- ID:
- ivo://CDS.VizieR/J/ApJ/884/6
- Title:
- Known members of Orion A with Gaia DR2 data
- Short Name:
- J/ApJ/884/6
- Date:
- 04 Dec 2021
- Publisher:
- CDS
- Description:
- The star-forming region of the Orion Nebula (ONC) is ideal to study the stellar dynamics of young stars in a clustered environment. Using Gaia DR2 we search for pre-main sequence stars with unusually high proper motions that may be representative of a dynamical ejection from unstable young triple systems or other close three-body encounters. We identify 26 candidate stars that are likely to have had such an encounter in the last 1Myr. Nine of these stars could be traced back to the densest central-most region of the ONC, the Trapezium, while five others have likely interactions with other OB-type stars in the cluster. Seven stars originate from other nearby populations within the Orion Complex that coincidentally scattered toward the ONC. A definitive point of origin cannot be identified for the remaining sources. These observations shed light on the frequency of the ejection events in young clusters.
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- ID:
- ivo://CDS.VizieR/J/AJ/162/101
- Title:
- K2 ugri & H{alpha} photometry in the Lagoon Nebula
- Short Name:
- J/AJ/162/101
- Date:
- 14 Mar 2022 06:42:13
- Publisher:
- CDS
- Description:
- Space observatories have provided unprecedented depictions of the many variability behaviors typical of low-mass, young stars. However, those studies have so far largely omitted more massive objects (~2M{sun} to 4-5M{sun}) and were limited by the absence of simultaneous, multiwavelength information. We present a new study of young star variability in the ~1-2Myr old, massive Lagoon Nebula region. Our sample encompasses 278 young, late B to K-type stars, monitored with Kepler/K2. Auxiliary u, g, r, i, H{alpha} time-series photometry, simultaneous with K2, was acquired at the Paranal Observatory. We employed this comprehensive data set and archival infrared photometry to determine individual stellar parameters, assess the presence of circumstellar disks, and tie the variability behaviors to inner disk dynamics. We found significant mass-dependent trends in variability properties, with B/A stars displaying substantially reduced levels of variability compared to G/K stars for any light-curve morphology. These properties suggest different magnetic field structures at the surface of early-type and later-type stars. We also detected a dearth of some disk-driven variability behaviors, particularly dippers, among stars earlier than G. This indicates that their higher surface temperatures and more chaotic magnetic fields prevent the formation and survival of inner disk dust structures corotating with the star. Finally, we examined the characteristic variability timescales within each light curve and determined that the day-to-week timescales are predominant over the K2 time series. These reflect distinct processes and locations in the inner disk environment, from intense accretion triggered by instabilities in the innermost disk regions to variable accretion efficiency in the outer magnetosphere.
- ID:
- ivo://CDS.VizieR/J/A+A/555/A8
- Title:
- L1448 and HH211 CO(6-5) velocity maps
- Short Name:
- J/A+A/555/A8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of CO rotational transitions in the 0.3-0.4 millimeter range, now possible from exceptional sites on the ground, provide the opportunity of studing the warm component of molecular outflows in star-forming regions. This study aims to characterize the role of the warm gas in high-velocity and collimated outflows from Class 0 low-mass protostars. We used the CHAMP+ heterodyne array on the APEX telescope to map the CO (6-5) and CO (7-6) emission in the well-known Class 0 outflows L1448-mm and HH211-mm. We complement these data with ^13^CO (6-5) observations and also with previous low-J CO observations. The CO (6-5) and (7-6) emission was detected to be tracing the outflow lobes. In L1448, extremely high-velocity (EHV) emission was detected in both transitions. In HH211, high-velocity CO (6-5) emission was detected to be tracing the regions close to the central object, but it was also found close to the bow-shock regions seen in the mid-IR. A large velocity gradient code applied to these and the complementary low-J CO data revealed the high-velocity components to be dense (10^5^cm^-3) and warm (T>200K) gas, in agreement with previous observations of shock tracers such as SiO. The high-velocity emission of these mid-J CO transitions are very good tracers of the inner highly excited part of outflows, which possibly is molecular material related to the underlying jet. In addition, these transitions are also strong at the bow-shock positions, which make them a good tool for probing these environments.
- ID:
- ivo://CDS.VizieR/J/A+A/604/A20
- Title:
- L1157-B1 DCN (2-1) and H^13^CN (2-1) datacubes
- Short Name:
- J/A+A/604/A20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed high-angular-resolution observations toward L1157-B1 with the IRAM NOEMA interferometer of the DCN (2-1) and H^13^CN (2-1) lines to compute the deuterated fraction, D_frac_(HCN), and compare it with previously reported D_frac_ of other molecular species. Our aim is to observationally investigate the role of the different chemical processes at work that lead to formation of the DCN and compare it with HDCO, the two deuterated molecules imaged with an interferometer, and test the predictions of the chemical models for their formation.
- ID:
- ivo://CDS.VizieR/J/A+A/558/A94
- Title:
- L1157 blue lobe SiO, H2CO, and CH3OH maps
- Short Name:
- J/A+A/558/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the Submillimeter Array at 1.4mm to observe the blue lobe of the L1157 outflow at high spatial resolution (~3"). We detected SiO, H_2_CO, and CH_3_OH lines from several molecular clumps that constitute the outflow. All three molecules were detected along the wall of the inner cavity that is thought to be related to the later ejection event. On the other hand, no emission was detected toward positions related to an old ejection episode, which is very likely due to space filtering from the interferometer. The H_2_CO and CH_3_OH emission is detected only at velocities close to the systemic velocity. The spatial distributions of the H_2_CO and CH_3_OH are similar. These emission lines trace the U-shaped structure seen in the mid-infrared image. In contrast, the SiO emission is detected in a wider velocity range with a peak at ~14km/s blueshifted from the systemic velocity. The SiO emission is brightest at the B1 position, which corresponds to the apex of the U-shaped structure. There are two compact SiO clumps along the faint arc-like feature to the east of the U-shaped structure. At the B1 position, there are two velocity components; one is a compact clump with a size of ~1500AU seen at high velocity, the other is an extended component with lower velocities. The kinematic structure at the B1 position is different from that expected in a single bow shock. Most likely the high-velocity SiO clump at the B1 position is kinetically independent of the low-velocity gas. The line ratio between SiO (5-4) and SiO (2-1) suggests that the high-velocity SiO clumps consist of high-density gas of n~10^5^-10^6^cm^-3^, which is similar to the density of the bullets in extremely high velocity (EHV) jets. The high-velocity SiO clumps in L1157 probably have the same origin as the EHV bullets.
- ID:
- ivo://CDS.VizieR/J/ApJ/809/42
- Title:
- LC and RV data of PTFO 8-8695 T-Tauri star
- Short Name:
- J/ApJ/809/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Spitzer 4.5{mu}m light curve observations, Keck NIRSPEC radial velocity observations, and LCOGT optical light curve observations of PTFO 8-8695, which may host a Jupiter-sized planet in a very short orbital period (0.45 days). Previous work by van Eyken et al. (2012ApJ...755...42V) and Barnes et al. (2013ApJ...774...53B) predicts that the stellar rotation axis and the planetary orbital plane should precess with a period of 300-600 days. As a consequence, the observed transits should change shape and depth, disappear, and reappear with the precession. Our observations indicate the long-term presence of the transit events (>3 years), and that the transits indeed do change depth, disappear and reappear. The Spitzer observations and the NIRSPEC radial velocity observations (with contemporaneous LCOGT optical light curve data) are consistent with the predicted transit times and depths for the M*=0.34M_{sun}_ precession model and demonstrate the disappearance of the transits. An LCOGT optical light curve shows that the transits do reappear approximately 1 year later. The observed transits occur at the times predicted by a straight-forward propagation of the transit ephemeris. The precession model correctly predicts the depth and time of the Spitzer transit and the lack of a transit at the time of the NIRSPEC radial velocity observations. However, the precession model predicts the return of the transits approximately 1 month later than observed by LCOGT. Overall, the data are suggestive that the planetary interpretation of the observed transit events may indeed be correct, but the precession model and data are currently insufficient to confirm firmly the planetary status of PTFO 8-8695b.
- ID:
- ivo://CDS.VizieR/J/A+A/643/A48
- Title:
- Linking ice and gas. Serpens SVS4
- Short Name:
- J/A+A/643/A48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The interaction between dust, ice, and gas during the formation of stars produces complex organic molecules. While observations indicate that several species are formed on ice-covered dust grains and are released into the gas phase, the exact chemical interplay between solid and gas phases and their relative importance remain unclear. Our goal is to study the interplay between dust, ice, and gas in regions of low-mass star formation through ice- and gas- mapping and by directly measuring gas-to-ice ratios. This provides constraints on the routes that lead to the chemical complexity that is observed in solid and gas phases. We present observations of gas-phase methanol (CH_3_OH) and carbon monoxide (^13^CO and C^18^O) at 1.3mm towards ten low-mass young protostars in the Serpens SVS4 cluster from the SubMillimeter Array (SMA) and the Atacama Pathfinder EXperiment (APEX) telescope. We used archival data from the Very Large Telescope (VLT) to derive abundances of ice H_2_O, CO, and CH_3_OH towards the same region. Finally, we constructed gas-ice maps of SVS4 and directly measured CO and CH_3_OH gas-to-ice ratios. The SVS4 cluster is characterised by a global temperature of 15+/-5K. At this temperature, the chemical behaviours of CH_3_OH and CO are anti-correlated: larger variations are observed for CH_3_OH gas than for CH_3_OH ice, whereas the opposite is seen for CO. The gas-to-ice ratios (N_gas_/N_ice_) range from 1-6 for CO and 1.4x10^-4^-3.7x10^-3^for CH_3_OH. The CO gas-maps trace an extended gaseous component that is not sensitive to the effect of freeze-out. Because of temperature variations and dust heating around 20K, the frozen CO is efficiently desorbed. The CH_3_OH gas-maps, in contrast, probe regions where methanol is predominantly formed and present in ices and is released into the gas phase through non-thermal desorption mechanisms. Combining gas- and ice-mapping techniques, we measure gas-to-ice ratios of CO and CH_3_OH in the SVS4 cluster. The CH_3_OH gas-to-ice ratio agrees with values that were previously reported for embedded Class 0/I low-mass protostars. We find that there is no straightforward correlation between CO and CH_3_OH gas with their ice counterparts in the cluster. This is likely related to the complex morphology of SVS4: the Class 0 protostar SMM4 and its envelope lie in the vicinity, and the outflow associated with SMM4 intersects the cluster. This study serves as a pathfinder for future observations with ALMA and the James Webb Space Telescope (JWST) that will provide high-sensitivity gas-ice maps of molecules more complex than methanol. Such comparative maps will be essential to constrain the chemical routes that regulate the chemical complexity in star-forming regions.
- ID:
- ivo://CDS.VizieR/J/A+A/475/915
- Title:
- L1489IRS observed by the submillimeter array
- Short Name:
- J/A+A/475/915
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Submillimeter Array observations of the Young Stellar Object L1489IRS (IRAS 04016+2610). These include images of the continuum at 267 GHz (1.12 mm) and line emission of the HCO+ J=3-2 transition at 267.55762 GHz. The HCO+ image is available in two different (u,v)-weighting schemes, natural and uniform, optimizing for S/N and resolution respectively. The continuum image is only available in uniform weighting. The synthesized beam size is 1".
- ID:
- ivo://CDS.VizieR/J/MNRAS/454/1468
- Title:
- LMC post-AGB, post-RGB star and YSOs
- Short Name:
- J/MNRAS/454/1468
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out a search for optically visible post-Asymptotic Giant Branch (post- AGB) stars in the Large Magellanic Cloud (LMC). First, we selected candidates with a mid-IR excess and then obtained their optical spectra. We disentangled contaminants with unique spectra such as M-stars, C-stars, planetary nebulae, quasi-stellar objects and background galaxies. Subsequently, we performed a detailed spectroscopic analysis of the remaining candidates to estimate their stellar parameters such as effective temperature, surface gravity (logg), metallicity ([Fe/H]), reddening and their luminosities. This resulted in a sample of 35 likely post-AGB candidates with late-G to late-A spectral types, low logg, and [Fe/H]<-0.5. Furthermore, our study con- firmed the existence of the dusty post-Red Giant Branch (post-RGB) stars, discovered previously in our SMC survey, by revealing 119 such objects in the LMC. These objects have mid-IR excesses and stellar parameters (Teff, logg, [Fe/H]) similar to those of post-AGB stars except that their luminosities (<2500L_{sun}_), and hence masses and radii, are lower. These post-RGB stars are likely to be products of binary interaction on the RGB. The post-AGB and post-RGB objects show SED properties similar to the Galactic post-AGB stars, where some have a surrounding circumstellar shell, while some others have a surrounding stable disc similar to the Galactic post-AGB binaries. This study also resulted in a new sample of 162 young stellar objects, identified based on a robust logg criterion. Other interesting outcomes include objects with an UV continuum and an emission line spectrum; luminous supergiants; hot main-sequence stars; and 15 B[e] star candidates, 12 of which are newly discovered in this study.
- ID:
- ivo://CDS.VizieR/J/AJ/136/18
- Title:
- LMC SAGE. New candidate YSOs
- Short Name:
- J/AJ/136/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present ~1000 new candidate Young Stellar Objects (YSOs) in the Large Magellanic Cloud selected from Spitzer Space Telescope data, as part of the Surveying the Agents of a Galaxy's Evolution (SAGE) Legacy program. The YSOs, detected by their excess infrared (IR) emission, represent early stages of evolution, still surrounded by disks and/or infalling envelopes. Previously, fewer than 20 such YSOs were known. The candidate YSOs were selected from the SAGE Point Source Catalog from regions of color-magnitude space least confused with other IR-bright populations.
