html5-img
1 / 10

X-ray Bursters with ESTREMO

X-ray Bursters with ESTREMO. Looking for burst lines: investigating the NS EOS Superbursts as peculiar thermonuclear flashes XrB population study (not a main driver) XrB spectroscopy (not a main driver). -> requirements for advanced XrB studies.

kin
Download Presentation

X-ray Bursters with ESTREMO

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. X-ray Bursters with ESTREMO • Looking for burst lines: investigating the NS EOS • Superbursts as peculiar thermonuclear flashes • XrB population study (not a main driver) • XrB spectroscopy (not a main driver) -> requirements for advanced XrB studies M. Cocchi, J.J.M. In ‘t Zand

  2. Cottam, Paerels & Mendez: absorption lines in the burst spectra of EXO 0748-676 (28 events average, XMM/RGS) M. Cocchi, J.J.M. In ‘t Zand

  3. Lines -> redshift -> determination of M/R ratio -> guess on the NS EOS Fe XXV, XXVI (n=2-3) and O VIII (n=1-2) with redshift z=0.35 -> in agreement with normal nuclear matter (some exotic models excluded) M = 1.4-1.8 Msun, R = 9-12 km Better / updated NS atmosphere models (taking into account also burst effects) are expected M. Cocchi, J.J.M. In ‘t Zand

  4. Looking for Bursts lines: 1) normal bursts: look at the longer bursts (eg GS 1826-238, KS 1731-2609, H 1608-52, 4U 1812-12 - the latter 2 being Eddington-limited bursters) GS1826-238 is the best candidate + easy trigger + most frequent bursts (1/3h) + pretty long events (~120 s) + GS 1826 shows quasi-periodic bursts (other pointings possible between consecutive events) - need for fast slew (<20 s not to miss the first phase) - need for low energy sensitivity in WFGC (~4 keV) M. Cocchi, J.J.M. In ‘t Zand

  5. Looking for Bursts lines: 2) superbursts: + very long bursts (hours, excellent statistics) + no real need for quick repointing (a few minutes is ok) + WFGC low energy threshold can be higher (5 keV) as more statistics available and integrating on larger timebins + less WFGC sensitivity needed - tricky trigger, possibly manual (high persistent intensity sources) - rare events (1-2 per year for 5-10% Edd sources) - LEO gaps interfering with the burst light curve and affecting count statistics M. Cocchi, J.J.M. In ‘t Zand

  6. Requirements on the WFGC low energy threshold for burst detection • For bursts with BB kT<2.5 keV, >99% of photon flux is below 20 keV • For kT>2.0 keV, you get >85% of photons with LET=2 keV, >50% for LET=5 keV and >10% for LET=10 keV (so going down to 2 keV from 5 keV leads to an improvement of 35% only) • For a 1 Crab (2-10 keV) 2.0 keV burst I5-20 keV = 0.9 c/s/cm2 • For a 1 Crab (2-10 keV) 2.5 keV burst I5-20 keV = 2.3 c/s/cm2 • In general, Aeff = 5 x sqrt(bkg) / sqrt(tri x delta-T) x I5-20 keV . • => For a 2.5 keV burst, Aeff=70 cm2; for tri=0.5 Aeff= 100 cm2 • Detect triggers  • monitor sensitivity should be able to detect 2 keV black body spectrum with bolometric flux of 10-8 erg s-1 cm-2 within 1 s, e.g. 100 cm2 at 40 x 40 sq deg • Have X-ray bursters in field of view, for instance through considerable exposure on Galactic center M. Cocchi, J.J.M. In ‘t Zand

  7. fallout science (depending on the pointing strategy): 1) XrB population study by WFGC: burst recurrence time vs bolometric luminosity, burning regimes big FOV, best sensitivity and energy response for a 40x40 ever. => Improving the nice results of BeppoSAX-WFC. Nothing like that since BeppoSAX! 2) Spectroscopy of bursters: refinement of spectral models (e.g. Compton tails & breaks, double Compton – see Thompson et al.) M. Cocchi, J.J.M. In ‘t Zand

  8. Burst Spectroscopy: 3 main spectral stases with INTEGRAL • Simple Comptonized emission fits quite well the 20-200 keV spectra of INTEGRAL bursters • Fitted electron kT’s range from ~3 to ~20 keV, possibly clustered in 2-3 ranges of values, likely related to the source state: • kTe ~ 3 keV, bursters in soft state, no evidence for hard tail, emission drops at < 50 keV (4U 1735-444, 4U 1820-303, possibly H 1702-429) • kTe ~ 6-10 keV, bursters in a sort of intermediate state, emergence of a hard Compton tail at 50-100 keV (GX 3+1, SLX 1744-300, GX 354-0, H 1705-440) • kTe > 15 keV, bursters in very hard state, Compton hard tail extended well above 100 keV, up to 200 keV (GS 1826-238, 4U 1812-12) M. Cocchi, J.J.M. In ‘t Zand

  9. kT = 28 ± 5 keV t = 1.1 ± 0.2 c2(dof) = 1.3 (17) f = 11.5 10-10 erg cm-2 s-1 kT = 12.1 ± 1.4 keV t = 4.6 ± 0.6 c2(dof) = 1.0 (21) f = 8.7 10-10 erg cm-2 s-1 kT = 3.0 ± 0.1 keV t = 17 ± 10 c2(dof) = 1.0 (18) f = 2.15 10-10 erg cm-2 s-1 M. Cocchi, J.J.M. In ‘t Zand

  10. What XrB community wants (requirements for ESTREMO): WFGC: -bandpass: Emin = 3-4 keV , ok if Emin < 5 keV Emax up to 200 keV for bolometric studies - spectral resolution 15-20% FWHM - detector area: a few hundred cm2 - timing: 1 ms - field of view: at least 40 deg fwzr (to trade off with the X-ray BGD) - source.location.accuracy. 1 arcmin - sensitivity: 500 mCrab in 1 s (normal burst trigger) much less for superbursts - slew speed: 1-2 deg/s, if combined with dedicated observation programs (e.g. Galactic Bulge) NF telescope: -bandpass: 0.3-10 keV - spectral resolution: 3 eV @ 1 keV, even less for fast rotators - area: as large as possible.. - timing 0.1 ms (ms oscillations in bursts) - maximum countrate: 10,000 (pile up?) - field of view: none - angular resolution: none M. Cocchi, J.J.M. In ‘t Zand

More Related