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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').

18758 results found.

  1. GRB 240415A 1.3m DFOT Optical upper limit
  2. GRB 240502C: GOTO possible optical counterpart candidates
  3. LIGO/Virgo/KAGRA S240501an: Updated Sky localization and EM Bright Classification
  4. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  5. MeerKAT Discovery of a Probable Radio Counterpart to EP240414a
  6. GRB 240501B: AstroSat CZTI detection
  7. LIGO/Virgo/KAGRA S240501an: Identification of a GW compact binary merger candidate
  8. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  9. LIGO/Virgo/KAGRA S240430ca: Identification of a GW compact binary merger candidate
  10. LIGO/Virgo/KAGRA S240422ed: GECKO/7DT ToO observations
  11. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limit for EP240426a
  12. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet ToO observations
  13. LIGO/Virgo/KAGRA S240428dr: Identification of a GW compact binary merger candidate
  14. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of J-GEM24a
  15. LIGO/Virgo/KAGRA S240422ed: DDOTI Optical Upper Limit for J-GEM24a
  16. EP240426b: AST3-2 optical upper limit
  17. LIGO/Virgo/KAGRA S240422ed: Observations with 1.6m Mephisto
  18. LIGO/Virgo S240422ed: Swift XRT observation of EP240426a
  19. LIGO/Virgo/KAGRA S240422ed: NOT optical observations of EP240426a
  20. EP240426b: EP-WXT detection of a new fast X-ray transient
  21. LIGO/Virgo/KAGRA S240422ed: Archival radio detection of EP240426a
  22. LIGO/VIRGO/KAGRA S240422ed: Historical variability for EP240426a
  23. GRB 240426A: AstroSat CZTI detection
  24. XMM-Newton observation of EP240426a
  25. LIGO/Virgo/KAGRA S240426dl: Identification of a GW compact binary merger candidate
  26. LIGO/Virgo/KAGRA S240422ed: BOOTES-4/MET Optical Upper Limits for EP240426a
  27. GRB 240414A: NOEMA detection
  28. LIGO/Virgo/KAGRA S240422ed: EP240426a possible optical detection
  29. LIGO/Virgo/KAGRA S240422ed: Continued Magellan Observations
  30. EP240426a: GMG optical upper limit
  31. LVK S240422ed: Further Swift-XRT followup of three sources
  32. LIGO/Virgo/KAGRA S240426s: Identification of a GW compact binary merger candidate
  33. LIGO/Virgo/KAGRA S240422ed: Magellan Follow-up Observations of Swift/XRT candidates
  34. LIGO/Virgo/KAGRA S240422ed: PRIME near-infrared observations
  35. LIGO/Virgo/KAGRA S240422ed: 2.5m PRL Telescope follow-up of the Swift/XRT source S240422ed_X190
  36. LIGO/Virgo/KAGRA S240422ed: Further near-infrared observations with Subaru/MOIRCS by J-GEM Collaboration
  37. LIGO/Virgo/KAGRA S240422ed: Upper limits from GECAM Observations
  38. LIGO/Virgo/KAGRA S240422ed: Magellan Spectrum of GW-MMADS Candidate AT2024hdo Indicates a Type II SN
  39. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limits for Swift/XRT candidates
  40. GRB 240422A: Glowbug gamma-ray detection
  41. LIGO/Virgo/KAGRA S240422ed: Archival BlackGEM/MeerLICHT detections of AT 2024hdr & AT 2024hdq
  42. LIGO/Virgo/KAGRA S240422ed: Himalayan Chandra Telescope follow-up of the Swift/XRT source S240422ed_X101
  43. LIGO/Virgo/KAGRA S240422ed: No significant counterpart candidates in HAWC observations
  44. LIGO/Virgo/KAGRA S240422ed: Vetting of DECam Candidates Using Real-Time Resources and SAGUARO Infrastructure
  45. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA/FRAM Observations
  46. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  47. LIGO/Virgo/KAGRA S240422ed: ATCA follow-up of candidate counterparts
  48. LIGO/Virgo S240422ed: Swift-XRT detection of 3 possible counterparts
  49. LIGO/Virgo/KAGRA S240422ed: Early X-ray Upper Limits from EP-WXT for the LVK Sky Localization Region
  50. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of Mag24a
  51. LIGO/Virgo/KAGRA S240422ed: Continued Imaging of Mag24a
  52. LIGO/Virgo/KAGRA S240422ed: Archival DECaPSs2 observations of the field of Mag24a
  53. LIGO/Virgo/KAGRA S240422ed: Potential Magellan candidates from GCN 36263 are unrelated.
  54. LIGO/Virgo/KAGRA S240422ed: NOT J-band upper limit on the Swift/XRT source S240422ed_X61
  55. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Three Potential Electromagnetic Counterparts Reported So Far
  56. LIGO/Virgo/KAGRA S240422ed: Magellan Detection of a Potential Electromagnetic Counterpart
  57. LIGO/Virgo/KAGRA S240422ed: Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
  58. LIGO/Virgo/KAGRA S240422ed: Potential Candidates from Magellan galaxy-based search
  59. LIGO/Virgo/KAGRA S240422ed: WINTER J-band upper limits on the Swift/XRT source S240422ed_X61
  60. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from Pan-STARRS observations of the skymap
  61. LIGO/Virgo/KAGRA S240422ed: No Counterparts in DDOTI/OAN Optical Observations
  62. LXT240402A/GRB240402B: Chandra X-ray detection
  63. GRB 240419A: Possible ATCA radio detection
  64. GRB 240421B: ATCA radio observations
  65. LIGO/Virgo/KAGRA S240422ed: WINTER near-infrared J-band observations
  66. LIGO/Virgo S240422ed: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  67. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam observations
  68. LIGO/Virgo/KAGRA S240422ed: Magellan Observations
  69. LIGO/Virgo/KAGRA S240422ed: Upper limits from Fermi-GBM Observations
  70. LIGO/Virgo/KAGRA S240422ed: Updated Sky localization and EM Bright Classification
  71. LIGO/Virgo/KAGRA S240422ed: Identification of a GW compact binary merger candidate
  72. LIGO/Virgo/KAGRA S240422ed: Global MASTER-Net observations report
  73. GRB 240421A: Glowbug gamma-ray detection
  74. GRB 240414A: radio detection with the VLA
  75. GRB 240414A: AMI-LA radio observations
  76. GRB 240414A: LBT optical detection
  77. GRB 240419B : MITSuME Akeno optical upper limits
  78. GRB 240415B: Swift-XRT observations
  79. GRB240421B: Zadko Observations
  80. GRB 240421B: J-band upper limits from WINTER
  81. GRB 240421B: Swift/UVOT Upper Limits
  82. GRB 240421B: Enhanced Swift-XRT position
  83. EP240417a: no counterpart detection by SOAR
  84. EP240420a: TNT upper limit to its optical counterpart
  85. EP240420a: Xinglong decaying optical counterpart
  86. GRB 240421B: Swift detection of a burst
  87. EP240420a: Nanshan optical counterpart observations
  88. EP240420a: GWAC-F50A optical upper limit
  89. LIGO/Virgo/KAGRA S240421ar: Identification of a GW unmodeled transient candidate
  90. EP240420a: detection of fading X-ray emission with refined position by EP-FXT
  91. EP240420a: NOT optical counterpart candidate and potential host
  92. GRB240419A: Skynet Optical Afterglow Analysis
  93. GRB240418A - Candidate afterglow from NIRES
  94. GRB 240419B: Swift/UVOT Upper Limits
  95. EP240420a: EP-WXT detection of a fast X-ray transient
  96. GRB 240419A: Swift/UVOT Upper Limits
  97. GRB 240419B: Swift-XRT refined Analysis
  98. GRB 240419B: optical afterglow from the NOT
  99. GRB 240419B: Enhanced Swift-XRT position
  100. GRB 240418A: Swift/UVOT Upper Limits

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