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March 2018 supernovae

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#1 StanH

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Posted 02 March 2018 - 11:09 PM

Want to let everyone know of a couple of potentially bright supernovae.

 

SN 2018yu is a Type Ia in NGC 1888.  This one lies in Lepus.  My image from tonight has it at 15.9.  It could peak around 13.7  https://www.flickr.c...N07/26713075768

 

AT 2018zd is an unknown type thus far in NGC 2146 as it was just discovered yesterday by Koichi Itagaki.  It lies in Camelopardalis.  This galaxy is closer than NGC 1888.  A type Ia could reach 11.4 with a core collapse around 13th magnitude.  My image tonight has it at 17.1.  As this supernova does not seem to be brightening as quickly as that in NGC 1888 it is more likely a core collapse event.  https://www.flickr.c...N07/26713075768

 

SN 2018gv in NGC 2525 is fading but should remain between 14.0 and 15.0 for at least the next week.

 

David Bishop's page shows SN 2018pv in NGC 3941 should be fading, Latest magnitude report to David Bishop's page is rather old at magnitude 12.7 on February 19. 

 

The last report on David Bishop's page for SN 2018oh in UGC 4780 is also old at 14.7 on February 18.  Probably below 15.0 now.

 

The last report on David Bishop's page for SN 2018gj in NGC 6217 is 15.1 on February 20.  Probably fainter than that now.


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#2 StanH

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Posted 03 March 2018 - 09:57 PM

Made an attempt to view SN 2018yu in NGC 1888 tonight with the 17.5-inch as I would estimate it to be about 15.1 based on last night's image.  Don't have my robotic image in yet to know how bright it is tonight.

 

Events conspired against me.  The next block south is the local college's baseball field.  So everything to the south is washed out.  I found the field, but could only suspect the galaxy.  By the time the lights were turned off around 8:22 p.m. local time, the field was well past the meridian.  It did not help that for the only place I could view the field over the next door tree causes one streetlight to shine directly in my eye and another too my back.  

 

With the lights off, NGC 1888 was not difficult at 202x.  It was an elongated glow oriented northwest to southeast.  NGC 1889 was a tiny, round glow in contact north of the core of NGC 1888.  The pair of galaxies was framed between two 10th magnitude stars northwest and southeast.  A 14th magnitude star lies just north-northwest of the galaxy and another 14th magnitude star south-southeast. At 304x at times the core of the two galaxies were readily resolved with that of NGC 1889 the brighter of the two.  Every once in a while a stellar object was suspected just off the northwestern tip of NGC 1888.  However, I could never hold it and I'm just not confident to claim detection.  Furthermore, I had no success in detecting the stars of 15.3 to 15.6 (V from APASS) west-southwest of the galaxy. Then at 8:39 p.m. clouds began coming in from the north.


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#3 Redbetter

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Posted 04 March 2018 - 05:59 AM

Thanks for starting the March thread, and with some new targets.  I hope that we can keep this going with monthly updates of new/some older targets and a place to check for an idea of what to search for in more detail on Bishop's excellent SN site.  

 

I realize that most of these are challenging or beyond medium apertures, but hopefully there are enough nuggets there for a few medium aperture targets throughout the year, and moderately large apertures should have at least one or two good targets each month.  Hey, I try with 60/80/110 mm refractors as appropriate to provide an idea of what might be possible, so it isn't like I am a complete aperture snob about this.  If ya got it, try it!



#4 StanH

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Posted 04 March 2018 - 10:03 AM

Turns out the rate of brightening for SN 2018yu in NGC 1888 has significantly decreased.  My image showed it at 15.6 last night.  No wonder I couldn't see it.  That means it probably won't get to 13.7 as my initial calculations indicated.  Double-checked the numbers from NED for the distance modulus and galactic extinction and that's what it comes to for a normal Type Ia.  Though the supernova lies seemingly off the edge of this nearly edge-on galaxy, perhaps there's enough material there dimming it a magnitude or more.  Wish I could afford a BVR series which should show if there is some extinction.

 

Maybe better luck with AT 2018zd in NGC 2146 as it measured 16.1 last night.  That's a full magnitude more than the night before.



#5 StanH

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Posted 05 March 2018 - 10:51 PM

Set up the 17.5-inch to take a look at AT 2017zd in NGC 2146.  Hadn't been able to get an image last night or tonight to see how much it brightened.  I am extremely shocked there has not been a posted spectrum to it yet.

 

First off, it took me about 25 minutes to starhop to the field.  Kept getting mixed up.  But once finding the field it was easy due to a group of bright stars and an arrowhead asterism pointing almost to the galaxy.  At 61x the galaxy was dimly visible.  At 304x only an oval to almost bar-shaped area probably just less than 2' long could be readily seen.  With averted vision the galaxy was very elongated northwest to southeast and perhaps 4' long.  In the field to the east of the galaxy is the arrowhead asterism.  Its point is a line of three stars of decreasing brightness towards the southeastern end of the galaxy.  The supernova lies east of the northwestern end of NGC 2146.  Could not see any extent of the galaxy to the supernova.  On my chart I had a line of three stars roughly paralleling the western side of the galaxy of 15.65V, 13.69V, and 14.78V.  The first star was very difficult with averted vision.  The brightness of the supernova lay between the 13.69 and 14.78 stars.  Of the tip to the arrowhead, the faintest star is 14.50V.  The supernova was brighter than that.  I estimated the supernova at 14.1.  Then compared the supernova to stars I did not have marked on the chart.  To the northwest is a right triangle of 14th magnitude stars.  The supernova seemed a shade fainter than the star nearest to it, but fainter than the star which marked the right angle.  Turns out from APASS these are 13.95V and 13.78V respectively so I'm fairly confident of my estimate of 14.1.  About 1' north of the supernova was an extremely faint star that rarely could be held.  It doesn't show in APASS.  However, my image from the other night has it at about 16.3.

 

Then forgot about trying for NGC 2146A and swung over to SN 2018gv in NGC 2525.  At 304x it has faded considerably.  Now it seemed slightly fainter than the star to its southwest which is 14.63V.

 

If you starhop to NGC 2146 like I did from Capella through Beta Cam and Alpha Cam, you ought to check out a few double stars so you don't have to back track like I did.  Beta Cam is a wide pair with the brighter star amber and the much fainter star blue.  11 Cam and 12 Cam are a wider pair, but are extremely pretty at blue and orange with not much difference in brightness, though the bluer one appeared brighter.  Then there's STI 2051.  I am indebted to Steve Gottlieb for posting about this recently, though I forgot where he posted it.  Anyway, this is a red dwarf and white dwarf pairing.  I've never seen a white dwarf.  I'm beginning to think I'll never see the Pup.  So I'm thrilled to have seen this pair and have now seen a white dwarf.  The brighter star is the red dwarf and it was orange.  At 304x the white dwarf was definitely a dirty white, but I can't really describe the color better than that.  


Edited by StanH, 05 March 2018 - 10:52 PM.


#6 sgottlieb

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Posted 06 March 2018 - 12:53 AM

STI 2051 was part of an observing report titled "Double the Fun" on DeepSkyForum and "Lake Sonoma on 2/13 and 2/15" on my own web site (Adventures in Deep Space).  I've stopped posting observing reports here because of restrictions on using labeled SDSS images.   But here's the post on STI 2051...

 

STEIN 2051
04 31 11.5 +58 58 37

V = 11.4/12.4; Separation 10"

 

This unusual 10" pair was discovered by Dutch Roman Catholic priest and astronomer Johan Stein in 1908. It consists of a mag 11.1 red dwarf (Stein 2051A) and a mag 12.4 white dwarf (Stein 2051B), at a distance of only 18 light years. This HST image shows only the white dwarf component (bluish color), along with a very close but distant field star. At 10” separation, the red and white dwarf pair were very easily resolved at 200x. The brighter red dwarf component on the southwestern side had a reddish hue with careful examination. The duo has a large proper motion, but is located ~9' E of mag 8.9 HD 28176.

 

Stein 2051 B is the 6th nearest white dwarf to the Sun after Sirius B, Procyon B, van Maanen's star, LP 145-141 and 40 Eridani B. Remarkably in 2017 Stein 2051B was observed using the HST passing in front of a more distant star about 5,000 light-years away. The HST news blurb reads…

 

"Looks can be deceiving. In this Hubble Space Telescope image, the white dwarf star Stein 2051 B and the smaller star below it appear to be close neighbors. The stars, however, reside far away from each other. Stein 2051 B is 17 light-years from Earth; the other star is about 5,000 light-years away.

 

Astronomers made the Hubble observations of the white dwarf, the burned-out core of a normal star, and the faint background star over a two-year period. Hubble observed the dead star passing in front of the background star, deflecting its light. During the close alignment, the distant starlight appeared offset by about 2 milliarcseconds from its actual position. This deviation is so small that it is equivalent to observing an ant crawl across the surface of a quarter from 1,500 miles away. From this measurement, astronomers calculated that the white dwarf's mass is roughly 68 percent of the sun's mass.”

 

The results were recently published by Sahu, Anderson, Casertano, Bond et al, in a paper titled "Relativistic deflection of background starlight measures the mass of a nearby white dwarf star". Here’s the abstract:

 

"Gravitational deflection of starlight around the Sun during the 1919 total solar eclipse provided measurements that confirmed Einstein’s general theory of relativity. We have used the Hubble Space Telescope to measure the analogous process of astrometric microlensing caused by a nearby star, the white dwarf Stein 2051 B. As Stein 2051 B passed closely in front of a background star, the background star’s position was deflected. Measurement of this deflection at multiple epochs allowed us to determine the mass of Stein 2051 B —the sixth nearest white dwarf to the Sun—as 0.675 ± 0.051 solar masses. This mass determination provides confirmation of the physics of degenerate matter and lends support to white dwarf evolutionary theory.”


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#7 StanH

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Posted 07 March 2018 - 10:42 PM

Steve, Thanks for reminding me where the post on the pair is and for the additional information.  I forgot to post the position.

 

Tonight was a mixed bag.  Saw three supernovae.  Had a horrible time with my imaging telescope.  Power kept going off when it would slew.  Was using a new power supply, too.

 

First off was SN 2018yu in NGC 1888.  No lights from the ballpark tonight.  Even with street lights shinging on me, the supernova was relatively easy to detect at 304x.  Estimated it at 14.6.  One time with averted vision the supernova and the stellar cores of NGC 1888 and NGC 1889 made a nice long right triangle with the core of NGC 1888 being the right angle.

 

SN 2018gv in NGC 2525 is faint.  Definitely more difficult than SN 2018yu.  It was fainter than the 14.6 star to its southwest.  Must be about 14.8.  Almost seemed as faint as the 3rd star in the line to the southwest.  Oddly, my images in Johnson V are running a little brighter than what I'm seeing visually.  

 

SN 2018zd in NGC 2146 continues to brighten.  Estimate seemed a bit trickier tonight, but it seemed to be about 13.8.  For this supernova my visual estimates are running brighter than Johnson V.  

 

Probably won't get my images processed until tomorrow night if not until the weekend.  Curious how SN 2018yu and SN 2018zd compare.  Unfortunately, with the problems getting my imaging telescope to work, SN 2018gv went behind the tree.  Good news was SN 2018yu was in a narrow gap between the tree and the power lines.


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#8 Vickx

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Posted 08 March 2018 - 03:40 PM

I observed 2018zd in NGC 2146 tonight (Mar 8.85 UT). I can confirm, it is really brightening very fast. I estimated it now as 13.7 mag.

Vic


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#9 StanH

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Posted 10 March 2018 - 11:22 PM

Viewed SN 2018yu in NGC 1888 and SN 2018zd in NGC 2146 tonight under poor conditions.  Also imaged both.  Pleased that my estimates matched closely to the Johnson V.

 

SN 2018yu appears to be similarly bright as the 14.20V star just south of the southeastern tip of NGC 1888.  So my estimate was 14.2.  On the resultant image it was 14.21V.  Recent photometries suggest it is very close to the peak.  Might go another half magnitude or so.  In actuality I was not too far off in calculating it could reach 13.7 with no host extinction.

 

SN 2018zd was estimated at 13.5 to 13.6.  On the image it was 13.52V.  It appears it is at maximum now.  This one has a storied history on TNS.  Right now it is classifed as a Type II supernova.  https://wis-tns.weiz...l/object/2018zd




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