http://localhost:8080/xmlui/handle/123456789/172 2026-04-08T12:25:44Z 2026-04-08T12:25:44Z Kumar, Parveen Gopal-Krishna Chand, H. http://localhost:8080/xmlui/handle/123456789/1086 2015-06-04T10:17:52Z 2015-04-01T00:00:00Z

Intranight optical variability of radio-quiet weak emission line quasars – III Kumar, Parveen; Gopal-Krishna; Chand, H. This is continuation of our programme to search for the elusive radio-quiet BL Lacs, by carrying out a systematic search for intranight optical variability (INOV) in a subset of ‘weak emission line quasars’ which are already designated as ‘high-confidence BL Lac candidate’ and are also known to be radio quiet. For six such radio-quiet weak emission line quasars (RQWLQs), we present here new INOV observations taken in 11 sessions of duration >3 h each. Combining these data with our previously published INOV monitoring of RQWLQs in 19 sessions yields INOV observations for a set of 15 RQWLQs monitored in 30 sessions, each lasting more than 3 h. The 30 differential light curves, thus obtained for the 15 RQWLQs, were subjected to a statistical analysis using the F-test, and the deduced INOV characteristics of the RQWLQs then compared with those published recently for several prominent active galactic nucleus (AGN) classes, also applying the F-test. From our existing INOV observations, there is a hint that RQWLQs in our sample show a significantly higher INOV duty cycle than radio- quiet quasars and radio lobe-dominated quasars. Two sessions when we have detected strong (blazar-like) INOV for RQWLQs are pointed out, and these two RQWLQs are therefore the best known candidates for radio-quiet BL Lacs, deserving to be pursued. For a proper comparison with the INOV properties already established for (brighter) members of several prominent classes of AGN, a factor of 2–3 improvement in the INOV detection threshold for the RQWLQs is needed and it would be very interesting to check if that would yield a significantly higher estimate for INOV duty cycle than is found here.

2015-04-01T00:00:00Z Wang, P. F. et al. Pandey, A. K. http://localhost:8080/xmlui/handle/123456789/981 2015-04-23T08:58:30Z 2014-03-04T00:00:00Z

Characterization of the praesepe star cluster by photometry and proper motions with 2 mass, ppmxl and pan-starrs Wang, P. F. et al.; Pandey, A. K. Membership identification is the first step in determining the properties of a star cluster. Low-mass members in particular could be used to trace the dynamical history, such as mass segregation, stellar evaporation, or tidal stripping, of a star cluster in its Galactic environment. We identified member candidates of the intermediate-age Praesepe cluster (M44) with stellar masses ∼0.11–2.4 Mꙩ , using Panoramic Survey Telescope And Rapid Response System and Two Micron All Sky Survey photometry, and PPMXL proper motions. Within a sky area of 3° radius, 1040 candidates are identified, of which 96 are new inclusions. Using the same set of selection criteria on field stars, an estimated false positive rate of 16% was determined, suggesting that 872 of the candidates are true members. This most complete and reliable membership list allows us to favor the BT-Settl model over other stellar models. The cluster shows a distinct binary track above the main sequence, with a binary frequency of 20%–40%, and a high occurrence rate of similar mass pairs. The mass function is consistent with that of the disk population but shows a deficit of members below 0.3 solar masses. A clear mass segregation is evidenced, with the lowest-mass members in our sample being evaporated from this disintegrating cluster.

2014-03-04T00:00:00Z ARIES, Nainital http://localhost:8080/xmlui/handle/123456789/938 2021-03-02T08:47:35Z 2013-08-23T00:00:00Z

सूर्य से उठ रहा सौर तूफान ARIES, Nainital

2013-08-23T00:00:00Z ARIES, Nainital http://localhost:8080/xmlui/handle/123456789/937 2021-03-02T08:44:25Z 2013-08-29T00:00:00Z

ब्रहमांड में छिपे रहस्य खोलेगी TMT ARIES, Nainital

2013-08-29T00:00:00Z