Multi-wavelength studies of hot-star magnetospheres

Mary Elizabeth OksalaLESIAParis-Meudon Observatory

CFHT UMNice, FranceMay 3, 2016

1

What are massive stars?

M � 8 M�

T � 15000 K

L = 104 � 106 L�

M = 106 � 108 M�

RADIATELY-DRIVEN STELLAR WIND

Credit: NASA, ESA/Hubble and the Hubble Heritage Team

Rosette Nebula © Juan Ignacio Jimenez

2

What if we add a magnetic field?

3

Massive-star magnetism

0.3 - 20 kG

Simple, Stable, Global

Strong stellar wind

Mass loss

4

© A. ud-Doula © R.H.D. Townsend

! I)+�

"A'J3#'K'

! I)+�

"A'J3#'K'

Si XIVMg XII

H-like / He-like

Si XIIIMg XII

Gagné et al. 2005

–1000 –500 0 500 1000 1500

1544 1548 1552

02460

2

4

6

8

10

Velocity (km s–1) (stellar rest frame)

σob

s/σex

pFl

ux (1

0–11 e

rg c

m–2

s–1Å

–1)

Wavelength (Å)HD 184927 C IV

IUE 30 spectra

B2V He strongP = 9.5 dBp ≈ 1 kG

–1000 –500 0 500 1000 1500

1544 1548 1552

0240

2

4

6

Velocity (km s–1) (stellar rest frame)

σob

s/σex

pFl

ux (1

0–10 e

rg c

m–2

s–1Å

–1)

Wavelength (Å)α Scl HD 5737 C IV

IUE 29 spectra

B7IIIpHe weakP = 21.6 dBp ≈ 300 G

–1000 –500 0 500 1000 1500

1544 1548 1552

024680

1

2

3

4

Velocity (km s–1) (stellar rest frame)

σob

s/σex

pFl

ux (1

0–9 e

rg c

m–2

s–1Å

–1)

Wavelength (Å)β Cep HD 205021 C IV

IUE 81 spectra

B1 IVpulsatingP = 12 dBp ≈ 300 G

–1000 –500 0 500 1000 1500

1544 1548 1552

02460

1

Velocity (km s–1) (stellar rest frame)

σob

s/σex

pFl

ux (1

0–10 e

rg c

m–2

s–1Å

–1)

Wavelength (Å)V2052 Oph HD 163472 C IV

IUE 41 spectra

B2IV/VpulsatingHe strongP = 5.4 dBp ≈ 250 G

–1000 –500 0 500 1000 1500

1544 1548 1552

01230

1

2

3

Velocity (km s–1) (stellar rest frame)

σob

s/σex

pFl

ux (1

0–9 e

rg c

m–2

s–1Å

–1)

Wavelength (Å)ζ Cas HD 3360 C IV

IUE 103 spectra

B2 IVSPBP = 3.6 dBp ≈ 350 G

–1000 –500 0 500 1000 1500

1544 1548 1552

0

2

40

Velocity (km s–1) (stellar rest frame)

σob

s/σex

pFl

ux (1

0–9 e

rg c

m–2

s–1Å

–1)

Wavelength (Å)σ Lupi HD 127381 C IV

IUE 4 spectra

B1/B2VHe strongP = 3.0 dBp ≈ 350 G

Courtesy of H. Henrichs

X-ray

UV

Leto et al. 2012

Radio

Diagnostics

5

σ Ori E

Optical+IR diagnostics

Courtesy of J. Grunhut

Br 10 1.73 microns

* INFRARED + OPTICAL

Oksala et al. 2015

ESPaDOnS@CFHT

Narval@TBL

OSIRIS@SOAR

Hα

Grunhut et al. 2012

Pa13

6

HR 5907

The serendipitous detection of a CM star

7

Eikenberry et al. 2014

HD 23478

σ Ori E

IR

Sikora et al. 2015

Optical Magnetic field confirmed by:

Sikora et al. 2015 ESPaDOnS@CFHT

Hubrig et al. 2015 FORS2@VLT

8

Optical Spectropolarimetry

HD 23478 ESPaDOnS@CFHT

Narval@TBL

Obtained 2014-2016

Phase (P=1.0498 d)

Bl (k

G)

Velocity (km/s)

LSD I/Ic 30*LSD V/Ic

9

HD 23478Magnetosphere variations

nm

Norm

alize

d flu

x

Bl (k

G)

Phase (P=1.0498 d)

10

NIR spectroscopy

GNIRS@GEMINI

• Short camera (30” slit)

• R ~ 6000 — intermediate

• Cross-dispersed — 0.78-2.3 microns

• Time series of 9 spectra, covering the 1.0498 d rotation period

microns

Flux

11

Magnetosphere diagnostics

Hα

Brɣ

Br13

Paβ

0.1 0.21 0.32 0.44 0.55 0.64 0.75 0.88 0.99

He I

HD 23478

12

Magnetosphere diagnostics

Hα

Brɣ

Br13

Paβ

0.1 0.21 0.32 0.44 0.55 0.64 0.75 0.88 0.99

He I

HD 23478

Velocity (km/s)

13

~±500 km/s

Summary

• Magnetic fields play an important role in shaping the circumstellar environment of hot, massive stars.

• Observational diagnostics give clues to the presence of magnetism across the entire electromagnetic spectrum

• Longer wavelength diagnostics are being developed

• IR is a viable tool to detect magnetic candidates in the Galactic center and star forming regions.

• SPIRou is coming soon:

• Ideal to simultaneously obtain magnetosphere and magnetic field info

• Requires in-depth knowledge of the features and behavior of magnetic diagnostics in the IR

• Determine physical characteristics of the magnetic field and magnetosphere of identified candidate stars.

• Study very young OB stars

14