Scott Ransom's Homepage

Scott M. Ransom

Astronomer

NRAO
520 Edgemont Rd.
Charlottesville, VA USA 22903

Phone / Fax: 434-296-0320 / 0278
Email: sransom at nrao dot edu
My GPG Key. My CV and a short bio.

I am a staff astronomer at NRAO-Charlottesville (and a Research Professor in the Astronomy Dept at UVA) specializing in pulsar research. In particular, I search for exotic pulsars (such as binary and/or millisecond pulsars or MSPs) and then time them, using their atomic clock-like rotational characteristics to probe as much basic physics or astrophysics as possible. Recently I've gotten very interested in the direct detection of gravitational waves using MSPs. Here in North America that effort is called NANOGrav.

Prior to August 2004, I was a postdoctoral researcher at McGill University in Montreal in Vicky Kaspi's pulsar group. Before that, I was a graduate student in the Harvard Astronomy Dept. If you are interested (or extremely bored), you can read my thesis here.

PRESTO is the suite of pulsar search and analysis software (written in C and Python) that I wrote, maintain, and use. You can get it and some other software on github.

Jim Condon and I are teaching the UVA graduate Radio Astronomy Course (Astro5340) and our lecture notes are on the web (Essential Radio Astronomy).

I'm the project scientist for GUPPI, the best damn pulsar instrument in the world. The GBT Pulsar Spigot is the pulsar instrument that I used to be responsible for (may it RIP).

Recent News:

April 2014:

Here a public talk I gave at the JMU Planetarium last week on the "Pulsars, Magnetars, Black Holes (Oh My!): The Wickedly Cool Stellar Undead"
Based on some questions I had in talks recently about how we dedisperse pulsar data and why it is harder to detect fast pulsars rather than slow ones, I made these movies: a slow strong pulsar(.avi), the same slow pulsar but much fainter(.avi) (as per a real search), and a weak MSP(.avi). Note how much narrower the significance peak (i.e. reduced-chi²) is as a function of Dispersion Measure for the MSP! Here is the script that made the movies if you are curious.
Here is a talk I gave at the Exascale Radio Astronomy meeting on future searches for pulsars and one from the following week at the APS meeting on testing general relativity with neutron star - white dwarf binaries.

January 2014:

The triple system (MSP J0337+1715) paper is out! Here is the arXiv version and some press stuff as well...

September 2013:

Accelerating Acceleration Searches for Pulsars is a talk I gave at the CASPER meeting in Manchester on how accelsearch in PRESTO works and how we might be able to accelerate it a lot with GPUs.

December 2012:

Here is why I do what I do: Pulsars are cool. Seriously. There is a video of the talk-version of this from the Beijing IAU meeting if you'd rather watch...

July 2012:

Network TV debut! ALMA really is pretty cool...

June 2011:

There is now a tutorial for PRESTO! Whoa! Go forth and find pulsars...

Winter 2010/2011:

The first three radio-detected but gamma-ray selected Fermi MSPs are published. We are now up to at least 32 new MSPs!

Oct 2010:

A Two Solar Mass Neutron Star! (or here) Millisecond pulsar J1614-2230 as measured with GUPPI! See here for the press release.

Sep 2010:

Added pySLALIB to github
Terzan 5 now has 34 pulsars.... Ter5ai is another highly eccentric binary (and was found with coherent GUPPI!).

Early 2010:

GUPPI coherent dedispersion with 800MHz of BW! Check out the original MSP B1937+21 at L-band!

Fall of 2009:

New radio MSPs in Fermi unassociated sources! And lots of em! Here is a recent short talk on them.

Nov 2007:

pySLALIB: Over the past few days I put together a complete set of python+numpy wrappers (using the fantastic f2py) for the SLALIB positional astronomy library (developed by P.T. Wallace). The release includes a complete copy of the Fortran source for SLALIB itself. Everything is released under the GPL. Hopefully some of you find it useful.

Feb 2006:

Terzan 5 now has 33 pulsars - although I think this is getting near the limit of what we can do with the current GBT. The two most recent ones were found by my summer student Ben Sulman using very deep stack searches of all our data. We have timing solutions for 31 of the pulsars, including (we think), Ter5Q, a highly eccentric (e = 0.72) binary MSP. Here is a neat plot that shows an I-band NTT image (from S. Ortolani), with VLA L-band contours (from Fruchter and Goss 2000), and the 31 timing-based pulsar positions.
We finally convinced ourselves that the Backer-beater was real and so we published a paper on Ter5ad (also available here). You can see Jason Hessels' poster and our press release from the recent AAS meeting as well. Just how fast is 716 Hz? That is what the pulsar would sound like if we amplified its signal from the GBT by about 5000 times!
Recent work on the 7 new M28 pulsars has shows us that M28C is highly eccentric (e = 0.84) and very interesting...

Oct 2005:

Terzan 5 now has 31 pulsars, and we have timing solutions for 28 of them!

One of them, Ter5ad, appears to (finally) be a "Backer-beating" 1.39ms pulsar! We're still trying to rule out that it isn't a harmonic of a 2.78ms, pulsar, though.
Another one, Ter5ae, is a new "Black-Widow" type pulsar in a compact binary that my summer student Mike McCarty found using an automated version of Adam Chandler's "Dynamic Power Spectrum" technique.

The GBT has found at least 55 new globular cluster pulsars since it has been in operation! Most of these have been with the fantastic SPIGOT+S-band receiver system.

Feb 2005: Two more MSPs (Z and aa) in Terzan 5 make 26 total!
Jan 2005: We've used the GBT to find 21 new binary and millisecond pulsars in globular cluster Terzan 5.
Here is the abstract and full text of the Science paper.
Aug 2004: Moved to Charlottesville from Montreal.

Last Modified 10 Sept 2013