arXiv subjects

Massimo Della Valle

Publications and source records attributed to Massimo Della Valle.

At least 91 records · Page 5Linked to original sources

arXiv2012

Evidence for Type Ia Supernova Diversity from Ultraviolet Observations with the Hubble Space Telescope

We present ultraviolet (UV) spectroscopy and photometry of four Type Ia supernovae (SNe 2004dt, 2004ef, 2005M, and 2005cf) obtained with the UV prism of the Advanced Camera for Surveys on the Hubble Space Telescope. This dataset provides unique spectral time series down to 2000 Angstrom. Significant diversity is seen in the near maximum-light spectra (~ 2000--3500 Angstrom) for this small sample. The corresponding photometric data, together with archival data from Swift Ultraviolet/Optical Telescope observations, provide further evidence of increased dispersion in the UV emission with respect to the optical. The peak luminosities measured in uvw1/F250W are found to correlate with the B-band light-curve shape parameter dm15(B), but with much larger scatter relative to the correlation in the broad-band B band (e.g., ~0.4 mag versus ~0.2 mag for those with 0.8 < dm15 < 1.7 mag). SN 2004dt is found as an outlier of this correlation (at > 3 sigma), being brighter than normal SNe Ia such as SN 2005cf by ~0.9 mag and ~2.0 mag in the uvw1/F250W and uvm2/F220W filters, respectively. We show that different progenitor metallicity or line-expansion velocities alone cannot explain such a large discrepancy. Viewing-angle effects, such as due to an asymmetric explosion, may have a significant influence on the flux emitted in the UV region. Detailed modeling is needed to disentangle and quantify the above effects.

astro-ph.HE↗

arXiv2011

Electromagnetic priors for black hole spindown in searches for gravitational-waves from supernovae and long GRBs

Some core-collapse supernovae appear to be hyper-energetic, and a subset of these are aspherical and associated with long GRBs. We use observations of electromagnetic emission from core-collapse supernovae and GRBs to impose constraints on their free energy source as a prior to searches for their gravitational wave emission. We review these events based on a finite efficiency for the conversion of spin energy to magnetic winds powering supernovae. We find that some of the hyper-energetic events cannot be powered by the spindown of rapidly rotating proto-neutron stars by virtue of their limited rotational energy. They can, instead, be produced by the spindown of black holes providing a distinct prospect for gravitational-wave emission of interest to LIGO, Virgo, and the LCGT.

astro-ph.HE↗

arXiv2011

No quantum gravity signature from the farthest quasars

Context: Strings and other alternative theories describing the quantum properties of space-time suggest that space-time could present a foamy structure and also that, in certain cases, quantum gravity (QG) may manifest at energies much below the Planck scale. One of the observable effects could be the degradation of the diffraction images of distant sources. Aims: We searched for this degradation effect, caused by QG fluctuations, in the light of the farthest quasars (QSOs) observed by the Hubble Space Telescope with the aim of setting new limits on the fluctuations of the space-time foam and QG models. Methods: We developed a software that estimates and compares the phase variation in the interference patterns of the high-redshift QSOs, taken from the snapshot survey of HST-SDSS, with those of stars that are expected to not be affected by QG effects. We used a two-parameter function to determine, for each test star and QSO, the maximum of the diffraction pattern and to calculate the Strehl ratio. Results: Our results go far beyond those already present in the literature. By adopting the most conservative approach where the correction terms, that describe the possibility for space-time fluctuations cumulating across long distances and partially compensate for the effects of the phase variations, are taken into account. We exclude the random walk model and most of the holographic models of the space-time foam. Without considering these correction terms, all the main QG scenarios are excluded. Finally, our results show the absence of any directional dependence of QG effects and the validity of the cosmological principle with an independent method; that is, viewed on a large scale, the properties of the Universe are the same for all observers, including the effects of space-time fluctuations.

gr-qc↗

arXiv2011

Prospects for true calorimetry on Kerr black holes in core-collapse supernovae and mergers

Observational evidence for black hole spin down has been found in the normalized light curves of long GRBs in the BATSE catalogue. Over the duration $T_{90}$ of the burst, matter swept up by the central black hole is susceptible to non-axisymmetries producing gravitational radiation with a negative chirp. A time sliced matched filtering method is introduced to capture phase-coherence on intermediate timescales, $τ$, here tested by injection of templates into experimental strain noise, $h_n(t)$. For TAMA 300, $h_n(f)\simeq 10^{-21}$ Hz$^{-\frac{1}{2}}$ at $f=1$ kHz gives a sensitivity distance for a reasonably accurate extraction of the trajectory in the time frequency domain of about $D\simeq 0.07-0.10$ Mpc for spin fown of black holes of mass $M=10-12M_\odot$ with $τ=1$ s. Extrapolation to advanced detectors implies $D\simeq 35-50$ Mpc for $h_n(f)\simeq 2\times 10^{-24}$ Hz$^{-\frac{1}{2}}$ around 1 kHz, which will open a new window to rigorous calorimetry on Kerr black holes.

gr-qc↗

arXiv2010

Nearby Supernova Rates from the Lick Observatory Supernova Search. IV. A Recovery Method for the Delay Time Distribution

The supernova (SN) delay-time distribution (DTD) - the SN rate versus time that would follow a brief burst of star formation - can shed light on SN progenitors, and on chemical enrichment timescales. Previous attempts to recover the DTD have used comparisons of mean SN rates vs. redshift to cosmic star-formation history (SFH), or comparison of SN rates among galaxies of different mean ages. We present an approach to recover the SN DTD that avoids such averaging. We compare the SFHs of individual galaxies to the numbers of SNe discovered in each galaxy (generally zero, sometimes one or a few SNe). We apply the method to a subsample of 3505 galaxies, hosting 82 SNe Ia and 119 core-collapse SNe (CC SNe), from the Lick Observatory SN Search (LOSS), with SFHs reconstructed from SDSS spectra. We find a >2sigma SN Ia DTD signal in our shortest-delay, "prompt", bin at <420 Myr. Despite a systematic error, due to the limited aperture of the SDSS spectroscopic fibres, which causes some of the prompt signal to leak to the later DTD bins, the data require prompt SNe Ia at the >99% confidence. We further find, at 4sigma, SNe Ia that are "delayed" by > 2.4 Gyr. Thus, the data support the existence of both prompt and delayed SNe Ia. The time integral over the CC SN DTD is 0.010+/-0.002 SNe per Msun, as expected if all stars of mass >8 Msun lead to visible SN explosions. This argues against a minimum mass for CC SNe of >10 Msun, and against a significant fraction of massive stars that collapse without exploding. For SNe Ia, the time-integrated DTD is 0.0023+/-0.0006 SNe per Msun formed, most of them with delays < 2.4 Gyr. We show, using simulations, that application of the method to the full existing LOSS sample, but with complete and unbiased SFH estimates for the survey galaxies, could provide a detailed measurement of the SN Ia DTD.

astro-ph.CO↗

arXiv2009

Prompt Ia Supernovae Are Significantly Delayed

The time delay between the formation of a population of stars and the onset of type Ia supernovae (SNe Ia) sets important limits on the masses and nature of SN Ia progenitors. Here we use a new observational technique to measure this time delay by comparing the spatial distributions of SNe Ia to their local environments. Previous work attempted such analyses encompassing the entire host of each SN Ia, yielding inconclusive results. Our approach confines the analysis only to the relevant portions of the hosts, allowing us to show that even so-called "prompt" SNe Ia that trace star-formation on cosmic timescales exhibit a significant delay time of 200-500 million years. This implies that either the majority of Ia companion stars have main-sequence masses less than 3 solar masses, or that most SNe Ia arise from double-white dwarf binaries. Our results are also consistent with a SNe Ia rate that traces the white dwarf formation rate, scaled by a fixed efficiency factor.

astro-ph.SR↗

arXiv2009

Nebular Phase Observations of the Type Ib Supernova 2008D/X-ray Transient 080109: Side-Viewed Bipolar Explosion

We present optical spectroscopic and photometric observations of supernova (SN) 2008D, associated with the luminous X-ray transient 080109, at >300 days after the explosion (nebular phases). We also give flux measurements of emission lines from the H II region at the site of the SN, and estimates of the local metallicity. The brightness of the SN at nebular phases is consistent with the prediction of the explosion models with an ejected 56Ni mass of 0.07 Msun, which explains the light curve at early phases. The [O I] line in the nebular spectrum shows a double-peaked profile while the [Ca II] line does not. The double-peaked [O I] profile strongly indicates that SN 2008D is an aspherical explosion. The profile can be explained by a torus-like distribution of oxygen viewed from near the plane of the torus. We suggest that SN 2008D is a side-viewed, bipolar explosion with a viewing angle of > 50^{\circ} from the polar direction.

astro-ph.HE↗

arXiv2009

Type II Supernovae as Probes of Cosmology

- Constraining the cosmological parameters and understanding Dark Energy have tremendous implications for the nature of the Universe and its physical laws. - The pervasive limit of systematic uncertainties reached by cosmography based on Cepheids and Type Ia supernovae (SNe Ia) warrants a search for complementary approaches. - Type II SNe have been shown to offer such a path. Their distances can be well constrained by luminosity-based or geometric methods. Competing, complementary, and concerted efforts are underway, to explore and exploit those objects that are extremely well matched to next generation facilities. Spectroscopic follow-up will be enabled by space- based and 20-40 meter class telescopes. - Some systematic uncertainties of Type II SNe, such as reddening by dust and metallicity effects, are bound to be different from those of SNe Ia. Their stellar progenitors are known, promising better leverage on cosmic evolution. In addition, their rate - which closely tracks the ongoing star formation rate - is expected to rise significantly with look- back time, ensuring an adequate supply of distant examples. - These data will competitively constrain the dark energy equation of state, allow the determination of the Hubble constant to 5%, and promote our understanding of the processes involved in the last dramatic phases of massive stellar evolution.

astro-ph.CO↗

arXiv2008

Using Spatial Distributions to Constrain Progenitors of Supernovae and Gamma Ray Bursts

We carry out a comprehensive theoretical examination of the relationship between the spatial distribution of optical transients and the properties of their progenitor stars. By constructing analytic models of star-forming galaxies and the evolution of stellar populations within them, we are able to place constraints on candidate progenitors for core-collapse supernovae (SNe), long-duration gamma ray bursts, and supernovae Ia. In particular we first construct models of spiral galaxies that reproduce observations of core-collapse SNe, and we use these models to constrain the minimum mass for SNe Ic progenitors to approximately 25 solar masses. Secondly, we lay out the parameters of a dwarf irregular galaxy model, which we use to show that the progenitors of long-duration gamma-ray bursts are likely to have masses above approximately 43 solar masses. Finally, we introduce a new method for constraining the time scale associated with SNe Ia and apply it to our spiral galaxy models to show how observations can better be analyzed to discriminate between the leading progenitor models for these objects.

astro-ph↗

arXiv2008

The metamorphosis of Supernova SN2008D/XRF080109: a link between Supernovae and GRBs/Hypernovae

The only supernovae (SNe) to have shown early gamma-ray or X-ray emission thus far are overenergetic, broad-lined Type Ic SNe (Hypernovae - HNe). Recently, SN 2008D shows several novel features: (i) weak XRF, (ii) an early, narrow optical peak, (iii) disappearance of the broad lines typical of SNIc HNe, (iv) development of He lines as in SNeIb. Detailed analysis shows that SN 2008D was not a normal SN: its explosion energy (KE ~ 6*10^{51} erg) and ejected mass (~7 Msun) are intermediate between normal SNeIbc and HNe. We derive that SN 2008D was originally a ~30Msun star. When it collapsed a black hole formed and a weak, mildly relativistic jet was produced, which caused the XRF. SN 2008D is probably among the weakest explosions that produce relativistic jets. Inner engine activity appears to be present whenever massive stars collapse to black holes.

astro-ph↗

arXiv2008

Transient Heavy Element Absorption Systems in Novae: Episodic Mass Ejection from the Secondary Star

A high-resolution spectroscopic survey of postoutburst novae reveals short-lived heavy element absorption systems in a majority of novae near maximum light, having expansion velocities of 400-1000 km/s and velocity dispersions between 35-350 km/s. A majority of systems are accelerated outwardly, and they all progressively weaken and disappear over timescales of weeks. A few of the systems having narrow, deeper absorption reveal a rich spectrum of singly ionized Sc, Ti, V, Cr, Fe, Sr, Y, Zr, and Ba lines. Analysis of the richest such system, in Nova LMC 2005, shows the excitation temperature to be 104 K and elements lighter than Fe to have abundance enhancements over solar values by up to an order of magnitude. The gas causing the absorption systems must be circumbinary and its origin is most likely mass ejection from the secondary star. The absorbing gas pre-exists the outburst and may represent episodic mass transfer events from the secondary star that initiate the nova outburst(s). If SNe Ia originate in single degenerate binaries, such absorption systems could be detectable before maximum light

astro-ph↗

arXiv2007

Type Ia Supernova Rates Near and Far

(ABRIDGED) Recently, three important observational results were established: (a) The evolution of the SNIa rate with redshift show that the rate rises up to z~0.8, when the Universe was 6.5 Gyr old, and decreases afterward. (b) The rate of supernova explosions of the different types as a function of the galaxy (B-K) and the galaxy mass shows a marked increase with the star formation activity. (c) The rate of SNIa in radio-loud galaxies is much higher than the rate measured in radio-quiet galaxies. On this basis we have discussed the distribution of the delay time (DTD) between the formation of a SNIa progenitor star and its explosion as a SNIa. Our analysis finds: i) models with long delay times, say 3-4 Gyr, cannot reproduce the dependence of the SNIa rate on the colors and on the radio-luminosity of the parent galaxies; ii) the dependence of the SNIa rate on the parent galaxy colors requires models with a wide DTD, spanning the interval 100 Myr to 10 Gyr; iii) the dependence on the parent galaxy radio-luminosity requires substantial production of SNIa at epochs earlier than 100 Myr after the birth of a given stellar generation; iv) the comparison between observed SN rates and a grid of theoretical "single-population" DTDs shows that only a few of them are marginally consistent with all observations; v) the present data are best matched by a bimodal DTD, in which about 50% of type Ia SNe ("prompt" SNIa) explode soon after their stellar birth, in a time of the order of 100 Myrs, while the remaining 50% ("tardy" SNIa) have a much wider distribution, well described by an exponential function with a decay time of about 3 Gyr. We discuss the cosmological implications of this result and make simple predictions.

astro-ph↗

arXiv2006

On the Rates of Gamma Ray Bursts and Type Ib/c Supernovae

We measure the local rates of ``low-luminosity'' (LL-GRBs, i.e. L<10^{48--49}erg/sec) and ``high-luminosity'' Gamma-ray Bursts (HL-GRBs). The values are in the range n0=100--1800 Gpc^(-3)yr^(-1) and n0=100--550 Gpc^(-3) yr^(-1), respectively, and the ratios to SNe-Ibc \sim 1%-9% and 0.4% -3%. These data may suggest the existence of two physically distinct classes of GRBs in which LL-GRBs are (intrinsically) more frequent events than HL-GRBs. However, with the present data we cannot exclude the possibility of a single population of GRBs which give rise to both an isotropic low-luminous emission (LL-GRBs: detectable only in nearby GRBs) and to a highly collimated high-luminous emission (HL-GRBs: detectable preferentially at high-z). We compute also the rate of SNe-Ibc characterized by broad-lined spectra (Hypernovae) and found it to be about 1.5\times 10^(-4)HNe yr^(-1) 10^(10) L_(B\odot) (i.e less than 10% of SNe-Ibc occurring in Spirals). This result implies that the ratio HL-GRBs/HNe is smaller than 1, possibly in the range 0.04--0.3. We have used the ratio between Hypernovae and LL-GRBs to constrain their beaming factor to f_b^(-1)\sim 10 or less.

astro-ph↗

arXiv2006

Supernova and GRB connection: Observations and Questions

We review the observational status of the supernova/gamma-ray burst connection. Present data suggest that SNe associated with GRBs form a heterogeneous class of objects including both bright and faint hypernovae and perhaps also `standard' Ib/c events. Evidence for association with other types of core-collapse SNe (e.g. IIn) is much weaker. After combining the local GRB rate with the local SN-Ibc rate and beaming estimates, we find the ratio GRB/SNe-Ibc in the range ~0.5-4%. In most SN/GRB associations so far discovered, the SN and GRB events appear to go off simultaneously. In some cases data do not exclude that the SN explosion may have preceded the GRB by a few days. Finally we discuss a number of novel questions started by recent cases of GRB-SN associations.

astro-ph↗

arXiv2006

Models for the Type Ic Hypernova SN 2003lw associated with GRB 031203

The Gamma-Ray Burst 031203 at a redshift z=0.1055 revealed a highly reddened Type Ic Supernova, SN 2003lw, in its afterglow light. This is the third well established case of a link between a long-duration GRB and a type Ic SN. The SN light curve is obtained subtracting the galaxy contribution and is modelled together with two spectra at near-maximum epochs. A red VLT grism 150I spectrum of the SN near peak is used to extend the spectral coverage, and in particular to constrain the uncertain reddening, the most likely value for which is E_{G+H}(B-V) about 1.07 +/- 0.05. Accounting for reddening, SN 2003lw is about 0.3 mag brighter than the prototypical GRB-SN 1998bw. Light curve models yield a 56Ni mass of about 0.55 solar mass. The optimal explosion model is somewhat more massive (ejecta mass about 13 solar mass) and energetic (kinetic energy about 6 times 10^52 erg) than the model for SN 1998bw, implying a massive progenitor (40 - 50 solar mass). The mass at high velocity is not very large (1.4 solar mass above 30000 km/s, but only 0.1 solar mass above 60000 km/s), but is sufficient to cause the observed broad lines. The similarity of SNe 2003lw and 1998bw and the weakness of their related GRBs, GRB031203 and GRB980425, suggest that both GRBs may be normal events viewed slightly off-axis or a weaker but possibly more frequent type of GRB.

astro-ph↗

arXiv2004

Chandra observations of the recurrent nova IM Nor

The recurrent nova IM Nor was observed twice in X-rays with Chandra ACIS-S, 1 and 6 months after the optical outburst. It was not detected in the first observation, with an upper limit on the X-ray luminosity in the 0.2-10 keV range L(x) < 4.8 x 10^(30) x (d/1 kpc)^2 erg s^(-1) (where d is the distance to the nova). Five months later, a hard X-ray source with L(x) = (1.4-2.5) x 10^(32) x (d/1 kpc)^2 erg s^(-1) was detected. The X-ray spectrum appears to be thermal, but we cannot rule out additional components due to unresolved emission lines. A blackbody component is likely to contribute to the observed spectrum, but it has bolometric luminosity L$_{\rm bol} = 2.5 x 10^(33) x (d/1 kpc)^2 erg s^(-1), therefore it is not sufficiently luminous to be due to a central white dwarf which is still burning hydrogen on the surface. An optical spectrum, taken 5 months post-outburst, indicates no intrinsic reddening of the ejecta. Therefore, we conclude that the shell had already become optically thin to supersoft X-rays, but nuclear burning had already turned off, or was in the process of turning off at this time. We discuss why this implies that recurrent novae, even the rare ones with long optical decays like IM Nor, indicating a large envelope mass, are not statistically significant as type Ia SN candidates.

astro-ph↗

arXiv2003

The rate and the origin of type Ia supernovae in radiogalaxies

An analysis of type Ia supernova (SNIa) events in early type galaxies from Evans et al (1989) database provides strong evidence that the rate of type Ia supernovae (SNe) in radio-loud galaxies is about 6 times higher than the rate measured in radio-quiet galaxies, i.e. SNIa-rate$(radio-loud galaxies)=0.47^{+0.23}_{-0.15} h^2_{50}$ SNe per century and per 10$^{10}$L$^{B}_\odot$ (SNU) as compared to SNIa-rate$(radio-quiet galaxies)\lsim 0.080 h^2_{50}$ SNU. The exact value of the enhancement is still rather uncertain, but is likely to be in the range $\sim 4-15$. We discuss the possible causes of this result and we conclude that that the enhancement of SNIa explosion rate in radio-loud galaxies has the same common origin as their being strong radio sources, but that there is no causality link between the two phenomena. We argue that repeated episodes of interaction and/or mergers of early type galaxies with dwarf companions are responsible for inducing both strong radio activity in $\sim$14% of early type galaxies, and the $\sim1$ Gyr old stellar population needed to supply an adequate number SNIa progenitors. Within this scenario we predict that the probability of detecting a core-collapse SN event in radio-loud elliptical galaxies amounts to about 4% of their SNIa events.

astro-ph↗

arXiv2002

Nova Populations

In this article we review the current status of the stellar population assignment for novae. Observations in the Milky Way and in external galaxies point out the existence of two nova populations: fast and bright novae, mainly originated from massive white dwarfs and associated with the `thin disk/spiral arm' stellar population, and slow and faint novae, originated from lighter white dwarfs and associated with `thick-disk/bulge' population.

astro-ph↗