LoTr 5

LoTr 5 is a large, faint planetary nebula in the constellation of Coma Berenices. In 2018, its parallax was measured by Gaia, giving a distance of about 1,650 light-years (506 parsecs).[1][2]

LoTr 5
Emission nebula
Planetary nebula
Observation data: J2000 epoch
Right ascension12h 55m 33.7462s[1]
Declination+25° 53′ 30.561″[1]
Distance1,650 ± 39 ly   (506 ± 12[2] pc)
Apparent diameter~500″[3]
ConstellationComa Berenices
Physical characteristics
Radius1.8 ly   (0.55[4] pc)
DesignationsPN G339.9+88.4[5]

As of 2018, LoTr 5 has the highest galactic latitude of any known planetary nebula, being only 1.5 degrees away from the galactic north pole.[6] Scientists noted this because if the distance of the nebula were found to be greater than a few hundred parsecs, then the gas from the nebula would be expanding into the galactic halo, where there is little interaction with the interstellar medium.[3]

Nomenclature

The nebula is most commonly referred to as LoTr 5, short for Longmore-Tritton 5. It was discovered in 1980 by A. J. Longmore and S. B. Tritton, who found the nebula on photographic plates taken at the UK Schmidt Telescope.[7]

The central star has a number of different names. It is often referred to by its Henry Draper Catalogue designation HD 112313, or by its variable star designation IN Comae Berenices. The General Catalogue of Variable Stars describes it as R:/PN, meaning it is likely a close binary star system with reflection of starlight being the cause of variation, as well as being part of the nucleus of a planetary nebula.[8]

Structure

LoTr 5 is one of the largest planetary nebulae known, with a radius of 1.8 light-years (0.55 parsecs).[4] It mostly emits light at a wavelength of 500.7 nm, corresponding to a doubly ionized oxygen line.[3]

LoTr 5 is not spherical, but is instead a bipolar nebula.[3] Many bipolar and non-spherical nebulae are known to exist, but it is the processes that cause planetary nebulae to get their shapes are not clear, and have been the subject of much debate. However, the "binary hypothesis" posits that binary stars are more likely to produce non-spherical nebulae.[9] For LoTr 5, the binary system likely played a role in shaping the nebula.[3]

A modelling of LoTr 5 shows that it is composed of two round lobes,[3] making a peanut shape. The semimajor and semiminor axes are about 390 arcsec and 100 arcsec, respectively. The position angle of the long axis is 55°. The long axis is tilted 17° away from the line of sight, so there is considerable overlap between the farther northeastern lobe and the closer southwestern lobe.[3] The nebula is not perfectly symmetrical: there appears to be a "hole" east of the nucleus, while the western side has an "arc" of emission.[3]

Binary system
IN Comae Berenices
Observation data
Epoch J2000      Equinox J2000
Constellation Coma Berenices
Right ascension 12h 55m 33.7462s[1]
Declination +25° 53′ 30.561″[1]
Apparent magnitude (V) 8.69[2]
Characteristics
Spectral type G5 III[2] + sdO[6]
U−B color index +0.31[10]
B−V color index +0.81[10]
V−R color index +0.73[10]
Astrometry
Radial velocity (Rv)−16.50 ± 0.2[5] km/s
Proper motion (μ) RA: −25.588[1] mas/yr
Dec.: 4.783[1] mas/yr
Parallax (π)1.9768 ± 0.0462[1] mas
Distance1,650 ± 40 ly
(510 ± 10 pc)
Absolute bolometric
magnitude (Mbol)		0.01 ± 0.08[2]
Orbit[6]
Period (P)2689 ± 52
Eccentricity (e)0.249 ± 0.018
Periastron epoch (T)2455944 ± 25
Argument of periastron (ω)
(secondary)		259.9 ± 4.8°
Semi-amplitude (K1)
(primary)		4.630 ± 0.084 km/s
Details[6]
Mass1.8 ± 0.4 M☉
Radius11.1+5.0
−2.2 R☉
Luminosity78 ± 6 L☉
Surface gravity (log g)2.6 ± 0.1 cgs
Temperature5400 ± 100 K
Metallicity [Fe/H]−0.10 ± 0.05 dex
Rotation5.973 ± 0.008 d
Rotational velocity (v sin i)67.0 ± 1.5 km/s
Other designations
BD+26 2405, HD 112313, HIP 63087, SAO 82570[5]
Database references
SIMBADdata

The central system at LoTr 5 has been known to be binary since 1983.[11] At the center there is an evolved G-type star (IN Comae Berenices) that is often classified as a giant star or a subgiant, as well as a hot O-type subdwarf or white dwarf that is responsible for ionizing the nebula.[12][6] The subdwarf is one of the hottest stars known,[12] with an effective temperature of about 150000 K.[2]

The two stars orbit each very slowly; in fact, with an orbital period of 2,689 ± 52 days (7.36 ± 0.14 a), this is one of the longest periods for a binary system within a planetary nebula. The orbit is also moderately eccentric, at 0.249 ± 0.018.[6] For a long time the hierarchical structure of the system has not been clear. Earlier studies came up with inner orbits around IN Comae Berenices with periods of 1.95 days[13] or 1.75 days,[14] and/or suggesting a third star orbiting the central G-type star.[13][14] The central stars' orbit appears to have a discrepancy with the nebula's "waist" such that the nebula's inclination of 17° may be too low. It is also possible, but more unlikely that the stellar orbits are not coplanar with the nebula's "waist", or that there is an undiscovered object in a close orbit with the degenerate star.[15]

IN Comae Berenices is known to be a variable star, with its brightness varying on a cycle that is about 5.9 days long. This corresponds to the rotation period of the star, and the variability is attributed to starspots, making it an RS Canum Venaticorum variable. With Doppler imaging, the starspots were found to be lying at middle latitudes (40-50°), covering 22% of the star's surface, and about 600 K cooler than the rest of the star's surface.[10] Its spectrum shows it to be rich in barium and other s-process elements, making it a barium star.[6]

IN Comae Berenices emits X-rays. These X-rays likely come from the star's corona, and are associated with the star's rapid rotation.[16]

In terms of structure, LoTr 5 is very similar to Abell 35, another planetary nebula. Both are large and faint planetary nebulae with a binary nucleus, consisting of a rapidly rotating G-type star that is a rotational variable.[12]

References
  1. 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.
  2. Kővári, Zs.; Strassmeier, K. G.; Oláh, K.; Kriskovics, L.; Vida, K.; Carroll, T. A.; Granzer, T.; Ilyin, I.; Jurcsik, J.; Kővári, E.; Weber, M. (2019). "Surface magnetic activity of the fast-rotating G5 giant IN Comae, central star of the faint planetary nebula LoTr 5". Astronomy & Astrophysics. 624: A83. arXiv:1902.09460. Bibcode:2019A&A...624A..83K. doi:10.1051/0004-6361/201834810. S2CID 118977429.
  3. Graham, M. F.; Meaburn, J.; Lopez, J. A.; Harman, D. J.; Holloway, A. J. (2004). "The bipolarity of the highest Galactic latitude planetary nebula, LoTr 5 (PN G339.9+88.4), around IN Com". Monthly Notices of the Royal Astronomical Society. 347 (4): 1370–1378. Bibcode:2004MNRAS.347.1370G. doi:10.1111/j.1365-2966.2004.07342.x.
  4. Jasniewicz, G.; Thevenin, F.; Monier, R.; Skiff, B. A. (1996). "The central star of LoTr 5 revisited". Astronomy and Astrophysics. 307: 200. Bibcode:1996A&A...307..200J.
  5. "PN LoTr 5". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-03-01.
  6. Aller, A.; Lillo-Box, J.; Vučković, M.; Van Winckel, H.; Jones, D.; Montesinos, B.; Zorotovic, M.; Miranda, L. F. (2018). "A new look inside planetary nebula LoTr 5: A long-period binary with hints of a possible third component". Monthly Notices of the Royal Astronomical Society. 476 (1): 1140–1150. arXiv:1801.06032. Bibcode:2018MNRAS.476.1140A. doi:10.1093/mnras/sty174. S2CID 119477283.
  7. Longmore, A. J.; Tritton, S. B. (1980). "A second list of new planetary nebulae found on United Kingdom 1.2-m Schmidt telescope plates". Monthly Notices of the Royal Astronomical Society. 193 (3): 521–524. Bibcode:1980MNRAS.193..521L. doi:10.1093/mnras/193.3.521.
  8. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....1.2025S.
  9. Douchin, Dimitri; De Marco, Orsola; Frew, D. J.; Jacoby, G. H.; Jasniewicz, G.; Fitzgerald, M.; Passy, Jean-Claude; Harmer, D.; Hillwig, Todd; Moe, Maxwell (2015). "The binary fraction of planetary nebula central stars – II. A larger sample and improved technique for the infrared excess search". Monthly Notices of the Royal Astronomical Society. 448 (4): 3132–3155. Bibcode:2015MNRAS.448.3132D. doi:10.1093/mnras/stu2700.
  10. Alekseev, I. Yu.; Kozhevnikova, A. V. (2004). "Rotational Brightness Modulation and Starspots on the RS CVN-type Stars IN Com, IL Com, UX Ari, and V711 Tau". Astrophysics. 47 (4): 443–453. Bibcode:2004Ap.....47..443A. doi:10.1023/B:ASYS.0000049781.42096.c6. S2CID 120473411.
  11. Feibelman, W. A.; Kaler, J. B. (1983). "The binary central star of the planetary nebula LT-5". The Astrophysical Journal. 269: 592. Bibcode:1983ApJ...269..592F. doi:10.1086/161065.
  12. Thevenin, F.; Jasniewicz, G. (1997). "Barium-rich G stars in the nuclei of the planetary nebulae Abell 35 and LoTr5". Astronomy and Astrophysics. 320: 913. Bibcode:1997A&A...320..913T.
  13. Jasniewicz, G.; Duquennoy, A.; Acker, A. (1987). "The nucleus of LT-5 : An unusual triple system ?". Astronomy and Astrophysics. 180: 145. Bibcode:1987A&A...180..145J.
  14. Malasan, Hakim Luthfi; Yamasaki, Atsuma; Kondo, Masayuki (1991). "The central star of planetary nebula LT-5 - A triple system". The Astronomical Journal. 101: 2131. Bibcode:1991AJ....101.2131M. doi:10.1086/115834.
  15. Jones, D.; Van Winckel, H.; Aller, A.; Exter, K.; De Marco, O. (2017). "The long-period binary central stars of the planetary nebulae NGC 1514 and LoTr 5". Astronomy & Astrophysics. 600: L9. arXiv:1703.05096. Bibcode:2017A&A...600L...9J. doi:10.1051/0004-6361/201730700. S2CID 55371290.
  16. Montez, Rodolfo; De Marco, Orsola; Kastner, Joel H.; Chu, You-Hua (2010). "X-Ray Emission from the Binary Central Stars of the Planetary Nebulae HFG 1, Ds 1, and LoTr 5". The Astrophysical Journal. 721 (2): 1820–1828. arXiv:1008.2910. Bibcode:2010ApJ...721.1820M. doi:10.1088/0004-637X/721/2/1820. S2CID 119232433.
  • Goldman, Don (2012-08-02). "LoTr5". astrodonimaging.com. Retrieved 2020-03-01.
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