18 research outputs found
Three red suns in the sky: A transiting, terrestrial planet in a triple M-dwarf system at 6.9 pc
We present the discovery from Transiting Exoplanet Survey Satellite (TESS) data of LTT 1445Ab. At a distance of 6.9 pc, it is the second nearest transiting exoplanet system found to date, and the closest one known for which the primary is an M dwarf. The host stellar system consists of three mid-to-late M dwarfs in a hierarchical configuration, which are blended in one TESS pixel. We use MEarth data and results from the Science Processing Operations Center data validation report to determine that the planet transits the primary star in the system. The planet has a radius of , an orbital period of days, and an equilibrium temperature of K. With radial velocities from the High Accuracy Radial Velocity Planet Searcher, we place a 3σ upper mass limit of 8.4 on the planet. LTT 1445Ab provides one of the best opportunities to date for the spectroscopic study of the atmosphere of a terrestrial world. We also present a detailed characterization of the host stellar system. We use high-resolution spectroscopy and imaging to rule out the presence of any other close stellar or brown dwarf companions. Nineteen years of photometric monitoring of A and BC indicate a moderate amount of variability, in agreement with that observed in the TESS light-curve data. We derive a preliminary astrometric orbit for the BC pair that reveals an edge-on and eccentric configuration. The presence of a transiting planet in this system hints that the entire system may be co-planar, implying that the system may have formed from the early fragmentation of an individual protostellar core.Accepted manuscrip
The SDSS-III Baryon Oscillation Spectroscopic Survey: Quasar Target Selection for Data Release Nine
The SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), a five-year
spectroscopic survey of 10,000 deg^2, achieved first light in late 2009. One of
the key goals of BOSS is to measure the signature of baryon acoustic
oscillations in the distribution of Ly-alpha absorption from the spectra of a
sample of ~150,000 z>2.2 quasars. Along with measuring the angular diameter
distance at z\approx2.5, BOSS will provide the first direct measurement of the
expansion rate of the Universe at z > 2. One of the biggest challenges in
achieving this goal is an efficient target selection algorithm for quasars over
2.2 < z < 3.5, where their colors overlap those of stars. During the first year
of the BOSS survey, quasar target selection methods were developed and tested
to meet the requirement of delivering at least 15 quasars deg^-2 in this
redshift range, out of 40 targets deg^-2. To achieve these surface densities,
the magnitude limit of the quasar targets was set at g <= 22.0 or r<=21.85.
While detection of the BAO signature in the Ly-alpha absorption in quasar
spectra does not require a uniform target selection, many other astrophysical
studies do. We therefore defined a uniformly-selected subsample of 20 targets
deg^-2, for which the selection efficiency is just over 50%. This "CORE"
subsample will be fixed for Years Two through Five of the survey. In this paper
we describe the evolution and implementation of the BOSS quasar target
selection algorithms during the first two years of BOSS operations. We analyze
the spectra obtained during the first year. 11,263 new z>2.2 quasars were
spectroscopically confirmed by BOSS. Our current algorithms select an average
of 15 z > 2.2 quasars deg^-2 from 40 targets deg^-2 using single-epoch SDSS
imaging. Multi-epoch optical data and data at other wavelengths can further
improve the efficiency and completeness of BOSS quasar target selection.
[Abridged]Comment: 33 pages, 26 figures, 12 tables and a whole bunch of quasars.
Submitted to Ap
Another Shipment of Six Short-Period Giant Planets from TESS
We present the discovery and characterization of six short-period, transiting
giant planets from NASA's Transiting Exoplanet Survey Satellite (TESS) --
TOI-1811 (TIC 376524552), TOI-2025 (TIC 394050135), TOI-2145 (TIC 88992642),
TOI-2152 (TIC 395393265), TOI-2154 (TIC 428787891), & TOI-2497 (TIC 97568467).
All six planets orbit bright host stars (8.9 <G< 11.8, 7.7 <K< 10.1). Using a
combination of time-series photometric and spectroscopic follow-up observations
from the TESS Follow-up Observing Program (TFOP) Working Group, we have
determined that the planets are Jovian-sized (R = 1.00-1.45 R),
have masses ranging from 0.92 to 5.35 M, and orbit F, G, and K stars
(4753 T 7360 K). We detect a significant orbital eccentricity
for the three longest-period systems in our sample: TOI-2025 b (P = 8.872 days,
= ), TOI-2145 b (P = 10.261 days, =
), and TOI-2497 b (P = 10.656 days, =
). TOI-2145 b and TOI-2497 b both orbit subgiant host
stars (3.8 g 4.0), but these planets show no sign of inflation
despite very high levels of irradiation. The lack of inflation may be explained
by the high mass of the planets; M (TOI-2145
b) and M (TOI-2497 b). These six new discoveries
contribute to the larger community effort to use {\it TESS} to create a
magnitude-complete, self-consistent sample of giant planets with
well-determined parameters for future detailed studies.Comment: 20 Pages, 6 Figures, 8 Tables, Accepted by MNRA
The 2MASS Redshift Survey - Description and Data Release
We present the results of the 2MASS Redshift Survey (2MRS), a ten-year
project to map the full three-dimensional distribution of galaxies in the
nearby Universe. The 2 Micron All-Sky Survey (2MASS) was completed in 2003 and
its final data products, including an extended source catalog (XSC), are
available on-line. The 2MASS XSC contains nearly a million galaxies with Ks <=
13.5 mag and is essentially complete and mostly unaffected by interstellar
extinction and stellar confusion down to a galactic latitude of |b|=5 deg for
bright galaxies. Near-infrared wavelengths are sensitive to the old stellar
populations that dominate galaxy masses, making 2MASS an excellent starting
point to study the distribution of matter in the nearby Universe.
We selected a sample of 44,599 2MASS galaxies with Ks =5
deg (>= 8 deg towards the Galactic bulge) as the input catalog for our survey.
We obtained spectroscopic observations for 11,000 galaxies and used
previously-obtained velocities for the remainder of the sample to generate a
redshift catalog that is 97.6% complete to well-defined limits and covers 91%
of the sky. This provides an unprecedented census of galaxy (baryonic mass)
concentrations within 300 Mpc.
Earlier versions of our survey have been used in a number of publications
that have studied the bulk motion of the Local Group, mapped the density and
peculiar velocity fields out to 50 Mpc, detected galaxy groups, and estimated
the values of several cosmological parameters.
Additionally, we present morphological types for a nearly-complete sub-sample
of 20,860 galaxies with Ks = 10 deg.Comment: Accepted for publication in The Astrophysical Journal Supplement
Series. The 2MRS catalogs and a version of the paper with higher-resolution
figures can be found at http://tdc-www.harvard.edu/2mrs
Two Massive Jupiters in Eccentric Orbits from the TESS Full-frame Images
We report the discovery of two short-period massive giant planets from NASA's Transiting Exoplanet Survey Satellite (TESS). Both systems, TOI-558 (TIC 207110080) and TOI-559 (TIC 209459275), were identified from the 30 minute cadence full-frame images and confirmed using ground-based photometric and spectroscopic followup observations from TESS's follow-up observing program working group. We find that TOI-558 b, which transits an F-dwarf (M-* =1.349(-0.065)(+0.064) M-circle dot, R-* =1.496(-0.040)(+0.042) R-circle dot, T-eff = 6466(-93)(+95) K, age 1.79(-0.73)(+0.91) Gyr) with an orbital period of 14.574 days, has a mass of 3.61 +/- 0.15 M-J, a radius of 1.086(-0.038)(+0.041) R-J, and an eccentric (e = 0.300(-0.020)(+0.022)) orbit. TOI-559 b transits a G dwarf (M-* = 1.026 +/- 0.057 M-circle dot, R-* =1.233(-0.026)(+0.028) R-circle dot, T-eff = 5925(-76)(+85) K, age 6.8(-2.0)(+2.5) Gyr) in an eccentric (e = 0.151 +/- 0.011) 6.984 days orbit with a mass of 6.01(-0.23)(+0.24) M-J and a radius of 1.091(-0.025+)(0.028) R-J. Our spectroscopic follow up also reveals a long-term radial velocity trend for TOI-559, indicating a long-period companion. The statistically significant orbital eccentricity measured for each system suggests that these planets migrated to their current location through dynamical interactions. Interestingly, both planets are also massive (>3 M-J), adding to the population of massive giant planets identified by TESS. Prompted by these new detections of high-mass planets, we analyzed the known mass distribution of hot and warm Jupiters but find no significant evidence for multiple populations. TESS should provide a near magnitude-limited sample of transiting hot Jupiters, allowing for future detailed population studies