So, if you look over to the right-hand side of this blog, there are a couple of new links, one pointing to my Twitter stream and the other pointing to my new Facebook profile. If you’re the kind of person who is interested in pursuing that sort of thing, feel free to chase down my ever thinning supply of worthwhile thoughts as they spread out in my increasingly deluded attempt to stay hip by belatedly jumping on long overworked netgen trends. (Yikes that’s a long sentence!)
Friday, November 28, 2008
Wednesday, November 26, 2008
Begging for Photons Part II: Finding the limit
So some poking about on websites has yielded some results... First, getting information out of NASA is definitely a “wheat from the chaff” kinda operation. NASA documentation is a bewildering blizzard of information presented in a format that probably made sense to the instrument designers, but is not end-user friendly. Eventually I managed to random-walk my way to an exposure-time calculator.
And this is where I typically meet my second challenge. The late-time spectra of supernovae are weird. They are dominated by line emission, but the lines are actually quite wide, something like about 1/10th of the spectral width of broad band photometric filters in the NIR. (Roughly 600 Angstroms or so for a line near 1.64 microns for the gear-heads out there). Now for several years I’ve been estimating the strength of the late-time emission lines in SNe Ia by extrapolating Peter Meikle’s absolute IR light curves from 100 days post max to the epoch of observation at around 1 year. For the extrapolation I assume that the late-time light curve fades at a rate consistent with the 77 day half-life of Cobalt-56, which is the dominant energy source in the ejecta. This gives me a rough H-band magnitude for the late-time epoch, and has been OK at predicting the strength of the emission, though I haven’t rigorously tested how accurate this is. (Probably not that accurate, I’d guess, but I don’t really have any other method).
Since this method gives me a broad-band magnitude, I then have to convert this to a line flux. Now flux points for broadband magnitudes are actually tabulated as flux densities (ie flux per unit wavelength rather than the actual integrated flux in the band pass). Thus I first have to convert the flux point to a total integrated band flux. If the flux calculation requires a total line flux, then I’m home and dry, but if it wants a flux density, then I have to divide the integrated flux by the width of the line before trying to go on with the calculation. I’ve run into both situations for different instruments, but for the NICMOS calculator it’s just integrated line flux, which is easier.
Then its a matter of choosing settings, clicking on radio buttons and filling in web-forms and after a bit of tweaking it appears that a 900 second exposure would detect my emission line at a S/N of about 1 for a supernova with a broad-band H-magnitude of about 23. That’s pretty good actually. It means I can probably go about 2-3 magnitudes fainter than my ground-based observations and still have some hope of getting enough of a detection to measure a Doppler shift. Hooray.
Now the next question: are there enough targets to make this an interesting program to run in the spring?
And this is where I typically meet my second challenge. The late-time spectra of supernovae are weird. They are dominated by line emission, but the lines are actually quite wide, something like about 1/10th of the spectral width of broad band photometric filters in the NIR. (Roughly 600 Angstroms or so for a line near 1.64 microns for the gear-heads out there). Now for several years I’ve been estimating the strength of the late-time emission lines in SNe Ia by extrapolating Peter Meikle’s absolute IR light curves from 100 days post max to the epoch of observation at around 1 year. For the extrapolation I assume that the late-time light curve fades at a rate consistent with the 77 day half-life of Cobalt-56, which is the dominant energy source in the ejecta. This gives me a rough H-band magnitude for the late-time epoch, and has been OK at predicting the strength of the emission, though I haven’t rigorously tested how accurate this is. (Probably not that accurate, I’d guess, but I don’t really have any other method).
Since this method gives me a broad-band magnitude, I then have to convert this to a line flux. Now flux points for broadband magnitudes are actually tabulated as flux densities (ie flux per unit wavelength rather than the actual integrated flux in the band pass). Thus I first have to convert the flux point to a total integrated band flux. If the flux calculation requires a total line flux, then I’m home and dry, but if it wants a flux density, then I have to divide the integrated flux by the width of the line before trying to go on with the calculation. I’ve run into both situations for different instruments, but for the NICMOS calculator it’s just integrated line flux, which is easier.
Then its a matter of choosing settings, clicking on radio buttons and filling in web-forms and after a bit of tweaking it appears that a 900 second exposure would detect my emission line at a S/N of about 1 for a supernova with a broad-band H-magnitude of about 23. That’s pretty good actually. It means I can probably go about 2-3 magnitudes fainter than my ground-based observations and still have some hope of getting enough of a detection to measure a Doppler shift. Hooray.
Now the next question: are there enough targets to make this an interesting program to run in the spring?
Begging for Photons
If you’re the type interested in peeking behind the curtains, read on:
In late September, the Hubble Space Telescope freaked out. The computer system responsible for transmitting data to the ground crashed. Thankfully, the telescope didn’t completely stop talking to the ground, but it took quite a while for the systems to come back on line. Now, thanks to NASA’s long held religious belief in redundancy, the telescope is once again taking data and transmitting the information back to hungry astronomers on the ground.
Now this failure happened just as NASA was making final preparations for the final servicing mission to HST. Since it wasn’t clear if they’d have to replace the communications electronics, NASA decided to delay the servicing mission again. (For reference, this servicing mission was originally scheduled to happen in 2003 and got sidelined in the aftermath of the Columbia disaster, so HST has been waiting for this visit for a *long* time!) Currently they’re guessing that the servicing mission will be sometime next spring.
Meanwhile, the last round of HST proposals for “Cycle 17” took place last winter and was explicitly expecting to use the new and refurbished instruments after the servicing mission. But that was assuming that the mission was going to be this last spring. It’s now been delayed at least a further year, and the observing queue for approved programs using the existing instruments is running dry. So they’ve put out an emergency call for proposals to fill in the time until the servicing mission. They are specifically looking for proposals which will either use a lot of time (>100 orbits) or “High risk/high gain” type proposals. So the gold rush is on to collect those photons which are about to “fall off the back of a truck,” and it’s time to dig up semi-crazy ideas for what to do with aging HST instruments.
Now one of the side effects of specializing in infrared observations of supernovae, is that while I’ve been able to come up with good uses for the large ground-based telescopes, it’s been much harder to come up with good HST programs. HST has an infrared instrument, but it’s frankly something of an underwhelming instrument. Its design was locked on the wrong side of the rapid development of infrared instrumentation in the 90s and by the time it was deployed, the detectors were well behind the standard for ground-based instrumentation. The field of view is pathetic, the detectors are tiny and noisy, and the sensitivity is nothing to write home about. It does have the advantage of being above the stupendous IR airglow, but even the image quality isn’t that much better than you can achieve with ground-based instruments and the new generation of laser-guide-star adaptive optics. Plus, my particular specialty has been largely spectroscopic science, and the spectroscopic capabilities of NICMOS are poor indeed. So, to date, I’ve largely dismissed NICMOS as useless, at least to me.
But now I’ve run into a different wall. It turns out that Type Ia supernovae have some very interesting behavior in the infrared at late times (roughly a year after the explosion). In particular, the late-time iron features show both a hollow (flat-topped) emission profile and are kinematically offset from the center of the explosion by several thousand kilometers per second. Unfortunately, observing these properties really pushes the sensitivity limits of the biggest telescopes on the planet. Even for supernovae in the nearest galaxies, I need to obtain spectra of objects which are several magnitudes fainter than the sky. These are observations so difficult it even impresses the guys trying to take spectra of type Ia supernovae halfway across the visible universe.
That’s all well and good, if it was easy it would already have been done, but now we’ve reached a point where it’s difficult to build on our successes. We have observed a small handful of objects using a fair bit of time on Subaru and Gemini. But now what we really need are observations of a couple of dozen objects to start looking at how these effects vary and broaden our results to the context of the general population of Type Ia supernovae. However, being limited to the nearest objects, we are stuck with asking for these observations an object or two at a time, and asking for a night or two of 8m time for each. And the TACs are understandably coming back with “what is one more spectrum going to do for you?.” So we’re trying to investigate other avenues. I’ve got a pilot proposal in with Rob Fesen & students to try and use optical data to get at the same science, which might help.
But while pondering these troubles at the SN meeting last week in Japan, I received the e-mail from SCScI announcing the new HST opportunity. So now the question is, can I use HST to learn something about more SNe Ia? My first crazy thought was to try and use the strange filter set on NICMOS to get “photometric redshifts”, using the flux ratios in neighboring filters to estimate the kinematic offsets of the iron lines. Fortunately, after a long night of sushi and sake (including the famously poisonous Fugu... it was a pretty fantastic meeting banquet), I came to my senses and remembered that NICMOS does have a rudimentary spectroscopic capability. The spectral resolution is pathetically low (about 1000 km/s) but in this case that’s actually a plus because it means I will be concentrating the faint emission into just a few pixels. So now it’s down to quantitative questions: (1) is NICMOS even sensitive enough to do this kind of observation, and (2) will I be able to push the observations out sufficiently far to measure an interesting number of supernovae?
To be continued....
In late September, the Hubble Space Telescope freaked out. The computer system responsible for transmitting data to the ground crashed. Thankfully, the telescope didn’t completely stop talking to the ground, but it took quite a while for the systems to come back on line. Now, thanks to NASA’s long held religious belief in redundancy, the telescope is once again taking data and transmitting the information back to hungry astronomers on the ground.
Now this failure happened just as NASA was making final preparations for the final servicing mission to HST. Since it wasn’t clear if they’d have to replace the communications electronics, NASA decided to delay the servicing mission again. (For reference, this servicing mission was originally scheduled to happen in 2003 and got sidelined in the aftermath of the Columbia disaster, so HST has been waiting for this visit for a *long* time!) Currently they’re guessing that the servicing mission will be sometime next spring.
Meanwhile, the last round of HST proposals for “Cycle 17” took place last winter and was explicitly expecting to use the new and refurbished instruments after the servicing mission. But that was assuming that the mission was going to be this last spring. It’s now been delayed at least a further year, and the observing queue for approved programs using the existing instruments is running dry. So they’ve put out an emergency call for proposals to fill in the time until the servicing mission. They are specifically looking for proposals which will either use a lot of time (>100 orbits) or “High risk/high gain” type proposals. So the gold rush is on to collect those photons which are about to “fall off the back of a truck,” and it’s time to dig up semi-crazy ideas for what to do with aging HST instruments.
Now one of the side effects of specializing in infrared observations of supernovae, is that while I’ve been able to come up with good uses for the large ground-based telescopes, it’s been much harder to come up with good HST programs. HST has an infrared instrument, but it’s frankly something of an underwhelming instrument. Its design was locked on the wrong side of the rapid development of infrared instrumentation in the 90s and by the time it was deployed, the detectors were well behind the standard for ground-based instrumentation. The field of view is pathetic, the detectors are tiny and noisy, and the sensitivity is nothing to write home about. It does have the advantage of being above the stupendous IR airglow, but even the image quality isn’t that much better than you can achieve with ground-based instruments and the new generation of laser-guide-star adaptive optics. Plus, my particular specialty has been largely spectroscopic science, and the spectroscopic capabilities of NICMOS are poor indeed. So, to date, I’ve largely dismissed NICMOS as useless, at least to me.
But now I’ve run into a different wall. It turns out that Type Ia supernovae have some very interesting behavior in the infrared at late times (roughly a year after the explosion). In particular, the late-time iron features show both a hollow (flat-topped) emission profile and are kinematically offset from the center of the explosion by several thousand kilometers per second. Unfortunately, observing these properties really pushes the sensitivity limits of the biggest telescopes on the planet. Even for supernovae in the nearest galaxies, I need to obtain spectra of objects which are several magnitudes fainter than the sky. These are observations so difficult it even impresses the guys trying to take spectra of type Ia supernovae halfway across the visible universe.
That’s all well and good, if it was easy it would already have been done, but now we’ve reached a point where it’s difficult to build on our successes. We have observed a small handful of objects using a fair bit of time on Subaru and Gemini. But now what we really need are observations of a couple of dozen objects to start looking at how these effects vary and broaden our results to the context of the general population of Type Ia supernovae. However, being limited to the nearest objects, we are stuck with asking for these observations an object or two at a time, and asking for a night or two of 8m time for each. And the TACs are understandably coming back with “what is one more spectrum going to do for you?.” So we’re trying to investigate other avenues. I’ve got a pilot proposal in with Rob Fesen & students to try and use optical data to get at the same science, which might help.
But while pondering these troubles at the SN meeting last week in Japan, I received the e-mail from SCScI announcing the new HST opportunity. So now the question is, can I use HST to learn something about more SNe Ia? My first crazy thought was to try and use the strange filter set on NICMOS to get “photometric redshifts”, using the flux ratios in neighboring filters to estimate the kinematic offsets of the iron lines. Fortunately, after a long night of sushi and sake (including the famously poisonous Fugu... it was a pretty fantastic meeting banquet), I came to my senses and remembered that NICMOS does have a rudimentary spectroscopic capability. The spectral resolution is pathetically low (about 1000 km/s) but in this case that’s actually a plus because it means I will be concentrating the faint emission into just a few pixels. So now it’s down to quantitative questions: (1) is NICMOS even sensitive enough to do this kind of observation, and (2) will I be able to push the observations out sufficiently far to measure an interesting number of supernovae?
To be continued....
Tuesday, November 25, 2008
Back in the Hurly Burly
Well, I’m newly back from Japan and in less time than it takes to shake off 14 hours of jet lag I’m back in the thick of being faculty. This time of year is really kind of a mess. The triple-whammy of Veterans day, Thanksgiving and finals really makes the last month of the semester something of a jumbled affair. Add to this the chaos of extra end-of-the-semester things like student thesis proposals, teaching evaluation forms, last-minutes committee meetings, and a bonus HST proposal (or two?) and it begins to look like a tasty soup indeed.
Ah well, with all this going on it’s obviously the ideal time to try and discover new ways to spend non-existent free time on the ‘net right? So, just before leaving for Tokyo, I got tagged by a voice from the past (Hi Keith :) ) who’d hunted me down and, among other things, told me that there’s a whole bunch of people that I used to know lurking on Facebook. And indeed, some quick poking around does seem to bear this out. So it seems that I may be sticking my toes into those waters as well.
Meanwhile I need to grade the last month of cosmology homework, invent next weeks last cosmology homework, invent some test questions for the astro seminar quiz, and other sundry teacher stuff. And perhaps write an HST proposal for the Cycle 16 extension using everyones least favorite infrared detector NICMOS. Oh and Tom Maccarone wrote me an email this morning (well morning my time, not his) asking me if I’d like to join him on an HST proposal based on a conversation we had like 2 years ago in Southampton. Sure... why not. Tom’s on facebook too... It’s a funny old world...
Ah well, with all this going on it’s obviously the ideal time to try and discover new ways to spend non-existent free time on the ‘net right? So, just before leaving for Tokyo, I got tagged by a voice from the past (Hi Keith :) ) who’d hunted me down and, among other things, told me that there’s a whole bunch of people that I used to know lurking on Facebook. And indeed, some quick poking around does seem to bear this out. So it seems that I may be sticking my toes into those waters as well.
Meanwhile I need to grade the last month of cosmology homework, invent next weeks last cosmology homework, invent some test questions for the astro seminar quiz, and other sundry teacher stuff. And perhaps write an HST proposal for the Cycle 16 extension using everyones least favorite infrared detector NICMOS. Oh and Tom Maccarone wrote me an email this morning (well morning my time, not his) asking me if I’d like to join him on an HST proposal based on a conversation we had like 2 years ago in Southampton. Sure... why not. Tom’s on facebook too... It’s a funny old world...
Tuesday, November 18, 2008
Not so live from Kashiwa anymore
So the great live blogging experiment hit a couple of predictable roadblocks this afternoon. First, of course, I had to give my own talk, and then I got distracted by a very interesting talk about the Cygnus Loop, and then another interesting discussion about Super-Chandrasekhar-mass Type Ia supernovae. Tomorrow morning I’m chairing the session, so that’s probably not a good time to be doing other things... Ah well. This is the way of experiments...
Had a lovely dinner with the overseas visitors at Ken’s apartment in Kashiwa with some lively conversation, and also had a nice chat earlier with Sergei Blinnikov. All in all a good day. Indeed, this trip has been a nice reminder that it would be nice to get back to being a scientist. I should try and make that happen somehow.
Had a lovely dinner with the overseas visitors at Ken’s apartment in Kashiwa with some lively conversation, and also had a nice chat earlier with Sergei Blinnikov. All in all a good day. Indeed, this trip has been a nice reminder that it would be nice to get back to being a scientist. I should try and make that happen somehow.
Monday, November 17, 2008
LiveBlogging the IPMU supernova workshop: Mamoru Doi
Distant SN Observations with Subaru
Planning to build a 6.5 m IR/Optical telescope in Atacama.
12 IAU SNe in one image! Doi et al. 2002.
Subaru XMM/Newton Deep Survey. Suprime-Cam BVRi’z’ Plus Xrays and NIR (UKIRT). 540 AGN, 400 SNe, 170 Variables, in 1 sq deg.
Delay time distribution. Totani et al 2008 (astro-ph) t^-0.5=-0.2 ... inconclusive so far.
Coming up... Hyper Suprime: 1.5 deg FOV to chase Dark Energy with weak lensing. 2011?
Sullivan et al 2007. Difference between reddening line and BDR in type Ias?
Some discussion here of low Rv again...
30 micron imaging with a 1 m from the ground?
15 Band imaging with dichroics... That’s a kinda crazy instrument, but sorta cool.
Planning to build a 6.5 m IR/Optical telescope in Atacama.
12 IAU SNe in one image! Doi et al. 2002.
Subaru XMM/Newton Deep Survey. Suprime-Cam BVRi’z’ Plus Xrays and NIR (UKIRT). 540 AGN, 400 SNe, 170 Variables, in 1 sq deg.
Delay time distribution. Totani et al 2008 (astro-ph) t^-0.5=-0.2 ... inconclusive so far.
Coming up... Hyper Suprime: 1.5 deg FOV to chase Dark Energy with weak lensing. 2011?
Sullivan et al 2007. Difference between reddening line and BDR in type Ias?
Some discussion here of low Rv again...
30 micron imaging with a 1 m from the ground?
15 Band imaging with dichroics... That’s a kinda crazy instrument, but sorta cool.
LiveBlogging the IPMU supernova workshop: Giuliano Pignata
Low Luminosity IIP SNe
99br... -13.5 mag?!
Low velocity too. Low Ni mass. Low MS mass...
SN 08bk. Very nice data set. A little bump in the LC just after drop off the plateau. 08bk and 99br very similar to one another.
99br... -13.5 mag?!
Low velocity too. Low Ni mass. Low MS mass...
SN 08bk. Very nice data set. A little bump in the LC just after drop off the plateau. 08bk and 99br very similar to one another.
LiveBlogging the IPMU supernova workshop: Mario Hamuy
Millennium Center for Supernova Science
What are they doing?: Refining distance indicators. Understanding SN physics. Nearby Supernova Search using robotic telescopes. Carry out a follow-up program.
CHASE: the supernova search. 6 40cm telescopes (4 working). 10% time... Sample about 1000 nearby galaxies, sampled every ~4 nights.
Oh look, they found a SN last night. 2 in 2007, 24 in 2008. Roughly 2 per month.
Buying their own telescope... 50 cm... Increase discovery rate... and or follow-up.
Follow-up... teamed up with Carnegie Supernova Project.
Yikes. CSP is killing us at LT.
104 Type Ia’s. They are doing very well. Hubble diagram.... sigma = 0.13-10.17 Using optical. Adding J reduces to 0.12
Hmmm.... Must rethink LT.
Rv low for both type Ia and type II SNe.
A type II “hypernova”? SN 2003bg... SN 2002gh. What the hell is that?
What are they doing?: Refining distance indicators. Understanding SN physics. Nearby Supernova Search using robotic telescopes. Carry out a follow-up program.
CHASE: the supernova search. 6 40cm telescopes (4 working). 10% time... Sample about 1000 nearby galaxies, sampled every ~4 nights.
Oh look, they found a SN last night. 2 in 2007, 24 in 2008. Roughly 2 per month.
Buying their own telescope... 50 cm... Increase discovery rate... and or follow-up.
Follow-up... teamed up with Carnegie Supernova Project.
Yikes. CSP is killing us at LT.
104 Type Ia’s. They are doing very well. Hubble diagram.... sigma = 0.13-10.17 Using optical. Adding J reduces to 0.12
Hmmm.... Must rethink LT.
Rv low for both type Ia and type II SNe.
A type II “hypernova”? SN 2003bg... SN 2002gh. What the hell is that?
LiveBlogging the IPMU supernova workshop: Itsuki Sakon
“Near- to Mid-Infrared observation of supernovae with AKARI/IRC”
AKARI. New IR Satellite. 70 cm telescope. IRC, near to mid IR. FIS for far IR. Launched Feb 22, 2006. Warm mission: 2008 June. NIR 2-5 micron imag & Spec.
An all sky survey... Covered 94% of the sky. Ishihara 08.
Pointed observations: 10 min integration. (Short!) Accepting proposals for warm missions. Roughly 20 micro Jy for NIR, and 100 for MIR... Lower in warm mode...
Spectra! 1.8 micron to 5.5 micron at 0.06 Prisim
2.5-5 at 0.0097 for grism. 0.1,0.2 mJy sensitivity.
06jc results: Peculiar Ib. Continuum excess, fading of red side of lines and increase of extinction. Spectra... Yikes source confusion. Spectrum sits across galaxy.
Probably not silicates... (Too bright) Probably amorphous carbon. 2 component model gives better fit. Perhaps pre-existing dust. Mention of Mattila et al 2008.
NEWSY.... Spectral Templates for nearby galaxies for subtractions...
AKARI. New IR Satellite. 70 cm telescope. IRC, near to mid IR. FIS for far IR. Launched Feb 22, 2006. Warm mission: 2008 June. NIR 2-5 micron imag & Spec.
An all sky survey... Covered 94% of the sky. Ishihara 08.
Pointed observations: 10 min integration. (Short!) Accepting proposals for warm missions. Roughly 20 micro Jy for NIR, and 100 for MIR... Lower in warm mode...
Spectra! 1.8 micron to 5.5 micron at 0.06 Prisim
2.5-5 at 0.0097 for grism. 0.1,0.2 mJy sensitivity.
06jc results: Peculiar Ib. Continuum excess, fading of red side of lines and increase of extinction. Spectra... Yikes source confusion. Spectrum sits across galaxy.
Probably not silicates... (Too bright) Probably amorphous carbon. 2 component model gives better fit. Perhaps pre-existing dust. Mention of Mattila et al 2008.
NEWSY.... Spectral Templates for nearby galaxies for subtractions...
LiveBlogging the IPMU supernova workshop: Nozomu Tominaga
Light curves of Type II Supernovae: Metallicity Dependencies.
“Discussion is Welcome... And conclusions may change after discussion”. Cute.
First talk by a member of the Subaru generation. Lots of young energetic Japanese astronomers here.
Light curves of Type IIs... characterized by the envelope mass and pre-sn radius... also metallicity. Type I: by Mej, M Ni, and E. LC Plateu, brighter and longer for larger Menv....
Difference btw SN Ibc and SN II? MS mass? Single vs Binary? Metallicity? Mass loss uncertain.. Can these be constrained just with MColor LCs? Stella, radn hydrocode from Blinnikov et al. Type IIs have weak metal lines and close to BB. Large PreSN radius so Rad Trans important...
Using code, explore effects of Energy, MS mass, and Metallicity. Progenitor models from Umeda & Nomoto 2005, Explosions 1,5,10,20 FOE. MS mass, 13,15, 18,20,25,30, Metallicity ... missed it...
Higher energy makes shorter and brighter plateaus.
Larger MS mass makes brighter and longer plateaus. Some discussion of the difference between input KE and actual result KE. Plateaus seem long... all are above 100 d which is near the long end of observations... Perhaps KE is too low?
Metallicity... Zero metallicity star is compact, but the rest have similar structures... Envelope mass has complicated relation to metallicity... some discussion between those responsible for the input models... Metallicity results: zero metallicity star has 87A-like light curve, Otherwise the trend is relativity weak for metallicities. However colors change significantly. Higher metallicity sne are redder. Higher metallicity means larger photospheric radii (larger opacity). Same structure, but larger radius so cooler.
Looking at shock breakout. For larger PreSN radius, longer shock breakout, higher total energy, but fainter and cooler.
Energy: Higher energies are brighter and bluer.
MS Mass: Larger mass makes the peak longer and color redder. Lifan asks where is Ly Alpha.. Its ionized. Very hot (300K +)
Metallicity: All similar except metal free, spectra very similar as well.. (not surprising if ionization is very high and opacity low.)
Sensitivity for seeing these things in S-Cam on Subaru. 30 Msun at z=2 possible in 1 hr? NIR on JWST, 10 ks observations, 10 sigma.... Discussion of how to find these things...
“Discussion is Welcome... And conclusions may change after discussion”. Cute.
First talk by a member of the Subaru generation. Lots of young energetic Japanese astronomers here.
Light curves of Type IIs... characterized by the envelope mass and pre-sn radius... also metallicity. Type I: by Mej, M Ni, and E. LC Plateu, brighter and longer for larger Menv....
Difference btw SN Ibc and SN II? MS mass? Single vs Binary? Metallicity? Mass loss uncertain.. Can these be constrained just with MColor LCs? Stella, radn hydrocode from Blinnikov et al. Type IIs have weak metal lines and close to BB. Large PreSN radius so Rad Trans important...
Using code, explore effects of Energy, MS mass, and Metallicity. Progenitor models from Umeda & Nomoto 2005, Explosions 1,5,10,20 FOE. MS mass, 13,15, 18,20,25,30, Metallicity ... missed it...
Higher energy makes shorter and brighter plateaus.
Larger MS mass makes brighter and longer plateaus. Some discussion of the difference between input KE and actual result KE. Plateaus seem long... all are above 100 d which is near the long end of observations... Perhaps KE is too low?
Metallicity... Zero metallicity star is compact, but the rest have similar structures... Envelope mass has complicated relation to metallicity... some discussion between those responsible for the input models... Metallicity results: zero metallicity star has 87A-like light curve, Otherwise the trend is relativity weak for metallicities. However colors change significantly. Higher metallicity sne are redder. Higher metallicity means larger photospheric radii (larger opacity). Same structure, but larger radius so cooler.
Looking at shock breakout. For larger PreSN radius, longer shock breakout, higher total energy, but fainter and cooler.
Energy: Higher energies are brighter and bluer.
MS Mass: Larger mass makes the peak longer and color redder. Lifan asks where is Ly Alpha.. Its ionized. Very hot (300K +)
Metallicity: All similar except metal free, spectra very similar as well.. (not surprising if ionization is very high and opacity low.)
Sensitivity for seeing these things in S-Cam on Subaru. 30 Msun at z=2 possible in 1 hr? NIR on JWST, 10 ks observations, 10 sigma.... Discussion of how to find these things...
Sunday, November 16, 2008
LiveBlogging the IPMU supernova workshop: Sergi Blinnikov
Radiative Shocks vs Other Models of the Most Luminous SNe
First messengers from core collapse: Neutrinos? Gravitational Waves, Radio Waves? (Early radio pulse?) (Bisnovati-Kogan et al, 1988 for SN 1987A) This speculation about a neutrino induced prompt radio pulse is kicking up a fair bit of discussion.
Shocks inside SNe. Computation of shock breakout. Optical depth ~10. Termination of shock acceleration... missed that... Ah. a plot of optical depth near shock breakout...
Formation of a thin shell at the outside. Chevalier and so on... shock interaction... Cold dense shell... Model for bright SNe: Chugai et al. 04, Woosley et al 07. Cold dense shell on the inside of large CS envelope. Shock cannot breakout completely for several years.... Dense shell is not adiabatic but nearly isothermal... 4 orders of magnitude in density jump...
Comparison to other models Radioactive needs very large Ni mass. 64FOE... Diffusion... Atmospheric....
06gy... 1 FOE in light. 2 orders of mag more than normal SN II. If radioactive, need large energy. Why xray low if shock.... missed some more...Something went by about entropy. Yikes, he’s just blowing past lots of stuff.
Back to the McCray diffusion model. Some referencing old Russian papers... Diffusion lengths are really much shorter... can’t make it fit.
Back to shocks.... Chugai again... Oh dear, Dessart & Hillier, et al.... density profiles not self consistent. Missed limb brightening effect due to shell.... Photospheric radius wrong...
Huge shells from PP instability producing large pulsations in ~100 Msun stars.
Conclusions: He prefers radiating shocks for energy production... poo-poos pure diffusion and pure atmospheric models...
Discussion... X-rays are self absorbed until later times.... Lifan complains about 1D vs 3D...
First messengers from core collapse: Neutrinos? Gravitational Waves, Radio Waves? (Early radio pulse?) (Bisnovati-Kogan et al, 1988 for SN 1987A) This speculation about a neutrino induced prompt radio pulse is kicking up a fair bit of discussion.
Shocks inside SNe. Computation of shock breakout. Optical depth ~10. Termination of shock acceleration... missed that... Ah. a plot of optical depth near shock breakout...
Formation of a thin shell at the outside. Chevalier and so on... shock interaction... Cold dense shell... Model for bright SNe: Chugai et al. 04, Woosley et al 07. Cold dense shell on the inside of large CS envelope. Shock cannot breakout completely for several years.... Dense shell is not adiabatic but nearly isothermal... 4 orders of magnitude in density jump...
Comparison to other models Radioactive needs very large Ni mass. 64FOE... Diffusion... Atmospheric....
06gy... 1 FOE in light. 2 orders of mag more than normal SN II. If radioactive, need large energy. Why xray low if shock.... missed some more...Something went by about entropy. Yikes, he’s just blowing past lots of stuff.
Back to the McCray diffusion model. Some referencing old Russian papers... Diffusion lengths are really much shorter... can’t make it fit.
Back to shocks.... Chugai again... Oh dear, Dessart & Hillier, et al.... density profiles not self consistent. Missed limb brightening effect due to shell.... Photospheric radius wrong...
Huge shells from PP instability producing large pulsations in ~100 Msun stars.
Conclusions: He prefers radiating shocks for energy production... poo-poos pure diffusion and pure atmospheric models...
Discussion... X-rays are self absorbed until later times.... Lifan complains about 1D vs 3D...
LiveBlogging the IPMU supernova workshop: Peter Nugent
11:25 Now we have Peter Nugent: SNe 1999as & 2007bi. Twin Pair Production SNe?
Bias in SN Searches: You find the kinds of things you’re looking for. KAIT, Zwicky & Amateurs: Targeting big galaxies. High-z searches. SNf and SDSS: Rolling searches.
SN 1999as: Search to find low z SNe using similar methods to high-z searches. ie. big fields not bright galaxies. SN 1999as found by NEAT. Something that showed up with nothing there.
Spectrum looks like a type Ibc. Some narrow features. Redshift of .1 Mag at max =-21.
Almost no evolution in spectral features over 25-55 days. Narrow features 1000 km/s wide at 10,000 km/s: Detached shell. Fe II and Ti II.
LC models: 5M Ni, Mtot = 50M, KE = 50 FOE.
Host spectrum: Metallicity < 1/3 Solar. Mv = -17.8
Other SNe like SN 1999as?: SN 2001bb Mabs = -17. Dropped like a rock. Similar spectrum with narrow Fe & Ti features.
No event like 99as, until....
SN factory: 10,000 images per night. 10% have 5sigma detections. Automated rejection tree knocks this down to 100 per night. Good at finding Type Ias.
Finding lots of Type Ias in low luminosity and low metallicity galaxies.
Deep Sky: 9 Years of data on the sky. Useful targeting aid. Allows the removal of distant AGN and variable stars.
SN 2007bi. Host Mg=-16.4 @ z=.127 Mv = -20.5. Like 99as. Slow decay LC at early times (again like 99as).
Prediscovery -50 d. (Would have been thrown out if known)
Why PPSN? Large 56Ni. Too much for “standard” mechanism. Large total mass. Large KE. Low Metallicy environment. What else could it be: CSM, but no smooth continuum and no narrow hydrogen....
Conclusions: What you find is what you get. These things have slow light curves and would get thrown out of Ia searches.
Discussion: Lots of questions about CSM interaction. Way to use interaction to power these things? What about lack of He in the spectra. Decay rate for 07bi consistent with Co decay... For a year!
Plug for the Palomar Transient Search. Coming in March.
Also. Both super Chandra SNe are in low metallicy galaxies.
Bias in SN Searches: You find the kinds of things you’re looking for. KAIT, Zwicky & Amateurs: Targeting big galaxies. High-z searches. SNf and SDSS: Rolling searches.
SN 1999as: Search to find low z SNe using similar methods to high-z searches. ie. big fields not bright galaxies. SN 1999as found by NEAT. Something that showed up with nothing there.
Spectrum looks like a type Ibc. Some narrow features. Redshift of .1 Mag at max =-21.
Almost no evolution in spectral features over 25-55 days. Narrow features 1000 km/s wide at 10,000 km/s: Detached shell. Fe II and Ti II.
LC models: 5M Ni, Mtot = 50M, KE = 50 FOE.
Host spectrum: Metallicity < 1/3 Solar. Mv = -17.8
Other SNe like SN 1999as?: SN 2001bb Mabs = -17. Dropped like a rock. Similar spectrum with narrow Fe & Ti features.
No event like 99as, until....
SN factory: 10,000 images per night. 10% have 5sigma detections. Automated rejection tree knocks this down to 100 per night. Good at finding Type Ias.
Finding lots of Type Ias in low luminosity and low metallicity galaxies.
Deep Sky: 9 Years of data on the sky. Useful targeting aid. Allows the removal of distant AGN and variable stars.
SN 2007bi. Host Mg=-16.4 @ z=.127 Mv = -20.5. Like 99as. Slow decay LC at early times (again like 99as).
Prediscovery -50 d. (Would have been thrown out if known)
Why PPSN? Large 56Ni. Too much for “standard” mechanism. Large total mass. Large KE. Low Metallicy environment. What else could it be: CSM, but no smooth continuum and no narrow hydrogen....
Conclusions: What you find is what you get. These things have slow light curves and would get thrown out of Ia searches.
Discussion: Lots of questions about CSM interaction. Way to use interaction to power these things? What about lack of He in the spectra. Decay rate for 07bi consistent with Co decay... For a year!
Plug for the Palomar Transient Search. Coming in March.
Also. Both super Chandra SNe are in low metallicy galaxies.
LiveBlogging the IMPU Supernova Workshop: What is this?
So I’m attending a workshop on supernovae at IPMU in Kashiwa, Japan, and instead of just passively watching, I thought I’d try and take notes on the talks in real time. So what you’re seeing here are my notes (pretty sketchy, sorry) of the meeting. I may also drop in some commentary if I feel inspired. Or perhaps I’ll just get tired of it and stop at some point. Time will tell.
One note already. The Mac fraction seems suspiciously large in the astronomy world, at least as far as laptops are concerned. Well above the rate they are seen in the wild. Peter Nugent is up next.
Of course, you can feel free to ignore all of this cryptic astrophysics nonsense.
One note already. The Mac fraction seems suspiciously large in the astronomy world, at least as far as laptops are concerned. Well above the rate they are seen in the wild. Peter Nugent is up next.
Of course, you can feel free to ignore all of this cryptic astrophysics nonsense.
LiveBlogging the IPMU Supernova meeting: Ken Nomoto
10:20
And we’re off. Ken Nomoto is going to tell us about the “Supernova-Progenitor Connection”.
Supernova density profile is highly dependent on the progenitor: Low mass have steeper envelopes.
8-10 Msun stars: Super AGB stars (Mcore > 1.07) ONeMg core collapse due to electron capture. At above 10.4 Msun, Ne burning is ignited (Ne flash) in degenerate core... leading to mass ejections? (Nomoto 1984) Origin of very bright type II supernovae (Woosley)?
Below 10 Msun: no Ne burning. Degenerate ONeMg core. MONeMg=1.35 Msun. Steep density gradient outside degenerate core.
Electron Capture on ONeMg core: (Miyaji et al. 1980) Electron capture reduces the degenerate electron gas support and leads to collapse. (Picture of Mg lizard eating the e-)
Kitaura et al. (2006) 9Msun star. Neutrino heating causes weak explosion in spherical model (.1FOE). Mej=0.014 Msun. Overproduction of 90Zr (Hoffman et al 2008).
Constraints on Ye (Wanajo et al 2008).
Pastorello et al 2008: Ultra-Faint SNe IIn? M85 OT2006-1 2008S. Also 1997bs, 1999br, etc. (Botticella et al. 2008, Prieto et al. 2008).
10-90 (60)Msun stars: Fe Core Collapse... Asphericity. Nomoto et al 06, Limongi et al 00: general agreement in heavy element production. Also Heger &Woosley 08, Umeda & Nomoto 02, Tominaga 08. Mixing and asymmetry. All differ significantly to observations of metal poor stars. (Cayrel et al 2004). Agreement improved by high energy (10 FOE) asymmetric (Mixed) explosion, Tominaga et al 2006). Jet induced nucleosynthesis (Tominaga et al again). Tominaga et al 2007
Main sequence mass vs Kinetic Energy. Fork diagram. Hypernova branch and Faint SN branch. Also MS mass vs Ni Mass. Again a forked diagram. Ib’s at the branching point?
Hamuy 2003: Trend in Mej & MNi vs E (FOE).
Wolf-Rayet connetion? Ib,Ic. Mass loss vs Angular Momentum loss. ?
SN 2008D. Ib’s bridging the gap between Hypernovae and normal SNe?
90-140 Msun stars: Instability in the core. Oscillations leading to Fe Core collapse. (Umeda & Nomoto) (Near e+e- instability region). 30FOE, 5Msun 56Ni (!)
140-300 Msun stars: Pair Production SNe. Don’t match metal poor stars? Interesting.
SN 2006gy. (13 Msun Ni mass!?!) CSM Interaction? 64FOE, 15M Ni? Light curve not like Pair production supernovae (Fast, not slow).
And we’re off. Ken Nomoto is going to tell us about the “Supernova-Progenitor Connection”.
Supernova density profile is highly dependent on the progenitor: Low mass have steeper envelopes.
8-10 Msun stars: Super AGB stars (Mcore > 1.07) ONeMg core collapse due to electron capture. At above 10.4 Msun, Ne burning is ignited (Ne flash) in degenerate core... leading to mass ejections? (Nomoto 1984) Origin of very bright type II supernovae (Woosley)?
Below 10 Msun: no Ne burning. Degenerate ONeMg core. MONeMg=1.35 Msun. Steep density gradient outside degenerate core.
Electron Capture on ONeMg core: (Miyaji et al. 1980) Electron capture reduces the degenerate electron gas support and leads to collapse. (Picture of Mg lizard eating the e-)
Kitaura et al. (2006) 9Msun star. Neutrino heating causes weak explosion in spherical model (.1FOE). Mej=0.014 Msun. Overproduction of 90Zr (Hoffman et al 2008).
Constraints on Ye (Wanajo et al 2008).
Pastorello et al 2008: Ultra-Faint SNe IIn? M85 OT2006-1 2008S. Also 1997bs, 1999br, etc. (Botticella et al. 2008, Prieto et al. 2008).
10-90 (60)Msun stars: Fe Core Collapse... Asphericity. Nomoto et al 06, Limongi et al 00: general agreement in heavy element production. Also Heger &Woosley 08, Umeda & Nomoto 02, Tominaga 08. Mixing and asymmetry. All differ significantly to observations of metal poor stars. (Cayrel et al 2004). Agreement improved by high energy (10 FOE) asymmetric (Mixed) explosion, Tominaga et al 2006). Jet induced nucleosynthesis (Tominaga et al again). Tominaga et al 2007
Main sequence mass vs Kinetic Energy. Fork diagram. Hypernova branch and Faint SN branch. Also MS mass vs Ni Mass. Again a forked diagram. Ib’s at the branching point?
Hamuy 2003: Trend in Mej & MNi vs E (FOE).
Wolf-Rayet connetion? Ib,Ic. Mass loss vs Angular Momentum loss. ?
SN 2008D. Ib’s bridging the gap between Hypernovae and normal SNe?
90-140 Msun stars: Instability in the core. Oscillations leading to Fe Core collapse. (Umeda & Nomoto) (Near e+e- instability region). 30FOE, 5Msun 56Ni (!)
140-300 Msun stars: Pair Production SNe. Don’t match metal poor stars? Interesting.
SN 2006gy. (13 Msun Ni mass!?!) CSM Interaction? 64FOE, 15M Ni? Light curve not like Pair production supernovae (Fast, not slow).
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