485 research outputs found
Astrometric and photometric initial mass functions from the UKIDSS Galactic Clusters Survey - II. The Alpha Persei open cluster
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2012 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We present the results of a deep (J = 19.1mag) infrared (ZYJHK) survey over the full α Per open cluster extracted from the Data Release 9 of the United Kingdom Infrared Telescope Infrared Deep Sky Survey Galactic Clusters Survey (UKIDSS). We have selected ∼700 cluster member candidates in ∼56 square degrees in α Per by combining photometry in five near-infrared passbands and proper motions derived from the multiple epochs provided by the UKIDSS Galactic Clusters Survey (GCS) Data Release 9 (DR9). We also provide revised membership for all previously published α Per low-mass stars and brown dwarfs recovered in GCS based on the new photometry and astrometry provided by DR9. We find no evidence of K-band variability in members of α Per with dispersion less than 0.06-0.09mag. We employed two independent but complementary methods to derive the cluster luminosity and mass functions: a probabilistic analysis and a more standard approach consisting of stricter astrometric and photometric cuts. We find that the resulting luminosity and mass functions obtained from both methods are consistent. We find that the shape of the α Per mass function is similar to that of the Pleiades although the characteristic mass may be higher after including higher mass data from earlier studies (the dispersion is comparable). We conclude that the mass functions of α Per, the Pleiades and Praesepe are best reproduced by a log-normal representation similar to the system field mass function although with some variation in the characteristic mass and dispersion values.Peer reviewe
The spectral type of CHS7797 - an intriguing very low mass periodic variable in the Orion Nebula Cluster
We present the spectroscopic characterization of the unusual high-amplitude
very low mass pre-main-sequence periodic variable CHS7797. This study is based
on optical medium-resolution (R=2200) spectroscopy in the 6450-8600 A range,
carried out with GMOS-GEMINI-S in March 2011. Observations of CHS7797 have been
carried out at two distinct phases of the 17.8d period, namely at maximum and
four days before maximum. Four different spectral indices were used for the
spectral classification at these two phases, all of them well-suited for
spectral classification of young and obscured late M dwarfs. In addition, the
gravity-sensitive NaI (8183/8195 A) and KI (7665/7699 A) doublet lines were
used to confirm the young age of CHS7797. From the spectrum obtained at maximum
light we derived a spectral type (SpT) of M6.05, while for the spectrum taken
four days before maximum the derived SpT is M5.75. The derived SpTs confirm
that CHS7797 has a mass in the stellar-substellar boundary mass range. In
addition, the small differences in the derived SpTs at the two observed phases
may provide indirect hints that CHS7797 is a binary system of similar mass
components surrounded by a tilted circumbinary disk, a system similar to KH15D.Comment: 6 pages, accepted for publication A&
Spectroscopy of Hyades L dwarf candidates
We present the results of photometric, astrometric, and spectroscopic
follow-up of L dwarf candidates identified in the Hyades cluster by Hogan et
al. (2008). We obtained low-resolution optical spectroscopy with the OSIRIS
spectrograph on the Gran Telescopio de Canarias for all 12 L dwarf candidates
as well as new J-band imaging for a subsample of eight to confirm their proper
motion. We also present mid-infrared photometry from the Wise Field Infrared
Survey Explorer (WISE) for the Hyades L and T dwarf candidates and estimate
their spectroscopic distances, effective temperatures, and masses. We confirm
the cool nature of several L dwarf candidates and confirm astrometrically their
membership, bridging the gap between the coolest M dwarfs and the two T dwarfs
previously reported in the Hyades cluster. These members represent valuable
spectral templates at an age of 625 Myr and slightly super solar metallicity
(Fe/H=+0.13). We update the Hyades mass function across the hydrogen-burning
limit and in the substellar regime. We confirm a small number numbers of
very-low-mass members below ~0.1 Msun belonging to the Hyades cluster.Comment: 12 pages, 7 figures, 3 tables; accepted for publication in MNRA
The substellar mass function in the central region of the open cluster Praesepe from deep LBT observations
Studies of the mass function (MF) of open clusters of different ages allow us
to probe the efficiency with which brown dwarfs (BDs) are evaporated from
clusters to populate the field. Surveys in old clusters (age > 100 Myr) do not
suffer so severely from several problems encountered in young clusters, such as
intra-cluster extinction and large uncertainties in BD models. Here we present
the results of a deep photometric survey to study the MF of the old open
cluster Praesepe (age 590 Myr and distance 190 pc), down to a 5 sigma detection
limit at i~25.6 mag (~40M_Jup). We identify 62 cluster member candidates, of
which 40 are substellar, from comparison with predictions from a dusty
atmosphere model. The MF rises from the substellar boundary until ~60M_Jup and
then declines. This is quite different from the form inferred for other open
clusters older than 50 Myr, but seems to be similar to those found in very
young open cluster, whose MFs peak at ~10M_Jup. Either Praesepe really does
have a different MF from other clusters or they had similar initial MFs but
have differed in their dynamical evolution. We further have identified six
foreground T dwarf candidates towards Praesepe, which require follow-up
spectroscopy to confirm their nature.Comment: 8 pages, 5 figures, to appear in the online proceedings of the Cool
Stars 16 conferenc
Impact of genetic counseling and Connexin-26 and Connexin-30 testing on deaf identity and comprehension of genetic test results in a sample of deaf adults: A prospective, longitudinal study
Using a prospective, longitudinal study design, this paper addresses the impact of genetic counseling and testing for deafness on deaf adults and the Deaf community. This study specifically evaluated the effect of genetic counseling and Connexin-26 and Connexin-30 genetic test results on participants' deaf identity and understanding of their genetic test results. Connexin-26 and Connexin-30 genetic testing was offered to participants in the context of linguistically and culturally appropriate genetic counseling. Questionnaire data collected from 209 deaf adults at four time points (baseline, immediately following pre-test genetic counseling, 1-month following genetic test result disclosure, and 6-months after result disclosure) were analyzed. Four deaf identity orientations (hearing, marginal, immersion, bicultural) were evaluated using subscales of the Deaf Identity Development Scale-Revised. We found evidence that participants understood their specific genetic test results following genetic counseling, but found no evidence of change in deaf identity based on genetic counseling or their genetic test results. This study demonstrated that culturally and linguistically appropriate genetic counseling can improve deaf clients' understanding of genetic test results, and the formation of deaf identity was not directly related to genetic counseling or Connexin-26 and Connexin-30 genetic test results.CGSP received funding from the National Human Genome Research Institute (Ethical, Legal, and Social Issues Branch) (R01 HG003871, http://projectreporter.nih.gov); and from the Brocher Foundation (http://www.brocher.ch/en/brocher-fundati???on-in-brief/) in support of this research. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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