X-Rays from Low and Intermediate Mass Stars

X-rays from low and intermediate mass stars

Jan Robrade

Hamburger Sternwarte

X-ray Universe, Dublin, 16-19 June 2014 The solar corona

Sun in X-rays: SDO, Yohkoh, TRACE

Solar corona is highly structured and dynamic

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 2 / 23 Stellar X-ray emission

This talk: Low and intermediate mass stars

X-ray generation mechanisms Time evolution of X-ray emission

’The X-ray HRD’ (G¨udel 2004)

X-ray stars are (virtually) everywhere!

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 3 / 23 Cool stars in X-rays

The solar neighborhood: volume limited

(Schmitt 1997)

X-ray surface ﬂux varies by orders of magnitude at given B-V Sun weakly active, coronal holes describe lower limit X-ray activity declines towards hotter stars

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 4 / 23 Cool stars in X-rays

Activity-dynamo relation

(F - mid M) (Wright+ 2011)

X-rays from magnetic activity, log LX/Lbol ≈ −3 ... −7

LX ∝ dynamo power; Ro = P/τc

powerlaw (slope?) - saturation (level, breakpoint ?) - supersaturation (?)

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 4 / 23 Coronal dynamo regimes

Activity regimes of stars (blue: Ro = 0.13, red: Rc /R∗ = 3, green: GX = 0.01) (Wright+ 2011) (also: Jeﬀries+ 2011) dynamo regimes depend on mass and rotation supersaturation: excess polar updraft vs. centrifugal stripping

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 5 / 23 X-ray activity at very low masses

Very red dwarfs are faint...... and fully convective!

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 6 / 23 Ultracool Dwarfs - magnetic activity at low masses ) 1 − 100 LHS 3003 (M7) 80 60 40 20 0

Rate (cts ks (cts Rate 0 10 20 30 40 50 )

1 2.0 − SCR J1845-6357 (M8.5) 1.5 1.0 0.5 0.0 Rate (cts s (cts Rate 0 5 10 15 mod. active stars )

1 35 log LX/Lbol ≈−4, − 30 LHS 2065 (M9) 25 20 TXqq = 1 − 5 MK 15 10 5 0

Rate (cts ks(cts Rate 0 10 20 30 40 Time (ks)

X-ray light curves of very low mass stars (XMM-Newton, Chandra)

quasi-quiescent X-ray emission, log LX/Lbol ≈−3.0 ···− 5.0 strong ﬂares with hot plasma (& 10 MK) frequent

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 7 / 23 Ultracool Dwarfs - X-ray/radio connection

18 < M6.5 M6.5–M9.5 > M9.5 17 Benz & Güdel (1994) Upper limit New result Flare 16

14 g/s/Hz] [er R ,

L 13 10 log

11 Radio vs. X-ray luminosity

(Williams+ 2014) 10

24 25 26 27 28 29 30 31 32

log10 LX [erg/s]

X-ray bright and radio bright group (also Stelzer+ 2012) UCDs violate G¨udel-Benz relation

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 8 / 23 Ultracool Dwarfs - X-ray/radio connection

18 < M6.5 M6.5–M9.5 > M9.5 17 Benz & Güdel (1994) Upper limit New result Flare 16

14 g/s/Hz] [er R ,

(image by G. Hallinan) L 13 10 log

11 Radio vs. X-ray luminosity

(Williams+ 2014) 10

24 25 26 27 28 29 30 31 32

log10 LX [erg/s] changing/bimodal dynamo mechanism, increasingly neutral atmospheres (e.g. Mohanty & Basri 2003, Reiners & Basri 2010) radio bright objects, fast rotators: ECME, aurorae (Hallinan+ 2007/08)

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 8 / 23 X-ray activity at higher masses - A stars

A stars are optically bright... but what about X-rays?

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 9 / 23 X-ray activity at higher masses - A stars

BSC sample: opt. brightness limited

(Schr¨oder & Schmitt 2007)

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 9 / 23 X-ray activity at higher masses −1 keV −1 0.01 0.1 normalized counts s −3 10

0.5 1 Energy (keV)

XMM spectra of Altair and Alderamin

A7 IV-V, M = 1.8/2.0 M⊙, age: 1.2/0.8 Gyr ultra-fast rotators, Vsini ≈ 220/280 km/s, 60/80 % break-up virtual identical X-ray properties

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 10 / 23 X-ray activity at higher masses

X-ray light curve and high-res spectrum of Altair (A7) (Robrade & Schmitt, 2009)

27 LX = 1.4 × 10 erg/s, log LX/Lbol = −7.4 minor activity, rotational modulation, long-term stable corona coronal properties similar to inactive Sun dominated by cool 1–4 MK plasma solar-like abundance pattern (FIP eﬀect, Ne/O ratio) O vii f/i-ratio high (UV sensitive)

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 10 / 23 X-ray activity at higher masses

1.0

0.5

0.0

-0.5 North (milliarcseconds)

-1.0

1.0 0.5 0.0 -0.5 -1.0 East (milliarcseconds)

Surface images of Altair & Alderamin, CHARA (Monnier+ 2007, Zhao+09)

oblate, gravity darkening ⇒ Teﬀ ≈ 6800 K - 8500 K

X-ray surface features at Teﬀ . 7400 K ’equatorial bulge corona’

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 10 / 23 The fading of X-ray activity

105

104

103

102

observation 101 ratio of count ratesHRC-I/MOS count of ratio

0 10 0.4 0.6 0.8 1.0 1.2 Temperature in MK

β Pictoris (ESO, G¨unther+ 2012)

β Pictoris - A6, young, debris disk (Hempel et al. 2005, G¨unther et al. 2012)

X-rays: very soft (TX ≈ 1 MK), very faint (log LX ≈ 26.5)

=⇒ No signiﬁcant magnetic activity around A5 (or earlier)

...tight upper limits on Fomalhaut (A3) and Vega (A0) (log LX < 25.5)

X-ray detections likely companions (e.g. VAST survey; De Rosa et al., 2011)

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 11 / 23 Ap/Bp stars – X-rays and the MCWS model

MCWS model (Babel & Montmerle, 1997)

MHD/RFHD advancements: (ud-Doula, Owocki, Townsend)

rigid disks, dynamic phenomena

Ap/Bp stars: magnetic intermediate mass stars, chemically peculiar, slow rotators ﬁelds: large-scale, stable, uncorrelated, rare (< 10 %), fossil

IQ Aurigae: A0p, (Teﬀ ≈ 14500 K, M = 4.0 M⊙, age ≈ 60 Myr) ROSAT detection: X-ray bright, soft spectrum X-rays via magnetically conﬁned wind-shocks (MCWS)

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 12 / 23 Ap/Bp stars – X-rays and the MCWS model

MCWS model (Babel & Montmerle, 1997)

MHD/RFHD advancements: (ud-Doula, Owocki, Townsend)

rigid disks, dynamic phenomena

XMM-Newton lightcurve of IQ Aur (Robrade & Schmitt, 2011)

hot plasma in quasi-quiescence & large ﬂare strong soft X-ray component magnetic activity + wind shocks

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 12 / 23 Ap/Bp stars – IQ Aurigae −1 keV −1 0.01 0.1 1 normalized counts s −3 10

0.51 2 5 Energy (keV)

Quasi-quiescent lightcurve & X-ray spectra - XMM (Robrade & Schmitt, 2011)

−1 log LXqq = 29.6 erg s , log LX/Lbol ≈−6.5

X-rays from well above the stellar surface (O vii f /i ≈ 1, d & 7 R∗) 31 −1 ﬂare: LXpeak = 3 × 10 erg s , very hot plasma: TX . 100 MK

metallicity increase, moderately sized structure, L . 0.2 R∗

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 13 / 23 Ap/Bp stars in X-rays

HD 144334

1e+30 HD 34452 Lx/Lbol = -7 HD 12767

HD 146001 1e+29 HD 125823

HD 175362 HD 137509HD 142301F 1e+28 HD 133880

HD 184905 HD 22470 HD 54118 HD 147010 HD 122532 HD 143473 HD 28843 HD 27309 LX vs. Lbol 1e+27 HD 40312 X-ray luminosity (erg/s) A0 – B7, magnetic CP stars

HD 112413 1e+26 (updated from Robrade & Schmitt (2011)

1.8 2 2.2 2.4 2.6 2.8 3 3.2 Stellar luminosity (log LSun)

X-rays predominantly in more luminous Ap/Bp stars (L∗ & 200L⊙)

suﬃcient mass loss & wind speed, strong magnetic conﬁnement (η∗ ≫ 1) weak trend with opt. brightness ...but large scatter X-ray/Radio relation violated in all cases, radio-overluminous

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 14 / 23 Ap/Bp stars in X-rays

30 30

29 29 (erg/s) (erg/s)

X 28 X 28

27 27 log L log L

26 26 2.5 3.0 3.5 4.0 4.5 5.0 5.5 4.0 4.1 4.2 4.3 M (MSun) log Teff (K)

30 30

29 29 (erg/s) (erg/s)

X 28 X 28

27 27 log L log L

26 26 1.0 2.0 3.0 4.0 5.0 6.5 7.0 7.5 8.0 8.5 Beff (kG) log t (yr) LX vs. stellar parameter

no correlation of LX with age or Beﬀ unexplained scatter: magnetic ﬁeld geometry, time variability, companions...

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 14 / 23 The temporal evolution of solar-like activity

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 15 / 23 The evolution of stellar rotation

Envelope

Core

Rotation vs. age for solar-like stars in open clusters (Gallet & Bouvier 2013)

large spread of initial rotation periods

rotation is function of age and mass (Teﬀ , color)

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 16 / 23 X-ray activity as age indicator

1−20 Å 1000 20−100 Å 100−360 Å 360−920 Å 920−1200 Å 100

10 Relative flux (Sun=1)

0.1 0.1 0.2 0.3 0.40.5 1 2 3 4 5 6 7 8 Age (Gyr)

X-ray/UV ﬂux vs. age - ’Sun in time’ (Ribas+ 2005)

activity age: rotation ⇒ dynamo processes/magnetic ﬁeld ⇒ activity steep decline, wavelength dependent

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 17 / 23 X-ray activity as age indicator

IC2391 IC2602

Pleiades

UMa

Hyades

Prox. Cen Sun 16 Cyg A HR7703

X-rays vs. age (Garces+ 2011)

well suited to identify young stars scatter in young stars - age ok for ensembles like groups/clusters poorly calibrated beyond 1 Gyr, activity cycles in older stars

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 17 / 23 Activity cycles in X-rays

Year 2008 2009 2010 2011 2012 2013 0.28 10 ι Hor

0.26 8 L x (x10

0.24 6 28 erg/s)

4 Mount Wilson S-index 0.22

2 0.20 4500 5000 5500 6000 HJD (+2450000)

ι Hor (F8), age: 600 Myr; Ca ii (black), X-rays (red) (Sanz-Forzada+ 2013)

cycles in more active stars often irregular multiple periods present

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 18 / 23 Activity cycles in X-rays

2006-10-29 30.0 2009-10-27 61 Cyg 46:00.0 46:00.0 1e27 61 Cyg A - XMM A 30.0 30.0

2.0 38:45:00.0 38:45:00.0 )

1 30.0 B

− 30.0 s 44:00.0 2 02.0 21:07:00.0 58.0 56.0 54.0 06:52.0 02.0 21:07:00.0 58.0 56.0 06:54.0

− 1.5

1.0 (ergcm X L

0.5 2002 2004 2006 2008 2010 2012 2014 Time (year)

61 Cyg A (K5), age: 4–6 Gyr (Robrade+ 2012)

cyclic X-ray activity in older solar-like stars, likely common diverse periods and amplitudes, coronal changes are solar-like var. more pronounced for hotter plasma/active regions

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 18 / 23 Activity cycles in X-rays

Alpha Cen A - XMM 1.01e27

) 0.8 1 − s 2

− 0.6

0.4 (ergcm X L 0.2 MOS1: α Centauri A/B: 2003/2005

2004 2006 2008 2010 2012 2014 Time (year)

1e27 Alpha Cen B - XMM

4 ) 1 − s

2 3 −

2 (ergcm X

L 1

MOS1: α Centauri A/B: 2014 2004 2006 2008 2010 2012 2014 Time (year)

α Cen A (G2) and α Cen B (K1), age: 5–7 Gyr (Robrade+ 2012)

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 18 / 23 SUMMARY so far

Low mass stars: Magnetic activity omnipresent in stars with surface convection - dynamo power related to rotation and internal structure - strong evolution with time, appearance of activity cycles - deviations from solar type dynamo at low and high mass end

Intermediate mass stars: X-ray emission generated by MCWS phenomena - suﬃciently fast and strong winds required - magnetic activity needed to explain X-ray phenomena in IQ Aur - several details open

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 19 / 23 X-rays from YSOs

The youth of low and

intermediate mass stars

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 20 / 23 Young low-mass stars: classical T Tauri stars

TW Hya (0.5 Ms Chandra, Brickhouse+ 2010) DG Tau (ACIS, G¨udel+ 2011)

magnetic activity omnipresent and strong X-rays from accretion shocks common (high density plasma + soft excess ) stellar X-ray jets

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 21 / 23 Young low-mass stars: classical T Tauri stars

BP Tau RGS, O vii-triplet (Schmitt+ 2005) soft excess O viii/O vii ratio (Robrade+ 2014)

BP Tau (Schmitt+ 2005), DN Tau (Robrade+ 2014), MP Mus (Argiroffi+ 2007), RU Lup (Robrade & Schmitt 2007), TW Hya (Kaster+ 2002, Stelzer & Schmitt 2004, Brickhouse+ 2010, 2012), V4046 Sgr (Günther+ 2005, Argiroffi+ 2012)... soft excess: Güdel &Telleschi 2007, Robrade & Schmitt 2007, Telleschi+ 2007... jets: Güdel+ 2007, 2011, Schneider & Schmitt 2008...+ sample studies like COUP, XEST...

See talks at: Stellar parallel session

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 21 / 23 HAeBe stars – young intermediate mass stars

(1.5–15 M⊙ Alecian+ 2013)

X-rays from jets, coronae (AB Aur, HD 163296...)

large spread in log LX/Lbol, companions? (Stelzer+ 2009) IMTTS at lower masses/younger age (RY Tau, SU Aur, T Tau...)

AB Aur (Telleschi+ 2007), HD 163296 (Swartz+ 2005, G¨unther & Schmitt 2009), SU Aur (Robrade & Schmitt 2006), RY Tau (Skinner+ 2011), T Tau (G¨udel+ 2007)... Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 22 / 23 Into the future...

eRASS ∼ 0.7 Mio. X-ray stars −14 −2 −1 lim. FX ≈ 1 × 10 erg cm s

2015 – ASTRO-H (JAXA+): calorimeter, resolution 7 eV, 0.3–12.0 keV 2016 – eROSITA/SRG (D/Ru): all-sky survey, 0.3–10.0 keV

Talks on Thursday morning: Predehl, Guainazzi...

Jan Robrade (Hamburger Sternwarte) X-rays from Stars 16.06.2014 23 / 23