Properties of Type Iax Supernova 2019muj in the Late Phase: Existence, Nature and Origin of the Iron-rich Dense Core

Type Iax Supernovae (SNe Iax) form a class of peculiar SNe Ia, whose early-phase spectra share main spectral line identifications with canonical SNe Ia but with higher ionization and much lower line velocities. Their late-time behaviors deviate from usual SNe Ia in many respects; SNe Iax keep showing photospheric spectra over several 100 days and the luminosity decline is very slow. In the present work, we study the late-time spectra of SN Iax 2019muj including a newly-presented spectrum at ~500 days. The spectrum is still dominated by allowed transitions but with lower ionization state, with possible detection of [O I]6300, 6363. By comprehensively examining the spectral formation processes of allowed transitions (Fe II, Fe I, and the Ca II NIR triplet) and forbidden transitions ([Ca II]7292, 7324 and the [O I]), we quantitatively constrain the nature of the innermost region and find that it is distinct from the outer ejecta; the mass of the innermost component is ~0.03 Msun dominated by Fe (which can be initially 56Ni), expanding with the velocity of ~760 km/s. We argue that the nature of the inner component is explained by the failed/weak white-dwarf thermonuclear explosion scenario. We suggest that a fraction of the 56Ni-rich materials initially confined in (the envelope of) the bound remnant can later be ejected by the energy input through the 56Ni/Co/Fe decay, forming the `second' unbound ejecta component which manifests itself as the inner dense component seen in the late phase.Comment: 35 pages, 18 figures. Accepted for publication in Ap

Clearance rate of the cyclopoid copepod Mesocyclops dissimilis on the calanoid copepod Eodiaptomus japonicus

Clearance rate of the planktonic cyclopoid copepod Mesocyclops dissimilis on the planktonic calanoid copepod Eodiaptomus japonicus was measured in laboratory experiments. Ontogenetic changes were investigated using several combinations of different developmental stages of the two species. To minimize the side effects of laboratory experiments, predation was examined for a short duration using field-captured animals at natural prey densities and temperatures. Individual predators showed a large variation in the clearance rate even within replicates of the same experiment. The clearance rates of adult female predators on late naupliar prey were similar (about 0.15 L ind. -1 d-1) within a range of prey density 12-31 ind. L _1. Ontogenetic tendencies in clearance rate, though seldom significant, translated to an increase with development of the predators and a decrease with that of the prey. Present clearance rates and the natural densities of predators and prey suggest that M. dissimilis was sometimes an influential predator of E. japonicus in the field. © The Plankton Society of Japan and The Japanese Association of Benthology

Systematic Investigation of Very Early-Phase Spectra of Type Ia Supernovae

It has been widely accepted that Type Ia supernovae (SNe Ia) are thermonuclear explosions of a CO white dwarf. However, the natures of the progenitor system(s) and explosion mechanism(s) are still unclarified. Thanks to the recent development of transient observations, they are now frequently discovered shortly after the explosion, followed by rapid spectroscopic observations. In this study, by modeling very early-phase spectra of SNe Ia, we try to constrain the explosion models of SNe Ia. By using the Monte Carlo radiation transfer code, TARDIS, we estimate the properties of their outermost ejecta. We find that the photospheric velocity of normal-velocity supernovae (NV SNe) in the first week is $\sim$15000 km s$^{-1}$. The outer velocity, to which the carbon burning extends, spans the range between $\sim$20000 and 25000 km s$^{-1}$. The ejecta density of NV SNe also shows a large diversity. For high-velocity supernovae (HV SNe) and 1999aa-like SNe, the photospheric velocity is higher, $\sim$20000 km s$^{-1}$. They are different in the photospheric density, with HV SNe having higher density than 1999aa-like SNe. For all these types, we show that the outermost composition is closely related to the outermost ejecta density; the carbon burning layer and the unburnt carbon layer are found in the higher-density and lower-density objects, respectively. This finding suggests that there might be two sequences, the high-density and carbon-poor group (HV SNe and some NV SNe) and the low-density and carbon-rich group (1999aa-like and other NV SNe), which may be associated with different progenitor channels.Comment: 22 pages, 11 figures, and 6 tables. Accepted for publication in Ap

フクロワムシの捕食行動

金沢大学教育学部湖沼における主要な無脊椎捕食者であるフクロワムシAsplanchnaの捕食行動を観察することにより、各被食者との食物関係を明らかにし、プランクトン群集におけるその役割について考察した。観察にあたっては、顕微鏡カメラシステムとビデオによる録画を行い、観察時間の延長と観察の再現性を確保した。本研究では、すでに動物プランクトン群集についての知見の蓄積されている河北潟に出現する以下の種を用いた。すなわち捕食者シ-ボルトフクロワムシAsplanchna sieboldiおよび被食者ツボワムシBrachionus calyciflorus、ツノワムシSchizocerca diversicornis、オナガミジンコDiaphanosoma brachyurum、カイアシ類である。捕食行動は以下の段階に分けることができた。まず感知、次いで攻撃もしくは無視、攻撃に次いでは捕獲の成功もしくは不成功、捕獲に次いでは捕食もしくは却下である。フクロワムシは口器に接近した生物を感知し、自身より小さな個体のみを攻撃した。捕獲成功率は、主に被食者の逃避能力に左右された。すなわち、ツボワムシとツノワムシは捕獲されやすく、オナガミジンコがそれに次ぎ、カイアシ類はほとんどの場合逃避した。フクロワムシは、口器を通過するもののほとんどを捕食した。この段階において、ツボワムシのうち側突起を持つ個体はそれを広げることにより捕食を逃れた。これに対して、側突起を持たないツボワムシや、縦長の突起を持つツノワムシは捕食された。以上から、フクロワムシからの捕食回避において、攻撃の段階では全体のサイズを大きくすること、捕獲の段階では逃避すること、捕食の段階では体の長さをいずれの方向にも大きくすることがそれぞれ有効であることが分かった。研究課題/領域番号:05740463, 研究期間(年度):1993出典：研究課題「フクロワムシの捕食行動」課題番号05740463（KAKEN：科学研究費助成事業データベース（国立情報学研究所）） （https://kaken.nii.ac.jp/ja/grant/KAKENHI-PROJECT-05740463/）を加工して作

ツボワムシの捕食回避反応:野外における側突起形成の観察とその有効性の評価

金沢大学教育学部研究課題/領域番号:04740356, 研究期間(年度):1992出典：研究課題「ツボワムシの捕食回避反応:野外における側突起形成の観察とその有効性の評価」課題番号04740356（KAKEN：科学研究費助成事業データベース（国立情報学研究所）） （https://kaken.nii.ac.jp/ja/grant/KAKENHI-PROJECT-04740356/）を加工して作

The evolution of the peculiar Type Ia supernova SN 2005hk over 400 days

$UBVRI$ photometry and medium resolution optical spectroscopy of peculiar Type Ia supernova SN 2005hk are presented and analysed, covering the pre-maximum phase to around 400 days after explosion. The supernova is found to be underluminous compared to "normal" Type Ia supernovae. The photometric and spectroscopic evolution of SN 2005hk is remarkably similar to the peculiar Type Ia event SN 2002cx. The expansion velocity of the supernova ejecta is found to be lower than normal Type Ia events. The spectra obtained \gsim 200 days since explosion do not show the presence of forbidden [\ion{Fe}{ii}], [\ion{Fe}{iii}] and [\ion{Co}{iii}] lines, but are dominated by narrow, permitted \ion{Fe}{ii}, NIR \ion{Ca}{ii} and \ion{Na}{i} lines with P-Cygni profiles. Thermonuclear explosion model with Chandrasekhar mass ejecta and a kinetic energy smaller (\KE = 0.3 \times 10^{51} {\rm ergs}) than that of canonical Type Ia supernovae is found to well explain the observed bolometric light curve. The mass of \Nifs synthesized in this explosion is 0.18 \Msun. The early spectra are successfully modeled with this less energetic model with some modifications of the abundance distribution. The late spectrum is explained as a combination of a photospheric component and a nebular component.Comment: Accepted for publication in The Astrophysical Journal. Minor revision, discussion section adde

Grazing and food size selection of zooplankton community in Lake Biwa during BITEX \u2793

金沢大学教育学部理科教育Community grazing rate of zooplankton larger than 98 μm in body size were examined at the north and south basins of Lake Biwa in late summer, 1993. The lake seston labeled with 14C was divided into different size fraction (20 μm, however, the largest size fraction contributed 57% of the ingested carbon, suggesting that the food source of zooplankton is not necessarily restricted to the small sestonic particles, even if feeding efficiency was low for large sestonic particles. Based on grazing rate, 6 to 10% of total seston was estimated to be removed by the zooplankton community within a day

Optical Spectropolarimetry and Asphericity of Type Ic SN 2007gr

We present optical spectropolarimetric observations of Type Ic supernova (SN) 2007gr with Subaru telescope at 21 days after the maximum brightness (~37 days after the explosion). Non-zero polarization as high as ~3% is observed at the absorption feature of Ca II IR triplet. The polarization of the continuum light is ~0.5% if we estimate the interstellar polarization (ISP) component assuming that the continuum polarization has a single polarization angle. This suggests that the axis ratio of the SN photosphere projected to the sky is different from unity by ~10%. The polarization angle at the Ca II absorption is almost aligned to that of the continuum light. These features may be understood by the model where a bipolar explosion with an oblate photosphere is viewed from the slightly off-axis direction and explosively synthesized Ca near the polar region obscures the light originated around the minor axis of the SN photosphere. Given the uncertainty of the ISP, however, the polarization data could also be interpreted by the model with an almost spherically symmetric photosphere and a clumpy Ca II distribution.Comment: 9 pages, 8 figures, Accepted for publication in the Astrophysical Journa