Konstantin N. Grankin

Head of Stellar Physics Department, CrAO. Leading Researcher, Dr. Sci. (physics and mathematics).


Web of Science Researcher ID: S-9426-2017

ORCID: 0000-0001-5707-8448

Scopus Author ID: 6701763277

Russian Science Citation Index (SPIN-code): 2064-7767

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Konstantin Nikolaevich Grankin graduated from the N.G. Chernyshevsky Saratov State University in 1984 with a degree in physics, physics teacher. From 1984 to 1987 he worked at the Saratov Branch of the All-Union Scientific Research Institute of Optico-Physical Measurements (VNIIOFI) as an engineer servicing a powerful infrared CO2 laser. From 1987 to 2007 he worked at the Astronomical Institute of the Academy of Sciences of Uzbekistan in different positions, from senior engineer to head of the Variable Stars Department. Since 2007, he has been working at CrAO RAS as a leading researcher and head of Stellar Physics Department.

In 1995 he defended his PhD thesis "Study of rotational modulation in young nonstationary stars". In 2022 he defended his doctoral thesis "Physical properties and evolutionary state of young stars of low and intermediate masses".

The scientific work of K.N. Grankin is related to the physics of various variable stars, in particular young T Tauri stars (TTS), Herbig Ae/Be stars (HAeBe) and other related objects. He has co-authored more than 180 scientific papers, 98 of which have been published in peer-reviewed journals, with 2806 citations and an h-index of 29.

From 1987 to 2007 K.N. Grankin actively participated in the photometric observations carried out within the ROTOR program at the Maidanak High-Altitude Observatory (Uzbekistan). As a result of this program, a unique database of photometric data was created, which contains more than one hundred thousand UBVR measurements for 370 objects from different star-forming regions (SFRs).

He developed a software package for the primary processing of photometric observations and implementing various methods of statistical and periodogram analysis of astronomical time series.

K.N. Grankin identified six candidates for close binary systems among several dozen young stars and detected quasicyclic variations in the brightness of 38 HAeBe stars. He found rotational modulation of brightness due to the presence of cool spots in 88 TTS. He showed that the cyclic and quasi-cyclic photometric variability of HAeBe stars can be caused by the presence of circumstellar structures of different origin.

He extensively studied the properties of the spotted rotational modulation in 60 TTS with weak emission lines (WTTS) in the Taurus-Auriga SFR. He determined the size and temperature of the spotted areas in several WTTS and traced the evolution of these parameters with time. He detected the phenomenon of stability of initial epochs and rotation periods for 17 WTTS over a time interval of 5 to 19 years. Such stability indicates that the active region in each WTTS remains on a particular meridian for many years.

K.N. Grankin analyzed significant changes in the amplitude of the light curves of spotted WTTS and showed that the decrease in the amplitude of brightness modulation was not due to a decrease in the total area of spots, as previously supposed, but to a more uniform distribution of spots over the stellar surface. This conclusion was later confirmed by Doppler imaging of the surface of several selected WTTS (in collaboration with J.-F. Donati, France).

As a co-author, K.N. Grankin contributed to a series of papers investigating AA Tau - the first prototype of dippers. These papers allowed for an extensive study of the processes of accretion of matter from the protoplanetary disk under the control of the dipole component of the magnetic field of a young star (in collaboration with J. Bouvier, France).

He showed that the average age (~2.3 Myr) of the younger subgroup of WTTS that have lost their protoplanetary disks practically coincides with the time of the end of the active disk accretion phase, determined from the analysis of a representative sample of low-mass stars in seven young clusters. It turned out that the time of disruption of protoplanetary disks, counted from the moment when accretion has stopped, can be very short, about 0.4 Myr.

K.N. Grankin is a member of the European Astronomical Society and the International Astronomical Union. He holds the title of the Honored Worker of Science and Technology of the Republic of Crimea.

Publications in scientific journals