The All Sky Automated Survey for SuperNovae or ASAS-SN, and less formally ASASSN, is an automated program to search for new supernovae and other astronomical transients. It has 20 robotic telescopes in both the northern and southern hemispheres. Currently, it can survey the entire sky approximately once every day.
Initially, there were four ASAS-SN telescopes at Haleakala and another four at Cerro Tololo, an LCOGT site. Twelve more telescopes were deployed in 2017 in Chile, South Africa and Texas, with funds from the Moore Foundation, the Ohio State University, the Mount Cuba Astronomical Foundation, China, Chile, Denmark, and Germany. All the telescopes (Nikon telephoto f400/2.8 lenses) have a diameter of 14 cm and ProLine PL230 CCD cameras. The pixels in the cameras span 7.8 arc seconds, so follow up observations on other telescopes are usually required to get a more accurate location.
The main goal of the project is to look for bright supernovae, including the most powerful supernova ever discovered, ASASSN-15lh. However other transient objects are frequently discovered, including nearby tidal disruption events, Galactic novae (e.g., ASASSN-16kt, ASASSN-16ma, and ASASSN-18fv), cataclysmic variables, and stellar flares, including several of the largest flares ever seen. In July 2017 ASAS-SN has discovered its first comet, ASASSN1. It can detect new objects with magnitudes between 18 and 8.
Objects discovered receive designations starting with ASASSN followed by a dash, a two digit year and letters, for example ASASSN-15lh.
|All Sky Automated Survey for SuperNovae|
ASASSN-15lh (supernova designation SN 2015L) is an extremely bright astronomical transient discovered by the All Sky Automated Survey for SuperNovae (ASAS-SN), with the appearance of a hypernova event. It was first detected on June 14, 2015, located within a faint galaxy in the southern constellation Indus, and is the brightest supernova-like object ever observed. At its peak, ASASSN-15lh was 570 billion times brighter than the Sun, and 20 times brighter than the combined light emitted by the Milky Way Galaxy. The emitted energy was exceeded by PS1-10adi.
The nature of ASASSN-15lh is disputed. The most popular explanations are that it is the most luminous type I supernova (hypernova) ever observed, or a tidal disruption event around a supermassive black hole. Other hypotheses include: gravitational lensing; a quark nova inside a Wolf–Rayet star; or a rapid magnetar spindown.ASASSN-V J213939.3-702817.4
ASASSN-V J213939.3-702817.4 (also known as ASAS-SN-V J213939.3-702817.4 and J213939.3-702817.4) is a star, previously non-variable, found to be associated with an unusual, deep dimming event that was uncovered by the All Sky Automated Survey for SuperNovae (ASAS-SN) project, and first reported on 4 June 2019 in The Astronomer's Telegram.The star, in the Indus constellation about 3,630 ± 110 ly (1,113 ± 33 pc) away, was first observed on 13 May 2014 (UT) by ASAS-SN, and, as of 4 June 2019, has resulted in more than 1580 data points, including a quiescent mean magnitude of g~12.95. On 4 June 2019, the star was reported to have dimmed gradually from g~12.96 at HJD 2458635.78, to g~14.22 at 2458637.95, and, as of 4 June 2019, seems to be returning to its quiescent state of g~13.29 at HJD 2458638.89. According to astronomer Tharindu Jayasinghe, one of the discoverers of the deep dimming event, "[The star has] been quiescent for so long and then suddenly decreased in brightness by a huge amount ... Why that happened, we don’t know yet.”ASASSN1
Comet ASASSN1 (IAU designation C/2017 O1) is a comet discovered by the All Sky Automated Survey for SuperNovae (ASAS-SN). It was first detected on July 19, 2017, located in the southern constellation Cetus.HV 2112
HV 2112 is a cool luminous variable star in the Small Magellanic Cloud. Until 2018, it was considered to be the most likely candidate for a Thorne–Żytkow object, but it is now thought to be an asymptotic giant branch star.Indus (constellation)
Indus is a constellation in the southern sky created in the late sixteenth century.Nova Carinae 2018
Nova Carinae 2018 is a nova in the Milky Way galaxy, discovered on March 20, 2018 by the All Sky Automated Survey for SuperNovae. Also known by its discovery designation of ASASSN-18fv, it is located in the constellation Carina, near the 5th magnitude star HD 92063.Pre-discovery images were matched to a star of Gaia magnitude 20.1. On March 21, it had brightened to a Gaia magnitude 7.80 (visual magnitude 7.45), and to magnitude 6.62 later the same day.V407 Lupi
V407 Lupi, or ASASSN-16kt, was a bright nova in the constellation Lupus discovered by All Sky Automated Survey for SuperNovae, which peaked at magnitude of 5.6 in late September 2016.V5856 Sagittarii
V5856 Sagittarii, or ASASSN-16ma, was a bright nova in the constellation Sagittarius discovered by All Sky Automated Survey for SuperNovae the 25th of October 2016, which peaked at magnitude of 5.4 in early November 2016. It is one of the brightest novae in recent history, and the brightest since V5668 Sagittarii in 2015. Being in one of the densest regions of the sky (the galactic core) it is nearly impossible to determine the culprit system, but due to the nature of the nova, a white dwarf and giant star binary system is the most likely origin.