1,030 research outputs found
A search for hidden white dwarfs in the ROSAT EUV survey II: Discovery of a distant DA+F6/7V binary system in a direction of low density neutral hydrogen
We report the results of our final search for hot white dwarfs in unresolved,
Sirius-type, binary systems with IUE. One new system, RE J0500-364 (DA+F6/7V),
has been identified. This star appears to lie at a distance of between
500-1000pc, making it one of the most distant white dwarfs, if not the most
distant, to be detected in the EUV surveys. The very low line-of-sight neutral
hydrogen volume density to this object could place a lower limit on the length
of the Beta CMa interstellar tunnel of diffuse gas, which stretches away from
the Local Bubble in a similar direction to RE J0500-364.Comment: 1 LaTex file plus 15 figures; accepted for publication in Monthly
Notices of the Royal Astronomical Societ
A Near-Infrared Spectroscopic Study of the Accreting Magnetic White Dwarf SDSS J121209.31+013627.7 and its Substellar Companion
The nature of the excess near-infrared emission associated with the magnetic
white dwarf commonly known as SDSS 1212 is investigated primarily through
spectroscopy, and also via photometry. The inferred low mass secondary in this
system has been previously detected by the emission and variation of H,
and the m spectral data presented here are consistent with the
presence of a late L or early T dwarf. The excess flux seen beyond 1.5 m
in the phase-averaged spectrum is adequately modeled with an L8 dwarf
substellar companion and cyclotron emission in a 7 MG magnetic field. This
interesting system manifests several observational properties typical of
polars, and is most likely an old interacting binary with a magnetic white
dwarf and a substellar donor in an extended low state.Comment: 28 pages, 5 figures, Accepted to Ap
NLTT5306: The shortest Period Detached White Dwarf + Brown Dwarf Binary
We have spectroscopically confirmed a brown dwarf mass companion to the
hydrogen atmosphere white dwarf NLTT5306. The white dwarf's atmospheric
parameters were measured using Sloan Digital Sky Survey and X-Shooter
spectroscopy as T_eff=7756+/-35K and log(g)=7.68+/-0.08, giving a mass for the
primary of M_WD=0.44+/-0.04 M_sun, at a distance of 71+/-4 pc with a cooling
age of 710+/-50 Myr. The existence of the brown dwarf secondary was confirmed
through the near-infrared arm of the X-Shooter data and a spectral type of
dL4-dL7 was estimated using standard spectral indices. Combined radial velocity
measurements from the Sloan Digital Sky Survey, X-Shooter and the Hobby-Eberly
Telescope's High Resolution Spectrograph of the white dwarf gives a minimum
mass of 56+/-3 M_jup for the secondary, confirming the substellar nature. The
period of the binary was measured as 101.88+/-0.02 mins using both the radial
velocity data and i'-band variability detected with the INT. This variability
indicates 'day' side heating of the brown dwarf companion. We also observe
H{\alpha} emission in our higher resolution data in phase with the white dwarf
radial velocity, indicating this system is in a low level of accretion, most
likely via a stellar wind. This system represents the shortest period white
dwarf + brown dwarf binary and the secondary has survived a stage of common
envelope evolution, much like its longer period counterpart, WD0137-349. Both
systems likely represent bona-fide progenitors of cataclysmic variables with a
low mass white dwarf and a brown dwarf donor.Comment: 9 pages, 11 figures, accepted for publication in MNRA
PHL 5038: a spatially resolved white dwarf + brown dwarf binary
A near-infrared excess is detected at the white dwarf PHLâ5038 in UKIDSS photometry, consistent with the presence of a cool, substellar companion. We have obtained H- and K-grism spectra and images of PHLâ5038 using NIRI on Gemini North. The target is spatially and spectrally resolved into two components: an 8000 K DA white dwarf, and a likely L8 brown dwarf companion, separated by 0.94\arcsec. The spectral type of the secondary was determined using standard spectral indices for late L and T dwarfs. The projected orbital separation of the binary is 55 AU, so it becomes only the second known wide WD+dL binary to be found after GDâ165AB. This object could potentially be used as a benchmark for testing substellar evolutionary models at intermediate to older ages
Intelligent assistance in scientific data preparation
Scientific data preparation is the process of extracting usable scientific data from raw instrument data. This task involves noise detection (and subsequent noise classification and flagging or removal), extracting data from compressed forms, and construction of derivative or aggregate data (e.g. spectral densities or running averages). A software system called PIPE provides intelligent assistance to users developing scientific data preparation plans using a programming language called Master Plumber. PIPE provides this assistance capability by using a process description to create a dependency model of the scientific data preparation plan. This dependency model can then be used to verify syntactic and semantic constraints on processing steps to perform limited plan validation. PIPE also provides capabilities for using this model to assist in debugging faulty data preparation plans. In this case, the process model is used to focus the developer's attention upon those processing steps and data elements that were used in computing the faulty output values. Finally, the dependency model of a plan can be used to perform plan optimization and run time estimation. These capabilities allow scientists to spend less time developing data preparation procedures and more time on scientific analysis tasks
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