HD 196775

HD 196775 (HR 7899) is a solitary star in the equatorial constellation Delphinus. It has an apparent magnitude of 5.98, allowing it to be faintly seen with the naked eye. The object is relatively far at a distance of 1,050 light years but is approaching the Solar System with a heliocentric radial velocity of −4.6 km/s. HD 196775 has a high peculiar velocity of 21.8+1.9
−4.1 km/s^[6] compared to neighboring stars, indicating that it may be a runaway star.

ConstellationDelphinus^[1]

Right ascension20^h 39^m 04.9681^s^[2]

Declination+15° 50′ 17.511″^[2]

Apparentmagnitude(V)5.98^[3]

Quick facts Constellation, Right ascension ...

HD 196775
Observation data Epoch J2000.0 Equinox J2000.0 (ICRS)
Constellation	Delphinus^[1]
Right ascension	20^h 39^m 04.9681^s^[2]
Declination	+15° 50′ 17.511″^[2]
Apparent magnitude (V)	5.98^[3]
Characteristics
Evolutionary stage	main sequence^[2]
Spectral type	B3 V^[4]
U−B color index	−0.71^[3]
B−V color index	−0.16^[3]
Astrometry

Radial velocity (R_v)	−4.6±1^[5] km/s
Proper motion (μ)	RA: −0.868 mas/yr^[2] Dec.: −15.290 mas/yr^[2]
Parallax (π)	3.1211±0.0617 mas^[2]
Distance	1,050 ± 20 ly (320 ± 6 pc)
Absolute magnitude (M_V)	−2.05^[1]

Details

Mass	7±0.4^[6] `M`_☉
Radius	4.13±0.14^[7] `R`_☉
Luminosity	1,507^[8] `L`_☉
Surface gravity (log g)	3.97^[9] cgs
Temperature	18,100^[9] K
Rotational velocity (v sin i)	145±6^[10] km/s
Age	36.1±9.5^[6] Myr

Other designations
AG+15°2265, BD+15°4220, GC 28785, HD 196775, HIP 101909, HR 7899, SAO 106347, WDS J20391+1550A
Database references
SIMBAD	data

HD 196775 has a general stellar classification of B3 V,^[4] indicating that it is an ordinary B-type main-sequence star. However, once source gives it a class of B4 Vn,^[11] making it slightly cooler and having broad absorption lines due to rapid rotation. It has an angular diameter of 0.12 mas,^[12] yielding a radius 4.13 times that of the Sun.^[7] At present it has 7 times the mass of the Sun^[6] and shines at 1507 L_☉^[8] from its photosphere at an effective temperature of 18,100 K,^[9] giving it a whitish blue hue. HD 196775 is 36 million years old^[6] and is spinning rapidly with a projected rotational velocity of 145 km/s.^[10]

HD 196775 has four faint optical companions whose parameters are listed below.

More information Companion, mv ...

HD 196775's Companions^[13]
Companion	m_v	PA (°)	Year	Sep. (″)
B	12.40	154	2006	5.2
C	11.31	122	2012	39.9
D	14.40	146	2012	28.8
E	14.40	33	2012	23.3

[1]
Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. XHIP record for this object at VizieR.
[2]
Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
[3]
Oja, T. (September 1984). "UBV photometry of stars whose positions are accurately known". Astronomy and Astrophysics Supplement Series. 57: 357–359. Bibcode:1984A&AS...57..357O. ISSN 0365-0138.
[4]
Cucchiaro, A.; Jaschek, M.; Jaschek, C.; Macau-Hercot, D. (May 1980). "Spectral classification from the ultraviolet line features of S2/68 spectra". Astronomy and Astrophysics Supplement Series. 40: 207–213. Bibcode:1980A&AS...40..207C. ISSN 0365-0138.
[5]
Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. ISSN 1063-7737. S2CID 119231169.
[6]
Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (October 12, 2010). "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun". Monthly Notices of the Royal Astronomical Society. 410 (1). Oxford University Press (OUP): 190–200. arXiv:1007.4883. Bibcode:2011MNRAS.410..190T. doi:10.1111/j.1365-2966.2010.17434.x. ISSN 0035-8711.
[7]
Lang, Kenneth R. (2006). Astrophysical formulae. Astronomy and astrophysics library. Vol. 1 (3 ed.). Birkhäuser. ISBN 3-540-29692-1.. The radius (R_*) is given by:
${\begin{aligned}2\cdot R_{*}&={\frac {(320\cdot 0.12\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 8.26\cdot R_{\bigodot }\end{aligned}}$
[8]
McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (21 November 2012). "Fundamental parameters and infrared excesses of Hipparcos stars: Parameters and IR excesses from Hipparcos". Monthly Notices of the Royal Astronomical Society. 427 (1): 343–357. arXiv:1208.2037. Bibcode:2012MNRAS.427..343M. doi:10.1111/j.1365-2966.2012.21873.x. ISSN 0035-8711.
[9]
Lyubimkov, L. S.; Rostopchin, S. I.; Lambert, D. L. (21 June 2004). "Surface abundances of light elements for a large sample of early B-type stars – III. An analysis of helium lines in spectra of 102 stars". Monthly Notices of the Royal Astronomical Society. 351 (2): 745–767. Bibcode:2004MNRAS.351..745L. doi:10.1111/j.1365-2966.2004.07825.x. eISSN 1365-2966. ISSN 0035-8711.
[10]
Bragança, G. A.; Daflon, S.; Cunha, K.; Bensby, T.; Oey, M. S.; Walth, G. (October 1, 2012). "Projected Rotational Velocities and Stellar Characterization of 350 B Stars in the Nearby Galactic Disk". The Astronomical Journal. 144 (5). American Astronomical Society: 130. arXiv:1208.1674. Bibcode:2012AJ....144..130B. doi:10.1088/0004-6256/144/5/130. ISSN 0004-6256.
[11]
de Vaucouleurs, A. (August 1, 1957). "Spectral Types and Luminosities of B, A and F Southern Stars". Monthly Notices of the Royal Astronomical Society. 117 (4). Oxford University Press (OUP): 449–462. Bibcode:1957MNRAS.117..449D. doi:10.1093/mnras/117.4.449. ISSN 0035-8711.
[12]
Bourgés, L.; Lafrasse, S.; Mella, G.; Chesneau, O.; Bouquin, J. L.; Duvert, G.; Chelli, A.; Delfosse, X. (May 2014). "The JMMC Stellar Diameters Catalog v2 (JSDC): A New Release Based on SearchCal Improvements". Astronomical Data Analysis Software and Systems Xxiii. 485: 223. Bibcode:2014ASPC..485..223B.
[13]
Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (December 2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466–3471. Bibcode:2001AJ....122.3466M. doi:10.1086/323920. ISSN 0004-6256.

References

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