R. Hudec, F. Munz, J. Š trobl , P. Kubánek , P. Sobotka, R. Urban

1. Identification of INTEGRAL Sources with Astronomical Archival Plates(and by CCD imaging) R. Hudec, F. Munz, J. Štrobl, P. Kubánek, P. Sobotka, R. Urban Astronomical Institute, Academy of Sciences 251 65 Ondrejov, Czech Republic & ISDC, Versoix, Switzerland IBWS Oct 25-28, 2006 v

2. Identification of Sources • Only a fraction of 209 sources seen by INTEGRAL are either known sources or have been identified and classified already. • From the 56 newly by INTEGRAL detected sources (IGR sources), only ~ 20% have already firm classification, mostly with Cataclysmic variables (CVs), AGN, High Mass X-ray Binaries, Low Mass X-ray Binaries, Black Hole Candidates, and Anomalous X-ray Pulsars (Bird et al. 2006). • One of the methods applied in the past is the identification by optical spectroscopy, which proved recently some new and interesting identification of INTEGRAL gamma-ray sources such as newly detected symbiotic and cataclysmic variables (e.g. Masetti et al., 2005a, 2005, Wheatley et al., 2005).

3. Limitations of Recent Method Although successful, this method has some limitations. • it can be hardly applied for particular types of transients and recurrent transients. • it requires access to dedicated large aperture telescopes and spectrographs. • it can be laborious in the case of large error box and crowded field. • in some specific cases, only the spectral information alone is not enough for reliable classification of the objects.

4. The alternative method • We propose an alternative method how to identify the still non-classified INTEGRAL gamma ray sources and newly detected INTEGRAL sources in the future (and of other high energy satellites). • This method is based on the fact that (1) many of gamma-ray sources identified and classified so far do have optical counterparts, in many cases brighter than mag 18, (2) a significant fraction of these sources is variable both in gamma-rays as well as in optical wavelengths, and (3) they are in the fields densely covered by archival optical observations covering typically years to tens of years. • The results can be used also to confirm the classification proposed by spectroscopy and to provide additional details for better physical understanding of the sources.

5. Optical B and V magnitudes of optically identified INTEGRAL gamma-ray sources … most are brighter than mag 20, and more than half are brighter than mag 15

6. It is not very clear at the moment whether the fact that most of the identified sources are brighter than mag 15-20 is due to the fact that: • The non-identified sources are optically fainter than mag 20 • or • They are brighter than mag 20 but remain non-identified because of lack of observational data/identification efforts. The recent identifications of CVs and SSs by Masetti et al., 2005, 2006, indicate that at least for some fraction of the sources this is may be true. • Surely, the selection effect plays a role since so far, the mean-class telescopes have been used to identify the sources

7. Archival sky patrol plates There are more than 3 millions archival plates in the world, lim mag up to 23, > 5 x 5 deg in most cases Suitable for dense long-term photometry (up to 100 years, up to 2000 points, up to 23 mag) Suitable to detect rare events - years od CONTINUOUS monitoring easily possible Use of scanners, powerful computers and innovative software allows the effective data extraction and evaluation for the first time

8. Various types of astronomical plates (digitised) automated analyses with novel algorithms - task mainly for informatics students Multiple exposure Spectral image Direct Image

9. Suitable Databases for INTEGRAL • The Sonneberg Field Patrol and Leiden/Johannesburg Franklin Adams Plates represent suitable database for identification and analysis of INTEGRAL sources • They both provide numerous data for regions along the Galactic Plane and in the Galactic center

10. Sonneberg Field patrol • Northern regions along the Galactic Plane (but also other fields) covered by numerous (typically 50…500) astrograph plates. Typical Field of View (FOV) is 10 x 10 deg and the typical limiting magnitude is B 17. • In exceptional cases, also low-dispersion spectral plates are available

11. Leiden/Johannesburg Franklin Adams Plates • These plates were taken in Johannesburg by the high quality Franklin Adams refractor (Taylor, 1904) in years 1923-1952 within the project originated by Prof. E. Hertzsprung and are located in Leiden. • The plates cover selected fields along the southern Galactic plane as well as the Galactic centre. • The typical number of plates per field is 300…400, FOV is 10 x 10 deg and limiting magnitude 17.

12. UKSTU Plates (ROE, UK) The deepest astronomical plates in the world • faint limits, mag 19 - 23 • FOV 40 sq. degrees • various colors/filters • spectral plates down to mag 18 • 18 000 plates over 30 years • Unfortunately end of operation in 2001

13. Digitized Schmidt plate, TLS Tautenburg, lim mag 20, field M92. Newly detected variable objects with light amplitude > 2 mag are indicated. Example of the use of the powerful computer and novel dedicated software on digitised plates.

14. Analogous study can be also performed by CCD imaging & monitoring. On CCD images separated in time by weeks to years, the variable objects can be easily found. This is suitable for searches for objects with variability scales less than one year We have started to monitor the IGR positions by robotic telescopes and, more recently, by a 60 cm CCD telescope at the Brno Observatory

15. Monitoring of IGR sources by robotic CCD telescopes BART and WATCHER

16. The proposed analysis • Using the datamentioned here, the optically identified INTEGRAL sources with objects brighter than ~ mag 17 can be investigated for long-term changes covering 10 … 50 years. • In addition, these data can be used to search for new optical identifications of non-classified INTEGRAL sources on hand of their optical variability. This has been used already succesfully for ROSAT (Greiner and Richter,2006)

17. Distribution of Sonneberg Field Patrol Fields and Franklin Adams Fields (blue) in Galactic coordinates.The densely covered fields are darker.

18. The coverage of INTEGRAL IBIS for revolutions 1 - 430.

19. Additional prospects • analyzing the light curves for flares and flaring activity like these seen in V1223 Sgr and TV Col • trying to fit the flare profiles • trying to look for possible periodicities and recurrence • study of colors and color changes with time, with consequent physical discussions and interpretations. • correlations with other objects, with related conclusions toward physical processes and physical models.

20. Optical analyses of INTEGRAL gamma ray sources • Promising task for our group, taking into account our facilities and our experience • Also for other HE satellites and observing campaigns • Examples: LSI 61 303 mag 10, optical counterparts of fast X-ray transients-massive stars, INTEGRAL CVs and symbiotics, etc.

21. TV Col is an intermediate polar (IP) and the optical counterpart of the X-ray source 2A0526-328 (Cooke et al. 1978, Charles et al. 1979). This is the first cataclysmic variable (CV) discovered through its X-ray emission. TV Col displays three types of variation in the optical: (a) basic 0.2163 d photometric variation with an amplitude of ~0.27 mag (Motch 1981). (b) spectroscopic period of 0.22868 d (Hutchings et al. 1981). (c) beat period of 4.024 d between the photometric and spectroscopic period (Motch 1981). (d) flickering (~0.1 mag) on the time scale of minutes or dozens of minutes (Motch 1981). (e) brief outbursts lasting for ~hours with an amplitude of ~2 mag (Szkody and Mateo 1984).

22. Photographic light curve of TV Col including segments densely covered by the observations. The detected outbursts are marked by the vertical lines. The data are connected by the line in the densely covered intervals for convenience. The photographic magnitudes were calibrated to the B magnitudes. The empty triangles denote the upper limits of brightness.

23. Outbursts of TV Col: Date JD Max. (mag) Duration Source 2434420.348 B=12.60 <1 day Hudec et al. 2005 2434475.265 B=13.29? < 1 dayHudec et al. 2005 2439031.625 B=13.38 < 1 dayHudec et al. 2005 2439059.510 B=12.33 < 1dayHudec et al. 2005 2440572.398 B=12.25 <1 dayHudec et al. 2005 2444295.819 V~12.3 ~3 hr, ~1 d* Szkody and Mateo (1984) 2446125.73 V~11.9 ~4.5 hr Schwarz and Heemskerk (1987) 2446133.50 V~12 ~6 hr Schwarz and Heemskerk (1987) 2447122.6 DB~1.2 ~6 hr Augustein et al. (1994) 2447125.7 DB~1.8 ~6 hr Augustein et al. (1994) 2447133.6 DB~1.8 ~8 hr Augustein et al. (1994) 2448600.375 V~12.4 ~6 hr, ~3d* Hellier and Buckley (1993) Note: * corresponds to the full decline of outburst.

24. Decay time scale of dwarf nova (DN) outbursts tD (in days/mag) versus the orbital period Porb. The solid line marks the fit to non-magnetic DN (empty circles) (Warner 1995). Intermediate polars are denoted by the solid circles. The upper and lower symbols for HT Cam mark the initial and final tD, respectively. The outburst data for IPs come from Hellier et al., (1997), Ishioka et al. (2002), Schwarz et al. (1988), Šimon (2000, 2002), van Amerongen and van Paradijs (1989), Warner (1995).

25. Conclusions • Alternative identification method based on high quality astronomical archival plates has been proposed • In addition, already identifies sources can be effectively monitored in optical light • Important also for searches for brightenings in IBIS data

26. The End