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

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 J0317$-$853, 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

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

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