ ○
V5579 SAGITTARII Apr 2008　 ○ ○
V1280 SCORPII Feb × ○
#1 Oct – Feb. 2010, #2 Mar. 2010– Sep. 2010
・Continuous 2.5—5mm spectra taken with AKARI/IRC are quite unique
・Collaborative optical (B,V,R) to NIR(J, H, Ks) observations with TRISPEC on the 2m KANATA telescope of Hiroshima University and with other ground-based facilities are important

7. あかり衛星によるV2468 CYGNIの近赤外分光観測
Nova V2468 CYGNI (R.A., DEC. [J2000]) = (19:58:33.57, +29:52:11.6)
2008年3月に発見 (Munari et al. 2008, Cent. Bur. Electron. Tel. 1431, 1)
Multi-epoch NIR spectroscopic observations of V2468 CYGNI with AKARI/IRC
First observation; on 2nd Nov., 2008 (t~240days; hereafter first epoch)
Second observation; on 1st May, 2009 (t~420days; hereafter second epoch)
Both observations were carried out in the framework of AKARI Director’s Time
Pointing ID’s; (Nov., 2008), & (May, 2009)
Near-Infrared Grism (NG) is used to obtain the 2.52mm-5.0mm spectra
with a resolution of R(=l/Dl)~80
N3 band reference image of V2468 CYGNI
on 2nd NOV. 2008
Raw NG data of V2468 CYGNI on 2nd NOV. 2008
N3 band reference image of V2468 CYGNI
on 1st May. 2009
Raw NG data of V2468 CYGNI on 1st May. 2009

8. あかり衛星によるV2468 CYGNIの近赤外分光観測
1回目のV2468 CYGNIの近赤外分光観測 (2nd Nov., 2008; t~240 days)

9. あかり衛星によるV2468 CYGNIの近赤外分光観測
2回目のV2468 CYGNIの近赤外分光観測 (1st May., 2009; t~420 days)

10. Bra 4.05mm lineのライン形状
Signal count profile of the Bra line in the spectrum of May 2009
平均的な放出ガスの視線速度成分は420日後の時点で~ km s-1

11. あかり衛星によるV2468 CYGNIの近赤外分光観測
Strength of Hydrogen recombination lines (10-16W/m2);
Epoch Bra(4.05mm) Brb(2.63mm) Pfg(3.74mm) Pfb(4.65mm)
Nov ± ± ± ±0.4
May ± ± ± ±0.40
Relative Strengths of Hydrogen recombination lines
Epoch Brb/Bra Pfg/Bra Pfb/Bra
Nov ± ± ±0.020
May ± ± ±0.080
Free-free continuum emission
Fn ~ 30mJy (on 240 days), ~12mJy (on 420 days)

12. あかり衛星によるV2468 CYGNIの近赤外分光観測
電子温度; Te ~数千度 K
電子密度; ne ~109 cm-3 (on 240 days), ~1011cm-3 (on 420 days)
(Case B; Osterbrock 1989; Hummer & Strey 1987; Storey & Hummer 1995)

13. あかり衛星によるV2468 CYGNIの近赤外分光観測
“coronal” lines の強度 (10-16W/m2);
[CaIV] [CaV] [MgIV] [AlV] [AlVI]
lc (mm)
eion (eV)
eex (eV)
Nov ± ± ±
May ± ± ± ± ±0.11
基本的には典型的なONeMg 新星の
近赤外スペクトル進化と一致;
-- free-free emission line phaseの終了段階
　に近づくにつれてwind fluxは落ちる
--光学厚さ t~1で決定される半径が後退
白色矮星の光球のより深く熱い層が
　見えるようになる。(i.e., Lynch et al. 2008)

14. あかり衛星によるV1280 Scoの近赤外分光観測
V1280 Scorpii;
-Discovered on 2007 Feb 4.86
by Y. Nakamura and Y. Sakurai
(Yamaoka et al. 2007)
Dust formation occurred after
d~23days (Das et al. 2007)
2009年9月9日にあかり衛星の近・中間赤外線カメラによる近赤外分光観測を遂行
右上がりの連続光放射に加えて、強い長波長側のwingを有する顕著な PAH 3.3mmバンド放射を検出
The late time near-Infrared Spectrum
of V1280 Sco obtained with AKARI/ IRC on ~940 days after the discovery.
※比較的大きな3.4mm/3.3mmのバンド強度比がV842 Cenでも観測。 (Hyland & McGregor 1988)

15. 赤外線波長域に見られるPAH featureの性質
Unidentified Infrared (UIR) Bands
Polycyclic Aromatic hydrocarbons
(PAHs; Allamandola et al. 1989)
3.3mm feature; aromatic C-H stretch mode
3.4mm feature; aliphatic C-H stretch mode
UKIRTで取得されたOrion Barの電離領域(上)　と中性領域(下) の近赤外スペクトル (Sloan et al. 1997)

16. あかり衛星によるV1280 Scoの近赤外分光観測
Red wing in mm
-- PAHについたaliphatic side groupから
のC-H strech の振動モードの放射
(Jourdain de Muizon et al. 1990)
-- いくつかのHerbig Ae/Be天体やNova
Cen1986
Near infrared spectrum of NGC1333
with UKIRT (Joblin et al. 1996)
Novaに見られるhydrocarbon featureがHydrogenated amorphous carbonによって担われている(Evans & Rawlings 1994)という主張に一貫
- 化学進化の観点からのHydrogenated amorphous carbon と PAHs との関連に関する重要な情報
AKARI Near infrared spectrum of
V1280 Sco at the epoch of 980 days

17. Summary　
(1) Multi-epoch NIR spectroscopic observations of V2468 CYGNI were carried out with AKARI Infrared Camera (IRC) in the framework of AKARI Director’s Time First epoch; on 2nd Nov., 2008 (t~240days) Second epoch; on 1st May, 2009 (t~420days) ・The NIR spectrum on first epoch is characterized by strong hydrogen and helium recombination lines and “coronal” lines of [CaIV], [CaV] and [MgIV] ・The NIR spectrum of second epoch is characterized by relatively weaker hydrongen recombination lines and strong [MgIV], [CaIV], [CaV] together with the lines with higher ionization potential such as [AlV] and [AlVI] (eip>100eV)  No significant signs of dust formation have been found for V2468 CYGNI  Consistent with the typical evolution scenario of ONeMg Novae (2) NIR spectroscopic observations of V1280 Scorpii were carried out With AKARI IRC in the framework of AKARI Director’s Time First epoch; on 9th Sep., 2009 (t~940 days) ・ Clear signs of PAH 3.3mm band accompanied by a strong red-tail in mm arising from the aliphatic C-H bonds  consistent with the scenario that hydrocarbon features in novae are carried by hydrogenated amorphous carbon (HAC) (Evans & Rawlings 1994)