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Variations of the emission lines in the spectrum of the yellow symbiotic star AG Dra have been studied for over 14 years (1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011), using more than 500 spectra obtained on the 1.5-metre telescope at Tartu Observatory, Estonia. The time interval covered includes the major (cool) outburst of AG Dra that started in 2006. Main findings can be summarized as follows: (i) cool and hot outbursts of AG Dra can be distinguished from the variations of optical emission lines; (ii) the Raman scattered emission line of O vi at λ 6825 almost disappeared during the cool outburst; (iii) lower excitation emission lines did not change significantly during the cool outburst, but they vary in hot outbursts and also follow orbital motion; (iv) similarity of variations in AG Dra to those in the prototypical symbiotic star Z And allows to suggest that a "combination nova" model proposed for the latter object might also be responsible for the outburst behaviour of AG Dra.

Abstract. We have combined recent radial velocity measurements of Fekel et al. (2000) with previously studied older ones, to test for the continued presence of the second period, found by Gális et al. (1999), which could be due to pulsations of the cool component of the AG Dra binary system. Fekel's data, even taken by themselves, also marginally suggest the presence of variations near the previously found second period. The period is in any case clearly seen, when all radial velocity measurements are combined.

AG Dra is a well known bright symbiotic binary with a white dwarf and a pulsating red giant. The long-term photometry monitoring and a new behaviour of the system are presented. The detailed period analysis of photometry as well as spectroscopy was carried out. In the system of AG Dra, two periods of variability are detected. The longer one around 550 days is related to the orbital motion, and the shorter one around 355 days is interpreted as pulsations of the red giant in our older paper. In addition the active stages change distinctively, but the outbursts are repeated with the periods from 359 to 375 days.

We report on the results of INTEGRAL observations of the neutron star low mass X-ray binary SAX J1810.8-2609 during its latest active phase in August 2007. The current outburst is the first one since 1998 and the derived luminosity is 1.1 − 2.6 × 10 36 erg s −1 in the 20-100 keV energy range. This low outburst luminosity and the long-term time-average accretion rate of ∼ 5 × 10 −12 M ⊙ yr −1 suggest that SAX J1810.8-2609 is a faint soft X-ray transient. During the flux increase, spectra are consistent with a thermal Comptonization model with a temperature plasma of kT e ∼ 23-30 keV and an optical depth of τ ∼ 1.2-1.5, independent from luminosity of the system. This is a typical low hard spectral state for which the X-ray emission is attributed to the upscattering of soft seed photons by a hot, optically thin electron plasma. During the decay, spectra have a different shape, the high energy tail being compatible with a single power law. This confirm similar behavior observed by BeppoSAX during the previous outburst, with absence of visible cutoff in the hard X-ray spectrum. INTEGRAL/JEM-X instrument observed four X-ray bursts in Fall 2007. The first one has the highest peak flux (≈ 3.5 Crab in 3-25 keV) giving an upper limit to the distance of the source of about 5.7 kpc, for a L Edd ≈ 3.8 × 10 38 erg s −1 . The observed recurrence time of ∼1.2 days and the ratio of the total energy 1 INTEGRAL is an ESA project with instruments and science data center funded by ESA member states (especially the PI countries:

Symbiotic variable stars belong to an interesting class of interacting binary systems.Since the beginning of this century, the systematic search for these objects has begun, and such surveys have led to discoveries of many new objects and dozens of candidates in the Milky Way and the Local Group. As the latest catalogue of symbiotic binaries is almost two decades old, we decided to prepare a new, online database of the galactic and extragalactic symbiotic systems. These objects are also known for their X-ray emission. For the purpose of this work, we have prepared a census of symbiotic binaries and their properties based on observations obtained by X-ray satellites in the previous decades. As our review has shown, the X-ray emission seems to be a common feature of symbiotic systems, preferentially detected from nearby sources.

Symbiotic stars belong to a group of interacting binaries that display a wide variety of phenomena, including prominent outbursts connected with mass transfer, as well as stellar winds, jets, eclipses, or intrinsic variability of the components. Dozens of new symbiotic stars and candidates have been discovered in recent years. However, there are many objects which are still poorly studied. Some symbiotic candidates suspected in the literature have never been studied spectroscopically. In this contribution, we present the first results of the ongoing campaign focused on symbiotic candidates. In the first paper in the series, we study the nature of ten candidate classical symbiotic stars suspected based on their photometric behaviour, colours or abundance pattern. To confirm or reject the symbiotic nature of the studied candidates, we obtained new spectra and analysed them in detail together with available multi-frequency photometric and spectroscopic observations of the objects. Hen 3-860 and V2204 Oph are genuine symbiotic systems showing typical spectral features of burning symbiotic stars and outbursts in the last 100 years. The first object belongs to the uncommon group of eclipsing symbiotic stars. V1988 Sgr cannot be classified as a genuine burning symbiotic star, but the scenario of an accreting-only symbiotic system cannot be ruled out. Hen 4-204 might be a bona-fide symbiotic star due to its similarity with the known symbiotic binary BD Cam. Six other symbiotic candidates (V562 Lyr, IRAS 19050+0001, EC 19249-7343, V1017 Cyg, PN K1-6, V379 Peg) are either single dwarf or giant stars or non-symbiotic binaries.

Symbiotic variables belong to an interesting class of interacting binary stars. At the beginning of this century, a systematic search for these objects was begun and such surveys in the Milky Way and the Local Group have resulted in discoveries of many new symbiotics and dozens of candidates. Because the latest catalogue of symbiotic binaries has been outdated for almost two decades, we decided to prepare a new database of the Galactic and extra-Galactic symbiotic systems. We present it in this work. Our database is available online, allowing it to be up-to-date and available to the astronomical community at any time. The database also includes a web portal that allows easy data access without the necessity for any additional software or formatting of the data.