1,895 research outputs found
A New Large Super-Fast Rotator: (335433) 2005 UW163
Asteroids of size larger than 150 m generally do not have rotation periods
smaller than 2.2 hours. This spin cutoff is believed to be due to the
gravitationally bound rubble-pile structures of the asteroids. Rotation with
periods exceeding this critical value will cause asteroid breakup. Up until
now, only one object, 2001 OE84, has been found to be an exception to this spin
cutoff. We report the discovery of a new super-fast rotator, (335433) 2005
UW163, spinning with a period of 1.290 hours and a lightcurve variation of
mag from the observations made at the P48 telescope and the P200
telescope of the Palomar Observatory. Its mag and
multi-band colors (i.e., mag, mag
and SDSS mag) show it is a V-type asteroid with a diameter of
km. This indicates (335433) 2005 UW163 is a super-fast rotator
beyond the regime of the small monolithic asteroid.Comment: 18 pages, 4 figures, 1 table Accepted by ApJ
Early socialization of hostile attribution bias: The roles of parental attributions, parental discipline, and child attributes
The goal of this study was to examine child and parent predictors of childrenās hostile attribution bias (HAB) with a particular focus on exploring the associations between parentsā early attribution of child misbehavior and childrenās HAB in the transition to school age. Participants were 241 children (118 girls) of middleāincome families who were at risk for schoolāage conduct problems. Multiāmethod, multiāinformant data were collected on maternal attributions of child misbehavior, parental use of corporal punishment, and child attributes (i.e., verbal IQ, effortful control, theory of mind, and emotional understanding) at 3Ā years, and child HAB in ambiguous situations at 6Ā years. Results indicated that mothersā internal explanations for childrenās misconduct may either reduce or increase childrenās later HAB depending on the specific content of attributions, such that mothersā belief that children misbehave because of their internal state (i.e., emotional state or temperament) was associated with lower levels of child HAB, whereas attributing powerābased motives (i.e., manipulative, controlling intentions) in children was associated with higher levels of HAB. The findings are discussed with respect to appreciating the complexity of parentsā explanations for childrenās behavior, and considering parental cognition as a potential target for early identification and prevention of child HAB and related problems.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/150591/1/sode12349.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150591/2/sode12349_am.pd
Asteroid Spin-Rate Study using the Intermediate Palomar Transient Factory
Two dedicated asteroid rotation-period surveys have been carried out using
data taken on January 6-9 and February 20-23 of 2014 by the Intermediate
Palomar Transient Factory (iPTF) in the ~band with -min cadence.
The total survey area covered 174~deg in the ecliptic plane. Reliable
rotation periods for 1,438 asteroids are obtained from a larger data set of
6,551 mostly main-belt asteroids, each with ~detections. Analysis of
1751, PTF based, reliable rotation periods clearly shows the "spin barrier" at
~hours for "rubble-pile" asteroids. We also found a new large-sized
super-fast rotator, 2005 UW163 (Chang et al., 2014), and other five candidates
as well. Our spin-rate distributions of asteroids with ~km shows
number decrease when frequency greater than 5 rev/day, which is consistent to
that of the Asteroid Light Curve Database (LCDB, Warner et al., 2009) and the
result of (Masiero et al., 2009). We found the discrepancy in the spin-rate
distribution between our result and (Pravec et al., 2008, update 2014-04-20) is
mainly from asteroids with mag that might be primarily due to
different survey strategies. For asteroids with ~km, we found a
significant number drop at rev/day. The YORP effect timescale for
small-sized asteroid is shorter that makes more elongate objets spun up to
reach their spin-rate limit and results in break-up. The K-S test suggests a
possible difference in the spin-rate distributions of C- and S-type asteroids.
We also find that C-type asteroids have a smaller spin-rate limit than the
S-type, which agrees with the general sense that the C-type has lower bulk
density than the S-type.Comment: Submitted to ApJ (Jan, 2015). Accepted by ApJ (June, 2015). The whole
set of the folded lightcurves will be available on the published articl
313 new asteroid rotation periods from Palomar Transient Factory observations
A new asteroid rotation period survey have been carried out by using the
Palomar Transient Factory (PTF). Twelve consecutive PTF fields, which covered
an area of 87 deg in the ecliptic plane, were observed in band with a
cadence of 20 min during February 15--18, 2013. We detected 2500 known
asteroids with a diameter range of 0.5 km 200 km. Of these, 313
objects had highly reliable rotation periods and exhibited the "spin barrier"
at hours. In contrast to the flat spin rate distribution of the
asteroids with 3 km 15 km shown by Pravec et al. (2008), our
results deviated somewhat from a Maxwellian distribution and showed a decrease
at the spin rate greater than 5 rev/day. One super-fast-rotator candidate and
two possible binary asteroids were also found in this work.Comment: 18 pages, 20 figures and 2 very long table
MinION-in-ARMS: Nanopore Sequencing to Expedite Barcoding of Specimen-Rich Macrofaunal Samples From Autonomous Reef Monitoring Structures
Autonomous Reef Monitoring Structure (ARMS) are standardized devices for sampling biodiversity in complex marine benthic habitats such as coral reefs. When coupled with DNA sequencing, these devices greatly expand our ability to document marine biodiversity. Unfortunately, the existing workflow for processing macrofaunal samples (\u3e2-mm) in the ARMS pipelineāwhich involves Sanger sequencingāis expensive, laborious, and thus prohibitive for ARMS researchers. Here, we propose a faster, more cost-effective alternative by demonstrating a successful application of the MinION-based barcoding approach on the \u3e2 mm-size fraction of ARMS samples. All data were available within 3.5ā4 h, and sequencing costs relatively low at approximately US$3 per MinION barcode. We sequenced the 313-bp fragment of the cytochrome c oxidase subunit I (COI) for 725 samples on both MinION and Illumina platforms, and retrieved 507ā584 overlapping barcodes. MinION barcodes were highly accurate (ā¼99.9%) when compared with Illumina reference barcodes. Molecular operational taxonomic units inferred between MinION and Illumina barcodes were consistently stable, and match ratios demonstrated highly congruent clustering patterns (ā„0.96). Our method would make ARMS more accessible to researchers, and greatly expedite the processing of macrofaunal samples; it can also be easily applied to other small-to-moderate DNA barcoding projects (\u3c10,000 specimens) for rapid species identification and discovery
VI-Band Follow-Up Observations of Ultra-Long-Period Cepheid Candidates in M31
The ultra-long period Cepheids (ULPCs) are classical Cepheids with pulsation
periods exceeding days. The intrinsic brightness of ULPCs are ~1
to ~3 mag brighter than their shorter period counterparts. This makes them
attractive in future distance scale work to derive distances beyond the limit
set by the shorter period Cepheids. We have initiated a program to search for
ULPCs in M31, using the single-band data taken from the Palomar Transient
Factory, and identified eight possible candidates. In this work, we presented
the VI-band follow-up observations of these eight candidates. Based on our
VI-band light curves of these candidates and their locations in the
color-magnitude diagram and the Period-Wesenheit diagram, we verify two
candidates as being truly ULPCs. The six other candidates are most likely other
kinds of long-period variables. With the two confirmed M31 ULPCs, we tested the
applicability of ULPCs in distance scale work by deriving the distance modulus
of M31. It was found to be mag. The large error
in the derived distance modulus, together with the large intrinsic dispersion
of the Period-Wesenheit (PW) relation and the small number of ULPCs in a given
host galaxy, means that the question of the suitability of ULPCs as standard
candles is still open. Further work is needed to enlarge the sample of
calibrating ULPCs and reduce the intrinsic dispersion of the PW relation before
re-considering ULPCs as suitable distance indicators.Comment: 13 pages, with 14 Figures and 4 Tables (one online table). AJ
accepte
Asteroid lightcurves from the Palomar Transient Factory survey: Rotation periods and phase functions from sparse photometry
We fit 54,296 sparsely-sampled asteroid lightcurves in the Palomar Transient
Factory to a combined rotation plus phase-function model. Each lightcurve
consists of 20+ observations acquired in a single opposition. Using 805
asteroids in our sample that have reference periods in the literature, we find
the reliability of our fitted periods is a complicated function of the period,
amplitude, apparent magnitude and other attributes. Using the 805-asteroid
ground-truth sample, we train an automated classifier to estimate (along with
manual inspection) the validity of the remaining 53,000 fitted periods. By this
method we find 9,033 of our lightcurves (of 8,300 unique asteroids) have
reliable periods. Subsequent consideration of asteroids with multiple
lightcurve fits indicate 4% contamination in these reliable periods. For 3,902
lightcurves with sufficient phase-angle coverage and either a reliably-fit
period or low amplitude, we examine the distribution of several phase-function
parameters, none of which are bimodal though all correlate with the bond albedo
and with visible-band colors. Comparing the theoretical maximal spin rate of a
fluid body with our amplitude versus spin-rate distribution suggests that, if
held together only by self-gravity, most asteroids are in general less dense
than 2 g/cm, while C types have a lower limit of between 1 and 2 g/cm,
in agreement with previous density estimates. For 5-20km diameters, S types
rotate faster and have lower amplitudes than C types. If both populations share
the same angular momentum, this may indicate the two types' differing ability
to deform under rotational stress. Lastly, we compare our absolute magnitudes
and apparent-magnitude residuals to those of the Minor Planet Center's nominal
, rotation-neglecting model; our phase-function plus Fourier-series
fitting reduces asteroid photometric RMS scatter by a factor of 3.Comment: 35 pages, 29 figures. Accepted 15-Apr-2015 to The Astronomical
Journal (AJ). Supplementary material including ASCII data tables will be
available through the publishing journal's websit
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