V1494 Aquilae

V1494 Aquilae or Nova Aquilae 1999 b was a nova which occurred during 1999 in the constellation Aquila and reached a brightness of magnitude 3.9 on 2 December 1999.[2] making it easily visible to the naked eye.[9] The nova was discovered with 14×100 binoculars by Alfredo Pereira of Cabo da Roca, Portugal at 18:50 UT on 1 December 1999, when it had a visual magnitude of 6.0.[10]

V1494 Aquilae
Location of V1494 Aquilae (circled in red)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Aquila
Right ascension 19h 23m 05.30s[1]
Declination 04° 57′ 19.1″[1]
Apparent magnitude (V) 3.9 Max.
17.1 Min.[2][3]
Variable type Classical Nova[3],
eclipsing binary[4]
Parallax (π)0.5615 ± 0.1281[5] mas
[3] pc
Absolute magnitude (MV)−8.2 Max.
4.8 Min.[2][3]
Period (P)0.1346 days
Semi-major axis (a)1.17 - 1.24 R
Inclination (i)78.5[7]°
white dwarf
Mass0.92 - 1.13[6] M
Luminosity750 - 3,000[7] L
Temperature>100,000 (2000)[8] K
Mass0.28[6] M
Temperature3,000[7] K
Other designations
Nova Aquilae 1999 b, AAVSO 1918+04
Database references
The light curve of V1494 Aquilae, from AAVSO data

V1494 Aquilae is classified as a fast nova, meaning it faded from peak brightness by more than 3 magnitudes in less than 100 days.[11] During its decline, V1494 Aql produced unusual variations in its x-ray radiation, including a bright burst lasting several minutes. During 2000, the x-ray spectrum developed from a hard (high energy) emission-line spectrum to a spectrum typical of a super soft X-ray source. The x-ray intensity varied with a period of about 40 minutes, probably due to pulsations induced in the white dwarf by its re-kindled hydrogen fusion.[8]

All novae are binary systems with two stars orbiting so close to each other that one star, the "donor" star transfers matter to the other star which is a white dwarf. In the case of V1494 the white dwarf has a mass of 1.20M, and it is accreting mass from the donor star at a rate of 2.1 × 10−10 M yr−1.[12] The stars' orbital period is 3.23 hours,[11] and the system is an eclipsing binary with two brightness minima each orbit, one 0.5 and one 0.1 magnitudes deep.[2][4] This apparently is a measurement of two stars of approximately equal brightness, the nova and a companion 1.4 to the south east. Measuring only the brightness of the nova, the eclipses are about two magnitudes deep.[13] The white dwarf is probably an oxygen-neon-magnesium type.[6]

Unlike some novae, the material ejected from V1494 Aquilae has not formed a visible nebula around the star.[14] However, a shell approximately 6.5 across has been detected spectroscopically in H-alpha emission.[13]

The distance to V1494 Aquilae has been estimated by different methods. Early estimates were based on assumptions about the luminosity of the nova and gave distances around 1.2 kpc.[7] Later models assumed distances of up to 2.2 kpc.[6] Comparison of the measured shell size with the observed expansion velocity give a distance of 1.2±0.2 kpc.[13] Gaia DR2 published a parallax of 0.8394±0.1415 mas, corresponding to a distance of 1,239+422
.[3] Gaia EDR3 published a parallax of 0.5615±0.1281 mas, corresponding to a distance around 1,800 kpc.[5]


  1. ^ a b "V1494 Aql". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-12-05.
  2. ^ a b c d Barsukova, E.A.; Goranskii, V.P. (March 2003). "The Orbital Period of Nova Aquilae 1999 No. 2 (V1494 Aql)". Astronomy Letters. 29 (3): 195–198. Bibcode:2003AstL...29..195B. doi:10.1134/1.1558159. S2CID 119929145.
  3. ^ a b c d e Schaefer, Bradley E. (2018). "The distances to Novae as seen by Gaia". Monthly Notices of the Royal Astronomical Society. 481 (3): 3033–3051. arXiv:1809.00180. Bibcode:2018MNRAS.481.3033S. doi:10.1093/mnras/sty2388. S2CID 118925493.
  4. ^ a b Kato, Taichi; Ishioka, Ryoko; Uemura, Makoto; Starkey, Donn R.; Krajci, Tom (March 2004). "V1494 Aql: Eclipsing Fast Nova with an Unusual Orbital Light Curve". Publications of the Astronomical Society of Japan. 56: S125–S131. arXiv:astro-ph/0310519. Bibcode:2004PASJ...56S.125K. doi:10.1093/pasj/56.sp1.S125. S2CID 8328265.
  5. ^ a b Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. Gaia EDR3 record for this source at VizieR.
  6. ^ a b c d e Hachisu, Izumi; Kato, Mariko (2010). "A Prediction Formula of Supersoft X-Ray Phase of Classical Novae". The Astrophysical Journal. 709 (2): 680–714. arXiv:0912.1136. Bibcode:2010ApJ...709..680H. doi:10.1088/0004-637X/709/2/680. S2CID 118577218.
  7. ^ a b c d Hachisu, Izumi; Kato, Mariko; Kato, Taichi (2004). "Detection of Two-armed Spiral Shocks on the Accretion Disk of the Eclipsing Fast Nova V1494 Aquilae". The Astrophysical Journal. 606 (2): L139–L142. arXiv:astro-ph/0403589. Bibcode:2004ApJ...606L.139H. doi:10.1086/421295. S2CID 16575884.
  8. ^ a b Drake, Jeremy J.; Wagner, R. Mark; Starrfield, Sumner; Butt, Yousaf; Krautter, Joachim; Bond, H. E.; Della Valle, M.; Gehrz, R. D.; Woodward, Charles E.; Evans, A.; Orio, M.; Hauschildt, P.; Hernanz, M.; Mukai, K.; Truran, J. W. (2003). "The Extraordinary X‐ray Light Curve of the Classical Nova V1494 Aquilae (1999 No. 2) in Outburst: The Discovery of Pulsations and a "Burst"". The Astrophysical Journal. 584 (1): 448–452. arXiv:astro-ph/0210072. Bibcode:2003ApJ...584..448D. doi:10.1086/345534. S2CID 14866037.
  9. ^ Nemiroff, R.; Bonnell, J., eds. (15 December 1999). "A Nova in Aquila". Astronomy Picture of the Day. NASA. Retrieved 7 December 2020.
  10. ^ Dicicco, D.; Vitorino, C.; Green, D.W.E. (December 1999). "Nova Aquilae 1999 No. 2". IAU Circular. 7323: 1. Bibcode:1999IAUC.7323....1D.
  11. ^ a b Ritter, H.; Kolb, U. (June 2003). "Catalogue of cataclysmic binaries, low-mass X-ray binaries and related objects (Seventh edition)". Astronomy & Astrophysics. 404: 301–303. arXiv:astro-ph/0301444. Bibcode:2003A&A...404..301R. doi:10.1051/0004-6361:20030330. S2CID 61117701.
  12. ^ Shara, Michael M.; Prialnik, Dina; Hillman, Yael; Kovetz, Attay (June 2018). "The Masses and Accretion Rates of White Dwarfs in Classical and Recurrent Novae". The Astrophysical Journal. 860 (2): 110. arXiv:1804.06880. Bibcode:2018ApJ...860..110S. doi:10.3847/1538-4357/aabfbd. S2CID 55851634.
  13. ^ a b c Barsukova, E. A.; Valeev, A. F.; Goranskij, V. P.; Zharova, A. V. (October 2013). "Spectroscopic detection of resolved ejecta of nova V1494 Aql". The Astronomer's Telegram (5454). Bibcode:2013ATel.5454....1B.
  14. ^ Sahman, D.I.; Dhillon, V.S.; Knigge, C.; Marsh, T.R. (August 2015). "Searching for nova shells around cataclysmic variables". Monthly Notices of the Royal Astronomical Society. 451 (3): 2863–2876. arXiv:1505.06048. Bibcode:2015MNRAS.451.2863S. doi:10.1093/mnras/stv1150. S2CID 62784187.

External linksEdit

Coordinates:   19h 23m 05.38s, +04° 57′ 20.1″