- ID:
- ivo://CDS.VizieR/J/ApJ/782/8
- Title:
- Spectroscopy of 104 objects in the ONC
- Short Name:
- J/ApJ/782/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed low-resolution (R~40) near-infrared (0.9-2.4{mu}m) multi-object spectroscopy of 240 isolated point sources having apparent H-band magnitudes between 9 and 18 in the central 5'x6' of the Orion Trapezium cluster. The observations were performed over four nights at the Canada-France-Hawaii Telescope using the visiting instrument SIMON, an infrared imager and multi-object spectrograph. We present the spectra of 104 objects with accurately derived spectral types including 7 new objects having masses below the hydrogen-burning limit, and 6 objects with masses below the deuterium-burning limit. The spectral classification is performed by fitting previously classified spectral templates of dwarf stars (K4-M3) and optically classified young stellar and substellar objects (M4-L0), to the entire 0.9-2.4{mu}m spectral energy distribution in order to assign a spectral type and visual extinction for each object. Of the 104 objects studied, 44 have been previously classified spectroscopically using various techniques. We perform a rigorous comparison between the previous classifications and our own and find them to be in good agreement. Using the dereddened H-band magnitudes, the classified objects are used to create an Hertzsprung-Russell diagram for the cluster. We find that the previous age estimates of ~1Myr to be consistent with our results. Consistent with previous studies, numerous objects are observed to have luminosities several magnitudes above the 1Myr isochrone. Numerous objects exhibiting emission features in the J band are also reported.
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- ID:
- ivo://CDS.VizieR/J/ApJ/691/1387
- Title:
- Spectroscopy of the Galactic bar. I.
- Short Name:
- J/ApJ/691/1387
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use Fabry-Perot absorption line imaging spectroscopy to measure radial velocities using the CaII line in 3360 stars toward three lines of sight in the Milky Way's bar: Baade's Window and offset position at (l,b)~(+/-5.0,-3.5{deg}). This sample includes 2488 bar red clump giants, 339 bar M/K-giants, and 318 disk main-sequence stars. We measure the first four moments of the stellar velocity distribution of the red clump giants, and find it to be symmetric and flat-topped. We also measure the line-of-sight average velocity and dispersion of the red clump giants as a function of distance in the bar.
- ID:
- ivo://CDS.VizieR/J/A+A/645/A100
- Title:
- SPECULOOS. Ultracool dwarf transit survey
- Short Name:
- J/A+A/645/A100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One of the most promising avenues for the detailed study of temperate Earth-sized exoplanets is the detection of such planets in transit in front of stars that are small and near enough to make it possible to carry out a thorough atmospheric characterisation with next-generation telescopes, such as the James Webb Space telescope (JWST) or Extremely Large Telescope (ELT). In this context, the TRAPPIST-1 planets form a unique benchmark system that has garnered the interest of a large scientific community. The SPECULOOS survey is an exoplanet transit survey targeting a volume-limited (40pc) sample of ultracool dwarf stars (of spectral type M7 and later) that is based on a network of robotic 1m telescopes especially designed for this survey. The strategy for brighter and earlier targets leverages its synergy with the ongoing TESS space-based exoplanet transit survey. We define the SPECULOOS target list as the sum of three non-overlapping sub-programmes incorporating the latest type objects (Teff<3000K). Programme1 features 365 dwarfs that are small and near enough to make it possible to detail atmospheric characterisation of an 'Earth-like' planet with the upcoming James Webb Space Telescope (JWST). Programme2 features 171 dwarfs of M5-type and later for which a significant detection of a planet similar to TRAPPIST-1b should be within reach of TESS. Programme3 features 1121 dwarfs that are later than M6-type. These programmes form the basis of our statistical census of short-period planets around ultracool dwarf stars. Our compound target list includes 1657 photometrically classified late-type dwarfs, with 260 of these targets classified, for the first time, as possible nearby ultracool dwarf stars. Our general observational strategy was to monitor each target between 100 and 200hr with our telescope network, making efficient use of the synergy with TESS for our Programme2 targets and a proportion of targets in our Programme1. Based on Monte Carlo simulations, we expect to detect up to a few dozen temperate, rocky planets. We also expect a number of them to prove amenable for atmospheric characterisation with JWST and other future giant telescopes, which will substantially improve our understanding of the planetary population of the latest-type stars.
- ID:
- ivo://CDS.VizieR/J/AJ/147/34
- Title:
- SpeX library of L-type dwarfs
- Short Name:
- J/AJ/147/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of the L dwarf WISE J174102.78-464225.5, which was discovered as part of a search for nearby L dwarfs using the Wide-field Infrared Survey Explorer (WISE). The distinct triangular peak of the H-band portion of its near-infrared spectrum and its red near-infrared colors (J-K_S_=2.35+/-0.08mag) are indicative of a young age. Via comparison to spectral standards and other red L dwarfs, we estimate a near-infrared spectral type of L7+/-2 (pec). From a comparison to spectral and low-mass evolutionary models, we determine self-consistent effective temperature, logg, age, and mass values of 1450+/-100K, 4.0+/-0.25 (cm/s2), 10-100Myr, and 4-21M_Jup_, respectively. With an estimated distance of 10-30pc, we explore the possibility that WISE J174102.78-464225.5 belongs to one of the young nearby moving groups via a kinematic analysis and we find potential membership in the {beta} Pictoris or AB Doradus associations. A trigonometric parallax measurement and a precise radial velocity can help to secure its membership in either of these groups.
- ID:
- ivo://CDS.VizieR/J/ApJ/651/502
- Title:
- Spitzer IRAC photometry of M, L, and T dwarfs
- Short Name:
- J/ApJ/651/502
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a program to acquire photometry for 86 late M, L, and T dwarfs using the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. We examine the behavior of these cool dwarfs in various color-color and color-magnitude diagrams composed of near-IR and IRAC data.
- ID:
- ivo://CDS.VizieR/J/ApJ/653/675
- Title:
- Spitzer 24{mu}m photometry of A dwarfs
- Short Name:
- J/ApJ/653/675
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report 24 and/or 70um measurements of ~160 A-type main-sequence stars using the Multiband Imaging Photometer for Spitzer (MIPS).
- ID:
- ivo://CDS.VizieR/J/ApJ/620/1010
- Title:
- Spitzer 24{mu}m photometry of A dwarfs
- Short Name:
- J/ApJ/620/1010
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report new Spitzer 24{mu}m photometry of 76 main-sequence A-type stars. We combine these results with previously reported Spitzer 24{mu}m data and 24 and 25{mu}m photometry from the Infrared Space Observatory and the Infrared Astronomy Satellite. The result is a sample of 266 stars with mass close to 2.5M_Sun_ all detected to at least the ~7{sigma} level relative to their photospheric emission.
- ID:
- ivo://CDS.VizieR/J/AJ/144/135
- Title:
- Spitzer 24{mu}m photometry of Hipparcos F stars
- Short Name:
- J/AJ/144/135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a study of debris disks around F stars in order to explore correlations between rotation, stellar winds, and circumstellar disks. We obtained new 24{mu}m photometry from the Multiband Imaging Photometer for Spitzer (MIPS) camera for a sample of 188 relatively nearby F dwarfs with various rotation rates and optical colors, and combined it with archival MIPS data for 66 more F stars, as well as Wide-field Infrared Survey Explorer data for the entire sample, plus 9 more F stars. Based on the objects' K_s_-[24] and [3.4]-[22] colors, we identify 22 stars in our sample as having 22 and/or 24{mu}m excesses above our detection limit, 13 of which are new discoveries. Our overall disk detection rate is 22/263, or 8%, consistent with previous determinations of disk fractions in the solar neighborhood. While fast-rotating stars are expected to have strong winds capable of efficiently removing dust, we find no correlation between rotational velocity and infrared excess. Similarly, we find no significant difference in excess detection rate between late-type F stars, which have convective surfaces, and early-type F stars, which have fully radiative envelopes. However, the essentially unknown range of ages in this sample may be washing out any effects relating rotation, winds, and disks.
- ID:
- ivo://CDS.VizieR/J/ApJ/679/720
- Title:
- Spitzer observations of the Hyades
- Short Name:
- J/ApJ/679/720
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the Spitzer Space Telescope to search for infrared excess at 24, 70, and 160um due to debris disks around a sample of 45 FGK-type members of the Hyades. We supplement our observations with archival 24 and 70um Spitzer data of an additional 22 FGK-type and 11 A-type Hyades members in order to provide robust statistics on the incidence of debris disks at 625Myr of age, an era corresponding to the late heavy bombardment in the solar system. We find that none of the 67 FGK-type stars in our sample show evidence for a debris disk, while 2 out of the 11 A-type stars do. This difference in debris disk detection rate is likely to be due to a sensitivity bias in favor of early-type stars. The fractional disk luminosity, L_dust_/L_*_, of the disks around the two A-type stars is ~4x10^-5^, a level that is below the sensitivity of our observations toward the FGK-type stars. However, our sensitivity limits for FGK-type stars are able to exclude, at the 2{sigma} level, frequencies higher than 12% and 5% of disks with L_dust_/L_*_>1x10^-4^ and L_dust_/L_*_>5x10^-4^, respectively. We also use our sensitivity limits and debris disk models to constrain the maximum mass of dust, as a function of distance from the stars, that could remain undetected around our targets.
- ID:
- ivo://CDS.VizieR/J/ApJ/794/159
- Title:
- Statistical analysis of exoplanet surveys
- Short Name:
- J/ApJ/794/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conduct a statistical analysis of a combined sample of direct imaging data, totalling nearly 250 stars. The stars cover a wide range of ages and spectral types, and include five detections ({kappa} And b, two ~60 M_J_ brown dwarf companions in the Pleiades, PZ Tel B, and CD-35 2722B). For some analyses we add a currently unpublished set of SEEDS observations, including the detections GJ 504b and GJ 758B. We conduct a uniform, Bayesian analysis of all stellar ages using both membership in a kinematic moving group and activity/rotation age indicators. We then present a new statistical method for computing the likelihood of a substellar distribution function. By performing most of the integrals analytically, we achieve an enormous speedup over brute-force Monte Carlo. We use this method to place upper limits on the maximum semimajor axis of the distribution function derived from radial-velocity planets, finding model-dependent values of ~30-100 AU. Finally, we model the entire substellar sample, from massive brown dwarfs to a theoretically motivated cutoff at ~5 M_J_, with a single power-law distribution. We find that p(M,a){prop.to}M^-0.65+/-0.60^a^-0.85+/-0.39^ (1{sigma} errors) provides an adequate fit to our data, with 1.0%-3.1% (68% confidence) of stars hosting 5-70 M_J_ companions between 10 and 100 AU. This suggests that many of the directly imaged exoplanets known, including most (if not all) of the low-mass companions in our sample, formed by fragmentation in a cloud or disk, and represent the low-mass tail of the brown dwarfs.
