High Amplitude δ-Scutis in the Large Magellanic Cloud
A. Garg, K. H. Cook, S. Nikolaev, M. E. Huber, A. Rest, A. C. Becker, P. Challis, A. Clocchiatti, G. Miknaitis, D. Minniti, L. Morelli, K. Olsen, J. L. Prieto, … 展开作者
A. Garg, K. H. Cook, S. Nikolaev, M. E. Huber, A. Rest, A. C. Becker, P. Challis, A. Clocchiatti, G. Miknaitis, D. Minniti, L. Morelli, K. Olsen, J. L. Prieto, N. B. Suntzeff, D. L. Welch, W. M. Wood-Vasey
We present 2323 High-Amplitude δ-Scuti (HADS) candidates discovered in the Large Magellanic Cloud (LMC) by the SuperMACHO survey (Rest et al. 2005). Frequency analyses of these candidates reveal that several are multimode pulsators, including 119 whose largest amplitude of pulsation is in the fundamental (F) mode and 19 whose largest amplitude of pulsation is in the first overtone (FO) mode. Using Fourier decomposition of the HADS light curves, we find that the period-luminosity (PL) relation defined by the FO pulsators does not show a clear separation from the PL-relation defined by the F pulsators. This differs from other instability strip pulsators such as type c RR Lyrae. We also present evidence for a larger amplitude, subluminous population of HADS similar to that observed in Fornax (Poretti et al. 2008).
The Magellanic Clouds are nearby dwarf irregular galaxies that represent a unique laboratory for studying galaxy interactions. Their morphology and dynamics have been heavily influenced by their mutual interactions as well as with their interaction(s) with the Milky Way. We use the VISTA near-infrared YJKs survey of the Magellanic Clouds system (VMC) in combination with stellar partial models of the Large Magellanic Cloud (LMC), the Small Magellanic Cloud (SMC) and the Milky Way to investigate the spatial distribution of stellar populations of different ages across the Magellanic Clouds. In th…
We investigate infrared properties of asymptotic giant branch (AGB) stars in our Galaxy and the Magellanic Clouds using various infrared observational data and theoretical models. We use catalogs for the sample of 4996 AGB stars in our Galaxy and about 39,000 AGB stars in the Magellanic Clouds from the available literature. For each object in the sample, we cross-identify the 2MASS, WISE, and Spitzer counterparts. To compare the physical properties of O-rich and C-rich AGB stars in our Galaxy and the Magellanic Clouds, we present IR two color diagrams (2CDs) using various photometric data. We …
We present a self-consistent study of cool supergiants (CSGs) belonging to the Magellanic clouds. We calculated stellar atmospheric parameters using LTE KURUCZ and MARCS atmospheric models for more than 400 individual targets by fitting a careful selection of weak metallic lines. We explore the existence of a T eff scale and its implications in two different metallicity environments (each Magellanic cloud). Critical and in-depth tests have been performed to assess the reliability of our stellar parameters (i.e. internal error budget, NLTE systematics). In addition, several Montercarlo tests ha…
The population of classical novae in the Magellanic Clouds was poorly known because of a lack of systematic studies. There were some suggestions that nova rates per unit mass in the Magellanic Clouds were higher than in any other galaxy. Here, we present an analysis of data collected over 16 years by the OGLE survey with the aim of characterizing the nova population in the Clouds. We found 20 eruptions of novae, half of which are new discoveries. We robustly measure nova rates of $2.4 \pm 0.8$ yr$^{-1}$ (LMC) and $0.9 \pm 0.4$ yr$^{-1}$ (SMC) and confirm that the K-band luminosity-specific nov…
We present initial results of the first large scale survey of embedded star clusters in molecular clouds in the Large Magellanic Cloud (LMC) using near-infrared (NIR) imaging from the VISTA Magellanic Clouds Survey (Cioni et al. 2011). We have explored a ~1.65 square degree area of the LMC, which contains the well-known star-forming region 30 Doradus as well as ~14 percent of the galaxy's CO clouds (Wong et al. 2011), and have identified 67 embedded cluster candidates, 45 of which are newly discovered as clusters. We have determined sizes, luminosities and masses for these embedded clusters, e…
An overview is provided of the scientific goals of the Magellanic Cloud component of the STScI Directors Discretionary UV initiative ULLYSES, together with the complementary spectroscopic survey XShootU (VLT/Xshooter) and other ancillary datasets. Together, ULLYSES and XShootU permit the first comprehensive, homogeneous study of wind densities and velocities in metal-poor massive stars, plus UV/optical spectroscopic libraries for population synthesis models and a large number of interstellar sight-lines towards the Magellanic Clouds.
2dF-AAOmega spectroscopy of massive stars in the Magellanic Clouds: The north-eastern region of the Large Magellanic Cloud
我们目前的光谱分类从光学光谱的263个大质量恒星在东北地区的大麦云云。观测到的2度场包括巨大的剑鱼座30恒星形成区，SN 1987 A的周围地区，以及剑鱼座30以南的一些恒星形成复合体。这是大多数恒星（203颗）的第一次分类，包括11颗双线分光双星。该样品还包括早期OC型光谱的第一个例子（AAOmega 30 Dor 248和280），其氮光谱的弱点和C IV 4658发射区分。我们建议，这些恒星有相对未加工的CNO丰度相比，形态正常的O型恒星，指示一个较早的演化阶段。通过对连续两个晚上观测结果的分析，我们对233颗恒星的径向速度进行了估计，发现了一个明显的单线双星和9个（> 3 sigma）与系统速度相比的异常值;后者可能是逃逸星或大振幅双星系统，需要进一步的光谱学来研究它们的性质。
A very long term near-infrared variable star survey towards the Large and Small Magellanic Clouds was carried out using the 1.4m InfraRed Survey Facility at the South African Astronomical Observatory. This project was initiated in December 2000 in the LMC, and in July 2001 in the SMC. Since then an area of 3 square degrees along the bar in the LMC and an area of 1 square degree in the central part of the SMC have been repeatedly observed. This survey is ongoing, but results obtained with data taken until December 2017 are reported in this paper. Over more than 15 years we have observed the two…
We started a photometric survey using the WFC3/UVIS instrument onboard the Hubble Space Telescope to search for multiple populations within Magellanic Cloud star clusters at various ages. In this paper, we introduce this survey. As first results of this programme, we also present multi-band photometric observations of NGC 121 in different filters taken with the WFC3/UVIS and ACS/WFC instruments. We analyze the colour-magnitude diagram (CMD) of NGC 121, which is the only "classical" globular cluster within the Small Magellanic Cloud. Thereby, we use the pseudo-colour C_(F336W,F438W,F343N)=(F336…
We obtained new spectra of fourteen Magellanic Cloud planetary nebulae with the South African Large Telescope to determine heating rates of their central stars and to verify evolutionary models of post-asymptotic giant branch stars. We compared new spectra with observations made in previous years. Five planetary nebulae showed an increase in excitation over time. Four of their central stars exhibit [WC] features in their spectra, including three new detections. This raises the total number of [WC] central stars of PNe in the Magellanic Clouds to ten. We compared determined heating rates of the…
The chemical abundances of a galaxy's metal-poor stellar population can be used to investigate the earliest stages of its formation and chemical evolution. The Magellanic Clouds are the most massive of the Milky Way's satellite galaxies and are thought to have evolved in isolation until their recent accretion by the Milky Way. Unlike the Milky Way's less massive satellites, little is know about the Magellanic Clouds' metal-poor stars. We have used the mid-infrared metal-poor star selection of Schlaufman & Casey (2014) and archival data to target nine LMC and four SMC giants for high-resolution…
We study three subregions in the HII region N11 which is located at the northeast side of the Large Magellanic Cloud (LMC). We used $^{12}$CO and $^{13}$CO J=3--2 data observed with the Atacama Submillimeter Telescope Experiment (ASTE) with an angular and spectral resolution of 22$^{\prime\prime}$ and 0.11 km s$^{-1}$ respectively. From the $^{12}$CO J=3--2 and $^{13}$CO J=3--2 integrated maps we estimated, assuming local thermodynamic equilibrium (LTE), masses in about $10^4$ M$_\odot$ for the molecular clouds associated with each subregion. Additionally, from the mentioned maps we study the …
Classical supersoft X-ray sources (SSSs) are understood as close binary systems in which a massive white dwarf (WD) accretes from its companion at rates sustaining steady hydrogen burning on its surface generating bolometric luminosities of $10^{36}-2\times10^{38}$ erg/s. Here, we perform for the first time the global supersoft X-rays to near-infrared (NIR) spectral energy distribution (SED) for the brightest SSSs in LMC and SMC. We test a model in which the ultraviolet--NIR is dominated by the emission from a compact (unresolved) circumstellar nebula represented by the ionized gas out-flowing…
