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GCN Circulars are now part of the new GCN! See news and announcements

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').
  1. GRB 230520B is not a GRB
  2. GRB 230520B: Fermi GBM Final Real-time Localization
  3. LIGO/Virgo/KAGRA S230520ae: Upper limits from IceCube neutrino search
  4. LIGO/Virgo/KAGRA S230518h: ATCA follow-up of candidate counterparts
  5. LIGO/Virgo/KAGRA S230518h: GECKO tiling observations with KMTNet
  6. LIGO/Virgo/KAGRA S230518h: Swift/UVOT Upper Limits for Swope candidates: SSS23a, SSS23b and SSS23c
  7. GRB 230520A: MAXI/GSC detection
  8. LIGO/Virgo/KAGRA S230518h: ATLAS observations of the skymap
  9. LIGO/Virgo/KAGRA S230518h: Swope Search and Candidate Counterpart Identification
  10. GRB 230518A: Fermi GBM Observation
  11. LIGO/Virgo/KAGRA S230518h: Upper limits from Konus-Wind observations
  12. LIGO/Virgo S230518h: AGILE/MCAL observations
  13. GRB 230518A: Swift/BAT-GUANO detection
  14. LIGO/Virgo S230518h: Swift XRT observations, 8 X-ray sources
  15. LIGO/Virgo/KAGRA S230518h: Coverage and upper limits from MAXI/GSC observations
  16. GRB 230518A: Fermi GBM Final Real-time Localization
  17. Fermi Gamma-ray Burst Monitor trigger 706068974/230518095 is not a GRB
  18. LIGO/Virgo/Kagra S230518h: NED Galaxies in the Localization Volume
  19. LIGO/Virgo/KAGRA S230518h: AstroSat CZTI non-detection and upper limits
  20. LIGO/Virgo/KAGRA S230518h: Upper limits from Fermi-GBM Observations
  21. LIGO/Virgo S230518h: Global MASTER-Net observations report
  22. LIGO/Virgo/KAGRA S230518h: Updated Sky localization and EM Bright Classification
  23. LIGO/Virgo S230518h: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  24. LIGO/Virgo S230518h: Upper limits from IceCube neutrino search
  25. LIGO/Virgo/KAGRA S230518h: Identification of a GW compact binary merger candidate
  26. GRB 230513A: Zwicky Transient Facility continuous observations of a Fermi Short GRB (Trigger 705709044)
  27. GRB 230510B: GRBAlpha detection
  28. Fermi trigger No 706014351: Global MASTER-Net observations report
  29. GRB 230517A: BALROG localization (Fermi Trigger 706014351 / GRB 230517462)
  30. Improved IPN triangulation of GRB 230512A
  31. GRB 230517A: Fermi GBM Final Real-time Localization
  32. GRB 230510B: Fermi GBM detection
  33. Fermi trigger No 705952199: Global MASTER-Net observations report
  34. GRB 230516A: Fermi GBM Final Real-time Localization
  35. IPN triangulation of GRB 230511D (short)
  36. IPN triangulation of GRB 230512A
  37. GRB 230513A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 705709044)
  38. GRB 230512A: Nanshan/NEXT non-detection of GRB afterglow candidate
  39. GRB 230512A: Zwicky Transient Facility non-detection of GRB afterglow candidate
  40. GRB 230512A: Liverpool Telescope observations
  41. GRB 230512A: GIT non detection of afterglow candidate
  42. GRB 230512A: Kitab possible afterglow candidate
  43. GRB 230512A: GRBAlpha detection
  44. GRB 230510A: GRBAlpha detection
  45. GRB 230513A: Fermi GBM Final Real-time Localization
  46. Fermi trigger No 705565670: Global MASTER-Net observations report
  47. Fermi-LAT gamma-ray observations of IceCube-230511A
  48. GRB 230510A: OHP/T193 and OHP/T120 optical observations
  49. GRB 230512A: Swift-XRT observations
  50. IceCube-230511A: Upper limits from a search for additional neutrino events in IceCube
  51. IceCube-Cascade 230511A: Upper limits from a search for additional neutrino events in IceCube
  52. GRB 230512A: GIT optical follow-up ZTF candidates
  53. GRB 230512A: Fermi GBM detection
  54. GRB 230512A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 705565670)
  55. GRB 230430A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 704533643)
  56. GRB 230511D: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 705537623)
  57. GRB 230512A: Tiled Swift observations
  58. GRB 230512A: Fermi-LAT detection
  59. GRB 230512A: AstroSat CZTI detection
  60. GRB 230512A: Fermi GBM Final Localization
  61. GRB 230510A: GIT optical upper limits
  62. GRB 230510A: LCOGT Optical Upper Limit
  63. GRB 230511D: Fermi GBM Final Real-time Localization
  64. GRB 230510A: Swift/UVOT Observations
  65. IceCube-230511A: IceCube observation of a high-energy neutrino candidate
  66. GRB 230510B: AstroSat CZTI detection
  67. GRB 230511C: Fermi GBM Final Localization
  68. Fermi trigger No 705503315: Global MASTER-Net observations report
  69. GRB 230511B: Fermi GBM Final Real-time Localization
  70. Fermi trigger No 705496510: Global MASTER-Net observations report
  71. GRB 230511A: Fermi GBM Final Real-time Localization
  72. GRB 230510A: Fermi GBM detection
  73. Fermi trigger No 705446499: Global MASTER-Net observations report
  74. GRB 230510A: Gaoyazi/GOT optical upper limit
  75. GRB 230510B: CALET Gamma-Ray Burst Monitor detection
  76. GRB 230510A: CALET Gamma-Ray Burst Monitor detection
  77. GRB 230510A: Nanshan/NEXT optical afterglow detection
  78. GRB 230510B: MAXI/GSC detection
  79. GRB 230510B: Fermi GBM Final Real-time Localization
  80. GRB 230506B: Fermi GBM detection
  81. GRB 230510A: Swift-XRT refined Analysis
  82. GRB 230510A: Enhanced Swift-XRT position
  83. GRB 230506C: Fermi GBM detection
  84. Fermi trigger No 705413051: Global MASTER-Net observations report
  85. Fermi Gamma-ray Burst Monitor trigger 230510133/705381054 is not a GRB
  86. GRB 230510A: Swift detection of a burst
  87. GRB 230510A: Fermi GBM Final Real-time Localization
  88. GRB 230506B: Swift/UVOT further analysis
  89. GRB 230506C: T193-OHP MISTRAL tentative redshift
  90. GRB 230506C: SAO RAS optical observations
  91. GRB 230307A: JWST second-epoch observations
  92. IceCube-230506A: Upper limits from a search for additional neutrino events in IceCube
  93. Fermi-LAT gamma-ray observations of IceCube-230506A
  94. GRB 230506C: Swift-XRT refined Analysis
  95. GRB 230506C: Swift-BAT refined analysis
  96. GRB 230506B: Swift-BAT refined analysis
  97. GRB 230506C: spectro-imaging observations of the optical afterglow with T193-OHP
  98. GRB 230506B: LCOGT Optical Upper Limits
  99. GRB 230506C: Swift/UVOT Upper Limits
  100. GRB 230506C: NUTTelA-TAO / BSTI Early Optical Limits
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