V5668 Sagittarii

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V5668 Sagittarii
V5668SgrALMA.png
The shell of V5668 Sagittarii imaged at 230 GHz with the ALMA. The image has been convolved with a gaussian function to make it match the resolution of the HST at the wavelength of . The major tick marks are separated by 0.1 arc seconds. From Diaz et al. (2018) [1]
Observation data
Epoch J2000.0        Equinox J2000.0 (ICRS)
Constellation Sagittarius
Right ascension 18h 36m 56.84s
Declination −28° 55 39.8
Apparent magnitude  (V)4.2 (max) – 16.0 [2]
Characteristics
Variable type Nova [3]
Astrometry
Distance 5,020 [4]   ly
(1,540  pc)
Other designations
Nova Sagittarii 2015 b, V5668 Sgr, PNV J18365700-2855420 [5]
Database references
SIMBAD data
The light curve of V5668 Sagittarii, plotted from AAVSO data V5668SgrLightCurve.png
The light curve of V5668 Sagittarii, plotted from AAVSO data

V5668 Sagittarii, also known as Nova Sagittarii 2015 Number 2 was the second and brighter of two novae in the southern constellation of Sagittarius in 2015 (the first was V5667 Sagittarii, reported on 12 February 2015 [6] ). It was discovered by John Seach of Chatsworth Island, New South Wales, Australia on 15 March 2015 with a DSLR patrol camera. At the time of discovery it was a 6th magnitude star. [7] [8] It peaked at magnitude of 4.32 on March 21, 2015, making it visible to the naked eye.

V5668 Sagittarii's peak brightness was followed by a series of fluctuations in brightness, then a strong decline of 7 magnitudes during June as the nova went through a dust formation phase. [4] The light curve for this event is very similar to the DQ Herculis intermediate polar, and it shows a coincident oscillation in X-ray flux with a period of 71±2 s due to rotation of the white dwarf. The white dwarf and its companion star are surrounded by a dusty shell of ejected material. [9]

In 2016 Banerjee et al. showed that 107 days after the nova outburst, its dust-dominated SED was well approximated by an 850 K blackbody spectrum. That temperature, along with infrared flux measurements, allowed them to calculate the mass of the dust shell to be 2.7 × 10−7 M , and the mass of the entire shell to be 2.7 to 5.4 × 10−5M. The angular diameter of the dust shell was estimated to be 42 milliarcsec which, along with the time since outburst and the measured expansion velocity of 530 km/sec, allowed the distance, 1.54  kpc , to be calculated. [4]

The location of V5668 Sagittarii (circled in red) V5668SgrLocation.png
The location of V5668 Sagittarii (circled in red)

Two and a half years after the nova event, the ALMA array, operating in the 230 GHz mm-wave radio band, observed a clumpy, roughly circular nova remnant surrounding V5668 Sagittarii. It was about one half arc second in diameter at that time, and was well resolved by the interferometer. [1]

Related Research Articles

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<span class="mw-page-title-main">V4743 Sagittarii</span> Nova that appeared in 2002

V4743 Sagittarii was a bright nova in the southern constellation of Sagittarius. This event was discovered by K. Haseda and colleagues in September 2002. It peaked at magnitude 5.0 on September 20, 2002, then declined rapidly thereafter. It reached a peak temperature of 740,000 K around April 2003 and remained at that level for at least five months, suggesting the white dwarf component has a mass of 1.1–1.2 M. The distance to this system is uncertain. Infrared observations indicate a distance of approximately 21 kly (6.3 kpc). A derivation using maximum magnitude rate of decay showed a distance of 12.7 ± 1.0 kly (3.9 ± 0.3 kpc).

<span class="mw-page-title-main">OS Andromedae</span> Nova event seen in 1986

OS Andromedae, known also as Nova Andromedae 1986, is a classical nova that appeared in the constellation Andromeda during 1986. It was discovered at 10:34 UT on 5 December 1986 by Mitsuri Suzuki, a 28-year-old school teacher living in Ena, Japan. He photographed the portion of the Milky Way that passes through northern Andromeda with a 200-mm telephoto lens, and found the nova when its apparent magnitude was 8.0. Two days later it reached a peak apparent visual magnitude of 6.3.

<span class="mw-page-title-main">V630 Sagittarii</span> Nova that appeared in 1936

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<span class="mw-page-title-main">V705 Cassiopeiae</span> Nova seen in 1993

V705 Cassiopeiae, also known as Nova Cassiopeiae 1993 was a nova which erupted in the constellation Cassiopeia during 1993. The nova was discovered at 11:17 UT on 7 December 1993 by amateur astronomer Kazuyoshi Kanatsu of Matsue, Japan, who photographed it using a 35mm camera with a 55mm f/2.8 lens. Asteroid 6976 Kanatsu was named after him in honor of this discovery. At the time of its discovery the nova had a photographic magnitude of 6.5. Around 18 December 1993 it flared briefly to magnitude 5.3, and then it returned rapidly to magnitude 6.5. It underwent a series of smaller flares until mid February 1993, after which it began a precipitous decline in brightness.

<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.

References

  1. 1 2 Diaz, Marcos P.; Abraham, Zulema; Ribeiro, Val ́erio A.R.M.; Beaklini, Pedro P.B.; Takeda, Larissa (October 2018). "The structure of a recent nova shell as observed by ALMA". Monthly Notices of the Royal Astronomical Society. 480 (1): L54–L57. arXiv: 1808.01848 . Bibcode:2018MNRAS.480L..54D. doi: 10.1093/mnrasl/sly121 .
  2. Samus, N. N.; et al. (2017). "General Catalogue of Variable Stars". Astronomy Reports. 5.1. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID   125853869.
  3. Özdönmez, Aykut; Ege, Ergün; Güver, Tolga; Ak, Tansel (May 2018). "A new catalogue of Galactic novae: investigation of the MMRD relation and spatial distribution". Monthly Notices of the Royal Astronomical Society. 476 (3): 4162–4186. arXiv: 1802.05725 . Bibcode:2018MNRAS.476.4162O. doi:10.1093/mnras/sty432 . Retrieved 9 January 2021.
  4. 1 2 3 Banerjee, D. P. K.; et al. (January 2016). "Near-infrared studies of the carbon monoxide and dust-forming Nova V5668 Sgr". Monthly Notices of the Royal Astronomical Society: Letters. 455 (1): L109–L113. arXiv: 1510.04539 . Bibcode:2016MNRAS.455L.109B. doi:10.1093/mnrasl/slv163.
  5. "V5668 Sgr". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2020-12-01.
  6. Nishiyama, K.; Kabashima, F.; Kojima, T.; Walter, F.M. (July 2015). "V5667 Sagittarii = N Sgr 2015 (No. 1) = Pnv J18142514-2554343". IAU Circular. 9274: 3. Bibcode:2015IAUC.9274....3N . Retrieved 9 January 2021.
  7. Seach, J. (March 2015). Green, D. W. E. (ed.). "Nova Sagittarii 2015 No. 2 = Pnv J18365700-2855420". Central Bureau Electronic Telegrams. 4080: 1. Bibcode:2015CBET.4080....1S.
  8. Macrobert, Alan (18 March 2015). "Nova (Nova Sagittarii 2015 No. 2) Erupts in Sagittarius". Sky & Telescope. American Astronomical Society. Retrieved 9 January 2021.
  9. Harvey, E. J.; et al. (March 2018). "Polarimetry and spectroscopy of the "oxygen flaring" DQ Herculis-like nova: V5668 Sagittarii (2015)". Astronomy & Astrophysics. 611: 15. arXiv: 1802.00224 . Bibcode:2018A&A...611A...3H. doi:10.1051/0004-6361/201731741. S2CID   43919676. A3.

Further reading