118919469
A MODIFIED MODEL OF NONLOCALLY CORRECTED GRAVITY: COSMOLOGY AND THE NEWTONIAN LIMIT
A modified form of nonlocally corrected theory of gravity is investigated in the context of cosmology and the Newtonian limit. This form of nonlocal correction to classic Einstein–Hilbert action can be locally represented by a triple-scalar–tensor theory in which one of the scalar degrees of freedom is phantom-like and the other two are quintessence-like. We show that there exists a stable de Sitter solution for the cosmological dynamics if a suitable form of potential function V(ϕ) (or equivalently, f(R)) is selected. However, no matter what a potential function is selected, there is always an early time repeller solution corresponding to a radiation dominated universe. Besides, the equations for linear scalar perturbations are presented and it is shown that the form of potential function V(ϕ) is stringently constrained by the solar system test, although the post-Newtonian parameter γ is not directly affected by this function.
118435552
Near-infrared Observations of Comet-like Asteroid (596) Scheila
Asteroid (596) Scheila was reported to exhibit a cometary appearance and an increase in brightness on UT 2010 December 10.4. We used the IRCS spectrograph on the 8 m Subaru telescope to obtain medium-resolution spectra of Scheila in the HK band (1.4-2.5 μm) and low-resolution spectra in the KL band (2.0-4.0 μm) on UT 2010 December 13 and 14. In addition, we obtained low-resolution spectroscopy using the SpeX spectrograph on the 3 m NASA Infrared Telescope Facility on UT 2011 January 4 and 5. The spectrum of Scheila shows a consistent red slope from 0.8 to 4.0 μm with no apparent absorption features, resembling spectra of D-type asteroids. An intimate mixing model suggests that the amount of water ice that might be present on the surface of Scheila is no more than a few percent. The spectrum of the Tagish Lake chondrite matches the asteroid's spectrum at shorter wavelengths (λ < 2.5 μm), but no hydration features are observed at longer wavelengths on Scheila. Our analysis corroborates other studies suggesting that the comet-like activity of Scheila is likely not caused by the sublimation of water ice. The dust coma and tail may be results of a recent impact event.
9863216
OBSERVATIONAL AND DYNAMICAL CHARACTERIZATION OF MAIN-BELT COMET P/2010 R2 (La Sagra)
We present observations of the recently discovered comet-like main-belt object P/2010 R2 (La Sagra) obtained by Pan-STARRS1 and the Faulkes Telescope-North on Haleakala in Hawaii, the University of Hawaii 2.2 m, Gemini-North, and Keck I telescopes on Mauna Kea, the Danish 1.54 m telescope (operated by the MiNDSTEp consortium) at La Silla, and the Isaac Newton Telescope on La Palma. An antisolar dust tail is observed to be present from 2010 August through 2011 February, while a dust trail aligned with the object's orbit plane is also observed from 2010 December through 2011 August. Assuming typical phase darkening behavior, P/La Sagra is seen to increase in brightness by >1 mag between 2010 August and December, suggesting that dust production is ongoing over this period. These results strongly suggest that the observed activity is cometary in nature (i.e., driven by the sublimation of volatile material), and that P/La Sagra is therefore the most recent main-belt comet to be discovered. We find an approximate absolute magnitude for the nucleus of HR = 17.9 ± 0.2 mag, corresponding to a nucleus radius of ~0.7 km, assuming an albedo of p = 0.05. Comparing the observed scattering surface areas of the dust coma to that of the nucleus when P/La Sagra was active, we find dust-to-nucleus area ratios of Ad /AN = 30-60, comparable to those computed for fellow main-belt comets 238P/Read and P/2008 R1 (Garradd), and one to two orders of magnitude larger than for two other main-belt comets (133P/Elst-Pizarro and 176P/LINEAR). Using optical spectroscopy to search for CN emission, we do not detect any conclusive evidence of sublimation products (i.e., gas emission), finding an upper limit CN production rate of Q CN 100 Myr, suggesting that it is likely native to its current location and that its composition is likely representative of other objects in the same region of the main belt, though the relatively close proximity of the 13:6 mean-motion resonance with Jupiter and the (3,–2,–1) three-body mean-motion resonance with Jupiter and Saturn mean that dynamical instability on larger timescales cannot be ruled out.
54058059
Infrared observations of the 2006 outburst of the recurrent nova RS Ophiuchi: The early phase
We present infrared spectroscopy of the recurrent nova RS Ophiuchi, obtained 11.81, 20.75 and 55.71 d following its 2006 eruption. The spectra are dominated by hydrogen recombination lines, together with He i, O i and O ii lines; the electron temperature of ∼104 K implied by the recombination spectrum suggests that we are seeing primarily the wind of the red giant, ionized by the ultraviolet flash when RS Oph erupted. However, strong coronal emission lines (i.e. emission from fine structure transitions in ions having high ionization potential) are present in the last spectrum. These imply a temperature of 930 000 K for the coronal gas; this is in line with X-ray observations of the 2006 eruption. The emission linewidths decrease with time in a way that is consistent with the shock model for the X-ray emission.
724871
IDENTIFICATION OF MAGNETITE IN B-TYPE ASTEROIDS
Spectrally blue (B-type) asteroids are rare, with the second discovered asteroid, Pallas, being the largest and most famous example. We conducted a focused, infrared spectroscopic survey of B-type asteroids to search for water-related features in these objects. Our results show that the negative optical spectral slope of some B-type asteroids is due to the presence of a broad absorption band centered near 1.0 μm. The 1 μm band can be matched in position and shape using magnetite (Fe3O4), which is an important indicator of past aqueous alteration in the parent body. Furthermore, our observations of B-type asteroid (335) Roberta in the 3 μm region reveal an absorption feature centered at 2.9 μm, which is consistent with the absorption due to phyllosilicates (another hydration product) observed in CI chondrites. The new observations suggest that at least some B-type asteroids are likely to have incorporated significant amounts of water ice and to have experienced intensive aqueous alteration.
17779184
Comet 17P/Holmes in Outburst: The Near Infrared Spectrum
Jupiter family comet 17P/Holmes underwent a remarkable outburst on UT 2007 October 24, in which the integrated brightness abruptly increased by about a factor of a million. We obtained near infrared (0.8-4.2 μm) spectra of 17P/Holmes on UT 2007 October 27, 28, and 31, using the 3.0 m NASA Infrared Telescope Facility atop Mauna Kea. Two broad absorption bands were found in the reflectance spectra with centers (at 2 μm and 3 μm, respectively) and overall shapes consistent with the presence of water ice grains in the coma. Synthetic mixing models of these bands suggest an origin in cold ice grains of micron size. Curiously, though, the expected 1.5 μm band of water ice was not detected in our data, an observation for which we have no explanation. Simultaneously, excess thermal emission in the spectra at wavelengths beyond 3.2 μm has a color temperature of 360 ± 40 K (corresponding to a superheat factor of ~2.0 ± 0.2 at 2.45 AU). This is too hot for these grains to be icy. The detection of both water ice spectral features and short-wavelength thermal emission suggests that the coma of 17P/Holmes has two components (hot, refractory dust and cold ice grains) which are not in thermal contact. A similarity to grains ejected into the coma of 9P/Tempel 1 by the Deep Impact spacecraft is noted.
125376511
Contribution of the LHT model to Z c anti-c coupling
64266626
Top quark pair production via $e^{+}e^{-}$ collision in the littlest Higgs model with T-parity at the ILC
In the framework of the littlest Higgs model with T parity, we studied the contributions of the new particles to the top-quark pair production via e{sup +}e{sup -} collision at the International Linear Collider. We calculated the top-quark pair production cross section and found this process can generate significantly relative correction. The result may be a sensitive probe of the littlest Higgs model with T parity.