arXiv subjects

Kouji Ohta

Publications and source records attributed to Kouji Ohta.

At least 73 records · Page 4Linked to original sources

arXiv2014

The Redshift and Metallicity of the Host Galaxy of Dark GRB 080325 at z=1.78

We present near-infrared spectroscopy of the host galaxy of dark GRB 080325 using Subaru/MOIRCS. The obtained spectrum provides a clear detection of H$α$ emission and marginal [NII]$λ$6584. The host is a massive (M$_{*}\sim10^{11}$M$_{\odot}$), dusty ($A_{V}\sim 1.2$) star-forming galaxy at z=1.78. The star formation rate calculated from the H$α$ luminosity (35.6-47.0 M$_{\odot}$ yr$^{-1}$) is typical among GRB host galaxies (and star-forming galaxies generally) at z $>$1; however, the specific star formation rate is lower than normal star-forming galaxies at redshift $\sim$ 1.6, in contrast to the high specific star formation rates measured for many of other GRB hosts. The metallicity of the host is estimated to be 12+log(O/H)$_{\rm KK04}$$=$8.88. We emphasize that this is one of the most massive distant host galaxies for which metallcity is measured with emission-line diagnostics. The metallicity is fairly high among GRB hosts. However, this is still lower than the metallicity of normal star-forming galaxies of the same mass at z$\sim$1.6. The metallicity offset from normal star-forming galaxies is close to a typical value of other GRB hosts and indicates that GRB host galaxies are uniformly biased toward low metalicity over a wide range of redshift and stellar mass. The low-metallicity nature of the GRB 080325 host is likely not attributable to the fundamental metallicity relation of star-forming galaxies beacuse it is a metal-poor outlier from the relation and has a low sSFR. Thus we conclude that metallicity is important to the mechanism that produced this GRB.

astro-ph.GA↗

arXiv2014

The gas inflow and outflow rate in star-forming galaxies at $z\sim1.4$

We try to constrain the gas inflow and outflow rate of star-forming galaxies at $z\sim1.4$ by employing a simple analytic model for the chemical evolution of galaxies. The sample is constructed based on a large near-infrared (NIR) spectroscopic sample observed with Subaru/FMOS. The gas-phase metallicity is measured from the [\ion{N}{2}]$λ$6584/H$α$ emission line ratio and the gas mass is derived from the extinction corrected H$α$ luminosity by assuming the Kennicutt-Schmidt law. We constrain the inflow and outflow rate from the least-$χ^{2}$ fittings of the observed gas mass fraction, stellar mass, and metallicity with the analytic model. The joint $χ^{2}$ fitting shows the best-fit inflow rate is $\sim1.8$ and the outflow rate is $\sim0.6$ in unit of star-formation rate (SFR). By applying the same analysis to the previous studies at $z\sim0$ and $z\sim2.2$, it is shown that the both inflow rate and outflow rate decrease with decreasing redshift, which implies the higher activity of gas flow process at higher redshift. The decreasing trend of the inflow rate from $z\sim2.2$ to $z\sim0$ agrees with that seen in the previous observational works with different methods, though the absolute value is generally larger than the previous works. The outflow rate and its evolution from $z\sim2.2$ to $z\sim0$ obtained in this work agree well with the independent estimations in the previous observational works.

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arXiv2014

FIELD: An automated emission-line detection software for Subaru/FMOS near-infrared spectroscopy

We describe the development of automated emission line detection software for the Fiber Multi-Object Spectrograph (FMOS), which is a near-infrared spectrograph fed by $400$ fibers from the $0.2$ deg$^2$ prime focus field of view of the Subaru Telescope. The software, FIELD (FMOS software for Image-based Emission Line Detection), is developed and tested mainly for the FastSound survey, which is targeting H$α$ emitting galaxies at $z \sim 1.3$ to measure the redshift space distortion as a test of general relativity beyond $z \sim 1$. The basic algorithm is to calculate the line signal-to-noise ratio ($S/N$) along the wavelength direction, given by a 2-D convolution of the spectral image and a detection kernel representing a typical emission line profile. A unique feature of FMOS is its use of OH airglow suppression masks, requiring the use of flat-field images to suppress noise around the mask regions. Bad pixels on the detectors and pixels affected by cosmic-rays are efficiently removed by using the information obtained from the FMOS analysis pipeline. We limit the range of acceptable line-shape parameters for the detected candidates to further improve the reliability of line detection. The final performance of line detection is tested using a subset of the FastSound data; the false detection rate of spurious objects is examined by using inverted frames obtained by exchanging object and sky frames. The false detection rate is $< 1$\% at $S/N > 5$, allowing an efficient and objective emission line search for FMOS data at the line flux level of $\gtrsim 1.0 \times 10^{-16}$[erg/cm$^2$/s].

astro-ph.IM↗

arXiv2014

Multi-band, Multi-epoch Observations of the Transiting Warm Jupiter WASP-80b

WASP-80b is a warm Jupiter transiting a bright late-K/early-M dwarf, providing a good opportunity to extend the atmospheric study of hot Jupiters toward the lower temperature regime. We report multi-band, multi-epoch transit observations of WASP-80b by using three ground-based telescopes covering from optical (g', Rc, and Ic bands) to near-infrared (NIR; J, H, and Ks bands) wavelengths. We observe 5 primary transits, each of which in 3 or 4 different bands simultaneously, obtaining 17 independent transit light curves. Combining them with results from previous works, we find that the observed transmission spectrum is largely consistent with both a solar abundance and thick cloud atmospheric models at 1.7$σ$ discrepancy level. On the other hand, we find a marginal spectral rise in optical region compared to the NIR region at 2.9$σ$ level, which possibly indicates the existence of haze in the atmosphere. We simulate theoretical transmission spectra for a solar abundance but hazy atmosphere, finding that a model with equilibrium temperature of 600 K can explain the observed data well, having a discrepancy level of 1.0$σ$. We also search for transit timing variations, but find no timing excess larger than 50 s from a linear ephemeris. In addition, we conduct 43 day long photometric monitoring of the host star in the optical bands, finding no significant variation in the stellar brightness. Combined with the fact that no spot-crossing event is observed in the five transits, our results confirm previous findings that the host star appears quiet for spot activities, despite the indications of strong chromospheric activities.

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arXiv2014

ALMA Observation of 158 micron [CII] Line and Dust Continuum of a z=7 Normally Star-forming Galaxy in the Epoch of Reionization

We present ALMA observations of the [CII] line and far-infrared (FIR) continuum of a normally star-forming galaxy in the reionization epoch, the z=6.96 Ly-alpha emitter (LAE) IOK-1. Probing to sensitivities of sigma_line = 240 micro-Jy/beam (40 km/s channel) and sigma_cont = 21 micro-Jy/beam, we found the galaxy undetected in both [CII] and continuum. Comparison of UV - FIR spectral energy distribution (SED) of IOK-1, including our ALMA limit, with those of several types of local galaxies (including the effects of the cosmic microwave background, CMB, on the FIR continuum) suggests that IOK-1 is similar to local dwarf/irregular galaxies in SED shape rather than highly dusty/obscured galaxies. Moreover, our 3 sigma FIR continuum limit, corrected for CMB effects, implies intrinsic dust mass M_dust < 6.4 x 10^7 M_sun, FIR luminosity L_FIR < 3.7 x 10^{10} L_sun (42.5 - 122.5 micron), total IR luminosity L_IR < 5.7 x 10^{10} L_sun (8 - 1000 micron) and dust-obscured star formation rate (SFR) < 10 M_sun/yr, if we assume that IOK-1 has a dust temperature and emissivity index typical of local dwarf galaxies. This SFR is 2.4 times lower than one estimated from the UV continuum, suggesting that < 29% of the star formation is obscured by dust. Meanwhile, our 3 sigma [CII] flux limit translates into [CII] luminosity, L_[CII] < 3.4 x 10^7 L_sun. Locations of IOK-1 and previously observed LAEs on the L_[CII] vs. SFR and L_[CII]/L_FIR vs. L_FIR diagrams imply that LAEs in the reionization epoch have significantly lower gas and dust enrichment than AGN-powered systems and starbursts at similar/lower redshifts, as well as local star-forming galaxies.

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arXiv2014

Constraint on the Gas-to-Dust Ratio in Massive Star-Forming Galaxies at z~1.4

We carried out 12CO(J=2-1) observations toward three star-forming galaxies on the main sequence at z~1.4 with the Nobeyama 45m radio telescope. These galaxies are detected with Spitzer/MIPS in 24 um, Herschel/SPIRE in 250 um and 350 um, and their gas metallicity, derived from optical emission line ratios based on near infrared spectroscopic observations, is close to the solar metallicity. Although weak signal-like features of CO were seen, we could not detect significant CO emission. The dust mass and the upper limits on the molecular gas mass are (3.4-6.7) x 10^{8} Msun and (9.7-14) x 10^{10} Msun, respectively. The upper limits on the gas-to-dust ratios at z~1.4 are 150-410 which are comparable to the gas-to-dust ratios in local galaxies with similar gas metallicity. A line stacking analysis enables us to detect a significant CO emission and to derive an average molecular gas mass of 1.3 x 10^{11} Msun and gas-to-dust ratio of 250. This gas-to-dust ratio is also near that in local galaxies with solar metallicity. These results suggest that the gas-to-dust ratio in star-forming galaxies with solar metallicity does not evolve significantly up to z~1.4. By comparing to a theoretical calculation, a rapid increase of the dust mass in an earlier epoch of galaxy evolution is suggested.

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arXiv2014

Outbursting Comet P/2010 V1 (Ikeya-Murakami): A Miniature Comet Holmes

Short-period comet P/2010 V1 (Ikeya-Murakami, hereafter V1) was discovered visually by two amateur astronomers. The appearance of the comet was peculiar, consisting of an envelope, a spherical coma near the nucleus and a tail extending in the anti-solar direction. We investigated the brightness and the morphological development of the comet by taking optical images with ground-based telescopes. Our observations show that V1 experienced a large-scale explosion between UT 2010 October 31 and November 3. The color of the comet was consistent with the Sun (g'-RC=0.61+-0.20, RC-IC=0.20+-0.20, and B-RC=0.93+-0.25), suggesting that dust particles were responsible for the brightening. We used a dynamical model to understand the peculiar morphology, and found that the envelope consisted of small grains (0.3-1 micron) expanding at a maximum speed of 500+-40 m/s, while the tail and coma were composed of a wider range of dust particle sizes (0.4-570 micron) and expansion speeds 7-390 m/s. The total mass of ejecta is ~5x10^8 kg and kinetic energy ~5x10^12 J. These values are much smaller than in the historic outburst of 17P/Holmes in 2007, but the energy per unit mass (1x10^4 J/kg) is comparable. The energy per unit mass is about 10% of the energy released during the crystallization of amorphous water ice suggesting that crystallization of buried amorphous ice can supply the mass and energy of the outburst ejecta.

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arXiv2014

Probing Intergalactic Neutral Hydrogen by the Lyman Alpha Red Damping Wing of Gamma-Ray Burst 130606A Afterglow Spectrum at z = 5.913

The unprecedentedly bright optical afterglow of GRB 130606A located by Swift at a redshift close to the reionization era (z = 5.913) provides a new opportunity to probe the ionization status of intergalactic medium (IGM). Here we present an analysis of the red Ly alpha damping wing of the afterglow spectrum taken by Subaru/FOCAS during 10.4-13.2 hr after the burst. We find that the minimal model including only the baseline power-law and HI absorption in the host galaxy does not give a good fit, leaving residuals showing concave curvature in 8400-8900 A with an amplitude of about 0.6% of the flux. Such a curvature in the short wavelength range cannot be explained either by extinction at the host with standard extinction curves, intrinsic curvature of afterglow spectra, or by the known systematic uncertainties in the observed spectrum. The red damping wing by intervening HI gas outside the host can reduce the residual by about 3 sigma statistical significance. We find that a damped Ly alpha system is not favored as the origin of this intervening HI absorption, from the observed Ly beta and metal absorption features. Therefore absorption by diffuse IGM remains as a plausible explanation. A fit by a simple uniform IGM model requires HI neutral fraction of f_HI ~ 0.1-0.5 depending on the distance to the GRB host, implying high f_HI IGM associated with the observed dark Gunn-Peterson (GP) troughs. This gives a new evidence that the reionization is not yet complete at z ~ 6.

astro-ph.HE↗

arXiv2013

The mass-metallicity relation at z~1.4 revealed with Subaru/FMOS

We present a stellar mass-metallicity relation at z~1.4 with an unprecedentedly large sample of ~340 star-forming galaxies obtained with FMOS on the Subaru Telescope. We observed K-band selected galaxies at 1.2 < z_{ph} < 1.6 in the SXDS/UDS fields with M_{*} > 10^{9.5} M_{\sun}, and expected F(Hα) > 5 \times 10^{-17} erg s^{-1} cm^{-2}. Among the observed ~1200 targets, 343 objects show significant Hαemission lines. The gas-phase metallicity is obtained from [NII]λ6584/Hαline ratio, after excluding possible active galactic nuclei (AGNs). Due to the faintness of the [NII]λ6584 lines, we apply the stacking analysis and derive the mass-metallicity relation at z~1.4. Our results are compared to past results at different redshifts in the literature. The mass-metallicity relation at z~1.4 is located between those at z~0.8 and z~2.2; it is found that the metallicity increases with decreasing redshift from z~3 to z~0 at fixed stellar mass. Thanks to the large size of the sample, we can study the dependence of the mass-metallicity relation on various galaxy physical properties. The average metallicity from the stacked spectra is close to the local FMR in the higher metallicity part but >0.1 dex higher in metallicity than the FMR in the lower metallicity part. We find that galaxies with larger E(B-V), B-R, and R-H colours tend to show higher metallicity by ~0.05 dex at fixed stellar mass. We also find relatively clearer size dependence that objects with smaller half light radius tend to show higher metallicity by ~0.1 dex at fixed stellar mass, especially in the low mass part.

astro-ph.CO↗

arXiv2013

The Cosmic BPT Diagram: Confronting Theory with Observations

We compare a large sample of galaxies between 0.5 1.5) are consistent with a model in which the ISM conditions are more extreme at high redshift than seen in the global spectra of local galaxies. We speculate that global spectra of our high redshift galaxies may be dominated by HII regions similar to the extreme clumpy, dense star-forming complexes in the Antennae and M82. The transition to local-type conditions occurs between 0.8 1.5). We use our theoretical models to derive a new redshift-dependent classification line that utilizes the standard optical diagnostic line ratios [OIII]/H-beta and [NII]/H-alpha. Our new line can be used to separate star-forming galaxies from AGN between z=0 to z~3.5. We anticipate that our redshift-dependent optical classification line will be useful for future large surveys with near-infrared multi-object spectrographs. We apply our classification line to a sample of gravitationally lensed galaxies at z~2.5. Although limited by small numbers, we show that our classification line is consistent with the position of AGN that have been independently confirmed via other methods.

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arXiv2013

Optical-to-Near-Infrared Simultaneous Observations for the Hot Uranus GJ3470b: A Hint for Cloud-free Atmosphere

We present optical (g', R_c, and I_c) to near-infrared (J) simultaneous photometric observations for a primary transit of GJ3470b, a Uranus-mass transiting planet around a nearby M dwarf, by using the 50-cm MITSuME telescope and the 188-cm telescope, both at Okayama Astrophysical Observatory. From these data, we derive the planetary mass, radius, and density as 14.1 \pm 1.3 M_earth, 4.32^{+0.21}_{-0.10} R_earth, and 0.94 \pm 0.12 g cm^{-3}, respectively, thus confirming the low density that was reported by Demory et al. based on the Spitzer/IRAC 4.5-micron photometry (0.72^{+0.13}_{-0.12} g cm^{-3}). Although the planetary radius is about 10% smaller than that reported by Demory et al., this difference does not alter their conclusion that the planet possesses a hydrogen-rich envelope whose mass is approximately 10% of the planetary total mass. On the other hand, we find that the planet-to-star radius ratio (R_p/R_s) in the J band (0.07577^{+0.00072}_{-0.00075}) is smaller than that in the I_c (0.0802 \pm 0.0013) and 4.5-micron (0.07806^{+0.00052}_{-0.00054}) bands by 5.9% \pm 2.0% and 3.0% \pm 1.2%, respectively. A plausible explanation for the differences is that the planetary atmospheric opacity varies with wavelength due to absorption and/or scattering by atmospheric molecules. Although the significance of the observed R_p/R_s variations is low, if confirmed, this fact would suggest that GJ3470b does not have a thick cloud layer in the atmosphere. This property would offer a wealth of opportunity for future transmission-spectroscopic observations of this planet to search for certain molecular features, such as H2O, CH4, and CO, without being prevented by clouds.

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arXiv2013

Faint End of 1.3 mm Number Counts Revealed by ALMA

We present the faint end of number counts at 1.3 mm (238 GHz) obtained with the Atacama Large Millimeter/submillimeter Array (ALMA). Band 6 observations were carried out targeting 20 star-forming galaxies at z ~ 1.4 in the Subaru/XMM-Newton Deep Survey field. In the observations, we serendipitously detect 15 sources (>=3.8 sigma, S(1.3 mm) = 0.15-0.61 mJy) other than the targeted sources. We create number counts by using these `sub-mJy sources', which probe the faintest flux range among surveys at millimeter wavelengths. The number counts are consistent with (flux-scaled) number counts at 850 um and 870 um obtained with gravitational lensing clusters. The ALMA number counts agree well with model predictions, which suggest that these sub-mJy populations are more like `normal' star-forming galaxies than `classical' SMGs with intense star-forming activity. In this flux range, ~80% of the extragalactic background light at 1.3 mm is resolved into individual sources.

astro-ph.CO↗

arXiv2013

A comparative analysis of virial black-hole mass estimates of moderate-luminosity active galactic nuclei using Subaru/FMOS

We present an analysis of broad emission lines observed in moderate-luminosity active galactic nuclei (AGNs), typical of those found in X-ray surveys of deep fields, with the aim to test the validity of single-epoch virial black hole mass estimates. We have acquired near-infrared (NIR) spectra of AGNs up to z ~ 1.8 in the COSMOS and Extended Chandra Deep Field-South Survey, with the Fiber Multi-Object Spectrograph (FMOS) mounted on the Subaru Telescope. These low-resolution NIR spectra provide a significant detection of the broad Halpha line that has been shown to be a reliable probe of black hole mass at low redshift. Our sample has existing optical spectroscopy which provides a detection of MgII, a broad emission line typically used for black hole mass estimation at z > 1. We carry out a spectral-line fitting procedure using both Halpha and MgII to determine the virial velocity of gas in the broad line region, the monochromatic continuum luminosity at 3000 A, and the total Halpha line luminosity. With a sample of 43 AGNs spanning a range of two decades in luminosity (i.e., L ~ 10^44-46 ergs/s), we find a tight correlation between the continuum and line luminosity with a distribution characterized by = 1.52 and a dispersion sigma = 0.16. There is also a close one-to-one relationship between the FWHM of Halpha and of MgII up to 10000 km/s with a dispersion of 0.14 in the distribution of the logarithm of their ratios. Both of these then lead to there being very good agreement between Halpha- and MgII-based masses over a wide range in black hole mass (i.e., M_BH ~ 10^7-9 M_sun). We do find a small offset in MgII-based masses, relative to those based on Halpha, of +0.17 dex and a dispersion sigma = 0.32. In general, these results demonstrate that local scaling relations, using MgII or Halpha, are applicable for AGN at moderate luminosities and up to z ~ 2.

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arXiv2012

Intrinsic Shape of Star-Forming BzK Galaxies II: Rest-Frame UV and Optical Structures in GOODS-South and SXDS

(Abridge) We study statistical intrinsic shape of star-forming BzK galaxies (sBzK galaxies) at z~2 in both rest-frame UV and rest-frame optical wavelengths. The sBzK galaxies are selected down to K(AB)=24.0 mag in the GOODS-South and SXDS fields, where high-resolution images from Hubble Space Telescope are publicly available. 57% (583) of all 1028 galaxies in GOODS-S show a single component in the ACS/F850LP image. As WFC3/F160W images cover only some part of GOODS-S and SXDS, 724/1028 and 2500/29835 sBzK galaxies in the GOODS-S and SXDS have the WFC3 coverage. 86% (626) and 82% (2044) of the sBzK galaxies in WFC3/F160W images appear as a single component in the GOODS-S and SXDS, respectively. Larger fraction of single-component objects in F850LP images represents multiple star-forming regions in galaxies, while they are not so obvious in the F160W image which appears smoother. Most of the single-component sBzK galaxies show Sérsic indices of n=0.5-2.5, in agreement with those of local disk galaxies. Their effective radii are 1.0-3.0 kpc and 1.5-4.0 kpc in F850LP and F160W images, respectively, regardless of the observed fields. Stellar surface mass density of the sBzK galaxies is also comparable to that of the local disk galaxies. However, the intrinsic shape of sBzK galaxies is not a round disk as seen in the local disk galaxies. By comparing apparent axial ratio (b/a) distributions of the sBzK galaxies with those by assuming tri-axial model with axes A>B>C, we found their intrinsic face-on B/A ratios peak at B/A=0.70 and B/A=0.77-0.79 in the rest-frame UV and optical, respectively and are statistically more bar-like than that of the local disk galaxies. The intrinsic edge-on C/A ratios in both rest-frame UV and optical wavelengths peak at 0.26, which is slightly larger than that of the local disk galaxies.

astro-ph.CO↗

arXiv2012

Constraints on Obscured Star Formation in Host Galaxies of Gamma-ray Bursts

We present the results of the 16-cm-waveband continuum observations of four host galaxies of gamma-ray bursts (GRBs) 990705, 021211, 041006, and 051022 using the Australia Telescope Compact Array. Radio emission was not detected in any of the host galaxies. The 2sigma upper limits on star-formation rates derived from the radio observations of the host galaxies are 23, 45, 27, and 26 Msun/yr, respectively, which are less than about 10 times those derived from UV/optical observations, suggesting that they have no significant dust-obscured star formation. GRBs 021211 and 051022 are known as the so-called "dark GRBs" and our results imply that dark GRBs do not always occur in galaxies enshrouded by dust. Because large dust extinction was not observed in the afterglow of GRB021211, our result {\bf suggests the possibility} that the cause of the dark GRB is the intrinsic faintness of the optical afterglow. On the other hand, by considering the high column density observed in the afterglow of GRB051022, the likely cause of the dark GRB is the dust extinction in the line of sight of the GRB.

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arXiv2011

NIR Spectroscopy of Star-Forming Galaxies at z~1.4 with Subaru/FMOS: The Mass-Metallicity Relation

We present near-infrared spectroscopic observations of star-forming galaxies at z~1.4 with FMOS on the Subaru Telescope. We observed K-band selected galaxies in the SXDS/UDS fields with K<23.9 mag, 1.2 10^{9.5} Msun, and expected F(Halpha)>10^{-16} erg s^{-1} cm^{-2}. 71 objects in the sample have significant detections of Halpha. For these objects, excluding possible AGNs identified from the BPT diagram, gas-phase metallicities are obtained from [NII]/Halpha line ratio. The sample is split into three stellar mass bins, and the spectra are stacked in each stellar mass bin. The mass-metallicity relation obtained at z~1.4 is located between those at z~0.8 and z~2.2. We constrain an intrinsic scatter to be ~0.1 dex or larger in the mass-metallicity relation at z~1.4; the scatter may be larger at higher redshifts. We found trends that the deviation from the mass-metallicity relation depends on the SFR and the half light radius: Galaxies with higher SFR and larger half light radii show lower metallicities at a given stellar mass. One possible scenario for the trends is the infall of pristine gas accreted from IGM or through merger events. Our data points show larger scatter than the fundamental metallicity relation (FMR) at z~0.1 and the average metallicities slightly deviate from the FMR. The compilation of the mass-metallicity relations at z~3 to z~0.1 shows that they evolve smoothly from z~3 to z~0 without changing the shape so much except for the massive part at z~0.

astro-ph.CO↗

arXiv2011

Interpretation of (596) Scheila's Triple Dust Tails

Strange-looking dust cloud around asteroid (596) Scheila was discovered on 2010 December 11.44-11.47. Unlike normal cometary tails, it consisted of three tails and faded within two months. We constructed a model to reproduce the morphology of the dust cloud based on the laboratory measurement of high velocity impacts and the dust dynamics. As the result, we succeeded in the reproduction of peculiar dust cloud by an impact-driven ejecta plume consisting of an impact cone and downrange plume. Assuming an impact angle of 45 deg, our model suggests that a decameter-sized asteroid collided with (596) Scheila from the direction of (alpha, delta) = (60deg, -40deg) in J2000 coordinates on 2010 December 3. The maximum ejection velocity of the dust particles exceeded 100 m/s. Our results suggest that the surface of (596) Scheila consists of materials with low tensile strength.

astro-ph.EP↗

arXiv2011

Photometric Observations of 107P/Wilson-Harrington

We present lightcurve observations and multiband photometry for 107P/Wilson-Harrington using five small- and medium-sized telescopes. The lightcurve has shown a periodicity of 0.2979 day (7.15 hour) and 0.0993 day (2.38 hour), which has a commensurability of 3:1. The physical properties of the lightcurve indicate two models: (1) 107P/Wilson-Harrington is a tumbling object with a sidereal rotation period of 0.2979 day and a precession period of 0.0993 day. The shape has a long axis mode (LAM) of L1:L2:L3 = 1.0:1.0:1.6. The direction of the total rotational angular momentum is around λ = 310°, β = -10°, or λ = 132°, β = -17°. The nutation angle is approximately constant at 65°. (2) 107P/Wilson-Harrington is not a tumbler. The sidereal rotation period is 0.2979 day. The shape is nearly spherical but slightly hexagonal with a short axis mode (SAM) of L1:L2:L3 = 1.5:1.5:1.0. The pole orientation is around λ = 330°, β = -27°. In addition, the model includes the possibility of binary hosting. For both models, the sense of rotation is retrograde. Furthermore, multiband photometry indicates that the taxonomy class of 107P/Wilson-Harrington is C-type. No clear rotational color variations are confirmed on the surface.

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