High-Energy Emission from Young and Massive Stellar Objects Gustavo E. Romero IAR-CONICET [email protected] Felix Aharonian’s Workshop November 7 th , 2012
Feb 23, 2016
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 .
Herbig-Haro objects
HH49-50
HH 80-81: a partially embedded massive protostellar system
Martí, Rodriguez & Reipurth (1993)
B = 0.2 mG,
Carrasco-González, Rodríguez et al. 2010
Polarization in the jets
Interaction with the ISM
The whole source (protostar + jets) is embedded in the molecular cloudAraudo, Romero, Bosch-Ramon & Paredes 2007, A&A 476, 1289
SED for HH 80-81
a=100Bosch Ramon et al. (2010), ncloud = 103/cm3.
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
Case dominated by protons
Araudo et al. (2007)
3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red)
Westerlund 2/ RCW 49
Aharonian, F.A., et al., 2006
Westerlund 2/ RCW 49
HESS Collaboration
Westerlund 2/ RCW 49
PSR J1022-5746
Westerlund 2/ RCW 49
Expected size of the PWN
Size of HESS J1023-575
Additional contributions?
HESS Coll.
K&C 1984
RCW 49 / Westerlund 2Be
nagl
ia e
t al.
2012
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
E-BOSS v.128 cands (out of 283 OB runaway stars known)
Peri,
Ben
aglia
, et a
l. 20
12, A
&A
Modeling bow-schocks and their emission
Relativistic particles are accelerated at the reverse adiabatic shock in the stellar wind
Modeling bow-schocks and their emission
Most of the protons escape
del Valle & RomeroIn prep.
These p can power the extended source
del Valle & Romero 2012, A&A
Spectral energy distributions for O4I and O9I stars
Another case: Westerlund 1
HESS Coll.
Another case: Westerlund 1
See also poster by Martí et al. on Monoceros
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
VLA + MSX images of
BD+43o 3654
C band
L band
Bena
glia
, Rom
ero,
et a
l 201
0, A
&A
SEDBe
nagl
ia, R
omer
o, e
t al 2
010,
A&A
z Oph bow-shock
Computed BS & WISE image
SED and sensitivities
del V
alle
& R
omer
o 2
012,
A&A
Is HD 195592 a Fermi source?del Valle, Romero, & De Becker 2012
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.
Thanks!
What a world!
“Relaxed gamma-ray astronomy team”
Gamma rays from massive stars: not a new idea
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
HH 80-81: the central source
Martí, Rodriguez & Reipurth (1993)
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,
Ben
aglia
, et a
l. 20
12, A
&A
Distributions
detected BS
GC
Peri, Benaglia, et al. 2012, A&A
Benaglia et al. 2012
Absorption
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 kpco 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?
MSX emission toward BD+430 3654
D-band image (14.65 mm)
VLA obs
L-band
C-band
Bena
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, Rom
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Images
Is al
l em
niss
ion
com
ing
from
the
BOW
SH
OCK?
5’ ~ 2pc
Bena
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, Rom
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Spectral index mapa
noise
S(n) ~ k na
s/n (cont) ≥ 4
s/n (a) ≥ 10
-0.8 ≤ a ≤ 0.3.
<a> -0.4Bena
glia
, Rom
ero,
et a
l 201
0, A
&A
AE AuriageLópez-Santiago, Miceli, del Valle, Romero, et al. ApJ Lett 2012
Eemax~1 TeV