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Wojciech Dimitrov

Publications and source records attributed to Wojciech Dimitrov.

6 recordsLinked to original sources

TOI-7475 spectroscopic follow up - detection of a massive hot Jupiter on an eccentric orbit

We present the first spectroscopic follow-up for TOI-7475, and report the detection of a planetary-mass companion. Transits with a period of 3.25 days were observed by TESS. The dips in brightness are 0.006 mag and last approximately 4.5 hours. The host star is a spectral type F5 with a mass of approximately 1.48 M$_{\odot}$. We collected 24 high resolution echelle spectra using the PST1 telescope. Analysis of the TESS photometric data and our radial velocities was performed using the Wilson-Devinney method. We obtained a planetary mass of the companion of 12.0$\pm$1.0 M$_{\mathrm{jup}}$. The small semi-major axis and short orbital period classify the planet as a Hot Jupiter. Its orbit is elliptical with an eccentricity of 0.16. The ellipticity is evident in the spectroscopic data and could indicates the young age of the system.

astro-ph.EP

Atomic gas properties at the positions of supernovae Type Ia, II, and Ib/c

Understanding which stars explode as which type of supernovae (SNe) is crucial to measure their contribution to the metal production and feedback halting star formation. Most of the studies of the gas in the environment of SNe are limited by a small sample size ($<10$). The goal of this paper is to present the first analysis of atomic gas properties at the positions of a statistically significant sample of SNe in order to constrain their nature. We selected 133 SNe (29 Ia, 77 II, 27 Ib/c) which have exploded in galaxies with existing atomic gas data. In order to test whether SN positions trace enhancements in the atomic gas distribution, we analyzed the fraction of pixels on the {\hi} map which are fainter than the pixel in which SN is located and the fraction of the {\hi} flux contributed by these pixels. All types of SNe deviate from the completely random distribution. From the three types of SNe, Type II showed the largest offset from the {\hi} distribution, preferring even higher concentrations of atomic gas. This type of SNe deviated also from being proportional to the stellar surface density of the host. The results are, however, complicated by the limits of the survey in size, and in the un-even resolution of the {\hi} observations. Furthermore, by direct comparison between the three SN types, we observed that the distributions of these populations are still consistent with each other. The obtained results fail to ascertain that Ib/c core-collapse SNe, and possibly also Type II SNe, are connected with the densest concentrations of atomic gas in their hosts, unlike what has been suggested for GRBs and Ic-BL SNe. Hence, the birth of progenitors of Type II and Ib/c SNe is still consistent with being connected with the current star formation in their hosts, whereas the progenitors of GRBs and Type Ic-BL SNe require more special conditions to form, for example low metallicity.

astro-ph.GA

Recent humps and superhumps observations and an estimation of outburst parameters of the AM CVn star CR Boo

We present our observational results of AM CVn star CR Boo in the UBVR bands. Our observational campaign includes data obtained over 5 nights with the National Astronomical Observatory Rozhen, Belogradchik and the AS Vidojevica telescopes. During the whole time of our observations the brightness of the system varied between $13.95 - 17.23$ in B band. We report the appearance of humps during the period of quiescence and superhumps during the active state of the object, (where the latter are detected in two nights). We obtain the superhumps periodicity for two nights, $P_{sh}\approx 24.76 - 24.92$ min. The color during maximum brightness is estimated as $ - 0.107 < (B-V)_{0} < 0.257$ and the corresponding temperature is in the range as $7700 [K] < T(B-V)_{0} < 11700 [K]$. We found that CR Boo varies from bluer to redder in the nights with outbursts activity. The star becomes bluer during the times of superhumps.

astro-ph.SR

NGC 2770: high supernova rate due to interaction

Galaxies which hosted many core-collapse supernovae (SN) explosions can be used to study the conditions necessary for the formation of massive stars. NGC 2770 was dubbed a SN factory, because it hosted four core-collapse SNe in 20 years (three type Ib and one type IIn). Its star formation rate (SFR) was reported not to be enhanced and therefore not compatible with such a high SN rate. We aim at explaining the high SN rate of NGC 2770. We used archival HI line data for NGC 2770 and reinterpret the Halpha and optical continuum data. Even though the continuum-based SFR indicators do not yield high values, the dust-corrected Halpha luminosity implies a high SFR, consistent with the high SN rate. Such disparity between the SFR estimators is an indication of recently enhanced star formation activity, because the continuum indicators trace long timescale of the order of 100 Myr, unlike the line indicators, which trace timescales of the order of 10 Myr. Hence, the unique feature of NGC 2770 compared to other galaxies is the fact that it is observed very recently after the enhancement of the SFR. It also has high dust extinction, E(B-V) above 1 mag. We provide support for the hypothesis that the increased SFR in NGC 2770 is due to the interaction with its companion galaxies. We report an HI bridge between NGC 2770 and its closest companion and the existence of a total of four companions within 100 kpc (one identified for the first time). There are no clear HI concentrations close to the positions of SNe in NGC 2770 such as those detected for hosts of gamma-ray bursts (GRBs) and broad-lined SNe type Ic (IcBL). This suggests that the progenitors of type Ib SNe are not born out of recently accreted atomic gas, as was suggested for GRB and IcBL SN progenitors.

astro-ph.HE

$τ$ Ori and $τ$ Lib: Two new massive heartbeat binaries

We report the discovery of two massive eccentric systems with BRITE data, $τ$ Ori and $τ$ Lib, showing heartbeat effects close to the periastron passage. $τ$ Lib exhibits shallow eclipses that will soon vanish due to the apsidal motion in the system. In neither system, tidally excited oscillations were detected.

astro-ph.SR

ESpeRo: Echelle Spectrograph Rozhen

In this paper we describe the echelle spectrograph of the 2 meter telescope of the Rozhen National Astronomical Observatory. The spectrograph is a cross-dispersed, bench-mounted, fiber-fed instrument giving a resolution from $\sim$30000 to $\sim$45000. The spectral range obtained in one single image is from 3900 to 9000 Å. We describe the parameters of the fiber injection and the guiding unit, of the spectrograph itself, and of the detector. The identified orders and the resulting resolving power are presented. The opportunity to increase of the resolution by using a narrower slit is discussed and the corresponding loss of flux is calculated. The expected signal-to-noise ratio for a set of stars of different magnitudes was derived. Some of the first results obtained with ESpeRo are shortly described.

astro-ph.IM