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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"
  1. GRB 230709C: Fermi GBM Final Localization
  2. GRB 230707B: Fermi GBM Observation
  3. GRB 230710A: Fermi GBM Final Real-time Localization
  4. LIGO/Virgo/KAGRA S230708z: Identification of a GW compact binary merger candidate
  5. LIGO/Virgo/KAGRA S230708t: Identification of a GW compact binary merger candidate
  6. IceCube-230707A: No candidates detected by Swift-XRT
  7. Swift Trigger 1178410 is not an astrophysical event
  8. GRB 230709C: AstroSat CZTI detection
  9. LIGO/Virgo/KAGRA S230708cf: Updated Sky localization
  10. GRB 230707B: CALET Gamma-Ray Burst Monitor detection
  11. GRB 230703A detected with multiple GRID detectors
  12. GRB 230709C: BALROG localization (Fermi Trigger 710617111 / GRB 230709735)
  13. LIGO/Virgo/KAGRA S230707ai: Updated Sky localization
  14. IceCube-230707A: No candidates from the Zwicky Transient Facility
  15. Fermi-LAT gamma-ray observations of IceCube-230708A
  16. Fermi-LAT gamma-ray observations of IceCube-230707B
  17. Fermi-LAT gamma-ray observations of IceCube-230707A
  18. LIGO/Virgo/KAGRA S230630am: Updated Sky localization
  19. LIGO/Virgo/KAGRA S230630am: Updated Sky localization
  20. GRB 230709B: BALROG localization (Fermi Trigger 710614579 / GRB 230709706)
  21. IceCube-230708A: Upper limits from a search for additional neutrino events in IceCube
  22. IceCube-230707B: Upper limits from a search for additional neutrino events in IceCube
  23. IceCube-230707A: Upper limits from a search for additional neutrino events in IceCube
  24. LIGO/Virgo/KAGRA S230709bi: Identification of a GW compact binary merger candidate
  25. Swift Trigger 1178410: possible GRB 230709A
  26. LIGO/Virgo/KAGRA S230708cf: Identification of a GW compact binary merger candidate
  27. LIGO/Virgo/KAGRA S230708bi: Retraction of GW compact binary merger candidate
  28. GRB 230628C: GRID Detection
  29. IceCube-230708A - IceCube observation of a high-energy neutrino candidate track-like event
  30. GRB 230707B: Swift/BAT-GUANO detection of a burst outside the coded FOV
  31. GRB 230707A: Swift-XRT observations
  32. IceCube Alert 230708.35: Global MASTER-Net observations report
  33. IceCube-230707B - IceCube observation of a high-energy neutrino candidate track-like event
  34. GRB 230707B: Fermi GBM Final Real-time Localization
  35. IceCube Alert 230707.71: Global MASTER-Net observations report
  36. IceCube-230707A - IceCube observation of a high-energy neutrino candidate track-like event
  37. GRB 230707A: Fermi GBM Detection
  38. LIGO/Virgo/KAGRA S230707ai: Identification of a GW compact binary merger candidate
  39. GRB 230707A: Swift ToO observations
  40. GRB 230707A: Swift/BAT-GUANO arcminute localization of a burst
  41. ZTF23aaoohpy/AT2023lcr : HCT follow-up observations
  42. Fermi GRB 230707A: Global MASTER-Net observations report
  43. GRB 230707A: Fermi GBM Final Real-time Localization
  44. LIGO/Virgo/KAGRA S230706ah: Updated Sky localization
  45. Integral GRB230706.70: Global MASTER-Net observations report
  46. LIGO/Virgo/KAGRA S230704f: Updated Sky localization
  47. LIGO/Virgo/KAGRA S230630bq: Updated Sky localization
  48. IBAS trigger number 10311: not a real GRB
  49. LIGO/Virgo/KAGRA S230702an: Updated Sky localization
  50. GRB 230625A: Detection by GRID
  51. LIGO/Virgo/KAGRA S230529ay: Updated Sky localization and EM Bright Classification
  52. LIGO/Virgo/KAGRA S230706ah: Identification of a GW compact binary merger candidate
  53. LIGO/Virgo/KAGRA S230627c: GECKO optical follow-up observations of host galaxy candidates and ZTF23aaptsuy/AT2023lxu
  54. ZTF23aaoohpy/AT2023lcr: AMI-LA radio detection
  55. Fermi trigger No 710117592: Global MASTER-Net observations report
  56. GRB 230626A: VZLUSAT-2 detection
  57. LVK S230619bd/GBM-230619: Upper limits from a two-week IceCube neutrino search
  58. GRB 230328B: LBT detection of the likely host galaxy
  59. LIGO/Virgo/KAGRA S230704f: Identification of a GW compact binary merger candidate
  60. Konus-Wind detection of GRB 220623A
  61. GRB 230701B: AstroSat CZTI detection
  62. LIGO/Virgo/KAGRA S230627c: observations of ZTF23aaptsuy/AT2023lx in AbAO observatory
  63. LIGO/Virgo/KAGRA S230702an: Identification of a GW compact binary merger candidate
  64. GRB 230628E: Swift/UVOT Detection
  65. GRB 230628E: Swift-BAT refined analysis
  66. GRB 230702A: Fermi GBM Final Real-time Localization
  67. GRB 230628E: ATCA rapid radio follow-up
  68. GRB 230701A: Fermi GBM Final Real-time Localization
  69. LIGO/Virgo/KAGRA S230627c: GRANDMA observations of galaxies and ZTF counterpart candidates
  70. LIGO/Virgo/KAGRA low-significance gravitational wave candidate S230701z: one counterpart neutrino candidate from IceCube neutrino searches
  71. LIGO/Virgo/KAGRA S230627c: Upper limits from Swift/BAT-GUANO
  72. LIGO/Virgo/KAGRA S230630bq: Identification of a GW compact binary merger candidate
  73. IPN triangulation of GRB 230625B (ultra-long)
  74. AT2023lcr (ATLAS23msn/ZTF23aaoohpy): ALMA 100 GHz Detection
  75. LIGO/Virgo/KAGRA S230630am: Identification of a GW compact binary merger candidate
  76. GRB 230625B: CALET Gamma-Ray Burst Monitor detection
  77. GRB 230628E - VLT spectroscopic observations
  78. ZTF23aaoohpy/AT2023lcr: LBT observations
  79. Fermi GRB 230628C: Global MASTER-Net observations report
  80. GRB 230625B: AstroSat CZTI detection
  81. GRB230628E: VLT optical identification of afterglow candidate
  82. GRB 230628E: Swift-XRT refined Analysis
  83. GRB 230628E: Enhanced Swift-XRT position (Correction to name in GCN 34115)
  84. GRB 230628A: Enhanced Swift-XRT position
  85. Fermi GRB 230628D: Global MASTER-Net observations report
  86. LIGO/Virgo/KAGRA S230628ax: Identification of a GW compact binary merger candidate
  87. GRB 230628E: LCOGT Optical Upper Limit
  88. Swift GRB230628.93: Global MASTER-Net observations report
  89. GRB 230628E: Swift detection of a burst
  90. GRB 230628D: BALROG localization (Fermi Trigger 709676556 / GRB 230628849)
  91. GRB 230628D: Fermi GBM Final Real-time Localization
  92. LIGO/Virgo/KAGRA low-significance gravitational wave candidate S230628aj: one counterpart neutrino candidate from IceCube neutrino searches
  93. GRB 230628C: Fermi GBM Final Real-time Localization
  94. GRB 230628B: Swift/BAT-GUANO detection of a burst outside the coded FOV
  95. GRB 230623B: CALET Gamma-Ray Burst Monitor detection
  96. LIGO/Virgo/KAGRA S230516az: GOTO candidate counterpart GOTO23hu ruled out by Zwicky Transient Facility observations
  97. ZTF23aaoohpy /AT2023lcr: TNG NIR detection
  98. GRB 230628A: Fermi GBM Final Localization
  99. LIGO/Virgo/KAGRA S230627c: Additional observations from the Zwicky Transient Facility
  100. GRB 230626A: GRBAlpha detection

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