Skip to main content

Post here if you are (or will be) measuring SN 2011fe

RHM's picture
RHM
Offline
Joined: 2011-03-04

I know that a number of people are contributing to the AAVSO's light curve of this supernova.  If you are one of them, please post the details of your setup here.  This may help us to figure out how to combine your data with that of others best, and it will also help new observers to figure out what they need to do the job.

I'll start: Michael Richmond, at the RIT Observatory in Rochester, NY.  I am using a 12-inch Meade LX-200 with SBIG ST-8E CCD camera and Johnson-Cousins BVRI filters.   I find that 60-second unguided exposures yield untrailed images about two-thirds of the time, so I take 10 or 15 images in each passband and analyze the 6-10 good ones.  Simple aperture photometry with a radius of 3-5 arcseconds seems to be adequate, so that's how I'm extracting magnitudes from the images.  I'm using the AAVSO's comparison stars from sequence 5249bgj.  You can find many details at the web pages I have written for each night's work -- look near the bottom of this page:

               http://stupendous.rit.edu/richmond/ritobs/ritobs.html

 

I've posted several
HOA's picture
HOA
Offline
Joined: 2011-03-09

I've posted several observations in the V-passband using an ST-9E camera. Telescope is an 11-inch SCT on an alt-az mount. Exposure durations are 20 seconds, and I typically stack 6-18 frames to get high signal-to-noise for photometry. At the object's relatively high northerly declination, tracking errors in unguided alt-az mode are less than at the celestial equator.

- Andy Howell

Setup for supernova imaging
HSW's picture
HSW
Offline
Joined: 2010-08-15

My name is Stan Howerton.  I image from my home in Arkansas City, Kansas.  In the past I've used remote imaging or my 8-inch SCT to image supernovae.  A 17.5-inch Dobsonian is normally used for making visual estimates.

I'm involved with a pro/am supernova search which I examine images online (this is NOT the Galaxy Zoo supernova search, though I have to admit to dabbling a bit with it).  When possible I then try to confirm discoveries with remote imaging or my equipment.

An 11-inch Celestron (CGEM1100) was purchased this summer to further pursue my interest in imaging supernovae.  The camera is an Orion StarShoot Deep Space Monochrome Imager II.

A 3.3 focal reducer is used to in order to get a large enough field for objects such as M51 or M101.  The field is 21.9' x 17.0' with a resolution of 1.75 arcseconds per pixel.

Thus far my only photometric filter is a Johnson V which was purchased from Astrodon.

Subs are usually 20 seconds in length with 15 to 30 stacked for a the final image.  Thus far I haven't figured out how to get a useful number of images without any trailing past 30 seconds.  I do not have autoguiding.

AIP4WIN is used for photometry.

Initially for M101 I was using some LONEOS stars shown in the software Guide 8.0 as I could center the galaxy and have comparison stars.  Lately I've been using a couple from an AAVSO chart, but that renders the center of the galaxy near one edge of the frame.

Images of the M101 supernova can be found here:  http://www.flickr.com/photos/watchingthesky/sets/72157627426040311

Re: Setup for supernova imaging
RHM's picture
RHM
Offline
Joined: 2011-03-04

Howdy, Stan!  Thanks very much for sending us your measurements.

When you write,

  "Initially for M101 I was using some LONEOS stars shown in the software Guide 8.0 as I could center the galaxy and have comparison stars.  Lately I've been using a couple from an AAVSO chart, but that renders the center of the galaxy near one edge of the frame."

do you mean that you have not been using the AAVSO sequence for the object?  If you go to AAVSO's "Variable Star Plotter" tool and enter the code for this object -- PTF11kly -- you should be given a chart like the one in my web page.  I just tried it now and was given a sequence of stars with identifier 5256atq.  If you use this sequence, you will have several stars right next to the supernova with known magnitudes which you can use as comparison stars; these are the stars labelled "A", "B", "C" on my little finding chart:

chart of the SN 2011fe field

 

Please do use these stars rather than the LONEOS ones if you can.

Re: Setup for supernova imaging
HSW's picture
HSW
Offline
Joined: 2010-08-15

Hi, Michael.

Part of the reason the LONEOS stars were used was the initial AAVSO notice said a comparison sequence was not yet made.  Furthermore, in the past, other than one of the stars near M51, they've appeared to give consistent and fairly accurate results when compared to stars on AAVSO charts.  So my earlier submitals for the supernova in M101 used those stars.

I am now using the AAVSO star 000-BKD-527 = 11.735V as my main comparison star.  The field of view won't allow me to get any brighter AAVSO stars than that in the same frame.   Incidently the AAVSO star 000-BKD-538 (15.475) is the same as my initial check star M101D (15.50).

Stan

setup for SN 2011FE
SHA's picture
SHA
Offline
Joined: 2010-07-29

I've been observing SN 2011FE (as well as SN 2011DH in M51) with the 24-inch Boller & Chivens telescope of the Michigan State University campus observatory.  The site is unfortunately not very dark, though that matters little for SN 2011FE right now, and the seeing is usually mediocre at best.  I'm observing in the B, V, and Cousins I bands with an Apogee Alta CCD.  At the monent I am just doing aperture photometry with an aperture of radius 5 arcsec.  For SN 2011FE I'm using the AAVSO sequence, although the formal uncertainties on some of the comparison stars are, at several hundredths of a magnitude, maybe a little larger than ideal.  I don't have a good pre-supernova image of M101, which probably doesn;t matter now but may when the supernova fades.

-Horace Smith

Sounds good, Horace.  I agree
RHM's picture
RHM
Offline
Joined: 2011-03-04

Sounds good, Horace.  I agree that the uncertainties in the AAVSO sequence aren't as small as I'd like, but if we use several of the stars together, it should be okay. 

I wouldn't worry about the simple aperture photometry; at this point, that's just fine.

Are you including color terms in your reductions?

Color Terms
SHA's picture
SHA
Offline
Joined: 2010-07-29

I have not included any color term reductions in my photometry.  Although I know the appropriate color terms to apply for ordinary stars, I do not know what is appropriate for a type Ia supernova.  I have worried that the emission features in the Ia spectrum might make the ordinary terms inappropriate, at least in the B and V passbands.  Do you whether the ordinary color terms are reasonable in this case?

Hi, Peter Lake (LPB)
lpb's picture
lpb
Offline
Joined: 2010-09-05

Hi,

Peter Lake (LPB) Planewave 0.51m (20inch) FLI PL11002M Class1 Johnson V Astrodon Filter, H06 New Mexico. Photometry VPHOT.


good question: when are color terms appropriate for SNe?
RHM's picture
RHM
Offline
Joined: 2011-03-04

(Short answer: please do apply color terms for now)

You are right to be concerned about the difference between ordinary stars and supernovae.  Supernovae have very different spectra than ordinary stars, so using color terms based on the properties of ordinary stars doesn't seem like a great idea.


The problem is largest at late times, starting a week or two after the supernova reaches maximum light.  As time goes by, the spectrum of the supernova becomes less like an ordinary star (which has roughly a blackbody spectrum) and more like that of a thin, hot gas (the spectrum of which is dominated by a few emission lines). 

At early times, however, when the supernova is still relatively compact and its gas is optically thick, its spectrum is not _too_ different from a blackbody; yes, there are some broad, strong emission lines and absorption lines, but there's also a pretty strong underlying continuum.  I'd say that for the time near maximum light, it's probably a better idea to apply the ordinary color terms than not to apply them.

What to do when the spectrum switches to that of a thin gas?   Gosh, I don't think there's a good answer.  In that case, it's just impossible to combine data from different instruments and hope to achieve agreement at the level of 2 or even 5 percent. 

I don't have their papers at
Matthew Templeton's picture
Matthew Templeton
Online
Joined: 2010-03-12

I don't have their papers at hand, but I think all of the supernova cosmology teams use template spectra to determine the ages of Ia.  I would guess the templates would show when they become optically thin and the emission lines turn on. 

I suspect that happens after peak -- I woudn't think it could be as bright if it goes optically thin.  That would mean most of the optical light would be coming out in emission lines.

Examples of spectra of ordinary Type Ia supernovae
RHM's picture
RHM
Offline
Joined: 2011-03-04

Here you go: a graph showing the spectrum of an ordinary Type Ia supernova at different times in its life.  These spectra are models created by Nugent et al., based on a number of real supernovae.  You can find Nugent's models at http://supernova.lbl.gov/~nugent/nugent_templates.html

 


spectra of ordinary type Ia SN

Setup for SN imaging
CNY's picture
CNY
Offline
Joined: 2010-07-23

I use an 11 year old 10" F6.3 LX200 w/ a focal reducer that gives nearly F4. I use the ST-8xme and V Johnson filter made by Schuler. I only have one measurement of SN 2011fe on 2011-8-30.0856UT. I do seperate flats for each target that I do photometry on, because sometimes I get some mirror flop as I move to a different target.

My measurement is the mean of 8 , 300 second exposures and the uncertainty is the standard deviation of the variable.

FITS are available on request and a JPEG can be found on the David Bishop website. (www.rochesterastronomy.com/snimages)

Astronomy is about to take a backseat for a little while as my wife is 36wks along with our second son. :) I may not even know the lunar phase for a few months.... hehehe.

---Andy Cason

Color terms
SHA's picture
SHA
Offline
Joined: 2010-07-29

OK, I will start applying color transformations to my measurements.  I suppose that we might eventually be able to compare the light curves with and without color terms and see whether they are yielding the hoped for improvement.  Now if the clouds would part...

Supernova 2011fe Spectroscopy
FMT's picture
FMT
Offline
Joined: 2010-08-14

Hi,

Note that a spectroscopic survey is realized by amateurs : the results are on Aras Web Page :

http://www.astrosurf.com/aras/surveys/supernovae/sn2011fe/obs.html

The blue continuum is strong.

Best regards

François Teyssier

My setup
rmu's picture
rmu
Offline
Joined: 2010-07-23

Miguel Rodríguez.

Ritchey-Chretien 8" f8. KAF-8300 monochrome based ccd camera. Astrodon B, V, R and I photometric filters. Exposure times depending on filter and sn brightness: from 120, 60 and 30 seconds in V and Rc, 150 and 120 seconds in B, and between 90 and 60 seconds in Ic.

Autoguiding was used for exposure times longer than 30 seconds. Two or three images are integrated for every filter and averaged. Average images are measured in vphot using 5249CHX, 5252IJ and 5252IS sequences.

My Setup
marco4variables's picture
marco4variables
Offline
Joined: 2011-09-06

Hi everbody

I'm working from north east Italy in order to follow up this beautiful SN. I've summarized my working conditions in the following images:

Usually I take 20 x 3 to 6 seconds images in order to reach 2/3 of CCD Full Well capacity and then I submit this mean image to Astrometrica, which gives the unfiltered V value for the mag.

All your comments are welcome!

Hi, I am Matt Bennett, a 15
mbennett's picture
mbennett
Offline
Joined: 2010-07-24

Hi, I am Matt Bennett, a 15 year old amature, and I will attempt to observe/image it with my meade etx 70 at (70 mm) telescope. I will be using a creative webcam with a 5 minute video and frames stacked. I dont think this plan is gonna work however. I have a pretty dark location maby I will be able to visually observe it.

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484