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

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