T. Tomov

T. Tomov
Nicolaus Copernicus University | umk · Centre for Astronomy

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181
Publications
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Publications

Publications (181)
Article
Context. EE Cep is one of few eclipsing binary systems with a dark, dusty disc around an invisible object similar to ε Aur. The system is characterised by grey and asymmetric eclipses every 5.6 yr that have significant variations in their photometric depth, ranging from ∼0 . m 5 to ∼2 . m 0. Aims. The main aim of the observational campaign of the E...
Preprint
Full-text available
Context. EE Cep is one of few eclipsing binary systems with a dark, dusty disk around an invisible object similar to {\epsilon} Aur. The system is characterized by grey and asymmetric eclipses every 5.6 yr, with a significant variation in their photometric depth, ranging from ~ 0 m .5 to ~ 2 m .0. Aims. The main aim of the observational campaign of...
Preprint
Here we analyze high-resolution spectra of the Nova V392 Per obtained during the 2018 outburst. The H$\alpha$ and H$\beta$ emission lines show a triple-peak structure with radial velocities of about -2000 km/s, -250 km/s and 1900 km/s respectively. The near infrared spectrum is dominated by the narrow and single-peaked Paschen lines of hydrogen and...
Article
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Results from regular monitoring of relativistic compact binaries like PSR 1913+16 are consistent with the dominant (quadrupole) order emission of gravitational waves (GWs). We show that observations associated with the binary black hole (BBH) central engine of blazar OJ 287 demand the inclusion of gravitational radiation reaction effects beyond the...
Article
Full-text available
Results from regular monitoring of relativistic compact binaries like PSR 1913+16 are consistent with the dominant (quadrupole) order emission of gravitational waves (GWs). We show that observations associated with the binary black hole central engine of blazar OJ 287 demand the inclusion of gravitational radiation reaction effects beyond the quadr...
Article
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We present the first spectroscopic study of an eclipsing system GT UMa. Our spectra show that the main visual component A is a triple-lined star, which consists of a close eclipsing pair and a farther third component. Radial velocity measurements show evidence of reflex motion. We used Hipparcos and our own R-band light curves for the analysis. The...
Article
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Time-series photometry from space in the ultraviolet can be presently done with only a few platforms, none of which is able to provide wide-field long-term high-cadence photometry. We present a concept of UVSat, a twin space telescope which will be capable to perform this kind of photometry, filling an observational niche. The satellite will host t...
Article
We report finding high-velocity components in the H{\alpha} emission wings of St 2-22 spectra, obtained in 2005. This discovery have encouraged us to start the present study, aiming to show that this little studied object is a jet producing symbiotic system. We used high-resolution optical and low-resolution near infrared spectra, as well as availa...
Article
We report optical CCD photometry of the recently identified symbiotic star EF Aql. Our observations in Johnson V and B bands clearly show the presence of stochastic light variations with an amplitude of about 0.2 mag on a time scale of minutes. The observations point toward a white dwarf (WD) as the hot component in the system. It is the 11-th obje...
Article
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We analyse the light curve in the R band of the blazar OJ287, gathered during the 2015/2016 observing season. We did a search for quasi-periodic oscillations (QPOs) using several methods over a wide range of timescales. No statistically significant periods were found in the high-frequency domain both in the ground-based data and in Kepler observati...
Article
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Partida de Maitino, pol. 2 num. 163 (03206) Elche, Abstract: We analyse the light curve in the R-band gathered during the 2015/16 observing season of OJ287. We did a search for QPOs using several methods in wide time domain. No statistically significant periods were found in the high frequency domain both in the ground data and also in K2 observati...
Article
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OJ 287 is a quasi-periodic quasar with roughly 12 year optical cycles. It displays prominent outbursts that are predictable in a binary black hole model. The model predicted a major optical outburst in 2015 December. We found that the outburst did occur within the expected time range, peaking on 2015 December 5 at magnitude 12.9 in the optical R-ba...
Article
We analyse optical photometric data of short term variability (flickering) of accreting white dwarfs in cataclysmic variables (KR Aur, MV Lyr, V794 Aql, TT Ari, V425 Cas), recurrent novae (RS Oph and T CrB) and jet-ejecting symbiotic stars (CH Cyg and MWC 560). We find that the amplitude–flux relationship is visible over four orders of magnitude, i...
Article
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M31N 2015-01a (or M31LRN 2015) is a red nova that erupted in January 2015 -- the first event of this kind observed in M31 since 1988. Very few similar events have been confirmed as of 2015. Most of them are considered to be products of stellar mergers. Results of an extensive optical monitoring of the transient in the period January-March 2015 are...
Article
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We report on recent optical observations of the stellar and the nebular remnants of 22 southern post-novae. In this study, for each of our targets, we obtained and analysed long-slit spectra in the spectral range 3500-6600 A and in H$\alpha$+NII narrow-band images. The changes in the emission lines' equivalent widths with the time since the outburs...
Article
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We present results from the first attempts to derive various physical characteristics of the dusty Wolf–Rayet (WR) star WR 48a based on a multiwavelength view of its observational properties. This is done on the basis of new optical and near-infrared spectral observations and on data from various archives in the optical, radio and X-rays. The optic...
Article
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Asteroid spectroscopy reflects surface mineralogy. There are few thousand asteroids whose surfaces have been observed spectrally. Determining the surface properties of those objects is important for many practical and scientific applications, such as for example developing impact deflection strategies or studying history and evolution of the Solar...
Article
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EE Cep is a unique system in which a Be star is eclipsed by a dark dusty disk, making this star similar to the famous epsilon Aur in many respects. The depth and the duration of the EE Cep eclipses change to a large extent. The last two eclipses were observed in the framework of extensive international campaigns. The joint analysis of these campaig...
Article
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We present optical photometric monitoring of KT Eri (Nova Eridani 2009), a He/N very fast nova which oubursted in November 2009. Our observations include BVRcIc brightness estimations as well as monitoring of the rapid brightness variations in V band. The characteristic times of these rapid changes are studied and compared with the observed in othe...
Article
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We report photometric observations of GQ Mus performed between 1992 and 2011. We find that the total amplitude of the orbital modulation of its brightness decreased from ~0.9 mag in 1992 to ~0.2 mag in 2010, becoming comparable to the amplitude of chaotic flickering on a time scale of several minutes. Optical spectra obtained in 2001 and 2012 indic...
Article
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During the commissioning of the new echelle spectrograph attached to the 2m RCC telescope of NAO Rozhen (Bulgaria) we obtained a high-resolution spectrum of SN2014J on January 23.75UT. The spectrum covers the range 3900-9200A with a resolving power ~30000. The most prominent feature in our spectrum is the SiII 6355A absorption with an EW ~120A and...
Article
Epsilon Aurigae is a bright binary system, in which an F0 supergiant is eclipsed by a dark disk around the companion, every 27.1 years. Although the star has been observed and studied for nearly two centuries, it remains an usolved mystery. For the latest \varepsilon Aur eclipse, which occurred in 2009-2011, an international observing campaign was...
Article
We present Johnson's V- and I-band photometry obtained for V383 Sco long period eclipsing binary by the ASAS-3 photometric survey during the years 2001-2009 (4 data files).
Article
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V383Sco was discovered to be an eclipsing binary at the beginning of the XX century. This system has one of the longest orbital periods known (13.5yr) and was initially classified as a zet_Aur-type variable. It was then forgotten for decades. This study provides a detailed look at the V383Sco, using new data obtained around the last eclipse in 2007...
Article
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AZ Cas is a unique long period eclipsing binary (P_orb approx. 9.3 yr). It shows long eclipses lasting for more than 4 months which are very deep in the blue wavebands. The spatial configuration of highly eccentric orbit, the huge diameter of the supergiant and its extended envelope causes that the eclipses occurring close to the periastron passage...
Article
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We report on the discovery of TYC 4031-791-1 as an eclipsing binary of Algol type which shows primary and secondary eclipses with period P_orb approx. 6.68 days. The system is composed of two, perhaps similar stars of spectral type around B5 on slightly eccentric orbit.
Article
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Two observational campaigns were carried out during the eclipses of EE Cep in 2003 and 2008/9 to verify whether the eclipsing body in the system is indeed a dark disk and to understand the observed changes in the depth and durations of the eclipses. Multicolour photometric data and spectroscopic observations at both low and high resolution were col...
Article
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An overview of our ongoing photometric and spectroscopic monitoring of the \varepsilon Aurigae eclipse in 2009-2011 is presented. The obtained until now observational data is described and discussed. The changes in the spectrum, which can be attributed to the eclipsing disk, are illustrated with the variations in the profiles and the equivalent wid...
Article
A summary of our efforts to study in more details one of the longest period eclipsing binaries V383 Sco is presented. Historical photometric observations as well as recent photometry and spectroscopy are used. Our results suggest that V383 Sco could be a high-velocity bulge/bar system containing a post-AGB supergiant eclipsed by a pulsating M super...
Article
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We present the Young Exoplanet Transit Initiative (YETI), in which we use several 0.2 to 2.6m telescopes around the world to monitor continuously young (< 100 Myr), nearby (< 1 kpc) stellar clusters mainly to detect young transiting planets (and to study other variability phenomena on time-scales from minutes to years). The telescope network enable...
Article
This data set consists of three spectra of V838 Mon obtained with UVES at VLT on 2 Jan., 13 Feb., and 22 March 2009. The spectra were acquired in the UVES standard red arm 580 setting, which gives a spectral coverage of 4770-6825 Angstroms. The spectral resolution is around R=52,000. Spectra are NOT corrected for the interstellar extinction and the...
Article
Full-text available
Context. V838 Mon erupted at the beginning of 2002. In the course of the outburst the object evolved to low effective temperatures and declined as a very late M-type supergiant. Among various scenarios proposed to explain the nature of the outburst, the most promising is a stellar merger event. Aims. We aim at studying the structure and evolution...
Article
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The sudden lengthening of orbital period of VV Cep eclipsing binary by about 1% was observed in the last epoch. The mass transfer and/or mass loss are most possible explanations of this event. The photometric behaviour of AZ Cas, the cousin of VV Cep, suggests that the accretion can occur and could be important in this system, too.
Article
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In this papper we present the analyses of the six (1998, 1997, 2001, 2002, 2003 and 2005) last outbursts of AG Draconis on the basis of low resolution visual spectroscopy. A new method to determine the Zanstra's temperature of the hot ionizing source from the optical Hb and HeII emission lines has been used. As a results we obtained the evolution o...
Article
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We present an analysis of high resolution spectral observations of the symbiotic star StHa 190. A 30 days period has been derived from radial velocities of the G-type absorption lines and the HeII 4686A emission line. The main aim of this work was to look for explanation of the very wide absorption lines of the yellow giant. The very low mass funct...
Article
We analyze archival U-band high speed photometry of the jet-ejecting symbiotic binary MWC 560 obtained during 1990-1993. The analysis shows that variability on time scales <20 min (flickering) is missing when the mass outflow is in a regime of discrete ejections with ejection velocity V_{ej} up to 7000 kms (February 1990 - March 1991), and when the...
Article
We present very preliminary analysis of a large sample of southern symbiotic stars spectra based on a simple photoionization model. Balmer decrement diagram and the He II 4686 Å/Hβ flux ratio were used to derive basic parameters, such as reddening, optical depth in Hα and the temperature of the hot component for each system.
Article
Full-text available
The results of time-resolved observations of SU UMa and U Gem obtained over two-years are presented. Both stars are prototypes of different classes of dwarf novae. We studied brightness variations on different time scales: orbital, QPO and flickering. The multicolor BVRI photometry allows to distinguisch the geometrical and physical sources of thes...
Article
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Nova V2491 Cyg was discovered on April 10.72 UT 2008 (Nakano, 2008). Here we present spectrophotometric premises that V2491 Cyg can be a good candidate for recurrent nova (RNe). Its properties are compared to five well known RNe with red dwarf secondaries (U Sco, V394 Cra, T Pyx, CI Aql, IM Nor) and recently confirmed as recurrent nova V2487 Oph (P...
Article
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We present photometric and spectral observation for four novae: V2362 Cyg, V2467 Cyg, V458 Vul, V2491 Cyg. All objects belongs to the "fast novae" class. For these stars we observed different departures from a typical behavior in the light curve and spectrum.
Article
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A new estimation of the orbital period of YY Her on the base of our and published observations is presented. Phased light curves in RI bands show evidently ellipsoidal effect connected with the tidal distortion of the giant surface. Comment: 2 pages, 1 figure, Conference Binaries - key to comprehention of the Universe, Brno, Czech Republik
Article
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We present UBVRI photometry of three symbiotic stars ZZ CMi, TX CVn and AG Peg carried out from 1997 to 2008 in Piwnice Observatory near Torun. To search orbital periods of these stars Fourier analysis was used. For two of them, TX CVn and AG Peg, we have confirmed the earlier known periods. For ZZ CMi we found a relatively short period 218.59 days...
Article
Full-text available
The photometric and spectroscopic observational campaign organized for the 2008/9 eclipse of EE Cep revealed features, which indicate that the eclipsing disk in the EE Cep system has a multi-ring structure. We suggest that the gaps in the disk can be related to the possible planet formation. Comment: 6 pages, 6 figures, contribution to the conferen...
Article
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We present the results of unfiltered and UBVR_cI_c band CCD photometry fast nova V2467Cyg. Our analysis of the data gives two distinct frequencies corresponding to periods of ~3.8h and ~35 min. The observed light curve of V2467 Cyg is typical for an intermediate polar. Comment: 4 pages, 5 figures
Article
We report on optical observations of Nova Eri 2009 obtained at the Nicolaus Copernicus University Observatory (Torun, Poland) and the Olsztyn Planetarium and Astronomical Observatory. Using a 60 cm Cassegrain telescope (Torun) and a 25 cm Schmidt-Cassegrain telescope (Olsztyn) we estimated the V brightness of the Nova to ~8.30+/-0.04 mag and ~8.59+...
Article
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The 2008/2009 eclipse of EE Cep is coming. Good quality photometric and spectroscopic data are needed to confirm, whether hot component in EE Cep system is eclipsed by an extended dark disc. An appeal to participate in observations of this eclipse is presented.
Article
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The nature of the high-velocity emission components observed in the Balmer line wings in the spectrum of RS Ophiuchi still remains unknown. Using high and medium resolution spectra acquired between 1994 and 2006 we tried to extract these components from the Hα profile and measured their radial velocities and equivalent widths. Here we discuss the l...
Article
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We have analysed high resolution spectra of RS Oph obtained in 2004 and 2005. In the analysis we have concentrated on the lines of ionized metals such as TiII and FeII. In the profiles of both species, emission and two absorption components are visible. Here we present the results of radial velocity measurements for FeII and discuss their behaviour...
Article
We present our multicolour photometric data of the primary and secondary eclipses of OW Gem that took place in 1995, 2002, and 2006, as well as the new radial-velocity data collected since 1993 by R. F. Griffin and A. Duquennoy. The Wilson-Devinney code was used for the simultaneous solution of both photometric and spectroscopic data. A complete se...
Article
We report on optical spectral observations and UBVRI brightness estimations obtained with 60/90 cm Schmidt and 60 cm Cassegrain telescopes of the Nicolaus Copernicus University Observatory (Torun, Poland). The nova V2491 Cyg was discovered on Apr. 10.728 UT with about 7.7 mag on unfiltered CCD frames (IAUC#8934). Additionally, the X-ray emission wa...
Article
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We present preliminary analysis of six high-resolution spectra of RS Oph obtained 1--2 years before the last outburst in 2006. New radial velocities of the M giant's neutral metal absorptions and double-component Ti II absorptions were measured and used here to study the orbital motions.
Article
Full-text available
UBVRI photometry observations of 10 symbiotic stars and related objects obtained in the period 2002-2003 are presented. Analysing differential light curves we found rapid light variations with timescales of tens of minutes and significant amplitudes in the well-known flickerers MWC 560, RS Oph, V407 Cyg and T CrB. MWC 560 and V407 Cyg demonstrate q...
Article
We report BV photometry and optical spectroscopic observations of a bright new variable in Cassiopeia, identified as GSC 3656-1328 (CBET # 711, # 712). According to SIMBAD database GSC 3656-1328 is a 11.4 star in V with B-V of about 0.2. Our spectra in the region 3700-7300AA and at a resolution of 4A were obtained with the 60/90cm Schmidt-Cassegrai...
Article
In our previous report (ATEL#931) we have suggested that the bright optical transient in Cassiopeia, identified as GSC 3656-1328, can be understood as a gravitational microlensing event of a nearby star (see also ATEL#942). All available photometric data support the finding and a symmetric microlens fit best reproduces the light curve. We continue...
Article
We report on optical spectral observations and V brightness estimate obtained with 60/90 cm Schmidt-Cassegrain telescope and the SAVS camera of the Nicolaus Copernicus University Observatory in Piwnice. The spectrum obtained on April 6.05 UT (3400-7050AA, resolution of 4A) shows numerous absorption lines (HI, FeII, CaII among the others) and in the...
Article
Full-text available
The orbits and physical parameters of three detached, double-lined A-F eclipsing binaries have been derived combining $H_{\rm P}, V_{\rm T}, B_{\rm T}$ photometry from the Hipparcos/Tycho mission with 8500-8750 Å ground-based spectroscopy, mimicking the photometric+spectroscopic observations that should be obtained by GAIA, the approved Cornerstone...
Chapter
We report multicolour photometric observations of the 2003 eclipse of the long-period (5.6 yr) eclipsing binary EE Cep. Measurements were obtained with ten telescopes at eight observatories in four countries. In most cases, UBV (RI)C broad band filters have been used. The light curve shape shows that the obscuring body is an almost dark disk around...
Article
Full-text available
High-resolution spectroscopy during the eclipse of EE Cep was obtained and presented for the first time. The star’s spectroscopic behaviour can be roughly interpreted as a partial eclipse of the high luminosity Be primary and its emitting gaseous ring by the semi-transparent gaseous envelope around an invisible, opaque secondary, most probably a da...
Article
Full-text available
Extensive optical and infrared photometry as well as low and high resolution spectroscopy are used as inputs in deriving robust estimates of the reddening, distance and nature of the progenitor of V838 Mon. The reddening is found to obey the R_V=3.1 law and amounts to (i) E(B-V)=0.86 from the interstellar NaI and KI lines, (ii) E(B-V)=0.88 from the...
Article
The orbits and physical parameters of three detached, double-lined A-F eclipsing binaries have been derived combining HP,VT,BT photometry from the Hip- parcos/Tycho mission with 8500-8750 ûA ground-based spectroscopy, mimicking the photometric+spectroscopic observations that should be obtained by GAIA, the ap- proved Cornerstone 6 mission by ESA. T...
Article
Extensive optical and infrared photometry as well as low and high resolution spectroscopy are used as inputs in deriving robust estimates of the reddening, distance and nature of the progenitor of V838 Mon, the 2002 outbursting event that produced a most spectacular light-echo. (3 data files).
Chapter
High-resolution spectroscopy during the eclipse of EE Cep was obtained and presented for the first time. The star’s spectroscopic behaviour can be roughly interpreted as a partial eclipse of the high luminosity Be primary and its emitting gaseous ring by the semi-transparent gaseous envelope around an invisible, opaque secondary, most probably a da...
Article
Full-text available
Some aspects of the recent activity period of the peculiar symbiotic binary CH Cyg, which has ejected both bipolar jets and discrete centrifugal outflows, are discussed.
Article
IAUC 8256 available at Central Bureau for Astronomical Telegrams.
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IAUC 8253 available at Central Bureau for Astronomical Telegrams.