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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').

15969 results found.

  1. GW170817: VLA observations at ~5.5 yrs since merger
  2. GRB 240504A: Fermi GBM Final Real-time Localization
  3. GRB 240415A 1.3m DFOT Optical upper limit
  4. MeerKAT Discovery of a Probable Radio Counterpart to EP240414a
  5. GRB 240501B: AstroSat CZTI detection
  6. LIGO/Virgo/KAGRA S240501an: Identification of a GW compact binary merger candidate
  7. LIGO/Virgo/KAGRA S240430ca: Identification of a GW compact binary merger candidate
  8. LIGO/Virgo/KAGRA S240422ed: GECKO/7DT ToO observations
  9. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limit for EP240426a
  10. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet ToO observations
  11. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of J-GEM24a
  12. LIGO/Virgo/KAGRA S240422ed: DDOTI Optical Upper Limit for J-GEM24a
  13. EP240426b: AST3-2 optical upper limit
  14. LIGO/Virgo/KAGRA S240422ed: Observations with 1.6m Mephisto
  15. LIGO/Virgo/KAGRA S240422ed: NOT optical observations of EP240426a
  16. EP240426b: EP-WXT detection of a new fast X-ray transient
  17. LIGO/Virgo/KAGRA S240422ed: Archival radio detection of EP240426a
  18. LIGO/VIRGO/KAGRA S240422ed: Historical variability for EP240426a
  19. GRB 240426A: AstroSat CZTI detection
  20. XMM-Newton observation of EP240426a
  21. LIGO/Virgo/KAGRA S240426dl: Identification of a GW compact binary merger candidate
  22. LIGO/Virgo/KAGRA S240422ed: BOOTES-4/MET Optical Upper Limits for EP240426a
  23. GRB 240414A: NOEMA detection
  24. LIGO/Virgo/KAGRA S240422ed: EP240426a possible optical detection
  25. EP240426a: GMG optical upper limit
  26. LIGO/Virgo/KAGRA S240426s: Identification of a GW compact binary merger candidate
  27. LIGO/Virgo/KAGRA S240422ed: Zwicky Transient Facility contuinued observations of S240422ed and candidate analysis
  28. IceCube-240424A: Upper limits from a search for additional neutrino events in IceCube
  29. LIGO/Virgo/KAGRA S240422ed: PRIME near-infrared observations
  30. LIGO/Virgo/KAGRA S240422ed: 2.5m PRL Telescope follow-up of the Swift/XRT source S240422ed_X190
  31. LIGO/Virgo/KAGRA S240422ed: Further near-infrared observations with Subaru/MOIRCS by J-GEM Collaboration
  32. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limits for Swift/XRT candidates
  33. GRB 240421B: Swift-BAT refined analysis
  34. GRB 240422A: Glowbug gamma-ray detection
  35. LIGO/Virgo/KAGRA S240422ed: Archival BlackGEM/MeerLICHT detections of AT 2024hdr & AT 2024hdq
  36. LIGO/Virgo/KAGRA S240422ed: Himalayan Chandra Telescope follow-up of the Swift/XRT source S240422ed_X101
  37. LIGO/Virgo/KAGRA S240422ed: No significant counterpart candidates in HAWC observations
  38. LIGO/Virgo/KAGRA S240422ed: Vetting of DECam Candidates Using Real-Time Resources and SAGUARO Infrastructure
  39. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA/FRAM Observations
  40. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  41. LIGO/Virgo S240422ed: Swift-XRT detection of 3 possible counterparts
  42. LIGO/Virgo/KAGRA S240422ed: Early X-ray Upper Limits from EP-WXT for the LVK Sky Localization Region
  43. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of Mag24a
  44. LIGO/Virgo/KAGRA S240422ed: Archival DECaPSs2 observations of the field of Mag24a
  45. LIGO/Virgo/KAGRA S240422ed: NOT J-band upper limit on the Swift/XRT source S240422ed_X61
  46. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Three Potential Electromagnetic Counterparts Reported So Far
  47. LIGO/Virgo/KAGRA S240422ed: Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
  48. LIGO/Virgo/KAGRA S240422ed: WINTER J-band upper limits on the Swift/XRT source S240422ed_X61
  49. IceCube-240419A: Upper limits from a search for additional neutrino events in IceCube
  50. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from Pan-STARRS observations of the skymap
  51. LIGO/Virgo/KAGRA S240422ed: No Counterparts in DDOTI/OAN Optical Observations
  52. LXT240402A/GRB240402B: Chandra X-ray detection
  53. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from ATLAS observations
  54. LIGO/Virgo/KAGRA S240422ed: WINTER near-infrared J-band observations
  55. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam observations
  56. LIGO/Virgo/KAGRA S240422ed: Updated NED Galaxies in the Localization Volume
  57. LIGO/Virgo/KAGRA S240422ed: AstroSat CZTI non-detection and upper limits
  58. LIGO/Virgo/KAGRA S240422ed: Identification of a GW compact binary merger candidate
  59. GRB 240421A: Glowbug gamma-ray detection
  60. GRB 240414A: radio detection with the VLA
  61. GRB 240414A: AMI-LA radio observations
  62. GRB 240414A: LBT optical detection
  63. GRB 240419B : MITSuME Akeno optical upper limits
  64. GRB 240415B: Swift-XRT observations
  65. GRB 240421B: AstroSat CZTI detection
  66. GRB240421B: Zadko Observations
  67. GRB 240421B: J-band upper limits from WINTER
  68. GRB 240421B: Swift/UVOT Upper Limits
  69. GRB 240421B: Enhanced Swift-XRT position
  70. EP240417a: no counterpart detection by SOAR
  71. EP240420a: TNT upper limit to its optical counterpart
  72. EP240420a: Xinglong decaying optical counterpart
  73. GRB 240421B: Swift detection of a burst
  74. EP240420a: Nanshan optical counterpart observations
  75. EP240420a: GWAC-F50A optical upper limit
  76. LIGO/Virgo/KAGRA S240421ar: Identification of a GW unmodeled transient candidate
  77. EP240420a: detection of fading X-ray emission with refined position by EP-FXT
  78. EP240420a: NOT optical counterpart candidate and potential host
  79. GRB240419A: Skynet Optical Afterglow Analysis
  80. GRB240418A - Candidate afterglow from NIRES
  81. GRB 240419B: Swift/UVOT Upper Limits
  82. EP240420a: EP-WXT detection of a fast X-ray transient
  83. GRB 240419A: Swift/UVOT Upper Limits
  84. GRB 240419B: optical afterglow from the NOT
  85. EP240414a: Near-IR observations with NIRES and WINTER
  86. GRB 240419B: Enhanced Swift-XRT position
  87. GRB 240418A: Swift/UVOT Upper Limits
  88. GRB 240419A: REM NIR afterglow detection
  89. GRB 240419B: Swift detection of a burst
  90. GRB 240411B: Swift/UVOT Detection
  91. GRB 240419A: VLT optical afterglow detection
  92. GRB 240419A: Enhanced Swift-XRT position
  93. EP240416a: J-band observations with WINTER
  94. EP240414a: GMG observation
  95. GRB 240419A: Swift detection of a burst
  96. GRB 240418A: TSHAO Zeiss-1000 optical upper limit
  97. GRB 240418A: NOT optical upper limits
  98. GRB 240418A: Enhanced Swift-XRT position
  99. GRB 240418A: AKO Upper Limit
  100. GRB 240418A: Swift detection of a burst

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