1. Rotationally modulated X-ray emission from the accretion shock in CTTS
V2129 Oph Project
C. Argiroffi, E. Flaccomio, J. Bouvier, J.-F. Donati,
K. V. Getman, S. G. Gregory, G. A. J. Hussain,
M. M. Jardine, M. B. Skelly and F. M. Walter
V4046 Sgr Project
C. Argiroffi, A. Maggio, T. Montmerle,
D. P. Huenemoerder, E. Alecian, M. Audard, J. Bouvier,
F. Damiani, J.-F. Donati, S. G. Gregory, M. Güdel,
G. A. J. Hussain, J. H. Kastner and G. G. Sacco
Costanza Argiroffi
The X-ray Universe - Berlin, 27 June 2011

2. ACCRETION IN YOUNG LOW MASS STARS MAGNETOSPHERIC ACCRETION MODEL
(Konigl 1991)
X-RAYS
X-rays from accretion in CTTS:
predicted by Ulrich (1976)
observational evidences by Kastner et al. (2002)
Costanza Argiroffi
The X-ray Universe - Berlin, 27 June 2011

3. WHY STUDY X-RAYS FROM ACCRETION
to constrain the total amount of X-rays emitted from CTTS
(to constrain the evolution of circumstellar disks)
to set the energy balance of the accretion-shock region
(to infer the mass accretin rate)
to probe the properties (i.e. density, velocity) of the accretion stream
(to understand how accretion occurs)
to probe the chemical composition of the inner disk
(to check the chemical evolution of circumstellar disks)
Costanza Argiroffi
INAF - OAPA, 27 April 2011

4. X-RAYS FROM ACCRETION: OPEN ISSUES
Observed X-rays significantly lower than predicted
Observability of the X-rays from accretion
Density vs temperature pattern: observations vs models
Costanza Argiroffi
INAF - OAPA, 27 April 2011

5. AIMS: SEARCH FOR ROTATIONAL MODULATION IN X-RAYS
Expected periodic variations in:
plasma densities
plasma average temperatures
EM of plasma at temperatures of 1-5 MK
Observing programs:
Long X-ray monitoring of a CTTS
with simultaneous optical observations
Projects:
V2129 Ophiuchi
V4046 Sagittari
Costanza Argiroffi
The X-ray Universe - Berlin, 27 June 2011

6. TARGETS: V2129 OPHIUCHI & V4046 SGR
Star
V2129 Oph
V4046 Sgr
single
binary
Mass
1.35 Msun
Msun ST K5
K5 + K5
Prot
6.53 days
2.42 days
age
3 Myr
10-15 Myr i
60 deg
35 deg B
4 kG
200 G
SFR
Rho Ophiuchi
Beta Pic
dist.
120 pc
72 pc
200 ks with Chandra/HETGS
360 ks with XMM
Costanza Argiroffi
The X-ray Universe - Berlin, 27 June 2011

7. X-RAY MONITORING OF V2129 OPH
seg. 1
seg. 2
(Donati et al. 2011, Argiroffi et al. 2011)
We have analyzed X-ray spectra integrated over: ~ 100 ks = 1 segment = 0.18 Prot
Costanza Argiroffi
The X-ray Universe - Berlin, 27 June 2011

8. VARIATIONS IN THE COOL EMD COMPONENT
EMD1 > EMD2 at 3-4 MK
Cool lines (long wavelengths) are stronger in seg.1 than in seg. 2
Costanza Argiroffi
The X-ray Universe - Berlin, 27 June 2011

9. VARIATIONS IN PLASMA DENSITY
Densities are higher in seg.1 than in seg. 2
Costanza Argiroffi
The X-ray Universe - Berlin, 27 June 2011

10. INTERPRETATION OF THE OBSERVED VARIABILITY
Results summary:
EM at ~4 MK is higher in seg.1 than seg.2
Ne at 4 MK is higher in seg. 1 than in seg. 2
(Argiroffi et al. 2011)
Costanza Argiroffi
The X-ray Universe - Berlin, 27 June 2011

11. The X-ray Universe - Berlin, 27 June 2011
V4046 SAGITTARI
(Stempels & Gahm 2004)
Costanza Argiroffi
The X-ray Universe - Berlin, 27 June 2011

12. X-RAY MONITORING OF V4046 SGR
Each segment is 120 ks
The X-ray observation covered 2.2 system rotations
We have analyzed X-ray spectra integrated over: ~25 ks = 0.12 Prot
Costanza Argiroffi
The X-ray Universe - Berlin, 27 June 2011

13. TIME RESOLVED X-RAY SPECTROSCOPY
Lines detected at 1 sigma in all the time intervals
Costanza Argiroffi
The X-ray Universe - Berlin, 27 June 2011

14. VARIABILITY: COOL LINES
(Argiroffi et al. 2011, ApJ submitted)
Best fit period = / days
(rot. period = 2.42 days)
Costanza Argiroffi
The X-ray Universe - Berlin, 27 June 2011

15. VARIABILITY: HOT vs COOL LINES
Hot lines:
Costanza Argiroffi
The X-ray Universe - Berlin, 27 June 2011

16. V4046 SGR X-RAY MONITORING: RESULTS
High density
Cool plasma is compatible with being material heated in the accretion shock
Rot. modulation
Cool plasma is not symmetrically distributed with respect to the stellar poles
Obs. period = half the system period
Naturally explained if high-density cool plasma is located on both the stellar components
X-ray vs optical results
X-rays are likely produced only by a fraction of the accretion shock region
Costanza Argiroffi
The X-ray Universe - Berlin, 27 June 2011

17. The X-ray Universe - Berlin, 27 June 2011
CONCLUSIONS
CTTS display variability in their soft X-rays
This variability can be explained in terms of X-rays emitted in the accretion shock and seen with different viewing angles during stellar rotation.
Soft X-rays, like all the other accretion indicators, display rotational modulation
Costanza Argiroffi
The X-ray Universe - Berlin, 27 June 2011