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Vladimir M. Lipunov

Publications and source records attributed to Vladimir M. Lipunov.

9 recordsLinked to original sources
arXiv2026

Variable Red Giants Exploration with MASTER Robotic Net: Main Algorithms and Study of Three Mira-type Targets

We are discussing the capabilities of MASTER network of robotic telescopes to study variable red giant stars. We report the discovery and present archival light curves for three optical transients, connected with long period variable red giants, based on MASTER Robotic Net all-sky survey observations and archival MASTER light curves at Lomonosov database storage. We demonstrate transient detection frames and light curves for three Mira-type variables: MASTER OT $J083717.54-573411.1$, MASTER OT $J190436.33+192828.7$ and MASTER OT $J07010810-6818548$. Spectroscopically validated carbon star MASTER OT $J07010810-6818548$ shows mean magnitude growth but constant pulsation period which may indicate the presence of a long secondary period. As the result of MASTER wide-field images analysis at Lomonosov supercomputer data storage we present the 8-years historical light curves for all three objects with period calculations for all three Mira-type variables. We estimated fundamental astrophysical parameters for all three Mira-type variables: luminosities, radii, and zero age main sequence (ZAMS) masses.

astro-ph.SR↗
arXiv2023

GRB 180128A: A Second Magnetar Giant Flare Candidate from the Sculptor Galaxy

Magnetars are slowly rotating neutron stars that possess the strongest magnetic fields ($10^{14}-10^{15} \mathrm{G}$) known in the cosmos. They display a range of transient high-energy electromagnetic activity. The brightest and most energetic of these events are the gamma-ray bursts (GRBs) known as magnetar giant flares (MGFs), with isotropic energy $E\approx10^{44}-10^{46} \mathrm{erg}$. There are only seven detections identified as MGFs to date: three unambiguous events occurred in our Galaxy and the Magellanic Clouds, and the other four MGF candidates are associated with nearby star-forming galaxies. As all seven identified MGFs are bright at Earth, additional weaker events remain unidentified in archival data. We conducted a search of the Fermi Gamma-ray Burst Monitor (GBM) database for candidate extragalactic MGFs and, when possible, collected localization data from the Interplanetary Network (IPN) satellites. Our search yielded one convincing event, GRB 180128A. IPN localizes this burst with NGC 253, commonly known as the Sculptor Galaxy. This event is the second MGF in modern astronomy to be associated with this galaxy and the first time two bursts are associated with a single galaxy outside our own. Here, we detail the archival search criteria that uncovered this event and its spectral and temporal properties, which are consistent with expectations for a MGF. We also discuss the theoretical implications and finer burst structures resolved from various binning methods. Our analysis provides observational evidence for an eighth identified MGF.

astro-ph.HE↗
arXiv2017

Viewing short Gamma-ray Bursts from a different angle

The recent coincident detection of gravitational waves (GW) from a binary neutron star merger with aLIGO/Virgo and short-lived gamma-ray emission with Fermi/GBM (called GW 170817) is a milestone for the establishment of multi-messenger astronomy. Merging neutron stars (NS) represent the standard scenario for short-duration (< 2 sec) gamma-ray bursts (GRBs) which are produced in a collimated, relativistically expanding jet with an opening angle of a few degrees and a bulk Lorentz factor of 300-1000. While the present aLIGO detection is consistent with predictions, the measured faint gamma-ray emission from GW 170817A, if associated to the merger event at a distance of 40 Mpc, is about 1000x less luminous than known short-duration GRBs (sGRBs). Hence, the presence of this sGRB in the local Universe is either a very rare event, or points to a dramatic ignorance of the emission properties of sGRBs outside their narrow jets. Here we show that the majority of previously detected faint sGRBs are local, at redshift smaller than 0.1, seen off-axis. In contrast, the brighter sGRBs are seen on-axis, and therefore out to larger distances, consistent with the measured redshift distribution. Examining the observer-frame parameter space of all Fermi/GBM sGRBs shows that the sGRB associated with GW 170817A is extreme in its combination of flux, spectral softness and temporal structure. We identify a group of similar GRBs, one of which has been associated to a bright galaxy at 75 Mpc. We incorporate off-axis emission in the estimate of the rates of sGRBs, and predict that the majority of future GW-detections of NS-NS mergers will be accompanied by faint gamma-ray emission, contrary to previous thinking. The much more frequent off-axis emission of sGRBs also implies a much higher deadly rate of gamma-rays for extraterrestrial life in the Universe.

astro-ph.HE↗
arXiv2016

MASTER optical polarization variability detection in the Microquasar V404 Cyg/GS2023+33

On 2015 June 15 the Swift space observatory discovered that the Galactic black hole candidate V404 Cyg was undergoing another active X-ray phase, after 25 years of inactivity (Barthelmy et al. 2015). Twelve telescopes of the MASTER Global Robotic Net located at six sites across four continents were the first ground based observatories to start optical monitoring of the microquasar after its gamma-ray wakeup at 18h 34m 09s U.T. on 2015 June 15 (Lipunov et al. 2015). In this paper we report, for the first time, the discovery of variable optical linear polarization, changing by 4-6% over a timescale of approximately 1 h, on two different epochs. We can conclude that the additional variable polarization arisies from the relativistic jet generated by the black hole in V404Cyg. The polarization variability correlates with optical brightness changes, increasing when the flux decreases.

astro-ph.HE↗
arXiv1997

Relativistic Binary Merging Rates

The Invited Review on Joint Discussion "High Energy Transients" on XXIIIrd General Assembly of IAU, Kioto, 1997 is presented. The simulated rates of neutron star + neutron star, neutron star + black hole and black hole + black hole mergings are considered in relation with the problem of GRBursts origin and gravitational waves detection.

astro-ph↗
arXiv1997

The radioastronomical "Time Machine" effect and the solution of gamma ray bursts mystery

The possible low-frequency radio emission from the progenitors of gamma ray bursts can experience a delay from tens of seconds to hours on the way to the observer due to the dispersion in galactic and extragalactic plasma, and thus reach the observer as a radio afterglow of the burst. This opens a unique possibility (peculiar "Time Machine") of seeing what happened in that place before the catastrophe.

astro-ph↗
arXiv1996

Pulsars revived by gravitational waves

Binary neutron stars mergers that are expected to be the most powerful source of energy in the Universe definitely exist in nature, as is proven by the observed behavior of the Hulse-Taylor binary radio pulsar. Though most of energy in such events is radiated in gravitational waves, there probably exist several mechanisms giving also electromagnetic radiation. We propose a new one, involving a revival of the radio pulsar several orbital cycles before the merger.

astro-ph↗