Osaka Kyoiku University Researcher Information
日本語 ｜ English
研究者業績
基本情報
- 所属
- 大阪教育大学 理数情報教育系 准教授
- 学位
- 博士（理学）(2000年 京都大学)
- 連絡先
- katsura
cc.osaka-kyoiku.ac.jp - 研究者番号
- 90362748
- ORCID ID
https://orcid.org/0000-0002-5277-568X- J-GLOBAL ID
- 200901049121591542
- researchmap会員ID
- 6000005612
- 外部リンク
研究分野
2論文
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Publications of the Astronomical Society of Japan 61(sp2) S395-S616 2009年12月 査読有りAbstract We systematically surveyed period variations of superhumps in SU UMa-type dwarf novae based on newly obtained data and past publications. In many systems, the evolution of the superhump period is found to be composed of three distinct stages: an early evolutionary stage with a longer superhump period, a middle stage with systematically varying periods, and a final stage with a shorter, stable superhump period. During the middle stage, many systems with superhump periods of less than 0.08 d show positive period derivatives. We present observational characteristics of these stages and give greatly improved statistics. Contrary to an earlier claim, we found no clear evidence for a variation of period derivatives among different superoutbursts of the same object. We present an interpretation that the lengthening of the superhump period is a result of the outward propagation of an eccentricity wave, which is limited by the radius near the tidal truncation. We interpret that late-stage superhumps are rejuvenated excitation of a 3:1 resonance when superhumps in the outer disk are effectively quenched. The general behavior of the period variation, particularly in systems with short orbital periods, appears to follow a scenario proposed in Kato, Maehara, and Monard (2008, PASJ, 60, L23). We also present an observational summary of WZ Sge-type dwarf novae. Many of them have shown long-enduring superhumps during a post-superoutburst stage having longer periods than those during the main superoutburst. The period derivatives in WZ Sge-type dwarf novae are found to be strongly correlated with the fractional superhump excess, or consequently with the mass ratio. WZ Sge-type dwarf novae with a long-lasting rebrightening or with multiple rebrightenings tend to have smaller period derivatives, and are excellent candidates for those systems around or after the period minimum of evolution of cataclysmic variables.
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Information Bulletin on Variable Stars 5576 1-3 2004年11月 査読有りWe detected the short-time variability of the GRB021004 afterglow from 0.078 to 0.336 days after the burst....
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Publications of the Astronomical Society of Japan 56(sp1) S109-S123 2004年3月 査読有りAbstract We report on time-resolved photometric observations of the WZ Sge-type dwarf nova, EG Cnc (Huruhata’s variable), during its superoutburst in 1996–1997. EG Cnc, after the main superoutburst accompanied by the development of superhumps typical of a WZ Sge-type dwarf nova, exhibited a series of six major rebrightenings. During these rebrightenings and the following long fading tail, EG Cnc persistently showed superhumps having a period equal to the superhump period observed during the main superoutburst. The persistent superhumps had a constant superhump flux with respect to the rebrightening phase. These findings suggest that the superhumps observed during the rebrightening stage and the fading tail are a “remnant” of the usual superhumps, and are not newly triggered by rebrightenings. By a comparison with the 1977 outburst of this object and outbursts of other WZ Sge-type dwarf novae, we propose an activity sequence of WZ Sge-type superoutbursts, in which the current outburst of EG Cnc is placed between a single-rebrightening event and distinct outbursts separated by a dip. The post-superoutburst behavior of WZ Sge-type dwarf novae can be understood in the presence of a considerable amount of remnant matter behind the cooling front in the outer accretion disk, even after the main superoutburst. We consider that a premature quenching of the hot state due to the weak tidal effect under the extreme mass ratio of the WZ Sge-type binary is responsible for the origin of the remnant mass.
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Information Bulletin on Variable Stars 5454 1-3 2003年10月 査読有り筆頭著者...
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Astrophysical Journal 596 847-859 2003年10月 査読有り
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Astronomy and Astrophysics 408 651-661 2003年9月 査読有り
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High Energy Blazar Astronomy (ASP Conference Series 299) 211-211 2003年7月
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Astronomy and Astrophysics 402 315-319 2003年4月 査読有り
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Publications of the Astronomical Society of Japan 55 483-488 2003年4月 査読有りAbstract We carried out time-resolved $V$-band photometry of DM Lyr during long outbursts in 1996 July and in 1996 February–March at Ouda Station, Kyoto University, and at Osaka Kyoiku University. Since superhumps were clearly detected in the light curves, DM Lyr was first identified as being an SU UMa-type dwarf nova. The superhump period is 0.0673(2) d, and the superhump excess is 2.8(3)%. The duration of the superoutburst, the outburst amplitude, the decline rate in the plateau phase, and the superhump excess were typical values for a usual SU UMa star. According to visual and CCD observations reported to VSNET, this star has experienced a dramatic change of the outburst pattern from a superoutburst phase to a normal outburst phase. There may exist mechanisms to decrease the number of normal outbursts between two successive superoutbursts and to elongate the recurrence cycle of the superoutburst.
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Monthly Notices of the Royal Astronomical Society 339 1006-1010 2003年3月 査読有り筆頭著者
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Interplay of Periodic, Cyclic and Stochastic Variability in Selected Areas of the H-R Diagram (ASP Conference Series 292) 413-413 2003年3月
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Publications of the Astronomical Society of Japan 55 297-304 2003年2月 査読有り筆頭著者Abstract In this paper we present and discuss our time-resolved photometry of an eclipsing recurrent nova, U Sco, during an outburst in 1999, which was conducted from immediately after the optical maximum to the final fading toward the quiescence. In the first-ever complete light-curve, a few primary and secondary eclipses of the binary system were detected, and the timings of the minima were determined. We found that the eclipses showed no totality during the outburst. The depth of the primary eclipses was 0.4–0.8 mag, much shallower than that in quiescence. In the plateau phase, very little irradiation ($\leq 0.1 \,\mathrm{mag}$) was observed in the orbital light curve, which implies the existence and a large flaring rim of the accretion disk during the outburst. The minima of the eclipses were detected at earlier orbital phases for the predicted ephemerides. Thus, we obtained an orbital period change of the binary system as $\dot{P}/P =-1.7 (\pm 0.7) \times 10^{-6} \,\mathrm{yr}^{-1}$ from the $O-C$. Assuming that this period change is a result of the conservative mass transfer between the component stars, its mass-transfer rate reaches $\dot{M} = 2.4 (\pm 1.0) \times 10^{-6} \,{ { {M}_{\odot } } } \,\mathrm{yr}^{-1}$ for a $1.37 \,{ { {M}_{\odot } } }$ white dwarf and a $2.0 \,{ { {M}_{\odot } } }$ mass-donor companion, which is too high to cause shell flashes, even on a massive white dwarf. Therefore, this large rate of the period change strongly indicates a non-conservative mass transfer in the binary system.
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Publications of the Astronomical Society of Japan 54 999-1008 2002年12月 査読有りAbstract We observed the entire course of the 1998 outburst of V592 Her, which was originally reported as a nova in 1968. We have been able to construct a full light curve of the outburst, which is characterized by a rapid initial decline ($0.98 \,\mathrm{mag} \,\mathrm{d}^{-1}$), which smoothly developed into a plateau phase with a slower linear decline. We detected superhumps characteristic to SU UMa-type dwarf novae $\sim 7 \,\mathrm{d}$ after the optical maximum. The overall behavior of the light curve and the development of superhumps were characteristic to a WZ Sge-type dwarf nova. Combined with the past literature, we have been able to uniquely determine the superhump period to be 0.05648(2) d. From this period, together with a modern interpretation of the absolute magnitude of the outburst light curve, we conclude that the overall picture of V592 Her is not inconsistent with a lower main-sequence secondary star, in contrast to a previous claim that V592 Her contains a brown dwarf.
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Blazar Astrophysics with BeppoSAX and Other Observatories (Proceedings of the international workshop) 219-219 2002年12月
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Inflows, Outflows and Reprocessing around Black Holes (Proceedings of the 5th Italian AGN Meeting) 152-152 2002年11月
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The Physics of Cataclysmic Variables and Related Objects, ASP Conference Series 261 629 2002年10月
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Publications of the Astronomical Society of Japan 54 599-607 2002年8月 査読有りAbstract We report on the evolution of superhumps and late superhumps in an ultrashort period dwarf nova, 1RXS J232953.9$+$062814, during the superoutburst in 2001 November. Ordinary superhumps were observed throughout a plateau phase, a rapid fading phase, and a rebrightening phase. During the plateau phase, the superhump period increased with time at a large rate of $P_\mathrm{dot} = 1.19 \pm 0.24 \times 10^{-4}$. In conjunction with the rebrightening phenomenon, these characteristics indicate that an accretion disk expanded further outward from the $3:1$ resonance radius, which caused a large amount of left over matter at the outer disk, even after the superoutburst. In the post-outburst phase, we detected late superhumps superimposed on dominant double-peak modulations. Late superhumps were observed at least for 10 d without a significant period change. We detected the first normal outburst of this object on 2001 December 26. The interval between the superoutburst and this normal one is 53 d. This short recurrence time supports a high mass-transfer rate in this system. Concerning the evolutionary status of 1RXS J232953.9$+$062814, we propose that it is a progenitor of AM CVn stars on the evolutionary course of the cataclysmic variable channel in which systems have a secondary star with a hydrogen-exhausted core.
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Information Bulletin on Variable Stars 5262 1-4 2002年4月 査読有りV893 Sco is a recently rediscovered bright eclipsing dwarf nova below the period gap. Most recently, Mason et al. (2001) proposed an idea that V893 Sco is an ER UMa-type dwarf nova. From the analysis of our CCD observations and reports to VSNET, we show that V893 Sco bears no similar characters with ER UMa stars. We propose that the arguments in Mason et al. (2001), including the evolutionary status of ER UMa star as inferred from the observation of V893 Sco, need to be reconsidered....
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Publications of the Astronomical Society of Japan 54 235-240 2002年4月 査読有りWe construct a model for supercritical accretion disks with winds, where the mass-accretion rate highly exceeds the Eddington rate and a significant fraction of the accreting gas is expelled as a superwind, under a self-similar treatment. The mass-accretion rate $ \dot{M}$ decreases with radius $ r$ as $ \dot{M} \propto r^{s+1/2}$, where $ s$ ($ \geq-1/2$) is some arbitrary constant. The surface density $ \Sigma$ and the disk central temperature $ T_\mathrm{c}$ vary as $ \Sigma \propto r^s$ and $ T_\mathrm{c} \propto r^{s/4-1/2}$, respectively. In spite of such a modification, we found that the scaleheight $ H$ and the surface temperature $ T$ of such a superdisk with a superwind is very similar to those of a superdisk without winds; $ H \propto r$ and $ T \propto r^{-1/2}$. Furthermore, the optical depth of the wind becomes remarkably smaller than that in the spherical case, because mass loss takes place at various radii on the disk, and the gas distribution in the wind is not concentrated, but diluted in space. Hence, the observational appearances of both superdisks are quite similar, except for the existence of a strong wind, unless the wind mass-loss rate highly exceeds the critical rate. We then apply a superdisk with a superwind to supersoft X-ray sources. In our picture, although the accretion rate in these objects is of the order of $10^{-5} \,{ { {M}_{\odot } } } \,\mathrm{yr}^{-1}$ at the outer edge of the disk and a sufficiently thick superdisk may be established, most of the gas is expelled by the superwind, and the accretion rate at the center becomes of the order of $10^{-7} \hbox{--} 10^{-6} \,{ { {M}_{\odot } } } \mathrm{yr}^{-1}$.
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Publications of the Astronomical Society of Japan 54 285-298 2002年4月 査読有りAbstract We report on photometric and spectroscopic observations of a possible halo black-hole X-ray nova, XTE J1118$ +$480 ($ =$ KV UMa) during outburst. Our photometric monitoring during the main outburst revealed that the optical maximum as well as the onset of the outburst precede those in the X-ray region. This indicates that the event was an “outside-in” type outburst and that its optical flux was dominated by viscous heating, itself, and not the effect of X-ray irradiation. Based on these results, we suggest an outburst scenario analogous to superoutbursts in SU UMa-type dwarf novae. This scenario predicts a superhump phenomenon, which we indeed detected throughout the outburst. We determined its period to be $ 0.170529\pm 0.000006 \,\mathrm{d}$, which is slightly longer than the orbital periods suggested from spectroscopic observations. We have furthermore revealed the first evidence of a continuous period decreasing in X-ray novae. The most prominent feature in our optical spectrum is a double-peak He II 4686Å emission line having an asymmetric profile with an outstanding blue side peak. Using a Doppler mapping method, we found that the He II emission originates from the accretion disk, which particularly concentrates on the hot spot. The time that the blue peak becomes strongest corresponds to a superhump peak. This implies that we see an elongated side of an eccentric disk at that time and, hence, it may cause an asymmetric emission profile. Substituting the observed fractional superhump excess for a theoretically expected relation between it and the mass ratio, we estimate that the black-hole mass is larger than $9.5 \,{ { {M}_{\odot } } }$. XTE J1118$ +$480 thus has a large mass of a compact object compared with the typical black-hole X-ray novae.
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Publications of the Astronomical Society of Japan 54 L15-L18 2002年4月 査読有りAbstract We revealed that the dwarf nova 1RXS J232953.9+062814 is an SU UMa-type system with a superhump period of $ 66.774\pm 0.010 \,\mathrm{min}$. The short period strongly indicates that the orbital period of this object is below the period minimum of cataclysmic variables. The superhump period is $ 4.04\pm 0.02$% longer than the photometric period during quiescence ($ 64.184\pm 0.003 \,\mathrm{min}$), which is probably associated with the orbital period. Although the standard evolutionary scenario of cataclysmic variables predicts lower mass-transfer rates in systems with shorter orbital periods, we found firm evidence of a relatively high mass-transfer rate from its large proper motion and bright apparent magnitude. Its proximity indicates that we have overlooked a number of objects in this new class. With the analogous system of V485 Cen, these objects establish the first subpopulation in hydrogen-rich cataclysmic variables below the period minimum.
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Publications of the Astronomical Society of Japan 54 L7-L10 2002年2月 査読有りAbstract Intermediate-resolution phase-resolved spectra of WZ Sge were obtained on five consecutive nights (July 23–27) covering the initial stage of the 2001 superoutburst. Double-peaked emission lines of He II at 4686 Å, which were absent on July 23, emerged on July 24 together with emission lines of C III$/$ N III Bowen blend. Analyses of the He II emission lines using the Doppler tomography revealed an asymmetric spiral structure on the accretion disk. This finding demonstrates that spiral shocks with a very short orbital period can arise during the initial stage of an outburst and may be present in all SU UMa stars.
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Astronomy and Astrophysics 381 L41-L44 2002年1月 査読有り
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Journal of Astronomical Data 7 1-9 2001年12月 査読有りWe present time-resolved optical spectroscopy of the dwarf novae WX Cet, TU Men, CU Vel and HS Vir. The spectra show prominent Balmer emission lines which can be used as testers of the physical conditions inside the accretion disk. These digital spectra are made available to the astronomical community as a first step in the formation of a digital database in support of spectroscopic studies related, for instance, to the long-term evolution of dwarf novae....
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Publications of the Astronomical Society of Japan 53 L51-L54 2001年12月 査読有りAbstract We observed a new dwarf nova, IX Dra, for 46 days between 2000 November 10 and 2001 June 17, and revealed that IX Dra is the fifth member of a peculiar group of SU UMa stars, called ER UMa stars. The light curve is almost perfectly identical to that of V1159 Ori: supercycle, 53 d; interval of normal outbursts, 3–4 d; duty cycle, $\sim 30\%$; and the outburst amplitude, 2.5 mag. From a time-series observation during the superoutbursts, we obtained a presumable superhump period of 0.067 d. We note that some clustering may exist in the period distribution of ER UMa stars. It is needed to confirm this clustering by a larger number of examples.
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Astronomy and Astrophysics 378 487-494 2001年11月 査読有り筆頭著者
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Publications of the Astronomical Society of Japan 53 893-900 2001年10月 査読有りAbstract We observed the 1998 November superoutburst of WX Cet, a dwarf nova originally proposed as a WZ Sge-like system. The observation established that WX Cet is an SU UMa-type dwarf nova with a mean superhump period of 0.05949(1)d, which is 2.1% longer than the reported orbital period. The lack of early superhumps at the earliest stage of the superoutburst, the rapid development of usual superhumps, and the possible rapid decay of late superhumps seem to support that WX Cet is a fairly normal large-amplitude SU UMa-type dwarf nova, rather than a WZ Sge-type dwarf nova with a number of peculiarities. However, a period increase of superhumps at a rate $\dot{P}/P = +8.5\pm 1.0 \times 10^{-5}$ was observed, which is one of the largest $\dot{P}/P$ ever observed in SU UMa-type dwarf novae. A linear decline of light, with a rate of $0.10 \,\mathrm{mag} \,\mathrm{d}^{-1}$, was observed in the post-superoutburst stage. This may be an exemplification of the decay of the viscosity in the accretion disk after the termination of a superoutburst, mechanism of which is proposed to explain a variety of post-superoutburst phenomena in some SU UMa-type dwarf novae.
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Publications of the Astronomical Society of Japan 53 905-913 2001年10月 査読有りAbstract We report here on time-resolved photometric observations of the superoutburst of a dwarf nova, RZ Leo, which occurred during 2000 December–2001 January. We reveal the following characteristics of the outburst based on our observations: long duration, large amplitude, and the existence of two types of superhumps — “early superhumps” and “normal superhumps”. In addition to the extremely low frequency of the outbursts, the characteristics of the outburst strongly indicate that RZ Leo is the fifth member of the WZ Sge-type dwarf novae. The orbital period of RZ Leo is 0.07651 d, which is remarkably longer than the “canonical” period of other WZ Sge stars ($\sim 0.058\,\mathrm{d}$). The longer period indicates a non-degenerate secondary of RZ Leo, which suggests that the idea of a low quiescence viscosity due to a degenerate brown dwarf secondary may not be correct. The present discovery of RZ Leo as being a WZ Sge star provides the first clear indication that the decay of magnetic turbulence in accretion disks of quiescent WZ Sge stars plays an important role in producing the proposed low quiescent viscosity.
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Publications of the Astronomical Society of Japan 53 111-117 2001年2月 査読有りIn supersoft X-ray sources the mass accretion rate is roughly equal to the Eddington rate, and traditional standard disks cannot be adequate. We thus propose a supercritical accretion disk (superdisk) for supersoft X-ray sources. We have found that superdisks exhibit various distinct features, compared with standard thin disks. The continuous spectra of superdisks generally become flat ($ \nu S_\nu \sim \nu^0$), which are greatly different from those of disk-blackbody spectra, as expected in the usual accretion disk systems. This flat nature is not so prominent in supersoft X-ray sources, compared with that in the superdisk around a black hole, since the radial extension of the disk is much smaller. Moreover, irradiation becomes important for a smaller accretion rate system. The superdisk picture was applied to RX J0019.8+2156, and reproduced its spectra and optical light curves well.
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Information Bulletin on Variable Stars 5023 1-4 2001年1月 査読有り...
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Astronomy and Astrophysics 363 1029-1039 2000年11月 査読有り筆頭著者We present time-resolved optical spectroscopic and photometric observations of the re-discovered dwarf nova <ASTROBJ>V893 Sco</ASTROBJ>. The orbital period of 0fd07610 (3) derived from the radial velocity and equivalent width variations of the Hα emission line is confirmed. The photometric light curves clearly show the eclipse of the accretion disk. A mass of the white dwarf ~ 0.5-0.6 Msun is derived from the orbital amplitude K1 = 86 +/- 11 km s-1 and the eclipse constraint. The mass ratio is likely small enough to make V893 Sco an SU UMa-type dwarf nova, though this object has shown only normal outbursts in its light curve. Time-resolved Doppler maps for the emission lines show two isolated Hα emission regions, which are associated with a strong hot spot and the irradiated secondary star. Based on observations obtained at ESO La Silla Observatory (ESO Proposal 61.D-0395)...
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Publications of the Astronomical Society of Japan 52 L15-L20 2000年8月 査読有りAbstract We discovered an optical counterpart of about 13 mag of a soft X-ray transient, XTE J1118+480 on 2000 March 30. We performed astrometry and provided an accurate position of R.A. = 11h18m10s.85, Decl. = +48°02′12″.9. The outbursting object has been identified with a 18.8 mag star in the USNO catalog. Our pre-discovery data shows another outburst during 2000 January, again coinciding with an outburst detected in X-rays. Through CCD time-series photometry, we found the presence of a periodic variation with an amplitude of 0.055 mag and a period of 0.17078 ± 0.00004 d, which we consider to be a promising candidate of the orbital period. Because of the high galactic latitude and faint quiescence magnitude of 18.8, XTE J1118+480 is possibly the first firmly identified black hole candidate X-ray transient in the galactic halo.
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Publications of the Astronomical Society of Japan 52 429-436 2000年6月 査読有りAbstract V-band high-speed CCD photometry of V 1028 Cyg revealed that hump structures existed in the early stage of its 1995 July outburst. We obtained 0.06154 (± 0.00002) d as the best estimated period of superhumps. We confirmed that this dwarf nova belongs to the SU UMa stars. A re-brightening occurred after the superoutburst, and may be associated with a normal outburst. An analysis of the timings of superhump maxima showed clear evidence for an increase of the superhump period (Pdot = Ṗ/P) with 7.54 × 10−6. Only a few stars (AL Com, T Leo, SW UMa, etc.) are reported to have such an increase of the superhump period. At the end of the superoutburst, we detected that the amplitude of the superhumps increased considerably. Both of these properties are not typical features of ordinary SU UMa stars. The connection between the WZ Sge-type and the SU UMa-type dwarf novae is briefly discussed.
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Astrophysical Journal Letters 534 L189-L192 2000年5月 査読有り
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Astronomy and Astrophysics 356 579-584 2000年4月 査読有り筆頭著者We carried out optical spectroscopic observations of the galactic supersoft X-ray source RX J0925.7-4758. The relatively long orbital period among supersoft X-ray sources was confirmed. The nature of the secondary star is discussed using its invisibility in the optical spectrum. Under the hypothesis of a non-eclipsing white dwarf, we derived an A-G giant secondary with an inclination angle of 55deg +/- 10deg. Doppler maps of the He Ii lambda4686 and Hα emission lines were constructed, which generally resemble those of RX J0019.8+2156, suggesting a common line emitting region in supersoft X-ray sources. The concentration of the main emission region to low-velocities indicates that the mass function gives only a lower limit to the mass of the secondary star. Based on observations obtained at ESO La Silla Observatory (ESO Proposal 61.D-0397)....
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Publications of the Astronomical Society of Japan 52 L9-L13 2000年4月 査読有りWe discovered a new deeply eclipsing SU UMa-type dwarf nova, IY UMa, which experienced a superoutburst in 2000 January. Our monitoring revealed two distinct outbursts, which suggest a superoutburst interval of ∼ 800 d, or its half, and an outburst amplitude of 5.4 mag. From time-series photometry during the superoutburst, we determined a superhump and orbital period of 0.07588 d and 0.0739132 d, respectively.
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Astrophysical Journal Letters 528 L97-L100 2000年1月 査読有り
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Star Formation 1999 (Proceedings of Star Formation 1999) 237-238 1999年12月
MISC
1書籍等出版物
5担当経験のある科目(授業)
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2021年 - 現在地学II (大阪教育大学)
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2020年 - 現在実践課題研究 I, II (大阪教育大学)
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2019年 - 現在高度教科内容研究 [天文] (大阪教育大学)
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2012年 - 現在教職実践演習 (大阪教育大学)
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2009年 - 現在理科ゼミナール (大阪教育大学)
共同研究・競争的資金等の研究課題
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日本学術振興会 科学研究費助成事業 基盤研究(C) 2019年4月 - 2024年3月
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日本学術振興会 科学研究費助成事業 研究成果公開促進費 2008年 - 2010年
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日本学術振興会 科学研究費助成事業 特別研究員奨励費 1999年 - 2000年
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日本天文学会 第21回早川幸男基金 1998年
学術貢献活動
9-
企画立案・運営等, パネル司会・セッションチェア等https://quasar.cc.osaka-kyoiku.ac.jp/tenmon-hs/ 2011年 - 現在
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企画立案・運営等http://web.wakayama-u.ac.jp/~atomita/nasejapan2019/ 2019年11月9日 - 2019年11月10日
社会貢献活動
25その他
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2022年9月https://quasar.cc.osaka-kyoiku.ac.jp/~katsura/BL_Lac.html
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2020年4月https://quasar.cc.osaka-kyoiku.ac.jp/~katsura/OJ_287.html
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2017年12月https://quasar.cc.osaka-kyoiku.ac.jp/~katsura/CTA_102.html