- ID:
- ivo://CDS.VizieR/J/AJ/152/75
- Title:
- Photometric survey of IC 2391, {eta} Cha, and USco
- Short Name:
- J/AJ/152/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The past two decades have seen a significant advancement in the detection, classification, and understanding of exoplanets and binaries. This is due, in large part, to the increase in use of small-aperture telescopes (<20cm) to survey large areas of the sky to milli-mag precision with rapid cadence. The vast majority of the planetary and binary systems studied to date consists of main-sequence or evolved objects, leading to a dearth of knowledge of properties at early times (<50Myr). Only a dozen binaries and one candidate transiting Hot Jupiter are known among pre-main-sequence objects, yet these are the systems that can provide the best constraints on stellar formation and planetary migration models. The deficiency in the number of well characterized systems is driven by the inherent and aperiodic variability found in pre-main-sequence objects, which can mask and mimic eclipse signals. Hence, a dramatic increase in the number of young systems with high-quality observations is highly desirable to guide further theoretical developments. We have recently completed a photometric survey of three nearby (<150pc) and young (<50Myr) moving groups with a small-aperture telescope. While our survey reached the requisite photometric precision, the temporal coverage was insufficient to detect Hot Jupiters. Nevertheless, we discovered 346 pre-main-sequence binary candidates, including 74 high-priority objects for further study.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/144/125
- Title:
- Photometry and spectroscopy of Markarian 266
- Short Name:
- J/AJ/144/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results of observations with the Spitzer, Hubble, GALEX, Chandra, and XMM-Newton space telescopes are presented for the luminous infrared galaxy (LIRG) merger Markarian 266. The SW (Seyfert 2) and NE (LINER) nuclei reside in galaxies with Hubble types SBb (pec) and S0/a (pec), respectively. Both companions are more luminous than L* galaxies and they are inferred to each contain a {approx}2.5x10^8^M_{sun}_ black hole. Although the nuclei have an observed hard X-ray flux ratio of f_X_(NE)/f_X_(SW)=6.4, Mrk 266 SW is likely the primary source of a bright Fe K{alpha} line detected from the system, consistent with the reflection-dominated X-ray spectrum of a heavily obscured active galactic nucleus (AGN). Optical knots embedded in an arc with aligned radio continuum radiation, combined with luminous H_2_line emission, provide evidence for a radiative bow shock in an AGN-driven outflow surrounding the NE nucleus. A soft X-ray emission feature modeled as shock-heated plasma with T~10^7^K is cospatial with radio continuum emission between the galaxies. Mid-infrared diagnostics provide mixed results, but overall suggest a composite system with roughly equal contributions of AGN and starburst radiation powering the bolometric luminosity. Approximately 120 star clusters have been detected, with most having estimated ages less than 50Myr. Detection of 24{mu}m emission aligned with soft X-rays, radio continuum, and ionized gas emission extending ~34" (20kpc) north of the galaxies is interpreted as ~2x10^7^M_{sun}_ of dust entrained in an outflowing superwind. At optical wavelengths this Northern Loop region is resolved into a fragmented morphology indicative of Rayleigh-Taylor instabilities in an expanding shell of ionized gas. Mrk 266 demonstrates that the dust "blow-out" phase can begin in a LIRG well before the galaxies fully coalesce during a subsequent ultraluminous infrared galaxy (ULIRG) phase, and rapid gas consumption in luminous dual AGNs with kiloparsec-scale separations early in the merger process may explain the paucity of detected binary QSOs (with parsec-scale orbital separations) in spectroscopic surveys. An evolutionary sequence is proposed representing a progression from dual to binary AGNs, accompanied by an increase in observed L_x_/L_ir_ ratios by over two orders of magnitude.
- ID:
- ivo://CDS.VizieR/J/AJ/127/660
- Title:
- Photometry in southern tail of the Antennae
- Short Name:
- J/AJ/127/660
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the Hubble Space Telescope and Wide Field Planetary Camera 2 to image the putative tidal dwarf galaxy located at the tip of the Southern tidal tail of NGC 4038/4039, the Antennae. We resolve individual stars and identify two stellar populations. Hundreds of massive stars are present, concentrated into tight OB associations on scales of 200pc, with ages ranging from 2 to 100Myr. An older stellar population is distributed roughly following the outer contours of the neutral hydrogen in the tidal tail; we associate these stars with material ejected from the outer disks of the two spirals. The older stellar population has a red giant branch tip at I=26.5+/-0.2 from which we derive a distance modulus (m-M)_0_=30.7+/-0.25. The implied distance of 13.8+/-1.7Mpc is significantly smaller than commonly quoted distances for NGC 4038/4039. In contrast to the previously studied core of the merger, we find no superstar clusters (SSCs).
- ID:
- ivo://CDS.VizieR/J/ApJ/468/633
- Title:
- Photometry in the M31 OB association NGC 206
- Short Name:
- J/ApJ/468/633
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of our effort to determine what affects the star formation process by looking at the products of that process, we have obtained broadband Hubble Space Telescope images of the large OB association NGC 206 in the nearby spiral galaxy M31. Our images cover approximately the southern half of the association. We have detected stars down to an F555W magnitude of 25.5 and measure stars on the main sequence in NGC 206 to an M_F555W,0_ of -1 or a mass of ~6M_{sun}_. From a comparison with isochrones, ages up to about 8Myr are plausible, and we adopt an age of 6Myr. For stellar masses 6-15M_{sun}_, we determine an initial mass function slope of -1.4+/-0.5. This is close to the value for a Salpeter mass function, although the uncertainty is large. The uncertainty in the slope represents disagreement among the individual mass bins. In terms of intermediate-mass stars (6-15M_{sun}_) the NGC 206 star formation event appears to be typical of star formation processes in other nearby galaxies, and it is part of a growing number of studies ,that are finding similarities in the products of the star formation processes in a wide variety of star formation events and galactic environments. Nevertheless, the density of stars formed in NGC 206 is much lower than that in giant H II regions such as NGC 604 in M33 or 30 Doradus in the LMC and in typical OB associations.
- ID:
- ivo://CDS.VizieR/J/A+A/600/A83
- Title:
- Photometry of beta Pic members
- Short Name:
- J/A+A/600/A83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We intended to compile the most complete catalogue of bona fide members and candidate members of the beta Pictoris association, and to measure their rotation periods and basic properties from our own observations, from public archives, and exploring the literature. We have carried out a multi-observatories campaign to get our own photometric time series and collected all archived public photometric data time series for the stars in our catalogue. Each time series was analyzed with the Lomb-Scargle and CLEAN periodograms to search for the stellar rotation periods. The measured rotational properties have been complemented with detailed information on multiplicity, membership, and projected rotational velocity available in the literature and discussed star by star. We have measured the rotation periods of 112 out of 117 among bona fide members and candidate members of the beta Pictoris association and, whenever possible, also luminosity, radius, and inclination of the stellar rotation axis. This represents to date the largest catalogue of rotation periods of any young loose stellar association. We have provided an extensive catalogue of rotation periods together with other relevant basic properties useful to explore a number of open issues such as the causes of spread of rotation periods among coeval stars, the evolution of angular momentum, the lithium-rotation connection, among others.
- ID:
- ivo://CDS.VizieR/J/A+A/301/396
- Title:
- Photometry of NGC 1962-65-66-70
- Short Name:
- J/A+A/301/396
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD data in the Johnson passbands B and V of the young association NGC 1962-65-66-70 in the Large Magellanic Cloud.
- ID:
- ivo://CDS.VizieR/J/A+A/529/A25
- Title:
- Photometry of star clusters in 5 nearby gal.
- Short Name:
- J/A+A/529/A25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent studies have started to cast doubt on the assumption that most stars are formed in clusters. Observational studies of field stars and star cluster systems in nearby galaxies can lead to better constraints on the fraction of stars forming in clusters. Ultimately this may lead to a better understanding of star formation in galaxies, and galaxy evolution in general. We aim to constrain the amount of star formation happening in long-lived clusters for four galaxies through the homogeneous, simultaneous study of field stars and star clusters.
- ID:
- ivo://CDS.VizieR/J/AJ/151/126
- Title:
- Photometry of YSOs in eight bright-rimmed clouds
- Short Name:
- J/AJ/151/126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We carried out deep- and wide-field near- and mid-infrared observations for a sample of eight bright-rimmed clouds (BRCs). Supplemented with the Spitzer archival data, we have identified and classified 44 to 433 young stellar objects (YSOs) associated with these BRCs. The Class I sources are generally located toward the places with higher extinction and are relatively closer to each other than the Class II sources, confirming that the young protostars are usually found in regions with denser molecular material. On the other hand the comparatively older population, Class II objects, are more randomly found throughout the regions, which can be due to their dynamical evolution. Using the minimal sampling tree analyses, we have extracted 13 stellar cores of eight or more members, which contain 60% of the total YSOs. The typical core is ~0.6pc in radii and somewhat elongated (aspect ratio of 1.45), of relatively low stellar density (surface density 60pc^-2^), consisting of a small (35) number of YSOs of relatively young sources (66% Class I), and partially embedded (median A_K_=1.1mag). But the cores show a wide range in their mass distribution (~20 to 2400M_{Sun}_), with a median value of around 130M_{Sun}_. We found the star-formation efficiencies in the cores to be between 3% and 30% with an average of ~14%, which agrees with the efficiencies needed to link the core mass function to the initial mass function. We also found a linear relation between the density of the clouds and the number of YSOs. The peaked nearest neighbor spacing distributions of the YSOs and the ratio of Jeans lengths to the YSO separations indicates a significant degree of non-thermally driven fragmentation in these BRCs.
- ID:
- ivo://CDS.VizieR/J/A+A/643/A138
- Title:
- Possible runaway stars list
- Short Name:
- J/A+A/643/A138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectral classifications of the Galactic O-Star Spectroscopic Survey (GOSSS) and the astrometric and photometric data from Gaia have significantly improved our ability to measure distances and determine memberships of stellar groups (clusters, associations, or parts thereof) with OB stars. In the near future, the situation will be further improved thanks to subsequent Gaia data releases and new photometric and spectroscopic surveys. We initiated a program to identify and determine the membership of Galactic stellar groups with OB stars and measure distances to them. Given the data currently available, we started with the identification and distance determinations of groups with O stars. In this paper, we concentrate on groups that contain stars with the earliest spectral subtypes. We used GOSSS to select Galactic stellar groups with O2-O3.5 stars and the method described in paper 0 of this series, which combines Gaia DR2 G + G_BP_ + G_RP_ photometry, positions, proper motions, and parallaxes to assign robust memberships and measure distances. We also included Collinder 419 and NGC 2264, the clusters cited in that paper, to generate our first list of 16 O-type Galactic stellar groups. We derived distances, determined the membership, and analyzed the structure of sixteen Galactic stellar groups with O stars, Villafranca O-001 to Villafranca O-016, including the fourteen groups with the earliest-O-type optically accessible stars known in the Milky Way. We compared our distance with previous results from the literature and establish that the best consistency is with (the small number of) VLBI parallaxes and the worst is with kinematic distances. Our results indicate that very massive stars can form in relatively low-mass clusters or even in near-isolation, as is the case for the Bajamar star in the North America nebula. This lends support to the hierarchical scenario of star formation, where some stars are born in well-defined bound clusters but others are born in associations that are unbound from the beginning: groups of newborn stars come in many shapes and sizes. We propose that HD 64568 and HD 64315 AB could have been ejected simultaneously from Haffner 18 (Villafranca O-012 S). Our results are consistent with a difference of =~20{mu}as in the Gaia DR2 parallax zero point between bright and faint stars.
- ID:
- ivo://CDS.VizieR/J/AJ/124/1670
- Title:
- Post-T Tauri Stars in Sco-Cen Association
- Short Name:
- J/AJ/124/1670
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a spectroscopic survey of X-ray and proper-motion-selected samples of late-type stars in the Lower Centaurus-Crux (LCC) and Upper Centaurus-Lupus (UCL) subgroups of the nearest OB association: Scorpius-Centaurus. The primary goals of the survey are to determine the star formation history of the OB subgroups and to assess the frequency of accreting stars in a sample dominated by "post-T Tauri" pre-main-sequence (PMS) stars. We investigate two samples: (1) proper-motion candidates from the ACT Catalog (<I/246>) and Tycho Reference Catalog (TRC, <I/250>) with X-ray counterparts in the ROSAT All-Sky Survey (RASS) Bright Source Catalog and (2) G- and K-type stars in the Hipparcos catalog found to be candidate members by de Zeeuw et al. (1999, Cat. <J/AJ/117/354>). We obtained optical spectra of 130 candidates with the Siding Spring 2.3m dual-beam spectrograph.
