IC 1274 is a faintly luminous nebula lying on the near surface of the Lynds 227 (L227) molecular cloud. Four luminous, early-type (B0-B5) stars are located within a spherical volume ~5' in diameter that appears to be clear of heavy obscuration. Approximately centered in the cleared region is the B0 V star HD 166033, which is thought to be largely responsible for the cavity's excavation. Over 80 H-alpha emission sources brighter than V~21 have been identified in the region. More than half of these are concentrated in IC 1274 and are presumably members of a faint T Tauri star population. Chandra Advanced CCD Imaging Spectrometer (ACIS) imaging of a nearby suspected pulsar and time-variable gamma-ray source (GeV J1809-2327) detected 21 X-ray sources in the cluster vicinity, some of which are coincident with the early-type stars and H-alpha emitters in IC 1274. Deep (V~22) optical BVRI photometry has been obtained for the cluster region. A distance of 1.82 +/- 0.3 kpc and a mean extinction of Av ~1.21 +/- 0.2 mag follow from photometry of the early-type stars. Using pre-main-sequence evolutionary models, we derive a median age for the H-alpha emitters and X-ray sources of ~1 Myr; however, a significant dispersion is present. Our interpretation of the structure of IC 1274 is that the early-type stars formed recently and are in the process of dispersing the molecular gas on the near surface of L227. The displaced material was driven against what remains of the molecular cloud to the east, enabling the formation of the substantial number of T Tauri stars found there. We identify a V~21.5 star very near the position of X-ray source 5, the assumed gamma-ray source and young pulsar candidate. The lack of distinctive characteristics for this source, however, coupled with the density of faint stars in this region suggest that this may be a random superposition.
The effects of the overshooting of the convective core on main-sequence turnoffs of young- and intermediate-age star clusters
最近的研究表明，扩展的主序星转折点（eMSTO）是麦哲伦星云中中等年龄星团的一个共同特征。eMSTO也出现在100年星团的色星等图（CMD）中。eMSTO的起源仍然是一个悬而未决的问题。此外，星震学表明，对流核的过冲参数$δ_{\rm ov}$的值对于质量近似相等的恒星是不固定的。因此，星团的MSTO可能会受到对流核心（OVCC）过冲的影响。我们计算了不同$δ_{\rm ov}$的OVCC对年轻和中等年龄星团MSTO的影响。\textbf{If $δ_{\rm ov}$ varies between stars in a cluster,}观测到的年轻和中等年龄星团的eMSTO可以很好地解释的影响。由OVCC引起的MSTO的等效年龄扩展与星团的年龄有关，并且与许多星团的观测结果符合得很好。此外，观测到的NGC 1856的eMSTO被具有不同$δ_{\rm ov}$的同时代人群所复制。星团的eMSTO可能与OVCC效应有关。OVCC的影响\textbf{are similar to that of rotation in some respects. But the effects cannot result in a significant split of main sequence of young star clusters at $m_{U}\lesssim 21$.}快速…
Geological evidence suggests liquid water near the Earth's surface as early as 4.4 billion years ago when the faint young Sun only radiated about 70% of its modern power output. At this point, the Earth should have been a global snowball if it possessed atmospheric properties similar to those of the modern Earth. An extreme atmospheric greenhouse effect, an initially more massive Sun, release of heat acquired during the accretion process of protoplanetary material, and radioactivity of the early Earth material have been proposed as reservoirs or traps for heat. For now, the faint-young-sun par…
Multiple stellar populations (MPs) representing star-to-star light-element abundance variations are common in nearly all ancient Galactic globular clusters. Here we provide the strongest evidence yet that the populous, ~ 1.7 Gyr-old Large Magellanic Cloud cluster NGC 2173 also exhibits light-element abundance variations. Thus, our results suggest that NGC 2173 is the youngest cluster for which MPs have been confirmed to date. Our conclusion is based on the distinct bifurcation at the tip of its red-giant branch in high-quality color--magnitude diagrams generated from Hubble Space Telescope ima…
Variability survey in the young open cluster IC 1805
年轻疏散星团IC 1805的变星巡天是正在弗罗茨瓦夫进行的北天疏散星团中寻找早期型变星计划的一部分（参见Jerzykiewicz et al. 2011及其参考文献）。我们特别感兴趣的脉动恒星，如仙王座β和SPB。这些恒星是非常有希望的星震学目标。特别是，富含这些变量的疏散星团可用于所谓的集合星震学（Saesen et al. 2010）。
Proton Irradiation of Primitive Atmospheres of Young Exoplanets and early Earth: $N_{\mathrm{2}}O$ Greenhouse Warming and Prebiotic Synthesis
Yokohama National University（横滨国立大学）；Institute of Science Tokyo（东京科学大学）；NASA Goddard Space Flight Center（美国国家航空航天局戈达德太空飞行中心）；American University（美利坚大学）；Kyoto University（京都大学）；Tokai-mura, Naka-gun, Ibaraki（茨城县那珂郡东海村）；Tokyo City University（东京都立大学）；Uppsala University（乌普萨拉大学）；NASA Langley Research Center（美国国家航空航天局兰利研究中心）
We searched through a seven-million cubic-parsec volume surrounding each of the four nearest young open clusters with ages from 40 to 80 Myr to identify both the current and past members of the clusters within the Gaia EDR3 dataset. We find over 1,700 current cluster members and over 1,200 candidate escapees. Many of these candidates lie well in front and behind the cluster from our point of view, so formerly they were considered cluster members, but their parallaxes put them more than 10 pc from the centre of the cluster today. We found two candidate high-mass white dwarfs that may have escap…
Young star clusters consisting of massive stars are the ideal sites to study the star formation processes and influence of massive stars on the subsequent star formation. NGC 1893 is a young star cluster associated with the HII region Sh2-236. It contains about five `O'-type stars and several early `B'-type stars. It is located at a distance of $\sim$3.25 kpc and has a reddening, E(B-V)$\sim$0.4 mag. To characterize the young low-mass stellar population in the central portion of the cluster, we carried out deep VI band observations of the region using the 4K$\times$4K CCD IMAGER mounted on the…
In deep near-infrared imaging of the low-metallicity (${\rm [O/H]}=-0.7$ dex) H II region Sh 2-127 (S127) with Subaru/MOIRCS, we detected two young clusters with 413 members (S127A) in a slightly extended H II region and another with 338 members (S127B) in a compact H II region. The limiting magnitude was $K=21.3$ mag (10$σ$), corresponding to a mass detection limit of $\sim$0.2 $M_\odot$. These clusters are an order of magnitude larger than previously studied young low-metallicity clusters and larger than the majority of solar neighborhood young clusters. Fits to the K-band luminosity functio…
A primordial group of open clusters containing NGC 6871 is confirmed and described through Gaia DR3 data and the previous literature. It is a star-forming complex containing at least six young OCs, including Teutsch 8, FSR 198 and Biurakan 2. Two nearby OCs (Casado 82 and Casado-Hendy 1) are newly identified and studied in detail and found to be also members of the cited group. The parameters of the components are sufficiently similar to postulate the case of at least six clusters born from a single GMC. None of the cluster pairs of the group seems to be an authentic binary cluster, with the p…
Context: The Carina Nebula complex (CNC) is one of the most massive and active star-forming regions in our Galaxy and it contains several large young star clusters. The distances of the individual clusters and their physical connection were poorly known up to now, with strongly discrepant results reported in the literature. Aims: We want to determine reliable distances of the young stellar clusters in the central Carina Nebula region (in particular, Tr 14, 15, and 16) and the prominent clusters NGC 3324 and NGC 3293 in the northwestern periphery of the CNC. Methods: We analyzed the parallaxes …
The rotational evolution of a young stellar population can give informations about the rotation pattern of more evolved clusters. Combined with rotational period values of thousands of young stars and theoretical propositions about the redistribution and loss of stellar angular momentum, it allows us to trace the rotational history of stars according to their mass. We want to investigate how internal and environmental changes on single stars can change the rotational evolution of a young stellar population. We run Monte Carlo simulations of a young cluster composed by solar mass stars of 0.5, …
We report the results of our search of planet candidates in Open Clusters and Young Stellar Associations based on the TESS Objects of Interest Catalog. We find one confirmed planet, one promising candidate, one brown dwarf, and three unverified planet candidates in a sample of 1229 Open Clusters from the second Gaia data release. We discuss individual planet-star systems based on their basic parameters, membership probability, and the observation notes from the ExoFOP-TESS website. We also find ten planet candidates (P $>$ 95%) in Young Stellar Associations by using the BANYAN $Σ$ Bayesian Alg…
Young star clusters are likely the most common birthplace of massive stars across cosmic time and influence the formation of compact binaries in several ways. Here, we simulate the formation of black hole -- neutron star binaries (BHNSs) in young star clusters, by means of the binary population synthesis code \texttt{MOBSE} interfaced with the $N$-body code \texttt{NBODY6++GPU}. BHNSs formed in young star clusters (dynamical BHNSs) are significantly more massive than BHNSs formed from isolated binaries (isolated BHNSs): $\sim{}40$~\% of the dynamical BHNS mergers have total mass $>15$ M$_\odot…
