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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"

21679 results found.

  1. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  2. GRB 250903A: Swift-XRT afterglow detection
  3. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  4. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  5. EP250905a: Liverpool Telescope i-band upper limits
  6. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  7. EP250905a: Liverpool Telescope observations
  8. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  9. EP250905b: EP-WXT detection of a fast X-ray transient
  10. EP250905a: JinShan likely optical counterpart detection
  11. GRB 250905A: Swift/UVOT Upper Limits
  12. GRB 250901A - SVOM/ECLAIRs refined analysis
  13. EP250905a: Einstein Probe detection of an X-ray transient
  14. GRB250904A: Liverpool Telescope upper limits
  15. GRB 250905A: Enhanced Swift-XRT position
  16. GRB 250904A: Swift/UVOT Detection
  17. GRB 250903A: Swift/UVOT detection
  18. GRB 250904A: Swift-XRT refined Analysis
  19. EP detected a brightening of LMXB 1ES 1735-26.9
  20. GRB 250905A: KAIT optical upper limit
  21. GRB 250905A: Swift detection of a burst
  22. GRB 250904A: Enhanced Swift-XRT position
  23. GRB 250904A: TRT optical counterpart detection
  24. GRB 250904A: Swift detection of a burst
  25. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  26. GRB 250903A: Swift-XRT observations
  27. EP250903a: Swift-XRT observations
  28. EP#01709201209: Swift-XRT observations
  29. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  30. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  31. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  32. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  33. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  34. GRB 250903A: LCO optical observation
  35. GRB 250903A: LCO optical afterglow detection
  36. GRB 250903A: SVOM/VT optical confirmation with VHF data
  37. EP250901a: Mondy, Assy and SAO RAS optical limits
  38. Subject GRB 250903A: SVOM/MXT afterglow detection
  39. EP250903a: LCO candidate counterpart discovery
  40. GRB 250903A: TRT optical counterpart detection
  41. EP250903a: TRT optical observations
  42. EP250903a: Einstein Probe detection of an X-ray transient
  43. EP 250827B: Detection of supernova counterpart by LCO.
  44. EP/WXT01709201159: GOTO optical follow-up
  45. GRB 250902B: SVOM/GRM observation
  46. EP250827b: SVOM/VT observation of AT 2025wkm
  47. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  48. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  49. GRB 250901A: Swift/UVOT Upper Limit
  50. GRB 250830B: Swift-XRT afterglow detection
  51. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  52. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  53. GRB 250902A: SVOM/GRM observation
  54. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  55. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  56. GRB 250901A: SVOM/VT optical afterglow with VHF data
  57. GRB 250901A: Swift-XRT afterglow detection
  58. EP250901a: Swift-XRT observations
  59. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  60. GRB 250901A: LCO optical upper limit
  61. EP250827b: Swift observations of AT 2025wkm
  62. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  63. EP250831a: NOT optical observations and tentative afterglow candidate
  64. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  65. GRB 250901A: SVOM detection of a burst
  66. EP250901a: Mephisto optical upper limits
  67. EP250901a: Einstein Probe detection of an X-ray transient
  68. EP250831a: Swift-XRT observations
  69. EP250831a: EP-WXT detection of a fast X-ray transient
  70. GRB 250831A: Swift-XRT counterpart detection
  71. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  72. GRB 250831A: SVOM/VT upper limit with VHF data
  73. GRB 250831A: SVOM detection of a soft burst
  74. GRB 250830B: Swift-XRT observations
  75. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  76. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  77. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  78. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  79. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  80. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  81. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  82. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  83. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  84. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  85. EP250828a: Optical counterpart detection with Kinder observations
  86. EP250828a: Liverpool Telescope upper limits
  87. EP-WXT trigger 01709200800 : KAIT optical observations
  88. EP250828a: KAIT optical upper limit
  89. EP250827a: Swift/UVOT Detection
  90. EP250828a: NOT optical counterpart confirmation
  91. EP250828a: SVOM/VT optical candidate
  92. EP250828a: Seimei/TriCCS optical counterpart detection
  93. GRB 250828B: Swift detection of a burst
  94. EP250828a: Optical upper limit with Kinder observations
  95. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  96. EP250828a: Einstein Probe detection of an X-ray transient
  97. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  98. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  99. EP250827a: confirmation of optical rebrightening with LCO
  100. GRB 250826A: SVOM/GRM observation

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