High-Energy Emission from Young and Massive Stellar Objects

Gustavo E. RomeroIAR-CONICET

romero@iar-conicet.gov.ar

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 2B

en

ag

lia e

t al. 2

01

2

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

, B

en

aglia

, et

al. 2

012

, 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

Benaglia

, R

om

ero

, et

al 2010,

A&

A

SEDB

enaglia

, R

om

ero

, et

al 2010,

A&

A

z Oph bow-shock

Computed BS & WISE image

SED and sensitivities

del Valle

&

Rom

ero

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

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aglia

, et

al. 2

012

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&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 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?

MSX emission toward BD+430 3654

D-band image (14.65 mm)

VLA obs

L-band

C-band

Benaglia

, R

om

ero

, et

al 2010,

A&

A

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

AE AuriageLópez-Santiago, Miceli, del Valle, Romero, et al. ApJ Lett 2012

Eemax~1 TeV