97 research outputs found
Use of a Portable Sawmill for Forestry Instruction
The Arthur Temple College of Forestry and Agriculture at Stephen F. Austin State University in Nacogdoches, TX, has implemented an experiential learning exercise to improve student learning related to the forest products industry. During the week-long sophomore- or junior-level course Harvesting and Processing, forestry students tour multiple wood products facilities such as sawmills. These mills use complex technologies to maximize the lumber produced from each log, and students were having difficulty understanding the underlying concepts. As part of this course beginning in 2012, students began working in teams to estimate the lumber that will be recovered from a log and then actually sawing their own log using a portable sawmill. Since the introduction of this experiential learning project, student comments, instructor observations, and an increase in the mean course grades suggest that the sawmill activity is not only popular among students, it also allows for a fun, competitive, and engaging way to prepare future natural resource managers for their careers
The GBT 350-MHz Drift Scan Pulsar Survey. III. Detection of a magnetic field in the eclipsing material of PSR J2256-1024
We present the first measurement of a non-zero magnetic field in the
eclipsing material of a black widow pulsar. Black widows are millisecond
pulsars which are ablating their companions; therefore they are often proposed
as one potential source of isolated millisecond pulsars. PSR J2256-1024 is an
eclipsing black widow discovered at radio wavelengths and later also observed
in the X-ray and gamma parts of the spectrum. Here we present the radio timing
solution for PSR J2256-1024, polarization profiles at 350, 820, and 1500~MHz
and an investigation of changes in the polarization profile due to eclipsing
material in the system. In the latter we find evidence of Faraday rotation in
the linear polarization shortly after eclipse, measuring a rotation measure of
0.44(6) rad per meter squared and a corresponding line-of-sight magnetic field
of 3.5(17) mG.Comment: 14 pages, 8 figure
Multi-Messenger Gravitational Wave Searches with Pulsar Timing Arrays: Application to 3C66B Using the NANOGrav 11-year Data Set
When galaxies merge, the supermassive black holes in their centers may form
binaries and, during the process of merger, emit low-frequency gravitational
radiation in the process. In this paper we consider the galaxy 3C66B, which was
used as the target of the first multi-messenger search for gravitational waves.
Due to the observed periodicities present in the photometric and astrometric
data of the source of the source, it has been theorized to contain a
supermassive black hole binary. Its apparent 1.05-year orbital period would
place the gravitational wave emission directly in the pulsar timing band. Since
the first pulsar timing array study of 3C66B, revised models of the source have
been published, and timing array sensitivities and techniques have improved
dramatically. With these advances, we further constrain the chirp mass of the
potential supermassive black hole binary in 3C66B to less than using data from the NANOGrav 11-year data set. This
upper limit provides a factor of 1.6 improvement over previous limits, and a
factor of 4.3 over the first search done. Nevertheless, the most recent orbital
model for the source is still consistent with our limit from pulsar timing
array data. In addition, we are able to quantify the improvement made by the
inclusion of source properties gleaned from electromagnetic data to `blind'
pulsar timing array searches. With these methods, it is apparent that it is not
necessary to obtain exact a priori knowledge of the period of a binary to gain
meaningful astrophysical inferences.Comment: 14 pages, 6 figures. Accepted by Ap
The NANOGrav 11-Year Data Set: Arecibo Observatory Polarimetry And Pulse Microcomponents
We present the polarization pulse profiles for 28 pulsars observed with the
Arecibo Observatory by the North American Nanohertz Observatory for
Gravitational Waves (NANOGrav) timing project at 2.1 GHz, 1.4 GHz, and 430 MHz.
These profiles represent some of the most sensitive polarimetric millisecond
pulsar profiles to date, revealing the existence of microcomponents (that is,
pulse components with peak intensities much lower than the total pulse peak
intensity). Although microcomponents have been detected in some pulsars
previously, we present microcomponents for PSRs B1937+21, J1713+0747, and
J2234+0944 for the first time. These microcomponents can have an impact on
pulsar timing, geometry, and flux density determination. We present rotation
measures for all 28 pulsars, determined independently at different observation
frequencies and epochs, and find the Galactic magnetic fields derived from
these rotation measures to be consistent with current models. These
polarization profiles were made using measurement equation template matching,
which allows us to generate the polarimetric response of the Arecibo
Observatory on an epoch-by-epoch basis. We use this method to describe its time
variability, and find that the polarimetric responses of the Arecibo
Observatory's 1.4 and 2.1 GHz receivers vary significantly with time.Comment: 41 pages, 20 figure
The Green Bank North Celestial Cap Pulsar Survey. III. 45 New Pulsar Timing Solutions
We provide timing solutions for 45 radio pulsars discovered by the Robert C. Byrd Green Bank Telescope. These pulsars were found in the Green Bank North Celestial Cap pulsar survey, an all-GBT-sky survey being carried out at a frequency of 350 MHz. We include pulsar timing data from the Green Bank Telescope and Low Frequency Array. Our sample includes five fully recycled millisecond pulsars (MSPs, three of which are in a binary system), a new relativistic double neutron star system, an intermediate-mass binary pulsar, a mode-changing pulsar, a 138 ms pulsar with a very low magnetic field, and several nulling pulsars. We have measured two post-Keplerian parameters and thus the masses of both objects in the double neutron star system. We also report a tentative companion mass measurement via Shapiro delay in a binary MSP. Two of the MSPs can be timed with high precision and have been included in pulsar timing arrays being used to search for low-frequency gravitational waves, while a third MSP is a member of the black widow class of binaries. Proper motion is measurable in five pulsars, and we provide an estimate of their space velocity. We report on an optical counterpart to a new black widow system and provide constraints on the optical counterparts to other binary MSPs. We also present a preliminary analysis of nulling pulsars in our sample. These results demonstrate the scientific return of long timing campaigns on pulsars of all types
The NANOGrav 12.5-Year Data Set: Polarimetry and Faraday Rotation Measures from Observations of Millisecond Pulsars with the Green Bank Telescope
In this work, we present polarization profiles for 23 millisecond pulsars
observed at 820 MHz and 1500 MHz with the Green Bank Telescope as part of the
NANOGrav pulsar timing array. We calibrate the data using Mueller matrix
solutions calculated from observations of PSRs B1929+10 and J1022+1001. We
discuss the polarization profiles, which can be used to constrain pulsar
emission geometry, and present both the first published radio polarization
profiles for nine pulsars and the discovery of very low intensity average
profile components ("microcomponents") in four pulsars. Using the Faraday
rotation measures, we measure for each pulsar and use it to calculate the
Galactic magnetic field parallel to the line of sight for different lines of
sight through the interstellar medium. We fit for linear and sinusoidal trends
in time in the dispersion measure and Galactic magnetic field and detect
magnetic field variations with a period of one year in some pulsars, but
overall find that the variations in these parameters are more consistent with a
stochastic origin.Comment: 35 pages, 21 figures. Accepted to Ap
Bayesian Solar Wind Modeling with Pulsar Timing Arrays
Using Bayesian analyses we study the solar electron density with the NANOGrav
11-year pulsar timing array (PTA) dataset. Our model of the solar wind is
incorporated into a global fit starting from pulse times-of-arrival. We
introduce new tools developed for this global fit, including analytic
expressions for solar electron column densities and open source models for the
solar wind that port into existing PTA software. We perform an ab initio
recovery of various solar wind model parameters. We then demonstrate the
richness of information about the solar electron density, , that can be
gleaned from PTA data, including higher order corrections to the simple
model associated with a free-streaming wind (which are informative probes of
coronal acceleration physics), quarterly binned measurements of and a
continuous time-varying model for spanning approximately one solar cycle
period. Finally, we discuss the importance of our model for chromatic noise
mitigation in gravitational-wave analyses of pulsar timing data and the
potential of developing synergies between sophisticated PTA solar electron
density models and those developed by the solar physics community.Comment: 22 pages, 7 figures, Submitted to Ap
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