[Kepler]

The Kepler Asteroseismic Science Operations Center provides asteroseismological data from the NASA Kepler mission to astronomers who are members of the Kepler Asteroseismic Science Consortium (KASC).

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News

14th Jan 2016: IMPORTANT: Older data releases re-introduces timing error

With the errors found in the latest data release 24 short cadence data, we have implemented filters that will per-default disregard these data in the searches you perform on the KASOC website, and in the data bundles.
However, this has the unfortunate side-affect of re-introducing the timing error, that was otherwise fixed in DR24, in the newest target pixel data files that you will per-default download from KASOC. This timing error, resulting in a 66.184 seconds offset between the reported times in the data files and the correct time.
It is important to note that it is only the short cadence target pixel data that are affected, but remember when downloading Kepler data, to please pay attention to the data release number of the data, as the data can be affected by the timing error.
You can read more about the error on the following link:
http://archive.stsci.edu/kepler/timing_error.html

5th Jan 2016: Incorrect DR24 Short Cadence data filter in Data Search

We have added a simple filter to the Data Search page which will allow you to filter out the incorrect Data Release 24 Short Cadence data from your data searches.
The filter, which is enabled by default, can be turned on and off under the "Basic Data" tab of the Data Search query page.
You can read more about the problem here:
http://keplergo.arc.nasa.gov/problem-with-dr24-short-cadence-data.html

13th Nov 2015: Campaign 5 data release note

The campaign 5 data release note (data release 7) is now available:
http://keplerscience.arc.nasa.gov/K2/C5drn.shtml

Kepler & K2 News

4th Feb 2016: Problem with Kepler and K2 short cadence pixel calibration

A K2 Guest Observer notified the Kepler Science Center in November 2015 of a puzzling difference between the short- and long-cadence calibrated pixel data for a specific K2 target.

After investigation, the problem was traced to an accounting error for the short-cadence collateral smear data. Under some conditions, these data are passed incorrectly between the spacecraft and the ground, causing smear values to be assigned to the wrong columns within a target’s aperture.

In these cases, the pipeline’s pixel-level calibration routine applies an erroneous smear correction.

Impact

The issue has been present since launch and affects both the target pixel files and the light curves of approximately half of all short-cadence targets in all releases to date, i.e. Kepler Data Releases 1-24 and K2 Data Releases for Campaigns 0-5. A list of all the affected targets is attached below. The long cadence data for these or other targets is not affected.

Since the smear signal is often small compared to the target signal, the effect is negligible for many targets. However, the smear signal is scene-dependent, so time-varying signals can be introduced into an affected target by the other stars falling on the same CCD column.

To assess the impact on affected targets, users should inspect the calibrated target pixels (see Section 2.3.2 of the Kepler Archive Manual). An improperly corrected smear signal may show up as an anomalously bright, or dark, column in the calibrated target pixel image. Comparison of the short-cadence pixel image with the long-cadence pixel image (which is not affected by this problem) can be used to estimate the magnitude of any contaminating signal.

Solution

The Kepler pipeline has been amended to ensure that the correct smear data is used at all times. All affected data will be corrected as follows:

  • All upcoming K2 data releases will be corrected from the start, beginning with Campaign 6. (The release of C6 short cadence data will be delayed by approximately two weeks as a result.)
  • Reprocessing of K2 Campaigns 0-5 will occur over the coming months. The expected release dates will be listed here when known.
  • Data from the prime Kepler mission will be corrected as part of the scheduled reprocessing with pipeline release 9.3 (DR25). Corrected target pixel files are expected to be available in Summer 2016.
More information

The project has released an erratum document describing the issue and its impact in more detail. The document is accompanied by a list of all the affected targets:

  • KSCI-19080-001.pdf (Erratum document containing a detailed description of the problem.)
  • kepler_bad_short_cadence_target_list.csv
  • k2_bad_short_cadence_target_list.csv

Read more

29th Jan 2016: Minor changes in the fields of Campaigns 11, 12, and 13

K2 users are alerted to a small but necessary adjustment in the position of Campaigns 11, 12, and 13, for which target proposals are currently being solicited as part of the K2 Guest Observer Cycle 4.

The change, explained below, alters ~0.2% of sky area covered and is unlikely to affect the vast majority of proposals. All users are nevertheless encouraged to update the K2fov target selection tool to version 4.0, which was released on 27 Jan 2016 to include the change.

K2fov can be updated from the command line using pip:

pip install K2fov --upgrade

The version number of your K2fov installation may be verified using the following command:

python -c "import pkg_resources; print(pkg_resources.require('K2fov')[0].version)"

This should return "4.0.0" or higher.

Background

Campaigns 11, 12, and 13 are being rotated slightly to accommodate a change in the configuration of the Kepler spacecraft.

During these Campaigns, spacecraft telemetry will be downlinked using a different low-gain antenna than before: LGA2 instead of LGA1. This antenna provides a better orientation to Earth and compensates for the increasing range of the spacecraft to the Earth (now 0.8 AU).

The change of antenna was recently trialled during Campaign 7, where it was found to cause a small increase in the roll drift rate. The reduced pointing performance was understood to be caused by the antenna's radiation pressure, which torques the spacecraft slightly differently when LGA2 is used, increasing the roll rate.

To optimize fuel usage and photometric precision, the K2 team has decided to adjust the roll angle of Campaigns 11, 12, and 13 by a very small amount (0.12--0.16 degrees) to optimally balance the spacecraft against solar pressure and antenna radiation when LGA2 is in use.

As a consequence, there is a minor change in the fields of view covered by K2 during these campaigns. The position of the CCD edges are being shifted by ~0.5 arcsec (~0.1 px) near the center of the focal plane, and by up to 60 arcsec (~15 px) near the corners. The change is illustrated in the figure below, which shows the change in sky coverage for a single CCD channel near the corner of C11, where the shift is the most significant.

Please contact the Guest Observer Office if you have questions.

Figure: Illustration of the effect of the change in sky coverage for one of the CCD detectors near the corner of the focal plane during K2 Campaign 11. The edges of the field are shifted by up to ~60 arcsec.

Read more

28th Jan 2016: Campaign 6 data processing complete

Data processing for K2 Campaign 6 is now complete and the pixel files are in the process of being shipped to the MAST archive. We anticipate that the data will become available to the public by February 11, 2016.

The Campaign 6 target list included 28,289 standard long cadence and 84 short cadence targets. In addition we observed 65 Trojan asteroids in long cadence.

Keep an eye on this website for an announcement of the release and the associated data release notes.

Read more

Recently published scientific publications

  • L. Molnár: An RR Lyrae family portrait: 33 stars observed in Pisces with K2-E2
    Updated: Tue 26th January 2016 11:56.
  • Santiago A. Triana: The internal rotation profile of the B-type star KIC 10526294 from frequency inversion of its dipole gravity modes
    Updated: Mon 25th January 2016 17:54.
  • G. Buldgen: Constraints on the structure of 16 Cyg A and 16 Cyg B using inversion techniques
    Updated: Tue 5th January 2016 14:44.
  • Dennis Stello: Dynamo-generated magnetic fields common in the convective cores of intermediate-mass stars
    Updated: Thu 31st December 2015 00:03.
  • B. Mosser: Period spacings in red giants I. Disentangling rotation and revealing core structure discontinuities
    Updated: Thu 10th December 2015 18:02.
  • M. A. Keen: KIC 10080943: a binary star with two $\gamma$ Doradus/$\delta$ Scuti hybrid pulsators. Analysis of the g modes
    Updated: Thu 10th December 2015 05:02.
  • S. Barceló Forteza: Evidence of amplitude modulation due to Resonant Mode Coupling in the $\delta$ Scuti star KIC 5892969
    Updated: Tue 1st December 2015 21:16.

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