gustavo e. romero iar-conicet [email protected] felix aharonian’s workshop november 7 th,...
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High-Energy Emission from Young and Massive Stellar Objects
Gustavo E. RomeroIAR-CONICET
Felix Aharonian’s Workshop November 7th, 2012
What are the contents of star-forming regions?
Gas (Hayakawa 1952, Morrison 1958, Aharonian & Atoyan 1996). Young, massive stars with winds collective effects
(Bykov & Fleishman 1992, Romero & Torres 2003, Torres et al. 2004, Parizot et al. 2004, Bykov: yesterday, etc).
Young pulsars. SNRs (yesterday’s talks). Colliding wind binaries (Eichler & Usov 1993, Benaglia &
Romero 2003, Pittard & Daugherty 2006). Accreting sources (Paredes, Mirabel, Bosch-Ramon – this
workshop). FORMING MASSIVE STARS. RUNAWAY MASSIVE STARS.
Massive stars are formed in massive and dense cores of giant molecular clouds. The cores are the result of the gravitational fragmentation of the cloud
The mechanism of massive star formation is still matter of debate. There are two main different scenarios: accretion and coalescence .
Interaction with the ISM
The whole source (protostar + jets) is embedded in the molecular cloudAraudo, Romero, Bosch-Ramon & Paredes 2007, A&A 476, 1289
The massive protostar IRAS 16547-4247
VLA Rodríguez et al. (2005)
Southern lobe:
S=cte na,a~ -0.6
d=2.9 kpc
B~10-3 G
Vs~1000 km/s
Clear non-thermal emission
SEDs of non-thermal region at the end of the jet
Araudo, Romero, Bosch-Ramon & Paredes 2007, A&A 476, 1289
3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red)
Westerlund 2/ RCW 49
Westerlund 2/ RCW 49
Expected size of the PWN
Size of HESS J1023-575
Additional contributions?
HESS Coll.
K&C 1984
Stellar bow shocks
• Arc-shaped features of piled-up material• Same direction as stellar velocity• Winds confined by ISM ram pressure • Distance to star by momentum balance• Radiation from shocked gas heats
swept dust• Dust re-radiates as MIR and FIR excess
Modeling bow-schocks and their emission
Relativistic particles are accelerated at the reverse adiabatic shock in the stellar wind
AE AuriageLópez-Santiago, Miceli, del Valle, Romero, et al. ApJ Lett2012
Absorbed X-ray power law ~ -2.5
AE AuriageLópez-Santiago, Miceli, del Valle, Romero, et al. ApJ Lett 2012
WISE + 1-8 keV EPIC map Energy map
Conclusions
* Protostars in SFRs can be gamma-ray sources when embedded in the original molecular core.
* The typical luminosities are ~ 1031-33 erg/s at E>100 MeV.
* Runaway massive stars can produce relativistic particles in their bowshocks, and local (IC) and difusse (pp) gamma-ray emission.
* Some nearby runaway O stars can be detected in gamma-rays by Fermi and in the future by CTA.
Gamma-ray astronomy can open a new window to the study of massive star forming processes.
Some basic parameters for HH 80-81
vj ~ 700 km/s n ~ 1000 cm-3
RHH ~ 5 1016 cm D ~ 1.7 kpc LX ~ 4 1031 erg/s Beq ~ 5 mG E max, p ~ 3 1014 eV - E max, e ~ E max, p/12
See Martí et al. (1993) and Pravdo et al. (2004) for details on the source
Distributions
0
10
20
30
40
50
60
10 20 30 50 70 90 130
Number of stars vs. Spatial velocity
Tetzlaff + 2010Km/s
#
Peri
, B
en
aglia
, et
al. 2
012
, A
&A
Energy losses and gains
tpp ~ 2 1012 s >> tesc ~ 3 109 s
tBremsstr ~ 3 1013 s
tacc ~ η E/qBc, where η =(8/3)(vs/c)2
tesc = tacc 3 1014 eV (for protons)
The star BD+43o 3654
IRAS bow shock candidates (Noriega-C. et al. 1997)
Comerón & Pasquali 2007:o Bow shock at MSX-D, E bandso Runaway from Cyg OB2, 1.4 kpc
o O4 If ; 70 Mo ; 1.6 Myr; [vw = 3200 km/s]
Kobulnicky et al. 2010:
o v ~ 80km/s, dM/dt ~ 2 x 10-4 Mo/yr
Ambient density: 6 to 100 cm-3 A non-
thermal emitter?
Images
Is a
ll em
nis
sion c
om
ing f
rom
th
e
BO
W
SH
OC
K?5’ ~
2pc
Benaglia
, R
om
ero
, et
al 2010,
A&
A
Spectral index map
a
noise
S(n) ~ k na
s/n (cont) ≥ 4
s/n (a) ≥ 10
-0.8 ≤ a ≤ 0.3.
<a> -0.4Benaglia
, R
om
ero
, et
al 2010,
A&
A