Be/X 線連星
線連星A0535+262
A0535+262 において2009年に起きた
2009
年に起きたgiant
giant outburst 時の時のBe
Be星ガス円盤の構造
星ガス円盤の構造
森谷友由希(1)、野上大作(1),、岡崎敦男(2)、 今田明(3)、 神戸栄治(3)、本田敏志(1)、橋本修 (4) 、市川幸平(1)1) 京都大学

2) 北海学園大学

3) 岡山天体物理観測所

4) ぐんま天文台

We report on high-dispersion optical spectroscopic observations of the Be/X-ray binary A0535+262/V725
Tau during a giant outburst in November/December 2009, and after it. The observed emission line profiles,
reflecting the structure of the geometrically thin circumstellar envelope of the Be star (Be disc), show drastic
variabilities, and indicate the existence of a warped component. The enhanced blue shoulder seen after periastronpassage implies a gas stream from a dense part of the Be disk to the neutron star.
(Moritani et al. 2011, PASJ, 64, L15)

1.Be/X‐
1.Be/X‐ray binariesii

2.A0535+262/ V725 Tau

・Be star + compact object (NS)・O9.7IIIe + NS, mV:8.9 mag (Giangrande+ 1980, A&AS, 40, 289)
・One of the main subgroups of HMXRBs Fig. 1: Be/X ray binaries ・Porb = 110.24 days (Moritani+ 2010, MNRAS, 405,467)(Okazaki+ 2002, MNRAS, 337, 967) ・e ~ 0.47 (Finger+ 1994, AIPC, 308, 459)
・3 states:
1. Quiescent LX‫د‬1036 erg/s
・NS: 103-sec. pulsar (Caballero+ 2007, A&A, 465, L21)
2. Normal (type I) outburst LX～1036-37 erg/s
・6 giant outburst have been observed;
・Orbital modulation
3. Giant (typeyp II) outburst LX‫ذ‬1037 erg/sg
・Less frequently than normal outbursts

in 1975, 1980, 1991, 1996, 2005, 2009 and 2011

・GiantGiant outburst in Nov
Nov.// Dec
Dec. 2009* Precursors in Oct. (Sugizaki+ 2009, Atel. #2277)* Rapid brightening at 30 Nov. (JD 2455166)* > 3 Crab at the peak in 15-50 keV (Krimm+ 2009, Atel. #2336)

・Be
Be stars (B emission stars):* B stars which have exhibited Balmer lines in emission atleast once (Luminosity class III-V)* Equatorial region … weak outflow(‫ د‬1 km/s), balance
between the surface gravity and the centrifugal force due
to rapid rotation (‫د‬several 100 km/s)* geometrically thin circumstellar envelope: Be disc
188cm tel.
tel @OAO

・Normal outbursts after the giant outburst* precursor … outburst in March and July in 2010
* no precursor … outburst in October 2010
* X-ray peak shift in October 2010

・Giant outburst in Feb. 2011

* ~ 500 days after the giant outburst in 2009

3.Observations

Fig. 2: X-ray light curve by MAXI/GSC (2-10 keV, bottom), and equivalent width(middle) and normalized intensity of the peak (top) of the Hα lines .
Vertical dotted lines: estimated periastron (Moritani+ 2010, MNRAS, 405, 467)
Short arrows: HJD of representative spectra in Fig.3
Horizontal blue line: the radius of the Be disc ~ Roche lobe radius-OAO/HIDES, GAO/GAOES…optical Echelle spectrograph(RR ~ 50,000, S/N ~ 100100))-Wavelength and Lines;*OAO/HIDES:3800 – 6700 Å*GAO/GAOES:4800 – 6700 Å

1 5m tel
1.5mtel. @GAO

-First optical (high-dispersion)
spectroscopic observation covering
the giant outburst!!

HαHe Iλ5876

4.Results & Discussion-Equivalent width is highest in thelast 5 years
Grundstrom+ 2007
2007, ApJ, 660,660 1398:

giant outburst*Relationship between EW(Hα) and theradius of the Be disc
*Roche lobe radius (~ 5R*) … - 10Å⇒Warping component! in the Be disc?

-Observed line profiles (Fig.3) show
drastic variabilities
Blue hump:*A bright
g humpp seen in the blue wingg*Radial velocity and intensity changed

Fig. 3:Representative spectra ofHα and He I λ5876

Redshifted enhanced component:*Triple peak
*Already seen in Aug. 2009 (after twopeak outburst)⇒Warping component in the Be disc?

Orbital phase when the blue
shoulder can be seen
seen.. Blueshoulder suggests the gas
stream from Be disc to theNS (orange arrowarrow))

Blue shoulder:-High E/C (normalized intensity ofthe peak) via enhanced component

54B

2009.11.30
2455166.233
φX = 0.0359

Blue shoulder can be seen
only after periastron passage
5C

4.5
45
2009.12.06
2455172.033
φX = 0.0886

4.5
4

3.5

3.5
Fλ/Fc

3
2.5

3
2.5

32.5

222

1.5

1.5

1.5

11

1

0.5

0.5
-400 -300 -200 -1000φX = 0.039
Giant outburst rise

0.5-400 -300 -200 -100 0 100 200 300 400 500
wevelength [km/s]

100 200 300 400 500

wevelength [km/s]

φX = 0.072

D2009.12.12
2455178.107
φX = 0.143

3.5
Fλ/Fc

4.5

Fig. 5:Geometry of A0535+262.
Cyan circle: Be photosphere
Orange ring: Be disc with the Roche lobe radius)Fig. 4:Line profiles with blue shoulder
during the giant outburst in 2009

φX = 0.808

Fλ/Fc*Only seen after periastron (Fig. 4)
d i thduringthe gianti t outburst
tb t iin 2009 anddthe normal outburst in Mar. 2010
*Radial velocity: ± 0 km/s
⇒Gas stream from Be disc to the NS(accretion disc)?

gas stream

φX = 0.089
Giant outburst peak-400 -300 -200 -100 0 100 200 300 400 500
wevelength [km/s]

φX = 0.143

D