EXor objects are young variables that show episodic variations of brightness commonly associated to enhanced accretion outbursts. With the aim of investigating the long-term photometric behaviour of a few EXor sources, we present here data from the archival plates of the Asiago Observatory, showing the Orion field where the three EXors V1118, V1143, and NY are located. A total of 484 plates were investigated, providing a total of more than 1000 magnitudes for the three stars, which cover a period of about 35yrs between 1959 to 1993. We then compared our data with literature data. Apart from a newly discovered flare-up of V1118, we identify the same outbursts already known, but we provide two added values: (i) a long-term sampling of the quiescence phase; and (ii) repeated multi-colour observations (BVRI bands). The former allows us to give a reliable characterisation of the quiescence, which represents a unique reference for studies that will analyze future outbursts and the physical changes induced by these events. The latter is useful for confirming whether the intermittent increases of brightness are accretion-driven (as in the case of V1118), or extinction-driven (as in the case of V1143). Accordingly, doubts arise about the V1143 classification as a pure EXor object. Finally, although our plates do not separate NY Ori and the star very close to it, they indicate that this EXor did not undergo any major outbursts during our 40yrs of monitoring.
We report 8 years of previously unpublished photometric observations of FK Com. The observations have been carried out between 1993 and 2001 with six different telescopes: 60 cm at Mt. Maidanak (Tashkent, Uzbekistan), Phoenix 10, Wolfgang and Amadeus located in Arizona, USA, and 20cm and 60 cm KVA on La Palma, Spain. Observations contain measurements at the following bands: Johnson U, B, V and R, Bessel R, Cousins I and Stromgren b and y. The observations are differential photometry in respect to the primary comparison star HD 117567. NOTE: Table 1 in the paper contains some small misprints in the Julian dates. Also for Wolfgang and Amadeus the number of observations given in Table1 at each band is slightly less than actually given in Table2c and Table2d. This is caused by accidentally using a limiting error of 0.01 in magnitudes when creating Table 1. In Table 2 the limiting error for Wolfgang and Amadeus is 0.02 mag, as mentioned in the paper itself. In Table2a-e 99.0000 means that no observations were available at that time at that band or that the error in the magnitude was larger than 0.02.
An extensive photometric dataset has been compiled for six Luminous Blue Variables (LBVs). The dataset comprises published and unpublished measurements in the Stroemgren, Geneva and Walraven photometric systems. The measurements within each individual system are presented in a uniform manner. Combining observations from these three photometric systems, a VJ light curve has been constructed for each LBV. Examination of the light curves reveals variations on widely different magnitude and time scales. For explanation about the photometric sytems, see the definitions in the General Catalogue of Photometric Data: about uvby (Stroemgren) <GCPD/04> ; Geneva <GCPD/13> ; Walraven VBLUW <GCPD/11>
As part of our ongoing effort to measure exoplanet sizes and transit times with greater accuracy, we present I-band observations of two transits of OGLE-TR-111b.
We report the discovery of 1RXS J173006.4+033813, a polar cataclysmic variable with a period of 120.21 minutes. The white dwarf primary has a magnetic field of B=42^+6^_-5_MG and the secondary is an M3 dwarf. The system shows highly symmetric double-peaked photometric modulation in the active state as well as in quiescence. These arise from a combination of cyclotron beaming and ellipsoidal modulation. The projected orbital velocity of the secondary is K_2_=390+/-4km/s. We place an upper limit of 830+/-65pc on the distance.
A subset of the RR Lyrae (RRL) candidates identified from the Southern Edgeworth-Kuiper Belt Object (SEKBO) survey data have been followed up photometrically (n=106) and spectroscopically (n=51). Period and light curve fitting reveals a 24+/-7% contamination of SEKBO survey data by non-RRLs. This paper focuses on the region of the Virgo Stellar Stream (VSS), particularly on its extension to the south of the declination limits of the Sloan Digital Sky Survey and of the Quasar Equatorial Survey Team (QUEST) RRL survey.
Photometry of RR Lyr stars in LMC cluster NGC 1835
Short Name:
J/AJ/105/527
Date:
21 Oct 2021
Publisher:
CDS
Description:
Photometry is presented for the RR Lyrae variables in the Large Magellanic Cloud (LMC) cluster NGC 1835. Sixteen new variables have been discovered. Due to the extreme crowding of the LMC field stars, the scatter of the light curves and mean magnitudes is greater than that found for other LMC clusters studied under similar conditions. The derived parameters of the light curves yield E(B-V) = 0.13 and [Fe/H] = -1.8, consistent with previous measurements. The complete sample of RR Lyraes has mean magnitudes <V> = 19.38, <B> = 19.70. If a distance modulus of 18.5 mag for the LMC is assumed, then in the mean the NGC 1835 RR Lyraes have <Mv> = 0.48, almost identical to the average found by the same procedure for the six other LMC clusters.
We present for the first time a catalogue of SX Phe-type pulsating variables in globular clusters. In addition, SX Phe variables discovered in the Carina dwarf galaxy and other ones probably belonging to the Sagittarius dwarf galaxy are included. This catalogue is intended to be an up-dated list of all the SX Phe stars, in globular clusters and galaxies, known until now, covering information published up to January, 2000. In summary, 149 variables are presented in our list for SX Phe-type variables belonging to 18 globular clusters and 2 galaxies. Some relevant distributions are also shown. The analysis of metal abundances and mean periods shows that both parameters are correlated in the sense that the periods of the variables are longer as the metallicity of the stellar system is higher.
Photographic BV photometry has been performed for stars in the southern globular cluster NGC 6139. Equatorial coordinates have been determined for the ten variables recognized in NGC 6139.
Photometric observations of 12 totally eclipsing W UMa binaries (NSVS 3325547, V646 Lac, V1320 Cas, V539 Dra, V816 Cep, NSVS 9045055, V1115 Cas, V902 Cep, V596 Peg, NSVS 1768818, V619 Peg, and NSVS 3198272) are presented. We found that the longer (in phase units) the flat eclipses are, the smaller the mass ratios (or the reciprocal values) are. The mass ratios of five targets turned out close to the lower-mass ratio limit. We found that the periods of V1115 Cas and V646 Lac increase, while that of V596 Peg decreases. Masses, radii, and luminosities of the target components were calculated by the light-curve solutions and Gaia distances. In order to perform more reliable statistical analysis of the results we added to the sample of 12 targets from this paper another 29 totally eclipsing W UMa stars studied by us earlier. As a result we found the following trends: (a) the radius and luminosity of the target components increase with their mass but the dependencies are different from those of main-sequence (MS) stars; (b) the temperatures of stellar components whose masses are above 1 M_{sun}_ tend to be lower than those of the corresponding MS stars, while the temperatures of stellar components whose masses are below 1 M_{sun}_ tend to be higher than those of the corresponding MS stars; (c) there is no relationship between the fillout factor and mass ratio; and (d) 11 of the 41 targets are of A subtype, 24 are of W subtype, and 6 systems are with equal-temperature components.
