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  HZ Her  
000-BBY-240 (12606 observations)  
Hercules Sequence
16 57 49.80 +35 20 33.0  (254.45750 +35.34250) Search nearby
B1950.0 16 56 01.74 +35 25 05.4
Galactic coord. 58.149 +37.523
Other names

(Internal only)
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1SWASP J165749.80+352032.8 2RXP J165749.4+352033 AAVSO 1654+35
AN 142.1936 Her X-1 ROTSE1 J165749.74+352032.4
X 16560+354    
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Variability type
Spectral type B0Ve-F5e
Mag. range
12.8 - 15.2 B
Discoverer --
21 Mar 1972 (HJD 2441397.584) Ephemeris
Outburst --
Period 1.700175 d
Rise/eclipse dur. --
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1 Otero, Sebastian Alberto The main photometric period of 34.875 d. is caused by the precession of the neutron star accretion disk and the reflection effect. Orbital elements: 2441397.584 + 1.700175 x E. X-ray eclipses.
2 GCVS Team Her X-1 = 4U 1656 + 35. Lx/Lopt = 2 - 60. The Table gives elements for light minima due to eclipsing variability and the reflection effect. Min I coincides with the X-ray eclipse. Shallow Min II may be present. The reflection effect causes variations with Delta(m) up to 1.5m. A cycle of 34.875d duration is observed in X-ray band; the source is faint during two thirds of the cycle. The optical light curve changes are observed during the 35d cycle [N.E.Kurochkin, Perem. Zvezdy 18, N5, 425, 1972.]. According to [W.Wenzel, H.Gessner, MVS 6, H.3, 61, 1972.], during JD2427543 - 657 and JD2428630 - 29789 the strong reflection effect was absent; the star was still varying with P = 1.7d and had Delta(m) ~0.5m, Min I = Min II. In [C.A.Jones, Wm.Forman, Wm.Liller, BAAS 5, N1, part 1, 32, 1973.] it is stated that such intervals with no reflection effect, of 8d to 7a duration, took place for almost half the time since 1890. The light changes during such intervals are in the range 14.7m - 15.2m pg. Since 1957 intervals without the reflection effect were not observed. In June - July 1983 the predicted phases of high X-ray flux did not take place, but the reflection effect did not disappear [IAU Circ N3841, 1983.]. Secondary light variations: P1 = 1.0977d (delta(B1) = 0.33m), P2 = 0.871173d*E (delta(B2) = 0.10m), P3 = 1.623846d*E (delta(B3) = 0.17m) [N.E.Kurochkin, Pis'ma Astron. Zh. 1, N7, 27, 1975.]. X-ray pulsar, P = 1.2377991s (JD2443357), dP/dt/P = (-2.9 +- 0.2)*10**(-6)/yr [P.C.Joss, F.Li, J.Nelson, J.Middleditch, ApJ 235, 592, 1980.], sometimes noticeable also in the optical range [D.O.Lamb, J.M.Sorvari, IAU Circ N2422, 1972.]. Rapid brightness flickering.
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1 J. Alfonso-Garzon, A. Domingo, J.M. Mas-Hesse, A. Gimenez, 2012,
arXiv:1210.0821 [astro-ph.IM] (online info)
2 Multicolor photoelectric WBVR observations of the close binary system HZ
Her = Her X-1 in 1986-1988. Method and observations
3 Norton A.J. et al., 2007, astro-ph/0702631 2007astro.ph..2631N
4 C.Akerlof et al., AJ 119, 1901, 2000. 2000AJ....119.1901A
5 R.Hudec, W.Wenzel, BAC 27, N6, 325, 1976. 1976BAICz..27..325H
6 N.E.Kurochkin, Perem. Zvezdy 18, N5, 425, 1972. 1972PZ.....18..425K
7 Bob Nelson's O-C files, 2016 --
8 -- --
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Revision History
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3 Otero, Sebastian Alberto 2011-05-23 20:23 UTC Primary record creation. Variability and spectral type from reference.
2 Admin, VSX 2010-01-04 23:43 UTC Position updated from the GCVS version of November 2009.
1 Admin, VSX 2005-12-17 20:33 UTC Initial upload.