We report a dynamically evolving low ionization broad absorption line flow in the QSO SDSS J133356.02+001229.1 (at z em ∼ 0.9197). These observations are part of our ongoing monitoring of low ionization broad absorption line (BAL) QSOs with the 2m telescope at IUCAA Girawali observatory (IGO). The broad Mg ii absorption with an ejection velocity of 1.7×10 4 km s −1 , found in the Sloan Digital Sky Survey (SDSS) spectra, has disappeared completely in our IGO spectra. We found an emerging new component at an ejection velocity of 2.8×10 4 km s −1 . During our monitoring period this component has shown strong evolution both in its velocity width and optical depth and nearly disappeared in our latest observations. Acceleration of a low velocity component seen in SDSS spectrum to a higher velocity is unlikely as the Mg ii column densities are always observed to be higher for the new component. We argue that the observed variations may not be related to ionization changes and are consistent with absorption produced by multi-streaming flow transiting across our line of sight. We find a possible connection between flux variation of the QSO and N(Mg ii) of the newly emerged component. This could mean the ejection being triggered by changes in the accretion disk or dust reddening due to the outflowing gas.

We study the time variability of five Fe low‐ionization broad absorption line (FeLoBAL) QSOs using repeated spectroscopic observations with the 2‐m telescope at IUCAA Girawali Observatory (IGO) spanning an interval of up to 10 years. We report a dramatic variation in the Al iii and Fe iii fine‐structure lines in the spectra of SDSS J221511.93−004549.9 (zem∼ 1.478). However, there is no such strong variability shown by the C iv absorption. This source is known to be unusual with (i) the continuum emission dominated by Fe emission lines, (ii) Fe iii absorption being stronger than Fe ii and (iii) the apparent ratio of Fe iii UV 48 to Fe iii UV 34 absorption suggesting an inverted population ratio. This is the first reported detection of time variability in the Fe iii fine‐structure lines in QSO spectra. There is a strong reduction in the absorption strength of these lines between 2000 and 2008. Using the template‐fitting techniques, we show that the apparent inversion of the strength of ultraviolet lines could be related to the complex spectral energy distribution of this QSO. The observed variability can be related to a change in the ionization state of the gas or due to the transverse motion of this absorbing gas. The shortest variability time‐scale of Al iii line gives a lower limit on the electron density of the absorbing gas as  cm−3. The remaining four FeLoBALs do not show any changes beyond the measurement uncertainties either in optical depth or in the velocity structure. We present the long‐term photometric light curve for all of our sources. Among them only SDSS J221511.93−004549.9 shows significant (≥0.2 mag) variability.

In this paper we study the thermodynamics and state space geometry of regular black hole solutions such as Bardeen black hole[1], Ayón-Beato and García black hole[2], Hayward black hole[3] and Berej-Matyjasek-Trynieki-Wornowicz black hole [4]. We find that all these black holes show second order thermodynamic phase transitions(SOTPT) by observing discontinuities in heat capacity-entropy graphs as well as the cusp type double point in free energy-temperature graph. Using the formulation of geometrothermodynamics we again find the singularities in the heat capacity of the black holes by calculating the curvature scalar of the Legendre invariant metric.

Abstract. We evaluate the complex frequencies of the normal modes for the massive charged scalar field perturbations around a Reissner-Nördstrom black hole surrounded by a static and spherically symmetric quintessence using third order WKB approximation approach. Due to the presence of quintessence, quasinormal frequencies damp more slowly. We studied the variation of quasinormal frequencies with charge of the black bole, mass and charge of perturbating scalar field and the quintessential state parameter.

We investigate black holes in a class of dRGT massive gravity for their quasi normal modes (QNMs) for neutral and charged ones using Improved Asymptotic Iteration Method (Improved AIM) and their thermodynamic behavior. The QNMs are studied for different values of the massive parameter m g for both neutral and charged dRGT black holes under a massless scalar perturbation. As m g increases, the magnitude of the quasi normal frequencies are found to be increasing. The results are also compared with the Schwarzchild de Sitter (SdS) case. P-V criticallity of the aforesaid black hoels under massles scalar perturbation in the de Sitter space are also studied in this paper. It is found that the thermodynamic behavior of a neutral black hole shows no physically feasible phase transition while a charged black hole shows a definite phase transition.