1,766 research outputs found
Reply to Comment on "Reevaluation of the parton distribution of strange quarks in the nucleon"
A Comment on the recently published reevaluation of the polarization-averaged
parton distribution of strange quarks in the nucleon using final data on the
multiplicities of charged kaons in semi-inclusive deep-inelastic scattering is
reviewed. Important features of the comparison of one-dimensional projections
of the multidimensional HERMES data are pointed out. A test of the
leading-order extraction of xS(x) using the difference between charged-kaon
multiplicities is repeated. The results are consistent with leading-order
predictions within the uncertainties in the input data, and do not invalidate
the earlier extraction of xS(x).Comment: Reply Comment to arXiv:1407.372
Prenatal therapy in developmental disorders: drug targeting via intra-amniotic injection to treat X-linked hypohidrotic ectodermal dysplasia
Research in the general area of non-linear dynamical systems Final report, 8 Jun. 1965 - 8 Jun. 1967
Nonlinear dynamical systems research on systems stability, invariance principles, Liapunov functions, and Volterra and functional integral equation
The Rapid Rotation of the Strongly Magnetic Ultramassive White Dwarf EGGR 156
The distribution of white dwarf rotation periods provides a means for
constraining angular momentum evolution during the late stages of stellar
evolution, as well as insight into the physics and remnants of double
degenerate mergers. Although the rotational distribution of low mass white
dwarfs is relatively well constrained via asteroseismology, that of high mass
white dwarfs, which can arise from either intermediate mass stellar evolution
or white dwarf mergers, is not. Photometric variability in white dwarfs due to
rotation of a spotted star is rapidly increasing the sample size of high mass
white dwarfs with measured rotation periods. We present the discovery of 22.4
minute photometric variability in the lightcurve of EGGR 156, a strongly
magnetic, ultramassive white dwarf. We interpret this variability as rapid
rotation, and our data suggest that EGGR 156 is the remnant of a double
degenerate merger. Finally, we calculate the rate of period change in rapidly
rotating, massive, magnetic WDs due to magnetic dipole radiation. In many
cases, including EGGR 156, the period change is not currently detectable over
reasonable timescales, indicating that these WDs could be very precise clocks.
For the most highly magnetic, rapidly rotating massive WDs, such as ZTF
J1901+1450 and RE J0317853, the period change should be detectable and may
help constrain the structure and evolution of these exotic white dwarfs.Comment: Replaced to correct two typos in equations on page 12. No
calculations or conclusions affected. 15 pages, 5 figures, accepted for
publication in the Astronomical Journa
Carbon and oxygen stable isotopic evidence for diverse sheep and goat husbandry strategies amid a Final Bronze Age farming milieu in the Kyrgyz Tian Shan
Abstract The mountains of Central Asia during the Bronze and Iron Ages are increasingly being reconceived as an important zone for intensive crop cultivation in combination with pastoralist herding. However, very little information is known about how farming practices intersected with livestock husbandry, especially at high-elevation sites. This paper presents the first insights to ancient animal management strategies in the Tian Shan through incremental carbon and oxygen stable isotope analysis of domesticated caprine teeth recovered from the Chap-1 farmstead located at 2000?m.a.s.l. in Kyrgyzstan (1065 to 825?cal?BCE). We implemented a fully reproducible analysis of time-series isotope data in the R programming language. Results show subtle but variable manipulation of domesticated caprine diets at subannual scales, suggesting mixed strategies of providing access to a small amount of C4 plant biomass, in addition to summer movements to high pastures where the overall carbon isotopic composition of graze was depleted in 13C compared with that of the environs of the site or lowland pastures. Nevertheless, caprine dietary intake was overwhelmingly dominated by C3 plants. Analysis of domesticated caprine birth seasonality reveals off-season fall and winter births, which represent a common strategy employed by ancient producers in Central Asia to improve herd security and extend meat and milk availability. This study illustrates a well-integrated system of agro-pastoralist production that can help clarify the social dynamics underlying food systems in the mountain regions of Central and Inner Asia in the Final Bronze Age. It further reveals the capability for more sedentary agro-pastoralist communities to facilitate wider interregional cultural connections, through limited seasonal herding mobility and investment in highland settlement.1 Introduction 2 Archaeology and enviroment of Chap-1 3 Material and methods 3.1 Study design and sample selection 3.2 Isotope mechanics 3.3 Isotopic analysis 3.4 Oxygen isotopic modelling and seasonal inference 4 Results 5 Discussion 5.1 Agricultural and pastoralist integration 5.2 Manipulation of animal births 5.3 Regional perspective 6 Conclusio
The Shortest Period Detached Binary White Dwarf System
We identify SDSS J010657.39-100003.3 (hereafter J0106-1000) as the shortest
period detached binary white dwarf (WD) system currently known. We targeted
J0106-1000 as part of our radial velocity program to search for companions
around known extremely low-mass (ELM, ~ 0.2 Msol) WDs using the 6.5m MMT. We
detect peak-to-peak radial velocity variations of 740 km/s with an orbital
period of 39.1 min. The mass function and optical photometry rule out a
main-sequence star companion. Follow-up high-speed photometric observations
obtained at the McDonald 2.1m telescope reveal ellipsoidal variations from the
distorted primary but no eclipses. This is the first example of a tidally
distorted WD. Modeling the lightcurve, we constrain the inclination angle of
the system to be 67 +- 13 deg. J0106-1000 contains a pair of WDs (0.17 Msol
primary + 0.43 Msol invisible secondary) at a separation of 0.32 Rsol. The two
WDs will merge in 37 Myr and most likely form a core He-burning single subdwarf
star. J0106-1000 is the shortest timescale merger system currently known. The
gravitational wave strain from J0106-1000 is at the detection limit of the
Laser Interferometer Space Antenna (LISA). However, accurate ephemeris and
orbital period measurements may enable LISA to detect J0106-1000 above the
Galactic background noise.Comment: MNRAS Letters, in pres
A Dark Spot on a Massive White Dwarf
We present the serendipitous discovery of eclipse-like events around the
massive white dwarf SDSS J152934.98+292801.9 (hereafter J1529+2928). We
selected J1529+2928 for time-series photometry based on its spectroscopic
temperature and surface gravity, which place it near the ZZ Ceti instability
strip. Instead of pulsations, we detect photometric dips from this white dwarf
every 38 minutes. Follow-up optical spectroscopy observations with Gemini
reveal no significant radial velocity variations, ruling out stellar and brown
dwarf companions. A disintegrating planet around this white dwarf cannot
explain the observed light curves in different filters. Given the short period,
the source of the photometric dips must be a dark spot that comes into view
every 38 min due to the rotation of the white dwarf. Our optical spectroscopy
does not show any evidence of Zeeman splitting of the Balmer lines, limiting
the magnetic field strength to B<70 kG. Since up to 15% of white dwarfs display
kG magnetic fields, such eclipse-like events should be common around white
dwarfs. We discuss the potential implications of this discovery on transient
surveys targeting white dwarfs, like the K2 mission and the Large Synoptic
Survey Telescope.Comment: ApJ Letters, in pres
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