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The formation of massive stars in dense and cold molecular clouds is a fundamental problem in star formation. In this work, we studied three compact massive star-forming regions, M8E, RAFGL 6366S, and IRAS 18317−0513, to investigate the environment of massive star formation, specifically the possibility of a local feedback process. Our new mid-infrared observations using miniTAO/MAX38 at 31 and 37 μm resolved individual objects in each region and allowed us to obtain their individual luminosities and masses. Together with existence/absence of ultra-compact H  ii regions, it is suggested that less-massive objects are more evolved than the more-massive objects in two out of the three regions. Because the objects that are more massive evolve faster, those that are less massive form earlier. This formation trend of local mass-sequential star was first suggested in 0.1 pc-scale massive star-forming regions. Therefore, feedback, such as outflows, jets, or radiative heating, from previously formed lower-mass young stellar objects might affect the environment of parental clouds and lead to next-generation massive young stellar objects. [ABSTRACT FROM AUTHOR]

The goal of this paper is to characterize the light variation properties of Mira variables in the Small Magellanic Cloud. We have investigated a combined optical and near-infrared multi-epoch data set of Mira variables based on our monitoring data obtained over 15 yr. Bolometric correction relations are formulated for various near-infrared colours. We find that the same bolometric correction equation holds for both the bolometricly brightest and faintest pulsation phases. Period–bolometric magnitude relations and period–colour relations were derived using time-averaged values. Phase lags between bolometric phase and optical and near-infrared phases were detected from the O-rich (the surface C/O number ratio is below unity) Mira variables, while no significant systematic lags were observed in most of the C-rich (the C/O ratio is over unity) ones. Some Miras show colour phase inversions, e.g. H – K s at its bluest while J – H and J – K s are at their reddest values at about the bolometricly brightest phase. Their occurrence conditions were studied but no clear direct or indirect trigger was found. A large NIR colour change unassociated with stellar pulsation was observed in Miras with long secondary periods, and its possible explanation is described. [ABSTRACT FROM AUTHOR]

A very long-term near-infrared variable star survey towards the Large and Small Magellanic Clouds (LMC and SMC) was carried out using the 1.4 m InfraRed Survey Facility at the South African Astronomical Observatory. This project was initiated in 2000 December in the LMC, and in 2001 July in the SMC. Since then an area of 3 deg2along the bar in the LMC and an area of 1 deg2in the central part of the SMC have been repeatedly observed. This survey is ongoing, but results obtained with data taken until 2017 December are reported in this paper. Over more than 15 yr we have observed the two survey areas more than one hundred times. This is the first survey that provides near-infrared time-series data with such a long time baseline and on such a large scale. This paper describes the observations in the SMC and publishes a point source photometric catalogue, a variable source catalogue, and time-series data. [ABSTRACT FROM AUTHOR]

The data of 8852 and 2927 variable stars detected by the OGLE survey in the Large and Small Magellanic Clouds are presented. They are cross-identified with the SIRIUSJHKsurvey data, and their infrared properties are discussed. Variable red giants are well separated on the period–plane, suggesting that it could be a good tool to distinguish their pulsation mode and type. [ABSTRACT FROM AUTHOR]

Abstract The first results of a study of the dwarf spheroidal galaxy Leo I using the new Nagoya–South African Infrared Survey Facility (IRSF) are presented. J, H and K[sub s] observations show that most, if not all, of at least the top magnitude of the asymptotic giant branch (AGB) in K[sub s] is populated by carbon stars. In addition there are five very red objects which are believed to be dust-enshrouded AGB stars. One of these is, remarkably, well outside the main body of the galaxy. Three of these obscured stars and five known carbon stars show variability in observations 11 months apart. One of the obscured stars has ΔK[sub s]= 0.87 , making it highly likely that it, at least, is a Mira variable. The tip of the AGB is at M[sub bol]∼-5.1 , but further variability studies are necessary to obtain a definitive value. Comparison with carbon stars, both Miras and non-Miras, in Magellanic Cloud clusters, and taking into account other evidence on the ages and metallicities of Leo I populations, suggests that these obscured stars belong to the youngest significant population of Leo I and have ages of ∼2 Gyr. [ABSTRACT FROM AUTHOR]

We have developed a near-infrared camera called ANIR (Atacama Near-InfraRed camera) for the University of Tokyo Atacama Observatory 1.0 m telescope (miniTAO) installed at the summit of Cerro Chajnantor (5640 m above sea level) in the north of Chile. The camera provides a field of view of 5${^{\prime}_{.}}$1 × 5${^{\prime}_{.}}$1 with a spatial resolution of 0${^{\prime\prime}_{.}}$298 pixel−1 in the wavelength range of 0.95 to 2.4 μm, using Offner relay optics and a PACE HAWAII-2 focal plane array. Taking advantage of the dry site, the camera is capable of narrow-band imaging observations at the hydrogen Paschen-α (Paα, λ = 1.8751 μm in air) wavelength ground-based observations of which have been quite difficult due to deep atmospheric absorption, mainly from water vapor. We have been successfully obtaining Paα images of Galactic objects and nearby galaxies since the first-light observation in 2009 with ANIR. The throughputs at the narrow-band filters (N1875, N191) including the atmospheric absorption show larger dispersion (∼ 10%) than those at broad-band filters (a few percent), indicating that they are affected by temporal fluctuations in precipitable water vapor (PWV) above the site. We evaluate the PWV content via the atmospheric transmittance at the narrow-band filters, and deduce that the median and the dispersion of the distribution of the PWV are 0.40 ± 0.30 and 0.37 ± 0.21 mm, for the N1875 and N191 data respectively, which are remarkably smaller (49% ± 38% for N1875 and 59% ± 26% for N191) than radiometry measurements at the base of Cerro Chajnantor (an altitude of 5100 m). The decrease in PWV can be explained by the altitude of the site when we assume that the vertical distribution of the water vapor is approximated at an exponential profile with scale heights within 0.3–1.9 km (previously observed values at night). We thus conclude that miniTAO/ANIR at the summit of Cerro Chajnantor indeed provides us an excellent capability for a ground-based Paα observation. [ABSTRACT FROM PUBLISHER]

Brown dwarfs (hereafter BDs) are of particular interest because of their extremely low-temperature atmospheres for comparison with atmospheres of giant planets. Aiming to obtain clues to understand the formation and disappearance of dust clouds and molecular abundances in BD photospheres, we conducted an observation programme of space-borne near-infrared spectroscopy of bright BDs with the Infrared Camera (IRC) on-board AKARI. [ABSTRACT FROM PUBLISHER]

We derive photometric metallicities for 56 intermediate-age and old star clusters in the Large Magellanic Cloud from the slopes of their red-giant branches in near-infrared color–magnitude diagrams (CMDs). The cluster sample covers the LMC bar and disk to a distance of ~2 kpc from the LMC center. The derived cluster metallicity distribution spans a range of [Fe/H] = +0.0 . . . 1.4 and is similar to the metallicity distribution of field stars. We find that the average cluster metallicities in certain fields of the LMC bar and disk may be different, but there seems to be no compelling evidence for a global cluster metallicity gradient in the LMC. [ABSTRACT FROM PUBLISHER]

The first results of our ongoing near-infrared (NIR) survey of the variable red giants in the Large Magellanic Cloud, using the Infrared Survey Facility (IRSF) and the SIRIUS infrared camera, are presented. Many very red stars were detected and we found that most of them are variables. In the observed colour-magnitude diagram (J - K, K) and the stellar K magnitude distribution, the tip of the first giant branch (TRGB), where helium burning in the core starts, is clearly seen. Apart from the genuine AGB variables, we found many variable stars at luminosities around the TRGB. From this result, we infer that a substantial fraction of them are RGB variables. [ABSTRACT FROM AUTHOR]