PoS(HTRA-IV)048 http://pos.sissa.it/ ∗ [email protected] [email protected] [email protected] [email protected] [email protected] Speaker. HU Aqr is an eclipsingdwarf CV with a system period hosting of asince about highly 1993. 125 magnetic min. Regular white OPTIMA dwarf Itsfollow observations orbited the orbital of secular by ephemeris changes eclipses a has of of M4V been theincluding HU binary followed recent orbit. Aqr with 2008/2009 since We precision observations report 1999 and new can modelingterm find as of be that well the a used as orbital model two to ephemeris sinusoidal includingpropose oscillatory a terms that linear provides the the and best sinusoidal quadratic fit variationsorbit to can around the be HU observed eclipses. Aqr. explained We by the presence of two giant planets in ∗ © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. High Time Resolution Astrophysics (HTRA) IVMay - 5 The - Era 7, of 2010 Extremely LargeAgios Telescopes Nikolaos, Crete Greece Robert Schwarz Astrophysikalisches Institut Potsdam, An der SternwarteE-mail: 16, D14482 Potsdam, Germany Axel. D. Schwope Astrophysikalisches Institut Potsdam, An der SternwarteE-mail: 16, D14482 Potsdam, Germany Gottfried Kanbach Max Planck Institute for Extraterrestrial Physics,Germany Giessenbachstrasse 1, 85741 Garching, E-mail: Max Planck Institute for Extraterrestrial Physics,Germany Giessenbachstrasse 1, 85741 Garching, Department of Physics, University of Cukurova,E-mail: 01330 Adana, Turkey Agnieszka Słowikowska Institute of Astronomy, University of ZielonaE-mail: Góra, Lubuska 2, 65-265 Zielona Góra, Poland Ilham Nasiroglu The orbital ephemeris of HU AquariiOPTIMA. observed Are with there two giant planets in orbit? PoS(HTRA-IV)048 , 2 4 χ 2.1 , 3 (2.2) (2.3) (2.1) 0.2 years. ] s [ ] ± s [ } Ilham Nasiroglu ) } ) ] 184 ( ) and to prevent the 664 ( orb BJED 25742 = P )[ / 64426 2 ( )] / spin )] 239 ]. ( 2 569 , ’ values of the linear ephemeris is ( 1 1 ). To determine a uniform time stamp 2229 0.8 s has a period of 15.3 C) 1 9980 − − 0868204073 ± . − E 0 [ E π [ × 7, . π w.r.t to the ephemeris including the Eqns. × E 2 2 × 11 2 ) { 2 ) + C ∼ { sin 79 − 141 and the mean error in the last digits for each term alculated ’(O of ( sin × C O 2 ∼ ) ( × χ 4 ) is ( 6 2 . 79 ( χ 6 9200653 . 14 . . A second least-squares sine fit to these residual values yields a ) + 13 335 2(b) ( ) + bserved minus 2449102 O 59 324 ( . = 0 75 ]) with a sigmoidal function and took the half intensity point as reference (see . = . Assuming that all the O-C values show a roughly sinusoidal variation we 6 7 2 MinI ) = 2(a) C 1 ) G) are a subgroup of magnetic CVs. In these systems the magnetic field of the WD − C 8 O − ( are plotted in Fig. 10 O ( − Linear ephemeris ). Observations and eclipse egress times were converted to Barycentric Julian Ephemeris 38: 2.2 7 1 This sinusoidal variation with an amplitude of 13.1 The baseline linear fit to all observed egress times yields the ephemeris Min I (in BJED), where Magnetic cataclysmic variables (CVs, Polars) are interacting close binary systems in which To follow the secular changes of the orbital period, the eclipse times of HU Aqr have been The corresponding • ∼ 10 ]. We have now generated new fits to eclipse egress times in HU Aqr that include recent 2008/2009 of The remaining residuals of egressand times second cyclic ephemeris with a reduced applied a least-squares sine fit that reveals the following ephemeris equation with the reduced is given in parentheses: E is the orbital epoch. The reduced formation of an accretion disk around thePolar WD. systems The with eclipsing visual system magnitudes HU ranging Aqr is from one 15 of to the 18 brightest [ observations at Skinakas Observatory, Crete, Greece (Tab. Dates (BJED). The reference time2449102.9201(1) for BJED, eclipse but is egress also epoch fitted zero within is the range 1993 of April uncertainty 25 in 10:04:56(10) each individual = 2. model. Ephemeris Calculation of HU Aqr 5 Fig. material flows from awhite Roche dwarf (WD). lobe Polars filling (a.k.a.∼ low AM mass Her companion stars) and including is a WD accreted with by strong a magnetic magnetic field (B observed in optical, UVTiming and Analyzer) X-rays observations over since the 1999.extending last In the 17 total work years, 111 of Schwope eclipse including et egress regular al. times OPTIMA have (2001), (Optical been Vogel et collected, al. (2008), and Schwarz et al. (2009) [ The orbital ephemeris of HU Aquarii 1. Introduction is sufficiently high to lock the system into synchronous rotation (P for the egress timesfrom we 450-900 fitted nm [ the OPTIMA count rates (intensity in a white light band ranging shown in Fig. PoS(HTRA-IV)048 ) = x ( y x was found ∆ ’the mid-point’ Ilham Nasiroglu 0 x BJED (b) ∆ 3 (c) are the levels before and after egress and 2 A and 1 A . ) x Eclipse egress times of HU Aqr (2008 and 2009). ∆ / ) x − (a) 0 x Table 1: ( Cycle Eclipse Dur. Egress Time 646576488564886 9.72765265 9.73867791 9.732 14716.4673895267917 9.741 14736.26244320 0.00000728 67918 9.711 14736.34926361 0.00000462 68009 9.706 14769.25419933 0.00000188 9.697 14988.56255719 0.00000345 9.735 14999.50192896 0.00000414 14999.58874937 0.00000159 15007.48940676 0.00003162 0.00000249 Number (m) (BJED-2440000+) exp + 1 ( / ) 1 A Representative eclipse measurements of HU Aqr in 2008 and 2009, (a) and (b). The reference 0.5 s. − 2 ± A +( 1 is fitted with an accuracy ofas 0.6 2.7 s in the example for 06 Sep. 2008 (c). The exponential scale Figure 1: for phase = 0 is the mid-time of eclipse egress, which is fitted with a sigmoidal function of the form A The orbital ephemeris of HU Aquarii PoS(HTRA-IV)048 , ]. 7 [ 3(b) (2.6) (2.4) (2.5) c . The 2 ] 2. This = / 3(a) ˙ ] P s [ P dE BJED } / ) Ilham Nasiroglu = ][ c dP C values have been 13 146 − − ± ( 10 ] ) are plotted in Fig. s [ × term is 67 ) } ( 2.5 ) 2 25196 17 81 E ( (b) / . 9 897 )] 29 ( and . + , we can derive 1 2 [ 6 191 2.4 − × ± cE ( 2 46109 10 + / E × )] values yields the new ephemeris with the ) − bE 2890 8, 3 ) . 17 1 699 + − 6 is the orbital period of HU Aqr) and an semi- ( ( C) ( a E ∼ − [ orb 2 204 π P 4 2 ) = χ . A second least-squares sine fitting to these values × { 16167 E ( E − sin T 2(b) − of the quadratic ephemeris is shown in Fig. E ∆ 086820416 [ × ) , and the coefficient of the . , where 3 ) π ) 0 E 71 2 ( C) 34 × { after application of Eqns. 184 − ± E 39 ( 4 ( . sin 9 × C) 04 ) + 91 and mean error for each term: . = − 6 3 73 ∼ 25742 ) ( ]. C ) + = of 5 (a) curve can be described by a combination of a linear and sinusoidal varia- 2 − 25 ω 3 χ O ± ( ( C) 9200370 − . 10 . 6, C diagram of HU Aqr with the remaining sine fit (red line). The O 1 25 and . . − = 27 4 365 ) ∼ / 2449102 2 C (a), O χ orb − = P Quadratic ephemeris O ω ( A weighted quadratic regression to all collected egress times yields the following ephemeris The remaining sine fit results indicates a cyclical variation with a period of 6.12±0.04 years This sine fit reveals a periodic oscillation with a semi-amplitude of 6.0 (±0.3) s and a period The corresponding residual (O The resulting residuals (O • = MinI P Thus, an ephemeris curve that displays arate quadratic form with is proving respect the period to changing at the a constant cycle number general trend of (O tion. Using a second least-squaresreduced fitting on the (O yields a new cyclic ephemeris with the reduced amplitude of 6.6 ±0.4 s. Schwarzyrs et and al. speculated (2009) that found these similar periodica variations variations with variable might periods magnetic occur of field because 13 [ of and shape 6.99 changes induced by (Min I) with a reduced ( of 5.99(±0.03) yr. From a quadratic form calculated according to the ephemerisincluding in models Eq. in (2.1). Eqns. (2.1) (b), and residual (2.2) of with eclipse the egress remaining times fit w.r.t. (red an line) ephemeris according to model in Eq. (2.3). and show periodic variation similar to Fig. The orbital ephemeris of HU Aquarii Figure 2: PoS(HTRA-IV)048 35 = 10 orb Jupiter ˙ ], and × P 5 M [ 1 − ss ) at a distance Ilham Nasiroglu 8 12 squares solution − − 13 seconds, and a − 10 10 − × × ) ) 5 . and the coefficient of the 11 1 P ± − (b) ( / c ... erg) accounts only for a small 2 19 7 . 6 34 − = ˙ = 10 P ] but are not convincingly reconciled = ( ]. These values are all about 3 times 5 × 4 , [ 0 orb 3 . f(m) ˙ 1 P 1 − ss ∼ − 7 sec amplitude. Explanations purely intrinsic 12 − − 5 ]) we conclude that there might be two planets, one ), we calculated a continuous orbital period decrease 10 4 × 2.4 3 . due to orbital period changes caused by a regular stellar 15 years and an amplitude between 10 13 (Eq. (the mass function − − (ii) . Schwope et al. (2001) calculated a period decrease of 13 cyclic movement of the accretion spot on the WD surface due 1 − = − (i) 10 ss Jupiter orb ˙ P × M 12 ) − ) at distance of 3.4 (±0.02) A.U in a 6 (±0.03) years orbit. 17 8 (a) ( 10 − × 29 10 . ) ], Schwarz et al. (2009) estimated 1 4 × 3 . − [ ) 0 7 1 . C diagram of HU Aqr with the best least squares sinusoidal fit (red line). The O-C dif- = ± − 0 c − 0 . ss ± planar orbits (inclination 85.5°,[ 3 ( − 12 − (a),O 77 − . 4 = ( 10 = × The ephemeris models presented here are characterized by the presence of two sinusoidal orb ˙ P coefficient can be determined from the ephemeris curve by a quadratic least 10 f(m) activity cycle of the secondary star have been discussed [ to the binary system into terms of changes in the accretion flow or − larger than our present value,erg. which now Gravitational implies an radiation angular loss momentum from loss the of binary about -1.3 ( short period oscillation over about 6 years and 6 with the data. Theseems quality to of hint the strongly sinusoidalpresence at variations of and an smaller the explanation ’planetary’ presence in bodiessystem of terms orbiting parameters two of the of different compact changes the periods binary HU inarguments at Aqr the presented large binary by light distances. were Qian travel derived et time Thepotential by al. latest planets due Vogel et around to (2010) al. HU for the Aqr. the (2008)move in and system If co we of we follow DP assume the Leo, thatwith to the a derive compact mass the binary of properties and 4.42 of its (±0.28) ’outer’ satellites variations, a long period one over 11 of Vogel et al. (2008) obtained fraction of the angular momentum loss, the dominant part is compatible with3. magnetic breaking. Discussion The orbital ephemeris of HU Aquarii Figure 3: quadratic term of 5.1 (±0.07) A.U( in a 11 (±0.2) years orbit, and another with a mass of 4.05 (±0.2) ferences have been calculated accordingegress to times w.r.t. the an quadratic ephemeris ephemerisaccording including in to models model Eq. in in Eqns. Eq (2.4). (2.6). (2.4) and (b), (2.5) Residual with of the eclipse remaining fitc (red line) that represent the observations correctly. Using the relation PoS(HTRA-IV)048 , 375 , 840 − A&A , , 833 Ilham Nasiroglu 496 , , (2001). , [1995]. A&A , Design and results of the fast c1995 , On the orbital period of the 267 (2008). − The soft X-ray eclipses of HU Aqr Cambridge Univ. Press 93 (2003). , 264 , − 984 , , (2001). , 82 6 Detection of a Giant Extrasolar Planet Orbiting the AIP , 4841 , 68 (2010). Springer , − SPIE , , 66 708 , ApJ , An Introduction to close Binary Stars Cataclysmic variable stars Cambridge Astrophysics Series Cataclysmic variable stars 433 (2001). − Eclipsing Polar DP Leo 419 magnetic cataclysmic variable HU Aquarii Hunting high and low: XMM monitoring of the eclipsing polar HU Aquarii (2009). timing photo-polarimeter OPTIMA A. Słowikowska acknowledges financial support from the Foundation for Polish Science grant [2] Hellier C., [3] A. D. Schwope, R. Schwarz, M. Sirk, and S. B. Howell, [4] J. Vogel, A. Schwope, R. Schwarz, G. Kanbach V. Dhillon T. Marsh, [1] Warner B., [7] R. W. Hilditch, [5] R. Schwarz, A. Schwope, J. Vogel, V. Dhillon, T. Marsh, C. Copperwheat, S. Littlefair, G Kanbach, [6] G. Kanbach, S. Kellner, F. Schrey, H. Steinle, C. Straubmeier, H. Spruit, [8] S. -B. Qian, W.-P. Liao, L.-Y. Zhu, Z.-B. Dai, HOM/2009/11B and the Marie Curie European ReintegrationNasiroglu Grant acknowledges PERG05-GA-2009-249168. support I. from theof EU Neutron FP6 Stars’ Transfer of (MTKD-CT-2006-042722).FP6 Knowledge Project Transfer G. ’Astrophysics of Kanbach Knowledge acknowledges Projecthospitality support of ’ASTROCENTER’ the from (MTKD-CT-2006-039965) Skinakas and the team the at EU kind UoC. We thank Arne Rau forReferences discussions on this paper. The orbital ephemeris of HU Aquarii Acknowledgments