SDSS J082625.70+612515.10 (V = 11.4; [Fe/H] = −3.1) and SDSS J134144.60+474128.90 (V = 12.4; [Fe/H] = −3.2) were observed with the SDSS 2.5-m telescope as part of the SDSS-MARVELS spectroscopic presurvey, and were identified as extremely metal-poor (EMP; [Fe/H] < −3.0) stars during high-resolution followup with the Hanle Echelle Spectrograph (HESP) on the 2.3-m Himalayan Chandra Telescope. In this paper, the first science results using HESP, we present a detailed analysis of their chemical abundances. Both stars exhibit under-abundances in their neutron-capture elements, while one of them, SDSS J134144.60+474128.90, is clearly enhanced in carbon. Lithium was also detected in this star at a level of about A(Li) = 1.95. The spectra were obtained over a span of 6-24 months, and indicate that both stars could be members of binary systems. We compare the elemental abundances derived for these two stars along with other carbon-enhanced metal-poor (CEMP) and EMP stars, in order to understand the nature of their parent supernovae. We find that CEMP-no stars and EMP dwarfs exhibit very similar trends in their lithium abundances at various metallicities. We also find indications that CEMP-no stars have larger abundances of Cr and Co at a given metallicity, compared to EMP stars.

Nuclear astrophysics is a field at the intersection of nuclear physics and astrophysics, which seeks to understand the nuclear engines of astronomical objects and the origin of the chemical elements. This white paper summarizes progress and status of the field, the new open questions that have emerged, and the tremendous scientific opportunities that have opened up with major advances in capabilities across an ever growing number of disciplines and subfields that need to be integrated. We take a holistic view of the field discussing the unique challenges and opportunities in nuclear astrophysics in regards to science, diversity, education, and the interdisciplinarity and breadth of the field. Clearly nuclear astrophysics is a dynamic field with a bright future that is entering a new era of discovery opportunities.

We present the first results of eight Globular Clusters (GCs) from the AstroSat/UVIT Legacy Survey program GlobULeS based on the observations carried out in two FUV filters (F148W and F169M). The FUV-optical and FUV-FUV colour-magnitude diagrams (CMDs) of GCs with the proper motion membership were constructed by combining the UVIT data with HST UV Globular Cluster Survey (HUGS) data for inner regions and Gaia Early Data Release (EDR3) for regions outside the HST’s field. We detect sources as faint as F148W ∼ 23.5 mag which are classified based on their locations in CMDs by overlaying stellar evolutionary models. The CMDs of 8 GCs are combined with the previous UVIT studies of 3 GCs to create stacked FUV-optical CMDs to highlight the features/peculiarities found in the different evolutionary sequences. The FUV (F148W) detected stellar populations of 11 GCs comprises 2,816 Horizontal Branch (HB) stars (190 Extreme HB candidates), 46 post-HB (pHB), 221 Blue Straggler Stars (BSS), and 107 White Dwarf (WD) candidates. We note that the blue HB colour extension obtained from F148W−G colour and the number of FUV detected EHB candidates are strongly correlated with the maximum internal Helium (He) variation within each GC, suggesting that FUV-optical plane is the most sensitive to He abundance variations in the HB. We discuss the potential science cases that will be addressed using these catalogues including HB morphologies, BSSs, pHB, and, WD stars.

The stars SDSS J0646+4116 and SDSS J1937+5024 are relatively bright stars that were initially observed as part of the SDSS/MARVELS pre-survey. They were selected, on the basis of their weak CH G-bands, along with a total of 60 others, in the range of halo globular cluster metallicities for high-resolution spectroscopic follow-up as a part of the HESP-GOMPA survey (Hanle Echelle SPectrograph -Galactic survey Of Metal Poor stArs). The stars exhibit typical nucleosynthesis signatures expected from the so-called second-generation stars of globular clusters. The light-element anticorrelation of Mg-Al is detected, along with elevated abundances of Na. Carbon is found to be depleted, which is compatible with expectation. Lithium is also detected in SDSS J0646+4116 and SDSS J1937+5024 ; the measured abundances are similar to those of normal halo giant stars. These bright escapees provide a unique opportunity to study the nucleosynthesis events of globular clusters in great detail, and shed light on their chemical-enrichment histories.

We present a study on the detailed elemental abundances of newly identified, bright, very metal-poor stars with the detection of lithium, initially observed as part of the SDSS/MARVELS pre-survey. These stars were selected for high-resolution spectroscopic follow-up as part of the HESP-GOMPA survey. In this work, we discuss the Li abundances detected for several stars in the survey, which include main-sequence stars, subgiants, and red giants. Different classes of stars are found to exhibit very similar distributions of Li, which points toward a common origin. We derive a scaling relation for the depletion of Li as a function of temperature for giants and main-sequence stars; the majority of the samples from the literature were found to fall within 1σ (0.19 and 0.12 dex K−1 for giants and dwarfs, respectively) of this relationship. We also report the existence of a slope of the Li abundance as a function of distance from the Galactic plane, indicating mixed stellar populations. Most Li-rich stars are found to be in or close to the Galactic plane. Along with Li, we have derived detailed abundances for C, odd-Z, α-, Fe-peak, and neutron-capture elements for each star. We have also used astrometric parameters from Gaia-EDR3 to complement our study, and derived kinematics to differentiate between the motions of the stars—those formed in situ and those accreted. The stellar population of the Spite plateau, including additional stars from the literature, is found to have significant contributions from stars formed in situ and through accretion. The orbits for the program stars have also been derived and studied for a period of 5 Gyr backwards in time.