the erosita all-sky survey - stars in x-rays...cas per tau sun lac ob1 cep ob2 cep ob6 a per per ob2...

The eROSITA all-sky survey - Stars in X-rays...

Jan Robrade

Hamburger Sternwarte

The X-ray Universe 2017Rome, 6 - 9 June

eROSITA (extended Roentgen Survey with an Imaging Telescope Array)

Jan Robrade (Hamburger Sternwarte) eROSITA & Stars 06.06.2017 2 / 10

eRASS:

eROSITA All-Sky Surveydata acquisition: 2019 – 2022

lim. FX ≈ 1× 10−14 erg cm−2 s−1

eROSITA on SRG

talk by P. Predehl (Thursday morning)

SRG Spacecraft

eROSITA/SRG – launch 2018, L2 halo orbit

all-sky survey (4 yr, sky-split D/Ru) + pointed phase (3.5 yr)

7 co-aligned X-ray telescopes, FOV 1.03◦ Ø

0.3 – 10.0 keV, HEW 15/28 ′′, eff. area@1keV 2400/1400 cm2

eRASS and stars


’The X-ray HRD’ (Gudel 2004)

eRASS detection limit:

LX ≈ 1.0× 1024 × d2(pc) [erg s−1]

’eRASS sensitivity with two Suns’(adapted from Wright et al. 2010)

eRASS (black line) vs.

ROSAT: survey+pointings (dots)

Chandra: CDF-N, ChaMP, COSMOS (crosses)

eRASS and stellar population models


3.0 2.5 2.0 1.5 1.0 0.5 0.0log S (cts/s)

1

0

1

2

3

4

log N

(1/d

eg^

2)

Stellar surface densities at var. galactic lat./lon.

Simulations are based on the Besancon Stellar X-ray population model.

Image by J. Robrade.

eROSITA X-ray stars (all, 0.5-2.0 keV)

ns00000

ns00090

ns00180

ns05000

ns05180

ns10000

ns10180

ns20000

ns20180

ns30000

ns30180

ns50000

ns50180

ns70000

ns70180

ns90000

Besancon model:(RASS, Guillout+ 1996)

∼ 0.7 million X-ray stars

> 50 per deg2 (disk),

∼ 6 per deg2 (poles)

(lim. logS = -1.9 [cts/s], 20 cts/1650s)

3 age x 6 star groups (0.15/1.0/10 Gyr, A to late M, ’standard’ coronal sources)

strong overall contribution from young stars (∼ 250000)

Detecting nearby stars with eROSITA


0 20 40 60 80 100Distance (pc)

26.0

26.5

27.0

27.5

28.0

log L

x (

erg

s−

1)

TW Hya --> 1kpcEK Dra, AB Dor --> 1kpc

AT Mic --> 500 pcπ1 UMa--> 300 pc

AD Leo --> 200 pc

HR 8799

β Pic TWA η ChaAB Dor Tuc/Hor

Pleiades (130 pc)

Gould Belt SFRs(≥ 140 pc)

F - mid M stars

late A/VLM+

Nearby young stars - eRASS X-ray horizon

Sensitivity at 100 pc (MS):

early F (5 L�) → log LX/Lbol = -6.3

mid M (0.005 L�) → log LX/Lbol = -3.3

young+nearby (100 pc, 200 Myr) → virtually all F to mid M stars

closer X-ray horizon for late A, VLM stars and older populations

very nearby - RECONS 10 pc sample :: > 300 stars (4-6-20-44-248, A-F-G-K-M)

SFRs & T Tauri stars


−400

−200

0

200

400−600 −400 −200 0 200 400 600 800

Ori

Vela

Oph

Aqu

Cep

Cas

Per

Tau

Sun Lac OB1

Cep OB2

Cep OB6

α Per

Per OB2Ori OB1a

Ori OB1b

Ori OB1c

Col 121

Vela OB2

Tr 10 LCC

UCLUS

X (

pc)

Y (pc)

10 km s−1

GC

Nearby SFRs and Gould Belt

CTTS - WTTS - ZAMS

strong X-ray emission in all YSOs

all-sky & harder energy range ideal

SFRs at 100 – 500 pc (Gould belt)

CTTS: accretors

WTTS: weak/no accretion or disks

post TTs/ZAMS

Massive SFRs in Milky Way,collective X-ray emission

More rare stars


Stelzer et al. (2009)

Williams et al. (2014)

Massive + Intermediate mass stars

O + early B stars, Lx/Lbol relations

WR, LBV, magn. massive stars

HAeBe stars : coronae, jets, MCWS,(companions)

ApBp stars : MCWS, magnetic disks,(companions)

Ultracool dwarfs (M7+)

X-ray bright UCD population in solarvicinity (. 30 pc)

VLM stars (fully convective)

young or massive/hot BDs

Beyond detections - spectral properties


10.5 2 5

0.0

10

.11

10

no

rma

lize

d c

ou

nts

s−

1 k

eV

−1

Energy (keV)

AT Mic (2ks eRASS)

AT Mic - simulated eRASS spectrum (27000 counts)

about 50000 (5000) stars with & 200 (1000) counts

coronal properties of X-ray brighter targets

multi-band HR classification for many other sources

Beyond detections - time-dependent properties


0 2•105

4•105

6•105

8•105

1•106

Time [sec.]

0

500

1000

1500

2000

Counts / K sec

0

1000

2000

3000

4000

counts [approx.]

9 10 11 12 13 14 15 16 17 18 19 20 21

COUP 1568 Cts: 89438 M: 2.55R: 3.99

2002 2004 2006 2008 2010 2012 2014 2016Time (year)

0.5

1.0

1.5

2.0

L X 1

027 [e

rg s−

1]

61 Cyg A - XMM

0 5 10 15 20 25 30 350.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Rate

(cts

s−

1)

LP 412-31 (M8)

0 5 10 15

Time (ks)

0.0

0.5

1.0

1.5

2.0

Rate

(cts

s−

1)

SCR J1845-6357 (M8.5)

X-ray light curves – left: nearby young stars; middle: A0p star, CTTS, K dwarf; right: M dwarfs, UCDs

light curves on multiple timescales + transient sources

4 yr survey: 8 sky-scans (0.5 yr) with 6 scans/day (40 s each)

X-ray variability, flare statistics, activity cycles...

Summary and synergies


The eROSITA all-sky survey - an unprecedented view of the X-ray sky

RASS =⇒ eRASS: about factor 20 higher sensitivity

plus variability, higher spatial resolution, X-ray spectral characteristics...

volume complete samples, full stellar populations, large object numbers

Synergies: most eROSITA stars are optically bright (V . 15 mag)

Gaia :: distances, 3-D space motions, identifications etc.

MWL data and aux. catalogs :: stellar properties, activity+age indicators,planet hosts etc.

Interested in collaborating? Give us a note...

the erosita all-sky survey - stars in x-rays...cas per tau sun lac ob1 cep ob2 cep ob6 a per per ob2...

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