ASTRONOMIA DE RAIGS X D'OBJECTES COMPACTES: ASTRONOMIA DE RAIGS X D'OBJECTES COMPACTES:
LA GAL.LÀXIA EN CONDICIONS EXTREMESLA GAL.LÀXIA EN CONDICIONS EXTREMES
Glòria SalaGlòria Sala
Grup d'Astronomia i AstrofísicaGrup d'Astronomia i Astrofísica
DFEN-EUETIBDFEN-EUETIB
DFEN. 2 de Febrer de 2010.
Per què ens calen observatoris espacials?
Observatoris terrestres: radiotelespistelescopis optics i infrarroig properraigs gamma de molt altes energies (Cherenkov)
telescopis Cherenkov
MAGIC
telescopis òptics
VLT
Per què ens calen observatoris espacials?
Observatoris terrestres: radiotelescopistelescopis optics i infrarroig properraigs gamma de molt altes energies (Cherenkov)
radiotelescopistelescopis Cherenkov
MAGIC
Per què ens calen observatoris espacials?
Observatoris astronòmics espacials
IR: Spitzer (3-180 microns)
Per què ens calen observatoris espacials?
Observatoris astronòmics espacials
IR: Spitzer (3-180 microns)
Raigs GAMMA:INTEGRAL (15 keV – 10 MeV)Raigs X:
XMM-Newton (0.5 keV – 10 keV)
COMPACT OBJECTS: fossiles of the stellar evolutionCOMPACT OBJECTS: fossiles of the stellar evolution
COMPACT OBJECTS: fossiles of the stellar evolutionCOMPACT OBJECTS: fossiles of the stellar evolution
Main sequence stars
OBJECTES COMPACTESOBJECTES COMPACTES
NANA BLANCA: • Estructura suportada per la pressió d'electrons degenerats.
• Massa màxima, massa limit de Chandrasekhar: 1.4 masses solars
● Radi similar al de la Terra
OBJECTES COMPACTESOBJECTES COMPACTES
• Massa: 1.4 – 2.1 masses solars● Radi: uns 10 kms• Equació d'estat encara desconeguda, hi ha diversos models però cap confirmat =>
La determinacio observacional de M i R delimita la possible equació d'estat
Oezel, Nature 2005
OBJECTES COMPACTESOBJECTES COMPACTES
FORAT NEGRE:
• Absència de superfície fisica.
• Massa superior a 3 masses solars en un radi inferior al seu radi de Schwarzschild: 2GM/c2
(3 km per cada massa solar)
WHAT DO THEY LOOK LIKE?WHAT DO THEY LOOK LIKE?
1. Isolated compact objects:1. Isolated compact objects:
Thermal UV emission while cooling down after formation
WHAT DO THEY LOOK LIKE?WHAT DO THEY LOOK LIKE?
1. Isolated NS1. Isolated NS
Low magnetic field:thermal (blackbody) Xray emission while cooling down.
High magnetic field, MAGNETARS: nonthermal (synchrotron) emission arising from “starquakes” => Xray and soft gammmaray flares (SGRs)
.... but... only Xrays and gammarays?
• Very fast optical variability, 0.3-0.4 s => emission region < 100 000 km.
• From X-ray data => located in our Galaxy
• Non- thermal emission => too fast variations of flux for thermal
“Swift J1955: Very fast optical flaring from a possible new magnetar”
Stefanescu, Kanbach, Slowikowska, Greiner, McBreen & Sala. Nature, 455, 503 (2008)
Magnetars: isolated NS with high magnetic fieldMagnetars: isolated NS with high magnetic field
Swift J1955 is probably the first individual of a new class of neutron star: an intermediate stage between
active SGRs (magnetars, young neutron stars) and dim isolated (old) neutron stars.
No other objects know in
the sky shows a similar
behaviour in the optical.
But the optical light curve
reminds of the X-ray light
curve of magnetars
SGR0501+4516. X-ray light curve (XMM/EPIC)
Rea et al. MNRAS 2009 in press (arXiv. 0904.2413)
Swift J1955: Optical light curve (OPTIMA)
Stefanescu et al. Nature 2008
Stefanescu, Kanbach, Slowikowska, Greiner, McBreen & Sala. Nature, 455, 503 (2008)
WHAT DO THEY LOOK LIKE?WHAT DO THEY LOOK LIKE?
1. Isolated compact objects:1. Isolated compact objects:
“Black”, no emission Can be detected in microlensing eventsOR If located in a BINARY SYSTEM
Low magnetic field; thermal Xray emission while cooling down High magnetic field, MAGNETARS: nonthermal Xray flares
Thermal UV emission while colling down after formation
X-ray binaries
Secondària
Primària
Black hole or neutron star
Binària de raigs X (Xray binary)
fonts de raigs X més brillants del cel el disc d'acreció és el principal responsable de l'emissió de raigs X
Objecte compacte: estel de neutrons o forat negre
Estel secondari que li transfereix material ric en H, formant un disc d'acreció
Evolució estel.lar en estels binaris
Secondària
Primària
Segons la massa de l'estel primari:
binàries amb forat negre (Xray binary)
binàries amb estrella de neutrons (Xray binary)
binàries amb nana blanca (Cataclysmic variable)
compact objectSupernova o PN
Evolució estel.lar en estels binaris
Secondària
Primària
Segons la massa de l'estel primari:
binàries amb forat negre
binàries amb estrella de neutrons
binàries amb nana blanca (variables cataclísmiques)
compact objectSupernova o PN
Galactic Xray binaries are the brightest Xray sources in the sky
Contain a compact accreting object, either a neutron star or a blackhole
Blackhole binaries Blackhole binaries
~20 contain dynamically confirmed stellar black holes (BHs).
other ~20 are black hole candidates (BHCs).
Most are Xray transients, and many with only one Outburst detected!!
Any new Xray transient may be a new BHC!
Strategy:
Trigger XMMNewton Target of Opportunity Observations (TOOs) of new Xray transients
(mainly based on RXTE/ASM monitoring) to identify new Blackhole candidates.
Blackhole binaries Blackhole binaries
XTE J1817330: a bright and soft Xray transientXTE J1817330: a bright and soft Xray transient
Discovered on 26 January 2006 with RXTE (Remillard et al. ATel#714) @ 0.93 (+/0.03) Crab!!
Maximum of 1.9 Crab on 28 January 2006.
XTE J1817330: a bright and soft Xray transientXTE J1817330: a bright and soft Xray transient
Discovered on 26 January 2006 with RXTE (Remillard et al. ATel#714) @ 0.93 (+/0.03) Crab!!
Maximum of 1.9 Crab on 28 January 2006.
Exponential decline with efolding time of 27 days.
XTE J1817330: a bright and soft Xray transientXTE J1817330: a bright and soft Xray transient
Discovered on 26 January 2006 with RXTE (Remillard et al. ATel#714) @ 0.93 (+/0.03) Crab!!
Maximum of 1.9 Crab on 28 January 2006.
Exponential decline with efolding time of 27 days.
Radio counterpart discovered, with steep spectrum and fading a factor 2.6 in 4 days (Rupen et al. ATel#717,#721)
XTE J1817330: a bright and soft Xray transientXTE J1817330: a bright and soft Xray transient
Discovered on 26 January 2006 with RXTE (Remillard et al. ATel#714) @ 0.93 (+/0.03) Crab!!
Maximum of 1.9 Crab on 28 January 2006.
Exponential decline with efolding time of 27 days.
Radio counterpart discovered, with steep spectrum and fading a factor 2.6 in 4 days (Rupen et al. ATel#717,#721)
Infrared counterpart with K=15.0 in outburst (D'Avanzo et al. ATel#724)
XTE J1817330: a bright and soft Xray transientXTE J1817330: a bright and soft Xray transient
Discovered on 26 January 2006 with RXTE (Remillard et al. ATel#714) @ 0.93 (+/0.03) Crab!!
Maximum of 1.9 Crab on 28 January 2006.
Exponential decline with efolding time of 27 days.
Radio counterpart discovered, with steep spectrum and fading a factor 2.6 in 4 days (Rupen et al. ATel#717,#721)
Infrared counterpart with K=15.0 in outburst (D'Avanzo et al. ATel#724)
Optical counterpart with g'=14.93 (Torres et al. Atel#733). g'K colour supports low reddening to the source.
XTE J1817330: a bright and soft Xray transientXTE J1817330: a bright and soft Xray transient
Discovered on 26 January 2006 with RXTE (Remillard et al. ATel#714) @ 0.93 (+/0.03) Crab!!
Maximum of 1.9 Crab on 28 January 2006.
Exponential decline with efolding time of 27 days.
Radio counterpart discovered, with steep spectrum and fading a factor 2.6 in 4 days (Rupen et al. ATel#717,#721)
Infrared counterpart with K=15.0 in outburst (D'Avanzo et al. ATel#724)
XTE J1817330: a bright and soft Xray transientXTE J1817330: a bright and soft Xray transient
Optical counterpart with g'=14.93 (Torres et al. Atel#733). g'K colour supports low reddening to the source.
INTEGRAL detection in 20150 keV band (Shaw et al. ATel#734)
Discovered on 26 January 2006 with RXTE (Remillard et al. ATel#714) @ 0.93 (+/0.03) Crab!!
Optical counterpart with g'=14.93 (Torres et al. Atel#733). g'K colour supports low reddening to the source.
Maximum of 1.9 Crab on 28 January 2006.
Exponential decline with efolding time of 27 days.
Radio counterpart discovered, with steep spectrum and fading a factor 2.6 in 4 days (Rupen et al. ATel#717,#721)
Infrared counterpart with K=15.0 in outburst (D'Avanzo et al. ATel#724)
INTEGRAL detection in 20150 keV band (Shaw et al. ATel#734)
SwiftUVOT detection in UV: U=14.4, UVW2=14.9 (Steeghs et al. ATel#742)
XTE J1817330: a bright and soft Xray transientXTE J1817330: a bright and soft Xray transient
Discovered on 26 January 2006 with RXTE (Remillard et al. ATel#714) @ 0.93 (+/0.03) Crab!!
Optical counterpart with g'=14.93 (Torres et al. Atel#733). g'K colour supports low reddening to the source.
Maximum of 1.9 Crab on 28 January 2006.
Exponential decline with efolding time of 27 days.
Radio counterpart discovered, with steep spectrum and fading a factor 2.6 in 4 days (Rupen et al. ATel#717,#721)
Infrared counterpart with K=15.0 in outburst (D'Avanzo et al. ATel#724)
INTEGRAL detection in 20150 keV band (Shaw et al. ATel#734)
SwiftUVOT detection in UV: U=14.4, UVW2=14.9 (Steeghs et al. ATel#742)
Chandra finds low absorption, ~1021 cm2
(Miller et al. ATel#749)
XTE J1817330: a bright and soft Xray transientXTE J1817330: a bright and soft Xray transient
Discovered on 26 January 2006 with RXTE (Remillard et al. ATel#714) @ 0.93 (+/0.03) Crab!!
Maximum of 1.9 Crab on 28 January 2006.
Exponential decline with efolding time of 27 days.
Radio counterpart discovered, with steep spectrum and fading a factor 2.6 in 4 days (Rupen et al. ATel#717,#721)
Infrared counterpart with K=15.0 in outburst (D'Avanzo et al. ATel#724)
INTEGRAL detection in 20150 keV band (Shaw et al. ATel#734)
SwiftUVOT detection in UV: U=14.4, UVW2=14.9 (Steeghs et al. ATel#742)
XTE J1817330: a bright and soft Xray transientXTE J1817330: a bright and soft Xray transient
Chandra finds low absorption, ~1021 cm2
(Miller et al. ATel#749)
Optical counterpart with g'=14.93 (Torres et al. Atel#733). g'K colour supports low reddening to the source.
Discovered on 26 January 2006 with RXTE (Remillard et al. ATel#714) @ 0.93 (+/0.03) Crab!!
Optical counterpart with g'=14.93 (Torres et al. Atel#733). g'K colour supports low reddening to the source.
Maximum of 1.9 Crab on 28 January 2006.
Exponential decline with efolding time of 27 days.
Radio counterpart discovered, with steep spectrum and fading a factor 2.6 in 4 days (Rupen et al. ATel#717,#721)
Infrared counterpart with K=15.0 in outburst (D'Avanzo et al. ATel#724)
INTEGRAL detection in 20150 keV band (Shaw et al. ATel#734)
SwiftUVOT detection in UV: U=14.4, UVW2=14.9 (Steeghs et al. ATel#742)
XTE J1817330: a bright and soft Xray transientXTE J1817330: a bright and soft Xray transient
Chandra finds low absorption, ~1021 cm2
(Miller et al. ATel#749)
Discovered on 26 January 2006 with RXTE (Remillard et al. ATel#714) @ 0.93 (+/0.03) Crab!!
13 March 2006
20 ks exposure
0.310.0 keV
XMMNewton TOOXMMNewton TOO
XTE J1817330: XMMNewton observation XTE J1817330: XMMNewton observation
XMMNewton: OM, EPICpn and RGS spectra
OM, U filterOM, UVW1 filter
EPICpn, Burst mode
RGS1, order 2
RGS1, order 1
EPICpn residuals
OM and RGS residuals
Sala et al . A&
A, 4 73, 561 ( 2007)
XTE J1817330: XMMNewton observation XTE J1817330: XMMNewton observation
EPICpn residuals
Spectral Model
Hot corona(CompTT, kTe=50keV)
τ=0.15(±0.02)Total absorbed modelNH=1.55(±0.05)×1021 cm2
Thermal accretion disk, unabsorbed.
Contributes to UV and optical Thermal accretion disk(diskpn, Rin=6Rg, fixed)kTin=0.70(±0.01) keV
L (0.410keV) @1kpc= 1.2(±0.1) ×1036 (D/1kpc)2 erg s1
Column density is compatible with the average galactic column density: minimum distance is 1 kpc
Sala et al . A&
A, 4 73, 561 ( 2007)
Models: diskpn, Gierlinski et al 1999, MNRAS, 309, 496CompTT , Titarchuk 1994, ApJ, 434, 313
Assuming it was at LEdd at maximum in RXTE lightcurve, corresponding L at time of XMM observation (a factor 6 fainter, 16% Ledd ).
Assuming it was at a lower limit of 30% the LEdd at maximum, corresponding L at time of XMM observations (5% Ledd ).
Sala et al . A&
A, 4 73, 561 ( 2007)
XTE J1817330: mass constraint XTE J1817330: mass constraint
Assuming =1.7, 1.8M
⊙< M < 6M
⊙
Evolució estel.lar en estels binaris
Secondària
Primària
Segons la massa de l'estel primari:
binàries amb forat negre
binàries amb estrella de neutrons
binàries amb nana blanca (variables cataclísmiques)
compact objectSupernova o PN
Accreting neutron stars vs accreting black-holes
Neutron StarDonor Star(“normal” star)
Accretion Disk
Neutron stars can have strong magnetic fields
If weak magnetic field:
Bright Xrays from accretion disk, like blackhole binaries, but can get closer to compact objects = > hotter
Has a physical surface where Hrich matter from donor accumulates => fresh fuel, when ignites => Type I Xray burst
Accreting neutron stars
Neutron star Xray binariesNeutron star Xray binaries
Xray pulsarsRegular pulses withperiods of 1 1000 s
High magnetic fields channel accretion flow on to magnetic poles
Xray pulsarsRegular pulses withperiods of 1 1000 s
High magnetic fields channel accretion flow on to magnetic poles
Xray burstersFrequent Outbursts of 10100s durationwith lower, persistent Xray flux inbetween
Xray burstersFrequent Outbursts of 10100s durationwith lower, persistent Xray flux inbetween
Type I Xray burstsTHERMONUCLEARBurst energy proportionalto duration of preceedinginactivity period
By far most of the bursters
Type I Xray burstsTHERMONUCLEARBurst energy proportionalto duration of preceedinginactivity period
By far most of the bursters
Type II Xray burstsSPASMODIC ACCRETIONBurst energy proportionalto duration of followinginactivity period
“Rapid burster” (also shows Type I)and GRO J174428 (Rapid Pulsar)
Type II Xray burstsSPASMODIC ACCRETIONBurst energy proportionalto duration of followinginactivity period
“Rapid burster” (also shows Type I)and GRO J174428 (Rapid Pulsar)
weak magnetic field
strong magnetic field
Accreting neutron stars: Type I X-ray bursts
Unstable, explosive burning in bursts (release over short time)
Burst energythermonuclear
Persistent fluxgravitational energy
Type I X-ray BurstsType I X-ray Bursts
Accreting neutron stars: Type I X-ray bursts
• 1036 1038 erg/s• duration 10 s – 100s• recurrence: hoursdays• regular or irregular
Type I X-ray BurstsType I X-ray Bursts
For nuclesynthesis studies and hydrodynamical models see works by Jordi José, Anuj Parikh and Fermin Moreno
Accreting neutron stars: Type II X-ray bursts.The Rapid Burster in March 2009
Time of Swift observations
Sala, Haberl, Pietsch, José & Parikh (2009)
Accreting neutron stars: type II X-ray burstsThe Rapid Burster in March 2009
Sala, Haberl, Pietsch, José, Parikh. Atel 1969 (2009)
100 s
Type II Xray bursts
Xr
ay fl
ux
Time (seconds)
Accreting neutron stars: The Rapid Burster in March 2009
Xr
ay fl
ux
Time (seconds)
Type I Xray Burst with Photospheric Radius Expansion
Accreting neutron stars: The Rapid Burster in March 2009
Xr
ay fl
ux
Time (seconds)
Type I Xray Burst with Photospheric Radius Expansion
Photospheric expansion => radiation pressure causes expansion => Eddington limit luminosity for this Neutron Star Mass =>
MEASURE MASS
Accreting neutron stars: The Rapid Burster in March 2009
Xr
ay fl
ux
Time (seconds)
Type I Xray Burst with Photospheric Radius Expansion
Accreting neutron stars: The Rapid Burster in March 2009
Xr
ay fl
ux
Time (seconds)
Type I Xray Burst with Photospheric Radius Expansion
After peak photosphere receedes => back to NS surface => at “touch down”: photosphericradius = neutron star radius =>
MEASURE RADIUSSala, Haberk, José et al, iIn preparation
Evolució estel.lar en estels binaris
Secondària
Primària
Segons la massa de l'estel primari:
binàries amb forat negre
binàries amb estrella de neutrons
binàries amb nana blanca (variables cataclísmiques)
compact objectSupernova o PN
X-ray emission from classical novae
1. SOFT (photon energy <1 keV):
- SOURCE: non-explosive H- burning in envelope left on the WD surface
- SPECTRUM: black-body-like, kTeff ~30-50 eV (Teff ~2-10×105 K)
- LUMINOSITY: L~105 X Solar ~ 1038 erg/s.
Ejected materialEjected material
WD2. HARD (photon energy 1-10 keV)
- SOURCE: shocks in expanding shell of ejecta
- SPECTRUM: thermal bremsstrahlung, kTeff ~ 1-10 keV
- LUMINOSITY: L~1033 erg/s.
3. HARD (photon energy 1-10 keV)
- SOURCE: hot accretion disk reestablished
- SPECTRUM: Thermal bremsstrahlung + fluorescent emission line from cold matterial
- LUMIINOSITY: L~1033-34 erg/s.
ROSAT X-ray observations of V1974 Cyg (Krautter et al. 1996).
Rise due to decrease ofAbsorption => timescale related to ejected mass
Time (days)
Xr
ay fl
uxExample 1. Soft X-ray emission due to hot atmosphere
(black-body-like spectrum).
1. Soft X-ray emission due to hot atmosphere
(black-body-like spectrum).
(Krautter et al. 1996).
Rise due to decrease ofabsorption
Energy (10 eV)
Xr
ay fl
ux
ROSAT X-ray observations of V1974 Cyg (Krautter et al. 1996).
Plateau, evolution path and duration related to white dwarf mass and envelope composition
Time (days)
Xr
ay fl
ux1. Soft X-ray emission due to hot atmosphere
(black-body-like spectrum).
Final decay due to fuel exhaustion, related to envelope mass left on WD after outburst
1. Soft X-ray emission due to hot atmosphere
(black-body-like spectrum).
Nova Cyg 1992(V1974 Cyg)
Comparison
of spectral evolution during
plateau and decay
with models
(Sala & Hernanz 2005a, A&A, 439, 1061)
provided limits on white dwarf mass
(0.9-1.0 Msun)
(Sala & Hernanz 2005b A&A, 439, 1057)
Nova Sgr 1998(V4633 Sgr)
Hard X-ray emission associated to the ejected material
(Hernanz & Sala 2007, The Astrophysical Journal, 664, 467)
Example 2. Hard X-ray emission due to schocked shell
(thermal bremsstrahlung spectrum)
WD
kT1
kT2 kT3
Energy (keV)
Xr
ay fl
ux
Ejected Ejected materialmaterial
WD
Nova Oph 1998(V2487 Oph)
Fluorescence FeKα line,signature of accretion
disc => CV-like emission =>, accretion reestablished less than
1000 days after the nova explosion
Low THigh T
Fe Kα
Example 3. Hard X-rays due to accretion disk
(thermal bremsstrahlung spectrum)
Energy (keV)
Xr
ay fl
ux
(Hernanz & Sala 2002, Science 664, 467)
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