Do Fast Radio Bursts Come from Flaring Stars?

Do Fast Radio Bursts Come from Flaring Stars?

by | Dec 16, 2013 | Daily Paper Summaries

Title: Fast Radio Bursts May Originate from Nearby Flaring Stars Authors: Abraham Loeb, Yossi Shvartzvald, Dan Maoz First Author’s Institution: Institute for Theory and Computation, Harvard University Paper Status: MNRAS, in press One of the most intriguing discoveries in radio astronomy in recent years has been the discovery of Fast Radio Bursts (FRBs).  Originally called Lorimer bursts after the first (and for some time, only) burst observed, there are currently six of these bursts published in the literature, and astronomers are puzzled because they look very different from any other astronomical signals observed before.  They are bright- FRBs are the brightest astronomical phenomena seen in radio frequencies, and they don’t seem to have known counterparts in other wavelengths.  They are brief- a burst only lasts a few microseconds, and they don’t seem to repeat.  And they have a very high dispersion measure (DM)- a relationship between time and frequency that tells you how far away a signal comes from (explained well in this Astrobite)- which has indicated an extragalactic origin for FRBs.  To writ, what exactly FRBs are and where they come from is a mystery.In this paper, the authors decided to take a different track from previous theories about FRB origins that point to extragalactic sources, and instead tackled the option of a much more local origin.  Their proposed candidate sources are flare stars– variable stars which can undergo dramatic and unpredictable increases in brightness.  Flare stars are typically dim dwarf stars, and some are already known to produce radio bursts with brief rise times on the order of milliseconds, thought to be produced by cyclotron maser mechanisms in the stellar atmospheres. ...

New Evidence of an Asteroid Encountering a Pulsar

by | Nov 22, 2013 | Daily Paper Summaries

Title: Evidence of an Asteroid Encountering a Pulsar Authors: P. R. Brook, A. Karastergiou, S. Buchner, S. J. Roberts, M. J. Keith, S. Johnson, R. M. Shannon First Author’s Institution:  University of Oxford Pulsars- neutron stars formed during supernovae explosions- are often considered the “precision clocks” of radio astronomy. This is because of two fundamental properties observed from their radio pulses: the average emitted radio beam- known as the pulse profile– remains very stable over decades, and the pulsar has extreme rotational stability thanks to its fast rotation. All pulsars have a rotational frequency, ν, which is gradually decreasing due to a loss of energy, and its change with time, the spin-down rate, tells radio astronomers about the stability of the pulsar. Hundreds of pulsars have been observed to have glitches where the pulsar’s rotational frequency is seen to increase rapidly, and there have even been anti-glitch observations where the pulsar abruptly slowed down, which are thought to be caused by the magnetic fields of the pulsar.But the interesting thing about astronomy is even in a field where things are as precise as pulsars, surprises will still crop up. And this is what happened during a 24-year observing campaign of PSR J0738-4042, when in September 2005 the spin-down rate abruptly changed and a new radio component was observed. In fact, no previously understood mechanism can explain these changes, and the observations led the paper’s authors to propose they witnessed an asteroid encountering the pulsar.The observations were relatively straightforward: PSR J0738-4042 is a bright radio pulsar and was the target of a monitoring campaign by the Hartebeesthoek Radio Astronomy Observatory (HartRAO) in South...