Observations and analysis of two type IIP supernovae: the intrinsically faint object SN 2005cs and the ambiguous object SN 2005ay

Aims: To derive observational properties and physical parameters of the progenitor stars of type IIP supernovae SN 2005ay and SN 2005cs from their U,B,V,R,I CCD photometry, and to define their velocity behaviour. Methods: Light curves are analysed, and the velocities and spectral characteristics of SN 2005cs are obtained using synthetic spectra modeling. Results: Both supernovae are found to be fainter than the average SN IIP, with SN 2005cs being more subluminous and showing slight brightening in the second half of plateau stage in the V,R,I bands and a low expansion velocity. The effects of two different plausible distance moduli on the derived physical parameters of SN 2005ay are considered. Two approaches are used to recover the amounts of the ejected 56Ni, indicating masses of the order of 0.02 Msun, although late luminosities might indicate a higher amount for SN 2005ay, especially for the large distance case. Constraints on the progenitor properties are also presented, based on empirical analytical models. Two approaches are used to estimate the expansion velocities at the middle of the plateau phase. SN 2005cs represents an example of where all 3 physical parameters, velocity, energy and 56Ni mass are lower than average, a correlation not always observed in SNe IIP. SN 2005ay may belong to the same class if the shorter distance possibility is adopted. Furthermore, the estimated mass range for SN 2005cs is in agreement with limits established by using pre-supernova imaging.Comment: 8 pages, 6 figures, to be published in A&A vol.460, issue 3, December 200

Дослідження протигерпетичної активності похідних амінопропанолу-2.

Introduction. Chemotherapy and chemoprophylaxis are some of the main and often the only possible ways to effective control of viral infections. Therefore, the study of antiviral properties of new substances with the known chemical structure is one of the main ways to create new antiviral agents.The aim of the study – to research the antiherpes activity of new aminopropanol-2 derivatives against the herpes simplex virus (HSV) antigenic type 1, strain VC.Research Methods. Antiherpes activity was determined in 8 aminopropanol-2 derivatives: norbornyl containing substance (compound No. 51), substance with cyclic substituents in alkoxi group (compound No. 48), substances with alicyclic substituents in alkoxi group (compounds No. 46, 47, 49, 50, 52 and 53). Evaluation of antiherpes activity of the studied compounds was performed in vitro on cell culture VNK (growing culture of hamster kidney). Ability to reduce of virus infectious titer and chemotherapeutic index (HTI) of the studied compounds was determined.Results and Discussion. It is established that the compound No. 53 inhibits HSV-I reproduction in 2 lg ID50 at a concentration of 1.56 µg/ml. HTI of compound No. 53 is equal to 64, which describes it as an effective inhibitor of HSV-I reproduction. Some antiherpes action in compounds No. 46, 47 and 51 was identified also, their HTI were 8, 4 and 4 respectively. Substances No. 48, 49, 50 and 52 do not show  the antiherpes action.Conclusions. Among all tested aminopropanol-2 derivatives the compound No. 53 with clear antiherpes properties was determined. Compound No. 53 belongs to the substances with alicyclic substituents in alkoxi group and has such chemical formula: 1-(2-methyl-3-butinox)-3-(2.2.6.6-tetramethyl piperidine)-2-propanol hydrochloride. Compound No. 53 as alicyclic substituent in alkoxy group contains 2-methyl-3-butene, and amine moiety of this substance contains the radical 2.2.6.6 – tetramethylpiperidine. The obtained results will be useful in establishing the natural relationships "structure-activity", also it can be used to create active compounds with certain characteristics.Вступление. В связи с тем, что химиотерапия и химиопрофилактика являются одними из главных, а часто и единственно возможными средствами эффективной борьбы с вирусными инфекциями, исследование соединений нового синтеза с известной формулой на предмет выявления их противовирусных свойств остается одним из основных направлений при создании новых противовирусных препаратов. Цель исследования – изучить противогерпетическую активность новых соединений аминопропанола-2 в отношении вируса герпеса простого (HSV)1-го антигенного типа, штамм VC.Методы исследования. Определяли противогерпетическое действие 8 производных аминопропанола-2, среди которых вещество № 51 относилось к норборнилсодержащим соединениям, вещество № 48 – к соединениям с циклическими заместителями в алкоксигруппе, вещества № 46, 47, 49, 50, 52 и 53 относились к соединениям  с алициклическими заместителями в алкоксигруппе. Противогерпетическую активность исследуемых веществ оценивали in vitro на культуре клеток ВНК (перевиваемая культура клеток почки хомяка) по снижению инфекционного титра вируса и путем определения их химиотерапевтического индекса (ХТИ).Результаты и обсуждение. Установлено, что вещество № 53 угнетает репродукцию вируса HSV-I на 2 lg ID50 в концентрации 1,56 мкг/мл, а ХТИ этого соединения равняется 64, что характеризует его как эффективный ингибитор репродукции HSV-I. Также выявлено незначительную противогерпетическую активность веществ № 46, 47 и 51, о чем свидетельствуют показатели их ХТИ (8, 4 и 4 соответственно). Вещества № 48, 49, 50 и 52 не имеют противогерпетического действия.Выводы. Среди исследованных производных аминопропанола-2 идентифицировано соединение 1-(2-метил-3-бутинокси)-3-(2,2,6,6-тетраметил пиперидино)-2-пропанол гидрохлорид (вещество № 53), которое проявляет выраженое противогерпетическое действие. По химической структуре вещество № 53 относится к группе соединений с алициклическими заместителями в алкоксигруппе, где алициклическим заместителем является 2-метил-3-бутен, а аминный фрагмент этого вещества содержит радикал 2,2,6,6-тетраметилпиперидин. Полученные результаты будут полезны при установлении закономерных взаимосвязей “структура – активность” и могут быть  использованы при создании активных соединений с определенными характеристикамиВступ. З огляду на те, що хіміотерапія та хіміопрофілактика є одними з головних,  а часто і єдино можливими засобами ефективної боротьби з вірусними інфекціями, дослідження сполук нового синтезу з відомою формулою стосовно виявлення їх противірусних властивостей залишається одним з основних шляхів створення нових противірусних препаратів.Мета дослідження – вивчити протигерпетичну активність нових сполук амінопропанолу-2 відносно вірусу простого герпесу (HSV) 1-го антигенного типу, штам VC.Методи дослідження. Визначали дію протигерпетичну у 8 похідних амінопропанолу-2, серед яких сполука № 51 належала до норборніловмісних речовин, сполука № 48 – до речовин із циклічними замісниками в алкоксигрупі, сполуки № 46, 47, 49, 50, 52 і 53 належали до речовин   з аліциклічними замісниками в алкоксигрупі. Протигерпетичну активність досліджуваних речовин оцінювали in vitro на культурі  клітин ВНК (перещеплювана культура клітин нирки хом’яка) за зниженням інфекційного титру вірусу та шляхом визначення їх хіміотерапевтичного індексу (ХТІ). Результати й обговорення. Встановлено, що сполука № 53 пригнічує репродукцію вірусу HSV-I на 2 lg ID50 в концентрації 1,56 мкг/мл, а ХТІ цієї речовини дорівнює 64, що характеризує її як  ефективний інгібітор репродукції HSV-I. Також виявлено деяку протигерпетичну сполук № 46, 47 та 51, про що свідчать показники їх ХТІ (8, 4 і 4 відповідно). Речовини № 48, 49, 50 та 52 не мають протигерпетичної дії.Висновки. Серед досліджених похідних амінопропанолу-2 ідентифіковано сполуку 1-(2-метил-3-бутинокси)-3-(2,2,6,6-тетраметил піперидино)-2-пропанол гідрохлорид (сполука № 53), що проявляє виражену протигерпетичну дію. За хімічною структурою сполука № 53 належить до групи речовин з аліциклічними замісниками в алкоксигрупі, де аліциклічним замісником є 2-метил-3-бутен, а амінний фрагмент цієї речовини містить радикал 2,2,6,6-тетраметилпіперидин. Отримані результати будуть корисними при встановленні закономірних взаємозв’язків “структура – активність” та можуть бути використані при створенні активних сполук  з певними характеристиками.

Comparative performance of selected variability detection techniques in photometric time series

Photometric measurements are prone to systematic errors presenting a challenge to low-amplitude variability detection. In search for a general-purpose variability detection technique able to recover a broad range of variability types including currently unknown ones, we test 18 statistical characteristics quantifying scatter and/or correlation between brightness measurements. We compare their performance in identifying variable objects in seven time series data sets obtained with telescopes ranging in size from a telephoto lens to 1m-class and probing variability on time-scales from minutes to decades. The test data sets together include lightcurves of 127539 objects, among them 1251 variable stars of various types and represent a range of observing conditions often found in ground-based variability surveys. The real data are complemented by simulations. We propose a combination of two indices that together recover a broad range of variability types from photometric data characterized by a wide variety of sampling patterns, photometric accuracies, and percentages of outlier measurements. The first index is the interquartile range (IQR) of magnitude measurements, sensitive to variability irrespective of a time-scale and resistant to outliers. It can be complemented by the ratio of the lightcurve variance to the mean square successive difference, 1/h, which is efficient in detecting variability on time-scales longer than the typical time interval between observations. Variable objects have larger 1/h and/or IQR values than non-variable objects of similar brightness. Another approach to variability detection is to combine many variability indices using principal component analysis. We present 124 previously unknown variable stars found in the test data.Comment: 29 pages, 8 figures, 7 tables; accepted to MNRAS; for additional plots, see http://scan.sai.msu.ru/~kirx/var_idx_paper

Inflows, Outflows, and a Giant Donor in the Remarkable Recurrent Nova M31N 2008-12a? - Hubble Space Telescope Photometry of the 2015 Eruption

The recurrent nova M31N 2008-12a experiences annual eruptions, contains a near-Chandrasekhar mass white dwarf, and has the largest mass accretion rate in any nova system. In this paper, we present Hubble Space Telescope (HST) WFC3/UVIS photometry of the late decline of the 2015 eruption. We couple these new data with archival HST observations of the quiescent system and Keck spectroscopy of the 2014 eruption. The late-time photometry reveals a rapid decline to a minimum luminosity state, before a possible recovery / re-brightening in the run-up to the next eruption. Comparison with accretion disk models supports the survival of the accretion disk during the eruptions, and uncovers a quiescent disk mass accretion rate of the order of $10^{-6}\,M_\odot\,\mathrm{yr}^{-1}$, which may rise beyond $10^{-5}\,M_\odot\,\mathrm{yr}^{-1}$ during the super-soft source phase - both of which could be problematic for a number of well-established nova eruption models. Such large accretion rates, close to the Eddington limit, might be expected to be accompanied by additional mass loss from the disk through a wind and even collimated outflows. The archival HST observations, combined with the disk modeling, provide the first constraints on the mass donor; $L_\mathrm{donor}=103^{+12}_{-11}\,L_\odot$, $R_\mathrm{donor}=14.14^{+0.46}_{-0.47}\,R_\odot$, and $T_\mathrm{eff, donor}=4890\pm110$ K, which may be consistent with an irradiated M31 red-clump star. Such a donor would require a system orbital period $\gtrsim5$ days. Our updated analysis predicts that the M31N 2008-12a WD could reach the Chandrasekhar mass in < 20 kyr

M31N 2008-12a - the remarkable recurrent nova in M31: Pan-chromatic observations of the 2015 eruption

The Andromeda Galaxy recurrent nova M31N 2008-12a had been observed in eruption ten times, including yearly eruptions from 2008-2014. With a measured recurrence period of $P_\mathrm{rec}=351\pm13$ days (we believe the true value to be half of this) and a white dwarf very close to the Chandrasekhar limit, M31N 2008-12a has become the leading pre-explosion supernova type Ia progenitor candidate. Following multi-wavelength follow-up observations of the 2013 and 2014 eruptions, we initiated a campaign to ensure early detection of the predicted 2015 eruption, which triggered ambitious ground and space-based follow-up programs. In this paper we present the 2015 detection; visible to near-infrared photometry and visible spectroscopy; and ultraviolet and X-ray observations from the Swift observatory. The LCOGT 2m (Hawaii) discovered the 2015 eruption, estimated to have commenced at Aug. $28.28\pm0.12$ UT. The 2013-2015 eruptions are remarkably similar at all wavelengths. New early spectroscopic observations reveal short-lived emission from material with velocities $\sim13000$ km s$^{-1}$, possibly collimated outflows. Photometric and spectroscopic observations of the eruption provide strong evidence supporting a red giant donor. An apparently stochastic variability during the early super-soft X-ray phase was comparable in amplitude and duration to past eruptions, but the 2013 and 2015 eruptions show evidence of a brief flux dip during this phase. The multi-eruption Swift/XRT spectra show tentative evidence of high-ionization emission lines above a high-temperature continuum. Following Henze et al. (2015a), the updated recurrence period based on all known eruptions is $P_\mathrm{rec}=174\pm10$ d, and we expect the next eruption of M31N 2008-12a to occur around mid-Sep. 2016

Breaking the habit - the peculiar 2016 eruption of the unique recurrent nova M31N 2008-12a

Since its discovery in 2008, the Andromeda galaxy nova M31N 2008-12a has been observed in eruption every single year. This unprecedented frequency indicates an extreme object, with a massive white dwarf and a high accretion rate, which is the most promising candidate for the single-degenerate progenitor of a type-Ia supernova known to date. The previous three eruptions of M31N 2008-12a have displayed remarkably homogeneous multi-wavelength properties: (i) From a faint peak, the optical light curve declined rapidly by two magnitudes in less than two days; (ii) Early spectra showed initial high velocities that slowed down significantly within days and displayed clear He/N lines throughout; (iii) The supersoft X-ray source (SSS) phase of the nova began extremely early, six days after eruption, and only lasted for about two weeks. In contrast, the peculiar 2016 eruption was clearly different. Here we report (i) the considerable delay in the 2016 eruption date, (ii) the significantly shorter SSS phase, and (iii) the brighter optical peak magnitude (with a hitherto unobserved cusp shape). Early theoretical models suggest that these three different effects can be consistently understood as caused by a lower quiescence mass-accretion rate. The corresponding higher ignition mass caused a brighter peak in the free-free emission model. The less-massive accretion disk experienced greater disruption, consequently delaying re-establishment of effective accretion. Without the early refueling, the SSS phase was shortened. Observing the next few eruptions will determine whether the properties of the 2016 outburst make it a genuine outlier in the evolution of M31N 2008-12a

An accreting white dwarf near the Chandrasekhar limit in the andromeda galaxy

The intermediate Palomar Transient Factory (iPTF) detection of the most recent outburst of the recurrent nova (RN) system RX J0045.4+4154 in the Andromeda galaxy has enabled the unprecedented study of a massive (M > 1.3 M) accreting white dwarf (WD). We detected this nova as part of the near-daily iPTF monitoring of M31 to a depth of R 21 mag and triggered optical photometry, spectroscopy and soft X-ray monitoring of the outburst. Peaking at an absolute magnitude of MR= -6.6 mag, and with a decay time of 1 mag per day, it is a faint and very fast nova. It shows optical emission lines of He/N and expansion velocities of 1900-2600 km s-1 1-4 days after the optical peak. The Swift monitoring of the X-ray evolution revealed a supersoft source (SSS) with kT eff 90-110 eV that appeared within 5 days after the optical peak, and lasted only 12 days. Most remarkably, this is not the first event from this system, rather it is an RN with a time between outbursts of approximately 1 yr, the shortest known. Recurrent X-ray emission from this binary was detected by ROSAT in 1992 and 1993, and the source was well characterized as a M > 1.3 M WD SSS. Based on the observed recurrence time between different outbursts, the duration and effective temperature of the SS phase, MESA models of accreting WDs allow us to constrain the accretion rate to and WD mass >1.30 M. If the WD keeps 30% of the accreted material, it will take less than a Myr to reach core densities high enough for carbon ignition (if made of C/O) or electron capture (if made of O/Ne) to end the binary evolution. © 2014. The American Astronomical Society. All rights reserved.