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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. LIGO/Virgo S230521k: Global MASTER-Net observations report
  2. LIGO/Virgo/KAGRA S230521k: Zwicky Transient Facility observations
  3. GRB 230518B: VZLUSAT-2 detection
  4. Fermi Gamma-ray Burst Monitor trigger 706338208/230521211 is not a GRB
  5. LIGO/Virgo S230520ae: Global MASTER-Net observations report
  6. Fermi trigger No 706328428: Global MASTER-Net observations report
  7. IPN triangulation of GRB 230518A (short)
  8. Fermi trigger No 706331483: Global MASTER-Net observations report
  9. Fermi trigger No 706317104: Global MASTER-Net observations report
  10. GRB 230520A: CALET Gamma-Ray Burst Monitor detection
  11. GRB 230521A: Fermi GBM Final Real-time Localization
  12. LIGO/Virgo/KAGRA S230520ae: Identification of a GW compact binary merger candidate: End-to-End Test
  13. GRB 230520B is not a GRB
  14. GRB 230520B: Fermi GBM Final Real-time Localization
  15. LIGO/Virgo/KAGRA S230520ae: Upper limits from IceCube neutrino search
  16. LIGO/Virgo/KAGRA S230518h: ATCA follow-up of candidate counterparts
  17. LIGO/Virgo/KAGRA S230518h: GECKO tiling observations with KMTNet
  18. LIGO/Virgo/KAGRA S230518h: Swift/UVOT Upper Limits for Swope candidates: SSS23a, SSS23b and SSS23c
  19. GRB 230520A: MAXI/GSC detection
  20. LIGO/Virgo/KAGRA S230518h: ATLAS observations of the skymap
  21. LIGO/Virgo/KAGRA S230518h: Swope Search and Candidate Counterpart Identification
  22. GRB 230518A: Fermi GBM Observation
  23. LIGO/Virgo/KAGRA S230518h: Upper limits from Konus-Wind observations
  24. LIGO/Virgo S230518h: AGILE/MCAL observations
  25. GRB 230518A: Swift/BAT-GUANO detection
  26. LIGO/Virgo S230518h: Swift XRT observations, 8 X-ray sources
  27. LIGO/Virgo/KAGRA S230518h: Coverage and upper limits from MAXI/GSC observations
  28. GRB 230518A: Fermi GBM Final Real-time Localization
  29. Fermi Gamma-ray Burst Monitor trigger 706068974/230518095 is not a GRB
  30. LIGO/Virgo/Kagra S230518h: NED Galaxies in the Localization Volume
  31. LIGO/Virgo/KAGRA S230518h: AstroSat CZTI non-detection and upper limits
  32. LIGO/Virgo/KAGRA S230518h: Upper limits from Fermi-GBM Observations
  33. LIGO/Virgo S230518h: Global MASTER-Net observations report
  34. LIGO/Virgo/KAGRA S230518h: Updated Sky localization and EM Bright Classification
  35. LIGO/Virgo S230518h: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  36. LIGO/Virgo S230518h: Upper limits from IceCube neutrino search
  37. LIGO/Virgo/KAGRA S230518h: Identification of a GW compact binary merger candidate
  38. GRB 230513A: Zwicky Transient Facility continuous observations of a Fermi Short GRB (Trigger 705709044)
  39. GRB 230510B: GRBAlpha detection
  40. Fermi trigger No 706014351: Global MASTER-Net observations report
  41. GRB 230517A: BALROG localization (Fermi Trigger 706014351 / GRB 230517462)
  42. Improved IPN triangulation of GRB 230512A
  43. GRB 230517A: Fermi GBM Final Real-time Localization
  44. GRB 230510B: Fermi GBM detection
  45. Fermi trigger No 705952199: Global MASTER-Net observations report
  46. GRB 230516A: Fermi GBM Final Real-time Localization
  47. IPN triangulation of GRB 230511D (short)
  48. IPN triangulation of GRB 230512A
  49. GRB 230513A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 705709044)
  50. GRB 230512A: Nanshan/NEXT non-detection of GRB afterglow candidate
  51. GRB 230512A: Zwicky Transient Facility non-detection of GRB afterglow candidate
  52. GRB 230512A: Liverpool Telescope observations
  53. GRB 230512A: GIT non detection of afterglow candidate
  54. GRB 230512A: Kitab possible afterglow candidate
  55. GRB 230512A: GRBAlpha detection
  56. GRB 230510A: GRBAlpha detection
  57. GRB 230513A: Fermi GBM Final Real-time Localization
  58. Fermi trigger No 705565670: Global MASTER-Net observations report
  59. Fermi-LAT gamma-ray observations of IceCube-230511A
  60. GRB 230510A: OHP/T193 and OHP/T120 optical observations
  61. GRB 230512A: Swift-XRT observations
  62. IceCube-230511A: Upper limits from a search for additional neutrino events in IceCube
  63. IceCube-Cascade 230511A: Upper limits from a search for additional neutrino events in IceCube
  64. GRB 230512A: GIT optical follow-up ZTF candidates
  65. GRB 230512A: Fermi GBM detection
  66. GRB 230512A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 705565670)
  67. GRB 230430A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 704533643)
  68. GRB 230511D: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 705537623)
  69. GRB 230512A: Tiled Swift observations
  70. GRB 230512A: Fermi-LAT detection
  71. GRB 230512A: AstroSat CZTI detection
  72. GRB 230512A: Fermi GBM Final Localization
  73. GRB 230510A: GIT optical upper limits
  74. GRB 230510A: LCOGT Optical Upper Limit
  75. GRB 230511D: Fermi GBM Final Real-time Localization
  76. GRB 230510A: Swift/UVOT Observations
  77. IceCube-230511A: IceCube observation of a high-energy neutrino candidate
  78. GRB 230510B: AstroSat CZTI detection
  79. GRB 230511C: Fermi GBM Final Localization
  80. Fermi trigger No 705503315: Global MASTER-Net observations report
  81. GRB 230511B: Fermi GBM Final Real-time Localization
  82. Fermi trigger No 705496510: Global MASTER-Net observations report
  83. GRB 230511A: Fermi GBM Final Real-time Localization
  84. GRB 230510A: Fermi GBM detection
  85. Fermi trigger No 705446499: Global MASTER-Net observations report
  86. GRB 230510A: Gaoyazi/GOT optical upper limit
  87. GRB 230510B: CALET Gamma-Ray Burst Monitor detection
  88. GRB 230510A: CALET Gamma-Ray Burst Monitor detection
  89. GRB 230510A: Nanshan/NEXT optical afterglow detection
  90. GRB 230510B: MAXI/GSC detection
  91. GRB 230510B: Fermi GBM Final Real-time Localization
  92. GRB 230506B: Fermi GBM detection
  93. GRB 230510A: Swift-XRT refined Analysis
  94. GRB 230510A: Enhanced Swift-XRT position
  95. GRB 230506C: Fermi GBM detection
  96. Fermi trigger No 705413051: Global MASTER-Net observations report
  97. Fermi Gamma-ray Burst Monitor trigger 230510133/705381054 is not a GRB
  98. GRB 230510A: Swift detection of a burst
  99. GRB 230510A: Fermi GBM Final Real-time Localization
  100. GRB 230506B: Swift/UVOT further analysis

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