arXiv subjects

V. V. Kouprianov

Publications and source records attributed to V. V. Kouprianov.

12 recordsLinked to original sources

arXiv2024

Searching for precursor activity of Type IIn Supernovae

We conducted a search for luminous outbursts prior to the explosion of Type IIn Supernovae (SNe IIn). We built a sample of 27 objects spectroscopically classified as SNe IIn, all located at $z<0.015$. Using deep archival SN fields images taken up to nearly 20 years prior from transient surveys (PTF, ZTF, DES, CHASE) and major astronomical observatories (ESO and NOAO), we found at least one outburst years to months before the explosion of seven SNe IIn, the earliest precursor being 10 years prior to the explosion of SN 2019bxq. The maximum absolute magnitudes of the outbursts range between -11.5 mag and -15 mag, and the eruptive phases last for a few weeks to a few years. The $g-r$ colour measured for three objects during their outburst is relatively red, with $g-r$ ranging between 0.5 and 1.0 mag. This is similar to the colour expected during the eruptions of Luminous Blue Variables. We noticed that the SNe with pre-SN outbursts have light curves with faster decline rates than those that do not show pre-SN outbursts. SN 2011fh is remarkable, as it is still visible 12 years after the luminous SN-like event, indicating that the progenitor possibly survived, or that the interaction is still on-going. We detect precursor activity in 29% of bona-fide SNe~IIn in our sample. However, a quantitative assessment of the observational biases affecting the sample suggests that this fraction underestimates the intrinsic precursor occurrence rate.

astro-ph.HE↗

arXiv2022

Host galaxy magnitude of OJ 287 from its colours at minimum light

OJ 287 is a BL Lacertae type quasar in which the active galactic nucleus (AGN) outshines the host galaxy by an order of magnitude. The only exception to this may be at minimum light when the AGN activity is so low that the host galaxy may make quite a considerable contribution to the photometric intensity of the source. Such a dip or a fade in the intensity of OJ 287 occurred in November 2017, when its brightness was about 1.75 magnitudes lower than the recent mean level. We compare the observations of this fade with similar fades in OJ 287 observed earlier in 1989, 1999, and 2010. It appears that there is a relatively strong reddening of the B$-$V colours of OJ 287 when its V-band brightness drops below magnitude 17. Similar changes are also seen V$-$R, V$-$I, and R$-$I colours during these deep fades. These data support the conclusion that the total magnitude of the host galaxy is $V=18.0 \pm 0.3$, corresponding to $M_{K}=-26.5 \pm 0.3$ in the K-band. This is in agreement with the results, obtained using the integrated surface brightness method, from recent surface photometry of the host. These results should encourage us to use the colour separation method also in other host galaxies with strongly variable AGN nuclei. In the case of OJ 287, both the host galaxy and its central black hole are among the biggest known, and its position in the black hole mass-galaxy mass diagram lies close to the mean correlation.

astro-ph.GA↗

arXiv2019

Full orbital solution for the binary system in the northern Galactic disc microlensing event Gaia16aye

Gaia16aye was a binary microlensing event discovered in the direction towards the northern Galactic disc and was one of the first microlensing events detected and alerted to by the Gaia space mission. Its light curve exhibited five distinct brightening episodes, reaching up to I=12 mag, and it was covered in great detail with almost 25,000 data points gathered by a network of telescopes. We present the photometric and spectroscopic follow-up covering 500 days of the event evolution. We employed a full Keplerian binary orbit microlensing model combined with the motion of Earth and Gaia around the Sun to reproduce the complex light curve. The photometric data allowed us to solve the microlensing event entirely and to derive the complete and unique set of orbital parameters of the binary lensing system. We also report on the detection of the first-ever microlensing space-parallax between the Earth and Gaia located at L2. The properties of the binary system were derived from microlensing parameters, and we found that the system is composed of two main-sequence stars with masses 0.57$\pm$0.05 $M_\odot$ and 0.36$\pm$0.03 $M_\odot$ at 780 pc, with an orbital period of 2.88 years and an eccentricity of 0.30. We also predict the astrometric microlensing signal for this binary lens as it will be seen by Gaia as well as the radial velocity curve for the binary system. Events such as Gaia16aye indicate the potential for the microlensing method of probing the mass function of dark objects, including black holes, in directions other than that of the Galactic bulge. This case also emphasises the importance of long-term time-domain coordinated observations that can be made with a network of heterogeneous telescopes.

astro-ph.SR↗

arXiv2019

YZ Phe: an active contact binary with variation of the O'Connell effect and orbital period change

YZ Phe is a very short-period contact binary (Sp.= $K2\,V$) with an orbital period of 0.2347 days near the short period limit (0.22 d). We present the complete light curves in $VRI$ bands, which photometric data were obtained with the 0.61-m telescope of PROMPT-8 at CTIO in Chile during June to October 2016 and August 2017. The photometric solutions were determined by using the W-D method and the results reveal that YZ Phe is a W-subtype shallow contact binary ($f\sim$ 10%, $q$ = 2.635 or $1/q$ = 0.379 for W subtype) with rotational motion of a large hot spot on the more massive component, showing a strong O'Connell effect with variation of maxima in photometric time series at period of 4.20 yr and stellar cycle at period of 1.28 yr. By compiling all available eclipse times, the result shows a long-term period decrease at a rate of $\mathrm{d}P/\mathrm{d}t = -2.64(\pm 0.02)\times 10^{-8}$ d $yr^{-1}$, superimposed on a cyclic variation ($A_3$ = 0.0081 days and $P_3$ = 40.76 years). This variation cannot be explained by Applegate mechanism. Thus, the cyclic change may be interpreted as light-travel time effect via the presence of a cool third body. Based on photometric solutions, the third light was detected with 2% contribution of total light in $V$ and $I$ bands. Those support the existence of a third body. For the long-term period decrease, it can be explained by mass transfer from the more massive component ($M_2 \sim 0.74 M_{\odot}$) to the less massive one ($M_1 \sim 0.28 M_{\odot}$) or plus AML via magnetic braking. With $1/q$ $<$ 0.4 and long-term period decrease, all suggest that YZ Phe is on the AML-controlled state and its fill-out factor will increase, as well as the system will evolve into a deeper normal contact binary.

astro-ph.SR↗

arXiv2018

RW Dor: A G-type shallow contact binary with new orbital period investigation

New CCD photometric light curves of short period (P=0.285d) eclipsing binary RW Dor are presented. The observations performed with the PROMPT-8 robotic telescope at CTIO in Chile from March 2015 to March 2017. The other eclipse timings were obtained from the 2.15-m JS telescope at CASLEO, San Juan, Argentina in December 2011. By light-curve analysis, it is found that RW Dor is a W-type shallow contact binary with a fill-out factor $f \sim 11\%$ and high mass ratio $q \sim 1.587$ (1/q = 0.63), where the hotter component is the less massive one ($M_1 \sim 0.52M_{\odot}$ and $M_2 \sim 0.82M_{\odot}$). For orbital period investigation, the new fifteen eclipse times and those in previous published were compiled. Based on $O-C$ analysis with very weak evidence suggests that a long-term period decrease with a rate of $\mathrm{d}P/\mathrm{d}t = -9.61\times10^{-9}$ d $\textrm{yr}^{-1}$ is superimposed on a cyclic variation ($A_3$ = 0.0054 days and $P_3$ = 49.9 yrs). The long-term period decrease can be interpreted as mass transfer from the more massive component to the less massive one or combine with the angular momentum loss (AML) via magnetic braking. In addition, with the marginal contact phase, high mass ratio (1/q $>$ 0.4) and the long-term period decrease, all suggest that RW Dor is a newly formed contact binary via a Case A mass transfer and it will evolve into a deeper normal contact binary. If the cyclic change is correct, the light-travel time effect via the presence of a cool third body will be more plausible to explain for this.

astro-ph.SR↗

arXiv2018

TY Pup: a low-mass-ratio and deep contact binary as a progenitor candidate of luminous red novae

TY Pup is a well-known bright eclipsing binary in southern hemisphere with an orbital period of 0.8192 days. New light curves in $B, V, (RI)_C$ bands were obtained with the 0.61-m reflector robotic telescope (PROMPT-8) at CTIO in Chile from January to February 2015 and from March to April 2017. By analyzing those photometric data with the W-D method, it is found that TY Pup is a low-mass-ratio ($q \sim$ 0.184) and deep contact binary with a high fill-out factor ($84.3\,\%$). An investigation of all available times of minimum light including three new ones obtained with the 60-cm and the 1.0-m telescopes at Yunnan Observatories in China indicates that the period change of TY Pup is complex. An upward parabolic variation in the $O-C$ diagram is detected to be superimposed on a cyclic oscillation. The upward parabolic change reveals a long-term continuous increase in the orbital period at a rate of $\mathrm{d}P/\mathrm{d}t = 5.57(\pm 0.08)\times10^{-8}$ d $\textrm{yr}^{-1}$. The period increase can be explained by mass transfer from the less massive component ($M_2 \sim 0.3 M_{\odot}$) to the more massive one ($M_1 \sim 1.65 M_{\odot}$) and the mass ratio of the binary system will become more smaller. In this way, the binary will be merging when it meets the criterion that the orbital angular momentum is less than 3 times the total spin angular momentum, i.e., $J_{orb} < 3J_{rot}$. This suggests that the system will finally merge into a rapid-rotating single star and may produce a luminous red nova. The cyclic oscillation in the $O-C$ diagram can be interpreted by the light-travel time effect (LITE) via the presence of an additional companion.

astro-ph.SR↗

arXiv2018

Constraining the period of the ringed secondary companion to the young star J1407 with photographic plates

Context. The 16 Myr old star 1SWASP J140747.93-394542.6 (V1400 Cen) underwent a series of complex eclipses in May 2007, interpreted as the transit of a giant Hill sphere filling debris ring system around a secondary companion, J1407b. No other eclipses have since been detected, although other measurements have constrained but not uniquely determined the orbital period of J1407b. Finding another eclipse towards J1407 will help determine the orbital period of the system, the geometry of the proposed ring system and enable planning of further observations to characterize the material within these putative rings. Aims. We carry out a search for other eclipses in photometric data of J1407 with the aim of constraining the orbital period of J1407b. Methods. We present photometry from archival photographic plates from the Harvard DASCH survey, and Bamberg and Sonneberg Observatories, in order to place additional constraints on the orbital period of J1407b by searching for other dimming and eclipse events. Using a visual inspection of all 387 plates and a period-folding algorithm we performed a search for other eclipses in these data sets. Results. We find no other deep eclipses in the data spanning from 1890 to 1990, nor in recent time-series photometry from 2012-2018. Conclusions. We rule out a large fraction of putative orbital periods for J1407b from 5 to 20 years. These limits are still marginally consistent with a large Hill sphere filling ring system surrounding a brown dwarf companion in a bound elliptical orbit about J1407. Issues with the stability of any rings combined with the lack of detection of another eclipse, suggests that J1407b may not be bound to J1407.

astro-ph.EP↗

arXiv2018

Skynet Algorithm for Single-Dish Radio Mapping I: Contaminant-Cleaning, Mapping, and Photometering Small-Scale Structures

We present a single-dish mapping algorithm with a number of advantages over traditional techniques. (1) Our algorithm makes use of weighted modeling, instead of weighted averaging, to interpolate between signal measurements. This smooths the data, but without blurring the data beyond instrumental resolution. Techniques that rely on weighted averaging blur point sources sometimes as much as 40%. (2) Our algorithm makes use of local, instead of global, modeling to separate astronomical signal from instrumental and/or environmental signal drift along the telescope's scans. Other techniques, such as basket weaving, model this drift with simple functional forms (linear, quadratic, etc.) across the entirety of scans, limiting their ability to remove such contaminants. (3) Our algorithm makes use of a similar, local modeling technique to separate astronomical signal from radio-frequency interference (RFI), even if only continuum data are available. (4) Unlike other techniques, our algorithm does not require data to be collected on a rectangular grid or regridded before processing. (5) Data from any number of observations, overlapping or not, may be appended and processed together. (6) Any pixel density may be selected for the final image. We present our algorithm, and evaluate it using both simulated and real data. We are integrating it into the image-processing library of the Skynet Robotic Telescope Network, which includes optical telescopes spanning four continents, and now also Green Bank Observatory's 20-meter diameter radio telescope in West Virginia. Skynet serves hundreds of professional users, and additionally tens of thousands of students, of all ages. Default data products are generated on the fly, but will soon be customizable after the fact.

astro-ph.IM↗

arXiv2018

Toward Understanding the B[e] Phenomenon. VII. AS 386, a single-lined binary with a candidate black hole component

We report the results of spectroscopic and photometric observations of the emission-line object AS 386. For the first time, we found that it exhibits the B[e] phenomenon and fits the definition of an FS CMa type object. The optical spectrum shows the presence of a B-type star with the following properties: T_ eff = 11000+/-500 K, log L/L_sun = 3.7+/-0.3, a mass of 7+/-1 M_sun, and a distance D = 2.4+/-0.3 kpc from the Sun. We detected regular radial velocity variations of both absorption and emission lines with the following orbital parameters: P_orb = 131.27+/-0.09 days, semi-amplitude K_1 = 51.7+/-3.0 km/s, systemic radial velocity gamma = -31.8+/-2.6 km/s, and a mass function of f(m) = 1.9+/-0.3 M_sun. AS 386 exhibits irregular variations of the optical brightness (V=10.92+/-0.05 mag), while the near-IR brightness varies up to ~0.3 mag following the spectroscopic period. We explain this behavior by a variable illumination of the dusty disk inner rim by the B-type component. Doppler tomography based on the orbital variations of emission-line profiles shows that the material is distributed near the B-type component and in a circumbinary disk. We conclude that the system has undergone a strong mass transfer that created the circumstellar material and increased the B-type component mass. The absence of any traces of a secondary component, whose mass should be >= 7 M_sun, suggests that it is most likely a black hole.

astro-ph.SR↗

arXiv2017

The early detection and follow-up of the highly obscured Type II supernova 2016ija/DLT16am

We present our analysis of the Type II supernova DLT16am (SN~2016ija). The object was discovered during the ongoing $\rm{D}<40\,\rm{Mpc}$ (DLT40) one day cadence supernova search at $r\sim20.1\,\rm{mag}$ in the `edge-on' nearby ($D=20.0\pm1.9\,\rm{Mpc}$) galaxy NGC~1532. The subsequent prompt and high-cadenced spectroscopic and photometric follow-up revealed a highly extincted transient, with $E(B-V)=1.95\pm0.15\,\rm{mag}$, consistent with a standard extinction law with $R_V=3.1$ and a bright ($M_V=-18.49\pm0.65\,\rm{mag}$) absolute peak-magnitude. The comparison of the photometric features with those of large samples of Type II supernovae reveals a fast rise for the derived luminosity and a relatively short plateau phase, with a slope of $S_{50V}=0.84\pm0.04\,\rm{mag}/50\,\rm{d}$ consistent with the photometric properties typical of those of fast declining Type II supernovae. Despite the large uncertainties on the distance and the extinction in the direction of DLT16am, the measured photospheric expansion velocity and the derived absolute $V$-band magnitude at $\sim50\,\rm{d}$ after the explosion match the existing luminosity-velocity relation for Type II supernovae.

astro-ph.HE↗

arXiv2017

The fading of Cassiopeia A, and improved models for the absolute spectrum of primary radio calibration sources

Based on five years of observations with the 40-foot telescope at Green Bank Observatory (GBO), Reichart & Stephens (2000) found that the radio source Cassiopeia A had either faded more slowly between the mid-1970s and late 1990s than Baars et al. (1977) had found it to be fading between the late 1940s and mid-1970s, or that it had rebrightened and then resumed fading sometime between the mid-1970s and mid-1990s, in L band (1.4 GHz). Here, we present 15 additional years of observations of Cas A and Cyg A with the 40-foot in L band, and three and a half additional years of observations of Cas A, Cyg A, Tau A, and Vir A with GBO's recently refurbished 20-meter telescope in L and X (9 GHz) bands. We also present a more sophisticated analysis of the 40-foot data, and a reanalysis of the Baars et al. (1977) data, which reveals small, but non-negligible differences. We find that overall, between the late 1950s and late 2010s, Cas A faded at an average rate of $0.670 \pm 0.019$ %/yr in L band, consistent with Reichart & Stephens (2000). However, we also find, at the 6.3$σ$ credible level, that it did not fade at a constant rate. Rather, Cas A faded at a faster rate through at least the late 1960s, rebrightened (or at least faded at a much slower rate), and then resumed fading at a similarly fast rate by, at most, the late 1990s. Given these differences from the original Baars et al. (1977) analysis, and given the importance of their fitted spectral and temporal models for flux-density calibration in radio astronomy, we update and improve on these models for all four of these radio sources. In doing so, we additionally find that Tau A is fading at a rate of $0.102^{+0.042}_{-0.043}$ %/yr in L band.

astro-ph.HE↗

arXiv2014

The orbital evolution of a passive high-orbit fragment with large surface area

The observation data for artificial celestial body 43096, which had been obtained during 2006-2012 within the framework of international project "The Scientific Network of Optical Instruments for Astrometric and Photometric Observations" - International Scientific Optical Network (ISON), were processed. The Keplerian elements and state vector as of 24 November 2006 01:55:50.76 UTC were determined. The numerical integration of the motion equations was performed accounting for the perturbations due to the polar flattening of the Earth, Moon and Sun, as well as the solar radiation pressure. Based on the numerical model of a motion in the near-Earth space that accounts for only the most powerful perturbations, a new method for de-orbiting artificial celestial bodies from high altitudes is suggested. For the first time such a considerable amount of data over long time intervals was gathered for the objects with high area-to-mass ratio that enabled to determine their specific characteristics.

astro-ph.EP↗