All-Sky Automated Survey for Supernovae
NEWS: ASAS-SN is now supported by a 5-year grant from the Gordon and Betty Moore Foundation! (January 2017).
ASASSN-16no, our 400th SN! (November 2016).
Three ASAS-SN papers posted: 14li in radio, 14li host galaxy, 16fq progenitor (Sept. 1st, 2016).
We discovered ASASSN-16fq, our lowest redshift SN yet (of 339 and counting) (May 2016).
Busy writing papers: 2014 SN Catalog, late 14ae evolution, 2nd 15lh paper (April/May 2016).
Press materials for ASASSN-15lh, the most powerful supernova ever discovered! (January 2016).
It was raining supernovae: dramatic finish to a great year! (December 2015).
See NASA and Chandra press releases on our TDE ASASSN-14li (October 2015).
With funds from Mt. Cuba Astronomical Foundation Cassius is now a four-telescope unit! (July 2015)
ASAS-SN results presented at the AAS press conference (January 2015).
See our TDE ASASSN-14ae press release (October 2014).

Bright supernovae discovered: 428 (151 in 2016)

ASAS-SN: All Transients | Supernovae | CV Patrol | ATels | Papers

Twitter | Channel | Picture of the Week | ASAS (Warsaw)

Status live: |

We are now supported by 5-year grant GBMF5490.

We are also supported by Grant AST-151592. Our telescopes are hosted by .

ASAS-SN expansion was possible with suport from , , and CASSACA.

We thank George Skestos for his generous gift to Prof. Kochanek, partially used to expand ASAS-SN.

We thank Robert Martin Ayers Sciences Fund for supporting our operations.

What is ASAS-SN?

The sky is very big: even in the present day, only human eyes fully survey the sky for the transient, variable and violent events that are crucial probes of the nature and physics of our Universe. We are changing that with our "All-Sky Automated Survey for Supernovae" (ASAS-SN or "Assassin") project, which will soon automatically survey the entire visible sky every night down to about 17th magnitude, more than 25,000 times deeper than human eye. Such a project is guaranteed to result in many important discoveries, some of them potentially transformative to the field of astrophysics---think about ASAS-SN as the "SSST" - Small Synoptic Survey Telescope, complementing LSST and other time-domain projects by frequently observing the entire bright sky. Bright transients, Galactic and extragalactic, discovered early by our high-cadence survey, are especially valuable, as they are easy to study using relatively modest size telescopes.

ASAS-SN is currently comprised of two units. ASAS-SN Unit-1, known as "Brutus", which also happens to be the name of the Ohio State mascot, is comprised of four robotic 14-cm telescopes deployed at the Haleakala station of the Las Cumbres Observatory Global Telescope Network. ASAS-SN Unit-2, named "Cassius", also consists of four 14-cm telescopes deployed at the LCOGT Cerro Tololo station. Together, these allow us to observe a total of approximately 20,000 square degrees each clear night. With support from the Gordon and Betty Moore Foundation grant GBMF5490 we will soon deploy additional 8 telescopes at two other LCO sites, allowing us to survey the entire visible sky every night, and making our network much less sensitive to weather conditions.

We are discovering numerous bright supernovae in both hemispheres (420 total, 151 in 2016). See below where our supernova discoveries announced so far are located on the sky (bigger symbols - smaller distance)

We continue to discover numerous bright cataclysmic variables, many of which are being intensely observed by professional and amateur astronomers.

Generally we are posting our real-time discoveries using ATel, so if you interested in being notified of our results, you should subscribe to that useful service, and also see our ASAS-SN Transients page.

See below our sky coverage plot for the last 365 days - we are now observing the entire sky!

At this point we are focused on discovering bright, nearby supernovae, but we like all kinds of variable objects, so if there is an object with V-band magnitude between V~9 and V~17 that we might have in our data, send us an e-mail ( and we will check what we have. Here are some papers written by outside collaborators that have used our unique ASAS-SN data: Herczeg et al. (2016), Rodriguez et al.(2016).


At OSU: Jon Brown, Tom Holoien, Chris Kochanek, Josh Shields, Kris Stanek, John Beacom, Todd Thompson;

Ben Shappee has moved (August 2014) to Carnegie Observatories, Pasadena, to start his 5-year Hubble-Carnegie-Princeton Postdoctoral Fellowship;

José Luis Prieto (Universidad Diego Portales; MAS);

Grzegorz Pojmanski (Warsaw University Observatory);

Joseph Brimacombe (Coral Towers Observatory);

David Bersier (LJMU);

Subo Dong, Ping Chen, Subhash Bose (KIAA-PKU);

Emilio Falco (CfA);

Przemek Wozniak (LANL);

Maximilian Stritzinger (Aarhus);

Nidia Morrell (Carnegie Observatories, Las Campanas Observatory);

Laura Chomiuk, Jay Strader (MSU);

Raffaella Margutti (Northwestern);

Anna Franckowiak (DESY).

Udit Basu, a local (Ohio) high school student who worked with us for 3 years, is now an undergrad at Princeton Astrophysics.

We thank Las Cumbres Observatory and its staff for their continued support of ASAS-SN: we truly could not do this without your help.

An important part of our project is the follow-up effort with bigger telescopes to get confirmation imaging (our images have 7.8" pixels). We are fortunate to have a number of "unpaid professional astronomers" working with us on ASAS-SN "ad hoc" SN confirmation effort: E. Conseil (Association Francaise des Observateurs d'Etoiles Variables, France), I. Cruz (Cruz Observatory, USA), J. M. Fernandez (Observatory Inmaculada del Molino, Spain), S. Kiyota (Variable Star Observers League in Japan), R. A. Koff (AntelopeHills Observatory), G. Krannich (Roof Observatory Kaufering, Germany), G. Masi (Virtual Telescope Project, Ceccano, Italy), L. A. G. Monard (Klein Karoo Observatory, Western Cape, South Africa), B. Nicholls (Mt. Vernon Obs., New Zealand), J. Nicolas (Groupe SNAUDE, France), R. Post (Post Astronomy), G. Stone (Sierra Remote Observatories), W. Wiethoff (University of Minnesota, Duluth, USA). You can see from many joint Astronomer's Telegrams we have published that it is a very fruitful collaboration - we have confirmed together almost 300 supernovae!

A number of professional astronomers have also contributed their effort and telescope time to ASAS-SN, which we most appreciate. You can see the names of our collaborators on ASAS-SN results annouced so far on ASAS-SN papers and ATels. So when you get an e-mail from us, asking to collaborate on a new exciting ASAS-SN target, we hope you will say "yes"!

ASAS-SN Hardware:

Our team makes ASAS-SN a success, but we also need excellent hardware to aid us in our ultimate goal of studying real-time variability of the entire sky:

Since we are using relatively small telescopes (lenses), we cannnot afford to waste many photons. As our detectors we have selected ProLine PL230 CCD cameras from FLI, with back-iluminated CCD sensors, giving us high QE, low-noise and fast readout (and of course they are electrically cooled). To cover 20,000 square degrees each night, we take several hundreds of images nightly with each camera. We have been very happy with the reliability of our cameras, and we will be deploying more of them as part of our 2017 expansion.

To achieve large field of view with a very stable and uniform point-spread-function (PSF) across the field, we use Nikon AF-S NIKKOR 400mm f/2.8G ED VR AF lenses. We had high expectations for these lenses and were not disappointed: we obtain stable and sharp images for many nights in a row. Stability is crucial for the image subtraction method, which we employ to detect transients, to work best.

And again, all ASAS-SN telescopes are deployed and run by Las Cumbres Observatory, including their telescope hardware and software: "Many eyes - one vision".

Wed Jan 4 12:51:44 EST 2017 This homepage is maintained by Tom Holoien and Kris Stanek (
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