20 research outputs found
Galactic Model Parameters and Space Density of Cataclysmic Variables in Gaia Era: New Constraints to Population Models
The spatial distribution, Galactic model parameters and luminosity function
of cataclysmic variables (CVs) are established using re-estimated trigonometric
parallaxes of {\it Gaia} DR3. The data sample of 1,587 CVs in this study is
claimed to be suitable for Galactic model parameter estimation as the distances
are based on trigonometric parallaxes and the {\it Gaia} DR3 photometric
completeness limits were taken into account when the sample was created.
According to the analysis, the scale height of All CVs increases from 2482
to 4304 pc towards shorter periods near the lower limit of the period gap
and suddenly drops to 3002 pc for the shortest orbital period CVs. The
exponential scale heights of All CVs and magnetic systems are found to be
3752 and 2813 pc, respectively, considerably larger than those
suggested in previous observational studies. The local space density of All CVs
and magnetic systems in the sample are 10 and
pc, respectively. Our measurements
strengthen the 1-2 order of magnitude discrepancy between CV space densities
predicted by population synthesis models and observations. It is likely that
this discrepancy is due to objects undetected by CV surveys, such as the
systems with very low and the ones in the period gap. The comparisons
of the luminosity function of white dwarfs with the luminosity function of All
CVs in this study show that 500 times the luminosity function of CVs fits very
well to the luminosity function of white dwarfs. We conclude that the
estimations and data sample in this study can be confidently used in further
analysis of CVs.Comment: 23 pages, including 12 figures and 6 tables, accepted for publication
in the Astronomical Journa
Multi-wavelength temporal and spectral analysis of Blazar S5 1803+78
Blazars are a class of AGN, one of their jets is pointed towards the earth.
Here, we report about the multi-wavelength study for blazar S5 1803+78 between
MJD 58727 to MJD 59419. We analysed -ray data collected by Fermi-LAT,
X-ray data collected by Swift-XRT \& NuSTAR, optical photons detected by
Swift-UVOT \& TUBITAK observatory in Turkey. Three flaring states are
identified by analysing the -ray light curve. A day scale variability
is observed throughout the flares with the similar rise and decay times
suggesting a compact emission region located close to the central engine.
Cross-correlation studies are carried out between -ray, radio, and
X-ray bands, and no significant correlation is detected. The -ray and
optical emission are significantly correlated with zero time lag suggesting a
co-spatial origin of them. A significant positive correlation between the R-I
index and the V magnitude is observed. The broadband spectral energy
distributions (SEDs) modeling was performed for all the flaring episodes as
well as for one quiescent state for comparison. SEDs are best fitted with the
synchrotron-self Compton (SSC) model under a one-zone leptonic scenario. The
SED modeling shows that to explain the high flaring state strong Doppler
boosting is required.Comment: 13 pages, 14 figures, 4 tables, Accepted in MNRA
Characterizing the optical nature of the blazar S5 1803+784 during its 2020 flare
We report the results from our study of the blazar S5 1803+784 carried out
using the quasi-simultaneous , , , and observations from May 2020
to July 2021 on 122 nights. Our observing campaign detected the historically
bright optical flare during MJD 59063.5MJD 59120.5. We also found the source
in its brightest (= 13.617) and faintest (= 15.888) states
till date. On 13 nights, covering both flaring and non-flaring periods, we
searched for the intraday variability using the power-enhanced test and the
nested ANOVA test. We found significant variability in 2 out of these 13
nights. However, no such variability was detected during the flaring period.
From the correlation analysis, we observed that the emission in all optical
bands were strongly correlated with a time lag of 0 days. To get
insights into its dominant emission mechanisms, we generated the optical
spectral energy distributions of the source on 79 nights and estimated the
spectral indices by fitting the simple power law. Spectral index varied from
1.392 to 1.911 and showed significant variations with time and band
magnitude. We have detected a mild bluer-when-brighter trend (BWB) during the
whole monitoring period while a much stronger BWB trend during the flare. We
also carried out a periodicity search using four different methods and found no
significant periodicity during our observation duration. Based on the analysis
during the flaring state of the source one can say that the emissions most
likely originate from the jet rather than the accretion disk.Comment: 17 pages, 8 figures, 7 tables, accepted for publication in The
Astrophysical Journal (ApJ
Multi-band behaviour of the TeV blazar PG 1553+113 in optical range on diverse timescales. Flux and spectral variations
Context. The TeV BL Lac object PG1553+113 is one of the primary candidates for a binary supermassive black hole system.Aims. We study the flux and spectral variability of PG1553+113 on intra-night to long-term timescales using (i) BVRI data collected over 76 nights from January 2016 to August 2019 involving nine optical telescopes and (ii) historical VR data (including ours) obtained for the period from 2005 to 2019.Methods. We analysed the light curves using various statistical tests, fitting and cross-correlation techniques, and methods for the search for periodicity. We examined the colour-magnitude diagrams before and after the corresponding light curves were corrected for the long-term variations.Results. Our intra-night monitoring, supplemented with literature data, result in a low duty cycle of âŒ(10?18)%. In April 2019, we recorded a flare, which marks the brightest state of PG1553+113 for the period from 2005 to 2019: R â 13.2mag. This flare is found to show a clockwise spectral hysteresis loop on its VR colour-magnitude diagram and a time lag in the sense that the V-band variations lead the R-band ones.We obtain estimates of the radius, the magnetic field strength, and the electron energy that characterize the emission region related to the flare.We find a median period of (2.21±0.04) years using the historical light curves. In addition, we detect a secondary period of about 210 days using the historical light curves corrected for the long-term variations. We briefly discuss the possible origin of this period.Fil: Agarwal, A.. Indian Institute Of Astrophysics; India. Raman Research Institute; IndiaFil: Mihov, B.. Institute Of Astronomy And Nao; BulgariaFil: Andruchow, Ileana. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de AstrofĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas. Instituto de AstrofĂsica La Plata; ArgentinaFil: Cellone, Sergio Aldo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - San Juan. Complejo AstronĂłmico "El Leoncito". Universidad Nacional de CĂłrdoba. Complejo AstronĂłmico "El Leoncito". Universidad Nacional de la Plata. Complejo AstronĂłmico "El Leoncito". Universidad Nacional de San Juan. Complejo AstronĂłmico "El Leoncito"; ArgentinaFil: Anupama, G. C.. Indian Institute Of Astrophysics; IndiaFil: Agrawal, V.. Embibe; IndiaFil: Zola, S.. Jagiellonian University; PoloniaFil: Slavcheva Mihova, L.. Institute Of Astronomy And Nao; BulgariaFil: Ăzdönmez, A.. Ataturk University; TurquĂaFil: Ege, E.. Istanbul University; TurquĂaFil: Raj, A.. University Enclave; IndiaFil: Mammana, Luis Antonio. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - San Juan. Complejo AstronĂłmico "El Leoncito". Universidad Nacional de CĂłrdoba. Complejo AstronĂłmico "El Leoncito". Universidad Nacional de la Plata. Complejo AstronĂłmico "El Leoncito". Universidad Nacional de San Juan. Complejo AstronĂłmico "El Leoncito"; ArgentinaFil: Zibecchi, Lorena Cecilia. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de AstrofĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas. Instituto de AstrofĂsica La Plata; ArgentinaFil: Fernandez Lajus, Eduardo Eusebio. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de AstrofĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas. Instituto de AstrofĂsica La Plata; Argentin
Multi-band behaviour of the TeV blazar PG 1553+113 in optical range on diverse timescales. Flux and spectral variations
Context. The TeV BL Lac object PG1553+113 is one of the primary candidates for a binary supermassive black hole system.Aims. We study the flux and spectral variability of PG1553+113 on intra-night to long-term timescales using (i) BVRI data collected over 76 nights from January 2016 to August 2019 involving nine optical telescopes and (ii) historical VR data (including ours) obtained for the period from 2005 to 2019.Methods. We analysed the light curves using various statistical tests, fitting and cross-correlation techniques, and methods for the search for periodicity. We examined the colour-magnitude diagrams before and after the corresponding light curves were corrected for the long-term variations.Results. Our intra-night monitoring, supplemented with literature data, result in a low duty cycle of âŒ(10?18)%. In April 2019, we recorded a flare, which marks the brightest state of PG1553+113 for the period from 2005 to 2019: R â 13.2mag. This flare is found to show a clockwise spectral hysteresis loop on its VR colour-magnitude diagram and a time lag in the sense that the V-band variations lead the R-band ones.We obtain estimates of the radius, the magnetic field strength, and the electron energy that characterize the emission region related to the flare.We find a median period of (2.21±0.04) years using the historical light curves. In addition, we detect a secondary period of about 210 days using the historical light curves corrected for the long-term variations. We briefly discuss the possible origin of this period.Fil: Agarwal, A.. Indian Institute Of Astrophysics; India. Raman Research Institute; IndiaFil: Mihov, B.. Institute Of Astronomy And Nao; BulgariaFil: Andruchow, Ileana. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de AstrofĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas. Instituto de AstrofĂsica La Plata; ArgentinaFil: Cellone, Sergio Aldo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - San Juan. Complejo AstronĂłmico "El Leoncito". Universidad Nacional de CĂłrdoba. Complejo AstronĂłmico "El Leoncito". Universidad Nacional de la Plata. Complejo AstronĂłmico "El Leoncito". Universidad Nacional de San Juan. Complejo AstronĂłmico "El Leoncito"; ArgentinaFil: Anupama, G. C.. Indian Institute Of Astrophysics; IndiaFil: Agrawal, V.. Embibe; IndiaFil: Zola, S.. Jagiellonian University; PoloniaFil: Slavcheva Mihova, L.. Institute Of Astronomy And Nao; BulgariaFil: Ăzdönmez, A.. Ataturk University; TurquĂaFil: Ege, E.. Istanbul University; TurquĂaFil: Raj, A.. University Enclave; IndiaFil: Mammana, Luis Antonio. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - San Juan. Complejo AstronĂłmico "El Leoncito". Universidad Nacional de CĂłrdoba. Complejo AstronĂłmico "El Leoncito". Universidad Nacional de la Plata. Complejo AstronĂłmico "El Leoncito". Universidad Nacional de San Juan. Complejo AstronĂłmico "El Leoncito"; ArgentinaFil: Zibecchi, Lorena Cecilia. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de AstrofĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas. Instituto de AstrofĂsica La Plata; ArgentinaFil: Fernandez Lajus, Eduardo Eusebio. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de AstrofĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas. Instituto de AstrofĂsica La Plata; Argentin
Optical identification and follow-up observations of SRGA J213151.5+491400 -- a new magnetic cataclysmic variable discovered with SRG Observatory
We report results of optical identification and multi-wavelength study of a
new polar-type magnetic cataclysmic variable (MCV), SRGA J213151.5+491400,
discovered by Spectrum Roentgen-Gamma () observatory in the course of the
all-sky survey. We present optical data from telescopes in Turkey (RTT-150 and
T100 at the T\"UBITAK National Observatory), and in Russia (6-m and 1-m at SAO
RAS), together with the X-ray data obtained with and
telescopes aboard and the observatory. We detect SRGA
J213151.5+491400 in a high state in 2020 (17.9 mag) that decreases about 3 mag
into a low state (21 mag) in 2021. We find only one significant period using
optical photometric time series analysis which reveals the white dwarf
spin/orbital period to be 0.059710(1) days (85.982 min). The long slit
spectroscopy in the high state yields a power law continuum increasing towards
the blue with a prominent He II line along with the Balmer line emissions with
no cyclotron humps; consistent with MCV nature. Doppler Tomography confirms the
polar nature revealing ballistic stream accretion along with magnetic stream
during the high state. These characteristics show that the new source is a
polar-type MCV. detections yield an X-ray flux of
(4.0-7.0)10 erg cm s in the high state.
detects a dominating hot plasma component (kT 21 keV in the
high state) declining to (4.0-6.0)10 erg cm s in
2021 (low state). The data obtained in the low state reveal a two-pole
accretor showing a soft X-ray component at (6-7) significance with a
blackbody temperature of 15-18 eV. A soft X-ray component has never been
detected for a polar in the low state before.Comment: 16 pages, 4 Tables and 15 Figures. Accepted for publication in A&A as
it stand
Galactic model parameters of cataclysmic variables: Results from a new absolute magnitude calibration with 2MASS and WISE
In order to determine the spatial distribution, Galactic model parameters and luminosity function of cataclysmic variables (CVs), a J-band magnitude limited sample of 263 CVs has been established using a newly constructed period-luminosity-colours (PLCs) relation which includes J, K-s and W1-band magnitudes in 2MASS and WISE photometries, and the orbital periods of the systems. This CV sample is assumed to be homogeneous regarding to distances as the new PLCs relation is calibrated with new or re-measured trigonometric parallaxes. Our analysis shows that the scaleheight of CVs is increasing towards shorter periods, although selection effects for the periods shorter than 2.25 h dramatically decrease the scaleheight: the scaleheight of the systems increases from 192 pc to 326 pc as the orbital period decreases from 12 to 2.25 h. The z-distribution of all CVs in the sample is well fitted by an exponential function with a scaleheight of 213(-10)(+11) pc. However, we suggest that the scaleheight of CVs in the Solar vicinity should be similar to 300 pc and that the scaleheights derived using the sech(2) function should be also considered in the population synthesis models. The space density of CVs in the Solar vicinity is found 5.58(1.35) x 10(-6) pc(-3) which is in the range of previously derived space densities and not in agreement with the predictions of the population models. The analysis based on the comparisons of the luminosity function of white dwarfs with the luminosity function of CVs in this study show that the best fits are obtained by dividing the luminosity functions of white dwarfs by a factor of 350-450. (C) 2014 Elsevier B.V. All rights reserved
Probing transit timing variations of three hot Jupiters: HATP-36b, HATP-56b, and WASP-52b
We report the results of new transit observations for the three hot Jupiter-like planets, HATP-36b, HATP-56b, and WASP-52b, respectively. Transit timing variations (TTVs) are presented for these systems based on observations that span the period 2016-2020. The data were collected with the 0.6-m telescope at Adiyaman University (ADYU60, Turkey) and the 1.0 m telescope at TĂBCrossed D signTAK National Observatory (TUG, Turkey). Global fits were performed to the combined light curves for each system along with the corresponding radial velocity (RV) data taken from the literature. The extracted parameters (for all three systems) are found to be consistent with the values from previous studies. Through fits to the combined mid-Transit times data from our observations and the data available in the literature, an updated linear ephemeris is obtained for each system. Although a number of potential outliers are noted in the respective O-C diagrams, the majority of the data are consistent within the 3Ï confidence level implying a lack of convincing evidence for the existence of additional objects in the systems studied
Analysis of the Intranight Variability of BL Lacertae during Its 2020 August Flare
We present an analysis of the BVRI photometry of the blazar BL Lacertae on diverse timescales from 2020 mid-July to mid-September. We have used 11 different optical telescopes around the world and have collected data over 84 observational nights. The observations cover the onset of a new activity phase of BL Lacertae that started in 2020 August (termed as the 2020 August flare by us), and the analysis is focused on the intranight variability. On short-term timescales, (i) flux varied with âŒ2.2 mag in the R band, (ii) the spectral index was found to be weakly dependent on the flux (i.e., the variations could be considered mildly chromatic), and (iii) no periodicity was detected. On intranight timescales, BL Lacertae was found to predominantly show bluer-when-brighter chromatism. We also found two cases of significant interband time lags of the order of a few minutes. The duty cycle of the blazar during the 2020 August flare was estimated to be quite high (âŒ90% or higher). We decomposed the intranight light curves into individual flares and determined their characteristics. On the basis of our analysis and assuming the turbulent jet model, we determined some characteristics of the emitting regions: Doppler factor, magnetic field strength, electron Lorentz factor, and radius. The radii determined were discussed in the framework of the Kolmogorov theory of turbulence. We also estimated the weighted mean structure function slope on intranight timescales, related it to the slope of the power spectral density, and discussed it with regard to the origin of intranight variability