Aims.
We study PTF11mnb, a He-poor supernova (SN) whose light curves resemble those of SN 2005bf, a peculiar double-peaked stripped-envelope (SE) SN, until the declining phase after the main peak. We ...investigate the mechanism powering its light curve and the nature of its progenitor star.
Methods.
Optical photometry and spectroscopy of PTF11mnb are presented. We compared light curves, colors and spectral properties to those of SN 2005bf and normal SE SNe. We built a bolometric light curve and modeled this light curve with the SuperNova Explosion Code (SNEC) hydrodynamical code explosion of a MESA progenitor star and semi-analytic models.
Results.
The light curve of PTF11mnb turns out to be similar to that of SN 2005bf until ~50 d when the main (secondary) peaks occur at −18.5 mag. The early peak occurs at ~20 d and is about 1.0 mag fainter. After the main peak, the decline rate of PTF11mnb is remarkably slower than what was observed in SN 2005bf, and it traces well the
56
Co decay rate. The spectra of PTF11mnb reveal a SN Ic and have no traces of He unlike in the case of SN Ib 2005bf, although they have velocities comparable to those of SN 2005bf. The whole evolution of the bolometric light curve is well reproduced by the explosion of a massive (
M
ej
= 7.8
M
⊙
), He-poor star characterized by a double-peaked
56
Ni distribution, a total
56
Ni mass of 0.59
M
⊙
, and an explosion energy of 2.2 × 10
51
erg. Alternatively, a normal SN Ib/c explosion (
M
(
56
Ni) = 0.11
M
⊙
,
E
K
= 0.2 × 10
51
erg,
M
ej
= 1
M
⊙
) can power the first peak while a magnetar, with a magnetic field characterized by
B
= 5.0 × 10
14
G, and a rotation period of
P
= 18.1 ms, provides energy for the main peak. The early
g
-band light curve can be fit with a shock-breakout cooling tail or an extended envelope model from which a radius of at least 30
R
⊙
is obtained.
Conclusions.
We presented a scenario where PTF11mnb was the explosion of a massive, He-poor star, characterized by a double-peaked
56
Ni distribution. In this case, the ejecta mass and the absence of He imply a large ZAMS mass (~85
M
⊙
) for the progenitor, which most likely was a Wolf-Rayet star, surrounded by an extended envelope formed either by a pre-SN eruption or due to a binary configuration. Alternatively, PTF11mnb could be powered by a SE SN with a less massive progenitor during the first peak and by a magnetar afterward.
Forbidden hugs in pandemic times Pastorello, A.; Fraser, M.; Valerin, G. ...
Astronomy and astrophysics (Berlin),
02/2021, Letnik:
646
Journal Article
Recenzirano
We present the follow-up campaign of the luminous red nova (LRN)
AT 2019zhd
, the third event of this class observed in
M 31
. The object was followed by several sky surveys for about five months ...before the outburst, during which it showed a slow luminosity rise. In this phase, the absolute magnitude ranged from
M
r
= −2.8 ± 0.2 mag to
M
r
= −5.6 ± 0.1 mag. Then, over a four to five day period,
AT 2019zhd
experienced a major brightening, reaching a peak of
M
r
= −9.61 ± 0.08 mag and an optical luminosity of 1.4 × 10
39
erg s
−1
. After a fast decline, the light curve settled onto a short-duration plateau in the red bands. Although less pronounced, this feature is reminiscent of the second red maximum observed in other LRNe. This phase was followed by a rapid linear decline in all bands. At maximum, the spectra show a blue continuum with prominent Balmer emission lines. The post-maximum spectra show a much redder continuum, resembling that of an intermediate-type star. In this phase, H
α
becomes very weak, H
β
is no longer detectable, and a forest of narrow absorption metal lines now dominate the spectrum. The latest spectra, obtained during the post-plateau decline, show a very red continuum (
T
eff
≈ 3000 K) with broad molecular bands of TiO, similar to those of M-type stars. The long-lasting, slow photometric rise observed before the peak resembles that of LRN
V1309 Sco
, which was interpreted as the signature of the common-envelope ejection. The subsequent outburst is likely due to the gas outflow following a stellar merging event. The inspection of archival HST images taken 22 years before the LRN discovery reveals a faint red source (
M
F
555
W
= 0.21 ± 0.14 mag, with
F
555
W
−
F
814
W
= 2.96 ± 0.12 mag) at the position of
AT 2019zhd
, which is the most likely quiescent precursor. The source is consistent with expectations for a binary system including a predominant M5-type star.
Since the discovery of the accelerating expansion of the Universe more than two decades ago, Type Ia Supernovae (SNe Ia) have been extensively used as standardisable candles in the optical. However, ...SNe Ia have shown to be more homogeneous in the near-infrared (NIR), where the effect of dust extinction is also attenuated. In this work, we explore the possibility of using a low number of NIR observations for accurate distance estimations, given the homogeneity at these wavelengths. We found that one epoch in
J
and/or
H
band, plus good
g
r
-band coverage, gives an accurate estimation of peak magnitudes in the
J
(
J
max
) and
H
(
H
max
) bands. The use of a single NIR epoch only introduces an additional scatter of ∼0.05 mag for epochs around the time of
B
-band peak magnitude (
T
max
). We also tested the effect of optical cadence and signal-to-noise ratio (S/N) in the estimation of
T
max
and its uncertainty propagation to the NIR peak magnitudes. Both cadence and S/N have a similar contribution, where we constrained the introduced scatter of each to < 0.02 mag in
J
max
and < 0.01 in
H
max
. However, these effects are expected to be negligible, provided the data quality is comparable to that obtained for observations of nearby SNe (
z
≲ 0.1). The effect of S/N in the NIR was tested as well. For SNe Ia at 0.08 <
z
≲ 0.1, NIR observations with better S/N than that found in the CSP sample is necessary to constrain the introduced scatter to a minimum (≲0.05 mag). These results provide confidence for our FLOWS project that is aimed at using SNe Ia with public ZTF optical light curves and few NIR epochs to map out the peculiar velocity field of the local Universe. This will allow us to determine the distribution of dark matter in our own supercluster, Laniakea, and to test the standard cosmological model by measuring the growth rate of structures, parameterised by
f
D
, and the
Hubble
-Lemaître constant,
H
0
.
Context. Research on supernovae (SNe) over the past decade has confirmed that there is a distinct class of events which are much more luminous (by ~2 mag) than canonical core-collapse SNe (CCSNe). ...These events with visual peak magnitudes ≲–21 are called superluminous SNe (SLSNe). The mechanism that powers the light curves of SLSNe is still not well understood. The proposed scenarios are circumstellar interaction, the emergence of a magnetar after core collapse, or disruption of a massive star through pair production. Aims. There are a few intermediate events which have luminosities between these two classes. They are important for constraining the nature of the progenitors of these two different populations and their environments and powering mechanisms. Here we study one such object, SN 2012aa. Methods. We observed and analysed the evolution of the luminous Type Ic SN 2012aa. The event was discovered by the Lick Observatory Supernova Search in an anonymous galaxy (z ≈ 0.08). The optical photometric and spectroscopic follow-up observations were conducted over a time span of about 120 days. Results. With an absolute V-band peak of ~− 20 mag, the SN is an intermediate-luminosity transient between regular SNe Ibc and SLSNe. SN 2012aa also exhibits an unusual secondary bump after the maximum in its light curve. For SN 2012aa, we interpret this as a manifestation of SN-shock interaction with the circumstellar medium (CSM). If we assume a 56Ni-powered ejecta, the quasi-bolometric light curve requires roughly 1.3 M⊙ of 56Ni and an ejected mass of ~14M⊙. This also implies a high kinetic energy of the explosion, ~5.4 × 1051 erg. On the other hand, the unusually broad light curve along with the secondary peak indicate the possibility of interaction with CSM. The third alternative is the presence of a central engine releasing spin energy that eventually powers the light curve over a long time. The host of SN 2012aa is a star-forming Sa/Sb/Sbc galaxy. Conclusions. Although the spectral properties of SN 2012aa and its velocity evolution are comparable to those of normal SNe Ibc, its broad light curve along with a large peak luminosity distinguish it from canonical CCSNe, suggesting that the event is an intermediate-luminosity transient between CCSNe and SLSNe at least in terms of peak luminosity. In comparison to other SNe, we argue that SN 2012aa belongs to a subclass where CSM interaction plays a significant role in powering the SN, at least during the initial stages of evolution.
The Carnegie Supernova Project I Holmbo, S.; Stritzinger, M. D.; Karamehmetoglu, E. ...
Astronomy and astrophysics (Berlin),
07/2023, Letnik:
675
Journal Article
Recenzirano
An analysis leveraging 170 optical spectra of 35 stripped-envelope (SE) core-collapse supernovae (SNe) observed by the Carnegie Supernova Project I and published in a companion paper is presented. ...Mean template spectra were constructed for the SNe IIb, Ib, and Ic subtypes, and parent ions associated with designated spectral features are identified with the aid of the spectral synthesis code
SYNAPPS
. Our modeled mean spectra suggest the ∼6150 Å feature in SNe IIb may have an underlying contribution due to silicon, while the same feature in some SNe Ib may have an underlying contribution due to hydrogen. Standard spectral line diagnostics consisting of pseudo-equivalent widths (pEWs) and blue-shifted Doppler velocity were measured for each of the spectral features. Correlation matrices and rolling mean values of both spectral diagnostics were constructed. A principle component analysis (PCA) was applied to various wavelength ranges of the entire dataset and suggests clear separation among the different SE SN subtypes, which follows from trends previously identified in the literature. In addition, our findings reveal the presence of two SNe IIb subtypes, a select number of SNe Ib displaying signatures of weak, high-velocity hydrogen, and a single SN Ic with evidence of weak helium features. Our PCA results can be leveraged to obtain robust subtyping of SE SNe based on a single spectrum taken during the so-called photospheric phase, separating SNe IIb from SNe Ib with ∼80% completion.
The Carnegie Supernova Project II Stritzinger, M. D.; Taddia, F.; Fraser, M. ...
Astronomy and astrophysics (Berlin),
07/2020, Letnik:
639
Journal Article
Recenzirano
We present multiwavelength observations of two gap transients that were followed by the Carnegie Supernova Project-II. The observations are 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 three days after outburst, the subsequent optical and near-infrared broadband followup extending over a period of about two months, two visual and two near-infrared wavelength spectra, and
Spitzer
Space Telescope observations extending from early (+28 d) to late (+1155 d) phases. SNhunt120 resembles other ILRTs such as NGC 300-2008-OT and SN 2008S, and like these other ILRTs, SNhunt120 exhibits prevalent mid-infrared emission at both early and late phases. From the comparison of SNhunt120 and other ILRTs to electron-capture supernova simulations, we find that the current models underestimate the explosion kinetic energy and thereby produce synthetic light curves that overestimate the luminosity. Finally, examination of pre-outburst
Hubble
Space Telescope images yields no progenitor detection.
The Carnegie Supernova Project II Stritzinger, M. D.; Taddia, F.; Fraser, M. ...
Astronomy and astrophysics (Berlin),
07/2020, Letnik:
639
Journal Article
Recenzirano
We present optical and near-infrared broadband photometry and optical spectra of AT 2014ej from 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 similar to that of LRN SN 2017jfs. A medium-dispersion visual-wavelength spectrum of AT 2014ej taken with the
Magellan Clay
telescope exhibits a P Cygni H
α
feature characterized by a blue velocity at zero intensity of ≈110 km s
−1
and a P Cygni minimum velocity of ≈70 km s
−1
. We attribute this 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 at the brighter end of the luminosity distribution. Comparison of the ultra-violet, optical, infrared light curves of well-observed LRNe to common-envelope evolution models from the literature indicates that the models underpredict the luminosity of the comparison sample at all phases and also produce inconsistent timescales of the secondary peak. Future efforts to model LRNe should expand upon the current parameter space we explore here and therefore may consider more massive systems and a wider range of dynamical timescales.
Forbidden hugs in pandemic times Pastorello, A.; Valerin, G.; Fraser, M. ...
Astronomy and astrophysics (Berlin),
03/2021, Letnik:
647
Journal Article
Recenzirano
We present the results of our monitoring campaigns of the luminous red novae (LRNe) AT 2020hat in NGC 5068 and AT 2020kog in NGC 6106. The two objects were imaged (and detected) before their ...discovery by routine survey operations. They show a general trend of slow luminosity rise, lasting at least a few months. The subsequent major LRN outbursts were extensively followed in photometry and spectroscopy. The light curves present an initial short-duration peak, followed by a redder plateau phase. AT 2020kog is a moderately luminous event peaking at ∼7 × 10
40
erg s
−1
, while AT 2020hat is almost one order of magnitude fainter than AT 2020kog, although it is still more luminous than V838 Mon. In analogy with other LRNe, the spectra of AT 2020kog change significantly with time. They resemble those of type IIn supernovae at early phases, then they become similar to those of K-type stars during the plateau, and to M-type stars at very late phases. In contrast, AT 2020hat already shows a redder continuum at early epochs, and its spectrum shows the late appearance of molecular bands. A moderate-resolution spectrum of AT 2020hat taken at +37 d after maximum shows a forest of narrow P Cygni lines of metals with velocities of 180 km s
−1
, along with an H
α
emission with a full-width at half-maximum velocity of 250 km s
−1
. For AT 2020hat, a robust constraint on its quiescent progenitor is provided by archival images of the
Hubble
Space Telescope. The progenitor is clearly detected as a mid-K type star, with an absolute magnitude of
M
F
606
W
= −3.33 ± 0.09 mag and a colour of
F
606
W
−
F
814
W
= 1.14 ± 0.05 mag, which are inconsistent with the expectations from a massive star that could later produce a core-collapse supernova. Although quite peculiar, the two objects nicely match the progenitor versus light curve absolute magnitude correlations discussed in the literature.
iPTF Survey for Cool Transients Adams, S. M.; Blagorodnova, N.; Kasliwal, M. M. ...
Publications of the Astronomical Society of the Pacific,
03/2018, Letnik:
130, Številka:
985
Journal Article
Recenzirano
Odprti dostop
We performed a wide-area (2000 deg2) 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 selection of cool and dusty transients.
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