Search Publications
Radio Observations of Four Active Galactic Nuclei Hosting Intermediate-mass Black Hole Candidates: Studying the Outflow Activity and Evolution
Ho, Luis C.; Zhang, Shaohua; Yang, Jun +5 more
Observational searches for intermediate-mass black holes (IMBHs; 102-106 M ⊙) include relatively isolated dwarf galaxies. For those that host active galactic nuclei (AGNs), the IMBH nature may be discerned through the accretion-jet activity. We present radio observations of four AGN-hosting dwarf galaxies, which po…
Layered Ejecta Craters in the Candidate Landing Areas of China's First Mars Mission (Tianwen-1): Implications for Subsurface Volatile Concentrations
Di, Kaichang; Gou, Sheng; Yue, Zongyu +2 more
One important scientific objective of China's first Mars mission (Tianwen-1) is to investigate the martian surface soil characteristics and water-ice distribution. Layered ejecta craters (LECs) on Mars are characterized by their fluidized ejecta deposits which have been interpreted to indicate volatiles in the substrate where the impact occurred. …
Far-ultraviolet Flares on Accreting Protostars: Weak and Classical T Tauri Stellar Pair Analysis
Kowalski, Adam F.; France, Kevin; Hinton, P. C. +5 more
The far-ultraviolet (FUV) emission of classical T Tauri stars (CTTSs) is known to play an important role in protoplanetary disk dispersal and giant planet formation, yet the role played by protostellar flares in these processes is largely unknown. We use nearby star-forming regions as laboratories to probe the FUV flare characteristics of CTTSs an…
First Report of a Solar Energetic Particle Event Observed by China's Tianwen-1 Mission in Transit to Mars
Zhao, Lingling; Sun, Zhiyu; Yu, Yuhong +15 more
Solar energetic particles (SEPs) associated with flares and/or coronal mass ejection (CME)-driven shocks can impose acute radiation hazards on space explorations. To measure energetic particles in near-Mars space, the Mars Energetic Particle Analyzer (MEPA) instrument on board China's Tianwen-1 (TW-1) mission was designed. Here, we report the firs…
Evidence for C and Mg variations in the GD-1 stellar stream
Balbinot, Eduardo; Cabrera-Ziri, Ivan; Lardo, Carmela
Dynamically cold stellar streams are the relics left over from globular cluster dissolution. These relics offer a unique insight into a now fully disrupted population of ancient clusters in our Galaxy. Using a combination of Gaia eDR3 proper motions, optical and near-UV colours, we select a sample of likely Red Giant Branch stars from the GD-1 str…
Model-independent redshift estimation of BL Lac objects through very-high-energy observations
Bhatt, Nilay; Malik, Zahoor; Sahayanathan, Sunder +3 more
The very-high-energy (VHE) gamma-ray spectral indices of blazars show a strong correlation with the source redshift. The absence of any such correlation in low-energy gamma-rays and X-rays indicates the presence of extragalactic background light (EBL)-induced absorption of VHE gamma-rays. By employing a linear regression analysis, this observation…
Relationship between Total Solar Irradiance and Magnetic Flux during Solar Minima
Lean, Judith L.; Marchenko, Sergey V.; DeLand, Matthew T.
What drives the small total solar irradiance (TSI) changes of ~50-100 parts per million (compared with >1000 ppm solar-cycle amplitudes) during a deep solar minimum, i.e., in the practical absence of detectable sunspots and long-lasting active regions? We consider the epoch 2008 June-October and investigate multiple data sets (TSI; various Mg I…
A Very Long Baseline Array Trigonometric Parallax for RR Aql and the Mira Period-Luminosity Relation
Sun, Yan; Reid, Mark J.; Zhang, Bo +4 more
We report Very Long Baseline Array observations of 22 GHz H2O and 43 GHz SiO masers toward the Mira variable RR Aql. By fitting the SiO maser emission to a circular ring, we estimate the absolute stellar position of RR Aql and find agreement with Gaia astrometry to within the joint uncertainty of ≈1 mas. Using the maser astrometry we me…
Interplanetary Sheaths and Corotating Interaction Regions: A Comparative Statistical Study on Their Characteristics and Geoeffectiveness
Hajra, Rajkumar; Sunny, Jibin V.; Babu, Megha +1 more
Interplanetary sheaths and corotating interaction regions (CIRs), while having different solar sources, represent turbulent solar-wind plasma and magnetic field that can perturb the Earth's magnetosphere. We explore long-term solar-wind measurements upstream of the Earth during Solar Cycle 24, from January 2008 to December 2019, to compare their s…
X-Ray Intraday Variability of the TeV Blazar Markarian 421 with XMM-Newton
Gupta, Alok C.; Gaur, Haritma; Ostrowski, Michał +4 more
Highly variable Markarian 421 is a bright high-synchrotron energy peaked blazar showing a wide featureless nonthermal spectrum, making it a good candidate for our study of intraday flux and spectral variations over time. We analyze its X-ray observations over 17 yr, taken with the EPIC-pn instrument, to probe into the intraday variability properti…