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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').

17234 results found.

  1. LIGO/Virgo/KAGRA S240428dr: Identification of a GW compact binary merger candidate
  2. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of J-GEM24a
  3. LIGO/Virgo/KAGRA S240422ed: DDOTI Optical Upper Limit for J-GEM24a
  4. EP240426b: AST3-2 optical upper limit
  5. LIGO/Virgo/KAGRA S240422ed: Observations with 1.6m Mephisto
  6. LIGO/Virgo/KAGRA S240422ed: NOT optical observations of EP240426a
  7. EP240426b: EP-WXT detection of a new fast X-ray transient
  8. LIGO/Virgo/KAGRA S240422ed: Archival radio detection of EP240426a
  9. LIGO/Virgo/KAGRA S240422ed: GRANDMA Optical Upper Limits for EP240426a
  10. LIGO/VIRGO/KAGRA S240422ed: Historical variability for EP240426a
  11. EP240426a: YAHPT optical upper limit
  12. XMM-Newton observation of EP240426a
  13. LIGO/Virgo/KAGRA S240426dl: Identification of a GW compact binary merger candidate
  14. GRB 240414A: NOEMA detection
  15. LIGO/Virgo/KAGRA S240422ed: EP240426a possible optical detection
  16. EP240426a: GMG optical upper limit
  17. LIGO/Virgo/KAGRA S240426s: Identification of a GW compact binary merger candidate
  18. LIGO/Virgo/KAGRA S240422ed: Magellan Follow-up Observations of Swift/XRT candidates
  19. LIGO/Virgo/KAGRA S240422ed: Zwicky Transient Facility contuinued observations of S240422ed and candidate analysis
  20. LIGO/Virgo/KAGRA S240422ed: GOTO counterpart search update and AT2024hfx, AT2024hgl observations
  21. LIGO/Virgo/KAGRA S240422ed: PRIME near-infrared observations
  22. LIGO/Virgo/KAGRA S240422ed: 2.5m PRL Telescope follow-up of the Swift/XRT source S240422ed_X190
  23. S240422ed: MeerLICHT/BlackGEM photometry on AT2024hfx and archival ZTF detection
  24. LIGO/Virgo/KAGRA S240422ed: Further near-infrared observations with Subaru/MOIRCS by J-GEM Collaboration
  25. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA and Kilonova-Catcher galaxy targeting observations
  26. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limits for Swift/XRT candidates
  27. GRB 240422A: Glowbug gamma-ray detection
  28. LIGO/Virgo/KAGRA S240422ed: Archival BlackGEM/MeerLICHT detections of AT 2024hdr & AT 2024hdq
  29. LIGO/Virgo/KAGRA S240422ed: Himalayan Chandra Telescope follow-up of the Swift/XRT source S240422ed_X101
  30. LIGO/Virgo/KAGRA S240422ed: No significant counterpart candidates in HAWC observations
  31. LIGO/Virgo/KAGRA S240422ed: Vetting of DECam Candidates Using Real-Time Resources and SAGUARO Infrastructure
  32. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA/FRAM Observations
  33. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  34. LIGO/Virgo S240422ed: Swift-XRT detection of 3 possible counterparts
  35. LIGO/Virgo/KAGRA S240422ed: Early X-ray Upper Limits from EP-WXT for the LVK Sky Localization Region
  36. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of Mag24a
  37. LIGO/Virgo/KAGRA S240422ed: Archival DECaPSs2 observations of the field of Mag24a
  38. LIGO/Virgo/KAGRA S240422ed: NOT J-band upper limit on the Swift/XRT source S240422ed_X61
  39. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Three Potential Electromagnetic Counterparts Reported So Far
  40. GRB 240421B: GRBAlpha detection
  41. LIGO/Virgo/KAGRA S240422ed: SAGUARO upper limits from CSS
  42. LIGO/Virgo/KAGRA S240422ed: Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
  43. LIGO/Virgo/KAGRA S240422ed: Potential Candidates from Magellan galaxy-based search
  44. LIGO/Virgo/KAGRA S240422ed: WINTER J-band upper limits on the Swift/XRT source S240422ed_X61
  45. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam upper limits on the Swift/XRT source S240422ed_X61
  46. LIGO/Virgo/KAGRA S240422ed: GOTO counterpart search
  47. LIGO/Virgo/KAGRA S240422ed: No Counterparts in DDOTI/OAN Optical Observations
  48. GRB 240418A: Swift-BAT refined analysis
  49. LXT240402A/GRB240402B: Chandra X-ray detection
  50. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from ATLAS observations
  51. LIGO/Virgo/KAGRA S240422ed: WINTER near-infrared J-band observations
  52. LIGO/Virgo S240422ed: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  53. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam observations
  54. LIGO/Virgo/KAGRA S240422ed: AstroSat CZTI non-detection and upper limits
  55. LIGO/Virgo/KAGRA S240422ed: Updated Sky localization and EM Bright Classification
  56. LIGO/Virgo/KAGRA S240421ar: Upper limits from Swift/BAT-GUANO
  57. LIGO/Virgo/KAGRA S240422ed: Identification of a GW compact binary merger candidate
  58. GRB 240421A: Glowbug gamma-ray detection
  59. GRB 240414A: radio detection with the VLA
  60. Fermi-LAT gamma-ray observations of IceCube-240419A
  61. GRB 240414A: AMI-LA radio observations
  62. GRB 240414A: LBT optical detection
  63. GRB 240419B : MITSuME Akeno optical upper limits
  64. GRB 240421B: AstroSat CZTI detection
  65. GRB240421B: Zadko Observations
  66. GRB240421B: BOOTES-5/JGT optical upper limit
  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: Xinglong decaying optical counterpart
  72. GRB 240421B: Swift detection of a burst
  73. EP240420a: Nanshan optical counterpart observations
  74. EP240420a: GWAC-F50A optical upper limit
  75. LIGO/Virgo/KAGRA S240421ar: Identification of a GW unmodeled transient candidate
  76. EP240420a: detection of fading X-ray emission with refined position by EP-FXT
  77. EP240420a: NOT optical counterpart candidate and potential host
  78. GRB240419A: Skynet Optical Afterglow Analysis
  79. GRB240418A - Candidate afterglow from NIRES
  80. GRB 240419B: Swift/UVOT Upper Limits
  81. EP240420a: EP-WXT detection of a fast X-ray transient
  82. GRB 240419A: Swift/UVOT Upper Limits
  83. GRB 240419B: optical afterglow from the NOT
  84. GRB 240419B: Enhanced Swift-XRT position
  85. GRB 240418A: Swift/UVOT Upper Limits
  86. GRB 240419A: REM NIR afterglow detection
  87. GRB 240418A: Swift-XRT refined Analysis
  88. GRB 240419B: Swift detection of a burst
  89. GRB 240411B: Swift/UVOT Detection
  90. EP240417a: YAHPT Optical Upper Limits
  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 240411A: GOTO early optical upper limits

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