Angstrom Transient Alerts: 2008
From Angstrom
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ANG-08B-M31-01
ANG-08B-M31-01 is located at RA=00:42:48.5 Dec=+41:13:49.8 (J2000), 137.12" South and 52.12" East of the core of M31. No significant variation has been observed at this position through the past four M31 observing seasons. This event was observed at peak i'-band magnitude of 18.99±0.06 on October 20.02 2008 and was resolvable in a single 200s background subtracted image. Subsequent behaviour of the light-curve suggests this object may be either a nova or possibly a binary microlensing event.
 Reference image section, transient location circled |
 Discovery image section, transient location circled (observation from October 20th 2008) |
 LT lightcurve of ANG-08B-M31-01 |
ANG-08B-M31-02
ANG-08B-M31-02 is located at RA=00:42:56.4 Dec=+41:15:46.7 (J2000), 138.12" East and 18.21" South of the core of M31. Periodic lightcurve behaviour is seen throughout the previous four seasons, consistent with a long-period variable at or close to the position of this event. However a stronger and sharper peak in the i' band was observed to reach a maximum of mi=20.3±0.2 on November 07.81 2008 and was just resolvable in a stack of seven 200s images following background subtraction. The light-curve of this object suggests that it is likely to be due to microlensing with peak magnification occurring at MJD=54774.1±0.6 days and with a full width at half maximum duration of 7±3 days.
 Reference image section, ANG-08B-M31-02 bottom circle |
 Discovery image section, ANG-08B-M31-02 bottom circle (observation from November 7th 2008) |
 LT lightcurve of ANG-08B-M31-02 |
ANG-08B-M31-03
ANG-08B-M31-03 is located at RA=00:42:56.4 Dec=+41:16:18.1 (J2000), 137.15" East and 13.27" North of the core of M31. Periodic variation at or close to the position of this event has been observed throughout the previous four observing seasons. A stronger and sharper outburst was observed to peak at mi=18.74±0.05 in the i' band on November 07.81 2008 and was also just resolvable following background subtraction. This event shows a gradual rise consistent with microlensing rather than a nova but subsequent behaviour appears inconsistent with microlensing by a single lens.
Reference image section, ANG-08B-M31-03 top circle |
Discovery image section, ANG-08B-M31-03 top circle (observation from November 7th 2008) |
 LT lightcurve of ANG-08B-M31-03 |
ANG-08B-M31-04
ANG-08B-M31-04 is located at RA=00:42:57.3 Dec=+41:15:41.1 (J2000), 148."05 East and 33."52 South of the core of M31. Periodic light-curve behaviour is seen throughout the previous four Angstrom observing seasons, consistent with a long-period variable at or close to the position of this event. However a stronger and sharper peak in the i' band was observed to reach a maximum of mi=20.2±0.1 (provisional) on November 24.885 2008. The light-curve of this object suggests that it is likely to be an ongoing nova or possibly an exotic microlensing system.
 ANG-08B-M31-04: (left) LT i-band reference image section, (right) same region imaged on November 24th 2008; (centre) the corresponding difference image. The location of ANG-08B-M31-04 is highlighted by the green circle (click on image to enlarge). |
 LT i-band lightcurve for ANG-08B-M31-04 (click on image to enlarge). |
ANG-08B-M31-05
ANG-08B-M31-05 is located at RA=00:42:59.0 Dec=+41:17:15.5 (J2000), 164."06 East and 72."06 North of the core of M31. Periodic variation has been observed at this position through the past four Angstrom observing seasons. However the current rise is substantially stronger than previous variations. This event was observed with a magnitude of mi=20.4±0.1 (provisional) as of November 24.885. The current behaviour is consistent with microlensing with a full-width half-maximum time-scale of 30.43±1.89 days and a predicted peak occurring at MJD=54793.28±0.92 days.
 ANG-08B-M31-05: (left) LT i-band reference image section, (right) same region imaged on November 24th 2008; (centre) the corresponding difference image. The location of ANG-08B-M31-05 is highlighted by the green circle (click on image to enlarge). |
 LT i-band lightcurve for ANG-08B-M31-05 (click on image to enlarge). |
ANG-08B-M31-06
ANG-08B-M31-06 is located at RA=00:42:39.3, Dec=+41:16:54.9 (J2000), 56.3" West and 43.7" North of the core of M31. Periodic variation has been observed at this position through the past four Angstrom observing seasons due to a bright nearby variable. The current rise appears stronger than previous variations though the close proximity of the object to the M31 core means that it is visible only on difference images and so no reliable magnitude estimate is available. The current behaviour is consistent with microlensing with a full-width half-maximum time-scale of 19.2±1.2days and a predicted peak occurring at MJD=54795.04±0.50 days.
 ANG-08B-M31-06: (left) LT i-band reference image section, (right) same region imaged on November 28th 2008; (centre) the corresponding difference image. The location of ANG-08B-M31-06 is highlighted by the green circle (click on image to enlarge). |
 LT i-band lightcurve for ANG-08B-M31-06 (click on image to enlarge). |
ANG-08B-M31-07
ANG-08B-M31-07 is located at RA=00:42:42.8 Dec=+41:13:26.2 (J2000). Baseline behaviour appears to be flat through four seasons of Angstrom data (2004-2007) and a further four seasons of POINT-AGAPE legacy data (1999-2002). The current variation is relatively faint and no reliable baseline magnitude estimate is available. As at December 8.801 2008 (UTC) the light-curve of this object is rising and is consistent with an ongoing microlensing event but with a long predicted full-width half-maximum time-scale of 40±3 days and a predicted peak at MJD=54802.1±1.1 days.
 ANG-08B-M31-07: (left) LT i-band reference image section, (right) same region imaged on December 8.801 2008 (UTC); (centre) the corresponding difference image. The location of ANG-08B-M31-07 is highlighted by the green circle (click on image to enlarge). |
 LT i-band lightcurve for ANG-08B-M31-07 (click on image to enlarge). |
