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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"

19565 results found.

  1. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  2. EP250911a: COLIBRÍ optical observations
  3. EP250911a: Einstein Probe detection of an X-ray transient
  4. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  5. GRB 250911A: Enhanced Swift-XRT position
  6. GRB 250911A: Swift-XRT observations
  7. GRB 250911A: COLIBRÍ optical counterpart candidate
  8. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  9. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  10. GRB 250909B: AstroSat CZTI detection of a long burst
  11. GRB 250910A: SVOM/VT optical upper limit
  12. GRB 250910A: LCO optical upper limit
  13. GRB 250910A: SVOM detection of a faint burst
  14. EP250908b/EP#01709240653: Swift/UVOT Detection
  15. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  16. EP250908c: SVOM/VT optical observation
  17. EP250908c: VLT/FORS2 optical counterpart identification
  18. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  19. EP250908b: SVOM/VT optical candidate
  20. EP250908c: Einstein Probe detection of an X-ray transient
  21. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  22. GRB 250903A: Swift-XRT afterglow detection
  23. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  24. EP250905a: Liverpool Telescope i-band upper limits
  25. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  26. EP250905a: Liverpool Telescope observations
  27. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  28. EP250905b: EP-WXT detection of a fast X-ray transient
  29. EP250905a: JinShan likely optical counterpart detection
  30. GRB 250905A: Swift/UVOT Upper Limits
  31. GRB 250901A - SVOM/ECLAIRs refined analysis
  32. EP250905a: Einstein Probe detection of an X-ray transient
  33. GRB250904A: Liverpool Telescope upper limits
  34. GRB 250905A: Enhanced Swift-XRT position
  35. GRB 250904A: Swift/UVOT Detection
  36. GRB 250903A: Swift/UVOT detection
  37. EP detected a brightening of LMXB 1ES 1735-26.9
  38. GRB 250905A: KAIT optical upper limit
  39. GRB 250905A: Swift detection of a burst
  40. GRB 250904A: Enhanced Swift-XRT position
  41. GRB 250904A: TRT optical counterpart detection
  42. GRB 250904A: Swift detection of a burst
  43. GRB 250902A: VZLUSAT-2 detection
  44. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  45. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  46. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  47. GRB 250830C: VZLUSAT-2 detection
  48. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  49. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  50. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  51. GRB 250903A: LCO optical observation
  52. GRB 250903A: LCO optical afterglow detection
  53. GRB 250903A: SVOM/VT optical confirmation with VHF data
  54. EP250901a: Mondy, Assy and SAO RAS optical limits
  55. GRB 250903A: TRT optical counterpart detection
  56. EP250903a: TRT optical observations
  57. EP250903a: Einstein Probe detection of an X-ray transient
  58. EP 250827B: Detection of supernova counterpart by LCO.
  59. GRB 250902B: SVOM/GRM observation
  60. EP250827b: SVOM/VT observation of AT 2025wkm
  61. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  62. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  63. GRB 250901A: Swift/UVOT Upper Limit
  64. GRB 250830B: Swift-XRT afterglow detection
  65. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  66. GRB 250902A: SVOM/GRM observation
  67. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  68. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  69. GRB 250901A: SVOM/VT optical afterglow with VHF data
  70. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  71. GRB 250901A: LCO optical upper limit
  72. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  73. EP250831a: NOT optical observations and tentative afterglow candidate
  74. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  75. GRB 250901A: SVOM detection of a burst
  76. EP250901a: Mephisto optical upper limits
  77. EP250901a: Einstein Probe detection of an X-ray transient
  78. EP250831a: EP-WXT detection of a fast X-ray transient
  79. GRB 250831A: Swift-XRT counterpart detection
  80. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  81. GRB 250831A: SVOM/VT upper limit with VHF data
  82. GRB 250831A: SVOM detection of a soft burst
  83. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  84. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  85. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  86. GRB 250830B: Swift ToO observations
  87. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  88. EP250821a: SOAR observations
  89. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  90. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  91. GRB 250808B: SVOM detection of a burst through offline search
  92. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  93. EP250828a: Optical counterpart detection with Kinder observations
  94. EP250828a: Liverpool Telescope upper limits
  95. EP-WXT trigger 01709200800 : KAIT optical observations
  96. EP250828a: KAIT optical upper limit
  97. EP250827a: Swift/UVOT Detection
  98. EP250828a: NOT optical counterpart confirmation
  99. EP250828a: SVOM/VT optical candidate
  100. EP250828a: Seimei/TriCCS optical counterpart detection

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