Skip to main content
New! BOOM Notices and Schema v7.0.0. See news and announcements

GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

7293 results found.

  1. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  2. GRB 250328A: Swift-XRT refined Analysis
  3. GRB 250331C: Swift detection of a burst
  4. GRB 250331B: Swift detection of a burst
  5. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  6. GRB 250328A: 1.6m Mephisto optical observations
  7. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  8. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  9. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  10. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  11. GRB 250329A: Swift-XRT afterglow detection
  12. GRB 250328A: SVOM/VT optical observation
  13. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  14. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  15. GRB 250329A: SVOM/VT optical counterpart confirmation
  16. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  17. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  18. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  19. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  20. GRB 250327B: 1.6m Mephisto optical observations
  21. GRB 250327B: SVOM/VT optically bright counterpart
  22. GRB 250327B: SAO RAS optical candidate
  23. GRB 250327A: SVOM/VT optical candidate
  24. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  25. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  26. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  27. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  28. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  29. GRB 250322A: Gemini-North redshift of candidate host galaxy
  30. GRB 250322A: VLT optical observations
  31. GRB 250322A: VLT near-infrared observations
  32. GRB 250322A: NOT optical upper limits
  33. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  34. GRB 250322A: Swift detection of a short burst
  35. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  36. GRB 250321B: Swift ToO observations
  37. GRB 250321B: SVOM detection of a sub-threshold transient event
  38. EP250321a: Kinder optical follow-up observations
  39. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  40. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  41. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  42. GRB 250309B/AT2025dws: further ATCA observations
  43. GRB 250316A: AbAO AS-32 Optical Upper Limit
  44. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  45. GRB 250316A: Swift ToO observations
  46. GRB 250314A: EP-FXT afterglow detection
  47. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  48. EP250315a: optical counterpart candidate detected by Gemini North
  49. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  50. GRB 250314A: SVOM/VT upper limit
  51. GRB 250314A: NOT near-infrared candidate counterpart
  52. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  53. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  54. GRB 250313A: Swift ToO observations
  55. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  56. GRB 250312A: Swift detection of a burst
  57. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  58. GRB 250311A: Tiled Swift observations
  59. GRB 250309B: SVOM/VT optical observation
  60. GRB 250309B / AT2025dws: further SAO RAS optical observations
  61. IceCube-250309A: Upper limits from Fermi-GBM Observations
  62. Konus-Wind detection of GRB 250309B
  63. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  64. GRB 250309B / IceCube-250309A: GECAM-B observations
  65. GRB 250309B / AT2025dws: Swift-UVOT detection
  66. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  67. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  68. IceCube-250309A: No candidates from the Zwicky Transient Facility
  69. GRB 230509B: Tiled Swift observations
  70. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  71. The EP-WXT trigger 01709132387 is likely a flaring star
  72. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  73. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  74. LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
  75. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  76. EP250225a: the candidate optical counterpart is an AGN
  77. EP250302a: Kinder optical follow-up observations
  78. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  79. EP250302a: Montarrenti Observatory optical detection
  80. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  81. GRB 250225B: VLT near-infrared afterglow confirmation
  82. EP250228a: Optical observations with Kinder and Swift/UVOT
  83. GRB 250225B: VLT/HAWKI near-infrared observations
  84. EP250227a: Optical upper limits with Kinder observations
  85. EP250225a: EP-FXT follow-up observation
  86. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  87. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  88. GRB 250225B: VLT/Xshooter imaging
  89. EP250225a: NOT optical candidate counterpart
  90. EP250226a/GRB 250226A: 1.6m Mephisto observations
  91. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  92. EP250226a/GRB 250226A: Kinder optical follow-up observations
  93. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  94. LIGO/Virgo/KAGRA S250227y: Retraction of GW compact binary merger candidate
  95. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  96. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  97. GRB 250225B: REM NIR upper limits
  98. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  99. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  100. GRB 250225B: VLT optical and near-infrared candidate counterpart

Advanced

Download all Circulars as a .tar.gz archive:
Questions or comments?
Contact GCN directly.
Have you found a bug in GCN?
Open an issue.
Want to contribute code to GCN?
Get involved on GitHub.

gcn.nasa.gov

A service of the Astrophysics Science Division at NASA Goddard Space Flight Center

Looking for U.S. government information and services? Visit USA.gov