EL Aquilae

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Double star
EL Aquilae
AladinLite
Observation
dates equinox :  J2000.0 , epoch : J2000.0
Constellation Eagle
Right ascension 18 h 50 m 8 s
declination + 03 ° 27 ′ 0 ″
Apparent brightness 20.9 likes
Typing
rel. Brightness
(G-band) 		(16.62 ± 0.01) mag
rel. Brightness
(J-band) 		(13.41 ± 0.03) mag
B − V color index −1.88 
Variable star type NA / DQ 
Astrometry
parallax (0.2008 ± 0.1221)  mas
Proper movement 
Rec. Share: (−2.44 ± 0.19)  mas / a
Dec. portion: (-5.98 ± 0.15)  mas / a
Physical Properties
Other names
and catalog entries
2MASS catalog 2MASS J18560202-0319205 [2]
Other names Nova Aquilae 1927, EL Aquilae, AAVSO 1850-03, AN 60.1927, IPHAS2 J185601.86-031918.7

Template: Infobox Star / Maintenance / MagGTemplate: Infobox Star / Maintenance / MagJ

EL Aquilae was a nova that wasdiscovered on photo platesby Max Wolf in Heidelberg on July 30th and 31st, 1927. She was categorized by him as a star of the ninth magnitude.

EL Aquilae is not one of the bright novas for which long series of spectrograms have been preserved. It remained undetected for more than six weeks after its maximum. It is therefore not surprising that the few spectroscopic observations of the Nova were made with little scatter of the individual values ​​from the mean. There is also hardly any evidence in the literature, particularly with regard to the character of the absorption spectra. Given this, and the fact that El Aquilae is a good example of certain behavioral aspects of novae, it seemed appropriate to provide a description of the spectrum as observed at the Lick Observatory . First, however, a brief summary of the general nature of the Nova is needed.

Photographs taken at Harvard prior to the discovery show that the predominant maximum occurred around June 15, 1927, and that the star was no more than 6.4 m or brighter. Other photographs taken before the discovery at the Bosscha Observatory in Lembang show the existence of a minor maximum for July 20, 1927. Although no final discussion of the light curve has been published, these observations are sufficient for a description of the spectrum.

No attempt was made to draw an actual light curve, as Harvard and Lembang observations differ systematically. There are no spectrographic records for the first two months after the main peak. The first spectrograms recorded near the minor maximum on August 17, 1927 show emission bands and two groups of absorption lines. On August 21, 1927, when the nova had decreased by half an order of magnitude, the continuous spectrum relative to the bright bands had also faded, and both absorption spectra had disappeared (Milton Lasell Humason). Apparently, no real absorption lines were observed afterwards.

A few days later, in the last week of August in 1927, the emission lines of [O III] appeared at 4363, 4959 and 5007 Å (Simeis observer, Struve). The emissions were recorded by several observers in September and October.

In addition, Fe II emissions at 4924 and 5018 Å are likely to have continued through early September. The width of the emission bands, including that of hydrogen, is rather poorly determined: the shift is around 50 or 55 units. The tracks indicate that the N III emissions at 4640 and 4100 Å on October 1 were unusually broad and diffuse, reminiscent of the various nitrogen emissions in Nova Geminorum in 1912 . The following year, when the star was back in an observable position, it had faded to the eleventh order of magnitude, and no further spectroscopic observations appeared to have been made.

A particularly interesting and telling aspect is the fact that, like the Nova Aquilae 1918 , there were some clear fluctuations in brightness in the first three months after the maximum, which are closely related to the presence or absence of the absorption spectra. This is because the latter were only observed during the maximum luminosity and were definitely not present at any minimum. In the case of Nova EL Aquilae, as the observations showed, there was a similar phenomenon on a more modest scale.

The brightness of EL Aquilae was derived by comparing it with the stars of the pole sequence from the photographic plates produced with the 91 cm Lick refractor (Crossley telescope) at the Lick Observatory in the US state of California on June 5, 1940. The apparent brightness is photographically about 19.0 m , with an uncertainty of two or three tenths of an order of magnitude. It seemed likely that the Nova had returned to normal brightness in the 13 years since it was discovered in 1927. Before the discovery, photographic plates showed that the star was weaker than sixteen magnitudes.

Individual evidence

  1. ↑ a b c d e f EL Aquilae. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed on March 28, 2019 .
  2. ↑ a b V EL Aql. In: VSX. AAVSO , accessed March 28, 2019 .
  3. ↑ Maximilian Wolf (June 21, 1863 - October 3, 1932) German astronomer and pioneer of astrophotography. In: Denkmalpflege Heidelberger Friedhöfe eV 2019, accessed on March 22, 2019 .
  4. ↑ a b c d Arthur B. Wyse: The Spectrum of Nova (EL) Aquilae (1927) Right Ascension: 18th 50m8; Declination: 3 degrees 27 '(1900) In: Publications of Lick Observatory, vol. 14, pp. 217-227, [1] .
  5. ^ North Polar Sequence - Oxford Reference. In: Oxford University Press. Retrieved June 13, 2019 .
  6. ↑ eSky: North Polar Sequence. In: www.glyphweb.com. Retrieved June 13, 2019 .