scholarly journals CRTS J035010.7 + 323230, a new eclipsing polar in the cataclysmic variable period gap

2019 ◽  
Vol 488 (2) ◽  
pp. 2881-2891 ◽  
Author(s):  
Paul A Mason ◽  
Natalie K Wells ◽  
Mokhine Motsoaledi ◽  
Paula Szkody ◽  
Emmanuel Gonzalez
Keyword(s):  
Light Curve ◽  
White Dwarf ◽  
Spectral Energy Distribution ◽  
Semimajor Axis ◽  
Spectral Energy ◽  
Cataclysmic Variable ◽  
Show Evidence ◽  
Optical Light Curve ◽  
Photometric Monitoring ◽  
Orbital Cycle

ABSTRACT We report the discovery of a new eclipsing polar, CRTS J035010.7+323230 (hereafter CRTS J0350+3232). We identified this cataclysmic variable (CV) candidate as a possible polar from its multiyear Catalina Real-Time Transient Survey (CRTS) optical light curve. Photometric monitoring of 22 eclipses in 2015 and 2017 was performed with the 2.1-m Otto Struve Telescope at McDonald Observatory. We derive an unambiguous high-precision ephemeris. Strong evidence that CRTS J0350 + 3232 is a polar comes from optical spectroscopy obtained over a complete orbital cycle using the Apache Point Observatory 3.5-m telescope. High velocity Balmer and He ii λ4686Å emission-line equivalent width ratios, structures, and variations are typical of polars and are modulated at the same period, 2.37 h (142.3 min), as the eclipse to within uncertainties. The spectral energy distribution and luminosity is found to be comparable to that of AM Herculis. Pre-eclipse dips in the light curve show evidence for stream accretion. We derive the following tentative binary and stellar parameters assuming a helium composition white dwarf and a companion mass of 0.2 M⊙: inclination i  = 74.68° ± 0.03°, semimajor axis a  = 0.942 ± 0.024 R⊙, and masses and radii of the white dwarf and companion, respectively: M1  = 0.948 $^{+0.006}_{-0.012}$ M⊙, R1  = 0.00830 $^{+0.00012}_{-0.00006}$ R⊙, and R2  = 0.249 ± 0.002 R⊙. As a relatively bright (V ∼ 17–19 mag), eclipsing, period-gap polar, CRTS J0350 + 3232 will remain an important laboratory for the study of accretion and angular momentum evolution in polars.

scholarly journals Results of 5-year photometric monitoring of the intermediate polar V2306 Cygni: correction of the orbital period and evidence of 2-day periodicity

2015 ◽  
Vol 5 (1) ◽  
pp. 17-20
Author(s):  
V. Breus ◽  
K. Petrík ◽  
S. Zoła ◽  
A. Baransky ◽  
T. Hegedus
Keyword(s):  
Light Curve ◽  
Accretion Disk ◽  
Orbital Period ◽  
White Dwarf ◽  
Cataclysmic Variable ◽  
Firm Conclusion ◽  
Spin Period ◽  
Photometric Monitoring

We present the results of 6 years of photometric monitoring of the magnetic cataclysmic variable V2306 Cygni (formerly known as 1WGAJ1958.2+3232) obtained at collaborating observatories. Using (O-C) analysis we tried to study variability of the spin period of the white dwarf, however we cannot make a firm conclusion based on the scatter. Simultaneously, using (O-C) diagram of orbital minima, we found that the value of 0.181545(3) days better corresponds with the light curve, than do previously published orbital period values. We also found that the variability has a 2.01 day period; this variability may be interpreted as possible precession of the accretion disk in this system.

scholarly journals Significant luminosity differences of two twin Type Ia supernovae

2019 ◽  
Vol 491 (4) ◽  
pp. 5991-5999 ◽  
Author(s):  
Ryan J Foley ◽  
Samantha L Hoffmann ◽  
Lucas M Macri ◽  
Adam G Riess ◽  
Peter J Brown ◽  
...  
Keyword(s):  
Light Curve ◽  
Spectral Energy Distribution ◽  
Cosmological Parameters ◽  
Spectral Energy ◽  
Type Ia Supernovae ◽  
Curve Shape ◽  
Type Ia ◽  
Optical Light Curve ◽  
Ia Supernovae ◽  
Peak Luminosity

ABSTRACT The Type Ia supernovae (SNe Ia) 2011by, hosted in NGC 3972, and 2011fe, hosted in M101, are optical ‘twins,’ having almost identical optical light-curve shapes, colours, and near-maximum-brightness spectra. However, SN 2011fe had significantly more ultraviolet (UV; 1600 < λ < 2500 Å) flux than SN 2011by before and at peak luminosity. Several theoretical models predict that SNe Ia with higher progenitor metallicity should (1) have additional UV opacity and thus lower UV flux; (2) have an essentially unchanged optical spectral-energy distribution; (3) have a similar optical light-curve shape; and (4) because of the excess neutrons, produce more stable Fe-group elements at the expense of radioactive 56Ni and thus have a lower peak luminosity. Following these predictions, Foley and Kirshner suggested that the difference in UV flux between SNe 2011by and 2011fe was the result of their progenitors having significantly different metallicities. They also measured a large, but insignificant, difference between the peak absolute magnitudes of the SNe (ΔMV, peak = 0.60 ± 0.36 mag), with SN 2011fe being more luminous. We present a new Cepheid-based distance to NGC 3972, substantially improving the precision of the distance measurement for SN 2011by. With these new data, we determine that the SNe have significantly different peak luminosities (ΔMV, peak = 0.335 ± 0.069 mag). Consequently, SN 2011fe produced 38 per cent more 56Ni than SN 2011by, consistent with predictions for progenitor metallicity differences for these SNe, although alternative models may also explain this difference. We discuss how progenitor metallicity differences can contribute to the intrinsic scatter for light-curve-shape-corrected SN luminosities, the use of ‘twin’ SNe for measuring distances, and implications for using SNe Ia for constraining cosmological parameters.

scholarly journals Far-infrared photometry of OJ 287 with the Herschel Space Observatory

2018 ◽  
Vol 610 ◽  
pp. A74
Author(s):  
Mark Kidger ◽  
Staszek Zola ◽  
Mauri Valtonen ◽  
Anne Lähteenmäki ◽  
Emilia Järvelä ◽  
...  
Keyword(s):  
Energy Distribution ◽  
Light Curve ◽  
Spectral Index ◽  
Spectral Energy Distribution ◽  
Low Frequency ◽  
Far Infrared ◽  
Small Degree ◽  
Spectral Energy ◽  
Space Observatory ◽  
Near Ir

Context. The blazar OJ 287 has shown a ≈12 year quasi-periodicity over more than a century, in addition to the common properties of violent variability in all frequency ranges. It is the strongest known candidate to have a binary singularity in its central engine. Aim. We aim to better understand the different emission components by searching for correlated variability in the flux over four decades of frequency measurements. Methods. We combined data at frequencies from the millimetric to the visible to characterise the multifrequency light curve in April and May 2010. This includes the only photometric observations of OJ 287 made with the Herschel Space Observatory: five epochs of data obtained over 33 days at 250, 350, and 500 μm with Herschel-SPIRE. Results. Although we find that the variability at 37 GHz on timescales of a few weeks correlates with the visible to near-IR spectral energy distribution, there is a small degree of reddening in the continuum at lower flux levels that is revealed by the decreasing rate of decline in the light curve at lower frequencies. However, we see no clear evidence that a rapid flare detected in the light curve during our monitoring in the visible to near-IR light curve is seen either in the Herschel data or at 37 GHz, suggesting a low-frequency cut-off in the spectrum of such flares. Conclusions.We see only marginal evidence of variability in the observations with Herschel over a month, although this may be principally due to the poor sampling. The spectral energy distribution between 37 GHz and the visible can be characterised by two components of approximately constant spectral index: a visible to far-IR component of spectral index α = −0.95, and a far-IR to millimetric spectral index of α = −0.43. There is no evidence of an excess of emission that would be consistent with the 60 μmdust bump found in many active galactic nuclei.

scholarly journals Broad-band spectral energy distribution of the X-ray transient Swift J1745−26 from outburst to quiescence

2020 ◽  
Vol 637 ◽  
pp. A2
Author(s):  
Sylvain Chaty ◽  
Francis Fortin ◽  
Alicia López-Oramas
Keyword(s):  
Energy Distribution ◽  
Light Curve ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Spectral Energy ◽  
X Ray ◽  
Upper Limit ◽  
Spectral Break ◽  
Hard State ◽  
Low Mass

Aims. We aim to analyse our study of the X-ray transient Swift J1745−26, using observations obtained from its outburst in September 2012, up to its decay towards quiescence in March 2013. Methods. We obtained optical and infrared observations, through override programme at ESO/VLT with FORS2 and ISAAC instruments, and added archival optical (VLT/VIRCAM), radio and X-ray (Swift) observations, to build the light curve and the broad-band spectral energy distribution (SED) of Swift J1745−26. Results. We show that, during its outburst and also during its decay towards quiescence, Swift J1745−26 SED can be adjusted, from infrared up to X-rays, by the sum of both a viscous irradiated multi-colour black body emitted by an accretion disc, and a synchrotron power law at high energy. In the radio domain, the SED arises from synchrotron emission from the jet. While our SED fitting confirms that the source remained in the low/hard state during its outburst, we determine an X-ray spectral break at frequency 3.1 ≤ νbreak ≤ 3.4 × 1014 Hz, and a radio spectral break at 1012 Hz ≤ νbreak ≤ 1013 Hz. We also show that the system is compatible with an absorption AV of ∼7.69 mag, lies within a distance interval of D ∼ [2.6 − 4.8] kpc with an upper limit of orbital period Porb = 11.3 h, and that the companion star is a late spectral type in the range K0–M0 V, confirming that the system is a low-mass X-ray binary. We finally plot the position of Swift J1745−26 on an optical-infrared – X-ray luminosity diagram: its localisation on this diagram is consistent with the source staying in the low-hard state during outburst and decay phases. Conclusions. By using new observations obtained at ESO/VLT with FORS2 and ISAAC, and adding archival optical (VLT/VIRCAM), radio and X-ray (Swift) observations, we built the light curve and the broad-band SED of Swift J1745−26, and we plotted its position on an optical-infrared – X-ray luminosity diagram. By fitting the SED, we characterized the emission of the source from infrared, via optical, up to X-ray domain, we determined the position of both the radio and X-ray spectral breaks, we confirmed that it remained in the low-hard state during outburst and decay phases, and we derived its absorption, distance interval, orbital period upper limit, and the late-type nature of companion star, confirming Swift J1745−26 is a low-mass X-ray binary.

An Extremely Massive White Dwarf of the Symbiotic Classical Nova V407 Cyg as Suggested by the RS Oph and U SCO Models

2012 ◽  
Vol 21 (1-2) ◽  
Author(s):  
I. Hachisu ◽  
M. Kato
Keyword(s):  
Light Curve ◽  
White Dwarf ◽  
Early Phase ◽  
Symbiotic Star ◽  
X Ray ◽  
Classical Nova ◽  
Optical Light Curve ◽  
Nova Outburst

AbstractWe have analyzed the optical light curve of the symbiotic star V407 Cyg that underwent a classical nova outburst in 2010 March. Being guided by a supersoft X-ray phase observed during days 20-40 after the nova outburst, we are able to reproduce the light curve during a very early phase of the nova outburst. Our model consists of an outbursting white dwarf and an extended equatorial disk. An extremely massive white dwarf of 1.35-1.37 M

The Complete Spectral Energy Distribution and the Atmospheric Properties of the Helium-Rich White Dwarf MCT 0501−2858

1998 ◽  
Vol 500 (1) ◽  
pp. L41-L44 ◽  
Author(s):  
Stéphane Vennes ◽  
Jean Dupuis ◽  
Pierre Chayer ◽  
Elisha F. Polomski ◽  
William Van Dyke Dixon ◽  
...  
Keyword(s):  
Energy Distribution ◽  
White Dwarf ◽  
Spectral Energy Distribution ◽  
Spectral Energy

scholarly journals The Origin and Evolution of Transition Discs: Successes, Problems, and Open Questions

2016 ◽  
Vol 33 ◽  
Author(s):  
James E. Owen
Keyword(s):  
Spectral Energy Distribution ◽  
Theoretical Work ◽  
Spectral Energy ◽  
Theoretical Understanding ◽  
Origin And Evolution ◽  
Hidden Population ◽  
Open Questions ◽  
Accretion Rates ◽  
Show Evidence ◽  
Dust Component

AbstractTransition discs are protoplanetary discs that show evidence for large holes or wide gaps (with widths comparable to their radii) in their dust component. These discs could be giving us clues about the disc destruction mechanism or hints about the location and time-scales for the formation of planets. However, at the moment there remain key gaps in our theoretical understanding. The vast majority of transition discs are accreting onto their central stars, indicating that—at least close to the star—dust has been depleted from the gas by a very large amount. In this review, we discuss evidence for two distinct populations of transition discs: mm-faint—those with low mm-fluxes, small holes (≲ 10 AU), and low accretion rates (~ 10−10 − 10−9 M⊙ yr−1) and mm-bright—discs with large mm-fluxes, large holes (≳ 20 AU), and high accretion rates ~ 10−8 M⊙ yr−1. MM-faint transition discs are consistent with what would naively be expected from a disc undergoing dispersal; however, mm-bright discs are not, and are likely to be rare and long-lived objects. We discuss the two commonly proposed mechanisms for creating transition discs: photoevaporation and planet–disc interactions, with a particular emphasis on how they would evolve in these models, comparing these predictions to the observed population. More theoretical work on explaining the lack of optically thick, non-accreting transition discs is required in both the photoevaporation and planetary hypothesis, before we can start to use transition discs to constrain models of planet formation. Finally, we suggest that the few discs with primordial looking spectral energy distribution, but serendipitously imaged showing large cavities in the mm (e.g. MWC758 and WSB 60) may represent a hidden population of associated objects. Characterising and understanding how these objects fit into the overall paradigm may allow us to unravel the mystery of transition discs.

scholarly journals ISO-ChaI 52: a weakly accreting young stellar object with a dipper light curve

2020 ◽  
Vol 639 ◽  
pp. L8
Author(s):  
A. Frasca ◽  
C. F. Manara ◽  
J. M. Alcalá ◽  
K. Biazzo ◽  
L. Venuti ◽  
...  
Keyword(s):  
Light Curve ◽  
Spectral Energy Distribution ◽  
Stellar Object ◽  
Spectral Lines ◽  
Spectral Energy ◽  
Emission Characteristic ◽  
Disk System ◽  
Dark Cloud ◽  
Infrared Excess ◽  
Young Stellar Object

We report the discovery of periodic dips in the multiband light curve of ISO-ChaI 52, a young stellar object in the Chamaeleon I dark cloud. This is one of the peculiar objects that display very low or negligible accretion in their UV continuum and spectral lines, although they present a remarkable infrared excess emission characteristic of optically thick circumstellar disks. We have analyzed a spectrum obtained at the Very Large Telescope with the X-shooter spectrograph with the tool ROTFIT to determine the stellar parameters. The latter, along with photometry from our campaign with the Rapid Eye Mount telescope and from the literature, have allowed us to model the spectral energy distribution and to estimate the size and temperature of the inner and outer disk. Based on the rotational period of the star-disk system of 3.45 days, we estimate a disk inclination of 36°. The depth of the dips in different bands has been used to gain information about the occulting material. A single extinction law is not able to fit the observed behavior, while a two-component model of a disk warp composed of a dense region with a gray extinction and an upper layer with an extinction as in the interstellar medium provides a better fit to the data.

scholarly journals Single magnetic white dwarfs with Balmer emission lines: a small class with consistent physical characteristics as possible signposts for close-in planetary companions

2020 ◽  
Vol 499 (2) ◽  
pp. 2564-2574
Author(s):  
Boris T Gänsicke ◽  
Pablo Rodríguez-Gil ◽  
Nicola P Gentile Fusillo ◽  
Keith Inight ◽  
Matthias R Schreiber ◽  
...  
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Late Onset ◽  
Spectral Energy Distribution ◽  
Giant Planet ◽  
Line Emission ◽  
Emission Lines ◽  
Spectral Energy ◽  
Common Mechanism ◽  
Small Class

ABSTRACT We report the identification of SDSS J121929.45+471522.8 as the third apparently isolated magnetic (B ≃ 18.5 ± 1.0 MG) white dwarf exhibiting Zeeman-split Balmer emission lines. The star shows coherent variability at optical wavelengths with an amplitude of ≃0.03 mag and a period of 15.26 h, which we interpret as the spin period of the white dwarf. Modelling the spectral energy distribution and Gaia parallax, we derive a white dwarf temperature of 7500 ± 148 K, a mass of 0.649 ± 0.022 M⊙, and a cooling age of 1.5 ± 0.1 Gyr, as well as an upper limit on the temperature of a sub-stellar or giant planet companion of ≃250 K. The physical properties of this white dwarf match very closely those of the other two magnetic white dwarfs showing Balmer emission lines: GD356 and SDSS J125230.93−023417.7. We argue that, considering the growing evidence for planets and planetesimals on close orbits around white dwarfs, the unipolar inductor model provides a plausible scenario to explain the characteristics of this small class of stars. The tight clustering of the three stars in cooling age suggests a common mechanism switching the unipolar inductor on and off. Whereas Lorentz drift naturally limits the lifetime of the inductor phase, the relatively late onset of the line emission along the white dwarf cooling sequence remains unexplained.

scholarly journals Modelling Kepler eclipsing binaries: homogeneous inference of orbital and stellar properties

2019 ◽  
Vol 489 (2) ◽  
pp. 1644-1666 ◽  
Author(s):  
D Windemuth ◽  
E Agol ◽  
A Ali ◽  
F Kiefer
Keyword(s):  
Main Sequence ◽  
Spectral Energy Distribution ◽  
Eclipsing Binaries ◽  
Spectral Energy ◽  
Parameter Estimates ◽  
Kepler Mission ◽  
Short Period ◽  
Show Evidence ◽  
Stellar Properties ◽  
Stellar Masses

Abstract We report on the properties of eclipsing binaries (EBs) from the Kepler mission with a newly developed photometric modelling code, which uses the light curve, spectral energy distribution of each binary, and stellar evolution models to infer stellar masses without the need for radial velocity (RV) measurements. We present solutions and posteriors to orbital and stellar parameters for 728 systems, forming the largest homogeneous catalogue of full Kepler binary parameter estimates to date. Using comparisons to published RV measurements, we demonstrate that the inferred properties (e.g. masses) are reliable for well-detached main-sequence (MS) binaries, which make up the majority of our sample. The fidelity of our inferred parameters degrades for a subset of systems not well described by input isochrones, such as short-period binaries that have undergone interactions, or binaries with post-MS components. Additionally, we identify 35 new systems which show evidence of eclipse timing variations, perhaps from apsidal motion due to binary tides or tertiary companions. We plan to subsequently use these models to search for and constrain the presence of circumbinary planets in Kepler EB systems.

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