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In this brief paper we present B, V, Rc, Ic photometric observations of a sample of dwarf novae made in the years 1998-2002. We are mainly interested to obtain multi-color data of a large sample of DNe during all the outburst-cycle, a work that requires large availability of well-equipped small telescopes and generally good weather conditions for many days. Here we present the sporadic observations that do not cover the outbursts cycle because were obtained during the stand-still, or interrupted for persisting bad weather conditions. However, these informations are useful for a historical database of this class of sources, and because for many of them there are no optical color indices reported in the literature.

The photometric data were mainly obtained with the 0.72 m telescope of the Teramo Astronomical Observatory, and the 0.40 m Automatic Imaging Telescope of the Perugia University Observatory (Tosti et al., 1996). The instruments used and the photometric techniques have already been described in Spogli et al. (1998, 2000). We have also used the 0.24 m Schmidt-Cassegrain f/6.3 telescope equipped with an HISIS 23 CCD camera (Kodak 401-E, 768×512 pixels), and the 0.33 m Newtonian f/4.5 telescope equipped with an MX-916 CCD camera (768×512 pixels), of the ``Subasio'' astronomical station. Both the telescopes are endowed with a standard Rc Cousins broad-band filter. A comparison with results obtained with the other telescopes shows no relevant systematic difference within the typical standard deviation of each instrument. The data reported in Table 1 are obtained in differential photometry using the calibration stars reported in Misselt (1996). Moreover, we calibrated these comparison stars with the Ic filter by observing, on photometric nights, several standard stars (Landolt, 1992) having (B-V) from -0.2 to 1.4, over a wide range of airmass.

Spogli, Corrado (1),(3); Fiorucci, Massimo (1); Raimondo, Gabriella (2); Monacelli, Giuseppe (3); Capezzali, Daniele (3)

(1) Osservatorio Astronomico, Università di Perugia, Via A. Pascoli, I-06123 Perugia, Italy

(2) INAF - Teramo Astronomical Observatory, Collurania, Italy

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

Dwarf Novae (DNe) are a subclass of cataclysmic variable stars, which are close binary systems in which matter transferred from a Roche-lobe filling secondary star is accreted by a primary white dwarf (Warner, 1995). In dwarf novae accretion proceeds through a disk which is the site of more or less regular outbursts. The recurrence time of these 2-6 mag outbursts can range from 10 days to several years. Dwarf novae can be divided into three subclasses: U Gem-type stars which have the most regular outburst cycles, SU UMa-type stars showing both short and very long outbursts (super-outbursts), and Z Cam stars. The last group is characterized by a ``standstill'' phenomenon: the decline from the outburst maximum is interrupted and the luminosity of the system settles to a value of   0.7 mag lower than the peak luminosity. Such standstill may last from ten days to years and, after that phase, the system luminosity declines to the usual quiescent state.

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 5420

Konkoly Observatory

Budapest

26 May 2003

HU ISSN 0374 - 0676  (print)

HU ISSN 1587 - 2440  (on-line)

BVRI Photometry of Dwarf Novae

------------------------------------------

ugSS

98/08/26

1052.398

16.9±0.2

98/09/01

1057.529

18.1±0.3

17.1±0.2

V632 Cyg

02/11/15

2594.405

13.47±0.05

02/11/22

2601.413

11.03±0.03

02/12/29

2638.237

13.98±0.03

ugSU

98/09/02

1058.597

16.4±0.2

16.1±0.1

15.76±0.05

ugSS

00/08/18

1775.463

14.43±0.08

14.12±0.08

13.93±0.08

00/08/23

1780.411

16.2±0.1

15.94±0.05

00/08/25

1782.328

16.5±0.1

16.2±0.1

15.75±0.03

00/08/29

1786.323

14.6±0.1

14.33±0.05

14.21±0.08

14.03±0.03

ugSS

00/08/29

1786.491

14.51±0.08

14.19±0.05

14.05±0.08

13.92±0.03

00/09/08

1796.428

15.43±0.08

15.21±0.05

14.93±0.05

14.68±0.04

00/09/09

1797.452

14.12±0.07

14.05±0.05

14.01±0.08

13.89±0.03

00/09/26

1814.493

16.9±0.1

16.3±0.1

16.1±0.1

15.60±0.05

98/09/01

1057.621

11.96±0.02

11.82±0.02

11.67±0.02

11.41±0.02

98/09/02

1058.523

11.97±0.02

11.84±0.02

11.62±0.03

11.42±0.02

98/09/02

1058.618

12.03±0.02

11.78±0.02

11.65±0.03

11.38±0.02

98/09/03

1059.527

12.08±0.02

11.87±0.02

11.67±0.02

11.45±0.02

98/09/03

1059.528

12.06±0.02

11.82±0.02

11.70±0.02

11.46±0.02

98/09/03

1059.621

12.04±0.02

11.90±0.02

11.73±0.02

11.42±0.02

98/09/03

1060.411

12.14±0.04

11.95±0.02

11.76±0.03

11.48±0.02

98/09/10

1067.379

12.17±0.03

12.02±0.02

11.86±0.02

11.53±0.02

HT Cas

V516 Cyg

V516 Cyg

98/09/03

1060.429

16.95±0.04

16.49±0.02

16.05±0.02

15.22±0.04

98/09/06

1063.446

16.76±0.02

15.56±0.02

98/09/10

1067.431

17.23±0.03

16.89±0.02

16.32±0.02

15.72±0.04

BV And

ug:

98/08/28

1053.501

18.1±0.2

17.9±0.2

17.7±0.2

DX And

ug

98/08/27

1053.489

15.01±0.02

14.34±0.03

13.87±0.05

98/08/31

1057.402

15.55±0.02

14.76±0.02

14.11±0.02

13.68±0.04

98/09/01

1058.397

15.52±0.02

14.68±0.02

14.17±0.03

13.72±0.03

98/09/02

1059.457

15.26±0.02

14.58±0.04

13.99±0.06

13.61±0.05

FO And

ugSU

02/11/22

2601.429

14.81±0.05

FS And

ugSU:

02/12/29

2638.281

16.8±0.1

RX And

ugz

98/08/27

1052.547

11.87±0.02

11.77±0.02

11.63±0.02

11.38±0.02

98/08/28

1053.563

11.88±0.03

11.78±0.02

11.65±0.02

11.39±0.02

98/08/31

1056.537

11.99±0.02

11.85±0.02

11.66±0.02

11.43±0.02

98/08/31

1056.611

12.03±0.02

11.84±0.02

11.67±0.02

11.42±0.02

98/09/01

1057.542

11.90±0.03

11.77±0.03

11.62±0.02

11.34±0.02

*) from Downes et al. (2001)

Name

Type*

Date

JD

B

V

Rc

Ic

UT

(245+)

AR And

ug

98/08/28

1053.538

16.49±0.02

16.25±0.01

15.44±0.02

98/08/31

1056.555

16.89±0.04

16.51±0.02

16.05±0.01

15.34±0.03

98/09/01

1057.590

16.67±0.03

16.38±0.02

15.96±0.02

15.30±0.02

98/09/02

1058.598

16.85±0.04

16.56±0.02

16.05±0.02

15.38±0.03

98/09/03

1059.574

16.71±0.04

16.35±0.02

15.92±0.03

15.20±0.02

The selected dwarf novae have been observed in different phases of luminosity: a few of them were in outburst, others at minimum or in stand-still. For the dwarf novae that were in outburst at the time of the observations, we calculated the spectral index {alpha} (Table 2) using the same procedure described in Spogli et al. (1998) and neglecting interstellar reddening.

Table 1: BVRcIc magnitudes of some Dwarf Novae

 

 

TX Tri

ugSS

98/09/03

1059.583

16.5±0.1

TW Tri

ugz

98/09/03

1059.603

16.7±0.1

16.4±0.1

SW Vul

ug

98/08/31

1056.509

19.1±0.3

18.4±0.3

17.9±0.2

17.7±0.2

VW Vul

ugSU

98/08/30

1056.413

18.1±0.2

17.7±0.2

16.4±0.1

Table 1: BVRcIc magnitudes of some Dwarf Novae (continues)

 

 

Name

Type*

Date

JD

B

V

Rc

Ic

UT

(245+)

V1028 Cyg

ugSU

98/08/26

1052.435

16.3±0.1

V1032 Cyg

ug

98/08/26

1052.440

16.1±0.1

V1052 Cyg

ugSS

98/08/26

1052.444

15.38±0.05

V1060 Cyg

ugSS

98/08/26

1052.464

16.1±0.1

V1316 Cyg

ugSU

98/09/01

1058.454

17.8±0.3

17.4±0.2

17.3±0.2

V1377 Cyg

ug:

98/08/26

1052.462

15.51±0.05

MN Lac

ugz

98/08/30

1056.493

15.69±0.07

14.99±0.05

14.59±0.04

CN Ori

ugz

02/02/11

2317.327

12.68±0.07

12.77±0.05

12.68±0.04

12.41±0.04

02/02/22

2328.329

15.92±0.09

15.31±0.05

14.91±0.05

14.34±0.05

02/03/04

2338.326

13.48±0.09

12.99±0.05

12.85±0.04

12.55±0.04

02/03/10

2344.361

17.4±0.2

16.1±0.1

15.44±0.05

14.59±0.05

CZ Ori

ug

98/03/10

0883.357

16.3±0.1

15.85±0.05

14.84±0.04

98/03/14

0887.381

14.50±0.05

14.08±0.04

98/03/16

0889.317

12.81±0.06

12.67±0.05

12.62±0.04

12.39±0.04

98/03/17

0890.312

12.67±0.07

12.82±0.05

12.64±0.04

12.43±0.04

98/03/18

0891.313

12.89±0.07

13.03±0.05

12.90±0.04

12.65±0.04

98/03/27

0900.313

16.8±0.1

16.35±0.08

15.74±0.05

14.89±0.04

98/03/29

0902.317

16.1±0.1

15.72±0.05

14.87±0.04

99/03/01

1239.393

14.41±0.05

13.99±0.05

13.69±0.04

99/03/03

1241.387

15.23±0.05

14.71±0.04

99/03/10

1248.375

16.00±0.08

15.01±0.05

99/03/11

1249.361

16.36±0.05

16.03±0.05

15.06±0.04

IP Peg

ug

98/08/28

1053.517

16.5±0.1

15.80±0.04

15.24±0.05

RU Peg

ugSS

98/09/03

1059.501

12.53±0.02

12.11±0.02

11.82±0.02

FO Per

ug

98/08/31

1056.628

14.01±0.05

13.77±0.05

13.57±0.05

13.29±0.04

98/09/01

1057.562

14.11±0.05

13.86±0.05

13.57±0.05

13.36±0.04

98/09/02

1058.637

14.42±0.03

14.19±0.03

13.91±0.03

13.62±0.03

98/09/03

1059.614

14.98±0.04

14.81±0.02

14.57±0.04

14.24±0.03

02/02/11

2317.309

15.06±0.06

15.03±0.03

14.82±0.05

14.49±0.03

02/02/22

2328.306

13.92±0.04

13.75±0.03

13.62±0.05

02/02/24

2330.312

14.85±0.05

14.42±0.05

14.37±0.05

02/03/10

2344.311

14.03±0.03

13.86±0.05

13.57±0.04

02/03/11

2345.291

14.19±0.03

14.03±0.03

13.86±0.05

13.58±0.04

02/03/13

2347.286

16.2±0.2

15.79±0.05

15.43±0.06

02/03/23

2357.297

17.3±0.3

17.0±0.2

16.2±0.1

02/03/29

2363.293

13.61±0.03

13.38±0.04

13.20±0.05

02/03/30

2364.294

13.65±0.05

13.53±0.05

13.21±0.05

KT Per

ugz

00/08/26

1782.515

12.84±0.05

12.75±0.05

00/08/29

1786.499

16.1±0.1

15.57±0.05

15.18±0.05

00/08/30

1786.560

15.89±0.05

15.47±0.05

00/09/09

1796.655

15.82±0.07

15.56±0.05

14.99±0.05

14.35±0.05

00/09/11

1799.464

15.53±0.05

15.05±0.05

14.21±0.05

00/09/23

1810.511

16.30±0.08

15.86±0.06

15.37±0.05

14.37±0.05

00/09/27

1814.513

12.85±0.06

12.71±0.05

12.52±0.04

12.33±0.04

00/09/27

1814.573

12.78±0.07

12.69±0.05

12.53±0.04

12.35±0.04

00/09/28

1815.535

12.69±0.07

12.53±0.05

12.38±0.04

12.17±0.04

00/10/12

1830.342

14.21±0.05

00/10/28

1846.323

14.48±0.07

TU Tri

ug

98/09/03

1059.586

18.3±0.2

*) from Downes et al. (2001)

Table 2: Mean spectral slope (F({nu}) {proportional to}{nu}{alpha}) of some DNe

 

 

Name

Type*

Magnitude Range*

Obs. Values

{alpha}

RX And

ugz

10.9 v

12.6 v

V =~ 11.8

0.2 ±0.1

V516 Cyg

ugSS

13.8 p

16.8 p

V =~ 14.1

0.3 ±0.2

CN Ori

ugz

11.9 v

16.3 v

V =~ 12.8

0.5 ±0.2

CZ Ori

ug

11.2 V

17.0 V

V =~ 12.7

0.4 ±0.2

FO Per

ug

11.8 v

16.2 p

V =~ 13.8

0.0 ±0.2

KT Per

ugz

10.6 V

16.1 V

V =~ 12.6

0.3 ±0.1

*) from Downes et al. (2001)

References:

 

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

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

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

Spogli, C., Fiorucci, M., Raimondo, G., 2000, IBVS, 4944 (IBVS N°.4944)

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

Tosti, G., Pascolini, S., Fiorucci, M., 1996, PASP, 108, 706 (1996PASP..108..706T)

Warner, B., 1995, ``Cataclysmic Variable Stars'', Cambridge University Press, Cambridge