Proposal not accepted?

Affiliation
American Association of Variable Star Observers (AAVSO)
Tue, 03/24/2015 - 02:37

I put in for a proposal on March 18 to attempt to determine the time of maximum for the supernova SNhunt281.  This is believed to be a subluminous Type Ia (http://www.astronomerstelegram.org/?read=7251) and is in a fairly nearby galaxy (NGC 5839) so it could reach 14th magnitude.  I had hoped through AAVSOnet to be able to get a fairly uninterrupted light curve of the rise and the initial fading.  The object may still be rising as my last data is 15.0V from a couple of nights ago.  However, I have been unable to get data on a regular basis or through the same band(s).

Did I make errors in my proposal?

Stan

Affiliation
American Association of Variable Star Observers (AAVSO)
I could BSM it

Hi Stan, If you cannot get the proposal, I have some free time and could image it whenever I have a clear night here with BSM-Hamren. It is a small telescope, but I could make some longer exposures in V, R or C, 120s, it may be enough to get a decent s/n at mag 14?

Let me know,

Mike

 

Affiliation
American Association of Variable Star Observers (AAVSO)
SN proposal

Hi Stan,

Your target was accepted and placed on the SRO queue.  Dirk probably didn't have time to tell you over the weekend.  However, it has been cloudy in AZ since the acceptance.  It finally cleared off late last night, so data should be collected tonight (Tuesday).

Arne

Affiliation
American Association of Variable Star Observers (AAVSO)
PSN J15053007+0138024

Looking at my 180sec 1x1 bin V exposure, PSN J15053007 looks as bright as the 14.563V magnitude comp star; see https://www.flickr.com/photos/watchingthesky/16681350779

Arne, to querry this photometric field in AASVO do we enter the whole name in this subject line, or do we just querry NGC 5839?  Thanks!

James 

Affiliation
American Association of Variable Star Observers (AAVSO)
SN proposal

Thanks Arne,

Even if the object was not accepted, I hope others might express interest in following the object.  Unlike many supernovae, this one is not embedded within the host galaxy and has sufficient offset to get good photometry.

So if anyone is interested SNhunt281 is located at 15h05m30.07s, +01d38m02.4s and is offset 39" east and 3" south of the center of NGC 5839.

ATel 7251 classified SNhunt281 as a subluminous Type Ia of the SN 1991bg variety.  This class typically has a maximum of 2 magnitudes fainter (absolute magnitude -17.3) than a typical Type Ia (absolute magnitude -19.3).  Per my proposal I expect the object to reach about magnitude 14.1.  The ATel states the object was believed to be about five days prior to max, but previous experience with this class of supernovae suggests such estimates can be greatly in error.  For instance SNhunt278 had the same classification.  ATel 7074 had it as one day past maximum, but my light curve showed it rising well after that date. However, I was unable to complete the light curve around maximum because I ran into scheduled conflicts, weather, etc. (see attached).  For that reason combined with SNhunt281 being in a closer galaxy I put in the proposal.

Stan

 

Affiliation
American Association of Variable Star Observers (AAVSO)
SN proposal

Stan,

Let us know if there any other comparison charts of this field; esp B & I.  I think AASVO will post a photometry chart for this, but as Arne mentions, they typically dont do faint SNs.  However, it looks like this one may crest 14th.  Its definetly brighter than mag 15v;  I would reduce it now, but I'm off to work......

James

Affiliation
American Association of Variable Star Observers (AAVSO)
SN Hunt proposal

James,

To get my comp charts for bright supernovae I go to the Aladin feature at VizieR and load the UCAC4 catalogue.  I then look for comparison stars with B-V from 0.3 to 0.8. 

Thus far I've only put together a chart for V:  https://www.flickr.com/photos/watchingthesky/16681350779

The 13.168V star might need to be not used as the Catalina Sky Surveys database suggests possible slight variation.

Aladin:  http://aladin.u-strasbg.fr/aladin.gml

Stan

Affiliation
American Association of Variable Star Observers (AAVSO)
SNhunt281 comp chart

To:  Stan,

Thanks alot!  Still don't know were to submit this, since there still isnt a VSX chart for this interesting SN.  Here is a (un-transformed) reduction of the BVI magnitudes of this NGC 5839 SN using your data:

http://www.astroimage.info/images/24-28Mar15.jpg

Hope AASVO makes a chart so I can transform the magnitudes and submit.  Good luck with your weather and thanks again for the reference star data!

James

Affiliation
American Association of Variable Star Observers (AAVSO)
SNhunt281 comp chart

To:  Stan,

Here is the spreadsheet I made with your photometry standards to use with my BVI data taken btw 24-28Mar15 on the SN in NGC 5839

http://www.astroimage.info/files/PSN%20J1505300%28FindChart%29.xls

Its funny how Ic seems to be at a plateu will B data; that seems too be brightning.  I wonder if these means the high energy component of the SN light is breaking through the dust/former emissions of the progenitor star.

James

Affiliation
American Association of Variable Star Observers (AAVSO)
SNhunt281

I want to thank AAVSO for the data on SNhunt281.  That data is much better than what I've been able to get with robotic telescopes.  Also want to thank James for what he has provided.

Noticed that SNhunt281 is now in the database.  I've added a few of the early data I was able to take as well as a couple of visual observations.  My visual estimates run a little high compared to the V data.  I've noticed that before when observing supernovae.  In this case I wonder if it is because the supernova is essentially the same brightness from B through R and since the eye is not limited to a single band that makes it appear brighter.  Another factor is the eye I use is blue sensitive.

Looks like it may finally be peaking after sixteen days since discovery.  From the SRO data I have it at 13.82V last night.  I'm hoping it will get an official SN designation soon, but for whatever reason this year, the IAU has done so for only six supernovae to this point.

Stan

Affiliation
American Association of Variable Star Observers (AAVSO)
SN proposal

Arne,

How do I access the data?  The ftp link I have has a folder for me, but as of the moment no data.

Stan

Affiliation
American Association of Variable Star Observers (AAVSO)
SNhunt281

Arne,

Looks like the images are complete as none have been made available since my original April 4 cutouff.  However, in the comments section of my proposal I had added a request to continue into mid-April.  Even if it is too late now, I got what I was needing.  It's my own fault for not requesting a longer run to begin with.

I really appreciate and wish to thank those at the various observatories who took the time to get the data.

Stan

Affiliation
American Association of Variable Star Observers (AAVSO)
SNhunt281

To:  Stan,

RE:"I really appreciate and wish to thank those at the various observatories who took the time to get the data."

I'm going to re-process my data and submit it based on the VSX chart for SNhunt281.  Thanks for your direction on shooting this neat SN variable Stan!

James

Affiliation
American Association of Variable Star Observers (AAVSO)
BSM Observations

Hi Mike,

Stan's target was way too faint for a BSM.  Plus, being a supernova, it is embedded in a galaxy where angular resolution is needed to obtain decent photometry.

When an AAVSOnet proposal is submitted, there is discussion within the TAC of the proposal, not only of its scientific merit, but also the feasability of making the observation.  In many cases, we extend the observations, obtaining more nights, higher cadence, more filters, deeper exposures or whatever, based on what we feel will make a good dataset not only for the current proposer but for any future researcher.

In this case, we were dealing with a 17th magnitude supernova that would get brighter since it was discovered prior to maximum light, but we don't knowi how much brighter.  Then you would want to follow it as long as possible as it got faint.  Therefore, the target was assigned to one of the bigger telescopes: OC61, TMO61 or SRO.  OC61 is currently busy doing time series for two researchers, though it frees up after tomorrow.  TMO61 is having communication problems and is unreliable (though getting better).  In addition, it and SRO have been experiencing a particularly cloudy spring, with the latest front passing through last night.  It looks to be clear for a couple of days, and so we can finally schedule the monitoring observations.

I've discussed with Bob Denny the option of building a master scheduler that could control all of the AAVSOnet telescopes, moving targets from one telescope to another based on availability and priority.  Now that I'm retired, I may open those discussions again!

Arne

Affiliation
American Association of Variable Star Observers (AAVSO)
AAVSO query

Hi James,

Any observation that goes into the International Database has to have an object AUID attached to it.  This means that the object is then also in VSX, and would then have a number of name aliases available.  So accessing it depends on whether you want the observation, the light curve, the VSX information, a finding chart, etc.  Your question is ambiguous to me as to which of these you want.

The AAVSO has traditionally NOT added extragalactic objects to VSP unless a researcher specifically requests an entry so that he/she can submit observations.  Therefore, the NGC catalog is not useful in searches such as displaying a finding chart since it is not in VSX.  The PSN designation is also not useful, unless the object was entered with that name into VSX and has an AUID.  For finding charts, I usually just enter the RA/DEC coordinates, and for extragalactic targets, select the DSS option.  I also go to the SN webpage maintained at the University of Rochester:

http://www.rochesterastronomy.org/snimages/

to look at an actual image with the supernova be sure of the identification.  Extragalactic objects are not added to VSX for several reasons.  One such reason is the difficulty in unambigously identifying the object - at minimum, a deep high resolution CCD finding chart, preferably when the object has faded a bit,  is required.  There have been cases of supernovae occurring in galaxies within an arcsec or two of a prior one, for example.

If you think an extragalactic object may already be entered into VSX, go to its search page and enter the object's coordinates.  If it is entered, you will get the VSX page with its primary name and any aliases.

Arne

 

Affiliation
American Association of Variable Star Observers (AAVSO)
Coker30 calibration frames

I was notifed of data from last night. Some trailing, but some of the images look usable.  Looks like Coker30 was used.  Images don't appear to be calibrated.  In the ftp there are several sets of calibration frames.  How do I find the correct ones?

Stan
 

Affiliation
American Association of Variable Star Observers (AAVSO)
coker30 calibration

Hi Sam,

The coker30 images are calibrated; why do you think they are not?  All AAVSOnet images are dark subtracted and flatfielded.

You also have some SRO data from 150325, as well as from last night.  However, those images don't seem to have transferred to your account.  I'll check with Matt and Doc on Monday to find out why.

Arne

Affiliation
American Association of Variable Star Observers (AAVSO)
coker30 calibration

Hi Arne,

The coker30 images had a lot of noise in them (please see attached).  Also, when going through the FITS header I didn't find anything about being calibrated.

Thanks for your help.

Stan

Affiliation
American Association of Variable Star Observers (AAVSO)
coker30 images

Hi Stan,

A couple of things.  First, all images are processed in 32-bit floating point with IRAF.  At the end of the pipeline, they are converted back into 16-bit integer.  FITS uses the parameters BZERO and BSCALE to fit the 32-bit value as best as possible into the 16-bit space.  Because darks are subtracted, there will be negative values in your image.  Some programs, such as MaximDL, assume all values are positive, and so will display the negative values as near-maximum (bright) positive values.  If you are using MaximDL, look for an additive offset value and use -500 for that value.  That will most likely make the "noise" look like it should.  That said, the STL-1001E uses the Kodak chip with the biggest pixels, but also with the highest dark current and noisiest background.  So there will be increased noise compared with some other sensors.

Second, because these are processed with IRAF, some non-standard keywords that you might be looking for to indicate processing may not be present.  If you look at the header, and go near the bottom, you will see that there are keywords that indicate dark subtraction and flatfielding have taken place; they are perhaps different than the ones you are expecting.

Arne

Affiliation
American Association of Variable Star Observers (AAVSO)
coker30 images

Hi Arne,

Thanks for the info.  Sure enough, there's something in the header different that what I am used to seeing.  Even so I should have seen it.  Sometimes I feel like such an idiot.

Am looking forward for the additional data.  

Also, one other question on the coker30 images.  For the red it says the filter is sr.  Is that the SDSS r filter instead of Rc?

Stan

Affiliation
American Association of Variable Star Observers (AAVSO)
SR filter

Hi Stan,

Yep, sorry, I should have mentioned the red filter.  Coker30 has both Cousins Rc and Sloan r' (SR).  However, SRO and OC61 (the other telescopes from which you might get data) only have SR.  So to keep everything consistent, I'm giving you B,V,SR.  Note that r' and Rc are pretty similar, so you can easily transform from one to the other.

Arne

Affiliation
American Association of Variable Star Observers (AAVSO)
SN images

HI Stan,

Your SN is still on the SRO queue; it has been cloudy in Arizona.  In addition, there have been a couple of priority projects (such as AM Her) that have taken precedence on the couple of clearish nights.  You should continue to get data for a while.

Arne

Affiliation
British Astronomical Association, Variable Star Section (BAA-VSS)
snhunt281 also a target for spectroscopy

This could also be a target for the scopes fitted with the new SA200 diffraction gratings. Here is a recent (20150412) quick spectrum using my ALPY spectrograph modified for low (~50A) resolution, confirming the 1a classification (~13 days after maximum) using GELATO

 

Robin