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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

32756 results found.

  1. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  2. EP250905b: EP-FXT follow-up observation
  3. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  4. EP250905a: Liverpool Telescope observations
  5. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  6. EP250905b: Global MASTER-Net observations report
  7. EP250905a: FTW one optical and multiple NIR counterpart candidates
  8. EP250905a: JinShan likely optical counterpart detection
  9. GRB 250904A: Swift-BAT refined analysis
  10. GRB 250905A: Swift/UVOT Upper Limits
  11. EP250905a: Global MASTER-Net observations report
  12. GRB 250901A - SVOM/ECLAIRs refined analysis
  13. GRB250904A: Liverpool Telescope upper limits
  14. GRB 250904A: Swift/UVOT Detection
  15. GRB 250903A: Swift/UVOT detection
  16. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  17. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  18. GRB 250905A: KAIT optical upper limit
  19. Swift GRB 250904A: Global MASTER-Net observations report
  20. GRB 250904A: TRT optical counterpart detection
  21. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  22. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  23. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  24. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  25. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  26. GRB 250902A: VZLUSAT-2 detection
  27. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  28. GRB 250903A: Swift-XRT observations
  29. EP250903a: Swift-XRT observations
  30. EP#01709201209: Swift-XRT observations
  31. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  32. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  33. GRB 250830C: VZLUSAT-2 detection
  34. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  35. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  36. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  37. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  38. GRB 250903A: EP-FXT counterpart detection
  39. GRB 250902A: GECAM-B detection
  40. GRB 250903A: LCO optical observation
  41. GRB 250903A: LCO optical afterglow detection
  42. GRB 250903A: SVOM/VT optical confirmation with VHF data
  43. EP250903a: SVOM/VT optical confirmation
  44. EP250901a: Mondy, Assy and SAO RAS optical limits
  45. Subject GRB 250903A: SVOM/MXT afterglow detection
  46. EP250903a: LCO candidate counterpart discovery
  47. GRB 250903A: TRT optical counterpart detection
  48. GRB 250902B: AstroSat CZTI detection
  49. EP250903a: Global MASTER-Net observations report
  50. EP250903a: TRT optical observations
  51. EP250903a: Einstein Probe detection of an X-ray transient
  52. EP 250827B: Detection of supernova counterpart by LCO.
  53. EP250827b / AT 2025wkm: TRT optical observations
  54. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  55. EP250827b: continued Liverpool Telescope observations
  56. GRB 250902B: SVOM/GRM observation
  57. EP250827b: SVOM/VT observation of AT 2025wkm
  58. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  59. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  60. Fermi GRB 250902B: Global MASTER-Net observations report
  61. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  62. GRB 250902A: Fermi GBM Detection
  63. GRB 250901A: Swift/UVOT Upper Limit
  64. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  65. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  66. EP250827b: Liverpool Telescope observations
  67. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  68. GRB 250902A: SVOM/GRM observation
  69. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  70. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  71. GRB 250901A: EP-FXT follow-up observation
  72. GRB 250901A: NOT optical observations
  73. GRB 250901A: SVOM/VT optical afterglow with VHF data
  74. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  75. GRB 250901A: LCO optical upper limit
  76. EP250827b: Swift observations of AT 2025wkm
  77. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  78. EP250827b: Gemini Spectroscopy of AT 2025wkm
  79. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  80. EP250831a: NOT optical observations and tentative afterglow candidate
  81. EP250827b: FTW Observations of AT 2025wkm
  82. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  83. GRB 250830C: Insight-HXMT detection
  84. EP250901a: Mephisto optical upper limits
  85. EP250901a: Global MASTER-Net observations report
  86. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  87. EP250831a: EP-FXT follow-up observation
  88. EP250831a: Swift-XRT observations
  89. EP250831a: Global MASTER-Net observations report
  90. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  91. GRB 250831A: Swift-XRT counterpart detection
  92. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  93. GRB 250831A: SVOM/VT upper limit with VHF data
  94. EP250830a: Global MASTER-Net observations report
  95. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  96. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  97. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  98. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  99. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  100. EP-WXT trigger 01709200994: Liverpool Telescope upper limits

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