Approaches to study the EOS for neutron star matter from X-ray - - PowerPoint PPT Presentation

Approaches to study the EOS for neutron star matter from X-ray astronomy satellites
 (Report from Group C01)

Tadayuki Takahashi, Tadayasu Dotani, Masahiro Tsujimoto Institute of Space and Astronautical Science (ISAS)/JAXA Toru Tamagawa RIKEN Yasunobu Uchiyama Rikkyo Univ.

( Collaborators: Hirokazu Odaka, Teruaki Enoto, Dmitry Khangulyan, Atsushi Harayama, Hirokazu Ikeda, Masachika Iwai, Chris Done, Hiroki Yoneda)

Introduction (by Takahashi) 5min Topic A: Performance of the ASTRO-H micro-calorimeter (by Tsujimoto) 10 min Topic B: X-ray Observations to study the EOS (by Dotani) 10 min

Kazuo Maxima (RIKEN), Teruaki Enoto (Kyoto U.)

Program for Specific topics (talks)

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

Topics covered in the C-01 research project

1) Neutron star observations with X-ray missions such as ASTRO-H. (1) Prepare for high-resolution observations by using the micro-calorimeter (SXS)

• nboard ASTRO-H.


(e.g. high counting rate Pulse Shape Processor (PSP)) (2) Prepare for wide-band observations from 0.3 keV to 600 keV by using SXI (X-ray CCD), HXI (CdTe DSD) and SGD (Si/CdTe Compton Camera) onboard ASTRO-H (e.g. ground calibration) (3) Find good targets to be observed by ASTRO-H based on studies by using archival data from Chandra, XMM, Suzaku.

SXS Dewar HXI Test Model

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

Topics covered in the C-01 research project

2) Study new X-ray missions, to open up a new field for studying neutron star matter (1) Participate in international mission proposals

• 1. NICER (Enoto’s talk)
• 2. PRAXyS
• 3. LOFT

(2) Develop new detectors for future X-ray missions (Si and CdTe Imaging detectors wth high counting & high resolution capability) 3) MonteCarlo calculation code to simulate the emission from neutron star surface (under strong magnetic field) 4) Use GeV Gamma-ray observatory (Fermi Satellite) to find another approach to study the neutron star.

X-ray Path in the MC Simulation of Accretion Column

T,Takahashi, “Recent Development of CdTe Imagers", Arizona, 25 Aug. 2016

ASTRO-H (Hitomi)

Chandra (Marshall et al. 2001)

2.7 ton/14 m

T,Takahashi, “Recent Development of CdTe Imagers", Arizona, 25 Aug. 2016

ASTRO-H (Hitomi)

Chandra (Marshall et al. 2001)

But lost its function

• n March 26, 2016

All mission instruments showed good performance as expected. Part A of this presentation (Tsujimoto)

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

New Missions (PRAXyS, NICER, LOFT)

7 . m f = 4 . 5 m X-ray mirror X-ray polarimeters deployable optical boom

PRAXyS (Polarimeter for Astrophysical X-ray Sources) Project

X-ray polarimetry can address the questions of:

• 1. X-ray emission point and mechanism of neutron stars (Meszaros+1998)
• 2. Vacuum birefringence in strong magnetic field of magnetars (Lai & Ho, 2003)
• 3. Inclination and magnetic inclination configuration of accreting millisecond

pulsars (Viironen & Poutanen, 2004)

Although these observations do not answer NS EOS directly, they contribute to the precise modeling of emission mechanism and environment of NSs.

2014/12: Proposed to NASA's Small Explorer program 2015/07: Selected for Phase A study (three projects selected) 2016/07: Submitted Conceptual Study Report to NASA HQ 2017/02: Down selection (only one project will be selected.) 2020/08: Launch

preflight X-ray polarimeter

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

Figure 6.9:

˙

GeV/TeV Gamma-ray Observations of Pulsars/Pulsar Wind Nebulae

Number of gamma-ray pulsars detected with Fermi-LAT is 205! (as of 2016 Feb), including PSRJ0537-6910 in LMC (Large Magellanic Cloud).

Gamma-ray observations can constrain NS’s “moment of inertia, I”.

Some Radio-quiet pulsars show large Gamma- ray luminosity close to its Spin-down power:

I = kMR2

Spin-down power: gamma-ray luminosity of pulsar/pulsar wind nebula

˙ E = −IΩ ˙ Ω = 4π2I ˙ PP −3

pulse measurement
 (radio/gamma) Then, moment of inertia, I, can constrain EOS.

Lγ=E

.

for I0

Fermi Satellite

Abdo et al. (2013)

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

Topic A: Performance of the ASTRO-H micro-calorimeter (Masahiro Tsujimoto) Topic B: X-ray Observations to study the EOS (Tadayasu Dotani)

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

Topic A: Performance of the ASTRO-H micro-calorimeter (SXS)

• X-ray micro-calorimeter array.
• 6x6 pixels : 10.6 μm HgTe absorber +

Si thermometer at 50 mK.

• Measure T increase (about 1 mK) by

energy deposit of individual X-ray photons (about 1 fJ).

• Multi-stage cooling using (a) 3 ADRs,

(b) 4 Stirling coolers, (c) 1 Joule- Thomson cooler, (d) 30 litter liquid He.

• Thermal relaxation time scale : about

5 ms = 200 Hz/pixel

熱 浴 Ts (約 50 m K)

約 8 m s

Array (5mm2)

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

Onboard Digital Electronics

• Waveform : ADU(t) is cross-correlated with a template to derive energy by
• ptimum filtering.
• Onboard digital electronics is the bottleneck in total throughput. 150 Hz/

array (about 1/10 of Crab flux) required.

• Efforts for high CR performance made in development phase.

Sample ADU(t) at 4 Hz/pixel

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

In-orbit Performance

• Energy resolution : 4.9 eV (FWHM) at 5.9 keV.
• Energy range : 2-20 keV.

Perseus cluster of galaxies (Hitomi collab. 2016, Nature) Hitomi SXS Suzaku XIS Cr XXIII Mn XXIV Fe XXV Fe XXVI Ni XXVII Fe XXV

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

High CR observation

• Crab nebula observed.
• About 200 Hz events

processed.

• Most illuminated pixels

have >25% live time.

• Superb spectroscopic

performance verified for a high CR observation.

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

Spectroscopy of high CR

• Most stringent upper limit for X-ray line emission from

Crab, a super-nova remnant.

• Constraint on the origin of this super nova SN1054.

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

Summary (Topic A)

• SXS worked successfully in the orbit. No major problems.

The first satellite-borne X-ray micro-calorimeter to

• bserve X-ray sources.
• Superb spectroscopic performance achieved.

Tremendous advantages beyond all other X-ray spectrometers for various topics, including NS.

• Efforts to make high CR observations paid off. Verified

with Crab.

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

Topic B: X-ray Observations of Neutron Stars to Study the EOS

Importance of X-ray observations

In order to get information on the radius, we need to

• bserve radiation from the neutron star surface.

Thermal emission from the mass-accreting neutron stars

T = 1.8 M M⊙ ⎛ ⎝ ⎜ ⎞ ⎠ ⎟

1/4

R 10km ⎛ ⎝ ⎜ ⎞ ⎠ ⎟

−1/2

L LEdd ⎛ ⎝ ⎜ ⎞ ⎠ ⎟

1/4

keV

X-ray emission

X-ray observations are essential to get information on radius of the neutron stars.

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

Observational Methods to probe the neutron star radius

(1)Mass-Radius Ratio

Gravitational redshift of the atomic features in the X-ray spectrum from the NS surface.

X-ray bursts (2) Radius (and Mass)

Light bending and Doppler boosting Pulse profile of the millisecond pulsars with thermal emission

NICER: Talk by T. Enoto

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

Low-mass X-ray binaries and X-ray Bursts

Low-mass star Accretion disk

Neutron star

Duration : ~10-100 sec Interval : hours ~ days Luminosity : ≤Eddington limit

~1038 erg/s

Burst oscillation is used to infer the spin frequency.

X-ray bursts

Run-away nuclear reaction of He (H) on the NS surface Properties of the NS in LMXBs

• Bs<109-1010 G
• Spin ~ 200-600 Hz
• T < 0.1 ~ 2 keV
• persistent / Transient

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

Why X-ray bursts?

Mean composition of the envelope

Parikh et al. 2013, Prog. Part. Nucl. Phys. 69, 225

Mass number A

Metal poor Solar

(1) Enrichment of heavy elements in the atmosphere

Heavy elements up to Z~50 are produced in X-ray bursts.

Atomic features in the spectra. (2) Temperature structure of the atmosphere

Photons created at the bottom of the atmosphere will go through the relatively cool layer, where absorption lines/edges are formed.

Caveat: Rapid spin of the neutron star X-ray bursters: typical spin 200-600 Hz Spectral features may be smeared out.

We need burst sources with slow spin.

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

Candidate 1: A unique burst source Terzan 5 X2

Cavecchi et al. 2011, ApJ, 740, L8

Frequency (Hz)

10.0 11.5

Time (sec) 100 200

A transient source in the globular cluster Terzan 5.

Terzan 5 X2

Spin frequency: ~11Hz Magnetic field: 109~1010 G

Caveat

Terzan 5 X2 is a transient source. Outburst occurred in 2010 for 55 days. Clean and clear results are expected. Independent of distance, radiation isotropy, details of the emission region, continuum models Narrow lines are expected from the NS atmosphere

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

Candidate 2: A young burst source Cir X-1

Cir X-1 : X-ray burst source with high-mass companion Chandra observation (Heinz et al. 2013, ApJ, 779, 171)

• Association with SNR is revealed.
• SNR age is estimated to be <4600 yr.

SNR associated with Cir X-1 Chandra X-ray image (1-3 keV)

• No spin-up due to mass-accretion

is expected for such a young neutron star.

• It should preserve the original spin

frequency at birth, which may be a few tens Hz.

Heinz et al. 2013, ApJ, 779, 171

Caveat

No X-ray burst occur in the high state, which may last ~5-10 yrs.

Slow rotator

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

Search existing burst data for spectral features Suzaku archive data: 2005 - 2015

We searched all the Suzaku archive data for the spectral features in the bursts, and found a unique source.

GRS1747-312 : Talk by M. Iwai

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

Summary (Topic B)

• 1. We have studied various methods to obtain information
• n the NS radius, and selected the best one:

Parameters: Gravitational redshift Methods: Atomic features in the burst spectra Targets: T5X2, Cir X-1

• 2. We searched existing burst data for the spectral

features, and found a candidate from GRS1747-312.

• 3. It is important to get a wide band coverage to

understand various types of neutron stars, eg. magnetars, pulsar wind nebulae, and X-ray binaries. This was realized with ASTRO-H for 0.3 - 600keV, which may be utilized for the future mission.

T,Takahashi, T. Dotani, M. Tsujimoto, T. Tamagawa, Y. Uchiyama, NSMAT 2016, Nov. 21-24, 2016

Summary

• We succeeded to demonstrate the power of X-ray micro-calorimeter

during the first one-month operation of ASTRO-H (Hitomi) before the loss of the spacecraft.

• SXS worked successfully in the orbit. as the first satellite-borne X-ray

micro-calorimeter to observe X-ray sources. Tremendous advantages beyond all other X-ray spectrometers for various topics, including NS.

• We have identified candidates as the sources to study the EOS of

neutron star matter.

• We participated in and contributed to future X-ray mission proposals,

such as PRAXyS, NICER and LOFT.

• We successfully expanded our scope to GeV gamma-ray
• bservations (Fermi) to constrain the M/R ratio.