Galaxy Zoo Talk

High velocity star?

  • Ghost_Sheep_SWR by Ghost_Sheep_SWR

    Or double supernova, or solar object? Wildly guessing is fun!

    But seriously; how come the position of this 'star' is so far off in DECaLS in comparison to SDSS?
    Does this fall within a standard timeframe for star position movement?

    enter image description here

    http://skyserver.sdss.org/dr9/en/tools/explore/obj.asp?id=1237663542612459793

    Posted

  • Ghost_Sheep_SWR by Ghost_Sheep_SWR

    Doesn't seem like an artifact looking at shape, and present in DECaLS and SDSS. But also not visible in earlier SDSS imaging, maybe obscured?

    enter image description here

    http://skyserver.sdss.org/dr5/en/tools/chart/navi.asp?ra=337.710463&dec=-0.524184

    Posted

  • Budgieye by Budgieye moderator

    Let me think... This green object seems to have moved 2 " (2 arc-seconds) in 10? years. (0.2 arc-sec/yr ?)

    Hypervelocity star can move 0.19 arcsec/year , or 1.9 arcsec in 10 ish years.

    So this object could be a hypervelocity star?

    A fast moving neutron star? They are usually very blue, but magnetic white dwarfs are all sorts of funny colours.

    or

    Two unrecorded supernova, going off at different times? Green is the usual colour for a supernova in SDSS, and these are green.

    4.1 Supernova in Talk, Forum, SDSS The Legacy Survey: Stripe 82, and Galaxy Zoo: The Hunt for Supernova. BBC Stargazing Live Snapshot Supernova http://talk.galaxyzoo.org/#/boards/BGZ0000001/discussions/DGZ0000wrb?page=4&comment_id=53d8b997db90c7673f00101d

    Info on high velocity stars : white dwarf stars, neutron stars http://talk.galaxyzoo.org/#/boards/BGZ0000001/discussions/DGZ0000wrb?page=4&comment_id=53d8b9d1db90c76202001111

    Forum thread: Hyper-Velocity Stars Project by Lovethetropics http://www.galaxyzooforum.org/index.php?topic=276167.0

    Zooniverse Letters http://letters.zooniverse.org/ In-house publication of science results, Hypervelocity star project Zooites go off on a tangent with HVS by Love The Tropics 2012 "Abstract: A Hyper-Velocity Star is a star which has obtained galactic escape velocity. The existence of stars with this characteristic was first proposed in 1988. ..List of confirmed Hyper-Velocity Stars as of September 2009" in SDSS

    Just for interest: A catalog of northern stars with annual proper motions larger than 0.15" (LSPM-NORTH catalog). http://simbad.u-strasbg.fr/simbad/sim-id?submit=display&bibdisplay=refsum&bibyear1=1983&bibyear2=2015&Ident=%404002025&Name=NLTT+19480#lab_bib
    These are SIMBAD objects, and Ghost_Sheep_SWR's star is not a SIMBAD object, it is too dim

    Proper Motions
    Proper Motion is the apparent angular motion of a star across the sky with respect to more distant stars.

    * Typical proper motion is ~0.1 arcsec/year.
* Largest: 10.25 arcsec/yr (Barnard's Star).

    Hypervelocity star can move 0.19 arcsec/year

    Note: proper motion in SDSS page has been multiplied by 100 , Why? I dunno. But you have to divide proper motion by 100 to get arc-sec/year.

    Posted

  • Budgieye by Budgieye moderator

    calculating date of SDSS dr9 photo, under PhotoObj click Field

    mjd_u 5.2936148E4
    mjd_g 5.29361496E4
    mjd_r 5.29361463E4
    mjd_i 5.29361471E4
    mjd_z 5.29361488E4

    Get rid of exponent 52936.149
    http://www.csgnetwork.com/julianmodifdateconv.html

    date of photo 10-24-2003

    dr5 image 5.219725E4 52197.25 date of photo 10-15-2001

    DECaLS images released in May 2015, so maybe taken in 2014.

    Posted

  • Ghost_Sheep_SWR by Ghost_Sheep_SWR

    Supernova was my first thought, but then i saw the SDSS image and got confused, and no SN reference whatsoever

    So 2 arcsec / 10-ish years would be within range of a hypervelocity star. But with a difference of +/- 2 years between the SDSS images it should also be visible on SDSS DR5 image at roughly the same position. In combination with the green color my best guess is 2 supernova, ill tag it just in case, although seems improbable within this timeframe.

    EDIT reference image, cant find a date on this one, but recognised as star.

    enter image description here

    APOGEE image

    Is it possible for a hypervelocity star to go supernova?

    Posted

  • c_cld by c_cld

    1. Form Decals browser (sources checked) we get for the "star"

      Source RA,Dec = 337.7101, -0.5233

      Source type: P

      Mags: g=21.59, r=19.76, z=20.23

      Brick: 3376m005, Objid: 2589

      Number of exposures: g=4, r=4, z=4

    2. From SDSS DR9
      1237663542612459793
      we get

      STAR 337.70948196,-0.52366619

    3. Querying SQL command: select
      60*dbo.fDistanceArcMinEq(337.70948196,-0.52366619,337.7101, -0.5233)
      yields 2.586 arcsec!

    We don't know the date of DEcals images but it seems to me too far apart SDSS shot to imprint a much brighter persistence of an "hyperveloce" supernova.

    That's why I am dubious about the SDSS "star" which could be a "muffin" from the nearby star mag. 9 (id=1237663542612525074), the second less possible interpretation is two different supernovae.

    Posted

  • Ghost_Sheep_SWR by Ghost_Sheep_SWR

    Thank everyone for the information, i was confusing 2 different type of objects anyway.

    And without further imaging or spectrum i don't think we can't get anymore certainty about this object or objects.

    Posted