Looking for Light Pseudoscalar Bosons in the Binary Pulsar System J0737-3039

We present numerical calculations of the photon-light-pseudoscalar-boson conversion in the recently discovered binary pulsar system J0737-3039. Light pseudoscalar bosons (LPBs) oscillate into photons in the presence of strong magnetic fields. In the context of this binary pulsar system, this phenomenon attenuates the light beam emitted by one of the pulsars, when the light ray goes through the magnetosphere of the companion pulsar. We show that such an effect is observable in the gamma-ray band since the binary pulsar is seen almost edge-on, depending on the value of the LPB mass and on the strenght of its two-photon coupling. Our results are surprising in that they show a very sharp and significant (up to 50%) transition probability in the gamma-ray ($>$ tens of MeV) domain. The observations can be performed by the upcoming NASA GLAST mission.Comment: to appear in Phys. Rev. Let

A variable absorption feature in the X-ray spectrum of a magnetar

Soft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are slowly rotating, isolated neutron stars that sporadically undergo episodes of long-term flux enhancement (outbursts) generally accompanied by the emission of short bursts of hard X-rays. This behaviour can be understood in the magnetar model, according to which these sources are mainly powered by their own magnetic energy. This is supported by the fact that the magnetic fields inferred from several observed properties of AXPs and SGRs are greater than - or at the high end of the range of - those of radio pulsars. In the peculiar case of SGR 0418+5729, a weak dipole magnetic moment is derived from its timing parameters, whereas a strong field has been proposed to reside in the stellar interior and in multipole components on the surface. Here we show that the X-ray spectrum of SGR 0418+5729 has an absorption line, the properties of which depend strongly on the star's rotational phase. This line is interpreted as a proton cyclotron feature and its energy implies a magnetic field ranging from 2E14 gauss to more than 1E15 gauss.Comment: Nature, 500, 312 (including Supplementary Information

We are the Martians: Connecting Cosmology with Biology

What frightens you more? Believing you are alone in the universe or rather thinking that there’s someone else out there?   Human beings have been asking themselves this question for many thousands of years while looking at the starry sky. Over the past few decades, however, we have moved from imagination to action, exploring the cosmos using new techniques, often with surprising results. Did you know, for instance, that every year many rocks from Mars fall on the Earth? Or that one of our amino acids has been found in the coma of a comet? Or that we now know of thousands of extrasolar planets, some of them similar to our own?   There are further exciting and important discoveries around the corner that will cast more light on the great enigma of how life started on Earth. In this intriguing book, one of  the world’s leading researchers in astrophysics and space science examines fundamental questions concerning life on Earth and the rest of the cosmos in an accessible and stimulating way

Imminent science: what remains to be discovered

This is not science fiction. It’s a voyage on the arrow of time to the coming fifty years. The legendary palindromic character Mr. Qfwfq from Italo Calvino’s collection of short stories, The Cosmicomics, will go with us – he who knows all the answers but will give out no hints. He will help us to discover the innovations that will have changed our lives by 2062, when, riding astride Halley’s Comet, our omniscient extraterrestrial will return to visit us.In this book, we shall learn how astronomers will devote themselves to the study of the mysterious force of dark energy, which makes up some three-quarters of the Universe. We shall also delve deeply into the study of our Earth, to exploit the immense thermal energy that lies beneath our feet. We shall solve another enigma in today’s science: the origin of life. We shall come to understand how to develop direct contacts between our brains and the rest of the world. We shall learn about the future of genetics, the reason for the longevity of Methuselah flies and the quest for prime numbers. These are only some of the exciting and important discoveries to be revealed in this intriguing book, which is designed for a broader public and not only for science fiction devotees

A scenario for interstellar exploration and its financing

This book develops a credible scenario for interstellar exploration and colonization. In so doing, it examines: • the present situation and prospects for interstellar exploration technologies; • where to go: the search for habitable planets; • the motivations for space travel and colonization; • the financial mechanisms required to fund such enterprises. The final section of the book analyzes the uncertainties surrounding the presented scenario. The purpose of building a scenario is not only to pinpoint future events but also to highlight the uncertainties that may propel the future in different directions. Interstellar travel and colonization requires a civilization in which human beings see themselves as inhabitants of a single planet and in which global governance of these processes is conducted on a cooperative basis. The key question is, then, whether our present civilization is ready for such an endeavor, reflecting the fact that the critical uncertainties are political and cultural in nature. It is written in such a way as to allow the non-professional reader to become part of the debate on the future of space programs

ALPs Explain the Observed Redshift-Dependence of Blazar Spectra

We considered a complete sample of blazars observed with the Imaging Atmospheric Cherenkov Telescopes above $E \geq 80 \, {\rm GeV}$, out to $z = 0.54$ and described by standard photon emission models which predict simple power-law spectra to a good approximation. We first show that the best-fit regression line of the emitted slope distribution $\{\Gamma_{\rm em} (z) \}$ decreases with $z$, in disagreement with physical intuition. Next, we demonstrate that, by allowing for photon-ALP oscillations in intergalactic space, for a realistic values of the parameters the best-fit regression line becomes exactly horizontal in the $\Gamma_{\rm em} - z$ plane. This result is amazing, because it is the only possibility in agreement with physical expectation, and so it can be regarded as a strong hint of the existence of an ALP