Twelve type II-P supernovae seen with the eyes of Spitzer

Core-collapse supernovae (CC SNe), especially those of type II-plateau (II-P), are thought to be important contributors to cosmic dust production. The most obvious indicator of the presence of newly-formed and/or pre-existing dust is the time-dependent mid-infrared (MIR) excess coming from the environment of SNe. Our goal was to collect publicly available, previously unpublished measurements on type II-P (or peculiar IIP) SNe from the Spitzer database. The temporal changes of the observed fluxes may be indicative of the underlying supernova, while spectral energy distribution (SED) fitting to the fluxes in different IRAC channels may reveal the physical parameters of the mid-IR radiation, presumably due to warm dust. IRS spectra were extracted and calibrated with SPICE, while photometric SEDs were assembled using IRAF and MOPEX. Calculated SEDs from observed fluxes were fit with simple dust models to get basic information on the dust presumed as the source of MIR radiation. We found twelve SNe satisfying the criterion above, observed at late-time epochs (typically after +300 days). In three cases we could not identify any point source at the SN position on late time IRAC images. We found two SNe, 2005ad and 2005af, which likely have newly-formed dust in their environment, while in the other seven cases the observed MIR flux may originate from pre-existing circumstellar or interstellar dust. Our results support the previous observational conclusions that warm new dust in the environment of SNe contributes only marginally to cosmic dust content.Comment: Accepted for publication in Astronomy and Astrophysics; 15 pages, 8 figures, 9 tables (Ver. 2.: language edited version, minor corrections were made in the title, in the text, and in the reference list

The contact binary VW Cephei revisited: surface activity and period variation

Context. Despite the fact that VW Cephei is one of the well-studied contact binaries in the literature, there is no fully consistent model available that can explain every observed property of this system. Aims. Our motivation is to obtain new spectra along with photometric measurements, to analyze what kind of changes may have happened in the system in the past two decades, and to propose new ideas for explaining them. Methods. For the period analysis we determined 10 new times of minima from our light curves, and constructed a new O$-$C diagram of the system. Radial velocities of the components were determined using the cross-correlation technique. The light curves and radial velocities were modelled simultaneously with the PHOEBE code. All observed spectra were compared to synthetic spectra and equivalent widths of the H$\alpha$ line were measured on their differences. Results. We have re-determined the physical parameters of the system according to our new light curve and spectral models. We confirm that the primary component is more active than the secondary, and there is a correlation between spottedness and the chromospheric activity. We propose that flip-flop phenomenon occurring on the primary component could be a possible explanation of the observed nature of the activity. To explain the period variation of VW Cep, we test two previously suggested scenarios: presence of a fourth body in the system, and the Applegate-mechanism caused by periodic magnetic activity. We conclude that although none of these mechanisms can be ruled out entirely, the available data suggest that mass transfer with a slowly decreasing rate gives the most likely explanation for the period variation of VW Cep.Comment: 13 pages, 18 figures, 9 tables, accepted for publication in Astronomy and Astrophysic

Mass and orbit constraints of the gamma-ray binary LS 5039

We present the results of space-based photometric and ground-based spectroscopic observing campaigns on the gamma-ray binary LS 5039. The new orbital and physical parameters of the system are similar to former results, except we found a lower eccentricity. Our MOST-data show that any broad-band optical photometric variability at the orbital period is below the 2 mmag level. Light curve simulations support the lower value of eccentricity and imply that the mass of the compact object is higher than 1.8 solar masses.Comment: 2 pages, 1 figure (with 2 panels); to be published in the Proceedings: From Interacting Binaries to Exoplanets: Essential Modeling Tools, IAU Symposium 282 (18-22 July, 2011, Tatranska Lomnica, Slovakia

Discovery of the spectroscopic binary nature of three bright southern Cepheids

We present an analysis of spectroscopic radial velocity and photometric data of three bright Galactic Cepheids: LR Trianguli Australis (LR TrA), RZ Velorum (RZ Vel), and BG Velorum (BG Vel). Based on new radial velocity data, these Cepheids have been found to be members of spectroscopic binary systems. The ratio of the peak-to-peak radial velocity amplitude to photometric amplitude indicates the presence of a companion for LR TrA and BG Vel. IUE spectra indicate that the companions of RZ Vel and BG Vel cannot be hot stars. The analysis of all available photometric data revealed that the pulsation period of RZ Vel and BG Vel varies monotonically, due to stellar evolution. Moreover, the longest period Cepheid in this sample, RZ Vel, shows period fluctuations superimposed on the monotonic period increase. The light-time effect interpretation of the observed pattern needs long-term photometric monitoring of this Cepheid. The pulsation period of LR TrA has remained constant since the discovery of its brightness variation. Using statistical data, it is also shown that a large number of spectroscopic binaries still remain to be discovered among bright classical Cepheids.Comment: 9 pages, 14 figure

Searching for the expelled hydrogen envelope in Type I supernovae via late-time H-alpha emission

We report the first results from our long-term observational survey aimed at discovering late-time interaction between the ejecta of hydrogen-poor Type I supernovae and the hydrogen-rich envelope expelled from the progenitor star several decades/centuries before explosion. The expelled envelope, moving with a velocity of ~10 -- 100 km s$^{-1}$, is expected to be caught up by the fast-moving SN ejecta several years/decades after explosion depending on the history of the mass-loss process acting in the progenitor star prior to explosion. The collision between the SN ejecta and the circumstellar envelope results in net emission in the Balmer-lines, especially in H-alpha. We look for signs of late-time H-alpha emission in older Type Ia/Ibc/IIb SNe having hydrogen-poor ejecta, via narrow-band imaging. Continuum-subtracted H-alpha emission has been detected for 13 point sources: 9 SN Ibc, 1 SN IIb and 3 SN Ia events. Thirty-eight SN sites were observed on at least two epochs, from which three objects (SN 1985F, SN 2005kl, SN 2012fh) showed significant temporal variation in the strength of their H-alpha emission in our DIAFI data. This suggests that the variable emission is probably not due to nearby H II regions unassociated with the SN, and hence is an important additional hint that ejecta-CSM interaction may take place in these systems. Moreover, we successfully detected the late-time H-alpha emission from the Type Ib SN 2014C, which was recently discovered as a strongly interacting SN in various (radio, infrared, optical and X-ray) bands.Comment: 8 pages, 7 figures, accepted in Ap

A mikrokörnyezeti hatások szerepe a felvehető nyomelem-tartalmának alakításában

Kisebb és nagyobb folyóinkon számos esetben vonultak le megemelkedett nehézfém koncentrációval együtt járó szennyező hullámok. A nehézfém szennyezések sok esetben árhullámokhoz köthetőek, de (főleg kisebb vízfolyásokon) előfordultak kifejezetten közepes (esetleg kis) vízálláshoz, illetve vízhozamhoz köthető szennyezések is. A vízhez, mint transzmissziós közeghez köthető szennyezések esetében a nehézfémek többféle fizikai és formában lehetnek jelen. Az ártérre kikerülő nehézfémek térbeli eloszlása, valamint felhalmozódásuk mértéke a vízállásnak, a szennyezőanyagok fizikai és kémiai formáinak, legvégül pedig az árterek térszerkezetének a függvénye. A nehézfémek által okozott környezeti kockázatot azonban nem önmagában e toxikus hatású elemek abszolút mennyisége jelenti, hanem azok „elérhetősége”. (Elérhetőség alatt ez esetben a fémek remobilizációját és felvehetőségét („bio-elérhetősége”) értjük. Jelen publikációnkban két nagyobb folyónk árterei példáján kíséreltük meg a Cd, Co, Cr, Cu, Ni, Pb és a Zn elérhetőségében mutatkozó különbségek okait feltárni

Discovery of the spectroscopic binary nature of six southern Cepheids

We present the analysis of photometric and spectroscopic data of six bright Galactic Cepheids: GH Carinae, V419 Centauri, V898 Centauri, AD Puppis, AY Sagittarii, and ST Velorum. Based on new radial velocity data (in some cases supplemented with earlier data available in the literature), these Cepheids have been found to be members in spectroscopic binary systems. V898 Cen turned out to have one of the largest orbital radial velocity amplitude (> 40 km/s) among the known binary Cepheids. The data are insufficient to determine the orbital periods nor other orbital elements for these new spectroscopic binaries. These discoveries corroborate the statement on the high frequency of occurrence of binaries among the classical Cepheids, a fact to be taken into account when calibrating the period-luminosity relationship for Cepheids. We have also compiled all available photometric data that revealed that the pulsation period of AD Pup, the longest period Cepheid in this sample, is continuously increasing with Delta P = 0.004567 d/century, likely to be caused by stellar evolution. The wave-like pattern superimposed on the parabolic O-C graph of AD Pup may well be caused by the light-time effect in the binary system. ST Vel also pulsates with a continuously increasing period. The other four Cepheids are characterised with stable pulsation periods in the last half century.Comment: accepted by the MNRAS, 11 pages, 16 figures, 18 tables, a part of the data can be downloaded from the online version of this articl

InSight Aerothermal Environment Assessment

The Mars Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) spacecraft, which successfully touched down on the planet surface on November 26, 2018, was proposed as a near build-to-print copy of the Mars Phoenix vehicle to reduce the overall cost and risk of the mission. Since the lander payload and the atmospheric entry trajectory were similar enough to those of the Phoenix mission, it was expected that the Phoenix thermal protection material thickness would be sufficient to withstand the entry heat load. However, allowances were made for increasing the heatshield thickness because the planned spacecraft arrival date coincided with the Mars dust storm season. The aftbody Thermal Protection System (TPS) components were not expected to change. In a first for a US Mars mission, the aerothermal environments for InSight included estimates of radiative heat flux to the aftbody from the wake. The combined convective and radiative heat fluxes were used to determine if the as-flown Phoenix thermal protection system (TPS) design would be sufficient for InSight. Although the radiative heat fluxes on the aftbody were predicted to be comparable to, or even higher than the local convective heat fluxes, all analyses of the aftbody TPS showed that the design would still be adequate. Aerothermal environments were computed for the vehicle from post-flight reconstruction of the atmosphere and trajectory and compared with the design environments. These comparisons showed that the predicted as-flown conditions were less severe than the design conditions

A study of orientational ordering in a fluid of dipolar Gay-Berne molecules using density-functional theory

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