20 research outputs found
CONSTRAINING THE ANGULAR MOMENTUM EVOLUTION OF V455 ANDROMEDAE
Time-series photometry on the cataclysmic variable V455 Andromedae (hereafter V455 And, HS 2331+3905) reveals a rotation period shorter than the orbital period, implying the presence of a magnetic field. We expect that this magnetic field channels the accreted matter from the disk toward the white dwarf poles, classifying it as an Intermediate Polar. The two polar spinning emission areas are visible in the lightcurves at the rotation period of 67.61970396 ± 0.00000072 s, and its harmonic. Using photometric observations of V455 And obtained from 2007 October to 2015, we derive 3Ï upper limits to the rate of change of the spin harmonic (SH) with time to be dPSH/dt †â7.5 Ă 10â15 s sâ1 employing the OâC method, and â5.4 Ă 10â15 s sâ1 with a direct nonlinear least squares fit. There is no significant detection of a changing spin period for the duration of 2007 Octoberâ2015. The 3Ï upper limit for the rate of change of spin period with time is dPspin/dt †â10.8 Ă 10â15 s sâ1 or â0.34 ÎŒs yrâ1. V455 And underwent a large-amplitude dwarf nova outburst in 2007 September. The pre-outburst data reflect a period 4.8 ± 2.2 ÎŒs longer than the best-fit post-outburst spin period. The angular momentum gained by the white dwarf from matter accreted during outburst and its slight subsequent shrinking should both cause the star to spin slightly faster after the outburst. We estimate that the change in spin period due to the outburst should be 5 ÎŒs, consistent with the empirical determination of 4.8 ± 2.2 ÎŒs (3Ï upper limit of 11.4 ÎŒs)
Constraining the angular momentum evolution of V455 Andromedae
Time-series photometry on the cataclysmic variable V455 Andromedae (hereafter V455 And, HS 2331+3905) reveals a rotation period shorter than the orbital period, implying the presence of a magnetic field. We expect that this magnetic field channels the accreted matter from the disk toward the white dwarf poles, classifying it as an Intermediate Polar. The two polar spinning emission areas are visible in the lightcurves at the rotation period of 67.61970396 ± 0.00000072 s, and its harmonic. Using photometric observations of V455 And obtained from 2007 October to 2015, we derive 3Ï upper limits to the rate of change of the spin harmonic (SH) with time to be dPSH/dt †â7.5 Ă 10â15 s sâ1 employing the OâC method, and â5.4 Ă 10â15 s sâ1 with a direct nonlinear least squares fit. There is no significant detection of a changing spin period for the duration of 2007 Octoberâ2015. The 3Ï upper limit for the rate of change of spin period with time is dPspin/dt †â10.8 Ă 10â15 s sâ1 or â0.34 ÎŒs yrâ1. V455 And underwent a large-amplitude dwarf nova outburst in 2007 September. The pre-outburst data reflect a period 4.8 ± 2.2 ÎŒs longer than the best-fit post-outburst spin period. The angular momentum gained by the white dwarf from matter accreted during outburst and its slight subsequent shrinking should both cause the star to spin slightly faster after the outburst. We estimate that the change in spin period due to the outburst should be 5 ÎŒs, consistent with the empirical determination of 4.8 ± 2.2 ÎŒs (3Ï upper limit of 11.4 ÎŒs)
LSQ13ddu: a rapidly evolving stripped-envelope supernova with early circumstellar interaction signatures
This paper describes the rapidly evolving and unusual supernova LSQ13ddu, discovered by the La Silla-QUEST survey. LSQ13ddu displayed a rapid rise of just 4.8 ± 0.9 d to reach a peak brightness of â19.70 ± 0.02 mag in the LSQgr band. Early spectra of LSQ13ddu showed the presence of weak and narrow HeI features arising from interaction with circumstellar material (CSM). These interaction signatures weakened quickly, with broad features consistent with those seen in stripped-envelope SNe becoming dominant around two weeks after maximum. The narrow HeI velocities are consistent with the wind velocities of luminous blue variables but its spectra lack the typically seen hydrogen features. The fast and bright early light curve is inconsistent with radioactive â”â¶Ni powering but can be explained through a combination of CSM interaction and an underlying â”â¶Ni decay component that dominates the later time behaviour of LSQ13ddu. Based on the strength of the underlying broad features, LSQ13ddu appears deficient in He compared to standard SNe Ib
The carbon-rich type Ic supernova 2016adj in the iconic dust lane of Centaurus A: signatures of interaction with circumstellar hydrogen?
We present a comprehensive data set of supernova (SN) 2016adj located within
the central dust lane of Centaurus A. SN 2016adj is significantly reddened and
after correcting the peak apparent -band magnitude ()
for Milky Way reddening and our inferred host-galaxy reddening parameters
(i.e., and ), we estimate
it reached a peak absolute magnitude of . Detailed inspection of
the optical/NIR spectroscopic time-series reveals a carbon-rich SN Ic and not a
SN Ib/IIb as previously suggested in the literature. The NIR spectra shows
prevalent carbon-monoxide formation occurring already by +41 days past -band
maximum, which is days earlier than previously reported in the
literature for this object. Interestingly around two months past maximum, the
NIR spectrum of SN~2016adj begins to exhibit H features, with a +97~d medium
resolution spectrum revealing both Paschen and Bracket lines with absorption
minima of km/s, full-width-half-maximum emission velocities of
km/s, and emission line ratios consistent with a dense emission
region. We speculate these attributes are due to circumstellar interaction
(CSI) between the rapidly expanding SN ejecta and a H-rich shell of material
formed during the pre-SN phase. A bolometric light curve is constructed and a
semi-analytical model fit suggests the supernova synthesized 0.5 solar masses
of Ni and ejected 4.2 solar masses of material, though these values
should be approached with caution given the large uncertainties associated with
the adopted reddening parameters, possible CSI contamination, and known light
echo emission. Finally, inspection of Hubble Space Telescope archival data
yielded no progenitor detection.Comment: Submitted to A&A, comments are welcom
A Large Fraction of Hydrogen-rich Supernova Progenitors Experience Elevated Mass Loss Shortly Prior to Explosion
Spectroscopic detection of narrow emission lines traces the presence of circumstellar mass distributions around massive stars exploding as core-collapse supernovae. Transient emission lines disappearing shortly after the supernova explosion suggest that the material spatial extent is compact and implies an increased mass loss shortly prior to explosion. Here, we present a systematic survey for such transient emission lines (Flash Spectroscopy) among Type II supernovae detected in the first year of the Zwicky Transient Facility survey. We find that at least six out of ten events for which a spectrum was obtained within two days of the estimated explosion time show evidence for such transient flash lines. Our measured flash event fraction (>30% at 95% confidence level) indicates that elevated mass loss is a common process occurring in massive stars that are about to explode as supernovae
The prevalence and influence of circumstellar material around hydrogen-rich supernova progenitors
Narrow transient emission lines (flash-ionization features) in early
supernova (SN) spectra trace the presence of circumstellar material (CSM)
around the massive progenitor stars of core-collapse SNe. The lines disappear
within days after the SN explosion, suggesting that this material is spatially
confined, and originates from enhanced mass loss shortly (months to a few
years) prior to explosion. We performed a systematic survey of H-rich (Type II)
SNe discovered within less than two days from explosion during the first phase
of the Zwicky Transient Facility (ZTF) survey (2018-2020), finding thirty
events for which a first spectrum was obtained within days from
explosion. The measured fraction of events showing flash ionisation features
( at confidence level) confirms that elevated mass loss in
massive stars prior to SN explosion is common. We find that SNe II showing
flash ionisation features are not significantly brighter, nor bluer, nor more
slowly rising than those without. This implies that CSM interaction does not
contribute significantly to their early continuum emission, and that the CSM is
likely optically thin. We measured the persistence duration of flash ionisation
emission and find that most SNe show flash features for days.
Rarer events, with persistence timescales days, are brighter and rise
longer, suggesting these may be intermediate between regular SNe II and
strongly-interacting SNe IIn
LSQ13ddu: a rapidly evolving stripped-envelope supernova with early circumstellar interaction signatures
This paper describes the rapidly evolving and unusual supernova LSQ13ddu, discovered by the La Silla-QUEST survey. LSQ13ddu displayed a rapid rise of just 4.8 +/- 0.9 d to reach a peak brightness of -19.70 +/- 0.02 mag in the LSQgr band. Early spectra of LSQ13ddu showed the presence of weak and narrow He I features arising from interaction with circumstellar material (CSM). These interaction signatures weakened quickly, with broad features consistent with those seen in stripped-envelope SNe becoming dominant around two weeks after maximum. The narrow He I velocities are consistent with the wind velocities of luminous blue variables but its spectra lack the typically seen hydrogen features. The fast and bright early light curve is inconsistent with radioactive Ni-56 powering but can be explained through a combination of CSM interaction and an underlying Ni-56 decay component that dominates the later time behaviour of LSQ13ddu. Based on the strength of the underlying broad features, LSQ13ddu appears deficient in He compared to standard SNe Ib
Type Ibn Supernovae Show Photometric Homogeneity and Spectral Diversity at Maximum Light
Type Ibn supernovae (SNe) are a small yet intriguing class of explosions whose spectra are characterized by low-velocity helium emission lines with little to no evidence for hydrogen. The prevailing theory has been that these are the core-collapse explosions of very massive stars embedded in helium-rich circumstellar material (CSM). We report optical observations of six new SNe Ibn: PTF11rfh, PTF12ldy, iPTF14aki, iPTF15ul, SN 2015G, and iPTF15akq. This brings the sample size of such objects in the literature to 22. We also report new data, including a near-infrared spectrum, on the Type Ibn SN 2015U. In order to characterize the class as a whole, we analyze the photometric and spectroscopic properties of the full Type Ibn sample. We find that, despite the expectation that CSM interaction would generate a heterogeneous set of light curves, as seen in SNe IIn, most Type Ibn light curves are quite similar in shape, declining at rates around 0.1 mag day-1 during the first month after maximum light, with a few significant exceptions. Early spectra of SNe Ibn come in at least two varieties, one that shows narrow P Cygni lines and another dominated by broader emission lines, both around maximum light, which may be an indication of differences in the state of the progenitor system at the time of explosion. Alternatively, the spectral diversity could arise from viewing-angle effects or merely from a lack of early spectroscopic coverage. Together, the relative light curve homogeneity and narrow spectral features suggest that the CSM consists of a spatially confined shell of helium surrounded by a less dense extended wind