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Photometry and spectroscopy of varaible stars, May 10, 2013

Photometry and spectroscopy of variable stars

with small telescopes

Vadim Burwitz (MPE)May 10, 2013

Small Telescope Workshop Istanbul

Overview

� Variable Stars

• What are they ?

• Measurements

• Classification

� Variable stars: X-ray / optical connection

� Accreting white dwarfs

� The PIRATE Robotic Telescope Project

� Spectrographs for small telescopes:

• DADOS

• BACHES

May 10, 2013 Photometry and Spectroscopy of Variable Stars with Small Telescopes Vadim Burwitz (MPE)


What are variable stars?

� They are stars that show changes in brightness as seen

from earth.

� The reason for brightness changes are manifold:

� Intrinsic:

• Pulsating � evolutionary stage (physical

properties)

• Eruptive� Flares , Mass ejections

• Cataclysmic / Explosive � Novae, Supernovae

� Extrinsic:

• Geometry � Eclipses in binary systems

• Rotational effects


Measurements

� Photometric lightcurves give �

� The periods present in the star: orbital, spin,

pulsation

� The shape symmetry, eclipses, dips

� Optical spectra yield �

� Spectral type / Luminosity class

� Absorption and emission lines

� Radial velocity shifts

� Changes in temperature

� Magnetic fields

The zoo of variable Stars


o The zoo is full of many

stars sorted into many

categories

o � based on physical

characteristics.

o Measurable periods are

in the range minutes to

years.

o Most of these variable

stars can be observed

with small telescopes. Image source wikipedia

Variable stars: X-ray / optical connection

Types of optical observations to complement

X-ray observations

�Follow-up observations (ROSAT, future eROSITA)

�� post discovery: photometry / spectroscopy

�Preparatory observations (XMM, Chandra)

�� trigger X-ray observations

� for objects with X-ray bright and faint states

�Contemporaneous multiwavelength

observations

(SWIFT, XMM, Chandra … etc )

�� during the X-ray observationsMay 10, 2013 Photometry and Spectroscopy of Variable Stars with Small Telescopes Vadim Burwitz (MPE)

Accreting white dwarfs

�Types of accreting white dwarfs

� Magnetic and non-magnetic accretion

� White dwarfs at high accretion rates

• Supersoft X-ray Sources

• Novae in M31


Types of accreting white dwarfs

� non-magnetic accretion = boundary layer accr.

• Magnetic and non-magnetic accretion

� magnetic accretion = funnel accretion

• Polars or AM Her stars

• Intermediate polars or DQ Her Stars


Boundary Layer Accretion

Wind

White Dwarf

Boundary Layer- X-rays

Accretion Disk

Wind



Types of accreting white dwarfs

� non-magnetic accretion = boundary layer accr.

• Magnetic and non-magnetic accretion

� magnetic accretion = funnel accretion

• Polars or AM Her stars

• Intermediate polars or DQ Her Stars


Magnetic cataclysmic variables (mCVs)

PolarsPorb = Pspin (synchronous)

No accretion disk

B ~ 10-200 MG

Intermediate PolarsPorb > Pspin

possible accretion disk

B upto 20 MG


Overall spectrum of mCVs

White

Dwarf

UV

Red

Dwarf

IR

Soft X-rays

Hard X-rays

Optical


Standard accretion scenario in mCVs

Blobs of matter that release Energy below the surface

SHOCKInfrared – Optical – UV

(cyklotronradiation)

Magneticfield-strength

B = 1 - 200 Million Gauss

White DwarfPhotosphereT = 20000 K

cool supersonicaccretion flow

Soft X-rays – UV(black-body radiation)T = 300000 Kelvin

Magnetic field line

Magnet ic f ield li ne

Hard XHard X--raysrays(Bremsstrahlung)(Bremsstrahlung)

T = 1 T = 1 ––100 Million Kelvin100 Million Kelvinstream of slowshock heated

Matter


The Polar

AM Herculis

a) b) c)

d) e) f)

companion of type dM4

Porb = 186 min = 3.1 hours

d = 85 ±±±± 5 pc

B = 14.5 MG

Twd = 24.000 K


Lightcurve: Polar

I

R

V

B

U


Lightcurve: Polar

RX J0453.4-4213 = RS Caelum

V ~ 19 mag.

Lightcurve: Intermediate PolarRX J0512.2-3241 = UU Col

V ~ 17.6

Accreting white dwarfs

�Types of accreting white dwarfs

� Magnetic and non-magnetic accretion

� White dwarfs at high accretion rates

• Supersoft X-ray Sources

• Novae in M31


Observational definition of

supersoft X-ray binaries

• Supersoft > 90% of intrinsic source photons

in 0.1– 2 keV band below 0.5 keV

• X-ray luminous soft X-ray source

fsoft x > fopt

• Binary evidence for binarity:

e.g. orbital period, variability


Discovery of SSXBs with ROSAT


Nature of the binary components

Primary: wd, ns, bh?

observational evidence:

• energy distribution

→ radius

• radial velocity curve

→ mass function

• jets → escape velocity

⇒ white dwarf

Secondary:

observational evidence:

• none

theoretically expected:

• spectral type A – F

(M2 > M1)

or

• spectral type K – M

(M2 < M1)


SSXBs as accreting binaries

CAL 83

RX J0513-69

CAL 87Sun van Teeseling, Kube

mB = 16.2 mag

Porb=0.76 days

I ~ edge on

mB = 16.2-16.9 mag

Porb= 1.04 days

i = 25 deg

mB = 19 mag

Porb=10.6 hours

I ~ edge on


RXJ0513-69: long term optical lightcurve

Southwell et al. 1996


MACHO Data

RXJ0513-69: long term optical lightcurve

Burwitz et al. 2008


RXJ0513-69: X-ray

and optical

variability

Reinsch et al. 2000May 10, 2013 Photometry and Spectroscopy of Variable Stars with Small Telescopes Vadim Burwitz (MPE)

RXJ0513-69: X-ray

and optical

variability


RXJ0513-69: X-ray

and optical

variability


Discovery of extragalactic novae:monitoring of M31

So far 6 CBET or Atelentries



Summary Part I

� Variable Stars

� Offer many possibilities for astrophysical studies

� using small telescopes

� Accreting white dwarfs

� CVs are easily accessible to photometry

� the short orbital periods (several hours to days)

� yield lots of information in a short time

� Low Resolution Spectroscopy:

� Brighter objects can be observed nicely

� Detecting and Monitoring Novae in M31 or sim.

� through regular observation of same fields

� patience is eventually rewarded.

Physics Innovations Robotic Astronomical

Telescope Explorer

Physics Innovations Robotic

Astronomical Telescope Explorer

PIRATE site

• Observatori Astronomic de Mallorca (OAM)

• host observatory of SXR208

Longitude E 2° 57' 06''Latitude N 39° 38' 38''Altitude 203 m

PIRATE milestones

• 2008 PIRATE prototype– funded initially by a UK teaching initiative (OU &

Leicester University) and OAM

– to explore feasibility of use in distance teaching remote students + remote telescope

= perfect match?

• 2009 New robotic dome

• 2010 New telescope (17 inch reflector)

• 2011: New main imaging camera (4kx4k CCD)

• PIRATE is now semi-autonomous and used in main-stream OU teaching and research

PIRATE in research

• Photometric monitoring of variable stars

• Transient search – novae in M31

– Gaia transient alert network facility

• Exoplanet transit candidate winnowing for SuperWASP and QES

• Serendipitous science

PIRATE published

• Faedi et al 2012, A&A, submitted (new planets WASP-54b, 56b, 57b)

• Haswell et al 2012, ApJ 760, 70 (second HST visit of WASP-12)

• Faillace et al 2012, JBAA, in press (near-contact binary)

• Rodda et al 2012, JBAA, in press (chromospherically active binary)

• Bloom et al 2012, ApJ Letters,744, L17 (supernova SN2011fe)

• Holmes et al 2011, PASP 123,1177, (PIRATE commissioning)

• Lucas & Kolb 2011, JBAA 121, 265 (software architecture)

• Fossati et al 2010 ApJL (HST visit of WASP-12)

• 8 ATel or CBET notes (M31 novae)

© Hans Deeg

Searching for extrasolar planets: the transit method

SuperWASPis the most successful exoplanet search project (80 confirmed planets)

Identifies 100-200 promising “A”candidates per year – but many are false positives

observed 80 A candidates since June 2011, to identify false positives

Expensive high-resolution spectroscopyat large telescopes (OHP, ESO La Silla)

Eclipsing brown dwarf binaries

Grazing eclipses of stellar binaries

Blends:background eclipsing binaries BEBs

Contaminants

SuperWASP: EB blend

HAT-P-20b

top: PIRATEbottom: SuperWASP

TReS-2bTReS-3bXO-1b

Sci

en

ce 4

Ja

n 2

01

3 i

ssu

e

Earliest known measurement of supernova in M101

23/08/2011vs24/08/2011

23 August 2011:PIRATE captures supernova only 3 hrs after explosion

Supernova SN2011fe(also known as PTF11kly)in M101

at 6.4 Mpc the closesttype Ia supernova for 40 years

SN2011fe

t0 + 4 hr

1 ar

cmin

Teff = 4000 K Teff = 7000 K

A

PIRATE/Clear

Bloom et al, 2012, ApJ Letters 744, L17(complements Nugent et al 2011,

Nature 480, 344)

PIRATE measurement shows that exploding object’s radius is smaller than 0.02 R

�

It must be a white dwarf.

PIRATE in OU teaching

• Third-level module “Astrophysics” (S382) – project

– At least 3 observing nights per student, over a period of 2

months (about 60 students)

– Outcome is a collaborative group report (10 students) with

research-grade data on a periodic variable star

• Second-level module “Practical Science” (S288)

– 1 observing night per student (15 nights, 60 students)

– Measurement of star cluster properties

• Observer teams of 2-4 students in Skype contact control PIRATE from home

S382 2010Castor groupresults

RS CVn system1SWASPJ160248.22+252038.2

SWASP J1628+10, pre-helium WD Faillace et al 2012July/August 2012 data

http://pirate.open.ac.uk

Follow us

on Twitter

@PirateOU

on facebook

Open University PIRATE Facility

: Overview - hardware

PIRATE Mark 2:• PlaneWave CDK17 0.42m • SBIG STX-16803

(4k x 4k 9µ pixels)• ƒ/6.8• F.O.V 43’ x 43’• Plate scale: 0.64’’ pixel-1

PIRATE Mark 1:• Celestron C14 0.35m SCT• SBIG STL-1001E • (1k x 1k 24µ pixels)• Paramount ME GEM• ƒ/11• F.O.V 22’ x 22’• Plate scale: 1.21’’ pixel-1

: Overview - software

http://pirate.open.ac.uk

• False positive elimination in A candidates (Holmes, Busuttil, Bochinski, Kolb & Haswell)

• about 60 sources observed since June 2011

PIRATE for SuperWASP

60cm PTST in Mallorca


60cm at MPE Garching Germany



Summary Part II: PIRATE

� Telescopes Robotic telescope for teaching and

complementing large telescope projects

� PIRATE � Open University 43 cm Telescope @ OAM

� Versatile small telescope

� Two new 60cm Telescope Projects

� PTST � Hamburg University telescope @ OAM,

Mallorca, Spain

� MPE/MPA/TUM Telescope, Garching, Germany

DADOS Spectrograph: Motivation

Develop a Spectrograph for use in a physics or astronomy

lab course with following characteristics:

– Easy and Flexible to use:

• Eyepiece

• Webcam

• CCD Camera

• Digital Camera

– Selectable spectral resolution (i.e. different gratings)

– Selectable spectralrange

– Light and compact

– Built in possibility to guide


The resulting spectrograph


The optical paths


• Prism � Rainbow

• Transmissiongrating

• Reflectiongrating

How are Spectra formed?


continuum spectrum

emission line spektrum

absorption line spektrum

Zum Leuchten angeregtes Gas:

- Energies saving lamps

- Flourescent lamps

- Neon lamps

comparable to licht from planetay Nebulae

incandescent lamp : in front a

- Dense / cool gas

- Filter

comparable to solar light (Fraunhofer lines)

- Classic incandescent lamp

- Halogen lamp

- LEDs

Study different kind of light sources/Spectra

• with eyepiece and eye / Webcam

� rough classification

Qualitative Analysis of Spectra

Spectra obtained with the 200line/mm Grating

Spectra obtained with the 900line/mm Grating


• Using Cameras (CCD) and data analysis software

� very detailed

Procyon AldebaranHalpha

Quantitative Analysis of Spectra


– Every day lamps• Incandescent lamps � continuum

• Energy saving/ Flourescent lamp � Lines + continuum

• Neon lamps � Lines

• LEDs � continuum around LED color

• Laser � single Lines

– Astronomical Objects: • Sun � Fraunhofer lines = Absorption lines

• Planets � Absorption bands

• Comets � Emission lines

• Stars � similar to Sun

• Nebulae � Emission lines

Analysing the light


Sample SpectraComparison of street lamp spectra with the City+Airport lamps of „Palma de Mallorca“

Wavelength

Inte

nsity


A Wolf Rayet Star Spectrum


Every day Spectra


Astronomical Spectra


Spectral Classification


Doppler Shifts in H-alpha line in β Aurigae


BACHES first presentation

77

ESO Messenger Sept. 2007 129, 63

Gerardo Avila, ESO

Vadim Burwitz, MPE

Carlos Guirao, ESO

Jesus Rodriguez, ESO

Raquel Shida, ESO

Dietrich Baade, ESO

Vadim Burwitz MPE Garching

BACHES first presentationESO Messenger Sept. 2007 129, 63

78

Evolution of Hα and Hβ lines in the Be star ζ Tau (HD 37202) over 44 days

Orbital period 132.97 days


BACHES first comercial Prototype

by Baader Planetarium GmbH

79Vadim Burwitz MPE Garching

BACHES on a telescope


BACHES Solar Spectrum with a Canon EOS 400D



BACHES Solar Spectrum mit Canon EOS 400D

82

Na I

Mg I

Hαααα


BACHES Solar Spectrum mit Canon EOS 400D

83

Na I

Mg I

Hαααα

BACHES Solar Spectrum with a Canon EOS 400D


Selectable BACHES or CCD Imager


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