Ultralight vector dark matter search using data from the KAGRA O3GK run

Among the various candidates for dark matter (DM), ultralight vector DM can be probed by laser interferometric gravitational wave detectors through the measurement of oscillating length changes in the arm cavities. In this context, KAGRA has a unique feature due to differing compositions of its mirrors, enhancing the signal of vector DM in the length change in the auxiliary channels. Here we present the result of a search for U(1)B−L gauge boson DM using the KAGRA data from auxiliary length channels during the first joint observation run together with GEO600. By applying our search pipeline, which takes into account the stochastic nature of ultralight DM, upper bounds on the coupling strength between the U(1)B−L gauge boson and ordinary matter are obtained for a range of DM masses. While our constraints are less stringent than those derived from previous experiments, this study demonstrates the applicability of our method to the lower-mass vector DM search, which is made difficult in this measurement by the short observation time compared to the auto-correlation time scale of DM

Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network

Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects

Search for eccentric black hole coalescences during the third observing run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass M>70 M⊙) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities 0<e≤0.3 at 0.33 Gpc−3 yr−1 at 90\% confidence level

∼1.6 Ga ultrahigh-temperature granulite metamorphism in the Central Indian Tectonic Zone: insights from metamorphic reaction history, geothermobarometry and monazite chemical ages

In this study, we present precise pressure–temperature (P–T) and age constraints of Ultrahigh-temperature (UHT) metamorphism of the Bhandara–Balaghat Granulite (BBG) domain at the southern margin of the Central Indian Tectonic Zone (CITZ). Supracrustal and metaigneous granulites of this domain, which lie as detached pods and lenses of various sizes within felsic gneiss–migmatite association record protracted high-T crustal anatexis events, broadly synchronous with and/or punctuated with felsic and mafic plutonism. Magnesian metagreywacke protolith of the supracrustal suite records extensive biotite melting and subsequent melt extractions at deep crustal, UHT metamorphic conditions (T ≥ ∼900°C at P∼8 kbar), producing restitic mineral assemblages of garnet + rutile, garnet + cordierite and garnet + aluminous orthopyroxene. The diversity of the mineral assemblages is related to the domainal-scale variation of the bulk rock composition. In situ chemical age dating of five monazite grains, which occur in the different textural settings of the garnet + cordierite + orthopyroxene + rutile-bearing granulite reveals two age domains: (1) Pervasive ∼ 1.6 Ga domain, which is recorded in monazites occurring as inclusions in garnet and in the leucosome matrix is correlated with the timing of the UHT metamorphism. (2) ∼1.47 Ga domain reflects a fluid-mediated recrystallization event leading to dissolution and re-precipitation of older monazite. The ∼1.6 Ga monazite chemical ages provide robust constraints on the timing of the earliest stage of tectonothermal processes in the CITZ (defined here as the ‘Central Indian Orogeny’). The significance of the ∼1.6 Ga hot orogenesis in interorogen correlation is discussed

Burial of thermally perturbed Lesser Himalayan mid-crust: Evidence from petrochemistry and P–T estimation of the western Arunachal Himalaya, India

In this work, we establish a dual prograde P–T path of the Lesser Himalayan Sequence (LHS) rocks from the Western Arunachal Himalaya (WAH). The investigated metagranites, garnet- and kyanite-zone metapelites of the LHS are part of an Inverted Metamorphic Sequence (IMS) that is exposed on the footwall side of the Main Central Thrust (MCT). Integrated petrographic, mineral chemistry, geothermobarometric (conventional and isopleth intersection methods) and P–T pseudosection modeling studies reveal a near isobaric (at P ∼ 8–9 kbar) peak Barrovian metamorphism with increase in TMax from ∼ 560°C in the metagranite through ∼ 590–600 °C in the lower and middle garnet-zone to ∼ 600–630 °C in the upper garnet- and kyanite-zone rocks. The metamorphic sequence of the LHS additionally records a pre-Barrovian near isobaric thermal gradient in the mid crust (at ∼ 6 kbar) from ∼ 515°C (in the middle garnet zone) to ∼ 560–580 °C (in the upper garnet- and kyanite zone, adjoining the Main Central Thrust). Further burial (along steep dP/dT gradient) to a uniform depth corresponding to ∼ 8–9 kbar and prograde heating of the differentially heated LHS rocks led to the formation of near isobaric metamorphic field gradient in the Barrovian metamorphic zones of the WAH. A combined critical taper and channel flow model is presented to explain the inverted metamorphic zonation of the rocks of the WAH

The Himalayan cryosphere: A critical assessment and evaluation of glacial melt fraction in the Bhagirathi basin

The cryosphere constitutes an important subset of the hydrosphere. The Himalayan cryosphere is a significant contributor to the hydrological budget of a large river system such as the Ganges. Basic data on the cryosphere in the Himalaya is inadequate and also has large uncertainties. The data on glacial melt component in the Himalayan rivers of India also shows high variability. The Gangotri glacier which constitutes nearly a fifth of the glacierized area of the Bhagirathi basin represents one of the fastest receding, large valley glaciers in the region which has been surveyed and monitored for over sixty years. The availability of measurement over a long period and relatively small glacier-fed basin for the Bhagirathi river provides suitable constraints for the measurement of the glacial melt fraction in a Himalayan river. Pre- and post-monsoon samples reveal a decreasing trend of depletion of δ18O in the river water from glacier snout (Gaumukh) to the confluence of the Bhagirathi river with the Alaknanda river near Devprayag. Calculations of existing glacial melt fraction (∼30% at Rishikesh) are not consistent with the reported glacial thinning rates. It is contended that the choice of unsuitable end-members in the three component mixing model causes the overestimation of glacial melt component in the river discharge. Careful selection of end members provides results (∼11% at Devprayag) that are consistent with the expected thinning rates

Polar Studies - Window to the changing Earth

The polar regions are a critical component of the global climate system, with changes taking place at high latitudes having global implications. Anthropogenic activity is affecting both the Arctic and Antarctic, but the two polar regions are responding in very different ways, which complicated the separation of the anthropogenic signal from natural variability. The contributed articles in this issue describe polar scientific studies from various national and international research organizations. The studies are largely confined to understanding the ocean-atmospheric sciences, paleoclimatic conditions and biogeochemical processes in the polar and surrounding ocean realms. This special issue on “Polar Studies - Window to the changing Earth” presents high-quality and topical scientific research concerned with both polar regions. It is an initiative to commemorate the four decades of India's activities in polar research and its international scientific collaborations. In addition, it coincides with the completion of 75 years of India's Independence being celebrated as “Azadi Ka Amrit Mahotsav (Elixir of Freedom Festival)” and the holding of the first SCAR Open Science Conference in India, August 2022

Determinants of Herpetofaunal Diversity in a Threatened Wetland Ecosystem: A Case Study of the Ramaroshan Wetland Complex, Western Nepal

Wetlands are among the highly threatened ecosystems due to anthropogenic activities. The Ramaroshan Wetland Complex (RWC) of Achham District, Nepal is one of the high-altitude wetlands facing human induced degradation and loss. Herpetofauna are key bio-indicators of environmental health and habitat quality and are useful to assess habitat conditions of such threatened ecosystems. This study quantified the land use and land cover (LULC) change in the RWC and documented the diversity and distribution pattern of herpetofauna. The LULC in the area (13.94 Km2) was analyzed for 1989, 2000, 2010 and 2021 by supervised classification of remote sensing images. Surveys were conducted along 25 transects, each of 200 m in length and environmental variables were recorded for every observation of herpetofauna. The LULC analysis revealed an overall loss of 16% of the total water body between 1989 (0.25 Km2) and 2021 (0.21 Km2). Eleven species of herpetofauna (five amphibians and six reptiles) within five families and two orders (i.e., Anura and Squamata), were recorded with low diversity (H’ = 1.88312) and evenness (E = 0.3642) indices. The herpetofauna had a hump-shaped distribution along the elevation gradient with the highest richness and abundance at 2300 m asl. Amphibian abundance decreased with increasing distance to nearest water sources, whereas reptile abundance increased. Amphibians were more abundant in agricultural field and marsh land, whereas reptile abundance was higher around human settlements. Results indicate that the wetland area in the RWC is declining at an alarming rate and, in turn, might account for the low diversity and abundance of the herpetofauna