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1

Hot Spot in Eclipsing Dwarf Nova IY Ursae Majoris during Quiescence and Normal Outburst

Bąkowska K., Olech A.

Acta Astronomica

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2015

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Vol. 65, No. 4

351--360

EN

We present the analysis of hot spot brightness in light curves of the eclipsing dwarf nova IY UMa during its normal outburst in March 2013 and in quiescence in April 2012 and in October 2015. Examination of four reconstructed light curves of the hot spot eclipses showed directly that the brightness of the hot spot changed significantly only during the outburst. The brightness of the hot spot, before and after the outburst, was on the same level. Thus, based on the behavior of the hot spot, IY UMa during its normal outburst follows the disk-instability model.

2

Hot Spot Manifestation in Eclipsing Dwarf Nova HT Cassiopeiae

Bąkowska K., Olech A.

Acta Astronomica

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2014

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Vol. 64, No. 3

247--259

EN

We report the detection of a hot spot in the light curves of the eclipsing dwarf nova HT Cas during its superoutburst in 2010 November. Analysis of the eight reconstructed light curves of the hot spot eclipses showed directly that the brightness of the hot spot was changing significantly during the superoutburst. Thereby, detected hot spot manifestation in HT Cas is the newest observational evidence for the EMT model for dwarf novae.

3

CzeV404 - an Eclipsing Dwarf Nova in the Period Gap During its July 2014 Superoutburst

Bąkowska K., Olech A., Pospieszyński R., Martinelli F., Marciniak A.

Acta Astronomica

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2014

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Vol. 64, No. 4

337--348

EN

Results of the CCD observations of CzeV404 are presented. During the season of June-August 2014 we detected one outburst and one superoutburst of the star. Clear superhumps with the period of Psh=0.10472(2) days were observed. The superhump period was decreasing with a high value of dP/dt=-2.43(8)×10-4. From 17 eclipses we calculated the orbital period with the value of Porb=0.0980203(6) days which confirms that CzeV404 belongs to period gap objects and it is the longest orbital period of an eclipsing SU UMa star. Based on superhump and orbital period determinations, the period excess ε=6.8%±0.02% and the mass ratio q≈0.32; of the system were obtained.

4

Photometric Study of the Star Cluster NGC 2155 in the Large Magellanic Cloud: Age Estimation and Variable Stars

Otulakowska M., Olech A., Pych W., Pamyatnykh A. A., Zdravkov T., Rucinski S. M.

Acta Astronomica

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2011

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Vol. 61, No. 2

161--177

EN

We present results of new photometry for the globular star cluster NGC 2155 in the Large Magellanic Cloud (LMC). Our I- and V-band observations were obtained with the 6.5-m Magellan-1 Baade Telescope at Las Campanas Observatory resulting in deep photometry down to V≈24 mag. By analyzing the color-magnitude diagram for the cluster and utilizing the Victoria-Regina grid of isochrones models we estimated the age of the cluster at ≅2.25 Gyr and [Fe/H]=-0.71, the numbers which place NGC 2155 outside the age-gap in the age-metallicity relation for LMC clusters. Using the Difference Image Analysis Package (DIAPL), we detected 7 variable stars in the cluster field with variability at the level of 0.01 mag in the I-band. Three variable stars are particularly interesting: two SX Phe stars pulsating in the fundamental mode, and a detached eclipsing binary which is a prime candidate to estimate the distance to the cluster.

5

Dwarf Nova V1040 Centauri and Variable Stars in its Vicinity

Rutkowski A., Pietrukowicz P., Olech A., Ak T., Złoczewski K., Poleski R., Tappert C., Eker Z.

Acta Astronomica

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2011

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Vol. 61, No. 4

345--357

EN

We present the results of a photometric campaign of the dwarf nova V1040 Cen. The light curve shows two normal outbursts with recurrence time ≈40 days and amplitude ≈2.5 mag. Quiescence data show oscillations with periods in the range ≈0.1 days (2.4 h) to ≈0.5 days (12 h) of unknown origin. We measured the orbital period of V1040 Cen to be Porb=0.060458(80) days (1.451±0.002 h). Based on the MV-Porb relation we found the distance of V1040 Cen to be 137±31 pc. In this paper we also report the detection of eleven new variable stars in the field of the monitored dwarf nova.

6

The 2003 and 2005 Superhumps in V1113 Cygni

Bąkowska K., Olech A., Złoczewski K., Wiśniewski M.

Acta Astronomica

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2010

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Vol. 60, No. 2

137--147

EN

We report CCD photometry of the cataclysmic variable star V1113 Cyg. During two campaigns, lasting from May to August 2003 and from March to June 2005, we recorded two superoutbursts. In the obtained light curves we detected clear superhumps with a mean period Psh=0.07891(3) days (113.63±0.04 min). That fact confirms that the star is a member of SU UMa class of dwarf novae. During the first observed superoutburst the superhump period was decreasing with an enormous rate of P=-4.5(8)×10-4 which is one of the highest values ever observed in SU UMa systems.

7

2009 Superoutburst of Dwarf Nova 1RXS J053234.9+624755

Rutkowski A., Olech A., Poleski R., Sobolewska M., Kankiewicz P., Ak T., Boyd D.

Acta Astronomica

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2010

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Vol. 60, No. 4

337--355

EN

We present photometric observations of the dwarf nova 1RXS J053234.9+624755. We performed a detailed analysis of the superoutburst that occurred in August 2009. We found the superhump period to be Psh=0.057122(14) days. Based on the O-C diagram we conclude that Psh increased during the plateau at the rate of dPsh/dt=(9.24±1.4)×10-5. Both the O-C analysis and evolution of the superhumps light curve favor the model in which superhumps originate in a variable source located in the vicinity of the hot spot. In addition, the evolution of the light curve suggests that the superhump light source approaches the disk plane as the superoutburst declines. Detailed analysis of the superoutburst plateau phase enabled us to detect a signal which we interpret as apsidal motion of the accretion disk. We detected additional modulations during the final stage of the superoutburst characterized by periods of 104 s and 188 s which we tentatively interpret as quasi periodic oscillations. Estimations of A0 and An are in agreement with the dependence between the amplitude of superhumps and the orbital inclination.

8

CURiuos Variables Experiment (CURVE): Variable Stars in the Metal-Poor Globular Cluster M56

Pietrukowicz P., Olech A., Kędzierski P., Złoczewski K., Wiśniewski M., Mularczyk K.

Acta Astronomica

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2008

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Vol. 58, No. 2

121--130

EN

We surveyed a 6.5'×6.5' field centered on the globular cluster M56 (NGC 6779) in a search for variable stars detecting seven variables, among which two objects are new identifications. One of the new variables is an RRLyrae star, the third star of that type in M56. Comparison of the new observations and old photometric data for an RV Tauri variable V6 indicates a likely period change in the star. Its slow and negative rate of -0.005±0.003 d/yr would disagree with post-AGB evolution, however this could be a result of blue-loop evolution and/or random fluctuations of the period.

9

Curious Variables Experiment (CURVE). RZ LMi - the Most Active SU UMa Star

Olech A., Wiśniewski M., Złoczewski K., Cook L. M., Mularczyk K., Kędzierski P.

Acta Astronomica

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2008

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Vol. 58, No. 2

131--152

EN

We report extensive photometry of the frequently outbursting dwarf nova RZ Leo Minoris. During two seasons of observations we detected 12 superoutbursts and 7 normal outbursts. The V magnitude of the star varied in range from 16.5 mag to 13.9 mag. The superoutbursts occur quite regularly flashing every 19.07(4) days and lasting slightly over 10 days. The average interval between two successive normal outbursts is 4.027(3) days. The mean superhump period observed during the superoutbursts is Psh=0.059396(4) days (85.530±0.006 min). The period of the superhumps was constant except for one superoutburst when it increased with a rate of P/Psh=7.6(1.9)×10-5. Our observations indicate that RZ LMi enters the stage of permanent superhumps, both in superoutbursts and quiescence. This may indicate that decoupling of thermal and tidal instabilities play important role in ER UMa systems. No periodic light variations which can be connected with orbital period of the binary were seen, thus the mass ratio and evolutionary status of RZ LMi are still unknown.

10

Curious Variables Experiment (CURVE). Three Periodicities of BF Ara

Olech A., Rutkowski A., Schwarzenberg-Czerny A.

Acta Astronomica

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2007

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Vol. 57, No. 4

331--345

EN

We report CCD photometry of the dwarf nova BF Ara in quiescence carried out throughout fifteen consecutive nights. Light curve in this interval is dominated by a large amplitude (≈0.8 mag), two period modulations. Higher amplitude signal has a period of 0.082159(4) days, which was increasing at the rate of P/Psh=3.8(3)×10-5. Weaker and stable second signal has a period of 0.084176(21) days. Because the superhump period of BF Ara is equal to 0.08797(1) days, the first modulation is interpreted as quiescent negative superhump arising from retrograde precession of titled accretion disk and the latter one as the orbital period of the binary. The respective period excess and defect are ε=4.51%±0.03% and ε-=-2.44%±0.02%. Thus BF Ara is yet another in-the-gap nova with mass ratio of q≈0.21.

11

Curious Variables Experiment (CURVE). CCD Photometry of V419 Lyr in its 2006 July Superoutburst

Rutkowski A., Olech A., Mularczyk K., Boyd D., Koff R., Wiśniewski M.

Acta Astronomica

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2007

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Vol. 57, No. 3

267--279

EN

We report extensive photometry of the dwarf nova V419 Lyr throughout its 2006 July superoutburst till quiescence. The superoutburst with amplitude of ≈3.5 mag lasted at least 15 days and was characterized by the presence of clear superhumps with a mean period of Psh=0.089985(58) days (129.58±0.08 min). According to the Stolz-Schoembs relation, this indicates that the orbital period of the binary should be around 0.086 days i.e., within the period gap. During the superoutburst the superhump period was decreasing with the rate of P/Psh=-24.8(2.2)×10-5, which is one of the highest values ever observed in SU UMa systems. At the end of the plateau phase, the superhump period stabilized at a value of 0.08983(8) days. The superhump amplitude decreased from 0.3 mag at the beginning of the superoutburst to 0.1 mag at its end. In the case of V419 Lyr we have not observed clear secondary humps, which seems to be typical for long period systems.

12

CURious Variables Experiment (CURVE). CCD Photometry and Variable Stars in the Field of Open Cluster NGC 637

Pietrukowicz P., Olech A., Wiśniewski M., Kędzierski P., Mularczyk K., Złoczewski K., Starczewski S., Szaruga K.

Acta Astronomica

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2006

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Vol. 56, No. 3

267--275

EN

We present VI photometry for the open cluster NGC 637 which is located in the Cassiopeia region. Morphology of cluster color-magnitude diagram indicates that it is a young object with age of a few million years. The apparent distance modulus of the cluster is 13.9<(m-M)V<14.3 mag, while reddening is 0.69

13

Curious Variables Experiment (CURVE). CCD Photometry of Dwarf Nova V660 Herculis

Olech A., Złoczewski K., Cook L. M., Mularczyk K., Kędzierski P., Wiśniewski M.

Acta Astronomica

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2005

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Vol. 55, No. 2

237--246

EN

We report extensive photometry of the dwarf nova V660 Her. During our campaign, lasting from August 2003 to November 2004, we recorded one bright eruption which turned out to be a superoutburst lasting about 15 days and having amplitude of ≈4.5 mag. Clear superhumps with a mean period of Psh=0.080924(18) days (116.53±0.03 min) were present during all nights of the superoutburst. The period of the superhumps was not stable and in the interval covered by our observations it decreased with a rate of P/Psh=-4.0(1.4)×10-5. Based on our data and the known orbital period of the binary we calculate the period excess of 3.4±0.1%, which is typical for an SU UMa star at this orbital period. This value indicates that the mass ratio of the system is q=0.154

14

Curious Variables Experiment (CURVE). TT Bootis - Superhump Period Change Pattern Confirmed

Olech A., Cook L. M., Złoczewski K., Mularczyk K., Kędzierski P., Udalski A., Wiśniewski M.

Acta Astronomica

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2004

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Vol. 54, No. 3

233--247

EN

We report extensive multi-station photometry of TT Boo during its June 2004 superoutburst. The amplitude of the superoutburst was about 5.5 mag and its length about 22 days. The star showed a small re-brightening starting around the 9th day of the superoutburst. During entire bright state we observed clear superhumps with amplitudes from 0.07 mag to 0.26 mag and a mean period of Psh=0.0779589(47) days (112.261±0.007 min). The period was not constant but decreased at the beginning and the end of superoutburst and increased in the middle phase. We argue that the complicated shape of the O-C diagram is caused by real period changes rather than by phase shifts. Combining the data from two superoutbursts, 1989 and 2004, allowed us to trace the birth of the late superhumps and we conclude that it is a rather quick process lasting about one day.

15

Curious Variables Experiment (CURVE). IX Dra - a Clue for Understanding Evolution of Cataclysmic Variable Stars

Olech A., Złoczewski K., Mularczyk K., Kędzierski P., Wiśniewski M., Stachowski G.

Acta Astronomica

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2004

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Vol. 54, No. 1

57--85

EN

We report extensive photometry of frequently outbursting dwarf nova IX Dra. During five months of observations the star went into three superoutbursts and seven ordinary outbursts. This allowed us to determine its supercycle and cycle lengths as equal to 54±1 and 3.1±0.1 days, respectively. During the September 2003 superoutburst, which had the best observational coverage, IX Dra displayed clear superhumps with a period of Psh=0.066968(17) days (96.43±0.02 min). This period was constant during the whole superoutburst. Another period, which was clearly present in the light curve of IX Dra in superoutburst, had a value of 0.06646(6) days (95.70±0.09 min) and we interpret it as the orbital period of the binary. Thus IX Dra is the first SU UMa star showing orbital modulation during the entire superoutburst. The beat between these two periods is the main cause of an unusual phase reversal of superhumps - a phenomenon which was previously observed in ER UMa. If our interpretation of the second periodicity is correct, IX Dra has an extremely low period excess ε equal to only 0.76%±0.03%. This implies very low mass ratio q=0.035±0.003, which strongly suggests that the system contains a brown dwarf-like degenerate secondary of mass ≈0.03 Msolar and that IX Dra is the most evolved dwarf nova known. Such a very low mass ratio results in the outer edge of the accretion disk reaching 80% of the distance between the components of the system. In turn, this allows the disk particles to enter a 2:1 resonance and leads to the appearance of the orbital period in the light curve of the entire superoutburst. The high level of activity and brightness of IX Dra indicate that very old cataclysmic variables go through episodes of increased activity leading to loss of angular momentum through mass loss from the system. Modulations with the orbital period are also detectable during normal outbursts and in quiescence.

16

Superhumps in V1141 Aquilae

Olech A.

Acta Astronomica

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2003

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Vol. 53, No. 1

85--92

EN

Results of the CCD observations of the 2002 superoutburst of V1141 Aql are described. We have detected clear superhumps characterized by the period of 0.05930(5) days, which clearly indicates that the star is a member of SU UMa class of dwarf novae.

17

Curious Variables Experiment (CURVE). Superhump Period Change Pattern in KS UMa and Other Dwarf Novae

Olech A., Schwarzenberg-Czerny A., Kędzierski P., Złoczewski K., Mularczyk K., Wiśniewski M.

Acta Astronomica

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2003

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Vol. 56, No. 2

175--194

EN

We report extensive photometry of the dwarf nova KS UMa throughout its 2003 superoutburst till quiescence. During the superoutburst the star displayed clear superhumps with a mean period of Psh=0.070092(23) days. In the middle stage of superoutburst the period was increasing with a rate of P/P=(21±12)×10-5 and later was decreasing with a rate of P/P=-(21±8)×10-5. At the end of superoutburst and during first dozen days of quiescence the star was showing late superhumps with a mean period of Plate=0.06926(2) days. This phenomenon was observed even 30 days after beginning of the superoutburst. In quiescence the star shows quasi-periodic modulations with amplitude reaching 0.5 mag. The most common structure observed during this stage was sinusoidal wave characterized by a period of about 0.1 days. Comparing KS UMa to other SU UMa stars we conclude that this group of dwarf novae shows decreasing superhump periods at the beginning and the end of superoutburst but increasing period in the middle phase.

18

Nova V1974 Cyg - Results of the 1997 Campaign

Olech A.

Acta Astronomica

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2002

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Vol. 52, No. 3

273--291

EN

This report analyzes the I-band CCD photometry of Nova V1974 Cyg from the 1997 observational season. The analysis shows that both short-term modulations with periods of 0.0813 and 0.085 days are still present in the light curve of the star. We confirmed the stability of the shorter period which is interpreted as the orbital period of the binary system. Its value, determined using the O-C residuals, is Porb=0.08125873(23) days=117.0126(3) min. The longer period, which appeared in the light curve in 1994, was decreasing until the beginning of 1995 but then started to increase quite rapidly. In October 1996 the value of the period was 122.67±0.02 min. Until the next observing run the period significantly decreased. Its value, as determined from our observations performed in July 1997, was 121.87±0.12 min. This means that the rate of change of the period in 1996-1997 was as high as P≈10-6. Such a rapid change of the period requires a large amount of rotational kinetic energy, if we assume that a 122-min periodicity is the rotation period of a white dwarf. Thus the more probable explanation is the hypothesis that the longer period including a superhump period is caused by the precession of an accretion disc surrounding a white dwarf primary.

19

Co wybrać - kremację, czy pochówek?

Olech A., Rusin K., Wandrasz J. W.

Przegląd Komunalny

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1999

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nr 12

60-63

PL

Ewolucja populacji ludzi na Ziemi - licząc od 10 tysięcy lat przed naszą erą - pokazuje, że w ciągu ostatnich 50 lat nastąpił okres szybkiego wzrostu zaludnienia. W tym czasie ludność świata zwiększyła się o tyle ile wynosił jej wzrost w czasie 2,5 min lat dzielących nas od homo erectus. Szacunki liczby ludności świata w 2050 r. wahają się od 7,8 mld do 12,5 mld. Wzrost ludzkiej populacji niesie ze sobą konieczność rozwiązywania problemów cywilizacyjnych, a w tym i jednego z najważniejszych, związanego z zachowaniem godności do właściwego pochówku.