scholarly journals Discovery of a 310 Day Period from the Enshrouded Massive System NaSt1 (WR 122)

2021 ◽  
Vol 922 (1) ◽  
pp. 5
Author(s):  
Ryan M. Lau ◽  
Samaporn Tinyanont ◽  
Matthew J. Hankins ◽  
Michael C. B. Ashley ◽  
Kishalay De ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Light Curves ◽  
Line Of Sight ◽  
Dust Formation ◽  
Alert System ◽  
Photometric Variability ◽  
The Past ◽  
Imaging Telescope ◽  
Photometric Period ◽  
Ir Light

Abstract We present optical and infrared (IR) light curves of NaSt1, also known as Wolf–Rayet 122, with observations from Palomar Gattini-IR (PGIR), the Zwicky Transient Facility (ZTF), the Katzman Automatic Imaging Telescope, the Asteroid Terrestrial-impact Last Alert System, and the All-Sky Automated Survey for Supernovae (ASAS-SN). We identify a P = 309.7 ± 0.7 day photometric period from the optical and IR light curves that reveal periodic, sinusoidal variability between 2014 July and 2021 July. We also present historical IR light curves taken between 1983 July and 1989 May, which show variability consistent with the period of the present-day light curves. In the past, NaSt1 was brighter in the J band with larger variability amplitudes than the present-day PGIR values, suggesting that NaSt1 exhibits variability on longer (≳decade) timescales. Sinusoidal fits to the recent optical and IR light curves show that the amplitude of NaSt1's variability differs at various wavelengths and also reveal significant phase offsets of 17.0 ± 2.5 day between the ZTF r and PGIR J light curves. We interpret the 310 day photometric period from NaSt1 as the orbital period of an enshrouded massive binary. We suggest that the photometric variability of NaSt1 may arise from variations in the line-of-sight optical depth toward circumstellar optical/IR-emitting regions throughout its orbit due to colliding-wind dust formation. We speculate that past mass transfer in NaSt1 may have been triggered by Roche-lobe overflow (RLOF) during an eruptive phase of an Ofpe/WN9 star. Lastly, we argue that NaSt1 is no longer undergoing RLOF mass transfer.

scholarly journals Optical Light Curves of Supernovae

2005 ◽  
Vol 192 ◽  
pp. 173-182
Author(s):  
Bruno Leibundgut
Keyword(s):  
Light Curve ◽  
Energy Input ◽  
Light Curves ◽  
Line Of Sight ◽  
Spectral Evolution ◽  
The Past

SummaryLight curves are the most readily available and most frequently used astrophysical tools for variable phenomena. Supernovae are no exception to this. The information that can be extracted from detailed light and colors curves, together with the detailed study of the spectral evolution, tells us about the progenitor star, the various energy input sources, the explosion environment, material in the line of sight and cosmological effects. Over the past decade we have come to understand the power of detailed light curve studies and how they tie into the exploration of other astrophysical topics.

scholarly journals FS Aur as a Permanent Superhump System

2004 ◽  
Vol 194 ◽  
pp. 169-171
Author(s):  
Gaghik H. Tovmassian ◽  
Sergei V. Zharikov
Keyword(s):  
Mass Transfer ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Variable Mass ◽  
Accretion Disc ◽  
Light Curves ◽  
Cataclysmic Variable ◽  
Short Period ◽  
Photometric Period ◽  
Low Amplitude

AbstractWe discovered that the short period cataclysmic variable FS Aur at some epochs shows a photometric period close to the orbital. It exceeds the orbital period by ∽2%, which is a sign of the presence of a permanent superhump in the system. Superhumps tend to appear near short, low amplitude outbursts. We assume that FS Aur possesses a large thermally stable accretion disc and that the outburst may be due to the variable mass transfer rate. This, however, does not alter our previous explanation of yet another, 2.4 times longer than orbital, photometric period of FS Aur, found earlier, and persistently observed in its light curves.

scholarly journals An overview of the structure and kinematics of the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 15-23 ◽  
Author(s):  
B. E. Westerlund
Keyword(s):  
Star Formation ◽  
Observational Data ◽  
Spiral Structure ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Line Of Sight ◽  
Small Magellanic Cloud ◽  
Complex Velocity ◽  
The Past

A vast amount of observational data concerning the structure and kinematics of the Magellanic Clouds is now available. Many basic quantities (e.g. distances and geometry) are, however, not yet sufficiently well determined. Interactions between the Small Magellanic Cloud (SMC), the Large Magellanic Cloud (LMC) and our Galaxy have dominated the evolution of the Clouds, causing bursts of star formation which, together with stochastic self-propagating star formation, produced the observed structures. In the youngest generation in the LMC it is seen as an intricate pattern imitating a fragmented spiral structure. In the SMC much of the fragmentation is along the line of sight complicating the reconstruction of its history. The violent events in the past are also recognizable in complex velocity patterns which make the analysis of the kinematics of the Clouds difficult.

scholarly journals Analysis of E.U. Rapid Alert System (RASFF) Notifications for Aflatoxins in Exported U.S. Food and Feed Products for 2010–2019

Toxins ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 90
Author(s):  
Ahmad Alshannaq ◽  
Jae-Hyuk Yu
Keyword(s):  
Animal Feed ◽  
The United States ◽  
Export Market ◽  
The European Union ◽  
Alert System ◽  
Agricultural Export ◽  
The Past ◽  
Pistachio Nuts ◽  
Food And Feed ◽  
Rapid Alert System

The most common, toxic, and carcinogenic mycotoxins found in human food and animal feed are the aflatoxins (AFs). The United States is a leading exporter of various nuts, with a marketing value of $9.1 billion in 2019; the European Union countries are the major importers of U.S. nuts. In the past few years, border rejections and notifications for U.S. tree nuts and peanuts exported to the E.U. countries have increased due to AF contamination. In this work, we analyzed notifications from the “Rapid Alert System for Food and Feed (RASFF)” on U.S. food and feed products contaminated with mycotoxins, primarily AFs, for the 10-year period 2010–2019. Almost 95% of U.S. mycotoxin RASFF notifications were reported for foods and only 5% for feeds. We found that 98.9% of the U.S. food notifications on mycotoxins were due to the AF contamination in almond, peanut, and pistachio nuts. Over half of these notifications (57.9%) were due to total AF levels greater than the FDA action level in food of 20 ng g−1. The Netherlands issued 27% of the AF notifications for U.S. nuts. Border rejection was reported for more than 78% of AF notifications in U.S. nuts. All U.S. feed notifications on mycotoxins occurred due to the AF contamination. Our research contributes to better understanding the main reasons behind RASFF mycotoxins notifications of U.S. food and feed products destined to E.U. countries. Furthermore, we speculate possible causes of this problem and provide a potential solution that could minimize the number of notifications for U.S. agricultural export market.

scholarly journals Small impacts on the giant planet Jupiter

2018 ◽  
Vol 617 ◽  
pp. A68 ◽  
Author(s):  
R. Hueso ◽  
M. Delcroix ◽  
A. Sánchez-Lavega ◽  
S. Pedranghelu ◽  
G. Kernbauer ◽  
...  
Keyword(s):  
Giant Planet ◽  
Interplanetary Dust ◽  
Light Curves ◽  
Dust Particles ◽  
Video Observation ◽  
Interplanetary Dust Particles ◽  
The Past ◽  
Giant Impacts ◽  
The Masses ◽  
The Impact

Context. Video observations of Jupiter obtained by amateur astronomers over the past 8 years have shown five flashes of light with durations of 1–2 s, each observed by at least two observers that were geographically separated. The first three of these events occurred on 3 June 2010, 20 August 2010, and 10 September 2012. Previous analyses of their light curves showed that they were caused by the impact of objects of 5–20 m in diameter, depending on their density, with a released energy comparable to superbolides on Earth of the class of the Chelyabinsk airburst. The most recent two flashes on Jupiter were detected on 17 March 2016 and 26 May 2017 and are analyzed here. Aims. We characterize the energy involved together with the masses and sizes of the objects that produced these flashes. The rate of similar impacts on Jupiter provides improved constraints on the total flux of impacts on the planet, which can be compared to the amount of exogenic species detected in the upper atmosphere of Jupiter. Methods. We extracted light curves of the flashes and calculated the masses and sizes of the impacting objects after calibrating each video observation. We also present results from a systematic search of impacts on >72 000 video amateur observations with a customized software that is based on differential photometry of the images. An examination of the number of amateur observations of Jupiter as a function of time over the past years allows us to interpret the statistics of these impact detections. Results. The cumulative flux of small objects (5–20 m or larger) that impact Jupiter is predicted to be low (10–65 impacts per year), and only a fraction of them are potentially observable from Earth (4–25 observable impacts per year in a perfect survey). These numbers imply that many observers are required to efficiently discover Jupiter impacts. Conclusions. We predict that more impacts will be found in the next years, with Jupiter opposition displaced toward summer in the northern hemisphere where most amateur astronomers observe. Objects of this size contribute negligibly to the abundance of exogenous species and dust in the stratosphere of Jupiter when compared with the continuous flux from interplanetary dust particles punctuated by giant impacts. Flashes of a high enough brightness (comparable at their peak to a +3.3 magnitude star) could produce an observable debris field on the planet. We estimate that a continuous search for these impacts might find these events once every 0.4–2.6 yr.

scholarly journals Collinder 135 and UBC 7: A physical pair of open clusters

2020 ◽  
Vol 642 ◽  
pp. L4
Author(s):  
Dana A. Kovaleva ◽  
Marina Ishchenko ◽  
Ekaterina Postnikova ◽  
Peter Berczik ◽  
Anatoly E. Piskunov ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Observational Evidence ◽  
Open Clusters ◽  
Line Of Sight ◽  
Kinematic Parameters ◽  
Current Line ◽  
Chance Coincidence ◽  
The Past ◽  
Link Type ◽  
Spatial Coordinates

Context. Given the closeness of the two open clusters Collinder 135 and UBC 7 on the sky, we investigate the possibility that the two clusters are physically related. Aims. We aim to recover the present-day stellar membership in the open clusters Cr 135 and UBC 7 (300 pc from the Sun) in order to constrain their kinematic parameters, ages, and masses and to restore their primordial phase space configuration. Methods. The most reliable cluster members are selected with our traditional method modified for the use of Gaia DR2 data. Numerical simulations use the integration of cluster trajectories backwards in time with our original high-order Hermite4 code φ−GRAPE. Results. We constrain the age, spatial coordinates, velocities, radii, and masses of the clusters. We estimate the actual separation of the cluster centres equal to 24 pc. The orbital integration shows that the clusters were much closer in the past if their current line-of-sight velocities are very similar and the total mass is more than seven times larger than the mass of the most reliable members. Conclusions. We conclude that the two clusters Cr 135 and UBC 7 might very well have formed a physical pair based on the observational evidence as well as numerical simulations. The probability of a chance coincidence is only about 2%.

Editorial

2008 ◽  
Vol 7 (3) ◽  
pp. 106-106
Author(s):  
Chris Roseveare ◽  
Keyword(s):  
Case Reports ◽  
Coding System ◽  
Alert System ◽  
The Past ◽  
Cerebral Nocardiosis ◽  
Irritable Bowel ◽  
Lateral Thinking ◽  
Difficult Times ◽  
To Receive ◽  
Better Than

There is no doubt that this Winter has been tough for those of us working in Acute Medical Units. At the time of writing I find myself in the depths of the post-Christmas blues; the combination of Bank Holidays, ward closures, junior doctor illness and huge admission surges have conspired to make January even more challenging than normal. No doubt the printing delays will have meant that, by the time you are reading this Editorial, these days will be a distant memory. Maybe this will serve as a useful reminder of the need for forward planning in time for next year, rather than breathing the usual sigh of relief as we steel ourselves for Easter. Perhaps a more imaginative colour coding system for our ‘alert’ system would be a start – simply alternating between ‘red alert’ (awful) and ‘black alert’ (even worse) can become quite tedious as the weeks pass. A few shades of maroon or magenta to remind us that ‘today is slightly better than yesterday’ might help break the monotony. We could even opt for a full rainbow spectrum to signify the hope that one day all of our efforts will be worthwhile….it’s important to stay positive in these difficult times! I frequently tell our students ‘When you hear hooves, think horses…not zebras’ – an alternative (and unoriginal) way to remind them that ‘common things occur commonly’. But of course not all chest pain is ischaemic in origin, and not every fever is caused by pneumonia – even in January. The case reports in this edition illustrate some of the more unusual causes of acute medical admission, and the importance of maintaining an open mind. Takotsubo cardiomyopathy is a condition which seems to have passed me by in my medical practice to-date; on reading this case I wondered how many patients I have inappropriately thrombolysed over the past 15 years. In the new world of Heart Attack Centres and urgent percutaneous intervention maybe we will find it is more common than was previously thought. Porphyrias and vasculitidies are occasionally sent to challenge us, but give us the opportunity to demonstrate the power of lateral thinking which distinguishes us as Physicians. As the authors remind us in their title – porphyria will only be diagnosed if it is considered in the differential; it is easy forget that the combination of psychiatric illness and abdominal pain does not always imply Irritable Bowel Syndrome! Cerebral Nocardiosis should not feature high up in the differential diagnosis when a 90 year old patient presents with a hemiparesis, even in the context of immune deficiency. The temptation to presume that the ‘ring enhancing lesion’ seen on his CT was neoplastic, must have been considerable for the team caring for this patient. The importance of a tissue diagnosis, even in this age group, is emphasised by the outcome of this case. I hope you enjoy this edition and hopefully we are now getting back on track with the scheduling. Please keep the submissions coming in; we are starting to receive some interesting pieces of research, which will be included over the next year pending review. If any more readers would like to volunteer to become editorial referees for future editions, please feel free to contact me directly on the email shown.

scholarly journals Profile Changes in the Binary Pulsar PSR 1913+16

1992 ◽  
Vol 128 ◽  
pp. 214-216
Author(s):  
J. M. Weisberg ◽  
J. H. Taylor
Keyword(s):  
General Relativity ◽  
Flux Density ◽  
Spin Axis ◽  
Line Of Sight ◽  
Emission Region ◽  
Pulse Profile ◽  
Pulsar Emission ◽  
Binary Pulsar ◽  
The Past ◽  
Profile Changes

AbstractAccording to general relativity, the spin axis of binary pulsar PSR 1913+16 should precess at a rate of 1.21 degrees per year. This precession will cause the pulse profile to change as our line of sight samples different pulsar latitudes. In order to search for this phenomenon, we have carefully monitored the pulse profile at 1408 MHz for 8.5 years. The ratio of flux density of the first to second pulse component has declined at a rate of approximately 1.65% per year, with some evidence of a steeper decrease over the past three years. We have detected no evidence for a change in the separation of the two components. We discuss the nature of the pulsar emission region in light of these results.

scholarly journals A flare in the optical spotted in the changing-look Seyfert NGC 3516

2020 ◽  
Vol 638 ◽  
pp. A13 ◽  
Author(s):  
D. Ilić ◽  
V. Oknyansky ◽  
L. Č. Popović ◽  
S. S. Tsygankov ◽  
A. A. Belinski ◽  
...  
Keyword(s):  
Maximum Amplitude ◽  
Light Curves ◽  
Continuum Emission ◽  
X Ray ◽  
The Past ◽  
Broad Component ◽  
High Ionization ◽  
Balmer Lines ◽  
Activity State ◽  
Low Activity

Context. We present observations from the short-term intensive optical campaign (from September 2019 to January 2020) of the changing-look Seyfert NGC 3516. This active galactic nucleus is known to have strong optical variability and has changed its type in the past. It has been in the low-activity state in the optical since 2013, with some rebrightening from the end of 2015 to the beginning of 2016, after which it remained dormant. Aims. We aim to study the photometric and spectral variability of NGC 3516 from the new observations in U- and B-bands and examine the profiles of the optical broad emission lines in order to demonstrate that this object may be entering a new state of activity. Methods. NGC 3516 has been monitored intensively for the past 4 months with an automated telescope in U and B filters, enabling accurate photometry of 0.01 precision. Spectral observations were triggered when an increase in brightness was spotted. We support our analysis of past-episodes of violent variability with the UV and X-ray long-term light curves constructed from the archival Swift/UVOT and Swift/XRT data. Results. An increase of the photometric magnitude is seen in both U and B filters to a maximum amplitude of 0.25 mag and 0.11 mag, respectively. During the flare, we observe stronger forbidden high-ionization iron lines ([Fe VII] and [Fe X]) than reported before, as well as the complex broad Hα and Hβ lines. This is especially seen in Hα, which appears to be double-peaked. It seems that a very broad component of ∼10 000 km s−1 in width in the Balmer lines is appearing. The trends in the optical, UV, and X-ray light curves are similar, with the amplitudes of variability being significantly larger in the case of UV and X-ray bands. Conclusions. The increase of the continuum emission, the variability of the coronal lines, and the very broad component in the Balmer lines may indicate that the AGN of NGC 3516 is finally leaving the low-activity state in which it has been for the last ∼3 years.

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