LOFT: Large Observatory For X-ray Timing

Transcription

1 LOFT: Large Observatory For X-ray Timing A mission selected by ESA as a candidate CV M3 mission Devoted to X-ray timing and designed to investigate the space-time around collapsed objects S. Zane (MSSL/UCL) on behalf of the LOFT Consortium Kathmandu, October

2 Missions & discoveries LOFT (ESA) NICER (NASA) ASTROSAT (ISRO) HTMT (China) 100,000 cm cm cm kev, 5000 cm 2

3 LOFT in 1 plot: 10 LOFT 8 Effective area [m 2 ] RXTE-PCA ASTROSAT-LAXPC XMM-EPIC-pn Energy [kev] S/N Area, 1 sigma becomes 20 sigma (for uncoherent detection regime)

4 The LOFT consortium THE LOFT SCIENCE TEAM Jan-Willem den Herder SRON, the Netherlands Marco Feroci INAF/IASF-Rome, Italy Luigi Stella INAF/OAR-Rome, Italy Michiel van der Klis Univ. Amsterdam, the Netherlands Martin Pohl Univ of Geneve, Switzerland LAD Silvia Zane MSSL, United Kingdom WFM (LAD) Margarita Hernanz IEEC-CSIC, Spain (WFM) Søren Brandt DTU, Copenhagen, Denmark (WFM) Andrea Santangelo Univ. Tuebingen, Germany Didier Barret IRAP, Toulouse, France Alex Short ESA Carlos Van Damme/ Mark Ayre ESA David Lumb ESA

5 Large area detector (LAD): - 6 deployable panels - 10m 2 collimated area, kev, SSD+MCP, - time res 10µs, - E ~ 260 The LOFT payload LAD WFM Bus Wide field Monitor (WFM): - coded mask detector kev, 50% sky - source localization 1 - visibility to identify strong transients Solar Array

6 Silicon Drift Detector heritage of the Inner Tracking System of the ALICE experiment, Large Hadron Collider (CERN) INFN Trieste, in collaboration with Canberra Inc., designed, built, tested and calibrated 1.5 m 2 of SDD detectors (~300 units), now operating since 2 yrs. High TRL, proven mass production. LAD has a mass per unit area ~30kg/m2 (the largest predecessor, RXTE/PCA, has >100kg/m2) Thickness 450 µm Monolithic Active Area 76 cm 2 Low power requirement (~60 W/m2) Good spectral performance 260 ev FWHM Drift time <5 µs Single-channel area 0.3 cm 2

7 . Unambiguous identification of the target source Built narrowing at Leicester the SRC field basing of view on by means of an aperture Heritage collimator, BC MIXS-C down to a level (typically ~1 ) large enough to allow for pointing uncertainties yet small enough to reduce X-ray the collimators aperture made background of capillary (cosmic diffuse X-ray plates, background) high Pb content and the glass risk of source confusion. a ~5 The mm LAD thick is sheet therefore of Lead designed glass as a classical collimated is perforated experiment. by a huge number of micro-pores, parallel 83 µm square cross section channels, ~17 µm septal thickness, giving an OAR of ~70% (Leicester)

8 LAD- Schematic Design Detector= SDD+FEE+Collimator (basic LAD detection element) The 6 Detector Panels (DP) are tiled with 2016 detectors, electrically and mechanically organized in groups of 16, (= the Modules). 21 Modules per Panel 16 Detectors per Module The assembly philosophy employs a hierarchical approach: Detector, Module, Detector Panel and LAD Assembly.

9 Achieving 10 m 2 effective area (~18 m 2 geometrical) modular and redundant approach: 16 independent detectors per Module 21 independent Modules per Detector Panel 6 independent Detector Panels per LAD Total panel surface 21 m SDDs per panel 2016 SDDs in totals 1 MCP tiles per SDD

10 LOFT Wide Field Monitor 1820 cm 2 Si drift detectors 2-50 kev (-80 for b/g) 0.25 Crab in 3 sec, 2 mcrab in 60 ks 1 arcmin positions (5 arcmin res) ev energy resolution 10 µs time resolution, 1 µs absolute timing WFM

11 LOFT Wide Field Monitor 1820 cm 2 Si drift detectors 2-50 kev (-80 for b/g) 0.25 Crab in 3 sec, 2 mcrab in 60 ks 1 year sky map 1 arcmin positions (5 arcmin res) ev energy resolution 10 µs time resolution, 1 µs absolute timing WFM

12 LOFT burst alert system Automatic triggers for bright events on-board: - Few to few 10 triggers/ day: ~1 arcmin location via VHF network within 30 s (onboard to end user) - All triggers: - Full spectral and timing resolution - Pre-trigger data - Triggered data available within hr Expected: ~ 150 GRBs yr -1 ~ 5000 thermonuclear X-ray bursts yr -1

13 The LOFT Science Drivers: The LOFT LAD has an effective area ~20 times larger than the Proportional Counter Array onboard RossiXTE and a much improved energy resolution. Neutron Star Structure and Equation of State of ultradense matter: - neutron star mass and radius measurements - neutron star crust properties (Routine neutron star seismology) Strong gravity and the mass and spin of black holes - QPOs in the time domain - Relativistic precession - Fe line reverberation studies in bright AGNs Observations Observations!

14 LOFT objectives 1. Dense matter supranuclear EOS Pulse profiles Spin measurements Seismology msecpulsations, Seismics in XRB, SGR 2. Strong field gravity GR in action Broad Fe line variability Epicyclic motion QPO waveforms QPOs & Fe lines in XRB & AGN 3. Observatory science Broad-ranging programme using LOFT unique capabilities All three areas mainly open-time & proposal-driven

15 RXTE discovered the signals: Dense matter accreting millisecond pulsars thermonuclear burst oscillations SGR seismic oscillations (in giant flares) LOFT uses them to characterize neutron stars neutron star spin distribution [discover many more spins] pulse profile modeling [measure M and R] SGR seismic oscillations in intermediate flares [NS interior] AGN

16 Few simulations of the LAD capabilities Accreting MSP as SAX J Coherent pulsations/burst oscillations Poutanen and Gierlinski U (582 Hz) <5% uncertainty (90% confidence level) on mass and radius

17 Pulse profiles s Ray tracing from hot spot to Earth to constrain spacetime geometry Thermonuclear burst pulsars: simple hot spots heated from below A few bursts sufficient to measure M,R to 4, 3 % (instrumental) if geometry is favourable (Lo et al. LOFT simulation 2013). Lo et al. 2013

18 Do spins pile up at ~700 Hz? Faster spins directly constrain EOS True pile up constrains torque mechanisms (cf. Gusakov this meeting) grav. waves magnetic Current spin distribution Spin frequencies Discover spins to unprecedented sensitivity by three tested methods Accreting pulsar Thermonuclear pulsar Burst rise Burst decay

19 Additional Request: long pointed observations during activity but NOT on-axis... Courtesy of GL Israel QPOs and Ifs Shorter (by a factor of ~10-600), less energetic (by a factor of ) than GFs but more frequent (by a factor of ). 1s-long, 500-Crab IF (~3Crab on-axis) similar to those detected from SGR1900. Observed 30 o off-axis. Strategy: Collecting a large number of IFs from different sources in order to reach a large enough statistics.

20 Strong gravity Previous missions discovered the signals: relativistic Fe lines (in binaries and AGN) dynamical and epicyclic timescale QPOs black hole high-frequency QPOs (barely) neutron star kilohertz QPOs BH&NS low-frequency QPOs LOFT uses them to probe strong field gravity Relativistic line profile variability Merges spectral / timing diagnostics Active into galactic one nucleus Tomography & reverberation Relativistic epicyclic motions Relativistic distortions of QPO waveforms AGN

21 Few simulations of the LAD capabilities LOFT simulation of a steady and variable Fe line ( MCG ), F=3mCrab, a=0.99, r in =1r g, r out =100r g, q=45, e~r -3, r sp =10r g, T orb =4 ks T exp =16 ks LOFT can map 4 phases (1000 s each) in four cycles M=3-4 x 10 6 M sun. a= R=0.98(0.02) r i n r out r sp

22 The high frequency QPOs in the BHC XTE J ν1=188 Hz, ν2=268 Hz, frac rms ν1= 2.8%, frac rms ν2=6.2% (Miller et al. 2001), flux = 1 Crab, RXTE Exposure 54 ks, significance 3-4σ. LOFT simulation: Texp=1 ks

23 BH high-frequency QPO Different models predict different frequency behaviour: Epicyclic Resonance (Abramowicz & Kluzniak 2001) Predicts fixed frequencies Epicyclic Resonance Model (Abramowicz & Kluzinak 2001) LOFT Rossi XTE Relativistic Precession (Stella et al 1999) Predicts variable frequencies LOFT Rossi XTE Diskoseismic modes (e.g. Lai&Tsang 2009) Alfven wave model (Zhang et al. 2005) Predict other dependencies on flux LOFT: distinguish between the models clinch the interpretation of the QPOs in terms of GR measure mass and spin of the black hole

24 Observatory Science As for RXTE/PCA (but at much higher sensitivity), with a high flexibility in its observing program, LOFT will also be an Observatory for virtually all classes of relatively bright sources. These include: X-ray bursters, High mass X-ray binaries X-ray transients (all classes) Cataclismic Variables Magnetars Gamma ray bursts (serendipitous) Nearby galaxies (SMC, LMC, M31, ) Bright AGNs The LOFT WFM will discover and localise X-ray transients and impulsive events and monitor spectral state changes, triggering follow-up observations and providing important science in its own. Useful for a broad range of studies in X-rays Synergies with many other instruments projected for the 2020 s

25 Observing program Source Type TOO Sources Pointings Total Time (ks) BH transient outbursts Yes Persistent BH No AGN No Msec pulsar outburst Yes NS transient bright outburst Yes Persistent bright NS No NS transient weak outburst Yes Persistent weak NS No Bursters Yes Total: 4 years with a goal of 5 years. Significant part (50%) available for observatory science

26 ACTIVITIES ESA is studying mission in house 2 parallel industrial studies started early in 2012 and ended this month Instrument consortium is working on payload: WFM: Hernanz (IEEC/CSIC) and Brandt (DTU) LAD: Zane/Walton/Kennedy (MSSL) Science case Coordinated by Stella (INAF), vd Klis (UvA) and Jonker (SRON) Yellow book for ESA down selection: Nov 2013 Selection of M3 mission beginning 2014 In the UK: - MSSL/UCL is leading the LAD payload UKSA supporting - Leicester SRC (G. Fraser) leading the collimator study - Southampton, Durham, Manchester, Cambridge on the science working groups

27 Yellow Book Outline (to be delivered Mid Nov)

28 LOFT Large Area Detector Item Requirement Goal Anticipated performance Effective area* Calibration area Energy range accuracy Energy resolution (FWHM, end of life) Energy Resolution (degraded performance outside field of regard**) 3.8 m 2 kev 7.6 m 5 kev 9.5 m 8 kev 0.95 m 30 kev 4.2 m 2 kev 8.4 m 5 kev 10.5 m 8 kev 1.05 m 30 kev 15% 10% 10% 2 30keV primary kev extended (for monitoring events ouside the LAD FoV) kev kev (singles, 40%) 3.56 m 2, 4 m 2.2 kev 9.5 m m m kev 1.5 (7.5 σ) lower threshold, 100 kev for maximum energy kev kev (singles, 40%) 260 ev 200 ev (singles) kev kev 400 6keV knowledge energy scale Collimated FoV (FWHM) degree degree (***) Off axis response (45 ) 30 kev Response stability (frequency-dependent, see relevant Tech Note) <0.01 Hz: <2% per decade Hz: <0.2% per decade Hz: <0.02% per octave >2000 Hz: Lower is better Hz: <0.0002% nearly periodic 1% per decade 0.05% per decade 0.005% per octave Lower is better < % nearly periodic Time resolution 10 µs 7 µs 7 µs Absolute time accuracy 2 µs 1 µs 1 µs 1.0 Responsibility of the spacecraft Dead time < 1 Crab, < 1 Crab, 1 Crab Dead time knowledge XX Less than the statistical precision of power spectrum for 1 day at 15 Crab up to F Ny = 10 khz (see [AD19]) Background < 10 mcrab < 5 mcrab 9 mcrab 2-30 kev Background knowledge 0.25% at 5-10 kev <0.20% at 5-10 kev (AGN reverberation mapping studies) Max flux (continuous, rebinned in energy >30 kev) Max flux (continuous, rebinned) On boad memory (transmitted over more orbits) Redundancy 0.3% at 5-10 kev > 500 mcrab >750 mcrab 650 mcrab 15 Crab 30 Crab 15 Crab, 300 minutes (full event information) Loss of<25% of the area due to single no single point failure 30 Crab, 300 minutes (full event information) <10% 17% instrument size SDD and orbit Collimator, alignment TM rates

29 LOFT Wide Field Monitor Camera dimensions FoV, camera location Detector, coded mask Ground contacts

30 The Mission I tem Requirem ent goal Net observing time core science 21 Msec Additional open observing time observatory science 33 Msec 20 Msec 30 Msec Calibration time 5% 2% minimum science observing times (during night time) Accessible sky fraction (daytime) 1 minute (1 source during 2 weeks per year) 10 minutes (10 sources during 2 weeks per year) >50 % 75% Mission duration 4 year 5 year Pointing accuracy (satellite + instruments combined) Relative pointing error (RPE over observation) Pointing knowledge for each axis over the full orbit (AMA, 3σ, 10 Hz) ToO (following alert of SOC) Orbit 1 arcmin 0.5 arcmin 1 arcmin 0.5 arcmin <20 arcsec <5 arcsec 24 hours for 70% of the time < 8 hours for 33% of the time + 24 hours for 66% of the time LEO, <600 km, < 5 deg LEO, 550 km, <2 deg Slews per orbit (average) Instrument data rate (typical) 1) LAD: 200 kbps (~ 150 mcrab) + Instrument data rate (sustained) WFM: 100 kbps LAD: 600 kbps (~ 500 mcrab) + WFM 100 kbps 1) WFM in event mode LAD: ~1 Crab data transfer per orbit 6.5 Gbit/orbit 14 Gbit/orbit Sun constraints consumables ToO response time

31 LOFT is a simple mission, relying on solid hardware heritage, offering both breakthrough and observatory science. LOFT is one of the 5 missions considered by the ESA WGs and SSAC as a candidate CV-M3