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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"

4994 results found.

  1. SVOM/sb25081602: detection of a likely X-ray transient
  2. GRB 250814A: Possible afterglow candidate from P200/WIRC
  3. Fermi trigger No 776818276: Global MASTER-Net observations report
  4. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  5. GRB 250814A: DDOTI Optical Upper Limit
  6. GRB 250814A: Fermi GBM Final Real-time Localization
  7. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  8. GRB 250812A: Swift/UVOT Detection
  9. EP250812a: SVOM/VT optical counterpart
  10. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  11. IceCube Alert 250813.14: Global MASTER-Net observations report
  12. EP250812a: Einstein Probe detection of an X-ray transient
  13. GRB 250812A: Swift-XRT afterglow detection
  14. GRB 250812A: TRT likely optical counterpart detection
  15. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  16. GRB 250702B: Chandra X-ray Detection
  17. Fermi GRB 250808A: Global MASTER-Net observations report
  18. Fermi Gamma-ray Burst Monitor trigger 776449964/250809689 is not a GRB
  19. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  20. Swift GRB250807.45: Global MASTER-Net observations report
  21. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  22. EP250806a: SVOM /VT optical candidate
  23. GRB 250805A: ESO/VLT observations
  24. GRB 250805A: Swift detection of a burst
  25. Swift GRB250805.26: Global MASTER-Net observations report
  26. EP250730a: SVOM/VT optical upper limit
  27. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  28. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  29. EP250730a: Global MASTER-Net observations report
  30. EP250730a: Einstein Probe detection of an X-ray transient
  31. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  32. GRB 250728A: Fermi GBM Observation
  33. GRB 250727A: AST3-2 Upper limit
  34. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  35. GRB 250721A: Fermi GBM Observation
  36. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  37. GRB 250722A: Fermi GBM Final Real-time Localization
  38. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  39. GRB 250721A: MAXI/GSC detection
  40. GRB 250721A: Fermi GBM Final Localization
  41. Fermi trigger No 774730635: Global MASTER-Net observations report
  42. GRB 250717B: COLIBRÍ optical upper limit
  43. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  44. GRB 250713A: SVOM/VT optical upper limit
  45. GRB 250713A: SVOM/C-GFT upper limit
  46. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  47. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  48. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  49. GRB 250702B,D,E / EP250702a: ALMA detection
  50. IceCube-250708A: No Candidates from WINTER
  51. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  52. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  53. GRB 250709A: Fermi GBM Final Localization
  54. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  55. GRB 250704B / EP250704a: VLA radio detection
  56. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  57. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  58. GRB 250703A: EIRSAT-1 GMOD Detection
  59. Konus-Wind detection of GRB 250703A
  60. IPN triangulation of GRB 250703A
  61. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  62. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  63. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  64. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  65. Fermi GRB 250703A: Global MASTER-Net observations report
  66. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  67. GRB 250703A: DDOTI Optical Upper Limit
  68. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  69. GRB 250703A: Fermi GBM Final Real-time Localization
  70. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  71. Fermi GRB 250702F: Global MASTER-Net observations report
  72. GRB 250702F: Swift detection of a burst with an optical counterpart
  73. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  74. GRB 250702A: Fermi GBM Detection
  75. GRB 250702D: Fermi GBM Final Localization Correction
  76. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  77. GRB 250702A: Fermi GBM Final Real-time Localization
  78. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  79. Fermi GRB 250626A: Global MASTER-Net observations report
  80. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  81. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  82. GRB 250625A: ABObservatory afterglow detection
  83. GRB 250521A: VZLUSAT-2 detection
  84. Fermi trigger No 772190032: Global MASTER-Net observations report
  85. GRB 250620C: Fermi GBM Final Real-time Localization
  86. Fermi trigger No 772128434: Global MASTER-Net observations report
  87. GRB 250617B: Nickel telescope optical observations
  88. GRB 250617B: COLIBRÍ optical observations
  89. GRB 250617B: NUTTelA-TAO early time optical observations
  90. GRB 250617A: Fermi GBM Final Real-time Localization
  91. EP#01709178975: Swift-XRT counterpart detection
  92. GRB 250615A: DDOTI Optical Upper Limit
  93. Fermi trigger No 771752663: Global MASTER-Net observations report
  94. IceCube alert 141029_8144692 retraction
  95. EP250610a: Global MASTER-Net observations report
  96. EP250610a: REM optical/NIR observations
  97. GRB 250609A: Fermi GBM Observation
  98. Fermi trigger No 771072240: Global MASTER-Net observations report
  99. The EP-WXT trigger 01709178283 is likely a flaring star
  100. Fermi trigger No 770867684: Global MASTER-Net observations report

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