arXiv subjects

T. Kaminski

Publications and source records attributed to T. Kaminski.

27 records · Page 2Linked to original sources

arXiv2012

The size, luminosity and motion of the extreme carbon star IRC+10216 (CW Leonis)

Very Large Array observations of the extreme carbon star IRC+10216 at 7 mm wavelength with 40 milli-arcsecond resolution resolve the object's radio emission, which forms an almost round uniform disk of 83 milli arcseconds diameter, corresponding to 11 AU (for an assumed distance of 130 pc). We find a brightness temperature of 1630 K for the radio photosphere. Since the emission is optically thick, we can directly estimate IRC+10216's average luminosity, which is 8600 L(Sun). This value is in excellent agreement with what is predicted from the period-luminosity relation for carbon-rich Miras. Assuming an effective temperature of 2750 K for IRC+10216, it implies an optical photospheric diameter of 3.8 AU. Our precise determination of IRC+10216's proper motion fits the picture presented by far-ultraviolet and far-infrared wavelength observations of its interaction region with the interstellar medium (its "astrosphere"): the star moves roughly in the direction expected from the morphology of the termination shock and its astrotail structures. Calculation of its three dimensional velocity and an analysis of the kinematics of its surrounding interstellar medium (ISM) suggest an appreciable relative velocity of 42 km s/s, which is about half the value discussed in recent studies. This suggests a lower (time-averaged) mass loss rate and/or a higher ISM density than previously assumed.

astro-ph.SR↗

arXiv2012

CO observations of water-maser post-AGB stars and detection of a high-velocity outflow in IRAS 15452-5459

Many aspects of the evolutionary phase in which Asymptotic Giant Branch stars (AGB stars) are in transition to become Planetary Nebulae (PNe) are still poorly understood. An important question is how the circumstellar envelopes of AGB stars switch from spherical symmetry to the axially symmetric structures frequently observed in PNe. In many cases there is clear evidence that the shaping of the circumstellar envelopes of PNe is linked to the formation of jets/collimated winds and their interaction with the remnant AGB envelope. Because of the short evolutionary time, objects in this phase are rare, but their identification provides valuable probes for testing evolutionary models. We have observed (sub)millimeter CO rotational transitions with the APEX telescope in a small sample of stars hosting high-velocity OH and water masers. These targets are supposed to have recently left the AGB, as indicated by the presence of winds traced by masers, with velocities larger than observed during that phase. We have carried out observations of several CO lines, ranging from J=2-1 up to J=7-6. In IRAS 15452-5459 we detect a fast molecular outflow in the central region of the nebula and estimate a mass-loss rate between 1.2x10^{-4} Msun yr^{-1} (assuming optically thin emission) and 4.9x10^{-4} Msun yr^{-1} (optically thick emission). We model the SED of this target taking advantage of our continuum measurement at 345 GHz to constrain the emission at long wavelengths. For a distance of 2.5 kpc, we estimate a luminosity of 8000 Lsun and a dust mass of 0.01 Msun. Through the flux in the [CII] line (158 um), we calculate a total mass of about 12 Msun for the circumstellar envelope, but the line is likely affected by interstellar contamination.

astro-ph.SR↗

arXiv2011

Strong linear polarization of V4332 Sgr: a dusty disc geometry

The eruption of V4332 Sgr was observed in 1994. During the outburst, the object became extremely red, so it is considered as belonging to luminous red transients of the V838 Mon type. It has recently been suggested that the central object in V4332 Sgr is now hidden in a dusty disc and that the photospheric spectrum of this object observed in the optical results from scattering the central star radiation on dust grains in the disc. One expects significant polarization of the spectrum in this case. We investigate this prediction. We present and analyse polarimetric observations of V4332 Sgr in the V and R photometric bands done with the NOT telescope. The optical light of V4332 Sgr is linearly polarized with a degree of ~26% in the V band and ~11% in R. Discussion of the observed polarization leads us to conclude that the photospheric spectrum observed in V4332 Sgr is probably produced by dust scattering not only in the disc but also in the outflow from the object seen in the emission features.

astro-ph.SR↗

arXiv2010

V4332 Sagittarii: A circumstellar disc obscuring the main object

V4332 Sgr experienced an outburst in 1994 whose observational characteristics in many respects resemble those of the eruption of V838 Mon in 2002. It has been proposed that these objects erupted because of a stellar-merger event. Our aim is to derive, from observational data, information on the present (10-15 yrs after the outburst) nature and structure of the object. We present and analyse a high-resolution (R = 21 000) spectrum of V4332 Sgr obtained with the Subaru Telescope in June 2009. Various components (stellar-like continuum, atomic emission lines, molecular bands in emission) in the spectrum are analysed and discussed. We also investigate a global spectral energy distribution (SED) of the object mostly derived from broadband optical and infrared photometry. The observed continuum resembles that of an M6 giant. The emission features (atomic and molecular) are most probably produced by radiative pumping. The observed strengths of the emission features strongly suggest that we only observe a small part of the radiation of the main object responsible for pumping the emission features. An infrared component seen in the observed SED, which can be roughly approximated by two blackbodies of 950 and 200 K, is 50 times brighter than the M6 stellar component seen in the optical. This further supports the idea that the main object is mostly obscured for us. The main object in V4332 Sgr, an M6 (super)giant, is surrounded by a circumstellar disc, which is seen almost edge-on so the central star is obscured. The observed M6 spectrum probably results from scattering the central star spectrum on dust grains at the outer edge of the disc.

astro-ph.SR↗

arXiv2009

An analysis of a spectrum of V838 Monocerotis in October 2005

V838 Mon erupted at the beginning of 2002. Among various scenarios proposed to explain the nature of the outburst, the most promising is a stellar merger event. The results of spectroscopic observations of the object obtained in October 2005 with the Keck/HIRES instrument, presented in detail in Paper I, are analysed and discussed. Our analysis of the molecular bands and the P-Cyg profiles of atomic lines shows that the object loses matter with a velocity of up to 215 km/s and a rate of 10^{-6} - 10^{-5} M_sun/yr. In the profiles of some atomic lines, we have also found evidence of matter infall. A narrow absorption component, which is particularly strong in some P-Cyg profiles, may indicate that a jet-like outflow has also been formed. We show that the observed emission in the [Fe II] lines and an eclipse-like event observed in November/December 2006 was probably caused by interactions of the expanding matter, ejected by V838 Mon in 2002, with radiation from the B3V companion. In particular, the observed profiles of the [Fe II] lines can be easily modelled in this scenario and allow us to estimate parameters of the system, such as the position of the B3V companion relative to V838 Mon and the line of sight, density in the outflowing matter, and mass lost in the 2002 eruption. The observed appearance of strong H-alpha emission, just before and during the eclipse-like event, can be interpreted as a result of the accretion of the outflowing matter onto the B3V companion: the accreted matter, shocked above the stellar surface, can be a source of extreme-UV and soft X-ray radiation capable of ionizing and exciting H in the outflow.

astro-ph.SR↗

arXiv2007

Observations of V838 Mon in the CO rotational lines

We investigate the structure of a field around the position of V838 Mon as seen in the lowest CO rotational transitions. We also measure and analyse emission in the same lines at the position of V838 Mon.Observations have primarily been done in the CO J = 2-1 and J = 3-2 lines using the KOSMA telescope. A field of 3.4 squared degrees has been mapped in the on-the-fly mode in these transitions. Longer integration spectra in the on-off mode have been obtained to study the emission at the position of V838 Mon. Selected positions in the field have also been observed in the CO J = 1-0 transition using the Delingha telescope.In the observed field we have identified many molecular clouds. They can be divided into two groups from the point of view of their observed radial velocities. One, having V(LSR) in the range 18-32 km/s, can be identified with the Perseus Galactic arm. The other one, having V(LSR) between 44-57 km/s, probably belongs to the Norma-Cygnus arm. The radial velocity of V838 Mon is within the second range but the object does not seem to be related to any of the observed clouds. We did not find any molecular buble of a 1 degree dimension around the position of V838 Mon claimed in van Loon et al. An emission has been detected at the position of the object in the CO J = 2-1 and J = 3-2 transitions. The emission is very narrow (FWHM ~ 1.2 km/s) and at V(LSR) = 53.3 km/s. Our analysis of the data suggests that the emission is probably extended.

astro-ph↗

arXiv2006

Combustion Process in a Spark Ignition Engine: Analysis of Cyclic Maximum Pressure and Peak Pressure Angle

In this paper we analyze the cycle-to-cycle variations of maximum pressure $p_{max}$ and peak pressure angle $α_{pmax}$ in a four-cylinder spark ignition engine. We examine the experimental time series of $p_{max}$ and $α_{pmax}$ for three different spark advance angles. Using standard statistical techniques such as return maps and histograms we show that depending on the spark advance angle, there are significant differences in the fluctuations of $p_{max}$ and $α_{pmax}$. We also calculate the multiscale entropy of the various time series to estimate the effect of randomness in these fluctuations. Finally, we explain how the information on both $p_{max}$ and $α_{pmax}$ can be used to develop optimal strategies for controlling the combustion process and improving engine performance.

nlin.CD↗

arXiv2006

Observations of V838 Mon and the nearby region in the CO J = 1-0, 2-1 and 3-2 transitions

We present observations of V838 Mon and its close vicinity in the three lowest rotational transitions of CO. The J = 2-1 and 3-2 data were obtained using the 3 m KOSMA telescope. They include on-the-fly maps covering a large area (~3.4 sq. deg.) around V838 Mon and long integrations on the star position. Complementary observations in the CO J = 1-0 transition were obtained using the 13.7 m Delingha telescope. The star position as well as 25 other points preselected in the near vicinity of the object have been measured in this transition. We report on a detection of two narrow emission components in J = 2-1 and 3-2 transitions at the position of V838 Mon. Lines were found at radial velocities of V_lsr=53.3 km/s and V_lsr=-11.0 km/s. Their origin is unclear. We also shortly discuss results of the observations of the vicinity of V838 Mon.

astro-ph↗

arXiv2003

Combustion Process in a Spark Ignition Engine: Dynamics and Noise Level Estimation

We analyse the experimental time series of internal pressure in a four cylinder spark ignition engine. In our experiment, performed for different spark advance angles, apart from usual cyclic changes of engine pressure we observed oscillations. These oscillations are with longer time scales ranging from one to several hundred engine cycles depending on engine working conditions. Basing on the pressure time dependence we have calculated the heat released per cycle. Using the time series of heat release to calculate the correlation coarse-grained entropy we estimated the noise level for internal combustion process. Our results show that for a smaller spark advance angle the system is more deterministic.

nlin.CD↗