NGC 1892

[jsmoraes]

Revendo este tópico e ainda intrigado com a aparente supernova, postei no forum Cloudy Nights pedindo confirmação. Lá, tive informação de que não havia nenhum registro de supernova na região. Foi-me sugerido entrar em contato com o grupo que realizou a captura.
Enviei email para um dos membros, Luis C Ho, e tive a seguinte resposta:

Luis C Ho escreveu

Dear Jorge,

Thanks for your email.  The CGS images of NGC 1892 were taken at Las Campanas on January 20, 2004, three years before yours.   You are right, there is a very bright object in the CGS image.  It's present in all of the filters observed, so it must be real.  It's so bright that it is saturated, and it has the same appearance as other bright stars in the field, so it is a point source.  At a distance of 16.6 Mpc, it must have been a supernova!

I cc this reply to my colleagues Aaron Barth and Zhao-Yu Li.

Luis

Ao que parece, na época não foi percebido a presença desta supernova, já que não havia fotos desta galáxia.

Muitos objetos do hemisfério sul não possuem fotos; a maioria dos telescópios sempre estiverem no hemisfério norte. E surpresas como esta são bem prováveis.

----------

Enviei email para rochesterastronomy.org perguntando sobre super nova na galáxia NGC 1892  e tive como resposta de Jim Seidewand and David Bishop:

rochesterastronomy.org escreveu

De: "David Bishop" <[e-mail]>
Para: [e-mail] [e-mail]

I don't records of any supernovae, novae, or LBVs in NGC 1892.
http://www.rochesterastronomy.org/snimages/archives.html

On 7/28/2018 8:57 AM, Jim Seidewand wrote:
> Dave Bishop is our supernova guru, so I copied him in here for any comments.
>
> Jim

Enviei email também para James Guillochon do Center for Astrophysics of Harvard-Smithsonian sobre esta possível super nova. E recebi a seguinte resposta:

James Guillochon escreveu

Hi Jorge,

Wow this is really cool, regardless of what the object may be.  Do you happen to have the exact RA/Dec of the object?

Some thoughts: it's possible we're looking at a solar system object that happened to cross in front of the galaxy in the Las Campanas image, one would have to check the image against the minor planet center's archive of planets to be sure. For that, we'll need the exact time the image was taken (not just the date), you probably want to ask the CGS people for that info.

Another possibility is a flaring star that was too dim for the Hubble image pre-flare. That might be a bit hard to rule out entirely, although the HST image seems pretty deep so you can probably rule out many flaring star candidates.

Lastly: it's close enough that we probably want to check the radio telescope archives for a source, if there is one at that position it would strongly suggest a supernova (the radio would be coming from the supernova remnant). I'll ask a friend of mine to check it out.

Cheers,
- James

Agora, é baixar o arquivo de Minor Planet para 20 de janeiro de 2004, configurar o Carte du Ciel para a data e local e verificar se houve algum asteroide ou cometa na região.

Por triangulação usando DSS2 do Aladim e Photoshop, eu encontrei as seguintes coordenadas:

RA: 05 17 11.70
DEC: -64 57 29.60

Graus e minutos estão com bastante precisão. Já segundos, podem ter erros no decimal. Portanto estariam entre:
11.00 à 12.00 para RA
29.00 à 30 para DEC

Havendo retorno do grupo CGS, veremos o quão preciso estão estas coordenadas.

----

James Guillochon solicitou coordenadas precisas do objeto. Eu enviei o resultado acima, e tive como resposta:

James Guillochon escreveu

That's a great help, I've checked SIMBAD and the transient catalogs and there appears to be no cataloged (stationary) objects in the vicinity:
http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=05%3A17%3A11.70+-64%3A57%3A29.60
https://api.astrocats.space/catalog?ra=05:17:11.70&dec=-64:57:29.60&radius=15

And, good news, the minor planet center has nothing either for that date (using their MPChecker tool):
"No known minor planets, brighter than V = 24.0, were found in the 5.0-arcminute region around R.A. = 05 17 11.70, Decl. = -64 57 29.60 (J2000.0) on 2004 01 20.50 UT."

Lastly, I checked two all-sky radio surveys: FIRST and NVSS. FIRST did not cover that part of the sky, but NVSS did roughly one month after the event, but no detection. Supernovae tend to get brighter in the radio for a few years after the event, so one month was probably not enough time to make it detectable if it was a supernova, so I wouldn't take that non-detection too seriously.

So that leaves either a previously unknown flaring star, or a legit supernova!

I think what would really seal the deal is a series of images around that time, which might be a bit difficult to dig up. Catalina potentially has more, but this object was pretty southern so that unfortunately makes options more limited (most telescopes are in the north). I'll contact some people at the CfA to see if it might be sitting in some historical images they have, but I wouldn't get too excited about that, I think the odds are low.

Exciting stuff!

-------

E por final, ou quase final, cheguei à impasse:

James Guillochon escreveu

Hi Jorge,

I've added an entry for this event to the OSC (giving it the name CGS2004A, for now), it will appear in our system by tomorrow night (our update script runs nightly). This will help collect data on the object in a central place. You'll notice I listed the type as "candidate" as I still think this object is not yet confirmed.

I looked at the CGS paper that presented the observations for this galaxy, and sadly all images were collected on the same night (Jan 20, 2004), although they were collected in four colors so that is still somewhat helpful. I think we need at least *one* more image while the supernova was active on a different date to be confident that it is real, *or* some late-time emission from the remnant, either in the X-rays or the radio.

My biggest worry is an M-dwarf flare: these stars are dim enough that not even HST would see them, but when they flare they can be very bright. The galaxy is a bit off the galactic plane so that is helpful (less stars when you're away from the Milky Way's disk), but there are still plenty of stars in the local neighborhood to worry about. That's why I think we need the second image and/or late-time emission.

By the way, I have an account on the TNS and can submit a discovery report on your behalf when/if we're confident the object is real. I think it makes sense for credit to be jointly shared by you and the CGS team, so we should pull them in the loop at some point.

Best,
- James

Ou seja: é preciso confirmação com alguma outra foto no período ou registro de radiação vindo do remanescente desta supernova para registro definitivo.
A galáxia fica nas redondezas da LMC... área pouco fotografada pelos colegas amadores. Nem na ESO encontrei fotos desta galáxia.

Achei na NASA, Nasa/Ipac Extragalactic Database, algumas fotos, inclusive de janeiro de 2004, mas data anterior ao da CGS. Em nenhuma delas há registro desta ocorrência ou deste objeto.

http://ned.ipac.caltech.edu/cgi-bin/imgdata?objname=NGC+1892&hconst=73.0&omegam=0.27&omegav=0.73&corr_z=1

------------

De Aaron Barth, membro da equipe CGS que fez a foto em 2004.

Aaron Barth escreveu

Hi James,
Thanks for getting in touch about this- it’s great that Jorge found this in our old images, and I agree that it’s likely a real SN although hard to prove this 14 years after the event. I’m copying Zhao-Yu Li on this email too.

It looks to me like the coordinates for the SN in our images are slightly different from what you listed.
From the pixel nearest to the center of the SN in our images, I am getting
05:17:11.53 -64:57:31.6
That should be good to precision of ~1 pixel or better, for pixel size of 0.26”. Those coordinates appear to be consistent across all 4 bands.

As for photometry: the SN is badly saturated in V, R, and I, so I’m not sure whether we can do much useful photometry. In B it might be just slightly saturated. The B-band seeing was not great, around 1.3”. From quick aperture photometry, it looks like the B-band magnitude of the SN was around 14.8. This would imply M_B ~ -16.2 (ignoring any extinction).

Unfortunately there’s probably not much more we can do with this- it may be that a rough B mag is the best we can do. It might not really be worth the trouble to try to do a host galaxy subtraction, unless there was a specific need for a more precise B magnitude at that one epoch. Given the limited information that we have, I don’t know if this really would justify a research note paper, unless you can think of anything else that we can do that might be useful to publish.

Thanks for taking a look at this!
Aaron

nota: minhas coordenadas foram encontradas utilizando superposição da imagem do Aladim-DSS2 e da imagem CGS-2004. Usei da ferramente de régua e meus olhos para efetuar uma triangulação e definir onde estaria na imagem Aladim.
Eu diria que tive uma boa precisão:

minhas coordenadas: 05:17:11.70 -64:57:29.60
coordenadas reais: 05:17:11.53 -64:57:31.60

Para RA, erro de 0.17" . Para DEC, erro de 2.0" . Eu estimei RA entre 11 e 12 segundos; para DEC entre 29 e 30 segundos.

Vai ser muito difícil a confirmação desta supernova sem uma outra foto. E como dito antes... na região das Nuvens de Magalhães ... 14 anos atrás ....

De qualquer forma está sendo uma boa tentativa.

------------
31/07/2018

Impressionante como James Guillochon está se esforçando para registrar esta supernova ! Muitos dias e horas de pesquisa e contato com diversos outros astrônomos e instituições para ter uma confirmação daquela ocorrência.

Eu diria que o mérito (ou crédito) pelo registro é dele.

Vai faltar-me palavras de agradecimento no final da novela. Embora eu vou tentar.

James Guillochon escreveu

"Hi Aaron,

Great, thanks for the additional info. I think the only chance that someone might have imaged this object recently would come from the OGLE survey, which has focused on the region around the LMC. I contacted Lukasz (head OGLE guy) about it and he'll look once he gets back from vacation.

I had a friend of mine check X-ray observations, Chandra had this object in its field a couple years ago, and there's no detection. Was worth a shot in case it was a IIL!

I think at the very least we should put out a discovery report on the TNS. Would it be OK to list the five CGS-Irvine folks as co-discoverers with Jorge? Anyone else I should list?

Best,
- James"

-------------

02/08/2018

James Guillochon escreveu

... all of the data on the event is now displayed on the OSC: https://sne.space/sne/CGS2004A/

Once the OGLE folks get back to me (hopefully in the next week) we can decide how to proceed from there. At the very least a TNS discovery report should be filed.

Cheers,
- James

-------------

13/08/2018

James Guillochon escreveu

Some updates on this:
- We had an astronomer use Magellan (6.5m telescope) to take an image of the galaxy last week. No detection at the nominal position of the supernova, but we're double-checking the exact coordinates before we know for sure.
- Another astronomer took a closer look at the HST data and it appears it was collected *before* the CGS image. That means we potentially have limits on the progenitor star, which can help us determine what kind of supernova this was.

As a result of these developments I am starting to put together a paper draft, listing you as one of the co-authors. Depending on how good our constraints on the progenitor star are it *might* be submitted to a refereed journal, but if not we'll do the unrefereed RNAAS and post the note to the ArXiv.

Are you OK with being included as an author? Could you send us the raw image file of the galaxy that you took?

Skeleton draft here, will be updated as data comes in: https://www.overleaf.com/18546403qtrgrwyjmbsq#/69902937/

Best,
- James

[Paulo Roberto Furlan]

Oi Jorge,

Comparei algumas fotos da NGC e realmente tudo indica que surgiu uma supernova nessa galáxia. E por ser pouco fotografada passou despercebido. Talvez, por ser um brasileiro que percebeu essa alteração eles demorem mais para confirmar. Mas vamos aguardar. Parabéns.

Paulo Furlan

[jsmoraes]

A falta de confirmação por outra foto ou medição de radiações vinda do remanescente está prejudicando o processo de registro.
Só temos uma única evidência. Apesar dos esforços na obtenção de dados de outras fontes, até agora nada foi obtido. A posição da galáxia, no hemisfério Sul e perto da Grande Nuvem de Magalhães dificulta as observações.

Do Rio de Janeiro até o Rio Grande do Sul, nós, brasileiros, temos uma boa visada da Grande Nuvem de Magalhães. Um privilégio. Mas poucos de nós fotografam ou registram seus objetos internos. Idem para Argentinos, Chile e Austrália.

A maioria das fotos se reduzem à nebulosa de Tarântula e uma vista panorâmica da galáxia.

Esta ocorrência reforça minhas intenções de continuar com os meus registros da região. Talvez eu esteja criando a única biblioteca de imagens amadora de seus objetos com boa resolução e detalhes.

[jsmoraes]

E, por fim, o último capitulo da novela.

O documento sobre a ocorrência foi aceito pela AAS e será publicado em seu períódico RNAAS.
Também foi aceito pela instituição que arquiva todos os documentos científicos arXiv.org
 https://arxiv.org/abs/1809.00163
arquivo PDF: https://arxiv.org/pdf/1809.00163.pdf

Arquivo 1809.pdf - Supernova CGS2004A

Está também em Open Supernova Catalog.  https://sne.space/sne/CGS2004A/