Search Publications
New insights on the massive interacting binary UU Cassiopeiae
Hadrava, P.; Jurkovic, M. I.; Mennickent, R. E. +7 more
We present the results of our study of the close binary UU Cassiopeiae based on previously published multiwavelength photometric and spectroscopic data. Based on eclipse timings from the last 117 years, we find an improved orbital period of Po = 8.d519296(8). In addition, we find a long cycle of length T ∼ 270 d in…
Sequential Lid Removal in a Triple-decker Chain of CME-producing Solar Eruptions
Joshi, Bhuwan; Joshi, Navin Chandra; Moore, Ronald L. +1 more
We investigate the onsets of three consecutive coronal mass ejection (CME) eruptions in 12 hr from a large bipolar active region (AR) observed by the Solar Dynamics Observatory (SDO), the Solar Terrestrial Relations Observatory (STEREO), the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), and the Geostationary Operational Environmen…
Structural analysis of disc super star clusters of M82: size and profile shape at intermediate ages
Mayya, Y. D.; Rosa-González, D.; Puerari, I. +1 more
We present the structural parameters of 99 super star clusters (SSCs) in the disc of M82. Moffat-EFF, King, and Wilson models were fitted using a χ2-minimization method to background-subtracted surface brightness profiles in the F435W (B), F555W (V), and F814W (I) bands of the Advanced Camera for Surveys (ACS) of the Hubble Space Telesc…
Detecting neutral hydrogen at z ≳ 3 in large spectroscopic surveys of quasars
Fumagalli, Michele; Fotopoulou, Sotiria; Thomson, Laura
We present a pipeline based on a random forest classifier for the identification of high column density clouds of neutral hydrogen (i.e. the Lyman limit systems, LLSs) in absorption within large spectroscopic surveys of z ≳ 3 quasars. We test the performance of this method on mock quasar spectra that reproduce the expected data quality of the Dark…
Morphology and ionization characteristics of planetary nebulae PB 1 and PC 19
Mondal, Soumen; Das, Ramkrishna; Bandyopadhyay, Rahul +1 more
We present results of our study of two planetary nebulae (PNe), PB1 and PC 19. We use the optical spectra of these two PNe observed at 2 m Himalayan Chandra Telescope and also archival and literature data for the study. We use the morphokinematic code shape to construct 3D morphologies of the PNe and the photoionization code cloudy to model the ob…
Low-Frequency Radio Observations of the "Quiet" Corona During the Descending Phase of Sunspot Cycle 24
Ramesh, R.; Kumari, A.; Kathiravan, C. +3 more
We carried out a statistical study of the "quiet" solar corona during the descending phase of the Sunspot Cycle 24 (i.e., January 2015 to May 2019) using data obtained with the Gauribidanur RAdioheliograPH (GRAPH) at 53 and 80 MHz simultaneously. Our results show that the equatorial (east-west) diameters of the solar corona at the above two freque…
Obscuration properties of mid-IR-selected AGN
Georgantopoulos, I.; Mountrichas, G.; Ruiz, A. +1 more
The goal of this work is to study the obscuration properties of mid-infrared (mid-IR)-selected active galactic nuclei (AGN). For that purpose, we use Wide-field Infrared Survey Explorer (WISE) sources in the Stripe 82-XMM area to identify mid-IR AGN candidates, applying the Assef et al. criteria. Stripe 82 has optical photometry ≈2 times deeper th…
The Timing Behavior of the Central Compact Object Pulsar 1E 1207.4-5209
Gotthelf, E. V.; Halpern, J. P.
We present 20 yr of timing observations for 1E 1207.4-5209, the central compact object in supernova remnant PKS 1209-51/52, to follow up on our detection of an unexpected timing glitch in its spin-down. Using new XMM-Newton and NICER observations of 1E 1207.4-5209, we now find that the phase ephemeris can be well modeled by either two small glitch…
An X-ray detection of star formation in a highly magnified giant arc
Dahle, H.; Rigby, J. R.; Bayliss, M. B. +19 more
In the past decade, our understanding of how stars and galaxies formed during the first 5 billion years after the Big Bang has been revolutionized by observations that leverage gravitational lensing by intervening masses, which act as natural cosmic telescopes to magnify background sources. Previous studies have harnessed this effect to probe the …
Spectroscopic Determination of Stellar Parameters and Oxygen Abundances for Hyades/Field G-K Dwarfs
Honda, Satoshi; Takeda, Yoichi
It has been suggested that Fe abundances of K dwarfs derived from Fe I and Fe II lines show considerable discrepancies, and oxygen abundances determined from high-excitation O I 7771-5 triplet lines are appreciably overestimated (the problem becoming more serious toward lower Teff), which, however, has not yet been widely confirmed. Wit…