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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.

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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.

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Międzynarodowy Rok Astronomii 2009: obchody międzynarodowe oraz inicjatywy lokalne. Kilka luźnych uwag na temat popularyzacji astronomii

Czerny B., Janiuk A., Złoczewski K.

Postępy Fizyki

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2009

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T. 60, z. 5

178-184

PL

Nasz esej porusza pewne problemy związane z Międzynarodowym Rokiem Astronomii 2009. Opisujemy dość szczegółowo ogólnopolski konkurs, ogłoszony z tej okazji przez Polskie Towarzystwo Astronomiczne, Centrum Astronomiczne im. Mikołaja Kopernika PAN, czasopismo Wiedza i Życie i kilka innych organizacji. Traktujemy konkurs i ogłoszone wyniki jako pretekst do kilku przemyśleń na temat powszechnego podejścia do astronomii. Nakreślamy też inne przykładowe inicjatywy związane z popularyzacją astronomii i wspominamy o aspektach międzynarodowych, ale w żadnej mierze nie w sposób wyczerpujący.

EN

In this open form article we discuss some issues related to the International Year of Astronomy 2009. We describe in detail the competition which was organized by the Polish Astronomical Society, Copernicus Astronomical Center, popular science magazine Wiedza i Życie, and several other organizations, with the aim to attract people to astronomy. We comment on the results of the competition and on the way how people commonly see astronomy. We locate this initiative at the broader background of other initiatives in Poland, and briefly comment on international activity related to IYA 2009.

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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.

5

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.

6

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

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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

8

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.

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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.

10

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.