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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').

22279 results found.

  1. GRB 240516A: Swift/UVOT Upper Limits
  2. EP240518a: possibly identified with a flare star by EP-FXT
  3. GRB 240519A: BALROG localization (Fermi Trigger 737788024 / GRB 240519213)
  4. EP240518a: EP-WXT detection of a new X-ray transient
  5. LIGO/Virgo/KAGRA S240514c: Updated Sky localization
  6. GRB 240516A: Swift-BAT refined analysis
  7. IPN triangulation of GRB 240514B (short)
  8. GRB 240516A: Swift-XRT refined Analysis
  9. GRB 240516A: Fermi GBM Observation
  10. GRB 240511A: Observations from GTC/OSIRIS+
  11. GRB 240516A: Swift detection of a burst
  12. GRB 240511A: radio detection of afterglow candidate
  13. MAXI GRB240514.78: Global MASTER-Net observations report
  14. GRB 240514E: MAXI/GSC detection of a probable afterglow
  15. LIGO/Virgo/KAGRA S240514x: Updated Sky localization
  16. LIGO/Virgo/KAGRA S240515m: Identification of a GW compact binary merger candidate
  17. GRB 240513A: Fermi GBM observation
  18. GRB 240513A: Swift-XRT observations
  19. LIGO/Virgo/KAGRA S240513ei: Updated Sky localization
  20. LIGO/Virgo/KAGRA S240514x: Identification of a GW compact binary merger candidate
  21. LIGO/Virgo/KAGRA S240514c: Identification of a GW compact binary merger candidate
  22. transient: Xinglong Nearby Galaxy Supernova Survey detection of AT2024iss
  23. LIGO/Virgo/KAGRA S240507p: Upper limits from Swift/BAT-GUANO
  24. LIGO/Virgo/KAGRA S240505av: Upper limits from Swift/BAT-GUANO
  25. LIGO/Virgo/KAGRA S240505av: Upper limits from Swift/BAT-GUANO
  26. LIGO/Virgo/KAGRA S240513ei: Identification of a GW compact binary merger candidate
  27. GRB 240511A: Fermi GBM Observation
  28. GRB 240511A: Swift-BAT refined analysis
  29. LIGO/Virgo/KAGRA S240513cx: Coverage and upper limits from MAXI/GSC observations
  30. GRB 240511A: J-band observations with WINTER
  31. Fermi trigger No 737247400: Global MASTER-Net observations report
  32. Fermi trigger No 737168073: Global MASTER-Net observations report
  33. GRB 240511A: Enhanced Swift-XRT position
  34. GRB 240511A : MITSuME Akeno optical upper limits
  35. LIGO/Virgo/KAGRA S240512r: Updated Sky localization and EM Bright Classification
  36. GRB 240511A: Swift-XRT refined Analysis
  37. LIGO/Virgo/KAGRA S240512r: Identification of a GW compact binary merger candidate
  38. GRB 240511A: Swift detection of a burst
  39. LIGO/Virgo/KAGRA S240511i: Updated Sky localization
  40. Fermi trigger No 737111207: Global MASTER-Net observations report
  41. LIGO/Virgo/KAGRA S240511i: Identification of a GW compact binary merger candidate
  42. LIGO/Virgo/KAGRA S240422ed: GMOS-S photometry of J-GEM24a
  43. LIGO/Virgo/KAGRA S240422ed: P200 observations of AT2024hit
  44. LIGO/Virgo/KAGRA S240422ed: Candidates from the latest GW-MMADS DECam Observations
  45. EP240506a: Xinglong optical upper limit
  46. GRB 240504A: Fermi GBM Observation
  47. EP240506a: Archival radio searching
  48. EP240506a: TRT optical upper limit
  49. LIGO/Virgo/KAGRA S240507p: Updated Sky localization and EM Bright Classification
  50. LIGO/Virgo/KAGRA S240422ed: Upper limits from a two-week IceCube neutrino search
  51. EP240506a: Optical upper limit with Kinder observations
  52. IPN triangulation of GRB 240504A
  53. GRB 240502A: 1.3m DFOT Optical upper limit
  54. EP240506a: EP-WXT detection of a new fast X-ray transient
  55. LIGO/Virgo/KAGRA S240507p: Identification of a GW compact binary merger candidate
  56. LIGO/Virgo/KAGRA S240422ed: Additional WINTER near-infrared J-band observations
  57. GRB 240504A: Swift/BAT-GUANO detection of a burst outside the coded FOV
  58. LIGO/Virgo/KAGRA S240505av: Updated Sky localization and EM Bright Classification
  59. LIGO/Virgo/KAGRA S240505av: Identification of a GW compact binary merger candidate
  60. Fermi trigger No 736461232: Global MASTER-Net observations report
  61. GW170817: VLA observations at ~5.5 yrs since merger
  62. GRB 240504A: BALROG localization (Fermi Trigger 736492377 / GRB 240504217)
  63. GRB 240502A: Fermi GBM Observation
  64. GRB 240415A 1.3m DFOT Optical upper limit
  65. LIGO/Virgo/KAGRA S240501an: Updated Sky localization and EM Bright Classification
  66. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  67. GRB 240426A: VZLUSAT-2 detection
  68. GRB 240425A: VZLUSAT-2 detection
  69. MeerKAT Discovery of a Probable Radio Counterpart to EP240414a
  70. GRB 240501B: AstroSat CZTI detection
  71. GRB 240501A: Fermi GBM Final Real-time Localization
  72. GRB 240408B: VZLUSAT-2 detection
  73. GRB 240407A: VZLUSAT-2 detection
  74. LIGO/Virgo/KAGRA S240501an: Identification of a GW compact binary merger candidate
  75. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  76. LIGO/Virgo/KAGRA S240430ca: Identification of a GW compact binary merger candidate
  77. LIGO/Virgo/KAGRA S240422ed: GECKO/7DT ToO observations
  78. Additional DECam GW-MMADS Candidates from three nights of observations
  79. Fermi-LAT gamma-ray observations of IceCube-240424A
  80. LIGO/Virgo/KAGRA S240426s: Updated Sky localization
  81. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limit for EP240426a
  82. LIGO/Virgo/KAGRA S240426dl: Updated Sky localization
  83. LIGO/Virgo/KAGRA S240428dr: Updated Sky localization
  84. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet ToO observations
  85. LIGO/Virgo/KAGRA S240428dr: Identification of a GW compact binary merger candidate
  86. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of J-GEM24a
  87. LIGO/Virgo/KAGRA S240422ed: DDOTI Optical Upper Limit for J-GEM24a
  88. EP240426b: AST3-2 optical upper limit
  89. LIGO/Virgo/KAGRA S240422ed: Observations with 1.6m Mephisto
  90. LIGO/Virgo S240422ed: Swift XRT observation of EP240426a
  91. LIGO/Virgo/KAGRA S240422ed: NOT optical observations of EP240426a
  92. EP240426b: EP-WXT detection of a new fast X-ray transient
  93. LIGO/Virgo/KAGRA S240422ed: Archival radio detection of EP240426a
  94. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfq, AT2024hfr, AT2024hfs, and AT2024hfx
  95. LIGO/Virgo/KAGRA S240422ed: BOOTES-6/DPRT optical upper limits for EP240426a
  96. LIGO/VIRGO/KAGRA S240422ed: Historical variability for EP240426a
  97. GRB 240426A: AstroSat CZTI detection
  98. XMM-Newton observation of EP240426a
  99. LIGO/Virgo/KAGRA S240426dl: Identification of a GW compact binary merger candidate
  100. GRB 240414A: NOEMA detection

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