Skip to main content
Updates to LVK & CHIME Notices, Schema v7.2.3! 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"

23407 results found.

  1. EP250911a: Swift-XRT observations
  2. EP250911a: Optical detection with Kinder observations
  3. GRB 250911A: Swift/UVOT Detection
  4. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  5. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  6. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  7. EP250911a: COLIBRÍ optical observations
  8. EP250911a: Einstein Probe detection of an X-ray transient
  9. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  10. GRB 250903A: SVOM/ECLAIRs refined analysis
  11. GRB 250911A: Enhanced Swift-XRT position
  12. GRB 250911A: Swift-XRT observations
  13. GRB 250911A: COLIBRÍ optical counterpart candidate
  14. GRB 250911A: Swift detection of a burst
  15. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  16. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  17. GRB 250910A: SVOM/VT optical upper limit
  18. GRB 250910A: LCO optical upper limit
  19. EP250908b/EP#01709240653: Swift/UVOT Detection
  20. EP#01709240653: Swift-XRT observations
  21. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  22. EP250908c: SVOM/VT optical observation
  23. EP250908c: VLT/FORS2 optical counterpart identification
  24. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  25. EP250908b: SVOM/VT optical candidate
  26. EP250908c: Einstein Probe detection of an X-ray transient
  27. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  28. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  29. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  30. GRB 250903A: Swift-XRT afterglow detection
  31. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  32. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  33. EP250905a: Liverpool Telescope i-band upper limits
  34. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  35. EP250905a: Liverpool Telescope observations
  36. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  37. EP250905b: EP-WXT detection of a fast X-ray transient
  38. EP250905a: JinShan likely optical counterpart detection
  39. GRB 250905A: Swift/UVOT Upper Limits
  40. GRB 250901A - SVOM/ECLAIRs refined analysis
  41. EP250905a: Einstein Probe detection of an X-ray transient
  42. GRB250904A: Liverpool Telescope upper limits
  43. GRB 250905A: Enhanced Swift-XRT position
  44. GRB 250904A: Swift/UVOT Detection
  45. GRB 250903A: Swift/UVOT detection
  46. GRB 250904A: Swift-XRT refined Analysis
  47. EP detected a brightening of LMXB 1ES 1735-26.9
  48. GRB 250905A: KAIT optical upper limit
  49. GRB 250905A: Swift detection of a burst
  50. GRB 250904A: Enhanced Swift-XRT position
  51. GRB 250904A: TRT optical counterpart detection
  52. GRB 250904A: Swift detection of a burst
  53. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  54. GRB 250903A: Swift-XRT observations
  55. EP250903a: Swift-XRT observations
  56. EP#01709201209: Swift-XRT observations
  57. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  58. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  59. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  60. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  61. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  62. GRB 250903A: LCO optical observation
  63. GRB 250903A: LCO optical afterglow detection
  64. GRB 250903A: SVOM/VT optical confirmation with VHF data
  65. EP250901a: Mondy, Assy and SAO RAS optical limits
  66. Subject GRB 250903A: SVOM/MXT afterglow detection
  67. EP250903a: LCO candidate counterpart discovery
  68. GRB 250903A: TRT optical counterpart detection
  69. EP250903a: TRT optical observations
  70. EP250903a: Einstein Probe detection of an X-ray transient
  71. EP 250827B: Detection of supernova counterpart by LCO.
  72. EP/WXT01709201159: GOTO optical follow-up
  73. GRB 250902B: SVOM/GRM observation
  74. EP250827b: SVOM/VT observation of AT 2025wkm
  75. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  76. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  77. GRB 250901A: Swift/UVOT Upper Limit
  78. GRB 250830B: Swift-XRT afterglow detection
  79. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  80. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  81. GRB 250902A: SVOM/GRM observation
  82. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  83. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  84. GRB 250901A: SVOM/VT optical afterglow with VHF data
  85. GRB 250901A: Swift-XRT afterglow detection
  86. EP250901a: Swift-XRT observations
  87. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  88. GRB 250901A: LCO optical upper limit
  89. EP250827b: Swift observations of AT 2025wkm
  90. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  91. EP250831a: NOT optical observations and tentative afterglow candidate
  92. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  93. GRB 250901A: SVOM detection of a burst
  94. EP250901a: Mephisto optical upper limits
  95. EP250901a: Einstein Probe detection of an X-ray transient
  96. EP250831a: Swift-XRT observations
  97. EP250831a: EP-WXT detection of a fast X-ray transient
  98. GRB 250831A: Swift-XRT counterpart detection
  99. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  100. GRB 250831A: SVOM/VT upper limit with VHF data

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
Looking for U.S. government information and services? Visit USA.gov