IBVS 5473

Rc light curve of X Leonis in April-May, 2003 (left panel). The Rc-Ic color index ranges from =~0.1 to =~0.7 mag (right panel).

Overall Rc light curve of X Leonis. The small crosses represent visual estimates available in the VSNET web site http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/

References:

Brun A., Petit M.,1952, Bull. De L'Assoc. Franc. d'Obser. D'Etoiles Var., 12

Downes R. A., Webbink R. F., Shara M. M. et al., 2001, PASP, 113, 764 (2001PASP..113..764D)

Echevarria, J., 1984, Rev. Mex. Astron. Astrof., 9, 99 (1984RMxAA...9...99E)

Howell S., Szkody P., 1988, PASP, 100, 224 (1988PASP..100..224H)

Landolt A.U., 1992, AJ, 104, 340 (1992AJ....104..340L)

Misselt K.A., 1996, PASP, 108, 146 (1996PASP..108..146M)

Ritter, H., Kolb, U., 1998, A&AS, 129, 83 (1998A&AS..129...83R)

Shafter A. W., Harkness R.P., 1986, AJ, 92, 658 (1986AJ.....92..658S)

Sherrington M. R., Jameson R. F., 1983, MNRAS, 205, 265 (1983MNRAS.205..265S)

Spogli C., Fiorucci M., Tosti G., 1998, A&AS, 130, 485 (1998A&AS..130..485S)

Spogli C., 2003, IBVS, 5240 (IBVS N°.5240)

Szkody P., 1987, ApJS, 63, 685 (1987ApJS...63..685S)

Szkody P., Mateo M., 1986, AJ, 92, 483 (1986AJ.....92..483S)

We observed the variable from February 22 to June 04, 2003, for a total of 36 observational nights. Observations were done with the 0.33 m and 0.24 m telescopes at the Porziano Astronomical Observatory, and with the 0.40 m Automatic Imaging Telescope at the Perugia University Observatory. The instruments used and the photometric techniques have already been described in Spogli et al. (1998) (Spogli, 2003). The telescopes are endowed with standard BVRcIc broad-band filters. Inter-comparison among results obtained with the different instruments shows no relevant systematic difference within the typical standard deviation. The data reported in Table 1 are obtained in differential photometry using the calibration stars reported by Misselt (1996). Moreover, we calibrated these comparison stars with the Ic filter by observing, on two photometric nights, several standard stars (Landolt, 1992) having (B-V) from -0.2 to 1.4, over a wide range of airmass. We followed the light curve in the Rc band, and obtained the color indices during the outburst phase.

Figs. 1 and 2 show the Rc light curve. Intra-night observations indicate the presence of variations in the order of few tenths of magnitude. Analyzing the spectral energy distribution in the optical region, obtained using the same procedure described in Spogli et al. (1998), we have verified the strong contribution of the late-type secondary star to the overall emission. The (V-Ic) color index follows the outburst ranging from =~1.1 at minimum to =~0.2 during the maximum. The same trend is evident for the (Rc-Ic) color index (Fig. 1).

03/03/12

2711.439

16.26±0.05

03/03/14

2713.433

15.77±0.04

03/03/28

2727.328

15.5±0.1

15.13±0.04

14.89±0.05

14.55±0.05

03/03/28

2727.452

15.13±0.04

03/04/05

2734.530

15.55±0.03

03/04/05

2735.399

15.72±0.02

03/04/08

2738.298

15.98±0.08

15.40±0.04

14.88±0.04

03/04/11

2741.495

16.31±0.05

03/04/14

2744.367

16.02±0.05

15.63±0.05

14.91±0.05

03/04/15

2745.358

15.88±0.08

15.52±0.04

15.00±0.04

03/04/22

2752.371

12.28±0.04

12.19±0.04

12.07±0.04

03/04/23

2752.504

12.56±0.05

12.40±0.03

12.16±0.03

12.03±0.04

03/04/24

2753.505

12.03±0.05

03/04/24

2753.518

12.31±0.03

03/04/24

2754.459

12.51±0.05

12.42±0.03

12.31±0.03

12.15±0.04

03/04/25

2755.416

12.20±0.03

03/04/25

2755.425

12.23±0.04

03/04/25

2755.443

12.25±0.04

03/04/25

2755.453

12.42±0.04

03/04/26

2755.505

12.80±0.05

12.55±0.05

12.37±0.03

12.29±0.04

03/04/27

2756.505

12.61±0.04

03/04/27

2757.382

12.62±0.05

03/04/27

2757.403

12.69±0.05

03/04/27

2757.414

12.75±0.05

03/04/28

2758.436

13.46±0.05

13.25±0.05

13.07±0.05

12.95±0.04

03/04/29

2759.436

13.52±0.05

03/04/29

2759.443

13.41±0.05

03/04/29

2759.445

13.48±0.05

03/04/29

2759.451

13.58±0.05

03/04/29

2759.467

13.47±0.05

03/04/30

2760.474

14.6±0.1

14.33±0.04

14.03±0.05

13.72±0.04

03/04/30

2760.477

14.05±0.05

03/04/30

2760.482

14.11±0.05

03/05/01

2761.436

14.38±0.05

03/05/01

2761.465

14.48±0.05

03/05/01

2761.470

14.56±0.05

03/05/01

2761.481

14.87±0.05

03/05/02

2762.452

15.25±0.05

03/05/03

2763.454

15.18±0.05

03/05/04

2764.499

15.16±0.05

03/05/05

2764.506

15.38±0.05

03/05/05

2764.512

15.58±0.05

03/05/05

2764.522

15.28±0.05

Table 1: BVRcIc magnitudes of X Leonis (continued)

Date

(2450000+)

03/05/05

2765.428

15.61±0.05

03/05/06

2766.427

15.12±0.05

03/05/06

2766.445

15.35±0.05

03/05/13

2773.415

12.74±0.05

03/05/15

2775.431

13.32±0.05

03/05/15

2775.442

13.24±0.05

03/05/15

2775.449

13.39±0.05

03/05/15

2775.457

13.29±0.05

03/05/16

2776.467

13.52±0.05

03/05/19

2779.438

15.14±0.05

03/05/22

2782.433

15.12±0.05

03/05/23

2783.457

15.35±0.05

03/05/28

2788.438

15.11±0.04

03/05/28

2788.447

15.42±0.04

03/05/31

2791.459

15.45±0.04

03/06/04

2795.445

12.99±0.06

Table 1: BVRcIc magnitudes of X Leonis

Date

(2450000+)

03/02/22

2693.493

15.36±0.04

03/03/07

2706.441

15.11±0.05

03/03/08

2707.456

15.10±0.03

SIMBAD object(s): X Leo

Dwarf Novae (DN) are a type of cataclysmic variable stars that undergo recurrent outbursts during which they increase in brightness by 2-8 magnitudes. X Leo is a dwarf nova that varies from 12.4 V to 16.5 V (Downes et al., 2001), and the recurrence time of two consecutive outbursts is approximately between 8 and 38 days (Ritter & Kolb, 1998). Brun and Petit (1952) considered X Leonis the prototype of a sub-group of DN characterized by asymmetrical maximum of outbursts, frequently of brief duration. The star was studied spectroscopically by Shafter & Harkness (1986), they found an orbital period of 0.1644 days. Multi-bands photometric observations were reported by Echevarria (1984), Sherrington & Jameson (1983), and Szkody (1987). Near-infrared intra-night observations indicate possible ellipsoidal variations (Szkody & Mateo, 1986), not confirmed in the optical (Howell & Szkody, 1988). The secondary star is classified as an M2 V (Ritter & Kolb, 1998).

IBVS - KONKOLY OBSERVATORY, BUDAPEST, HUNGARY - ABOUT THIS DOCUMENT - ToC ENTRY FOR THIS ISSUE

COMMISSIONS 27 AND 42 OF THE IAU

INFORMATION BULLETIN ON VARIABLE STARS

Number 5473

Konkoly Observatory

Budapest

3 November 2003

HU ISSN 0374 - 0676 (print)

HU ISSN 1587 - 2440 (on-line)

Observations of the Dwarf Nova X Leonis

Spogli, Corrado (1),(2); Fiorucci, Massimo (1); Capezzali, Daniele (1),(2); Brunozzi, Paolo (2); Fagotti, Paolo (2); Mancinelli, Vannio (2); Sensi, Angelo (2); Fagotti, Barbara (2)

(1) Dipartimento di Fisica, Università di Perugia, Via A. Pascoli, 06123 Perugia, Italy

(2) Gruppo Astrofili Monte Subasio, Piazza Santa Chiara 2, 06081 Assisi, Italy