I have a new type IIn supernova that I am interested in crowd sourcing a light curve for. For those of you not familiar with my past group efforts, I am primarily interested in type IIn SNE and supernova impostors. This current effort is similar to what I have done in the past for SN 2009ip, SN 2014G, and ASASSN-14il.
I am attaching the target information below. The goal here is to get a composite light curve to 0.05 mag sensitivity or better with a cadence of at least one measure every two days. I won't complain if we do better. I am going to ask everyone who is participating to contribute images in the Johnson V-band. But I would also welcome contributions in other standard filters particularly (in order of importance) B, I, and R. I also have an interest in getting spectra using filterwheel gratings (i.e. SA100 or SA200) for this object. I'll post over in the spectrscopy forum about that.
I would like to collect images that have been dark corrected and flat fielded. These are most helpful to me for removing observer dependent systematics. The data you take remains yours to report as you please if you want to submit on your own to AAVSO, VSNET or anywhere else you are free to do that. But I'd still like your images to try to put together the best possible composite light curve I can. We can arrange on an individual basis you will share images with me once you are "on board."
Let me know if you would like to be "in" on this campaign. Once I know you are in I will add you to an email list where you know everyone else who is contributing. That will give those of you who plan to use iTelescope or other services a chance to coordinate your plans with each other and ensure efficient coverage.
Here is the target information:
ASASSN-15lf
RA: 12:06:45.56
Dec: +67:09:24.00
Class: Type II-n
V mag about 16.2 on June 15 and 15.4 on June 19.
Host galaxy: NGC 4108 (this galaxy is pretty nearby, indicating this taget could potentially get much brighter)
Will try, John.
It is supposed to clear up tonight, and I have access to a Planewave CDK-17 with an SA-200 in the filter wheel. Unbinned spectral resolution is only 11 A/pixel, but I've gotten reasonable data on 15th mag stars before (though binned 2x2 at 21.8A/pixel), so we'll see if I can twease a useable spectrum out of this object. I should be able to squeeze this one in while waiting for Cygnus to rise -- good thing its so far north.
Clear skies,
Brad Vietje
Newbury, VT
www.nkaf.org
Will try, John.
It is supposed to clear up tonight, and I have access to a Planewave CDK-17 with an SA-200 in the filter wheel. Unbinned spectral resolution is only 11 A/pixel, but I've gotten reasonable data on 15th mag stars before (though binned 2x2 at 21.8A/pixel), so we'll see if I can twease a useable spectrum out of this object. I should be able to squeeze this one in while waiting for Cygnus to rise -- good thing its so far north.
Clear skies,
Brad Vietje
Newbury, VT
www.nkaf.org
One of the great things
Brad,
One of the great things about novae and supernovae is that the speeds invovled are so big that the spectra features are much broader and more recognizable in low resolution spectra. Also, I'm interested in figuring out what we could do with these filter wheel gratings for campaigns so anything is useful toward that end. The resolution you have sound like it will work just fine. Let me know if you get anything and we will setup a way to exchange files.
So I guess that means that the n suffix = narrow hydrogen absoption lines only means relatively narrow compared to othe type II SNe but still broad compared to those found in garden variety main sequence star atmospheres. Is that the gist of it?
Brad Walter WBY
Too many Brad's on this list.
That is correcty Brad. the "n" means narrow lines. But the narrow lines are typically in emission rather than absorption. Normally those narrow features are superimposed on top of the very broad (thousands of km/s) features that are typical of a supernova.
Ok So are the absorption lines coming from gas thrown off in the SN or is it from fast moving gas ejected prior to the explosion? Thousands of KM per sec would appear to be SN ejecta. Then would narrow emission lines be be non-thermal emissions from previously ejected gas?
Brad
Hello John
I am in New Hampshire and will have pretty much the same weather as Brad. It supposed to clear and I will give it a go. Also have SA200 gratting.
Gary
Thanks Gary!
The target for the last two nights remained pretty steady at V~15.5. Our wonderful sequence team has made a sequence for it and ASASSN-15lf is now also in VSX.
Hello
Reprocessed PT on this object from JD 7193. Got about 15.35(Ic) and 15.75(B&V), but doing Conventional PT, no extraction of the host. Used the 123 as Ref and 144 as the check. Transformed with TA237.
Clear Skies
Gary
I have attached a spectra if ASASSN-15lf. Its 5 images of 120 seconds each. Object at 15.7, so could use more exposure. I have a 12 inch telescope. If it clears I will do more. Thanks to John Martin who processed the spectra.
John says this shows its a Type II SN. The absorption at Ha and Hb, along with the emission lines there, suggest this is a type IIn.
Cross posted on Spectroscopy Forum
Gary
Hello
I got a run on ASASSN-15lf from Nantucket on the RC24 last night, along with a lot of moonlight. Have no SA-200 on this scope, so it was PT only. I got a short run in V and I on it, about 6 images. Lots of hi thin cirrus and low fog. It looks like 17 to 17.1 in V, without flatfielding, just using the simple Maxim Tool in the info window. Definitely fainter than the night before. On another rig and location, the night before I had it at about 16.1 in V.
I will get some fresh flats tonight and process the images fully.
It took 2 nights to get some flats. When I calibrated and used the Photometry tool in Maxim, I got the SN at about 16 in V.
Gary
i have treid two nights in the past week with my Mewlon 250 with no success. The combination of moon, bad transparency due to high atmospheric moisture and high dust content make the sky background as bright as the galaxy. I can't get a guide star with a 10 second exposure. I will keep trying but my observing conditions have been worse than anything on record. We haven't had a day without some rain in weeks.
Brad Walter, WBY
Just submitted 2 ensemble measures from Vphot. Data from Late Thursday night -- clear and relatively dry up here (northern VT) but the same nagging moonlight as everyone else. AAVSO reports attached.
My measures are somehow brighter than Gary's. Wonder if completing the transform process would address this? My earlier measures were done in MaxIm DL 5.18, so I figured using Vphot would at least level the process. Our Johnson-Cousins BVRI filters are made by Chroma Technologies, in Bellows Falls, VT. They make very highly-regarded filter sets (especially for quantative research in fluorochrome microscopy), so maybe their transmission is just a bit different than other filter sets(?)
I've attempted to go through the transform process a few months ago, and took a BVRI series of M-67 for this, but I never completed the process. I'm not convinced the process is quite as streamlined as it could be yet -- I was confused about what I should be doing at each step, got frustrated, and gave up for the time being. Could always return to it, but would like better guidance. If I have calibrated BVRI images, it sure would be nice to be able to feed them into a standard processor (Vphot?) and have transform coefficeints come out the other end, since I have no experience to guide me in eliminating outliers, etc.
'Nuff said for now,
Brad Vietje
Newbury, VT
Brad,
If you have BVRI images of M67 in VPHOT, share them with me (MGW) and I'll generate the coefficients for you. You can use them with TA in the future.
Gordon Myers
Holy Smokes -- Thank you! Will do.
Brad
Hello Brad
There is an easy way to do Transformations, thanks to George Silvis and Gordon Meyers. Gordon wrote an Ap that takes the instrumental mags from preferable VPHOT and calculates the Tx Coef, and plots it for you, and shows the line, and you can immediately see each outlier. Click on each outlier,it goes away, and a new BFSL is calculated and displayed.
You will want to use VPHOT to get the inst mags. The reason is that you can set up a sequence and save it. This is important because there will most likely be double stars in some apertures, and sometimes the aperture will jump to a nearby bright star, but a wrong one.
Once you like the coef in TG, you can save them into an .ini file. Then use George's Tranform Applier (TA). It reads the .ini file from TG, and you have it open an AAVSO Extended format file with your science in it, and Press "Process". It writes another AAVSO Extended Format file that you can save. It contains the transformed and raw values for you run. This file can be loaded into WebObs directly, and you are done.
It takes me less than 10 seconds to go from my AAVSO Ext file with untransformed data to the transformed file, and load to WebObs.Its real slick. Gordon sounds like he will determine your coef for you this time. You will eventually want to do this yourself. You are close enough by, that I would be glad to come over the Border sometime and give you a hand, in exchange for a tour of your wonderful observatory.
Gary
WGR