V1309 Scorpii

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V1309 Scorpii
Observation data
Epoch J2000.0 (ICRS)       Equinox J2000.0 (ICRS)
Constellation Scorpius
Right ascension 17h 57m 32.93830s [1]
Declination −30° 43′ 09.96739″ [1]
Apparent magnitude  (V)7.9 [2] max.
Database references
SIMBAD data

V1309 Scorpii (also known as V1309 Sco) is a contact binary that merged into a single star in 2008 in a process known as a luminous red nova.It was the first star to provide conclusive evidence that contact binary systems end their evolution in a stellar merger. Its similarities to V838 Monocerotis and V4332 Sagittarii allowed scientists to identify these stars as merged contact binaries as well. [3]

Contents

Discovery

V1309 Scorpii was discovered independently on 2 September 2008 by three groups: Koichi Nishiyama and Fujio Kabashima, Yukio Sakurai, and Guoyou Sun and Xing Gao. It was originally identified as a transient object located near the galactic bulge at right ascension 17h 57m 32.93s ± 0s.01 and declination −30° 43′ 10″ ± 0″.1. The astronomers who found it noted that it had been invisible to their 12 mag limit telescope just a few days prior to its discovery, indicating that it had recently gone nova. Before its eruption, its faintness and close proximity to USNO-B1.0 star 0592-0608962 (magnitude B = 16.9 and R = 14.8) just 1.14″ away made it difficult to detect. When discovered, V1309 Scorpii was believed to be nothing more than a classical nova. [4]

Identification as a stellar merger

A near-infrared (I band) light curve for V1309 Scorpii, plotted from OGLE data V1309ScoLightCurve.png
A near-infrared (I band) light curve for V1309 Scorpii, plotted from OGLE data

Immediately following its eruption, a group of astrophysicists led by Elena Mason at the European Southern Observatory conducted a study of V1309 Sco's post-outburst spectrum. Originally, the focus of this study was to analyze heavy-metal absorption patterns in a classical nova, but the authors did not realize that this was not a classical nova. In analyzing the spectrum, Mason et al. posited that V1309 Scorpii was surrounded by a slowly expanding gas shell which is denser in the equatorial plane, giving way to a narrow absorption spectrum from this dense region and a broader emission spectrum surrounding it. The incline of this equatorial plane from the observer's line of sight leaves mostly just the polar cap visible. This region would then be approaching the observer as indicated by the overall blueshift of the spectrum. Furthermore, the presence of ejecta from the polar cap at various velocities would account for the observed high velocity wings in the Balmer series. The behavior of the Hα/Hβ ratio, which decreased for a little over a month before shooting up to saturated levels and remaining high months after, was one of many spectral characteristics, also including distinct forbidden lines, that made V1309 Scorpii distinct from classical novae and more similar to red novae. [6]

Following up on the Mason et al. study, Romuald Tylenda and colleagues, who had previous used theoretical models to support that red novae could be the result of stellar mergers, turned to investigate V1309 Scorpii. Due to its proximity to the Galactic Center, V1309 Scorpii was within the field of view of the Optical Gravitational Lensing Experiment (OGLE) telescope, which had been collecting magnitude data of V1309 Scorpii to a precision of 0.01 magnitudes for several years prior to its eruption. The star gradually grew in brightness between 2001 and 2007, before dipping just a little prior to its 2008 eruption. During this eruption, it increases in brightness by 10 mag, or by about a factor of 1×104. The star then rapidly subsided in brightness through the period spectrally observed by Mason et al. Prior to outburst, the star's magnitude had a period of around 1.4 days that decreased exponentially until the outburst. Following the model of a typical contact binary, V1309 Scorpii had two peaks in magnitude per cycle, corresponding to times when the two stars were perpendicular to the observer's line of sight. However, in its case, the second peak in each period began to gradually decrease until its light curve only showed one peak per period. This was because the secondary star began orbiting faster than the envelope of the primary star could keep up with. Because the stars are in contact, the velocity difference begins to dissipate as energy at their point of contact. Thus when the secondary star was approaching the line of sight, it appeared brighter and when it was moving away from the line of sight, it appeared fainter. By 2007, the two stars were so close to merging, that its magnitude, as measured on Earth, appeared roughly spherical, leading to the loss of the second maximum immediately prior to its outburst. [3]

This evidence was the first of its kind to conclusively demonstrate that a contact binary star can end its evolution in a stellar merger and also gave scientists a framework within which to identify other stars as contact binaries and predict future mergers. [7]

Post-identification studies

Since the identification of V1309 Scorpii, further studies of the star have been focussed both on modelling its evolution and collecting additional spectral data.

Further spectral research

One of these follow-up studies continued Mason et al.'s 2010 spectroscopic study by analyzing the evolution of a wider spectrum on a longer time scale. [8] In this study, Kaminsky et al. unexpectedly found a strong spectral signature from CrO in the near infrared, which was the first known discovery of CrO in a stellar spectrum. Present chemical models do not have an explanation for why red novae are the only stars to display this CrO line. [8] This finding may also give further insight into the unexpectedly high amounts of 54Cr that have been observed in our solar system, which was recently found to not originate solely from supernovae. [9]

Theoretical research

Understanding that contact binary stars end their lives in mergers has also spawned theoretical research. Notably, a 2015 study investigated contact binaries within globular clusters and determined that the stellar merger hypothesis may be a leading cause in the formation of blue straggler stars in these regions. [10]

Identifying other stellar mergers

As more is known about V1309 Scorpii and its progenitor than other red novae, it has been described as a "Rosetta Stone" in our understanding of stellar mergers that can help to identify other nova as stellar mergers. [3] For example, data on V1309 Scorpii has already been used to try to explain the mysterious outburst of CK Vulpeculae in 1670–1672 that has puzzled scientists for centuries. [11] Past spectroscopic studies of other stars have turned up more red novae candidates, including V1148 Sagittarii, which was studied as early as 1949. [12] These retrospective inferences have also identified potential red novae like M31 RV that are outside of the Milky Way, including M31LRN 2015, M85 OT2006, NGC300OT2008, and SN2008S. [12]

More recent studies have been more forward-looking, trying to identify stars that match the profile of V1309 Scorpii's progenitor. A search among other contact binaries by OGLE found 14 different contact binary systems with decreasing periods over 0.8 days that are all candidates for upcoming stellar mergers. [13] [ needs update ]

Related Research Articles

<span class="mw-page-title-main">Contact binary</span> Binary star system whose component stars are very close

In astronomy, a contact binary is a binary star system whose component stars are so close that they touch each other or have merged to share their gaseous envelopes. A binary system whose stars share an envelope may also be called an overcontact binary. The term "contact binary" was introduced by astronomer Gerard Kuiper in 1941. Almost all known contact binary systems are eclipsing binaries; eclipsing contact binaries are known as W Ursae Majoris variables, after their type star, W Ursae Majoris.

<span class="mw-page-title-main">V838 Monocerotis</span> Star in the constellation Monoceros

V838 Monocerotis is a spectroscopic binary star system in the constellation Monoceros about 19,000 light years from the Sun. The previously unremarked star was observed in early 2002 experiencing a major outburst, and was one of the largest known stars for a short period following the outburst. Originally believed to be a typical nova eruption, it was then identified as the first of a new class of eruptive variables known as luminous red novae. The reason for the outburst is still uncertain, but is thought to have been a merger of two stars within a triple system.

<span class="mw-page-title-main">Epsilon Sagittarii</span> Binary star in the constellation Sagittarius

Epsilon Sagittarii, formally named Kaus Australis, is a binary star system in the southern zodiac constellation of Sagittarius. The apparent visual magnitude of +1.85 makes it the brightest object in Sagittarius. Based upon parallax measurements, this star is around 143 light-years from the Sun.

<span class="mw-page-title-main">T Coronae Borealis</span> Recurrent nova in the constellation Corona Borealis

T Coronae Borealis, nicknamed the Blaze star, is a recurrent nova in the constellation Corona Borealis. It was first discovered in outburst in 1866 by John Birmingham, although it had been observed earlier as a 10th magnitude star. It may have been observed in 1217 and in 1787 as well. It is expected to undergo an outburst again in 2024.

Xi<sup>2</sup> Sagittarii Star in the constellation Sagittarius

Xi2 Sagittarii, Latinized from ξ2 Sagittarii, is a star in the zodiac constellation of Sagittarius. Data collected during the Hipparcos mission suggests it is an astrometric binary, although nothing is known about the companion. It is visible to the naked eye with a combined apparent visual magnitude of +3.51. Based upon an annual parallax shift of 8.93 mas as seen from Earth, this system is located around 370 light years from the Sun.

<span class="mw-page-title-main">Rho Scorpii</span>

Rho Scorpii is a double star in the constellation of Scorpius. It has an apparent visual magnitude of +3.87, which is bright enough to be seen with the naked eye. Based upon parallax measurements, it is located approximately 472 light years from the Sun. At that distance, the visual magnitude of the system is reduced by 0.07 due to extinction from interstellar dust. It is a member of the Upper Scorpius OB association.

<span class="mw-page-title-main">P Cygni</span> Variable star in the constellation Cygnus

P Cygni is a variable star in the constellation Cygnus. The designation "P" was originally assigned by Johann Bayer in Uranometria as a nova. Located about 5,300 light-years from Earth, it is a hypergiant luminous blue variable (LBV) star of spectral type B1-2 Ia-0ep that is one of the most luminous stars in the Milky Way.

<span class="mw-page-title-main">Chromium(II) oxide</span> Chemical compound

Chromium(II) oxide (CrO) is an inorganic compound composed of chromium and oxygen. It is a black powder that crystallises in the rock salt structure. Hypophosphites may reduce chromium(III) oxide to chromium(II) oxide:

<span class="mw-page-title-main">Luminous red nova</span> Stellar explosion with a distinct red colour

A luminous red nova is a stellar explosion thought to be caused by the merging of two stars. They are characterised by a distinct red colour, and a light curve that fades slowly with resurgent brightness in the infrared. Luminous red novae are not related to standard novae, which are explosions that occur on the surface of white dwarf stars.

<span class="mw-page-title-main">S Monocerotis</span> Star in the constellation Monoceros

S Monocerotis, also known as 15 Monocerotis, is a massive multiple and variable star system located in the constellation Monoceros. It is the brightest star in the Christmas Tree open cluster in the area catalogued as NGC 2264.

<span class="mw-page-title-main">U Scorpii</span> Recurrent nova system first seen in 1863

U Scorpii is a recurrent nova system; one of 10 known recurring novae in the Milky Way galaxy. Located near the northern edge of the constellation Scorpius it normally has a magnitude of 18, but reaches a magnitude of about 8 during outbursts. Outbursts have been observed in 1863, 1906, 1936, 1979, 1987, 1999, 2010, and 2022.

<span class="mw-page-title-main">Stellar collision</span> Coming together of two stars

A stellar collision is the coming together of two stars caused by stellar dynamics within a star cluster, or by the orbital decay of a binary star due to stellar mass loss or gravitational radiation, or by other mechanisms not yet well understood.

<span class="mw-page-title-main">Gamma Monocerotis</span> Star in the constellation of Monoceros

γ Monocerotis, Latinised as Gamma Monocerotis, is a binary star system in the equatorial constellation of Monoceros. Based upon an annual parallax shift of 6.55 mas, it is located roughly 500 light years from the Sun. It can be viewed with the naked eye, having an apparent visual magnitude of 3.96. Gamma Monocerotis is moving away from the Sun with a radial velocity of −5 km/s.

<span class="mw-page-title-main">Epsilon Monocerotis</span> Binary star system in the constellation Monoceros

ε Monocerotis, Latinised as Epsilon Monocerotis, is the Bayer designation of a binary star system in the equatorial constellation Monoceros. Its location is a guide for sky navigation toward the Rosette Nebula.

13 Scorpii, also known by its Bayer designation c2 Scorpii, is a binary star in the constellation Scorpius. Its apparent magnitude is 4.57, meaning it can be faintly seen with the naked eye. Based on parallax estimates made by the Hipparcos spacecraft, the system is located about 480 light-years away. It is located within the Upper Scorpius subgroup of the Scorpius–Centaurus association.

<span class="mw-page-title-main">M31-RV</span> Possible red cataclysmic variable star in the constellation Andromeda

M31-RV is a possible red cataclysmic variable star located in the Andromeda Galaxy (M31) that experienced an outburst in 1988, which is similar to the outburst V838 Monocerotis experienced in 2002. Such objects have been called luminous red novae or intermediate-luminosity red transients. During the outburst, both V838 Mon and M31-RV reached a maximum absolute visual magnitude of -9.8.

<span class="mw-page-title-main">V728 Scorpii</span> Nova seen in 1862

V728 Scorpii, also known as Nova Scorpii 1862, was a nova that occurred in the constellation of Scorpius. It was discovered on 4 October 1862 by John Tebbutt, an astronomer living in New South Wales, Australia, while he was observing a comet. He reported that the star was in the constellation Ara. At the time of its discovery, the nova had an apparent magnitude of 5, making it visible to the unaided eye. Nine days later it had faded to below 11th magnitude, indicating that it was a very fast nova.

<span class="mw-page-title-main">GI Monocerotis</span> 1918 Nova in the constellation Monoceros

GI Monocerotis, also known as Nova Monocerotis 1918, was a nova that erupted in the constellation Monoceros during 1918. It was discovered by Max Wolf on a photographic plate taken at the Heidelberg Observatory on 4 February 1918. At the time of its discovery, it had a photographic magnitude of 8.5, and had already passed its peak brightness. A search of plates taken at the Harvard College Observatory showed that it had a photographic magnitude of 5.4 on 1 January 1918, so it would have been visible to the naked eye around that time. By March 1918 it had dropped to ninth or tenth magnitude. By November 1920 it was a little fainter than 15th magnitude.

<span class="mw-page-title-main">V4332 Sagittarii</span>

V4332 Sagittarii is a nova-like event in the constellation of Sagittarius. It was discovered February 24, 1994 at an apparent visual magnitude of 8.9 by Japanese amateur astronomer Minoru Yamamoto from Okazaki, Aichi, then confirmed by K. Hirosawa. Initially designated Nova Sagittarii 1994 #1, it was given the variable star designation V4332 Sgr. A spectra of the event taken March 4 lacked the characteristic features of a classical nova, with the only emission lines being of the Balmer series. Subsequent spectra showed a rapid decline in luminosity and a change of spectral type over a period of five days. By 2003, the object was ~1500 times less luminous than at peak magnitude and showed a spectrum of an M-type star.

<span class="mw-page-title-main">L-type supergiant</span> Type of cool star

L-type supergiants are an extremely rare type of supergiant star that have spectral types of "L" due to their low temperatures. Such stars should be very unstable due to the extremely low density and temperature but can exist for short periods of time. A star that may eventually become an L-type supergiant starts as a B- or late O-type main sequence star and evolves off the main sequence, up and to the right on the H-R diagram. It may expand by up to a factor of 300 and cool dramatically in the process due to the laws of thermodynamics, reaching spectral type M10 at ~2,400 K and cooling into the L-type range. An L-type supergiant can also form when a pair of hotter, sometimes main-sequence stars undergoes a luminous red nova explosion preceding or during the transition from B-type main sequence star to B or A-type giant to orange or red supergiant, such as in the case of V838 Monocerotis. Some sources also claim that V838 Monocerotis was an extremely unusual main-sequence star, with a temperature of 7300 K and a luminosity less than twice the Sun's, corresponding to an F-type or G0 star. Examples are VX Sagittarii and V838 Monocerotis at their coolest. These stars have huge extended atmospheres that can reach past the orbit of Jupiter.

References

  1. 1 2 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics . 616. A1. arXiv: 1804.09365 . Bibcode: 2018A&A...616A...1G . doi: 10.1051/0004-6361/201833051 . Gaia DR2 record for this source at VizieR.
  2. ↑ Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017). "General catalogue of variable stars". Astronomy Reports. GCVS 5.1. 61 (1): 80. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID   125853869.
  3. 1 2 3 Tylenda, R.; Hajduk, M.; Kamiński, T.; Udalski, A.; Soszyński, I.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Poleski, R.; Wyrzykowski, Ł.; Ulaczyk, K. (2011). "V1309 Scorpii: Merger of a contact binary". Astronomy & Astrophysics. 528: A114. arXiv: 1012.0163 . Bibcode:2011A&A...528A.114T. doi:10.1051/0004-6361/201016221. S2CID   119234303.
  4. ↑ Nakano, S.; Nishiyama, K.; Kabashima, F.; Sakurai, Y.; Jacques, C.; Pimentel, E.; Chekhovich, D.; Korotkiy, S.; Kryachko, T.; Samus, N. N. (2008). "V1309 Scorpii = Nova Scorpii 2008". IAU Circ. 8972: 1. Bibcode:2008IAUC.8972....1N.
  5. ↑ "The main OGLE Homepage". OGLE. Warsaw University. Retrieved 19 March 2022.
  6. ↑ Mason, E.; Diaz, M.; Williams, R. E.; Preston, G.; Bensby, T. (2010). "The peculiar nova V1309 Scorpii/nova Scorpii 2008. A candidate twin of V838 Monocerotis". Astronomy and Astrophysics. 516: A108. arXiv: 1004.3600 . Bibcode:2010A&A...516A.108M. doi:10.1051/0004-6361/200913610. S2CID   118172752.
  7. ↑ Ferreira, Thiago; Saito, Roberto K.; Minniti, Dante; Navarro, María Gabriela; Ramos, Rodrigo Contreras; Smith, Leigh; Lucas, Philip W. (2019). "The asymptotic evolution of the stellar merger V1309 Sco: a Blue Straggler in the making?". MNRAS. 486 (1): 1220–1224. arXiv: 1903.11026 . Bibcode:2019MNRAS.486.1220F. doi:10.1093/mnras/stz878.
  8. 1 2 Kamiński, T.; Mason, E.; Tylenda, R.; Schmidt, M. R. (2015). "Post-outburst spectra of a stellar-merger remnant of V1309 Scorpii: From a twin of V838 Monocerotis to a clone of V4332 Sagittarii". Astronomy & Astrophysics. 580: A34. arXiv: 1504.03421 . Bibcode:2015A&A...580A..34K. doi:10.1051/0004-6361/201526212. S2CID   118566357.
  9. ↑ Wasserburg, G. J.; Trippella, O.; Busso, M. (2015). "Isotope Anomalies in the Fe-group Elements in Meteorites and Connections to Nucleosynthesis in AGB Stars". The Astrophysical Journal. 805 (1): 7. arXiv: 1503.02256 . Bibcode:2015ApJ...805....7W. doi:10.1088/0004-637X/805/1/7. S2CID   35495576.
  10. ↑ Stȩpień, K.; Kiraga, M. (2015). "Model computations of blue stragglers and W UMa-type stars in globular clusters". Astronomy & Astrophysics. 577: A117. arXiv: 1503.07758 . Bibcode:2015A&A...577A.117S. doi:10.1051/0004-6361/201425550. S2CID   54743972.
  11. ↑ Kamiński, Tomasz; Menten, Karl M.; Tylenda, Romuald; Hajduk, Marcin; Patel, Nimesh A.; Kraus, Alexander (2015). "Nuclear ashes and outflow in the eruptive star Nova Vul 1670". Nature. 520 (7547): 322–4. arXiv: 1503.06570 . Bibcode:2015Natur.520..322K. doi:10.1038/nature14257. PMID   25799986. S2CID   4449518.
  12. 1 2 Tylenda, R.; Kamiński, T. (2016). "Evolution of the stellar-merger red nova V1309 Scorpii: Spectral energy distribution analysis". Astronomy & Astrophysics. 592: A134. arXiv: 1606.09426 . Bibcode:2016A&A...592A.134T. doi:10.1051/0004-6361/201527700. S2CID   35724352.
  13. ↑ Kurtenkov, Alexander (2017). "Searching for twins of the V1309 Scorpii progenitor system: A selection of long-period contact binaries". Bulgarian Astronomical Journal. 26: 26. arXiv: 1609.06595 . Bibcode:2017BlgAJ..26...26K.
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