AR-2019-2020

of the three modes (constituting the triangular con- figuration of wave vectors) is much smaller than the other two, with which the three-point functions can be completely expressed in terms of the two-point functions. It is found that while the consistency condition is mostly satisfied by the primordial per- turbations generated in the inflationary scenario, it is often violated in the bouncing models. The validity of the consistency condition in the context of inflation can be attributed to the fact that the amplitude of the scalar and tensor perturbations freezes on super-Hubble scales. Whereas, in the bouncing scenarios, the amplitude of the scalar and tensor perturbations often grows rapidly as one ap- proaches the bounce, leading to a violation of the condition. In this work, with the help of a specific example involving the tensor perturbations, we ex- plicitly show that suitable non-minimal couplings can restore the consistency condition even in the bouncing models. We briefly discuss the implica- tions of the result. This work is done in collabora- tion with Debottam Nandi. Parijat Thakur 2016 outburst of H 1743–322: XMM-Newton and NuSTAR View We report the detection of a type C quasi-periodic oscillation (QPO) along with the upper harmonic in the commensurate ratio of 1:2 in the two observa- tions of the low-mass black hole transient H 1743– 322, jointly observed by XMM-Newton and NuS- TAR during the 2016 outburst. We find that the QPO and the upper harmonic exhibit shifts in their centroid frequencies in the second observation with respect to the first one. The hardness intensity dia- gram implies that in contrast to the 2008 and 2014 failed outbursts, the 2016 outburst was a successful one. We also detect the presence of a broad iron K α line at ∼ 6.5 keV and reflection hump in the en- ergy range of 15–30 keV in both of the observations. Along with the shape of the power density spectra, the nature of the characteristic frequencies and the fractional rms amplitude of the timing features im- ply that the source stayed in the low/hard state during these observations. Moreover, the photon index and the other spectral parameters also indi- cate the low/hard state behaviour of the source. Unlike the soft lag detected in this source during the 2008 and 2014 failed outbursts, we observe hard time lags of 0 . 40 ± 0 . 15 s and 0 . 32 ± 0 . 07 s in the 0.07–0.4 Hz frequency range in the two observations during the 2016 outburst. The correlation between the photon index and the centroid frequency of the QPO is consistent with the previous results. Fur- thermore, the high value of the Comptonized frac- tion and the weak thermal component indicate that the QPO is being modulated by the Comptoniza- tion process. This work has been done in collabora- tion with Swadesh Chand, Vivek Kumar Agrawal, Gulab C. Dewangan, and Prakash Tripathi. Probing transit timing variation and its possible origin with twelve new transits of TrES-3b We have investigated the possibility of existence of additional planet, as well as the orbital decay and apsidal precession in the extra-solar planetary system TrES-3 through the transit timing varia- tion (TTV) analysis. We have made total twelve transit observations of this system, which include six transits from the 2m Himalayan Chandra Tele- scope (HCT), IAO, Hanle, India, five from the 1.3m Devasthal Telescope, ARIES, Nainital, India, and one transit from the 1.25m AZT-11 telescope at the Crimean Astrophysical Observatory (CrAO), Crimea. In order to have refine destimation of transit ephemeris, as well as precise TTV anal- ysis, apart from our twelve new transit observa- tions, seventy one more transit data of this sys- tem are also considered from the literature. All these eighty three transit light curves are analyzed with uniform procedure through Transit Analysis Package (TAP). By fitting a linear ephemeris model to the eighty three mid-transit times derived from light curve analysis, we have derived new linear ephemeris for orbital period and mid-transit time with χ 2 red = 1 . 859, which indicates that there is an evidence of TTV in TrES-3 system. However, we do not find any indication of periodic-TTV as the sig- nificance of the highest peak found in the generated Lomb-Scargle periodogram, which is computed us- ing the timing residuals of linear ephemeris model fit is found to be very far below from the thresh- old value (FAP = 5%). This allows us to conclude that there is no evidence of additional planet in the TrES-3 system. Since TrES-3b is one of the known hot-Jupiter extra-solar planets, it has been theoretically predicted that the possible TTV may be due to the orbital decay and apsidal preces- sion induced by tidal interactions of TrES-3b and its parent star. These two phenomena have been examined in the TrES-3 system by fitting the or-