Search and characterization of T-type planetary mass candidates in the Sigma Orionis cluster .

Figure caption:Upper panels: Proper motion diagrams for S Ori 70 (left, Omega 2000/HAWK-I data) and S Ori 73 (right, ISAAC/HAWK-I data). The two objects of interest are labelled. All identifiedsources within an area of 4 arcmin2 around the targets are plo
Figure caption:Upper panels: Proper motion diagrams for S Ori 70 (left, Omega 2000/HAWK-I data) and S Ori 73 (right, ISAAC/HAWK-I data). The two objects of interest are labelled. All identifiedsources within an area of 4 arcmin2 around the targets are plo
Advertised on
References
A&A, 2011, in press

The proper characterization of the least massive population of the young Sigma Orionis star cluster is required to understand the form of the cluster mass function and its impact on our comprehension of the substellar formation processes. S Ori 70 (T5.5+/-1) and 73, two T-type cluster member candidates, are likely to have masses between 3 and 7 MJup if their age is 3 Myr. It awaits confirmation whether S Ori 73 has a methane atmosphere. We aim to: i) confirm the presence of methane absorption in S Ori 73 by performing methane imaging; ii) study S Ori 70 and 73 cluster membership via photometric colors and accurate proper motion analysis; and iii) perform a new search to identify additional T-type Sigma Orionis member candidates. We obtained HAWK-I (VLT) J,H, and CH4off photometry of an area of 119.15 arcmin2 in Sigma Orionis down to Jcomp = 21.7 and Hcomp = 21 mag. S Ori 70 and 73 are contained in the explored area. Near-infrared data were complemented with optical photometry using images acquired with OSIRIS (GTC) and VISTA as part of the VISTA Orion survey. Color-magnitude and color-color diagrams were constructed to characterize S Ori 70 and 73 photometrically, and to identify new objects with methane absorption and masses below 7 MJup. We derived proper motions by comparing of the new HAWK-I and VISTA images with published near-infrared data taken 3.4?7.9 yr ago. S Ori 73 has a red H?CH4off color indicating methane absorption in the H-band and a spectral type of T4+/-1. S Ori 70 displays a redder methane color than S Ori 73 in agreement with its latter spectral classification. Our proper motion measurements are larger than the motion of Sigma Orionis, rendering S Ori 70 and 73 cluster membership uncertain. From our survey, we identified one new photometric candidate with J=21.69+/-0.12 mag and methane color consistent with spectral type > T8. S Ori 73 has colors similar to those of T3?T5 field dwarfs, which in addition to its high proper motion suggests that it is probably a field dwarf located at 170?200 pc. The origin of S Ori 70 remains unclear: it can be a field, foreground mid- to late-T free-floating dwarf with peculiar colors, or an orphan planet ejected through strong dynamical interactions from Sigma Orionis or from a nearby star-forming region in Orion.

News type
Research news

It may interest you

  • Research news
    On the magnetic nature of quiet-Sun chromospheric grains
    CaII Kgrains, i.e., intermittent, short-lived (about 1 minute), periodic (2-4 minutes), pointlike chromospheric brightenings, are considered to be the manifestations of acoustic waves propagating upward from the solar surface and developing into shocks in the chromosphere. After the simulations of Carlsson and Stein, we know that hot shocked gas moving upward interacting with the downflowing chromospheric gas (falling down after having been displaced upward by a previous shock) nicely reproduces the spectral features of the CaII K profiles observed in such grains, i.e., a narrowband emission
    Advertised on
  • RSOph_MWL_TransientsUniverse
    Research news
    A Very-High-Energy Gamma-Ray View of the Transient Sky
    The development of the latest generation of Imaging Atmospheric Cherenkov Telescopes (IACTs) over recent decades has led to the discovery of new extreme astrophysical phenomena in the very-high-energy (VHE, E > 100 GeV) gamma-ray regime. Time-domain and multi-messenger astronomy are inevitably connected to the physics of transient VHE emitters, which show unexpected (and mostly unpredictable) flaring or exploding episodes at different timescales. These transients often share the physical processes responsible for the production of the gamma-ray emission, through cosmic-ray acceleration
    Advertised on
  • Research news
    Scientific results with the QUIJOTE-MFI wide survey: The anomalous microwave emission in our Galaxy and M31
    In the 90s, the COBE satellite discovered that not all the microwave emission from our Galaxy behaved as expected. Part of this signal was later assigned to a fresh new emission component, spatially correlated with the Galactic dust emission, which showed greater importance in the microwave range of frequencies. It has been named since as “anomalous microwave emission”, or AME. The current main hypothesis to explain the AME origin is that it is emitted by small dust particles which undergo fast spinning movements. In Fernández-Torreiro et al. (2023), we study the observational properties of
    Advertised on