The progress of Low-Mass X-ray binary monitoring program

1. The progress of Low-Mass X-ray binary monitoring program 陳炳志 許瑞榮 蘇漢宗 成功大學物理系 天文實驗室 周翊 黃崇源 中央大學天文所

2. Outlines • Scientific motivation • The collaboration with Yale • 2002 Summer visiting and 4U1543-47 • Current status at NCKU • Monitoring targets and observation • Data archive • Data reduction and automatic photometry pipeline • Web-based photometry database • Preliminary result — V616 Mon and GRO J0422+32 • On-going work and perspectives 2003年物理年會

3. Scientific motivation • Sometimes, an X-ray binary star could be ignited dramatically by 8-magnitude which we call “outburst” →Target of opportunity(TOO). • Some outbursts will occur repeatedly but almost irregularly, and they were referred as recursive novae. • In the outburst state, multi-wavelength light curves are excellent probes to explore the structure of the accretion disk and mass transfer between components. 2003年物理年會

4. Scientific motivation • The luminosity can reach a maximum in few days, but declines gradually to quiescence state in few weeks or few months. →It’s essential to have observation facility to response to the outburst alert and to perform follow-up. • Some outbursts occur repeatedly but irregularly.→ Need to monitor these known X-ray binaries continuously and globally. 2003年物理年會

5. 2002 Summer Visiting • Go through real observation data before LOT routine operation • Discuss the scientific strategy and collaboration platform on this 2-sites monitoring work • Major work: 2002 outburst of 4U1543-47 (observed by MSO 74in reflector which was burned on a wildfire of Jan. 19 2003!) 2003年物理年會

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8. Targets to be monitored 2003年物理年會

9. Observation at LOT • Observed targets • V616 Mon: 12 nights (11/26, 12/1-12/6, 12/13-12/14, 1/1, 1/23, 1/25) • XTE J1118+480: 10 nights (12/1-12/3, 1/24, 1/29-1/31, 2/6, 2/9, 2/10) • 4U2129+47: 1 night (11/09) • GRO J0422+32: 2 night (11/26, 1/25), 1/25: Fast photometry 2003年物理年會

10. Data Archive • Transfer data to download area by ftp in next morning (30~40KB/s). • Copy to archive area and carry out bias/dark/flat calibration, remove matterless files. • Backup to DVD-R when download area occupation exceeds 4.5GB. Remove files after backup. • Copy into work area to reduce photometry. • Clean work area after photometry reduction. 2003年物理年會

11. Data Reduction • Archive area • Put "observatory", "RA", "DEC" tags into fits header. (hedit/cl) • Calculate "hour angle", "airmass", "mean sideral time", "julian day" and paste into fits header. (asthedit) • Do bias/dark/flat calibration on all files. (zerocomb/darkcomb/flatcomb/ccdproc) • Keep combined bias/dark/flat std. fields and LMXB observation, remove other files. 2003年物理年會

12. Data Reduction • Work area • Crowd field photometry (daophot→AUTOMATIC PIPELINE) • Match target and comparison/standard stars (photcal→IDL) • Photometry calibration and check (photcal→IDL) • Post calibrated photometry to web-based database 2003年物理年會

13. Automatic photometry pipeline • Only one parameter for this pipeline: an estimate of FWHM of the field stars • Major tasks: • Calculate the deviation of sky background by 3-σ rejection and iteration. • Find the coarse center of the stars (daofind task). • Carry out fast aperture photometry as as initial value in the following calculation (phot task). • Sift bright stars with non-linear central profile, faint and non-stellar objects. • Select 35 bright candidates to construct an analytic PSF (pstselect and psf tasks). • Solve the magnitudes of the stars (allstar task). • Reject bright stars with non-linear central profile from solved objects list. • Select 25 bright candidates from solve objects list and construct an PSF (pstselect and psf tasks). • Solve the magnitudes of the stars as final results (allstar task). 2003年物理年會

14. Automatic photometry pipeline • Advantages of the pipeline: • Only one parameter: Other essential parameters can be estimated by pipeline itself. • Accurate photometry: less than 0.002 magnitude difference compared to the results reduced by manual operation and inspection. • Fast reduction: 1.5-2.0 minutes per frame, and the pipeline can be scripted in order to process numerous of images. 2003年物理年會

15. Web-based photometry database • Designed by PHP, MySQL, TCL • Data post • Web-based interactive input • Upload by predefined format text file • Output • Tabular photometry data • On-line light curve • A platform for site-to-site collaboration. 2003年物理年會

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21. Preliminary results — V616 Mon • V~18.2 in quiescent state. (R~17.27) • 3 minutes exposure, S/N >100 • Calibration • Done by 2002/12/14 observation • 6 Landolt fields and 36 Std. Stars • 7 nearby stars were calibrated in V616 Mon field • KR=0.097 2003年物理年會

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23. Preliminary results — V616 Mon • Photometry accuracy : 0.01 mag • ΔmV616 Mon ~ 0.2 • Δmcomp. star ≦ 0.02 2003年物理年會

24. Preliminary results — GRO J0422+32 fast photometry • Photometry accuracy : 0.01 mag • ΔmV616 Mon < 0.1 • Δmcomp. star ≦ 0.02 2003年物理年會

25. On-going works • Precise multi-band photometry calibration on XTE J1118+480, GRO J0422+32 and V616 Mon fields. • Fast photometry to detect orbital and other related periods and superhump phenomena. 2003年物理年會

26. Perspectives • The improvement on the observation • Resident observers? • Multi-band photometry → precise calibration • Header tags of "RA", "DEC" to help automatic calibration pipeline • Increase monitoring targets → 3~5/nights (1 hr/night) • Better automatic pipeline? • Auto download and bias/dark/flat correction? • Photometry calibration script 2003年物理年會