I am currently an Associate Specialist at UCSB and at LCOGT. But I will be soon a Assistant Research Physicist at UC Davis. My research interests is the study of Supernovae. My main interest is understanding how Stars end their life as Supernova. I am currently focusing my research activity on four aspects of these SNe:
Faint type I SNe: Theory suggests that the most massive stars with M >30M⊙ have cores which may form a black hole and the resulting explosion produces ejecta of low kinetic energy, a faint optical luminosity and a small mass fraction of radioactive nickel. An alternative origin for low-energy supernovae is the collapse of the oxygen-neon core of a star of 7-9 M⊙. In Valenti et al. Nature 2009, we report the first hydrogen- poor faint SN that could fit both theoretical scenarios. The issues on these objects are still open: what is their nature? are they core-collapse, BH forming, Ec-SNe or even thermonuclear? Which is the frequency of stars exploding trough this channel? In this contest, I’m currently studing three faint type I SNe: SN2012hn (Valenti et al 2014A), SN2010el (Valenti et al in preparation).
SNe in low metallicity host: Theory suggests that metallicity is a key parameter for stellar evolution, but so far there is a bias in discovering SNe mainly in luminous (metal rich) hosts. Metallicity has been proposed as a fundamental ingredient to make a stripped envelope SN produce a GRB. So far, statistical studies on environment metal- licity have been carried out only for SNe broad line Ic, and these have suggested that SNe-GRBs events occur mainly in low metallicity environments (Modjaz et al 2008). I plan to investigate which is the role of metallicity for Ib/c SNe. Through my collaborations, we have already started to study in details these SNe reporting the case of a bright SN Ic in a low luminous host that could be a pair-instability explosion (Young et al. 2010)
Normal Ib/c SNe have been identified for a long time with the first well studied SN Ic: SN 1994I. Recent studies of other SN Ib/c have shown that this SN does not represent the prototype of SNe Ib/c (not in the spectro-photometric behavior, nether in the physical parameters at the explosion epoch). This class of objects has to be characterized better enlarging the number of well studied objects. In this context I’m studying nearby normal stripped envelope SNe with wide data coverage (Valenti et al 2008, ApJL; Hunter et al 2009, MNRAS; Valenti et al 2011, MNRAS, Valenti et al. 2012 ApJL)
SNe-GRB connection: The occurrences of some stripped envelope SNe with some GRBs pointed out that the explosion of these events has to be strongly asymmetric. Whether or not all the stripped envelope SNe are strongly asymmetric or if the geometry of the explosion is the key to distinguish massive stars that produce a GRB from those that do not produce a GRB, is unclear. The similarities of some SNe without a GRB event with those occurred generating also a GRB add uncertainties to this issue. In this context, I’m studying the stripped envelope SNe, with similar characteristics to those associated to GRBs (Valenti et al MNRAS 2008; Mazzali et al. Science 2008) and nebular spectra of stripped envelope SNe to investigate the geometry of the explosion (Taubenberger et al MNRAS 2009)
Faint type I SNe: Theory suggests that the most massive stars with M >30M⊙ have cores which may form a black hole and the resulting explosion produces ejecta of low kinetic energy, a faint optical luminosity and a small mass fraction of radioactive nickel. An alternative origin for low-energy supernovae is the collapse of the oxygen-neon core of a star of 7-9 M⊙. In Valenti et al. Nature 2009, we report the first hydrogen- poor faint SN that could fit both theoretical scenarios. The issues on these objects are still open: what is their nature? are they core-collapse, BH forming, Ec-SNe or even thermonuclear? Which is the frequency of stars exploding trough this channel? In this contest, I’m currently studing three faint type I SNe: SN2012hn (Valenti et al 2014A), SN2010el (Valenti et al in preparation).
SNe in low metallicity host: Theory suggests that metallicity is a key parameter for stellar evolution, but so far there is a bias in discovering SNe mainly in luminous (metal rich) hosts. Metallicity has been proposed as a fundamental ingredient to make a stripped envelope SN produce a GRB. So far, statistical studies on environment metal- licity have been carried out only for SNe broad line Ic, and these have suggested that SNe-GRBs events occur mainly in low metallicity environments (Modjaz et al 2008). I plan to investigate which is the role of metallicity for Ib/c SNe. Through my collaborations, we have already started to study in details these SNe reporting the case of a bright SN Ic in a low luminous host that could be a pair-instability explosion (Young et al. 2010)
Normal Ib/c SNe have been identified for a long time with the first well studied SN Ic: SN 1994I. Recent studies of other SN Ib/c have shown that this SN does not represent the prototype of SNe Ib/c (not in the spectro-photometric behavior, nether in the physical parameters at the explosion epoch). This class of objects has to be characterized better enlarging the number of well studied objects. In this context I’m studying nearby normal stripped envelope SNe with wide data coverage (Valenti et al 2008, ApJL; Hunter et al 2009, MNRAS; Valenti et al 2011, MNRAS, Valenti et al. 2012 ApJL)
SNe-GRB connection: The occurrences of some stripped envelope SNe with some GRBs pointed out that the explosion of these events has to be strongly asymmetric. Whether or not all the stripped envelope SNe are strongly asymmetric or if the geometry of the explosion is the key to distinguish massive stars that produce a GRB from those that do not produce a GRB, is unclear. The similarities of some SNe without a GRB event with those occurred generating also a GRB add uncertainties to this issue. In this context, I’m studying the stripped envelope SNe, with similar characteristics to those associated to GRBs (Valenti et al MNRAS 2008; Mazzali et al. Science 2008) and nebular spectra of stripped envelope SNe to investigate the geometry of the explosion (Taubenberger et al MNRAS 2009)