SN blast from 2014

https://www.legacysurvey.org//viewer/?ra=201.9889&dec=-31.0137&layer=ls-dr10-grz&zoom=15

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Oh, that’s cool – there are so many g- and z-band exposures containing the SN that the outlier-rejection doesn’t catch it!

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This is a very good candidate. You are lucky, it is a miracle that it is not seen before and reported yet with al those bots around.

Ine :stars::dizzy:

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What do you think reporting this?

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Yes, I could but first I have to report some of my own candidates. If I report, I have to know your real name.

Ine :stars::dizzy:

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Timothy Chris Snell

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My brother reported this candidate as: AT 2014ht as this SN blast candidate shown above.

I forgot he has a TNS account! :smiley:

He reported it as 31st mag? That cant be right…

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Hello,

I agree with Tom. The magnitude is absolutely wrong! This is not possible! The lower the number, the brighter the object. The object’s apparent magnitude is more likely between 16 or 20 A transient (supernova candidate) with an apparent mag of 31 is not possible)
How on earth did you guys come up with an apparent magnitude of 31??? :fearful: The limit is really between 14 and 25 and then I have taken a wide margin!
Also the band (filter) is wrong. It must be g-sloan instead of r-sloan. The transient is first visible on 2014-04-01 @ 06:23 in g-band. A really careless mistake!

The given magnitude in the DECaLS 10 catalog in g-band is 18.77. But to be sure I’ll do a calculation using APT and a reference target.

When I make a report. I always check it several times before reporting anything at all. It must also be scientifically justified. Sorry but IMHO this report is not a good example of accurate science!

Ine :stars::dizzy:

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Hello,

I calculated an apparent magnitude of 17.28 using APT (Aperture Photometry Tool) and reference star Gaia 6169768040223511552.

mag target = mag reference – 2.5 * log10(flux target / flux reference)
mag target = 18.65 - 2.5*log10(151969/38389)
mag target = 17.2761294839
Apparent magnitude target = approximately 17.28

And I calculated an Absolute magnitude with the transient’s Apparent magnitude and the luminosity distance of the host galaxy.

Apparent magnitude = 17.2761294839
Luminosity distance host galaxy = (m-M) = 36.48
17.2761294839 - 36.48 = -19.2038705161
Absolute magnitude = approximately -19.2

Ine :stars::dizzy:

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Great work Ine!

I agree with you, especially in the beginning I was very hesitant to submit, wondering if I got everything right (one reason I didn’t report transients where only APT was an option to get the magnitude) and as correct as possible.

Perhaps not many folks care much about a very inaccurate mag for an archival transient with no way to follow-up anymore but I can imagine if this happens often in the long run this might hurt the option for amateur astronomers to report themselves.

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Hi, thank you for pointing this out. I was calculating flux and not the absolute value. I may correct this at a later time. I was obviously using DECaLS DR10 catalog and under this page. If you see any errors, please reply to me. There were too many angular measurements and couldn’t figure out the right one.

I was first of all downloading the photometry tool but unfortunately the download doesn’t work. I get an error message.

In words, What is the angular measurement for flux?

This is the value of the g-band flux. Does the absolute value differ?
https://www.legacysurvey.org//viewer/ls-dr10-grz/cat?ralo=201.98797880906264&rahi=201.98997880906265&declo=-31.014727850241062&dechi=-31.01272785024106&objid=9929
flux_g 31.138578

Cheers!

The mags are listed towards the bottom of that list.

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This has now been corrected in the comment below. Thanks everyone!

You should NOT use the DR10 measurements for this, because those will average across the images the contain the SN and those that don’t contain the SN!

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No. I am using the absolute magnitudes from DR10 which are measurements are nearly identical to the object… I have to use the absolute magnitude to report this. The average magnitude is only for me to report this object.m SNe does not appear in other catalogs because it is a transient. Transients are deteted to bare minimum. It does not average.

Light from stars in all the galaxies last billions of years while supernovae usually last a few months. Photometry takes more than the supernova that has origionally poccured. This is why it is a good thing!

Averaging is good because it is VERY ACCURATE INFORMATION!

Hi,

I made that measurement and I am telling you that you should not use it!!

I’m not sure what you mean by “absolute magnitude” but I do not think it means what you think it means.

cheers,
dustin

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DR10 doesn’t give absolute magnitudes. It gives averaged apparent magnitudes.

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The difference between Apparent magnitude and Absolute magnitude explained in a simple way:

The Apparent magnitude is how we see a star in terms of brightness in the sky. The Absolute magnitude is the actual brightness of a star, the luminosity of a star. Two magnitude 1 stars as we see them can have different absolute magnitudes because one is further away than the other.

A star’s absolute luminosity, which is directly related to its luminosity, is the brightness a star would have if it were 10 parsecs (32.6 lightyears) away.

And the flux is an astronomical term that represents the amount of energy emitted by a star per square meter per second in a wavelength interval of 1 nanometer.

Regarding the report, in the report you only have to state the Apparent magnitude of the transient (supernova candidate). You may state the Absolute magnitude in the comments section of the photometry section, but it is not required.
Why would you want to make things so complicated when it is in fact quite easy! :thinking:

And even if it is an archival transient, a report simply has to be scientifically justified!

Ine :stars::dizzy:

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Strictly speaking, flux is just the amount of energy per unit of time per unit of area. There are many different units used.