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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"

32536 results found.

  1. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  2. Corrected Swift-XRT Refined Analysis of GRB 250809A
  3. GRB 250807B: SVOM/VT optical observation
  4. EP250807a: EP-FXT follow-up observation upper limit
  5. GRB 250809A: LCOGT Optical Upper Limits
  6. GRB 250702B: Chandra X-ray Detection
  7. EP250807a: Global MASTER-Net observations report
  8. Fermi GRB 250808A: Global MASTER-Net observations report
  9. GRB 250808A: VLT X-shooter candidate counterpart
  10. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  11. GRB 250808A: Fermi GBM Observation
  12. GRB 250807A: SVOM/VT optical continued observation
  13. EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
  14. GRB 250808A: SVOM detection of a long burst
  15. Konus-Wind detection of GRB 250807A
  16. GRB 250807B: Swift/UVOT Detection
  17. GRB 250807B: Kilonova-Catcher optical afterglow detection
  18. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  19. GRB 250807A: Swift/UVOT Detection
  20. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  21. GRB 250806A: SVOM/MXT refined analysis
  22. GRB 250806A: SVOM/ECLAIRs refined analysis
  23. EP250807a: NTT z-band optical upper limit
  24. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  25. GRB 250804B: Insight-HXMT detection
  26. GRB 250807A: SVOM/GRM observation
  27. GRB 250807A: AstroSat CZTI detection of bright long burst
  28. GRB 250806A: NOT z-band upper limit and host galaxy candidate
  29. GRB 250807B: NTT optical observations
  30. EP250807a: EP-WXT detection of a fast X-ray transient
  31. GRB 250807A: SVOM/VT optical observation
  32. EP250806a: Upper limit from Fermi-GBM Observations
  33. GRB 250805A: Kilonova-Catcher optical upper limits
  34. EP250806a:SVOM/VT refined analysis
  35. GRB 250805A: Swift/UVOT Upper Limits
  36. GRB 250806A: Swift/UVOT U-band detection
  37. EP250806a: Liverpool telescope optical upper limit
  38. GRB 250806A: EP-FXT observation
  39. EP#01709198415/EP250806a: Swift-XRT observations
  40. EP250806a: Global MASTER-Net observations report
  41. EP250802a: EP-FXT follow-up observation
  42. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  43. EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
  44. EP250806a: SVOM /VT optical candidate
  45. GRB 250806A: J-band upper limit from WINTER
  46. GRB 250805A: Swift-BAT refined analysis
  47. GRB 250806A: KAIT optical upper limit
  48. GRB 250806A: SVOM/VT refined analysis
  49. EP250806a: COLIBRÍ optical upper limit
  50. GRB 250806A: Kilonova-Catcher optical upper limits
  51. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  52. GRB 250806A: SVOM/VT optical upper limit
  53. GRB 250805A: SVOM/VT optical counterpart
  54. GRB 250805A: ESO/VLT observations
  55. GRB 250805A: TRT optical upper limits
  56. GRB 250804B: Tiled Swift observations
  57. EP250802a: additional Liverpool Telescope upper limits
  58. EP250730a: SVOM/VT optical upper limit
  59. EP250802a: Liverpool Telescope optical upper limits
  60. EP250802a: Global MASTER-Net observations report
  61. EP250802a: GROWTH-India Telescope optical upper limit
  62. LIGO/Virgo/KAGRA S250802dn: Updated Sky localization
  63. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  64. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  65. GRB 250702B: SMA observations
  66. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  67. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  68. EP250711a: CrAO and Assy optical observations
  69. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  70. EP250730a: Global MASTER-Net observations report
  71. EP250730a: COLIBRÍ optical upper limit
  72. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  73. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  74. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  75. GRB 250725A: AstroSat CZTI detection
  76. GRB 250727A: EP-FXT follow-up observation
  77. GRB 250725A: PRIME near-infrared observations
  78. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  79. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  80. GRB: Clarification on Gamma-Ray Burst Naming Convention
  81. GRB 250727A: SVOM/ECLAIRs refined analysis
  82. EP-WXT trigger 01709195487: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  83. GRB 250728A: COLIBRÍ optical upper limit
  84. GRB 250728A: Fermi GBM Observation
  85. LIGO/Virgo/KAGRA S250727dc: Updated Sky localization
  86. GRB 250728A: Swift ToO observations
  87. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  88. GRB 250727A: AST3-2 Upper limit
  89. LIGO/Virgo/KAGRA S250727cl: Updated Sky localization
  90. GRB 250727A: EP-FXT counterpart detection
  91. GRB250727A: SVOM/VT optical upper limit
  92. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  93. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  94. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  95. LIGO/Virgo/KAGRA S250725l: Updated Sky localization
  96. LIGO/Virgo/KAGRA S250726ak: Updated Sky localization
  97. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  98. GRB 250725A: Fermi GBM Observation
  99. LIGO/Virgo/KAGRA S250725j: Updated Sky localization
  100. GRB 250725A: Swift-BAT refined analysis

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