Constraints on Lorentz invariance and CPT violation using optical photometry and polarimetry of active galaxies BL Lacertae and S5 B0716+714

Abstract

Various quantum gravity approaches that extend beyond the standard model predict Lorentz Invariance and Charge-Parity-Time Violation at energies approaching the Planck scale. These models frequently predict a wavelength dependent speed of light, which would result in time delays between promptly emitted photons at different energies, as well as a wavelength-dependent rotation of the plane of linear polarization for photons resulting from vacuum birefringence. Here, we describe a pilot program with an automated system of small telescopes that can simultaneously conduct high cadence optical photometry and polarimetry of Active Galactic Nuclei (AGN) in multiple passbands. We use these observations as a proof-of-principle to demonstrate how such data can be used to test various Lorentz Violation models, including special cases of the Standard Model Extension (SME). In our initial campaign with this system, the Array Photo Polarimeter, we observed two AGN sources, including BL Lacertae at redshift z = 0.069, and S5 B0716+714 at z = 0.31. We demonstrate that optical polarimetry with a broadband Luminance filter combined with simultaneous Ic-band observations yields SME parameter constraints that are up to ∼10 and ∼30 times more sensitive than with a standard Ic-band filter, for SME models with mass dimension d = 5 and d = 6, respectively. Using only a small system of telescopes with an effective 0.45-m aperture, we further demonstrate d = 5 constraints for individual lines of sight that are within a factor of ∼1-10 in sensitivity to comparable constraints from optical polarimetry with a 3.6-m telescope. Such an approach could significantly improve existing SME constraints via a polarimetric all-sky survey of AGN with multiple 1-meter class telescopes.

In Vacuo Dispersion-Like Spectral Lags in Gamma-Ray Bursts

“…[12] on dimension-four operators added to the Standard-Model lagrangian, whereas the effects we here consider would be described in field-theory in terms of dimension-five operators. However, describing photons within the SME the effects of dispersion would be combined with birefringence [13][14][15][16][17], which we here assume to be absent consistently with results obtained in frameworks alternative to the SME, such as those studied in Refs. [1,3,7] and references therein).…”

“…For reasons that shall soon be clear it was valuable for us to divide our data sample in different subgroups, characterized by different ranges of values for the energy at emission, which we denote by E 0 . We label as "high" the photons in our sample with E 0 > 40 GeV, with "medium" those with 15 GeV ≤ E 0 ≤ 40 GeV, and with "low" those with 5 GeV ≤ E 0 ≤ 15 GeV. Our "high" photons were already taken into account in the previous studies which led to Figure 1, so it is particularly valuable to keep them distinct from the other photons in our sample (the ones we label as "medium" and "low").…”

Constraints on Lorentz Invariance Violation with Multiwavelength Polarized Astrophysical Sources

“…This leads to an energy-dependent rotation of the polarization vector of the linearly polarized photons, known as vacuum birefringence. Hence, Lorentz invariance can also be tested with astrophysical polarization measurements [4,[29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48]. As polarization measurements are more sensitive than time-offlight measurements by a factor ∝ 1/E, where E is the energy of the light, more stringent constraints on LIV result from the former rather than the latter [21].…”

Non-Minimal Lorentz Violation in Macroscopic Matter

“…We use this freedom to eliminate analogous coefficients from the photon sector. Other minimal violations in photons produce birefringence and are strictly limited by astrophysical tests [20][21][22][23][24][25][26][27][28][29][30]. We can therefore safely neglect the effects of minimal Lorentz violations in the pure-photon sector of the SME.…”