scholarly journals Optical and X-ray studies of three polars: RX J0859.1+0537, RX J0749.1–0549, and RX J0649.8–0737

2019 ◽  
Vol 491 (1) ◽  
pp. 201-214 ◽  
Author(s):  
Arti Joshi ◽  
J C Pandey ◽  
Ashish Raj ◽  
K P Singh ◽  
G C Anupama ◽  
...  
Keyword(s):  
White Dwarf ◽  
Optical Spectra ◽  
Emission Lines ◽  
X Ray ◽  
Long Period ◽  
Photometric And Spectroscopic Observations ◽  
High Ionization ◽  
Orbital Periods ◽  
Actual Size ◽  
Balmer Decrement

ABSTRACT We present optical photometric and spectroscopic observations, and an analysis of archival X-ray data of three polars: RX J0859.1+0537, RX J0749.1–0549, and RX J0649.8–0737. Optical light curves of these three polars reveal eclipse-like features that are deep, total, and variable in shape. The optical and X-ray modulations of RX J0859.1+0537, RX J0749.1–0549, and RX J0649.8–0737 are both found to occur at the orbital periods of 2.393 ± 0.003 h, 3.672 ± 0.001 h, and 4.347 ± 0.001 h, respectively. RX J0859.1+0537 is found to be a polar that lies in the region of the period gap, whereas RX J0749.1–0549 and RX J0649.8–0737 are found to be long-period polars above the period gap. The eclipse length is found to be 61 min for RX J0749.1–0549 in the Rband, which is the highest among the long-period eclipsing polars. The radius of the eclipsed light source is found to be more than the actual size of the white dwarf for these three systems, indicating that the eclipsed component is not only the white dwarf but also appears to include the presence of an extended accretion region. Optical spectra of these systems show the presence of high-ionization emission lines along with the strong Balmer emission lines with an inverted Balmer decrement. Cyclotron harmonics are also detected in the optical spectra from which we infer magnetic field strength of the surface of the white dwarf to be 49 ± 2 MG, 43.5 ± 1.4 MG, and 44 ± 1 MG for RX J0859.1+0537, RX J0749.1–0549, and RX J0649.8–0737, respectively.

SPIN PERIODICITY MEASUREMENTS OF WHITE DWARFS HOSTED IN SOUTHERN HARD X–RAY INTERMEDIATE POLAR CANDIDATES

2010 ◽  
Vol 19 (06) ◽  
pp. 797-803
Author(s):  
ILEANA ANDRUCHOW ◽  
NICOLA MASETTI ◽  
DOMITILLA DE MARTINO ◽  
SERGIO A. CELLONE ◽  
ELENA MASON ◽  
...  
Keyword(s):  
Optical Spectroscopy ◽  
White Dwarf ◽  
Preliminary Analysis ◽  
Cataclysmic Variables ◽  
Optical Spectra ◽  
X Rays ◽  
Optical Photometry ◽  
X Ray ◽  
Orbital Periods ◽  
Magnetic Cataclysmic Variables

Thanks to the combination of hard X–ray data afforded with the INTEGRAL satellite and optical spectroscopy at various telescopes, a number of new, possibly magnetic, Cataclysmic Variables (CVs) has been recently discovered. We here report on the preliminary analysis of B-band optical photometry performed with the 2.15m "Jorge Sahade" telescope at CASLEO (Argentina) on 5 CVs discovered at hard X–rays with INTEGRAL and which show features of a magnetic white dwarf (WD) in their optical spectra. The aim of these observations is to derive the orbital periods of these systems and the spin periodicity of their accreting WD.

scholarly journals Evidence for rapid disc formation and reprocessing in the X-ray bright tidal disruption event candidate AT 2018fyk

2019 ◽  
Vol 488 (4) ◽  
pp. 4816-4830 ◽  
Author(s):  
T Wevers ◽  
D R Pasham ◽  
S van Velzen ◽  
G Leloudas ◽  
S Schulze ◽  
...  
Keyword(s):  
Light Curve ◽  
Optical Spectra ◽  
Emission Lines ◽  
Tidal Disruption ◽  
X Ray ◽  
Physical Conditions ◽  
High Ionization ◽  
Optical Light Curve ◽  
Narrow Emission ◽  
Disruption Event

ABSTRACT We present optical spectroscopic and Swift UVOT/XRT observations of the X-ray and UV/optical bright tidal disruption event (TDE) candidate AT 2018fyk/ASASSN–18ul discovered by ASAS–SN. The Swift light curve is atypical for a TDE, entering a plateau after ∼40 d of decline from peak. After 80 d the UV/optical light curve breaks again to decline further, while the X-ray emission becomes brighter and harder. In addition to broad H, He, and potentially O/Fe lines, narrow emission lines emerge in the optical spectra during the plateau phase. We identify both high-ionization (O iii) and low-ionization (Fe ii) lines, which are visible for ∼45 d. We similarly identify Fe ii lines in optical spectra of ASASSN–15oi 330 d after discovery, indicating that a class of Fe-rich TDEs exists. The spectral similarity between AT 2018fyk, narrow-line Seyfert 1 galaxies, and some extreme coronal line emitters suggests that TDEs are capable of creating similar physical conditions in the nuclei of galaxies. The Fe ii lines can be associated with the formation of a compact accretion disc, as the emergence of low-ionization emission lines requires optically thick, high-density gas. Taken together with the plateau in X-ray and UV/optical luminosity this indicates that emission from the central source is efficiently reprocessed into UV/optical wavelengths. Such a two-component light curve is very similar to that seen in the TDE candidate ASASSN–15lh, and is a natural consequence of a relativistic orbital pericentre.

scholarly journals 2.13. Optical and X-ray variability in NGC 4395

1998 ◽  
Vol 184 ◽  
pp. 83-84 ◽  
Author(s):  
P. Lira ◽  
A. Lawrence
Keyword(s):  
Emission Lines ◽  
X Ray ◽  
High Ionization ◽  
Ngc 4395 ◽  
Narrow Emission

The spectrum of the dwarf Seyfert 1 nucleus in NGC 4395 was first reported about a decade ago (Filippenko & Sargent 1989), showing high ionization narrow emission lines and broad permitted lines. The later detection of radio and X-ray compact nuclear sources and of a featureless UV continuum gave support to the idea that NGC 4395 is a genuine low luminosity AGN (Sramek 1992; Filippenko, Ho & Sargent 1993). However, it has been claimed that, unlike classic Seyferts, NGC 4395 does not vary at all (Shields & Filippenko 1992).

scholarly journals V2282 Sgr Revisited

2014 ◽  
Vol 1 (1) ◽  
pp. 118-122
Author(s):  
Roberto Nesci ◽  
Corinne Rossi ◽  
Antonio Frasca ◽  
Ettore Marilli ◽  
Paolo Persi ◽  
...  
Keyword(s):  
Light Curve ◽  
Accretion Disk ◽  
Main Sequence ◽  
Optical Spectra ◽  
Emission Lines ◽  
Main Sequence Star ◽  
Strong Emission ◽  
X Ray ◽  
Type Spectrum

The nature of V2282 Sgr is examined on the basis of several multiband observations: a 20 years long I-band light curve of V2282 Sgr obtained from archive photographic plates of the Asiago and Catania Observatories; a CCD R-band light curve obtained at Cornero Observatory; JHK photometry from 2MASS and UKDISS; <em>Spitzer</em> IRAC and MIPS images; optical spectra from Loiano Observatory; X-ray flux from <em>CHANDRA</em>. The star has a K-type spectrum with strong emission lines and is irregularly variable at all wavebands. The overall evidences suggest that V2282 Sgr is a Pre Main Sequence star with an accretion disk.

scholarly journals X-Ray and Ultraviolet Observations of AG Draconis during Quiescence and Outburst

1987 ◽  
Vol 93 ◽  
pp. 763-763
Author(s):  
A. Cassatella ◽  
F.A. Córdova ◽  
M. Friedjung ◽  
J. Kenyom ◽  
L. Piro ◽  
...  
Keyword(s):  
Orbital Motion ◽  
Uv Light ◽  
Low Energy ◽  
Emission Lines ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Uv Spectrum ◽  
X Ray ◽  
High Ionization ◽  
Ultraviolet Observations

AbstractWe describe the first X-ray monitoring of a symbiotic star during phases of enhanced activity. AG Dra is a Pop II object with a composite spectrum, characterized by a cool K-type component, prominent high ionization emission lines and a strong UV continuum which is attributed to a hot dwarf companion. Periodic variability of the UV radiation during minimum could be attributed to the orbital motion of the system. In April 1980 HEAO-2 detected an intense, soft X-ray flux from AG Dra, stronger than in other symbiotic stars. After one major outburst of November 1980, which continued until 1983, two more outbursts occurred in February 1985 and January 1986, and coordinated X-ray (EXOSAT) and ultraviolet (IUE) observations were organized to study the behaviour of AG Dra during different activity phases. EXOSAT observations made during decline after the 1985 outburst, revealed a weak X-ray flux in the Thin Lexan filter of the Low Energy dedtector. Observations made during minimum, in June and November 1985, at phases 0.22 and 0.50 of the UV light curve, disclosed the presence of an intense X-ray flux, which was not occulted in November. AG Dra was again observed with EXOSAT in February 1986 when the stellar luminosity was still at maximum. No X-ray flux was detected, in spite of the prominent, high ionization UV spectrum observed with IUE.A detailed discussion of the X-ray and ultraviolet results on AG Dra in the light of possible models is in progress.

scholarly journals X-ray Grating Observations of Recent Recurrent Novae

2011 ◽  
Vol 7 (S281) ◽  
pp. 181-185
Author(s):  
Marina Orio ◽  
Ehud Behar ◽  
J. Gallagher ◽  
A. Bianchini ◽  
E. Chiosi ◽  
...  
Keyword(s):  
White Dwarf ◽  
Peak Temperature ◽  
Carbon Accounting ◽  
Emission Lines ◽  
Absorption Lines ◽  
Red Giants ◽  
X Ray ◽  
Secular Evolution ◽  
Show Evidence ◽  
Collisional Ionization

AbstractTwo recurrent novae (RNe) that do not host red giants were observed in outburst at the beginning of 2009 and 2010, respectively. The first nova was LMC 2009a, and the second one was U Scorpii. Nova LMC 2009a was a relatively slow RN, and it was quite luminous both at optical and X-ray wavelengths. U Sco is the fastest nova ever recorded. Its supersoft X-ray phase started a couple of weeks after optical maximum and lasted for about a month, while for Nova LMC 2009a this phase started four months after maximum and lasted for 5 months. For both novae, the first X-ray spectrum taken while the luminous supersoft X-ray source was beginning to emerge is remarkably similar with broad and prominent emission lines of nitrogen and carbon accounting for at least 30% of the X-ray flux. Blue-shifted absorption and red-shifted emission form apparent P-Cyg profiles. We attribute the emission features to the ejecta and show evidence that they are largely due to collisional ionization. In the case of U Sco the absorption lines were embedded in the emission features after the first observation. We find evidence that in U Scorpii we were observing the Thomson reflected spectrum at a distance of ≃ 3 R⊙ from the white dwarf rather than the atmosphere itself. For both novae, the peak temperature was remarkably high, probably close to 900,000 K for U Sco, and about 600,000 K for Nova LMC 2009a. We suggest that these two objects represent different stages of RNe secular evolution.

Discovery of new changing look in NGC 1566

2019 ◽  
Vol 15 (S356) ◽  
pp. 127-131
Author(s):  
Victor L. Oknyansky ◽  
Sergey S. Tsygankov ◽  
Vladimir M. Lipunov ◽  
Evgeny S. Gorbovskoy ◽  
Nataly V. Tyurina
Keyword(s):  
South African ◽  
Astronomical Observatory ◽  
Emission Lines ◽  
Optical Monitoring ◽  
X Ray ◽  
Broad Emission ◽  
High Ionization ◽  
The Galaxy ◽  
Multi Wavelength ◽  
Bright Phase

AbstractWe present continuation of the multi-wavelength (from X-ray to optical) monitoring of the nearby changing look (CL) active galactic nucleus in the galaxy NGC 1566 performed with the Neil Gehrels Swift Observatory,the MASTER Global Robotic Network over the period 2007–2019. We also present continuation of optical spectroscopy using the South African Astronomical Observatory 1.9-m telescope between Aug. 2018 and Mar. 2019. We investigate remarkable re-brightenings in of the light curve following the decline from the bright phase observed at Dec. 2018 and at the end of May 2019. For the last optical spectra (31 Nov. 2018–28 Mar. 2019) we see dramatic changes compared to 2 Aug. 2018, accompanied by the fading of broad emission lines and high-ionization [FeX]6374Å line. Effectively, one more CL was observed for this object: changing from Sy1.2 to the low state as Sy 1.8–Sy1.9 type. Some possible explanations of the observed CL are discussed.

scholarly journals Influence of the initial orbital period and accretion efficiency on the low-mass binary evolution

2021 ◽  
pp. 25-30
Author(s):  
J. Petrovic
Keyword(s):  
Mass Transfer ◽  
Orbital Period ◽  
White Dwarf ◽  
Binary Systems ◽  
Evolutionary Models ◽  
Stable Case ◽  
Long Period ◽  
Low Mass ◽  
Orbital Periods ◽  
Binary Evolution

This paper presents detailed evolutionary models of low-mass binary systems (1.25 + 1 M?) with initial orbital periods of 10, 50 and 100 days and accretion efficiency of 10%, 20%, 50%, and a conservative assumption. All models are calculated with the MESA (Modules for Experiments in Stellar Astrophysics) evolutionary code. We show that such binary systems can evolve via a stable Case B mass transfer into long period helium white dwarf systems.

scholarly journals The Remarkable Spin-down and Ultrafast Outflows of the Highly Pulsed Supersoft Source of Nova Herculis 2021

2021 ◽  
Vol 922 (2) ◽  
pp. L42
Author(s):  
Jeremy J. Drake ◽  
Jan-Uwe Ness ◽  
Kim L. Page ◽  
G. J. M. Luna ◽  
Andrew P. Beardmore ◽  
...  
Keyword(s):  
White Dwarf ◽  
Emission Lines ◽  
Optical Observations ◽  
High Mass ◽  
X Rays ◽  
Pulse Profile ◽  
X Ray ◽  
Classical Nova ◽  
First Time ◽  
The Magnetic Field

Abstract Nova Her 2021 (V1674 Her), which erupted on 2021 June 12, reached naked-eye brightness and has been detected from radio to γ-rays. An extremely fast optical decline of 2 magnitudes in 1.2 days and strong Ne lines imply a high-mass white dwarf. The optical pre-outburst detection of a 501.42 s oscillation suggests a magnetic white dwarf. This is the first time that an oscillation of this magnitude has been detected in a classical nova prior to outburst. We report X-ray outburst observations from Swift and Chandra that uniquely show (1) a very strong modulation of supersoft X-rays at a different period from reported optical periods, (2) strong pulse profile variations and the possible presence of period variations of the order of 0.1–0.3 s, and (3) rich grating spectra that vary with modulation phase and show P Cygni–type emission lines with two dominant blueshifted absorption components at ∼3000 and 9000 km s−1 indicating expansion velocities up to 11,000 km s−1. X-ray oscillations most likely arise from inhomogeneous photospheric emission related to the magnetic field. Period differences between reported pre- and post-outburst optical observations, if not due to other period drift mechanisms, suggest a large ejected mass for such a fast nova, in the range 2 × 10−5–2 × 10−4 M ⊙. A difference between the period found in the Chandra data and a reported contemporaneous post-outburst optical period, as well as the presence of period drifts, could be due to weakly nonrigid photospheric rotation.

scholarly journals Effects of Eccentric Orbit of BF Cygni on IUE and Optical Spectra

1988 ◽  
Vol 103 ◽  
pp. 299-300
Author(s):  
J. Mikolajewska ◽  
M. Mikolajewski
Keyword(s):  
Emission Measure ◽  
Line Emission ◽  
Optical Spectra ◽  
Emission Lines ◽  
Recent Analysis ◽  
Emission Region ◽  
Galactic Rotation ◽  
Resonance Emission ◽  
High Ionization ◽  
Cosmic Abundance

A recent analysis of all available photometric data has resulted in a new ephemeris for BF Cyg: MIN=JD 2415058 + 756.8E. Simultaneously, optical spectra collected in 1979–1986 showed periodic changes of all emission lines (Mikolajewska 1987; Mikolajewska & lijima 1987). It is interesting that the forbidden lines of [OIII] varied in antiphase to the permitted emission lines and optical brightness.IUE spectra taken in 1979–1981 showed a strong hot continuum and high ionization resonance emission lines of NV, SilV CIV, intercombination lines of NIV], NIII], SiIII], CIII] and OIII] as well as Hell emission. The observed λ2200Å interstellar absorption band suggests E(B-V)≃0.3. Taking into account the interstellar reddening distribution in the vicinity of BF Cyg (Lucke 1978; Mikolajewska & Mikolajewski 1980), the observed extinction implies a distance d≲1.5kpc. This distance is in good agreement with the observed low value of the systemic radial velocity (∼15 km/s, Fig.1) of BF Cyg and the standard galactic rotation law. The standard extinction curve with E(B-V)=0.3 (Seaton 1979) was used for reddening correction of the spectra. The UV continuum of BF Cyg can be interpreted as a combination of a hot subdwarf (Teff≃60000K, L≃2500L⊙ for d=1.5kpc) and hydrogen bf+ff emission (Te≃10000K). The emission measure of the nebular (bf+ff) continuum varied from ∼4×1059cm−3 at maximum to ∼1059cm−3 at minimum. Assuming cosmic abundance of Si/C the observed SiIII]/CIII] line ratio implies ne≃2×l010cm−3 at the photometric maximum and ne≃3×109cm−3 at the minimum. We assume that these values are representative of the region where the bulk of the HI Balmer and intercombination line emission is produced. The ratio of NV(1240)/NIV(1720) gives Te(NV)≃11500K close to the value derived for the Balmer emission region from the UV continuum fit.

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