- ID:
- ivo://CDS.VizieR/J/PASJ/60/739
- Title:
- Emission-line stars in the W5E HII region
- Short Name:
- J/PASJ/60/739
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have made a new survey of emission-line stars in the W5 E HII region to investigate the population of PMS stars near the OB stars by using the Wide Field Grism Spectrograph 2 (WFGS2). A total of 139 Halpha emission stars were detected and their g'i'-photometry was performed. Their spatial distribution shows three aggregates, i.e., two aggregates near the bright-rimmed clouds at the edge of the W5 E HII region (BRC 13 and BRC 14) and one near the exciting O7V star. The age and mass of each Halpha star were estimated from an extinction-corrected color-magnitude diagram and theoretical evolutionary tracks. We found, for the first time in this region, that the young stars near the exciting star are systematically older (4Myr) than those near the edge of the HII region (1Myr). This result supports that the formation of stars proceeds sequentially from the center of HII region to the eastern bright rim. We further suggest a possibility that the birth of low-mass stars near the exciting star of the HII region precedes the production of massive OB stars in the pre-existing molecular cloud.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/590/A50
- Title:
- eMSTOs in low mass clusters
- Short Name:
- J/A+A/590/A50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an imaging analysis of four low mass stellar clusters (<~5000M_{sun}_) in the outer regions of the LMC in order to shed light on the extended main sequence turn-off (eMSTO) phenomenon observed in high mass clusters. The four clusters have ages between 1-2Gyr and two of them appear to host eMTSOs. The discovery of eMSTOs in such low mass clusters - more than 5 times less massive than the eMSTO clusters previously studied - suggests that mass is not the controlling factor in whether clusters host eMSTOs. Additionally, the narrow extent of the eMSTO in the two older clusters (~2Gyr) is in agreement with predictions of the stellar rotation scenario, as lower mass stars are expected to be magnetically braked, meaning that their colour magnitude diagrams should be better reproduced by canonical simple stellar populations. We also performed a structural analysis on all the clusters and found that a large core radius is not a requisite for a cluster to exhibit an eMSTO.
- ID:
- ivo://CDS.VizieR/J/ApJ/812/89
- Title:
- Environmental COntext (ECO) catalog
- Short Name:
- J/ApJ/812/89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the relationships between galaxy environments and galaxy properties related to disk (re)growth, considering two highly complete samples that are approximately baryonic mass limited into the high-mass dwarf galaxy regime, the Environmental COntext (ECO) catalog (data release herein) and the B-semester region of the REsolved Spectroscopy Of a Local VolumE (RESOLVE) survey. We quantify galaxy environments using both group identification and smoothed galaxy density field methods. We use by-eye and quantitative morphological classifications plus atomic gas content measurements and estimates. We find that blue early-type (E/S0) galaxies, gas-dominated galaxies, and UV-bright disk host galaxies all become distinctly more common below group halo mass ~10^11.5^M_{sun}_, implying that this low group halo mass regime may be a preferred regime for significant disk growth activity. We also find that blue early-type and blue late-type galaxies inhabit environments of similar group halo mass at fixed baryonic mass, consistent with a scenario in which blue early-types can regrow late-type disks. In fact, we find that the only significant difference in the typical group halo mass inhabited by different galaxy classes is for satellite galaxies with different colors, where at fixed baryonic mass red early- and late-types have higher typical group halo masses than blue early- and late-types. More generally, we argue that the traditional morphology-environment relation (i.e., that denser environments tend to have more early-types) can be largely attributed to the morphology-galaxy mass relation for centrals and the color-environment relation for satellites.
- ID:
- ivo://CDS.VizieR/J/ApJ/874/32
- Title:
- Environment and hosts of Type Ia supernovae
- Short Name:
- J/ApJ/874/32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The reliability of Type Ia Supernovae (SNe Ia) may be limited by the imprint of their galactic origins. To investigate the connection between supernovae and their host characteristics, we developed an improved method to estimate the stellar population age of the host as well as the local environment around the site of the supernova. We use a Bayesian method to estimate the star formation history and mass weighted age of a supernova's environment by matching observed spectral energy distributions to a synthesized stellar population. Applying this age estimator to both the photometrically and spectroscopically classified Sloan Digital Sky Survey II supernovae (N=103), we find a 0.114+/-0.039mag "step" in the average Hubble residual at a stellar age of ~8Gyr; it is nearly twice the size of the currently popular mass step. We then apply a principal component analysis on the SALT2 parameters, host stellar mass, and local environment age. We find that a new parameter, PC1, consisting of a linear combination of stretch, host stellar mass, and local age, shows a very significant (4.7{sigma}) correlation with Hubble residuals. There is a much broader range of PC1 values found in the Hubble flow sample when compared with the Cepheid calibration galaxies. These samples have mildly statistically different average PC1 values, at ~2.5{sigma}, resulting in at most a 1.3% reduction in the evaluation of H0. Despite accounting for the highly significant trend in SN Ia Hubble residuals, there remains a 9% discrepancy between the most recent precision estimates of H0 using SN Ia and the CMB.
- ID:
- ivo://CDS.VizieR/J/AJ/135/1311
- Title:
- Environments of moderate redshift radio galaxies
- Short Name:
- J/AJ/135/1311
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the local universe, high-power radio galaxies live in lower-density environments than low-luminosity radio galaxies. If this trend continued to higher redshifts, powerful radio galaxies would serve as efficient probes of moderate redshift groups and poor clusters. Photometric studies of radio galaxies at 0.3<~z<~0.5 suggest that the radio luminosity-environment correlation disappears at moderate redshifts, though this could be the result of foreground/background contamination affecting the photometric measures of environment. We have obtained multi-object spectroscopy in the fields of 14 lower luminosity (L_1.4GHz_<4x10^24^W/Hz) and higher luminosity (L_1.4GHz_>1.2x10^25^W/Hz) radio galaxies at z~0.3 to spectroscopically investigate the link between the environment and the radio luminosity of radio galaxies at moderate redshifts. Our results support the photometric analyses; there does not appear to be a correlation between the luminosity of a radio galaxy and its environment at moderate redshifts. Hence, radio galaxies are not efficient signposts for group environments at moderate redshifts.
- ID:
- ivo://CDS.VizieR/J/A+A/628/A64
- Title:
- EPIC 212036875b griz light curves
- Short Name:
- J/A+A/628/A64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Although more than 2000 brown dwarfs have been detected to date, mainly from direct imaging, their characterisation is difficult due to their faintness and model dependent results. In the case of transiting brown dwarfs it is, however, possible to make direct high precision observations. Our aim is to investigate the nature and formation of brown dwarfs by adding a new well-characterised object, in term of its mass, radius and bulk density, to the currently small sample of less than 20 transiting brown dwarfs. One brown dwarf candidate was found by the KESPRINT consortium when searching for exoplanets in the K2 space mission Campaign 16 field. We combined the K2 photometric data with a series of multi-colour photometric observations, imaging and radial velocity measurements to rule out false positive scenarios and to determine the fundamental properties of the system. We report the discovery and characterisation of a transiting brown dwarf in a 5.17 day eccentric orbit around the slightly evolved F7V star EPIC 212036875. EPIC 212036875b is a rare object that resides in the brown dwarf desert. In the mass-density diagram for planets, brown dwarfs and stars, we find that all giant planets and brown dwarfs follow the same trend from 0.3M_J_ to the turn-over to hydrogen burning stars at 73M_J_. EPIC 212036875b falls on the theoretical line for H/He dominated planets in this diagram as determined by interior structure models, as well as on the empirical fit. We argue that EPIC 212036875b formed via gravitational disc instabilities in the outer part of the disc, followed by a quick migration. Orbital tidal circularisation may have started early in its history for a brief period when the brown dwarf's radius was larger. The lack of spin-orbit synchronisation points to a weak stellar dissipation parameter which implies a circularisation timescale of 23Gyr, or suggests an interaction between the magnetic and tidal forces of the star and the brown dwarf.
- ID:
- ivo://CDS.VizieR/J/A+A/566/A43
- Title:
- EPOCH Project. EROS-2 LMC periodic variables
- Short Name:
- J/A+A/566/A43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The EPOCH (EROS-2 periodic variable star classification using machine learning) project aims to detect periodic variable stars in the EROS-2 light curve database. In order to classify these variables, we first build a training set by compiling known variables in the Large Magellanic Could area from the OGLE and MACHO surveys. We crossmatch these variables with the EROS-2 sources and extract 22 variability features from 28,392 light curves of the corresponding EROS-2 sources. We then use Random Forests to classify the EROS-2 sources in the training set. We design the model to separate not only Delta Scuti stars, RR Lyraes, Cepheids, eclipsing binaries and long-period variables, the "superclasses", but also their subclasses, such as RRab, RRc, RRd and RRe for RR Lyraes, and similarly for the other variable types. We apply the trained model to the entire EROS-2 LMC database containing about 29 million sources and find 117,234 periodic variable candidates. Out of these 117,234 periodic variables, 55,285 have not been discovered by either OGLE or MACHO variability studies. This set comprises 1906 Delta Scuti stars, 6,607 RR Lyraes, 638 Cepheids, 178 Type II Cepheids, 34,562 eclipsing binaries and 11,394 long-period variables.
- ID:
- ivo://CDS.VizieR/J/ApJ/881/87
- Title:
- 9 epochs spectroscopy of type I supernova SN 201iet
- Short Name:
- J/ApJ/881/87
- Date:
- 08 Dec 2021
- Publisher:
- CDS
- Description:
- We present optical photometry and spectroscopy of SN2016iet (=Gaia16bvd=PS17brq), an unprecedented Type I supernova (SNI) at z=0.0676 with no obvious analog in the existing literature. SN2016iet exhibits a peculiar light curve, with two roughly equal brightness peaks (~-19mag) separated by about 100 days, and a subsequent slow decline by about 5mag in 650 rest-frame days. The spectra are dominated by strong emission lines of calcium and oxygen, with a width of only 3400km/s, superposed on a strong blue continuum in the first year. There is no clear evidence for hydrogen or helium associated with the SN at any phase. The nebular spectra exhibit a ratio of L_CaII_/L_OI_~4, much larger than for core-collapse SNe and TypeI superluminous SNe. We model the light curves with several potential energy sources: radioactive decay, a central engine, and ejecta-circumstellar medium (CSM) interaction. Regardless of the model, the inferred progenitor mass near the end of its life (i.e., the CO core mass) is >~55M{sun} and potentially up to 120M{sun}, clearly placing the event in the regime of pulsational pair instability supernovae (PPISNe) or pair instability supernovae (PISNe). The models of CSM interaction provide the most consistent explanation for the light curves and spectra, and require a CSM mass of ~35M{sun} ejected in the final decade before explosion. We further find that SN2016iet is located at an unusually large projected offset (16.5kpc, 4.3 effective radii) from its low-metallicity dwarf host galaxy (Z~0.1Z{sun}, L~0.02L*, M~108.5M{sun}), supporting the interpretation of a PPISN/PISN explosion. In our final spectrum at a phase of about 770 rest-frame days we detect weak and narrow H{alpha} emission at the location of the SN, corresponding to a star formation rate of ~3x10^-4^M{sun}/yr, which is likely due to a dim underlying galaxy host or an HII region. Despite the overall consistency of the SN and its unusual environment with PPISNe and PISNe, we find that the inferred properties of SN2016iet challenge existing models of such events.
- ID:
- ivo://CDS.VizieR/J/AJ/160/104
- Title:
- {Epsilon} CrA components radial & orbital velocity
- Short Name:
- J/AJ/160/104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution spectroscopic observations of the W UMa-type binary {Epsilon}CrA obtained as a time-monitoring sequence on four full and four partial nights within two weeks have been used to derive orbital elements of the system and discuss the validity of the Lucy model for description of the radial-velocity data. The observations had more extensive temporal coverage and better quality than similar time-sequence observations of the contact binary AW UMa. The two binaries share several physical properties and show very similar deviations from the Lucy model: the primary component is a rapidly rotating star almost unaffected by the presence of the secondary component, while the latter is embedded in a complex gas flow and appears to have its own rotation-velocity field, in contradiction to the model. The spectroscopic mass ratio is found to be larger than the one derived from the light-curve analysis, as in many other W UMa-type binaries, but the discrepancy for {Epsilon} CrA is relatively minor, much smaller than for AW UMa. The presence of the complex velocity flows contradicting the assumption of solid-body rotation suggests a necessity of modification to the Lucy model, possibly along the lines outlined by Stepien in his concept of energy transfer between the binary components.
- ID:
- ivo://CDS.VizieR/J/A+A/510/A99
- Title:
- Epsilon Indi Ba and Bb IR spectra
- Short Name:
- J/A+A/510/A99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The discovery of epsilon Indi Ba, Bb, a binary brown dwarf system very close to the Sun, makes possible a concerted campaign to characterise the physical parameters of two T dwarfs. Recent observations suggest substellar atmospheric and evolutionary models may be inconsistent with observations, but there have been few conclusive tests to date. We therefore aim to characterise these benchmark brown dwarfs to place constraints on such models. We have obtained high angular resolution optical, near-infrared, and thermal-infrared imaging and medium-resolution (up to R~5000) spectroscopy of epsilon Indi Ba, Bb with the ESO VLT and present VRIzJHKL'M' broad-band photometry and 0.63-5.1 micron spectroscopy of the individual components. The photometry and spectroscopy of the two partially blended sources were extracted with a custom algorithm. Furthermore, we use deep AO-imaging to place upper limits on the (model-dependent) mass of any further system members. We derive luminosities of log L/L_{sun}=-4.699+/-0.017 and -5.232+/-0.020 for epsilon Indi Ba, Bb, respectively, and using the dynamical system mass and COND03 evolutionary models predict a system age of 3.7-4.3Gyr, in excess of previous estimates and recent predictions from observations of these brown dwarfs. Moreover, the effective temperatures of 1352-1385K and 976-1011K predicted from the COND03 evolutionary models, for epsilon Indi Ba and Bb respectively, are in disagreement with those derived from the comparison of our data with the BT-Settl atmospheric models where we find effective temperatures of 1300-1340K and 880-940K, for epsilon Indi Ba and Bb respectively, with surface gravities of logg=5.25 and 5.50. Finally, we show that spectroscopically determined effective temperatures and surface gravities for ultra-cool dwarfs can lead to underestimated masses even where precise luminosity constraints are available.
