x-ray binary light-curve analysis in optical and x-ray or “the ‘crazy’ lmxb (low mass x-ray...

X-Ray Binary Light-Curve Analysisin optical and x-ray

or “the ‘crazy’ LMXB (low mass x-ray binary) EXO 0748-676“

Trainee: Alexander Kolodzig

Origin: HU Berlin, UCM Madrid (Erasmus)

Tutor: Maria Diaz Trigo

ESA-Stay: 03/2008 - 06/2008

Background Picture Credits - Binary System: with ESA, NASA and Felix Mirabel - XMM-Newton: ESA (Image by C. Carreau)

08.09.2008, ESAC X-Ray Binary Light-Curve Analysis - A.Kolodzig 2

Overview

1. The Observed Object

2. Light-Curve – Analysis2.1. My Main Project-Tasks

2.2. Light Curve Creation

2.3. Modeling & Analysis

2.4. Further Analysis


Video Credits: D. Klochkov 2008

1. The Observed Object 1.1. Components of a LMXB (1/2)



1.2. Name and Type

• Name: EXO 0748-676

• (opitcal: UY Vol star)

• Type: low mass x-ray binary (LMXB)


1.3. Position in the Milky Way

• equatorial coordinates:

Figure: Sky distribution of bursters showing those observed by RXTE (Rossi X-ray Timing Explorer)

Credit: Galloway et al. 2006

°

h m s

07 48 33.3

-67 45 00


1.4. System Parameters

• Orbital Period: 3.82 hours(Parmar et al. 1985)

• Estimate Distance:5.9 - 7.7 kpc(Wolff et al. 2005)

• Inclination: 75° - 83°(Parmar et al. 1986)

• Optical Magnitude:16.9 mag(Pedersen et al. 1985)

• Binary Separation: 0.67 AU (1011 cm)

(Cottam et al. 2002)


1.5. Members of the System

• Neutron-Star– estimated Mass: 1.4 solar masses (SM)

• Companion Star– main sequence, sun like star– Mass: 0.45 SM

(assuming Roche lobe overflow, the spectral class & the neutron-star-mass)

(Masses: Parmar et al. 1986)


1.6. Discovery (1/2)

Early in 1985:

• esa x-ray satellite EXOSAT (1983 - 1986)

• open detector in a maneuver

• detects uncatalogued x-ray source

• Identifier: Mr. Arvind Parmar


Credit: Parmar et al. 1986

1.6. Discovery (2/2)

• First Light-Curve (by EXOSAT)BurstDip

Eclipse

x-ray (1 - 10keV)


1.4. Main Features

• „light curve shows a remarkable amount of structure“ (Parmar et al. 1985)

• sharp x-ray & broad optical eclipses

phase depending analysis

• strong, irregular & periodic dipping activity

• frequent x-ray burster with doublets & triplets

• system remains active since discovery

(23 years)


• creation and validation of the optical light curves (LC‘s)

• burst-deleting & folding of x-ray & optical LC‘s

• comparison of the x-ray & optical LC‘s

• modeling of bursts & eclipses in x-ray LC‘s

• modeling the optical LC’s

2. Light-Curve – Analysis 2.1 My Main Project-Tasks


• 3 independent X-RAY cameras– EPIC PN (Array of 12 CCDs)– Wavelength - Range: 0.5 - 10 keV

• 1 independent Optical/UV monitor (OM)

2.2. Light-Curves Creation 2.2.1. XMM-Newton Satellite


2.2.2. Optical Light-Curves (1/2)

• Observation-Date– in ‘Image+Fast Mode’

• high time resolution

– White Filter• high intensity


2.2.2. Optical Light-Curves (2/2)

• Light Curve Extraction– SAS (Science Analysis Software) task ’omfchain‘

• automatic source & background selection• time sampling: 1 second

– good signal-to-noise ratio

– inspection of the correct automatic selection– SAS task ‘barycen’

• time correction to the ‘solar system barycentre’


In all cases the EPIC pn was operated in Small Window Mode with the Medium Filter and the OM in Image+Fast Mode with the White Filter.

2.2.3. Observation-Log

• Observations 1 - 4 within 7 days!


1. Continuum

2.3. Modeling & Analysis2. Eclipses

3. Bursts 4. Periodicities(Dips, Modulations)

optical = blue

x-ray = red


2.3.1.a) x-ray Continuum (1/2)

Binning: 60 seconds

Flux (Counts/Second)

Time/Phase

for all Light-Curves


2.3.1.a) x-ray Continuum (2/2)

Triple Burst

Triple Burst

Double Burst

just 23,4 hour time gap between Observations

Binning: 60 seconds

BurstDipEclipse


2.3.1.b) optical Continuum (1/2)

Binning: 60 seconds


2.3.1.b) optical Continuum (2/2)

Triple BurstTriple Burst

Double Burst

Binning: 60 seconds

Burst

Eclipse



2.3.1.c) optical & x-ray Continuum

Binning: 60 seconds

Triple BurstTriple Burst

Double Burst

BurstDipEclipse


optical Flux

x-ray Flux

[10,45][0,220]


2.3.2.a) x-ray Eclipses (1/2)OID: 160760301

Binning: 1 second


2.3.2.a) x-ray Eclipses (2/2)

Ingress Egress

Binning: 1 second


2.3.2.b) Eclipses Results (1/2)

• Flux (Hard-Band): 0.24 0.20 Count/s– Ratio of Persistent Flux: 5,5%

• Eclipses not total evidence of a ‘Corona’

• Mean-Duration: 496 10 s (8.30.2 min)

– Parmer et al. 1991: 492 4.9 s• from End Ingress to Start Egress

• X-ray: Hard-Band (5-10 keV)– less Dip affected


2.3.2.b) Eclipses Results (2/2)

• Period (x-ray): 13766.74 0.06 s(42 Eclipse in 54 days) (3,824094 0,000017 hours)

– Parmar et al 1991: 13766,780 0,002 s(33 Eclipses in 4.1 years; linear Ephemeris)

Time

Cycle1

23

4

56

7

OID‘s


2.3.2.c) optical Eclipses

Binningred & blue: 60 secondsyellow (x-ray): 1 second

optical Gap

optical Flux

[7,20]


2.3.3. optical LC Modeling

• simple Model:C - Constant

A - Amplitude

xo - Phase-Shift

p - Period

• optical Periods:

sin 2 ox xpf x C A


2.3.4.a) Burst Modeling (1/2)

OID: 160760201X-Ray: with pile-up correction

Binning: 1 second

x-ray Flux

[0,420]

optical Flux

[0,110]


X-Ray: with pile-up correction

Binning: 1 second

2.3.4.a) Burst Modeling (2/2)

x-ray Flux

[0,420]

optical Flux

[0,110]


2.3.4.b) Burst Delay


2.3.4.c) optical Risetime


2.3.5.a) Dips

• Definition:“Dips are due to the central x-ray source being obscured by some structure above the disk.”(e.g. Frank et al. 1987)

• Example-Video:



2.3.5.b) Folded Light Curve

• 500 points/Phase

• same Period for all: 13767.0 seconds


2.3.5. Folded Light Curve


2.4. Further Analysis

• find super-period (around 50 or 27 hours)– preccessing, tilted accretion disc ?

• bursts-decay-modeling– phase-decay correlation ?

• better model for the optical LC’s

• deeper analysis of periodicities in the system

• and many many more (still after 23 years!)

Thanks for your Attention!

Questions?

Background Picture Credits - Binary System: with ESA, NASA and Felix Mirabel - XMM-Newton: ESA (Image by C. Carreau)

x-ray binary light-curve analysis in optical and x-ray or “the ‘crazy’ lmxb (low mass x-ray...

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