J. Krzesinski

Pedagogical University of Cracow, Cracovia, Lesser Poland Voivodeship, Poland

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Publications (193)526.63 Total impact

  • J. Krzesinski
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    ABSTRACT: Context. It has been suggested that two weak signals observed in the low frequency region of the Fourier transform amplitude spectra from the KIC 5807616 Q5-Q8 data can be interpreted as a result of the light reflection from planets orbiting the host star. Ever since the last results on KIC 5807616 were presented, the Kepler spacecraft has collected over two years of additional data, which we analysed using asteroseismological methods. Aims. To verify and improve on previous results, we used the Q 5-Q 17 Kepler data to identify pulsational modes, determine multiplet splitting, and to re-analyse the low frequency region between 33-49 μHz where two frequencies, claimed as the planetary signature, were found. Methods. Since Fourier transform amplitude spectra of the KIC 5807616 data do not show any clear multiplets, we used two stable acoustic modes to determine the theoretical width of gravity mode multiplets and their splittings. The period spacing and histograms of common multiplet component separations were used to identify pulsation modes and the observed gravity mode splittings. In the low frequency region, we analysed the amplitude variations of two planetary signature frequencies over the whole observing run. Results. We determined the rotational period of the star from the splittings. Analysis of the low frequency region shows that the amplitude and frequency change of the signals found there have similar characteristics to other gravity modes. Conclusions. New data allow for identifying gravity modes in a limited period range, as well as better rotational period estimations. We suggest that the so-called planetary signature frequencies found in previous work might instead be pulsation modes visible beyond the cut-off frequency of the star.
    No preview · Article · Jul 2015 · Astronomy and Astrophysics
  • A. S. Baran · J. H. Telting · P. Nemeth · Sz Bachulski · J. Krzesinski
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    ABSTRACT: We present our analysis of Kepler data of a pulsating subdwarf B star, KIC8302197. We used Q5-17 data and applied a Fourier technique to extract 30 significant pulsation modes. We searched for multiplets and period-spacing sequences to perform a mode identification and to derive a rotation period. To our surprise, KIC 8302197 does not show any multiplets. We explain the lack of multiplets by either a very slow rotation (longer than similar to 1000 days) or a unique (pole-on) orientation of the pulsation axis. Our mode identification relied solely on period spacing. We were successful in identifying modal degrees of most of the detected modes. An analysis of the period stability did not show any evidence of a companion to the host star. In addition to photometric data, several spectroscopic observations were collected. Our twelve radial-velocity measurements constrain a possible orbital radial-velocity amplitude to be smaller than about 10 km s(-1). Furthermore, based on color indices we constrained a possible companion to be an M or later type main sequence, a compact or a substellar object. We found that the atmospheric parameters (T-eff = 27 450 +/- 200 K, log g = 5.438 +/- 0.033 dex, and log(nHe/nH) = -2.56 +/- 0.07 dex) of KIC 8302197 are consistent with other slow pulsating subdwarf B stars. From the optical spectra we derived C, N, O, Si and Fe abundances, and set an upper limit for the S abundance.
    No preview · Article · Jan 2015 · Astronomy and Astrophysics
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    Full-text · Article · Mar 2014
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    S. Torres · E. García-Berro · J. Krzesinski · S. J. Kleinman
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    ABSTRACT: We present a coherent and detailed Monte Carlo simulation of the population of hot white dwarfs. We assess the statistical significance of the hot end of the white dwarf luminosity function and the role played by the bolometric corrections of hydrogen-rich white dwarfs at high effective temperatures. We use the most up-to-date stellar evolutionary models and implement a full description of the observational selection biases to obtain realistic simulations of the observed white dwarf population. Our theoretical results are compared with the luminosity function of hot white dwarfs obtained from the Sloan Digital Sky Survey (SDSS), for both DA and non-DA white dwarfs. We find that the theoretical results are in excellent agreement with the observational data for the population of white dwarfs with hydrogen deficient atmospheres (non-DA white dwarfs). For the population of white dwarfs with hydrogen-rich atmospheres (white dwarfs of the DA class), our simulations show some discrepancies with the observations for the brightest luminosity bins. These discrepancies can be attributed to the way in which the masses of the white dwarfs contributing to this luminosity bin have been computed, as most of them have masses smaller than the theoretical lower limit for carbon-oxygen white dwarfs. We conclude that the way in which the observational luminosity function of hot white dwarfs is obtained is very sensitive to the particular implementation of the method used to derive the masses of the sample. We also provide a revised luminosity function for hot white dwarfs with hydrogen-rich atmospheres.
    Full-text · Article · Feb 2014 · Astronomy and Astrophysics
  • J. Krzesinski · A. Blokesz · A.S. Baran · S. Bachulski
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    ABSTRACT: In this paper we present our study of KIC 10670103, a pulsating hot subdwarf located in the Kepler field. The study is based on three years of data taken by the Kepler spacecraft during Q5-16. Using Fourier analysis, we investigate periodic signals associated with pulsations. Using asymptotic relationships and rotational multiplets we identify modal degrees. The amplitude spectrum appears to be rich in l = 1 and 2 multiplets, allowing derivation of a 90 days rotation period for this star. Comparing the pattern of identified gravity mode period spacings with theoretical models, we show that KIC 10670103 is a thick-envelope sdB star.
    No preview · Article · Jan 2014
  • R. Matson · E. Helin · K. Sarneczky · J. Krzesinski · G. V. Williams
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    ABSTRACT: CBET 3396 available at Central Bureau for Astronomical Telegrams.
    No preview · Article · Feb 2013
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    ABSTRACT: Available from the Minor Planet Center.
    No preview · Article · Feb 2013
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    ABSTRACT: Here, we report on the white dwarf catalog built from the SDSS DR7 (Cat. II/294). We have applied automated techniques supplemented by complete, consistent human identifications of each candidate white dwarf spectrum. We make use of the latest SDSS reductions and white dwarf model atmosphere improvements in our spectral fits, providing logg and Teff determinations for each identified clean DA and DB where we use the word "clean" to identify spectra that show only features of non-magnetic, nonmixed, DA or DB stars. Our catalog includes all white dwarf stars from the earlier Kleinman et al. (2004, Cat. J/ApJ/607/426) and Eisenstein et al. (2006, Cat. J/ApJS/167/40) catalogs, although occasionally with different identifications. (1 data file).
    No preview · Article · Jan 2013
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    ABSTRACT: We present a new catalog of spectroscopically-confirmed white dwarf stars from the Sloan Digital Sky Survey Data Release 7 spectroscopic catalog. We find 20,407 white dwarf spectra, representing 19,712 stars, and provide atmospheric model fits to 14,120 DA and 1011 DB white dwarf spectra from 12,843 and 923 stars, respectively. These numbers represent a more than factor of two increase in the total number of white dwarf stars from the previous SDSS white dwarf catalog based on DR4 data. Our distribution of subtypes varies from previous catalogs due to our more conservative, manual classifications of each star in our catalog, supplementing our automatic fits. In particular, we find a large number of magnetic white dwarf stars whose small Zeeman splittings mimic increased Stark broadening that would otherwise result in an overestimated log(g) if fit as a non-magnetic white dwarf. We calculate mean DA and DB masses for our clean, non-magnetic sample and find the DB mean mass is statistically larger than that for the DAs.
    Full-text · Article · Dec 2012 · The Astrophysical Journal Supplement Series
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    ABSTRACT: This paper describes the Fourth Data Release of the Sloan Digital Sky Survey (SDSS), including all survey-quality data taken through 2004 June. The data release includes five-band photometric data for 180 million objects selected over 6670 deg2 and 673,280 spectra of galaxies, quasars, and stars selected from 4783 deg2 of those imaging data using the standard SDSS target selection algorithms. These numbers represent a roughly 27% increment over those of the Third Data Release; all the data from previous data releases are included in the present release. The Fourth Data Release also includes an additional 131,840 spectra of objects selected using a variety of alternative algorithms, to address scientific issues ranging from the kinematics of stars in the Milky Way thick disk to populations of faint galaxies and quasars.
    Full-text · Article · Nov 2012
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    S. Torres · E. García-Berro · J. Krzesinski · S. J. Kleinman
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    ABSTRACT: We present a detailed Monte Carlo simulation of the population of the hot branch of the white dwarf luminosity function. We used the most up-to-date stellar evolutionary models and we implemented a full description of the observational selection biases. Our theoretical results are compared with the luminosity function of hot white dwarfs obtained from the Sloan Digital Sky Survey (SDSS), for both DA and non-DA white dwarfs. For non-DA white dwarfs we find an excellent agreement with the observational data, while for DA white dwarfs our simulations show some discrepancies with the observations for the brightest luminosity bins, those corresponding to L>= 10 L_sun.
    Full-text · Article · Sep 2012
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    ABSTRACT: 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 collected. We numerically modelled the variations in brightness and colour during the eclipses. We tested models with different disk structure. We considered the possibility of disk precession. The complete set of observational data collected during the last three eclipses are made available to the astronomical community. Two blue maxima in the colour indices were detected during these two eclipses, one before and one after the photometric minimum. The first (stronger) blue maximum is simultaneous with a "bump" that is very clear in all the UBVRI light curves. Variations in the spectral line profiles seem to be recurrent during each cycle. NaI lines always show at least three absorption components during the eclipse minimum and strong absorption is superimposed on the H_alpha emission. These observations confirm that the eclipsing object in EE Cep system is indeed a dark, dusty disk around a low luminosity object. The primary appears to be a rapidly rotating Be star that is strongly darkened at the equator and brightened at the poles. Some of the conclusions of this work require verification in future studies: (i) a complex, possibly multi-ring structure of the disk in EE Cep; (ii) our explanation of the "bump" observed during the last two eclipses in terms of the different times of obscuration of the hot polar regions of the Be star by the disk; and (iii) our suggested period of the disk precession (~11-12 P_orb) and predicted depth of about 2 mag the forthcoming eclipse in 2014.
    Full-text · Article · Apr 2012 · Astronomy and Astrophysics
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    ABSTRACT: We use SDSS photometry of 73 million stars to simultaneously obtain best-fit main-sequence stellar energy distribution (SED) and amount of dust extinction along the line of sight towards each star. Using a subsample of 23 million stars with 2MASS photometry, whose addition enables more robust results, we show that SDSS photometry alone is sufficient to break degeneracies between intrinsic stellar color and dust amount when the shape of extinction curve is fixed. When using both SDSS and 2MASS photometry, the ratio of the total to selective absorption, $R_V$, can be determined with an uncertainty of about 0.1 for most stars in high-extinction regions. These fits enable detailed studies of the dust properties and its spatial distribution, and of the stellar spatial distribution at low Galactic latitudes. Our results are in good agreement with the extinction normalization given by the Schlegel et al. (1998, SFD) dust maps at high northern Galactic latitudes, but indicate that the SFD extinction map appears to be consistently overestimated by about 20% in the southern sky, in agreement with Schlafly et al. (2010). The constraints on the shape of the dust extinction curve across the SDSS and 2MASS bandpasses support the models by Fitzpatrick (1999) and Cardelli et al. (1989). For the latter, we find an $R_V=3.0\pm0.1$(random) $\pm0.1$(systematic) over most of the high-latitude sky. At low Galactic latitudes (|b|<5), we demonstrate that the SFD map cannot be reliably used to correct for extinction as most stars are embedded in dust, rather than behind it. We introduce a method for efficient selection of candidate red giant stars in the disk, dubbed "dusty parallax relation", which utilizes a correlation between distance and the extinction along the line of sight. We make these best-fit parameters, as well as all the input SDSS and 2MASS data, publicly available in a user-friendly format.
    Full-text · Article · Nov 2011
  • Article: 2010 OC103
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    ABSTRACT: Available from the Minor Planet Center.
    No preview · Article · Jul 2011
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    L. Fox Machado · A.S. Baran · M. Winiarski · J. Krzesiński · M. Dróżdz
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    ABSTRACT: The Mt. Suhora M\,dwarf survey searching for pulsations in low mass main sequence stars has acquired CCD photometry of 46 M\,dwarf stars during the first year of the project (Baran et al 2011). As a by-product of this search hundreds field stars have been checked for variability. This paper presents our initial result of a search for periodic variables in field stars observed in the course of the survey. On the basis of the periodicity and the shape of the light curves, eight new variables has been detected, among which five are $\delta$ Scuti stars and three likely RR Lyrae stars. Although variation in one of the stars has been previously detected, it was classified incorrectly. To support our classification, in August 2010, we performed spectroscopic observations to derive spectral types and luminosity classes for all eight variable stars.
    Full-text · Article · Jun 2011 · New Astronomy
  • Baran A S · Krzesinski J · Kawaler S.D
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    ABSTRACT: We present the first results of our M dwarf survey in search for stellar pulsation in low-mass main-sequence stars. Theoretical calculations made by one of the present authors (S. K.) predict that varepsilon-mechanism might drive a fundamental radial mode in these stars and therefore pulsations could be observed photometrically. Although M dwarfs are known for their flare and spot activity, they have not yet been the subject of dedicated time-series surveys for pulsation. In this presentation we include the light curves along with amplitude spectra and Phase Dispersion Minimization analysis of a dozen of M red dwarfs, which have been observed during the first year of our survey. None of them seems to be a pulsating star. As a by-product of our search, we have detected many flares of M dwarfs and variation in seven field stars. The survey will last for two more years and during that period more than a hundred of M0-M4 type main-sequence stars will be observed.
    No preview · Conference Paper · Mar 2011
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    ABSTRACT: We present the first results of our M dwarf survey in search for stellar pulsation in low mass main sequence stars. Theoretical calculations predict that ɛ mechanism might drive a fundamental radial mode in these stars and therefore pulsations could be observed photometrically. Although M dwarfs are known for their flare and spot activity they have not yet been the subject of dedicated time-series surveys for pulsation. In this work we include the light curves and amplitude spectra of 46 M dwarfs, which have been observed during the first two years of our survey. We did not detect any pulsations yet. As a by-product of our search, we describe the light curves of some flare M dwarfs. The survey will last for two more years and during that period more than a hundred of M0-M4 type main sequence stars will be observed.
    No preview · Article · Mar 2011 · Acta Astronomica -Warsaw and Cracow-
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    ABSTRACT: 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.
    Full-text · Article · Feb 2011
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    A. Baran · S.D. Kawaler · J. Krzesinski
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    ABSTRACT: We present our new observing project searching for pulsations in M dwarfs.
    Preview · Article · Nov 2010 · Proceedings of the International Astronomical Union

  • No preview · Article · Sep 2010

Publication Stats

14k Citations
526.63 Total Impact Points

Institutions

  • 1991-2014
    • Pedagogical University of Cracow
      • Institute of Physics
      Cracovia, Lesser Poland Voivodeship, Poland
  • 2007-2009
    • University of Washington Seattle
      • Department of Astronomy
      Seattle, Washington, United States
    • Victoria University of Wellington
      • School of Chemical and Physical Sciences
      Wellington, Wellington, New Zealand
  • 2008
    • Akademia Ignatianum w Krakowie
      Cracovia, Lesser Poland Voivodeship, Poland
    • Tel Aviv University
      • Department of Physics and Astronomy
      Tell Afif, Tel Aviv, Israel
    • New Mexico State University
      • Department of Astronomy
      Las Cruces, NM, United States
  • 2006-2007
    • Princeton University
      • Department of Astrophysical Sciences
      Princeton, New Jersey, United States
  • 2003
    • The University of Tokyo
      • Institute for Cosmic Ray Research
      Tokyo, Tokyo-to, Japan
    • Fermi National Accelerator Laboratory (Fermilab)
      Batavia, Illinois, United States
  • 2002
    • Los Alamos National Laboratory
      Лос-Аламос, California, United States
    • Johns Hopkins University
      • Department of Physics and Astronomy
      Baltimore, Maryland, United States
  • 1999
    • University of Cape Town
      • Department of Astronomy
      Kaapstad, Western Cape, South Africa
  • 1998
    • University of Texas at Austin
      • Department of Astronomy
      Austin, Texas, United States
    • Université de Montréal
      Montréal, Quebec, Canada