The Chandra LETG and XMM-Newton Spectra of HR 1099

5 Pages·0.31 MB·English

by  M. Audard

1
THE CHANDRA LETG AND XMM-NEWTON SPECTRA OF HR 1099
M.Audard1, M.Gu¨del1, and R.L.J.van der Meer2
1
Paul ScherrerInstitut,Wu¨renlingen and Villigen, 5232 Villigen PSI, Switzerland
2
SpaceResearch Organization Netherlands, Sorbonnelaan 2, 3584 CA Utrecht,The Netherlands
2
Abstract effect with decreasing activity,suggesting that the transi-
0
0 The X-ray luminous RS CVn binary system HR 1099 tion is real.
2
hasbeenobservedonseveraloccasionsintheearlyphases
n ofChandra andXMM-Newton.Averyhot(upto40MK) 2. Analysis
a dominant coronal plasma has been identified from the
J The Chandra X-ray Observatory observed HR1099 be-
high-resolution spectroscopic data; cooler plasma is seen
1 tween January 10–12, 2001 for 95 ksec (obsID1879) with
down to about 3 MK. We recently obtained 100 ksec in
3 the High-Resolution Camera (HRC-S) and the Low En-
Chandra’s Guest Observer Program to study the corona ergyTransmissionGrating(LETG).ItsLETGSspectrum
1 of HR 1099 with the High-Resolution Camera (HRC-S)
displaysbrightemissionlinesfromH-likeandHe-liketran-
v andtheLowEnergyTransmissionGrating(LETG)across
sitions of various elements (C, N, O, Ne, Mg, Si, S, Ar,
3 the complete temperature range above 1 MK. The data
3 Ca), and a rich forest of lines from Fe L-shell and 2s-2p
provide an unprecedented view of spectral lines and con-
5 lines. A few bright L-shell lines from Si and Ne can be
tinuaathighresolutionbetween 1and175˚A.Wepresent
1 identified as well. Figure 1 shows the LETGS spectrum
0 our investigations on the Chandra LETGS observation of from 1.5 to 175˚A together with identification labels from
2 HR 1099 into the context of the latest results obtained
major lines. The X-ray light curve (sum of both grating
0 with XMM-Newton.
/ orders)isalsogiveninFig.2;themeasuredfluxdecreases
h
with time, which could suggest that the observation has
p Keywords:Missions:Chandra,XMM-Newton–stars:HR
been performed during the decay ofa flare.We have used
-
1099 = V711 Tau – stars: coronae
o the updated MEKAL code available in the SPEX fitting
r
t program (Kaastra, Mewe, & Nieuwenhuijzen 1996) to fit
s
the average LETGS spectrum (after co-adding the pos-
a
: 1. Introduction itive and negative orders). We have performed a multi-
v
temperature fit to obtain coronal abundances and then
i
X HR 1099 (=V711 Tau; d=28.97 pc, K1 IV+G5 V-IV) usedaChebychevpolynomialapproachtoderivetheemis-
r is one of the brightest binary systems of the RS CVn sion measure (EM) distribution. The latter is dominated
a
class. The active K subgiant mainly contributes to the byhotplasma(≈20−40MK;Fig.3).Coronalabundances
chromospheric and coronal emissions (e.g., Ayres et al. (normalizedtoO)relativetothesolarphotosphericabun-
2001).Whileinthesolarcorona,aFirstIonizationPoten- dances (Anders & Grevesse 1989, except for Fe, Grevesse
tial (FIP) effect is observed (low-FIP elements enhanced & Sauval 1999) as a function of the First Ionization Po-
by factors of 4-6 relative to high-FIP elements), an in- tential are shown in Figure 4. An enhanced Ne abun-
verse FIP effect in the corona of HR 1099 has been found dance is found, similarly to results shown by Brinkman
(Brinkmanet al.2001).Other active stars also show such et al. (2001), Audard et al. (2001b), and Drake et al.
an IFIP effect (Gu¨del et al. 2001a; Gu¨del et al. 2001b; (2001). Note that the abundances differ from those ob-
Drake et al. 2001; Huenemoerder et al. 2001), while it is tained from the XMM-Newton RGS data (see Audard &
not present in the intermediately active Capella (Audard Gu¨del 2002 in these proceedings),although the same sys-
et al. 2001a). It is unclear whether there is an enrich- tematic trend can be found. Most probably, the discrep-
ment or a depletion of the coronal material compared to ancyoriginatesfromtheuseofadifferentplasmaemission
the photospheric materialin RS CVn systems,because of code in the analysis of the RGS data (APEC code). An
the high levels of activity and the short rotation periods. upper limit of ne ≤ 1012 cm−3 has been derived from
Estimates for HR 1099 range from [Fe/H]= −0.6 to 0. density-sensitive line ratios of Fe xxii (Fig. 5), while the
Hence the IFIP effect may only reflect the photospheric O vii line ratio (sensitive to cool plasma ≈ 2 MK) gives
composition.However,inananalysisofsolaranalogswith ne =2−5×1010 cm−3.
knownphotosphericabundances(closeto solar),Gu¨delet TheXMM-Newton RGSspectrumofHR1099isshown
al. (2002) (see also Audard & Gu¨del 2002 in these pro- with other RS CVn spectra (UX Ari, λ And, Capella;
ceedings)findanevolutionfromanIFIPto a normalFIP Fig.6).TheChandra andXMM-Newton spectraofHR1099
Proc. Symposium ‘New Visions of the X-ray Universe in the XMM-Newton and Chandra Era’ 26–30 November2001,
ESTEC, The Netherlands
2
00000.....000001122305050 S XVI Si XIV Mg XIINe XFe XXIV Ne IX Fe XVIIFe XVIII/O VIIIFe XVII O VO VIIIII N VII 0000....000000002345 Fe XVIII Ni XXI Fe XXINe VIII Fe XIXFe XXI Fe XVIII Fe XIX/XXI Fe XXII Fe XXII Fe XX
0.001
0.005
0.000
0.000
0 5 10 15 20 25 30 90 95 100 105 110 115 120
1−2−1 cm Å) 000...000001680 C VI S XII/Ne X (3) O VIII (2) C V Si XII Fe XVI O VIII (3) 1−2−1 cm Å) 000...000000345 Fe XX Fe XXI Fe XXIFIIe / XXXXII
−h s 0.004 −h s 0.002
p p
x ( 0.002 x ( 0.001
Flu 0.000 Flu 0.000
30 35 40 45 50 55 60 120 125 130 135 140 145 150
0.005 0.005
00..000034 Fe XVIFe XVI Fe XVI Ne X (6) O VIII (4) Ni XX Ne VIII 00..000034 O VIII (8) Ni XIII Ni XXIV Fe IX Fe X
0.002 0.002
0.001 0.001
0.000 0.000
60 65 70 75 80 85 90 150 155 160 165 170 175 180
Wavelength (Å) Wavelength (Å)
Figure1. LETGS spectrum of HR 1099 together with major identified emission lines (at the exception of the Fe ix and
Fe x lines, in violet, that have been marked to emphasize their absence in the spectrum as an evidence of the absence
of a significant cool component, T ≈1−2 MK, in the corona of HR 1099). Data are in red, and a best-fit model (cf.
Fig. 3) is in green.
show a dominance of a hot plasma indicating a high level from IFIP to FIP found in solar analogs (Gu¨del et al.
of activity in this binary system. As found by Brinkman 2002; see also Audard & Gu¨del 2002).
etal.(2001),low-FIPelementstendtobeunderabundant
Acknowledgements
relativetohigh-FIPelements.Itisprobablyrelatedtothe
ThePSIgroup acknowledges supportfrom theSwiss National
correlation between the activity level of a coronal source
Science Foundation (grant 2100-049343).
and its FIP bias (Gu¨del et al. 2002; see also Audard &
Gu¨del 2002).
References
3. Conclusions Anders,E.,&Grevesse,N.1989,Geochim.Cosmoschim.Acta,
53, 197
HR1099isahotRSCVnbinarythatshowsahighNe/Fe Audard, M., Behar, E., Gu¨del, M., et al. 2001a, A&A, 365,
ratio.Relativetosolarphotosphericabundances,theabun- L329
dance pattern of HR 1099 (normalized to O) is similar to Audard,M., Gu¨del, M., & Mewe, R.2001b, A&A,365, L318
other active RS CVn binaries, although less active stars Audard,M., & Gu¨del, M. 2002, these proceedings
(λAnd,Capella)shownoinverseFIPeffect.Thispattern Ayres, T. R., Brown, A., Osten, R. A., et al. 2001, ApJ, 549,
in active binaries fits well into the long-term evolution 554
3
5
10.0
Ca NiSi SC ONAr Ne
4 HR 1099, HRC−S/LETG (m=±1) Fe
g
M
c
eri
h
3 p
Count rate [c/s]2 olar photos 1.0
s
o
e t
v
1 ati
el
O, r
A/ HR 1099
0
51920.0 51920.2 51920.4 51920.6 51920.8 51921.0
MJD
Figure2. X-ray light curve of the LETGS observation of
HR 1099. The sum of the positive and negative grating 0.1
orders is shown. The light curve suggests that the obser- 10
First Ionization Potential [eV]
vation was possibly performed during the decay phase of a
flare.
1054 Figure4. Coronal abundances of HR 1099 (normalized to
oxygen)relativetosolarphotospheric abundances(Anders
& Grevesse 1989, except Fe, Grevesse & Sauval 1999) as
a function of FIP. Notethat the abundances have been de-
−3m) rived using a recent update of the MEKAL code in SPEX.
measure per bin (c 1053 Sdeffaimneccitela.rislyfotounBdr,isnukgmgaesntientgatlh.e(2p0re0s1e)n,cae hoifgahnNine/vFereseabFuInP-
mission
E Gu¨del, M., Audard,M., Sres, A., et al. 2002, ApJ, submitted
1052 Huenemoerder, D. P., Canizares, C. R., Schulz, N. S. 2001,
ApJ, 559, 1135
Kaastra, J. S., Mewe, R., & Nieuwenhuijzen, H. 1996, in UV
and X-ray Spectroscopy of Astrophysical and Laboratory,
1 10 100
Temperature (MK) ed. K. Yamashita & T. Watanabe (Tokyo: Univ. Acad.
Press), 411
Figure3. Emission measure distribution of HR 1099 ob-
served by Chandra LETGS. Abundances from a multi-
temperature fit have been used. Note that a modified
MEKALplasmaemissioncodeavailableinSPEXhasbeen
used.
Brickhouse,N.S.,Raymond,J.C.,&Smith,B.W.1995,ApJS,
97, 551
Brinkman,A.C.,Behar,E.,Gu¨del,M.,etal.2001,A&A,365,
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Drake, J. J., Brickhouse, N. S., Kashyap, V. L., et al. 2001,
ApJ, 548, L81
Grevesse, N.,& Sauval,A. J. 1999, A&A,347, 348
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Gu¨del, M., Audard, M., Magee, H., et al. 2001b, A&A, 365,
L344
4
0.30
HR 1099, LETGS
Fe XXII λλ114.41 / λλ117.17
0.25
Ratio
Intensity 0.20
0.15 1σ
0.10
8 9 10 11 12 13
Log ne (cm−3)
Figure5. Density upper limit from Fe xxii lines. The dot-
ted blue line represents the measured line ratio, while the
dashed blue lines are 1 σ confidence ranges. The contin-
uous red curve is a theoretical curve based on models de-
rived by Brickhouse et al. (1995). The black dash-dotted
line gives the upper limit to the measured density. Note
that the O vii line ratio (sensitive to plasma ≈ 2 MK)
gives ne =2−5×1010 cm−3.
5
αSi XIII He αMg XII LyαMg XI HeβNe X LyFe XXIVαNe X LyαNe IX He Fe XVIIFe XVIIIFe XVII αO VIII Ly αO VII He αN VII Ly αC VI Ly
25
20
15 HR 1099
10
5
0
1) 15
−
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2
− 10
m UX Ari
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1
− 5
s

h
p
0
3 12
−
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10
1
(
8
x λ
And
u
l 6
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n 4
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40
30 Capella
20
10
0
10 15 20 25 30 35
Wavelength (Å)
Figure6. XMM-Newton RGS spectra of HR 1099 with compared other RS CVn binaries (see Audard & Gu¨del 2002 in
these proceedings). Note the difference in flux ratios between Ne ix (logTm ≈ 6.6; arrow) and Fe xvii (logTm ≈ 6.73;
arrow), especially in UX Ari and Capella, suggesting that their coronae differ in their elemental composition.