The Carnegie Supernova Project II. Observations of the luminous red nova AT 2014ej
M. D. Stritzinger, F. Taddia, M. Fraser, T. M. Tauris, C. Contreras, S Drybye, L. Galbany, S. Holmbo, N. Morrell, A. Pastorello, M. M. Phillips, G. Pignata, L. … 展开作者
M. D. Stritzinger, F. Taddia, M. Fraser, T. M. Tauris, C. Contreras, S Drybye, L. Galbany, S. Holmbo, N. Morrell, A. Pastorello, M. M. Phillips, G. Pignata, L. Tartaglia, N. B. Suntzeff, J. Anais, C. Ashall, E. Baron, C. R. Burns, P. Hoeflich, E. Y. Hsiao, E. Karamehmetoglu, T. J. Moriya, G. Bock, A. Campillay, S. Castellon, C. Inserra, C. Gonzalez, P. Marples, S. Parker, D. Reichart, S. Torres-Robledo, D. R. Young
备注：
Paper 2 of a series of 2 papers. Replaced to match the version published on A&A. 8 pages of text, 15 figures, 10 tables
We present optical and near-infrared broadband photometry and optical spectra of AT 2014ej from the the Carnegie Supernova Project-II. These observations are complemented with data from the CHilean Automatic Supernova sEarch, the Public ESO Spectroscopic Survey of Transient Objects, and from the Backyard Observatory Supernova Search. Observational signatures of AT 2014ej reveal that it is similar to other members of the gap-transient subclass known as luminous red novae (LRNe), including the ubiquitous double hump light curve and spectral properties akin to the LRN SN 2017jfs. A medium-dispersion, visual-wavelength spectrum of AT 2014ej taken the Magellan Clay telescope, exhibits a P Cygni H$α$ feature characterized by a blue velocity at zero intensity of $\approx 110$ km s$^{-1}$ and a P Cygni minimum velocity of $\approx70$ km s$^{-1}$, and which we attribute to emission from a circumstellar wind. Inspection of pre-outbust Hubble Space Telescope images yields no conclusive progenitor detection. In comparison with a sample of LRNe from the literature, AT 2014ej lies among the brighter end of the luminosity distribution. Comparison of the ultra-violet, optical, infrared (UVOIR) light curves of well-observed LRNe to common-envelope evolution models from the literature, indicates the models under predict the luminosity of the comparison sample at all phases and also produce inconsistent time-scales of the secondary peak. Future efforts to model LRNe should expand upon the current parameter space explored and therefore may consider more massive systems and a wider range of dynamical timescales.
We present observations of the unusual optical transient SN 2010U, including spectra taken 1.03 days to 15.3 days after maximum light that identify it as a fast and luminous Fe II type nova. Our multi-band light curve traces the fast decline (t_2 = 3.5 days) from maximum light (M_V = -10.2 mag), placing SN 2010U in the top 0.5% of the most luminous novae ever observed. We find typical ejecta velocities of approximately 1100 km/s and that SN 2010U shares many spectral and photometric characteristics with two other fast and luminous Fe II type novae, including Nova LMC 1991 and M31N-2007-11d. Fo…
We present the $H$-band wavelength region of thirty post-maximum light near-infrared (NIR) spectra of fourteen transitional and sub-luminous type Ia supernovae (SNe Ia), extending from $+$5d to +20d relative to the epoch of $B$-band maximum. We introduce a new observable, the blue-edge velocity, $v_{edge}$, of the prominent Fe/Co/Ni-peak $H$-band emission feature which is quantitatively measured. The $v_{edge}$ parameter is found to slowly decrease over sub-type ranging from around $-$13,000km/s for transitional SNe~Ia, down to $-$5,000km/s for the sub-luminous SNe Ia. Furthermore, inspection …
Nova Sagittarii 1943 (V1148 Sgr) was an 8th-mag optical transient that was unusual in having a late-type spectrum during its outburst, in striking contrast to the normal high-excitation spectra seen in classical novae. Unfortunately, only an approximate position was given in the discovery announcement, hampering follow-up attempts to observe its remnant. We have identified the nova on two photographic plates in the Harvard archive, allowing us to determine a precise astrometric position. Apart from these two plates, obtained in 1943 and 1944, none of the photographs in the Harvard collection, …
It has recently been discovered that some, if not all, classical novae emit GeV gamma rays during outburst, but the mechanisms involved in the production of the gamma rays are still not well understood. We present here a comprehensive multi-wavelength dataset---from radio to X-rays---for the most gamma-ray luminous classical nova to-date, V1324 Sco. Using this dataset, we show that V1324 Sco is a canonical dusty Fe-II type nova, with a maximum ejecta velocity of 2600 km s$^{-1}$ and an ejecta mass of few $\times 10^{-5}$ M$_{\odot}$. There is also evidence for complex shock interactions, inclu…
Exploring stellar evolution with Luminous Red Novae and Interacting Gap Transients
Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona (UB)（巴塞罗那大学宇宙科学研究所）；Departament de Física Quàntica i Astrofísica (FQA), Universitat de Barcelona (UB)（巴塞罗那大学量子物理与天体物理学系）；Institut d’Estudis Espacials de Catalunya (IEEC)（加泰罗尼亚空间研究院）
We present multi-wavelength observations of two gap transients followed by the Carnegie Supernova Project-II and supplemented with data obtained by a number of different programs. Here in the first of two papers, we focus on the intermediate luminosity red transient (ILRT) designated SNhunt120, while in a companion paper we examine the luminous red novae AT 2014ej. Our data set for SNhunt120 consists of an early optical discovery, estimated to be within 3 days after outburst, the subsequent optical and near-infrared broadband followup extending over a $\sim$2 month period, two visual- and two …
Recent observational surveys have uncovered the existence of super-luminous supernovae (SLSNe). While several possible explanations have been put forth, a consensus description for SLSNe has yet to be found. In this work we study the light curves of eight SLSNe in the context of dual-shock quark novae. We find that progenitor stars in the range of 25-35 $M_{\sun}$ provide ample energy to power each light curve. An examination into the effects of varying the physical properties of a dual-shock quark nova on light curve composition is undertaken. We conclude that the wide variety of SLSN light c…
Luminous red novae (LRN) are a class of optical transients believed to originate from the mergers of binary stars, or "common envelope" events. Their light curves often show secondary maxima, which cannot be explained in the previous models of thermal energy diffusion or hydrogen recombination without invoking multiple independent shell ejections. We propose that double-peaked light curves are a natural consequence of a collision between dynamically-ejected fast shell and pre-existing equatorially-focused material, which was shed from the binary over many orbits preceding the dynamical event. …
We present the discovery of a rapidly evolving transient by the Korean Microlensing Telescope Network Supernova Program (KSP). KSP is a novel high-cadence supernova survey that offers deep ($\sim21.5$ mag in $BVI$ bands) nearly continuous wide-field monitoring for the discovery of early and/or fast optical transients. KSP-OT-201509a, reported here, was discovered on 2015 September 27 during the KSP commissioning run in the direction of the nearby galaxy NGC~300, and stayed above detection limit for $\sim$ 22 days. We use our $BVI$ light-curves to constrain the ascent rate, $-3.7(7)$ mag day$^{…
The process of unstable mass transfer in a stellar binary can result in either a complete merger of the stars or successful removal of the donor envelope leaving a surviving more compact binary. "Luminous red nova" (LRN) are the class of optical transients believed to accompany such merger/common envelope events. Past works typically model LRNe using analytic formulae for supernova light curves which make assumptions (e.g., radiation dominated ejecta, neglect of hydrogen recombination energy) not justified in stellar mergers due to the lower velocities and specific thermal energy of the ejecta…
A class of optical transients known as Luminous Red Novae (LRNe) have recently been associated with mass ejections from binary stars undergoing common-envelope evolution. We use the population synthesis code COMPAS to explore the impact of a range of assumptions about the physics of common-envelope evolution on the properties of LRNe. In particular, we investigate the influence of various models for the energetics of LRNe on the expected event rate and light curve characteristics, and compare with the existing sample. We find that the Galactic rate of LRNe is $\sim 0.2$ yr$^{-1}$, in agreement…
We report the discovery and multicolor (VRIW) photometry of a rare explosive star MASTER OT J004207.99+405501.1 - a luminous red nova - in the Andromeda galaxy M31N2015-01a. We use our original light curve acquired with identical MASTER Global Robotic Net telescopes in one photometric system: VRI during first 30 days and W (unfiltered) during 70 days. Also we added publishied multicolor photometry data to estimate the mass and energy of the ejected shell, and discuss the likely formation scenarios of outbursts of this type. We propose the interpretation of the explosion, that is consistent wit…
We report on the Fermi-LAT detection (with ~5.7 sigma significance) as well as the multi-wavelength analysis of the 2017 nova eruption V549 Vel. Unlike the recent shock-powered novae ASASSN-16ma and V906 Car, the optical and gamma-ray light curves of V549 Vel show no correlation, likely implying relatively weak shocks in the eruption. Gaia detected a candidate progenitor of V549 Vel and found a parallax measurement of 1.91+/-0.39 mas, equivalent to a mode distance of d=560 pc (90% credible interval of 380-1050 pc). The progenitor was also observed by the 2MASS and WISE surveys. When adopting t…
We examine four high resolution reflection grating spectrometers (RGS) spectra of the February 2009 outburst of the luminous recurrent nova LMC 2009a. They were very complex and rich in intricate absorption and emission features. The continuum was consistent with a dominant component originating in the atmosphere of a shell burning white dwarf (WD) with peak effective temperature between 810,000 K and a million K, and mass in the 1.2-1.4 M$_\odot$ range. A moderate blue shift of the absorption features of a few hundred km s$^{-1}$ can be explained with a residual nova wind depleting the WD sur…
The Landscape of Unstable Mass Transfer in Interacting Binaries and Its Imprint on the Population of Luminous Red Novae
University of California, Santa Cruz（加州大学圣克鲁兹分校）；Niels Bohr International Academy, Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯·玻尔研究所、尼尔斯·玻尔国际学院）；Center for Astrophysics, Harvard & Smithsonian（哈佛-史密森天体物理中心）；Institute for Theory and Computation, Harvard & Smithsonian（哈佛-史密森理论计算研究所）
Luminous Red Novae as shock-powered transients I: Electron-scattering wings and deviations from Case B
Cosmic Dawn Center (DAWN)（宇宙黎明中心）；Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯玻尔研究所）；Research Center for the Early Universe, Graduate School of Science, The University of Tokyo（东京大学理学研究科早期宇宙研究中心）；Astronomical Institute, Tohoku University（东北大学天文学研究所）
SNe II show great photometric and spectroscopic diversity which is attributed to the varied physical characteristics of their progenitor and explosion properties. In this study, the third of a series of papers where we analyse a sample of SNe II observed by the Carnegie Supernova Project-I, we present correlations between their observed and physical properties. Our analysis shows that explosion energy is the physical property that correlates with the highest number of parameters. We recover previously suggested relationships between the hydrogen-rich envelope mass and the plateau duration, and…
Super-luminous supernova (SLSN) are supernovae showing extreme properties in their light-curves: high peak luminosities (more than 10 times brighter than bright SN Ia), and long durations. Several mechanisms have been proposed for SLSN, such as pair instability SN of a massive progenitor, interaction of the ejecta with a massive circumstellar shell, and the dual-shock quark nova (dsQN) model. The dual-shock quark nova model is unique in that it predicts a normal SN event will be seen about 10 days prior to the main SLSN event. The dsQN model is described here and shown that it is consistent wi…
We present a multi-wavelength photometric and spectroscopic analysis of thirteen "Super-Chandrasekhar Mass"/2003fg-like type Ia Supernova (SNe~Ia). Nine of these objects were observed by the Carnegie Supernova Project. 2003fg-like have slowly declining light curves ($Δm_{15}$(B) $<$1.3 mag), and peak absolute $B$-band magnitudes between $-19<M_{B}<-21$~mag. Many 2003fg-like are located in the same part of the luminosity width relation as normal SNe~Ia. In the optical $B$ and $V$ bands, 2003fg-like look like normal SNe~Ia, but at redder wavelengths they diverge. Unlike other luminous SNe~Ia, 20…
We present ultra-violet to mid-infrared observations of the long-lasting Type IIn supernova (SN) 2013L obtained by the Carnegie Supernova Project II (CSP-II). The spectra of SN 2013L are dominated by H emission features characterized by three components attributed to different regions. A unique feature of this Type IIn SN is that the blue shifted line profile is dominated by the macroscopic velocity of the expanding shock wave of the SN. We are therefore able to trace the evolution of the shock velocity in the dense and partially opaque circumstellar medium (CSM), from $\sim 4800~km~s^{-1}$ at…
We present the observation of an extraordinary luminous soft X-ray transient, MAXI J0158-744, by the Monitor of All-sky X-ray Image (MAXI) on 2011 November 11. This transient is characterized by a soft X-ray spectrum, a short duration (1.3 x 10^3 s < ΔT_d < 1.10 x 10^4 s), a very rapid rise (< 5.5 x 10^3 s), and a huge peak luminosity of 2 x 10^40 erg s^-1 in 0.7-7.0 keV band. With Swift observations and optical spectroscopy from the Small and Moderate Aperture Research Telescope System (SMARTS), we confirmed that the transient is a nova explosion, on a white dwarf in a binary with a Be star, …
SN2006oz is a super-luminous supernova with a mysterious bright precursor that has resisted explanation in standard models. However, such a precursor has been predicted in the dual-shock quark nova (dsQN) model of super-luminous supernovae -- the precursor is the SN event while the main light curve of the SLSN is powered by the Quark-Nova (QN; explosive transition of the neutron star to a quark star). As the SN is fading, the QN re-energizes the SN ejecta, producing a "double-humped" light curve. In this paper, we show the dsQN model successfully reproduces the observed light curve of SN2006oz…
Comparative Study of Two Luminous Red Novae I. Progenitor Modeling and Dust Formation
Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona (UB)（巴塞罗那大学宇宙科学研究所）；Departament de Física Quàntica i Astrofísica (FQA), Universitat de Barcelona (UB)（巴塞罗那大学量子物理与天体物理学系）；Institut d’Estudis Espacials de Catalunya (IEEC)（加泰罗尼亚空间研究院）；Department of Astrophysics/IMAPP, Radboud University（拉德堡德大学天体物理学/IMAPP系）
We show that appealing to a Quark-Nova (QN) in a tight binary system containing a massive neutron star and a CO white dwarf (WD), a Type Ia explosion could occur. The QN ejecta collides with the WD driving a shock that triggers Carbon burning under degenerate conditions (the QN-Ia). The conditions in the compressed low-mass WD (M_WD < 0.9M_sun) in our model mimics those of a Chandrasekhar mass WD. The spin-down luminosity from the QN compact remnant (the quark star) provides additional power that makes the QN-Ia light-curve brighter and broader than a standard SN-Ia with similar 56Ni yield. In…
The Palomar Transient Factory (PTF) is systematically charting the optical transient and variable sky. A primary science driver of PTF is building a complete inventory of transients in the local Universe (distance less than 200 Mpc). Here, we report the discovery of PTF10fqs, a transient in the luminosity "gap" between novae and supernovae. Located on a spiral arm of Messier 99, PTF 10fqs has a peak luminosity of Mr = -12.3, red color (g-r = 1.0) and is slowly evolving (decayed by 1 mag in 68 days). It has a spectrum dominated by intermediate-width H (930 km/s) and narrow calcium emission line…
We present extensive datasets for a class of intermediate-luminosity optical transients known as "luminous red novae" (LRNe). They show double-peaked light curves, with an initial rapid luminosity rise to a blue peak (at -13 to -15 mag), which is followed by a longer-duration red peak that sometimes is attenuated, resembling a plateau. The progenitors of three of them (NGC4490-2011OT1, M101-2015OT1, and SNhunt248), likely relatively massive blue to yellow stars, were also observed in a pre-eruptive stage when their luminosity was slowly increasing. Early spectra obtained during the first peak …
We present a study of observed Type II supernova (SN~II) colours using optical/near-infrared photometric data from the \textit{Carnegie Supernovae Project-I}. We analyse four colours ($B-V$, $u-g$, $g-r$, and $g-Y$) and find that SN~II colour curves can be described by two linear regimes during the photospheric phase. The first ($s_{\rm 1,colour}$) is steeper and has a median duration of $\sim 40$ days. The second, shallower slope ($s_{\rm 2,colour}$) lasts until the end of the "plateau" ($\sim 80$ days). The two slopes correlate in the sense that steeper initial colour curves also imply steep…
We present Suzaku XIS observation of V2491 Cyg (Nova Cyg 2008 No. 2) obtained in quiescence, more than two years after the outburst. The nova was detected as a very luminous source in a wide spectral range from soft to hard X-rays. A very soft blackbody-like component peaking at 0.5 keV indicates that either we observe remaining, localized hydrogen burning on the surface of the white dwarf, or accretion onto a magnetized polar cap. In the second case, V2491 Cyg is a candidate "soft intermediate polar". We obtained the best fit for the X-ray spectra with several components: two of thermal plasm…
1991T-like supernovae are the luminous, slow-declining extreme of the Branch shallow-silicon (SS) subclass of Type Ia supernovae. They are distinguished by extremely weak Ca II H & K and Si II $\lambda6355$ and strong Fe III absorption features in their optical spectra at pre-maximum phases, and have long been suspected to be over-luminous compared to normal Type Ia supernovae. In this paper, the pseudo equivalent width of the Si II $λ$6355 absorption obtained at light curve phases from $\leq+10$ days is combined with the morphology of the $i$-band light curve to identify a sample of 1991T-lik…
In the last 20 years, modern wide-field surveys discovered a new class of peculiar transients, which lie in the luminosity gap between standard supernovae and classical novae. These transients are often called 'intermediate luminosity optical transients' or 'gap transients'. They are usually distinguished in subgroups based on their phenomenology, such as supernova impostors, intermediate luminosity red transients, and luminous red novae. In this review, we present a brief overview of their observational features and possible physical scenarios to date, in the attempt to understand their natur…
We present an observational study of the luminous red nova (LRN) AT\,2021biy in the nearby galaxy NGC\,4631. The field of the object was routinely imaged during the pre-eruptive stage by synoptic surveys, but the transient was detected only at a few epochs from $\sim 231$\,days before maximum brightness. The LRN outburst was monitored with unprecedented cadence both photometrically and spectroscopically. AT\,2021biy shows a short-duration blue peak, with a bolometric luminosity of $\sim 1.6 \times 10^{41}$\,erg\,s$^{-1}$, followed by the longest plateau among LRNe to date, with a duration of 2…
A discussion regarding the progenitor system of the nova and dwarf nova system V392 Persei using archival data from 2MASS and WISE. We find that the system is unlikely to contain a luminous red giant donor (i.e. a symbiotic system), but cannot exclude the presence of a lower luminosity red giant or a sub-giant donor. The similarity of the SED of the quiescent V392 Per to that of GK Persei is noted.
Nova SMC 2016 has been the most luminous nova known in the direction of the Magellanic Clouds. It turned into a very luminous supersoft X-ray source between day 16 and 28 after the optical maximum. We observed it with Chandra, the HRC-S camera and the Low Energy Transmission Grating (LETG) on 2016 November and 2017 January (days 39 and 88 after optical maximum), and with XMM-Newton on 2016 December (day 75). We detected the compact white dwarf (WD) spectrum as a luminous supersoft X-ray continuum with deep absorption features of carbon, nitrogen, magnesium, calcium, probably argon and sulfur o…
The Type Ia supernova (SN Ia) LSQ14fmg exhibits exaggerated properties which may help to reveal the origin of the "super-Chandrasekhar" (or 03fg-like) group. The optical spectrum is typical of a 03fg-like SN Ia, but the light curves are unlike those of any SNe Ia observed. The light curves of LSQ14fmg rise extremely slowly. At -23 rest-frame days relative to B-band maximum, LSQ14fmg is already brighter than $M_V$=-19 mag before host extinction correction. The observed color curves show a flat evolution from the earliest observation to approximately one week after maximum. The near-infrared lig…
What do gravitational-wave observations tell us about Luminous Red Novae?
Aryabhatta Research Institute of Observational Sciences (ARIES)（阿亚巴塔观测科学研究所）；Department of Applied Physics, Mahatma Jyotibha Phule Rohilkhand University（马哈特玛·乔蒂巴·普勒罗希尔坎德大学应用物理系）；Inter-University Centre for Astronomy and Astrophysics（大学间天文学与天体物理学中心）；Institute for Gravitational Wave Astronomy and School of Physics and Astronomy, University of Birmingham（伯明翰大学引力波天文台及物理与天文学学院）；Bareilly College, Mahatma Jyotibha Phule Rohilkhand University（马哈特玛·乔蒂巴·普勒罗希尔坎德大学巴雷利学院）；Chennai Mathematical Institute（金奈数学研究所）
Aims: AT 2018hso is a new transient showing transitional properties between those of LRNe and the class of intermediate luminosity red transients (ILRTs) similar to SN 2008S. Through the detailed analysis of the observed parameters, our study support that it actually belongs to the LRN class, and was likely produced by the coalescence of two massive stars. Methods: We obtained ten months of optical and near-infrared photometric monitoring, and eleven epochs of low-resolution optical spectroscopy of AT~2018hso. We compared its observed properties with those of other ILRTs and LRNe. We also insp…
Type Ia supernovae have proven vital to our understanding of cosmology, both as standard candles and for their role in galactic chemical evolution; however, their origin remains uncertain. The canonical accretion model implies a hot and luminous progenitor which would ionize the surrounding gas out to a radius of $\sim$10--100 parsecs for $\sim$100,000 years after the explosion. Here we report stringent upper limits on the temperature and luminosity of the progenitor of Tycho's supernova (SN 1572), determined using the remnant itself as a probe of its environment. Hot, luminous progenitors tha…
Nova LMC 2009a is confirmed as a Recurrent Nova (RN) from positional coincidence with nova LMC 1971b. The observational data set is one of the most comprehensive for any Galactic or extragalactic RN: optical and near-IR photometry from outburst until over 6 years later; optical spectra for the first 6 months, and Swift satellite Ultraviolet and X-ray observations from 9 days to almost 1 year post-outburst. We find $M_V = -8.4\pm0.8_{\mathrm{r}}\pm0.7_{\mathrm{s}}$ and expansion velocities between 1000 and 4000 km s$^{-1}$. Coronal line emission before day 9 indicates shocks in the ejecta. Stre…
The extremely luminous supernova 2006gy (SN 2006gy) is among the most energetic ever observed. The peak brightness was 100 times that of a typical supernova and it spent an unheard of 250 days at magnitude -19 or brighter. Efforts to describe SN 2006gy have pushed the boundaries of current supernova theory. In this work we aspire to simultaneously reproduce the photometric and spectroscopic observations of SN 2006gy using a quark nova model. This analysis considers the supernova explosion of a massive star followed days later by the quark nova detonation of a neutron star. We lay out a detaile…
We present medium-resolution spectroscopy and multicolor photometry for the optical transient PSN J09093496+3307204 (SN 2015bh) in the galaxy NGC 2770, which has transferred into the supernova phase. The observations were carried out between February 2015 to May 2016. Both at the phase of the SN impostor (2015a) and at the supernova phase (2015b), besides Balmer emissions, the strong Fe II emissions are seen in the spectrum; so, these spectra resemble those of Williams Fe II type classical novae. The star is located near the edge of a dark nebula and notably absorbed (Av = 1.14 +/-0.15 mag). T…
We investigate the mechanism to reproduce notable spectral features at the ignition phase of nova explosion observed for a super-Eddington X-ray transient source MAXI J0158$-$744 in the Small Magellanic Cloud. These are a strong Ne IX emission line at 0.92 keV with a large equivalent width of $0.32^{+0.21}_{-0.11}$ keV and the absence of Ne X line at 1.02 keV. In this paper, we calculate the radiative transfer using a Monte Carlo code, taking into account the line blanketing effect due to transitions of N, O, Ne, Mg and Al ions in an accelerating wind emanating from a white dwarf with a struct…
Type-Iax supernovae (SN Iax) are stellar explosions that are spectroscopically similar to some type-Ia supernovae (SN Ia) at maximum light, except with lower ejecta velocities. They are also distinguished by lower luminosities. At late times, their spectroscopic properties diverge from other SN, but their composition (dominated by iron-group and intermediate-mass elements) suggests a physical connection to normal SN Ia. These are not rare; SN Iax occur at a rate between 5 and 30% of the normal SN Ia rate. The leading models for SN Iax are thermonuclear explosions of accreting carbon-oxygen whi…
The fast recurrent nova V745 Sco was observed in the 3-79 keV X-rays band with NuSTAR 10 days after the optical discovery. The measured X-ray emission is consistent with a collisionally ionized optically thin plasma at temperature of about 2.7 keV. A prominent iron line observed at 6.7 keV does not require enhanced iron in the ejecta. We attribute the X-ray flux to shocked circumstellar material. No X-ray emission was observed at energies above 20 keV, and the flux in the 3-20 keV range was about 1.6 $\times$ 10$^{-11}$ erg cm$^{-2}$ s$^{-1}$. The emission measure indicates an average electron…
We analyse here four observations of nova KT Eri (Nova Eri 2009) done with the Chandra High Resolution Camera Spectrometer (HRC-S) and the Low Energy Transmission Grating (LETG) in 2010, from day 71 until day 159 after the optical maximum, in the luminous supersoft X-ray phase. The spectrum presents many absorption features with a large range of velocity, from a few hundred km s$^{-1}$ to 3100 km s$^{-1}$ in the same observation, and a few prominent emission features, generally redshifted by more than 2000 km s$^{-1}$. Although the uncertainty on the distance and the WD luminosity from the app…
We study mass loss from the outer Lagrange point (L2) in binary stellar mergers and their luminous transients by means of radiative hydrodynamical simulations. Previously, we showed that for binary mass ratios 0.06 < q < 0.8, synchronous L2 mass loss results in a radiatively inefficient, dust-forming unbound equatorial outflow. A similar outflow exists irrespective of q if the ratio of the sound speed to the orbital speed at the injection point is sufficiently large, ε= c_T/v_orb > 0.15. By contrast, for cold L2 mass-loss (ε< 0.15) from binaries with q < 0.06 or q > 0.8, the equatorial outflow…
We report the detection of an infrared selected transient which has lasted at least 5 years, first identified by a large mid-infrared and optical outburst from a faint X-ray source detected with the Chandra X-ray Observatory. In this paper we rule out several scenarios for the cause of this outburst, including a classical nova, a luminous red nova, AGN flaring, a stellar merger, and intermediate luminosity optical transients, and interpret this transient as the result of a Young Stellar Object (YSO) of at least solar mass accreting material from the remains of the dusty envelope from which it …
We performed a wide-area (2000 deg$^{2}$) g and I band experiment as part of a two month extension to the Intermediate Palomar Transient Factory. We discovered 36 extragalactic transients including iPTF17lf, a highly reddened local SN Ia, iPTF17bkj, a new member of the rare class of transitional Ibn/IIn supernovae, and iPTF17be, a candidate luminous blue variable outburst. We do not detect any luminous red novae and place an upper limit on their rate. We show that adding a slow-cadence I band component to upcoming surveys such as the Zwicky Transient Facility will improve the photometric selec…
We searched optical/UV/IR counterparts of seven supersoft X-ray sources (SSS) in M31 in the Hubble Space Telescope (HST) "Panchromatic Hubble Andromeda Treasury" (PHAT) archival images and photometric catalog. Three of the SSS were transient, the other four are persistent sources. The PHAT offers the opportunity to identify SSS hosting very massive white dwarfs that may explode as type Ia supernovae in single degenerate binaries, with magnitudes and color indexes typical of symbiotic stars, high mass close binaries, or systems with optically luminous accretion disks. We find evidence that the …
Shock interaction has been argued to play a role in powering a range of optical transients, including supernovae (particularly the superluminous class), classical novae, stellar mergers, tidal disruption events, and fast blue optical transients. These same shocks can accelerate relativistic ions, generating high-energy neutrino and gamma-ray emission via hadronic pion production. The recent discovery of time-correlated optical and gamma-ray emission in classical novae has revealed the important role of radiative shocks in powering these events, enabling an unprecedented view of the properties …
[Abridged] By appealing to a Quark-Nova (QN; the explosive transition of a neutron star to a quark star) in the wake of a core-collapse Supernova explosion of a massive star, we develop a unified model for long duration Gamma-ray Bursts (LGRBs) and Fast Radio Bursts (FRBs). The time delay (years to decades) between the SN and the QN and, the fragmented nature (i.e. millions of chunks) of the relativistic QN ejecta are key to yielding a robust LGRB engine. In our model, a LGRB light-curve exhibits the interaction of the fragmented QN ejecta with a turbulent (i.e. filamentary and magnetically sa…
IPHAS J190812.63+045728.1: A deeply eclipsing, X-ray bright cataclysmic variable with frequent outbursts
Universidade Federal de Sergipe（塞尔希培联邦大学）；Observatório Nacional（国家天文台）；Laboratório Nacional de Astrofísica（国家天体物理实验室）；NASA/GSFC（美国宇航局戈达德太空飞行中心）；University of Maryland, Baltimore County（马里兰大学巴尔的摩县分校）；Instituto Nacional de Pesquisas Espaciais（国家空间研究所）
We provide additional observational evidence that some Type Ia supernovae (SNe Ia) show signatures of circumstellar interaction (CSI) with hydrogen-rich material. Early phase optical and near-infrared (NIR) light curves and spectroscopy of SN 2008J obtained by the Carnegie Supernova Project are studied and compared to those of SNe 2002ic and 2005gj. Our NIR spectrum is the first obtained for a 2002ic-like object extending up to 2.2 $μ$m. A published high-resolution spectrum is used to provide insight on the circumstellar material (CSM). SN 2008J is found to be affected by $A_V\sim$ 1.9 mag of …
We present a systematic study of the most luminous ($M_{\mathrm{IR}}$ [Vega magnitudes] brighter than $-14$) infrared (IR) transients discovered by the SPitzer InfraRed Intensive Transients Survey (SPIRITS) between 2014 and 2018 in nearby galaxies ($D < 35$ Mpc). The sample consists of nine events that span peak IR luminosities of $M_{[4.5],\mathrm{peak}}$ between $-14$ and $-18.2$, show IR colors between $0.2 < ([3.6]{-}[4.5]) < 3.0$, and fade on timescales between $55$ days $< t_{\mathrm{fade}} < 480$ days. The two reddest events ($A_V > 12$) show multiple, luminous IR outbursts over several…
