THE IRIS NETWORK fOR WHOLE DISC HELIOSEISMOLOGY: RECENT RESULTS

EHGAMBERDIEV SH. A. The Korean Astronomical Society 1996 Journal of The Korean Astronomical Society Vol.29 No.suppl1

IRIS(International Research on the Interior of the sun) is the name of a worldwide network of 6 stations for whole disc Doppler shift measurements. The network has been operating since 1987 and by now a few series of a hundred days long unbroken (by day/night periodicity) data were received. Analysis of these data allowed to receivesome new results which are discussed in the paper.

Searching for LSB Dwarf Satellite Galaxies Around Nearby Galaxies in IMSNG Data

Gu Lim,Myungshin Im,Jisu Kim,Jeong Hwan Lee,Changsu Choi,S. Ehgamberdiev,O. Burkhonov,D.Mirzaqulov,IMSNG team 한국천문학회 2019 天文學會報 Vol.44 No.1

THE VERY EARLY LIGHT CURVE OF SN 2015F IN NGC 2442: A POSSIBLE DETECTION OF SHOCK-HEATED COOLING EMISSION AND CONSTRAINTS ON SN Ia PROGENITOR SYSTEM

Im, Myungshin,Choi, Changsu,Yoon, Sung-Chul,Kim, Jae-Woo,Ehgamberdiev, Shuhrat A.,Monard, Libert A. G.,Sung, Hyun-Il IOP Publishing 2015 The Astrophysical journal Supplement series Vol.221 No.1

<P>The main progenitor candidates of Type Ia supernovae (SNe Ia) are white dwarfs in binary systems where the companion star is another white dwarf (double degenerate (DD) system) or a less-evolved, non-degenerate star with R-* greater than or similar to 0.1 R-circle dot (single degenerate system). However, no direct observational evidence exists to tell us which progenitor system is more common. Recent studies suggest that the light curve of a supernova shortly after its explosion can be used to set a limit on the progenitor size, R-*. Here, we report high-cadence monitoring observations of SN 2015F, a normal SN Ia in the galaxy NGC 2442, starting about 84 days before the first light time. Using our daily cadence data, we capture the emergence of the radioactively powered light curve; more importantly, with >97.4% confidence, we detect possible dim precursor emission that appears roughly 1.5 days before the rise of the radioactively powered emission. The signal is consistent with theoretical expectations for a progenitor system involving a companion star with R-* similar or equal to 0.1-1 R-circle dot or a prompt explosion of a DD system, but is inconsistent with the typically invoked size of a white dwarf progenitor of R-* similar to 0.01 R-circle dot. Upper limits on the precursor emission also constrain the progenitor size to be R-* less than or similar to 0.1 R-circle dot with a companion star size of R-* less than or similar to 1.0 R-circle dot, excluding a very large companion star in the progenitor system. Additionally, we find that the distance to SN 2015F is 23.9 +/- 0.4 Mpc.</P>

NEWLY DISCOVERED FOOTPRINTS OF GALAXY INTERACTION AROUND SEYFERT 2 GALAXY NGC 7743

KIM, YONGJUNG,IM, MYUNGSHIN,CHOI, CHANGSU,HYUN, MINHEE,YOON, YONGMIN,TAAK, YOON CHAN,EHGAMBERDIEV, SHUHRAT A.,BURHONOV, OTABEK The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2

It has been suggested that only the most luminous AGNs ($L{\gtrsim}10^{45}erg/s$) are triggered by galaxy mergers, while less luminous AGNs ($L{\sim}10^{43}erg/s$) are driven by other internal processes. The lack of merging features in low luminosity AGN host galaxies has been a primary argument against the idea of merger triggering of low luminosity AGNs. But a merger, especially a rather minor one, might still have played an important role in low luminosity AGNs, as minor merging features at low luminosities are more difficult to identify than major merging features. Using SNUCAM on the 1.5 m telescope at Maidanak observatory, we obtained deep optical images of NGC 7743, a barred spiral galaxy classified as a Seyfert 2 AGN with a low bolometric luminosity of $5{\times}10^{42}erg/s$. Surprisingly, we discovered a merging feature around the galaxy, which indicates past merging activity in the galaxy. This example indicates that the merging fraction of low luminosity AGNs may be much higher than previously thought, hinting at the importance of galaxy mergers even in low luminosity AGNs.

INTENSIVE MONITORING SURVEY OF NEARBY GALAXIES (IMSNG)

Myungshin Im,Changsu Choi,Sungyong Hwang,Gu Lim,Joonho Kim,Sophia Kim,Gregory S. H. Paek,Sang-Yun Lee,Sung-Chul Yoon,Hyunjin Jung,성현일,Yeong-beom Jeon,Shuhrat Ehgamberdiev,Otabek Burhonov,Davron Milzaq 한국천문학회 2019 Journal of The Korean Astronomical Society Vol.52 No.1

Intensive Monitoring Survey of Nearby Galaxies (IMSNG) is a high cadence observation program monitoring nearby galaxies with high probabilities of hosting supernovae (SNe). IMSNG aims to constrain the SN explosion mechanism by inferring sizes of SN progenitor systems through the detection of the shock-heated emission that lasts less than a few days after the SN explosion. To catch the signal, IMSNG utilizes a network of 0.5-m to 1-m class telescopes around the world and monitors the images of 60 nearby galaxies at distances $D < 50$ Mpc to a cadence as short as a few hours. The target galaxies are bright in near-ultraviolet (NUV) with $M_{NUV} < -18.4$ AB mag and have high probabilities of hosting SNe (0.06 SN yr$^{-1}$ per galaxy). With this strategy, we expect to detect the early light curves of 3.4 SNe per year to a depth of $R \sim 19.5$ mag, enabling us to detect the shock-heated emission from a progenitor star with a radius as small as 0.1 $R_{\odot}$. The accumulated data will be also useful for studying aint features around the target galaxies and other science projects. So far, 18 SNe have occurred in our target fields (16 in IMSNG galaxies) over 5 years, confirming our SN rate estimate of 0.06 SN yr$^{-1}$ per galaxy.

Asteroid pairs: A complex picture

Pravec, P.,Fatka, P.,Vokrouhlický,, D.,Scheirich, P.,Ď,urech, J.,Scheeres, D.J.,Kuš,nirá,k, P.,Hornoch, K.,Galá,d, A.,Pray, D.P.,Krugly, Yu. N.,Burkhonov, O.,Ehgamberdiev, Elsevier 2019 Icarus Vol.333 No.-

<P><B>Abstract</B></P> <P>We studied a sample of 93 asteroid pairs, i.e., pairs of genetically related asteroids that are on highly similar heliocentric orbits. We estimated times elapsed since separation of pair members (i.e., pair age) that are between 7 × 10<SUP>3</SUP> yr and a few 10<SUP>6</SUP> yr. With photometric observations, we derived the rotation periods <I>P</I> <SUB>1</SUB> for all the primaries (i.e., the larger members of asteroid pairs) and a sample of secondaries (the smaller pair members). We derived the absolute magnitude differences of the studied asteroid pairs that provide their mass ratios <I>q</I>. For a part of the studied pairs, we refined their WISE geometric albedos and collected or estimated their taxonomic classifications. For 17 asteroid pairs, we also determined their pole positions. In two pairs where we obtained the spin poles for both pair components, we saw the same sense of rotation for both components and constrained the angles between their original spin vectors at the time of their separation. We found that the primaries of 13 asteroid pairs in our sample are actually binary or triple systems, i.e., they have one or two bound, orbiting secondaries (satellites). As a by-product, we found also 3 new young asteroid clusters (each of them consisting of three known asteroids on highly similar heliocentric orbits). We compared the obtained asteroid pair data with theoretical predictions and discussed their implications. We found that 86 of the 93 studied asteroid pairs follow the trend of primary rotation period vs mass ratio that was found by Pravec et al. (2010). Of the 7 outliers, 3 appear insignificant (may be due to our uncertain or incomplete knowledge of the three pairs), but 4 are high mass ratio pairs that were unpredicted by the theory of asteroid pair formation by rotational fission. We discuss a (remotely) possible way that they could be created by rotational fission of flattened parent bodies followed by re-shaping of the formed components. The 13 asteroid pairs with binary primaries are particularly interesting systems that place important constraints on formation and evolution of asteroid pairs. We present two hypotheses for their formation: The asteroid pairs having both bound and unbound secondaries could be “failed asteroid clusters”, or they could be formed by a cascade primary spin fission process. Further studies are needed to reveal which of these two hypotheses for formation of the paired binary systems is real.</P>