Sidereal Time Research Articles

Short-range gravity and Lorentz violation

Comparatively few searches have been performed for violations of local Lorentz invariance in the pure-gravity sector. We show that tests of short-range gravity are sensitive to a broad class of unconstrained and novel signals that depend on the experimental geometry and on sidereal time.

ROTATION OF SOLAR MAGNETIC FIELDS FOR THE CURRENT SOLAR CYCLE 24

The rotation of solar magnetic fields for the current solar cycle 24 is investigated through a cross-correlation analysis of the Carrington synoptic maps of solar photospheric magnetic fields during Carrington rotation numbers 2076-2146 (2008 October to 2014 January). The sidereal rotation rates of positive and negative magnetic fields at some latitudes are shown, and it can be found that the positive (negative) fields generally rotate faster than the negative (positive) fields in the southern (northern) hemisphere at low latitudes. The mean rotation profiles of total, positive, and negative magnetic fields between +/- 60 degrees latitudes in the time interval are also obtained. It should be noted that both of the mean rotation profiles of the positive and negative magnetic fields, as well as the mean rotation profile of the total magnetic field, exhibit a quasi-rigid rotation at latitudes above about 55 degrees. The mean rotation rates of the positive (negative) polarity reach their maximum values at about 9 degrees(6)degrees latitude in the southern (northern) hemisphere. The mean rotation profile of the total magnetic field displays an obvious north-south asymmetry, where the rotation seems to be more differential in the northern hemisphere. The latitude variation in the rotation rate differences between positive and negative magnetic fields is further studied, and it is found that magnetic fields with the same polarity as the leading sunspots at a given hemisphere rotate faster than those with the opposite polarity, except for the zones around 52 degrees latitude of the southern hemisphere and around 35 degrees latitude of the northern hemisphere. The implication of these results is discussed. It is clear that the obtained results can provide some observational constraints on the theoretical research of the mechanisms of differential rotation and solar cycle.

Measurement of the radial density gradient of cosmic ray in the heliosphere by the GRAPES-3 experiment

A radial anisotropy in the flux of cosmic rays in heliosphere was theoretically predicted by Parker and others within the framework of the diffusion–convection mechanism. The solar wind is responsible for sweeping out the galactic cosmic rays, creating a radial density gradient within the heliosphere. This gradient coupled with the interplanetary magnetic field induces a flow of charged particles perpendicular to the ecliptic plane which was measured and correctly explained by Swinson, and is hereafter referred as ‘Swinson flow’. The large area GRAPES-3 tracking muon telescope offers a powerful probe to measure the Swinson flow and the underlying radial density gradient of the galactic cosmic rays at a relatively high rigidity of ∼100GV. The GRAPES-3 data collected over a period of six years (2000–2005) were analyzed and the amplitude of the Swinson flow was estimated to be (0.0644±0.0008)% of cosmic ray flux which was an ∼80σ effect. The phase of the maximum flow was at a sidereal time of (17.70±0.05)h which was 18min earlier than the expected value of 18h. This small 18min phase difference had a significance of ∼6σ indicating the inherent precision of the GRAPES-3 measurement. The radial density gradient of the galactic cosmic rays at a median rigidity of 77GV was found to be 0.65% AU−1.

Tests of Lorentz and CPT violation with MiniBooNE neutrino oscillation excesses

Lorentz and CPT symmetry violaton is a predicted phenomenon of Planck–scale physics. Various types of data are analyzed to search for Lorentz violation under the Standard–Model Extension (SME) framework, including neutrino oscillation data. MiniBooNE is a short–baseline neutrino oscillation experiment at Fermilab. The measured excesses from MiniBooNE cannot be reconciled within the neutrino Standard Model (vSM); thus it might be a signal of new physics, such as Lorentz violation. We have analyzed the sidereal time dependence of MiniBooNE data for signals of the possible sidereal time dependence of the ocillation signals. we find that the ve appearance data prefer a sidereal time–independent solution, and the v̄e appearance data slightly prefer a sidereal time–dependent solution, however, the statistical significance is not high to claim the discovery. Limits of order 10−20 GeV are placed on combinations of SME coefficients.

Model independent result on possible diurnal effect in DAMA/LIBRA-phase1

The results obtained in the search for possible diurnal effect in the single-hit low energy data collected by DAMA/LIBRA-phase1 (total exposure: 1.04 ton x yr) deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. are presented. At the present level of sensitivity the presence of any significant diurnal variation and of diurnal time structures in the data can be excluded for both the cases of solar and sidereal time. In particular, the diurnal modulation amplitude expected, because of the Earth diurnal motion, on the basis of the DAMA Dark Matter annual modulation results is below the present sensitivity.

Testing Lorentz invariance inβdecay

In theories aiming to unify the Standard Model with gravity, Lorentz invariance may be broken. Although Lorentz symmetry appears to hold well, few experiments have been performed that consider its violation in the weak interaction. We have started a theoretical and experimental research program to this effect. We consider a Lorentz violating correction of the W -boson propagator, characterized by a tensor. With this extension of the Standard Model the β -decay rate will depend on how the spin of the parent nucleus and the emission direction of the β and ν particles are oriented in absolute space. We explore the consequence for allowed Fermi and Gamow-Teller transitions and the spin degrees of freedom in the latter.Experimentally we exploit the Gamow-Teller transition of polarized 20 Na, where we can test the dependence of the β -decay rate on the spin orientation of 20 Na. The polarization degree is measured using the β asymmetry, while the decay rate is measured by the γ yield. A change in the γ rate, when reversing the spin, implies Lorentz invariance violation. The decay rate should depend on sidereal time and the polarization direction relative to the rotation axis of the earth. The method of the measurement will be presented, together with the first results.

Updated study on multi-TeV cosmic-ray modulation with the Tibet III air shower array using the east-west method

We study the sidereal and solar time modulation of multi-TeV cosmic rays using the east-west method with Tibet III air shower array data taken from November 1999 to December 2008. The statistics are twice the amount used in our previous paper. In this analysis, the amplitude of the observed sidereal time modulation is about 0.1%, and the modulation shows an excess from about 4 to 7 hours and a deficit around 12 hours in local sidereal time. The sidereal time modulation has a weak dependence on the primary energy of the cosmic rays. However, the solar time modulation shows a large energy dependence. We find that the solar time modulation is fairly consistent with the prediction of the Compton-Getting effect for high-energy samples (6.2 TeV and 12.0 TeV), but exceeds the prediction for the low-energy sample (4.0 TeV). Such a discrepancy may be due to the solar modulation or the characteristics of the experimental device in the near threshold energy.

Dung Beetles Use the Milky Way for Orientation

When the moon is absent from the night sky, stars remain as celestial visual cues. Nonetheless, only birds, seals, and humans are known to use stars for orientation. African ball-rolling dung beetles exploit the sun, the moon, and the celestial polarization pattern to move along straight paths, away from the intense competition at the dung pile. Even on clear moonless nights, many beetles still manage to orientate along straight paths. This led us to hypothesize that dung beetles exploit the starry sky for orientation, a feat that has, to our knowledge, never been demonstrated in an insect. Here, we show that dung beetles transport their dung balls along straight paths under a starlit sky but lose this ability under overcast conditions. In a planetarium, the beetles orientate equally well when rolling under a full starlit sky as when only the Milky Way is present. The use of this bidirectional celestial cue for orientation has been proposed for vertebrates, spiders, and insects, but never proven. This finding represents the first convincing demonstration for the use of the starry sky for orientation in insects and provides the first documented use of the Milky Way for orientation in the animal kingdom.

First test of Lorentz violation with a reactor-based antineutrino experiment

We present a search for Lorentz violation with 8249 candidate electron antineutrino events taken by the Double Chooz experiment in 227.9 live days of running. This analysis, featuring a search for a sidereal time dependence of the events, is the first test of Lorentz invariance using a reactor-based antineutrino source. No sidereal variation is present in the data and the disappearance results are consistent with sidereal time independent oscillations. Under the Standard-Model Extension (SME), we set the first limits on fourteen Lorentz violating coefficients associated with transitions between electron and tau flavor, and set two competitive limits associated with transitions between electron and muon flavor.

Test of Lorentz and CPT violation with short baseline neutrino oscillation excesses

The sidereal time dependence of MiniBooNE νe and ν¯e appearance data is analyzed to search for evidence of Lorentz and CPT violation. An unbinned Kolmogorov–Smirnov (K–S) test shows both the νe and ν¯e appearance data are compatible with the null sidereal variation hypothesis to more than 5%. Using an unbinned likelihood fit with a Lorentz-violating oscillation model derived from the Standard Model Extension (SME) to describe any excess events over background, we find that the νe appearance data prefer a sidereal time-independent solution, and the ν¯e appearance data slightly prefer a sidereal time-dependent solution. Limits of order 10−20 GeV are placed on combinations of SME coefficients. These limits give the best limits on certain SME coefficients for νμ→νe and ν¯μ→ν¯e oscillations. The fit values and limits of combinations of SME coefficients are provided.

Compliance with High-Intensity Radiated Fields Regulations - Emitter's Perspective

NASA's Deep Space Network (DSN) uses high-power transmitters on its large antennas to communicate with spacecraft of NASA and its partner agencies. The prime reflectors of the DSN antennas are parabolic, at 34m and 70m in diameter. The DSN transmitters radiate Continuous Wave (CW) signals at 20 kW - 500 kW at X-band and S-band frequencies. The combination of antenna reflector size and high frequency results in a very narrow beam with extensive oscillating near-field pattern. Another unique feature of the DSN antennas is that they (and the radiated beam) move mostly at very slow sidereal rate, essentially identical in magnitude and at the opposite direction of Earth rotation.The DSN is in the process of revamping its documentation to provide analysis of the High Intensity Radiation Fields (HIRF) environment resulting from radio frequency radiation from DSN antennas for comparison to FAA regulations regarding certification of HIRF protection as outlined in the FAA regulations on HIRF protection for aircraft electrical and electronic systems (Title 14, Code of Federal Regulations (14 CFR) [section sign][section sign] 23.1308, 25.1317, 27.1317, and 29.1317).This paper presents work done at JPL, in consultation with the FAA. The work includes analysis of the radiated field structure created by the unique DSN emitters (combination of transmitters and antennas) and comparing it to the fields defined in the environments in the FAA regulations. The paper identifies areas that required special attention, including the implications of the very narrow beam of the DSN emitters and the sidereal rate motion. The paper derives the maximum emitter power allowed without mitigation and the mitigation zones, where required.Finally, the paper presents summary of the results of the analyses of the DSN emitters and the resulting DSN process documentation.

The mid-term and long-term solar quasi-periodic cycles and the possible relationship with planetary motions

This work investigates the solar quasi-periodic cycles with multi-timescales and the possible relationships with planetary motions. The solar cycles are derived from long-term observations of the relative sunspot number and microwave emission at frequency of 2.80 GHz. A series of solar quasi-periodic cycles with multi-timescales are registered. These cycles can be classified into 3 classes: (1) strong PLC (PLC is defined as the solar cycle with a period very close to the ones of some planetary motions, named as planetary-like cycle) which is related strongly with planetary motions, including 9 periodic modes with relatively short period (P<12 yr), and related to the motions of the inner planets and of Jupiter; (2) weak PLC, which is related weakly to planetary motions, including 2 periodic modes with relatively long period (P>12 yr), and possibly related to the motions of outer planets; (3) non-PLC, which so far has no obvious evidence to show the relationship with any planetary motions. Among planets, Jupiter plays a key role in most periodic modes by its sidereal motion or spring tidal motions with other planets. Among planetary motions, the spring tidal motion of the inner planets and of Jupiter dominates the formation of most PLCs. The relationships between multi-timescale solar periodic modes and the planetary motions will help us to understand the essential natures and prediction of solar activities.

Observing Program Calculator for Eclipsing Binary Star Systems

A Microsoft Excel application has been developed to utilize eclipsing binary elements to calculate binary ephemerides that are useful in a program of observing binary systems. Binary star systems consist of two stars orbiting a common center of mass. Consistent monitoring of eclipsing binary stars is important for establishing fundamental astronomical parameters, such as mass and composition of the stellar system. The application that was developed supports effective use of resources in such monitoring applications. The main quantities computed by the application at the time of the eclipse include: local time, Julian date, starting Epoch, altitude of the system, phase of the moon, Local Mean Sidereal Time, and Local Hour Angle. Other quantities computed by the application include current Universal Time (UT), UT/Local Time correction, Julian Date, and current moon phase/percent illuminated. The observing application has been demonstrated to be effective in practical application to obtain differential photometry data for SV Camelopardalis, a system of interest because of variability in its period caused by a third body. The application can be easily modified for use with other highly periodic astronomical systems, for instance transits of extrasolar planets.

Search for Violation of Lorentz Invariance in Top Quark Pair Production and Decay

Using data collected with the D0 detector at the Fermilab Tevatron Collider, corresponding to 5.3 fb(-1) of integrated luminosity, we search for violation of Lorentz invariance by examining the tt[over ¯] production cross section in lepton+jets final states. We quantify this violation using the standard-model extension framework, which predicts a dependence of the tt[over ¯] production cross section on sidereal time as the orientation of the detector changes with the rotation of the Earth. Within this framework, we measure components of the matrices (c(Q))(μν33) and (c(U))(μν33) containing coefficients used to parametrize violation of Lorentz invariance in the top quark sector. Within uncertainties, these coefficients are found to be consistent with zero.

THE EAST-WEST METHOD: AN EXPOSURE-INDEPENDENT METHOD TO SEARCH FOR LARGE-SCALE ANISOTROPIES OF COSMIC RAYS

The measurement of large scale anisotropies in cosmic ray arrival directions at energies above 10^13 eV is performed through the detection of Extensive Air Showers produced by cosmic ray interactions in the atmosphere. The observed anisotropies are small, so accurate measurements require small statistical uncertainties, i.e. large datasets. These can be obtained by employing ground detector arrays with large extensions (from 10^4 to 10^9 m^2) and long operation time (up to 20 years). The control of such arrays is challenging and spurious variations in the counting rate due to instrumental effects (e.g. data taking interruptions or changes in the acceptance) and atmospheric effects (e.g. air temperature and pressure effects on EAS development) are usually present. These modulations must be corrected very precisely before performing standard anisotropy analyses, i.e. harmonic analysis of the counting rate versus local sidereal time. In this paper we discuss an alternative method to measure large scale anisotropies, the "East-West method", originally proposed by Nagashima in 1989. It is a differential method, as it is based on the analysis of the difference of the counting rates in the East and West directions. Besides explaining the principle, we present here its mathematical derivation, showing that the method is largely independent of experimental effects, that is, it does not require corrections for acceptance and/or for atmospheric effects. We explain the use of the method to derive the amplitude and phase of the anisotropy and we demonstrate its power under different conditions of detector operation.

Tracking the stars, Sun, and Moon to connect with the universe

We describe the theory, design, and construction of simple electromechanical devices that automatically and continually track celestial objects. As Earth rotates and revolves, a star tracker always points at a star or other objects fixed to the celestial sphere, such as the center of the Milky Way galaxy. A planet tracker can fixate on any celestial object including the planets, the Sun, or the Moon. A sidereal clock mechanism drives the star tracker, and software that encodes astronomical algorithms controls an inexpensive robot that drives the planet tracker. The star tracker acts like a gyroscope, rigidly oriented in space, despite Earth’s motion. Both trackers indicate the passing of time just like clocks and calendars. The resulting lecture, hallway, or museum displays promote awareness of and excitement about our place in the universe.

An Attempt to Detect Gravitational Waves with the Yellowknife Seismic Arrayt†

The Yellowknife array of 19 vertical short-period seismometers was used to search for small coherent signals in the frequency range from about 1 to 8 Hz. Beamforming and autocorrelation of several hours of digital seismic recording lowers the background noise level to about 10−11 ms−1. Consistent peaks are observed at several frequencies, but terrestrial or instrumental origins have been identified for most components. None of the observed components shows correlation with sidereal time. There is, therefore, no evidence that gravitational waves have been detected.

The next steps in Seti-Italia science and technology

The Italian Medicina Radioastronomy Station (nearby Bologna) is equipped with two antennas: the 32 mt (VLBI) dish and the Northern Cross, a large T-shaped parabolic/cylindrical antenna (30.000 sqm). So far Seti observations have been performed using a SERENDIP IV high resolution spectrometer connected to the VLBI dish in “piggy back” mode configuration. In order to facilitate data interpretation and to introduce innovative methods to search for possible extraterrestrial signals, we are planning to make use of the large UHF Northern Cross transit telescope. Sky observations performed at least within two months, could provide for each day a number of matrices labeled according to the observing sidereal time. The entire set of matrices will be characterized by an averaged spectrum on each row per day. Keeping constant the transit antenna declination, a coherent signal coming from a definite position of the sky, would produce a “flag on” in the same submatrix at the same sidereal time. Detections collected in this way could be considered “confirmed” since they always come from the same region of the sky and are observed regularly. An extremely powerful processing board based on a multi-FPGAs (Field Programmable Gate Array) core was developed and is now under programming. This is conceived to be the processing core for this new kind of investigations.

Survey and chase: A new method of observations for the Michigan Orbital DEbris Survey Telescope (MODEST)

The Michigan Orbital DEbris Survey Telescope (MODEST) is normally used to survey the geosynchronous orbit (GEO) environment to obtain a statistical assessment of the debris population. Due to the short time that the object is in the field-of-view (usually 5 min), it is common practice to assume a circular orbit when calculating the orbit from this limited observational arc. Some objects in the GEO regime are GEO-transfer orbit (GTO) objects which are observed at their apogee or objects with varying eccentricities such as those with high area-to-mass ratios. For these objects, an assumed circular orbit (ACO) prediction would not be accurate. After MODEST was modernized in March 2005 and brought under computer control, it became possible to use the telescope in modes other than tracking at the sidereal rate. Three data runs were conducted to test the orbit determination program, the ability to transfer data effectively between site locations, and to determine if objects could be re-acquired with this method. We report in this paper our initial efforts to determine full orbits based on follow-up observations after the initial detection in survey mode. Our long-term goal is to construct a system which can detect and follow up an object in any orbit at GEO. This paper reports our first steps towards that goal. During the three data collections, only circular orbit objects were obtained. Although this allowed for testing of the process, further tests must be conducted in an effort to target GTO and high area-to-mass objects.

Evidence for Long-term Retrograde Motions of Sunspot Patterns and Indications of Coupled g-mode Rotation Rates

Solar g-modes are global oscillations that would exist primarily in the radiative zone (RZ) and would be excited by either convective overshoot or nuclear burning in the core. Wolff and O’Donovan (Astrophys. J.661, 568, 2007) proposed a non-linear coupling of g-modes into groups that share the same harmonic degree l. Each group (denoted set(l)) exhibits a unique retrograde rotation rate with respect to the RZ that depends mainly on l. The coupling yields a standing wave (nearly stationary in longitude) that has two angularly defined hot spots offset from the equator on opposite sides of the Sun that would deposit energy asymmetrically in the lower convective envelope (CE). It is anticipated that when two or more groups overlap in longitude, an increase in local heating would influence the distribution of sunspots. In this paper, we scanned a multitude of rotational reference frames for sunspot clustering to test for frames that are concordant with the rotation of these g-modes sets. To achieve this, spherical harmonic filtering of sunspot synoptic maps was used to extract patterns consistent with coalesced g-modes. The latitude band, with minimal differential rotation, was sampled from each filtered synoptic map and layered into a stackplot. This was progressively shifted, line-by-line, into different rotational reference frames. We have detected long-lived longitudinal alignments, spanning 90 years of solar cycles, which are consistent with the rotation rate of the deep solar interior as well as other rotational frames predicted by the coupled g-mode model. Their sidereal rotation rates of 370.0, 398.8, 412.7, 418.3, 421.0, 424.2 and 430.0 nHz correspond, respectively, to coupled g-modes for l = 2 through 7 and G, where G is a set with high l values or a group of such sets (unresolved) that rotate almost as fast as the RZ. While the clustering in these reference frames offers new approaches for studying the longitudinal behavior of solar activity, it tentatively leads to the more profound conclusion that a portion of the driving force for sunspot occurrence is linked to energy extracted from the solar core and deposited at the top of the RZ by solar g-modes.