scholarly journals OJ 287: A Blazar with Everything

1994 ◽  
Vol 159 ◽  
pp. 409-409
Author(s):  
L.O. Takalo
Keyword(s):  
Correlation Analysis ◽  
Light Curve ◽  
Observational Data ◽  
Light Curves ◽  
Simple Correlation ◽  
Data Set ◽  
Preliminary Results ◽  
Blazar Oj 287

We have collected all the observations available to us of blazar OJ 287. Here we will present preliminary results from our investigation of these data. The photometric light curves show large outbursts occuring (quasi)simultaneously in all frequences. The largest outbursts occured during 1972 and 1983. The B-band light curve can be extended to the year 1894. This being the longest available observational data set of all blazars. Polarization light curves in optical show random variations in all timescales. In the radio bands the polarization observations show well defined structure in the light curves. Light curves and simple correlation analysis based on the light curves on different frequences will be presented.

scholarly journals Searching for binary central stars of planetary nebulae with Kepler

2011 ◽  
Vol 7 (S283) ◽  
pp. 344-345
Author(s):  
Dimitri Douchin ◽  
George H. Jacoby ◽  
Orsola De Marco ◽  
Steve B. Howell ◽  
Mattias Kronberger
Keyword(s):  
Initial Data ◽  
Light Curve ◽  
Planetary Nebulae ◽  
Central Star ◽  
Light Curves ◽  
Data Set ◽  
Lunar Cycles ◽  
Near Future ◽  
Central Stars

AbstractThe Kepler Observatory offers unprecedented photometric precision (<1 mmag) and cadence for monitoring the central stars of planetary nebulae, allowing the detection of tiny periodic light curve variations, a possible signature of binarity. With this precision free from the observational gaps dictated by weather and lunar cycles, we are able to detect companions at much larger separations and with much smaller radii than ever before. We have been awarded observing time to obtain light-curves of the central stars of the six confirmed and possible planetary nebulae in the Kepler field, including the newly discovered object Kn 61, at cadences of both 30 min and 1 min. Of these six objects, we could confirm for three a periodic variability consistent with binarity. Two others are variables, but the initial data set presents only weak periodicities. For the central star of Kn 61, Kepler data will be available in the near future.

scholarly journals Analysis of putative exoplanetary signatures found in light curves of two sdBV stars observed by Kepler

2019 ◽  
Vol 627 ◽  
pp. A86 ◽  
Author(s):  
A. Blokesz ◽  
J. Krzesinski ◽  
L. Kedziora-Chudczer
Keyword(s):  
Fourier Transform ◽  
Light Curve ◽  
Fourier Transforms ◽  
Detection Threshold ◽  
Low Frequency ◽  
Light Curves ◽  
Comparison Star ◽  
Data Set ◽  
Nearby Star ◽  
Lower Amplitude

Context. We investigate the validity of the claim that invokes two extreme exoplanetary system candidates around the pulsating B-type subdwarfs KIC 10001893 and KIC 5807616 from the primary Kepler field. Aims. Our goal was to find characteristics and the source of weak signals that are observed in these subdwarf light curves. Methods. To achieve this, we analyzed short- and long-cadence Kepler data of the two stars by means of a Fourier transform and compared the results to Fourier transforms of simulated light curves to which we added exoplanetary signals. The long-cadence data of KIC 10001893 were extracted from CCD images of a nearby star, KIC 10001898, using a point spread function reduction technique. Results. It appears that the amplitudes of the Fourier transform signals that were found in the low-frequency region depend on the methods that are used to extract and prepare Kepler data. We demonstrate that using a comparison star for space telescope data can significantly reduce artifacts. Our simulations also show that a weak signal of constant amplitude and frequency, added to a stellar light curve, conserves its frequency in Fourier transform amplitude spectra to within 0.03 μHz. Conclusions. Based on our simulations, we conclude that the two low-frequency Fourier transform signals found in KIC 5807616 are likely the combined frequencies of the lower amplitude pulsating modes of the star. In the case of KIC 10001893, the signal amplitudes that are visible in the light curve depend on the data set and reduction methods. The strongest signal decreases significantly in amplitude when KIC 10001898 is used as a comparison star. Finally, we recommend that the signal detection threshold is increased to 5σ (or higher) for a Fourier transform analysis of Kepler data in low-frequency regions.

scholarly journals Quasi-periodic behaviour in the optical and γ-ray light curves of blazars 3C 66A and B2 1633+38

2020 ◽  
Vol 492 (4) ◽  
pp. 5524-5539 ◽  
Author(s):  
J Otero-Santos ◽  
J A Acosta-Pulido ◽  
J Becerra González ◽  
C M Raiteri ◽  
V M Larionov ◽  
...  
Keyword(s):  
Light Curve ◽  
Confidence Level ◽  
Light Curves ◽  
Data Set ◽  
Spectrum Radio ◽  
Periodic Behaviour ◽  
Optical Light Curve ◽  
Emission Models ◽  
Γ Ray ◽  
Radio Quasar

ABSTRACT We report on quasi-periodic variability found in two blazars included in the Steward Observatory Blazar Monitoring data sample: the BL Lac object 3C 66A and the Flat Spectrum Radio Quasar B2 1633+38. We collect optical photometric and polarimetric data in V and R bands of these sources from different observatories: St. Petersburg University, Crimean Astrophysical Observatory, WEBT–GASP, Catalina Real-Time Transient Survey, Steward Observatory, STELLA Robotic Observatory, and Katzman Automatic Imaging Telescope. In addition, an analysis of the γ-ray light curves from Fermi–LAT is included. Three methods are used to search for any periodic behaviour in the data: the Z-transform Discrete Correlation Function, the Lomb–Scargle periodogram and the Weighted Wavelet Z-transform. We find pieces of evidence of possible quasi-periodic variability in the optical photometric data of both sources with periods of ∼3 yr for 3C 66A and ∼1.9 yr for B2 1633+38, with significances between 3σ and 5σ. Only B2 1633+38 shows evidence of this behaviour in the optical polarized data set at a confidence level of 2σ–4σ. This is the first reported evidence of quasi-periodic behaviour in the optical light curve of B2 1633+38. Also, a hint of quasi-periodic behaviour is found in the γ-ray light curve of B2 1633+38 with a confidence level ≥2σ, while no periodicity is observed for 3C 66A in this energy range. We propose different jet emission models that could explain the quasi-periodic variability and the differences found between these two sources.

scholarly journals The stellar occultations by the largest satellite of the dwarf planet Haumea, Hi'iaka

2021 ◽  
Author(s):  
Estela Fernández-Valenzuela ◽  
Jose Luis Ortiz ◽  
Bryan Holler ◽  
Monica Vara-Lubiano ◽  
Nicolas Morales ◽  
...  
Keyword(s):  
Light Curve ◽  
North Africa ◽  
High Accuracy ◽  
The Body ◽  
Light Curves ◽  
Effective Diameter ◽  
Preliminary Results ◽  
Stellar Occultations ◽  
The Times ◽  
Triaxial Shape

&lt;p&gt;Two stellar occultations by the largest satellite of the dwarf planet Haumea, Hi'iaka, were predicted to happen on April, 6th and 16th, 2021. Additional high accuracy astrometric analysis was carried out in order to refine the prediction for April 6th, using several telescopes in the 1.2-m to 2-m range, with the final shadow path crossing North Africa. We successfully detected the first event from TRAPPIST-North telescope at Ouka&amp;#239;meden Observatory (Morocco). Although it was recorded from only one site, this first detection allowed us to improve the prediction for the second that crossed North America from East to West.&amp;#160;We had a good success recording six positive detections and several negative detections that constrain the shape and size of the body. The light curves obtained from the different observatories provide the time at which the star disappears and reappears, which are translated into chords (the projected lines on the sky-plane as observed from each location). Additionally, we carried out a campaign to study Hi'iaka's rotational light-curve, studying the residuals of Haumea's rotational light-curve to a four-order Fourier fit. We obtained the rotational phases at the times of the occultations, which is critical for the analysis of the occultations, given that Hi&amp;#8217;iaka is clearly non-spherical. Our preliminary results show that Hi'iaka indeed has a triaxial shape with a larger effective diameter than what has been published so far. The preliminary results and their implications will be discussed in this talk.&amp;#160;&lt;/p&gt;

scholarly journals Variability characteristics of Blazar 0J 287

1996 ◽  
Vol 175 ◽  
pp. 45-46
Author(s):  
L.O. Takalo ◽  
A. Sillanpää ◽  
T. Pursimo ◽  
H.J. Lehto ◽  
K. Nilsson ◽  
...  
Keyword(s):  
Light Curve ◽  
Time Scales ◽  
Light Curves ◽  
Data Archive ◽  
Extragalactic Object ◽  
Optical Light Curve ◽  
Blazar Oj 287

Blazar OJ 287 is one of the best observed extragalactic objects. It's historical light curve goes back to 1890′s. Based on the historical behaviour Sillanpää et al. (1988) showed that OJ 287 displays large periodic outbursts, with a period of 11.7 years. We have monitored OJ 287 intensively for two years, during the OJ-94 project. This project was created for monitoring OJ 287 during its predicted new outburst in 1994. In the data archive we have over 7000 observations on OJ 287, in the radio, infrared and optical bands. This data archive contains the best ever obtained light curves for any extragalactic object. The optical light curve shows continuous variability down to time scales of tens of minutes. The variability observed in OJ 287 can be broken down to (at least) four different categories:

scholarly journals Frequency analysis of multiperiodic δ Scuti stars

1993 ◽  
Vol 139 ◽  
pp. 149-149 ◽  
Author(s):  
L. Mantegazza ◽  
E. Poretti ◽  
F.M. Zerbi
Keyword(s):  
Light Curve ◽  
Frequency Analysis ◽  
Curve Analysis ◽  
Light Curves ◽  
Light Curve Analysis ◽  
Preliminary Results ◽  
Long Time ◽  
Scuti Star ◽  
Scuti Stars ◽  
Δ Scuti Stars

We report some of the recent results of our studies on δ Scuti star pulsation which are based on observations made at Merate and La Silla Observatories, sometimes in two site campaigns. Our recent experiences on X Caeli and 44 Tauri have shown that quite complicate light curves can be resolved even with observations obtained from one site only, if compact and accurate datasets are collected on sufficiently long time baselines (Mantegazza and Poretti, 1992; Poretti et al., 1992). Here we report the preliminary results of the light curve analysis of three more stars surveyed for more than 120 hours each: BI CMi, HD 18878 and HD 224639.BI CMi has been observed in a two-site campaign in January-February 1991, the observations being collected during 17 nights. The frequency analysis of the light curve allowed us to identify unambiguously 4 pulsation modes at 8.247, 8.863, 8.514 and 7.424 c/d with semi-amplitudes of 22, 19, 5 and 5 mmag respectively.

scholarly journals KEPLER PLANETARY SYSTEMS: DOPPLER BEAMING EFFECT SIGNIFICANCE

2021 ◽  
Vol 57 (1) ◽  
pp. 123-132
Author(s):  
H. Barbier ◽  
E. López
Keyword(s):  
Light Curve ◽  
Radial Velocity ◽  
Observational Data ◽  
Close Agreement ◽  
Extrasolar Planets ◽  
Planetary Systems ◽  
Light Curves ◽  
Third Harmonic ◽  
Good Agreement

In the present work, in order to estimate the semi-amplitude of the radial velocity, we evaluate the contribution of the Doppler beaming effect to the phase curves of the all confirmed extrasolar planets (2776, September 2019), observed so far by the Kepler telescope. By modeling the tiny photometric variations (reflection, ellipsoidal and Doppler beaming effects) of the light curves, we found that the best observational data are in close agreement with the theoretical and published values of the amplitudes only for exoplanets: KOI-13b and TrES-2b. The derived values for the radial velocity also are in good agreement with those published by some authors. Furthermore, we found it necessary to introduce a third harmonic (3Φ) contribution into the KOI-13b and HAT-P7b light curve models, in order to decrease the residuals.

scholarly journals Changes in the Soft and Hard X-Ray Light Curves of the AM Her Object E1405−451

1987 ◽  
Vol 93 ◽  
pp. 643-649
Author(s):  
J.P. Osborne ◽  
M. Cropper ◽  
S. Cristiani
Keyword(s):  
Phase Shift ◽  
Light Curve ◽  
Light Curves ◽  
Optical Observations ◽  
X Ray ◽  
Preliminary Results ◽  
Optical Light Curve

AbstractThe preliminary results of EXOSAT and contemporaneous optical observations of E1405−451 (V834 Cen) in 1985 and 1986 are presented. In the latter of the two observations the soft X-ray light curve was observed to be quite different to that seen in all previous observations, but similar to the optical light curve and the new soft X-ray light curve of E2003+225. A phase shift of the broad soft X-ray eclipse was also observed. The hard X-ray and optical light curves have also undergone small changes.

The Eclipsing Binary WX Eridani

1979 ◽  
Vol 46 ◽  
pp. 385
Author(s):  
M.B.K. Sarma ◽  
K.D. Abhankar
Keyword(s):  
Light Curve ◽  
Spectral Type ◽  
Orbital Period ◽  
Primary Component ◽  
Light Curves ◽  
Absorption Feature ◽  
Primary Star ◽  
Eclipsing Binary ◽  
The Times ◽  
Phase Angles

AbstractThe Algol-type eclipsing binary WX Eridani was observed on 21 nights on the 48-inch telescope of the Japal-Rangapur Observatory during 1973-75 in B and V colours. An improved period of P = 0.82327038 days was obtained from the analysis of the times of five primary minima. An absorption feature between phase angles 50-80, 100-130, 230-260 and 280-310 was present in the light curves. The analysis of the light curves indicated the eclipses to be grazing with primary to be transit and secondary, an occultation. Elements derived from the solution of the light curve using Russel-Merrill method are given. From comparison of the fractional radii with Roche lobes, it is concluded that none of the components have filled their respective lobes but the primary star seems to be evolving. The spectral type of the primary component was estimated to be F3 and is found to be pulsating with two periods equal to one-fifth and one-sixth of the orbital period.

Sign in / Sign up

Export Citation Format

Share Document