Some background behind my last visit to Arecibo (Aug 2019) and the picture I already posted, but will post again because I love it so much. Incoming THREAD on PSR B1913+16. Buckle up... #AreciboLove #QuieroArecibo 1/18

B1913+16 was discovered by Joe Taylor and Russel Hulse (U-Mass Amherst) in 1974. It's such a spectacular pulsar in so many other respects, people often forget it was also the first binary pulsar found (~100 other PSRs known at the time). #AreciboLove #QuieroArecibo 2/18

The fact it was found at all in 1974(!!) is a testament to @NAICobservatory's preeminence in the world of radio astronomy. B1913+16 was then the 2nd fastest-rotating PSR, spinning once every 59 ms, surpassed only by the Crab (33 ms). #AreciboLove #QuieroArecibo 3/18

Not to mention, it was FAINT compared to other known PSRs, far away (thus significant corrections were needed to correct signal smearing due to the interstellar medium), and it's spin period, constantly changing! That makes it hard to pin down. #AreciboLove #QuieroArecibo 4/18

B1913+16's apparent spin period changes due to binary motion around its companion, a Doppler effect. Imagine standing outside and listening to an ambulance with sirens ablaze, whipping around an adjacent block...FAST. How fast?... #AreciboLove #QuieroArecibo 5/18

PSR B1913+16 completes a full orbit in ~7.75 hrs! Its orbital period and the shape of its radial velocity curve tell us (almost) everything we need to know to model the binary system. #AreciboLove #QuieroArecibo 6/18

Timing the pulsar over many years tells us even more. "Timing" here just means unambiguously accounting for every rotation of the star. Using it as a clock, we can probe all sorts of interesting aspects of its unique environment. #AreciboLove #QuieroArecibo 7/18

Already in 1976, Joe Taylor and others noted B1913+16 may be a prime laboratory for testing theories of gravity. Beyond classical orbital parameters, others predicted by General Relativity (GR) would crop up soon, detectable via pulsar timing. #AreciboLove #QuieroArecibo 8/18

In the meantime, pulsar timing efforts continued at @NAICobservatory; for several years, Joe Taylor and postdoc Joel Weisberg returned to keep careful track of B1913+16's rotations and look for any deviations from their existing "timing model." #AreciboLove #QuieroArecibo 9/18

In 1982, they published: "The most far-reaching result of this experiment is our measurement of a secular decrease of orbital period, consistent with the loss of energy through emission of quadrupole gravitational radiation, as predicted by GR." #AreciboLove #QuieroArecibo 10/18

B1913+16 is a remarkable binary pulsar system and the fact that it was discovered at all in 1974 is extraordinary. But the careful, dedicated accounting for its pulse arrival times that followed changed gravitational physics forever. @ligo #AreciboLove #QuieroArecibo 11/18

Joel Weisberg ( @CarletonCollege) has dedicated over four decades of his life to studying B1913+16. And always, with the premier radio telescope for pulsar timing, @NAICobservatory. #AreciboLove #QuieroArecibo 12/18

Many previous students/collabs have joined in along the way, but Weisberg & Huang (2016) showed, beyond a shadow of a doubt, orbital decay due to gravitational radiation. Note: measurements are "...points, with error bars too small to show."
#AreciboLove #QuieroArecibo 13/18

So what's next?

Due to its relativistic orbit, B1913+16 precesses, like a top. Its axis of rotation goes around once every ~300 years. Unlike with most pulsars, we're treated to an ever-changing perspective on its cone of emission. #AreciboLove #QuieroArecibo 14/18

Thus, we can map the beam! Enter THE PEANUT: a beam-mapping model based on timing and observed pulse profile evolution, developed by Clifton & Weisberg (2008). Closed contours mean we expect the PSR signal to wink out of sight in the future. #AreciboLove #QuieroArecibo 15/18

Model uncertainties mean we're not quite sure when B1913+16's signal will leave us (momentarily, at least). Joel thought it might be as soon as ~2020, which brings me back to the beginning, remembering our last visit to @NAICobservatory in 2019. #AreciboLove #QuieroArecibo 16/18

Lots more is coming soon in this ever-evolving saga of B1913+16, but for now, I'm happy to report the pulsar was still visible at @NAICobservatory last summer! #AreciboLove #QuieroArecibo 17/18

BONUS photo of Joel re-enacting glory days in the @NAICobservatory control room, wearing the wonderful shirt, designed for his retirement party at @CarletonCollege in 2018 (JoelFest; https://www.carleton.edu/physics-astronomy/faculty/joel-fest/). #AreciboLove #QuieroArecibo 18/18