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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"

32531 results found.

  1. GRB 250916A: AstroSat CZTI detection of a bright long burst
  2. GRB 250910A: SVOM/ECLAIRs refined analysis
  3. Fermi GRB 250916A: Global MASTER-Net observations report
  4. EP250827b: VLA Observations
  5. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  6. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  7. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  8. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  9. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  10. GRB 250912A: Swift-XRT observations
  11. GRB250912A: VLT/HAWK-I follow-up observations
  12. GRB 250912A: VLT observations
  13. GRB 250912A: Fermi GBM Observation
  14. GRB 250911A: Insight-HXMT detection
  15. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  16. GRB 250912A:SVOM/VT optical upper limit
  17. GRB 250912A: LCO optical upper limit
  18. Fermi GRB 250912A: Global MASTER-Net observations report
  19. EP250911a: Global MASTER-Net observations report
  20. GRB 250912A: SVOM detection of a burst
  21. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  22. EP250911a: Upper limit from Fermi-GBM Observations
  23. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  24. GRB 250911A: GECAM-B detection
  25. GRB 250911A: Swift-BAT refined analysis
  26. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  27. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  28. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  29. GRB 250910B: SVOM/GRM observation
  30. EP250911a: SVOM/VT optical observation
  31. GRB 250911A: MASTER optical counterpart observations
  32. EP250911a: SAO RAS optical observations
  33. EP250911a: Swift-XRT observations
  34. EP250911a: Optical detection with Kinder observations
  35. GRB 250911A: Swift/UVOT Detection
  36. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  37. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  38. GRB 250909B: Insight-HXMT detection
  39. GRB 250909B: SVOM/GRM observation
  40. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  41. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  42. EP250911a: COLIBRÍ optical observations
  43. LIGO/Virgo/KAGRA S250908y: Updated Sky localization
  44. Fermi GRB 250910B: Global MASTER-Net observations report
  45. EP250911a: LCO optical counterpart discovery
  46. EP250910a: Global MASTER-Net observations report
  47. GRB 250404A / EP250404a: spectroscopic redshift at z = 1.88 (correction to GCN 40084)
  48. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  49. GRB 250903A: SVOM/ECLAIRs refined analysis
  50. GRB 250911A: COLIBRÍ optical counterpart candidate
  51. LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
  52. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  53. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  54. GRB 250910A: SVOM/VT optical upper limit
  55. EP250908C: GROND observation of the fading optical counterpart
  56. GRB 250910A: LCO optical upper limit
  57. GRB 250909A: AstroSat CZTI detection
  58. GRB 250910A: SVOM/MXT possible afterglow detection
  59. GRB 250702B: Late time Chandra observations
  60. EP250908b/EP#01709240653: Swift/UVOT Detection
  61. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  62. GRB 250907A: CALET Gamma-Ray Burst Monitor detection
  63. EP250908c: SVOM/VT optical observation
  64. EP250908c: VLT/FORS2 optical counterpart identification
  65. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  66. EP250908b: SVOM/VT optical candidate
  67. EP250908c: Global MASTER-Net observations report
  68. Fermi GRB 250909A: Global MASTER-Net observations report
  69. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  70. GRB 250905A: Swift-BAT refined analysis
  71. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  72. GRB 250903A: Swift-XRT afterglow detection
  73. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  74. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  75. EP250905a: Liverpool Telescope i-band upper limits
  76. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  77. EP250905b: EP-FXT follow-up observation
  78. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  79. EP250905a: Liverpool Telescope observations
  80. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  81. EP250905b: Global MASTER-Net observations report
  82. EP250905a: FTW one optical and multiple NIR counterpart candidates
  83. EP250905a: JinShan likely optical counterpart detection
  84. GRB 250904A: Swift-BAT refined analysis
  85. GRB 250905A: Swift/UVOT Upper Limits
  86. EP250905a: Global MASTER-Net observations report
  87. GRB 250901A - SVOM/ECLAIRs refined analysis
  88. GRB250904A: Liverpool Telescope upper limits
  89. GRB 250904A: Swift/UVOT Detection
  90. GRB 250903A: Swift/UVOT detection
  91. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  92. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  93. GRB 250905A: KAIT optical upper limit
  94. Swift GRB 250904A: Global MASTER-Net observations report
  95. GRB 250904A: TRT optical counterpart detection
  96. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  97. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  98. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  99. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  100. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization

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