2022, Liu, Teng, Merloni, Andrea, Wolf, Julien, Salvato, Mara, Reiprich, Thomas H., Comparat, Johan, Arcodia, Riccardo, Lamer, Georg, Georgakakis, Antonis, Dwelly, Tom, Sanders, Jeremy, Buchner, Johannes, Haberl, Frank, Ramos-Ceja, Miriam E., Wilms, Jörn, Nandra, Kirpal, Brunner, Hermann, Brusa, Marcella, Schwope, Axel, Robrade, Jan, Freyberg, Michael, Boller, Thomas, Maitra, Chandreyee, Veronica, Angie, Malyali, Adam

Context. The eROSITA X-ray telescope on board the Spectrum-Roentgen-Gamma (SRG) observatory performed calibration and performance verification (CalPV) observations between September 2019 and December 2019, ahead of the planned 4-yr all-sky surveys. Most of them were deep, pointing-mode observations. Aims. We present here the X-ray catalog detected from the set of extra-galactic CalPV observations released to the public by the German eROSITA consortium, and the multiband counterparts of these X-ray sources. Methods. We developed a source detection method optimized for point-like X-ray sources by including extended X-ray emission in the background measurement. The multiband counterparts were identified using a Bayesian method from the CatWISE catalog. Results. Combining 11 CalPV fields, we present a catalog containing 9515 X-ray sources, whose X-ray fluxes were measured through spectral fitting. CatWISE counterparts are presented for 77% of the sources. Significant variabilities are found in 99 of the sources, which are also presented with this paper. Most of these fields show similar number counts of point sources as typical extragalactic fields, and a few harbor particular stellar populations.

2019, Aguado, D. S., Ahumada, Romina, Almeida, Andrés, Anderson, Scott F., Andrews, Brett H., Anguiano, Borja, Ortíz, Erik Aquino, Aragón-Salamanca, Alfonso, Argudo-Fernández, Maria, Aubert, Marie, Avila-Reese, Vladimir, Seong Hwang, Ho, Ibarra-Medel, Héctor J., Eduardo Jimenez Angel, Camilo, Johnson, Jennifer, Jones, Amy, Jönsson, Henrik, Kinemuchi, Karen, Kollmeier, Juna, Krawczyk, Coleman, Kreckel, Kathryn, Badenes, Carles, Kruk, Sandor, Lacerna, Ivan, Lan, Ting-Wen, Lane, Richard R., Law, David R., Lee, Young-Bae, Li, Cheng, Lian, Jianhui, Lin, Lihwai, Lin, Yen-Ting, Barboza Rembold, Sandro, Lintott, Chris, Long, Dan, Longa-Peña, Penélope, Ted Mackereth, J., de la Macorra, Axel, Majewski, Steven R., Malanushenko, Olena, Manchado, Arturo, Maraston, Claudia, Mariappan, Vivek, Barger, Kat, Marinelli, Mariarosa, Marques-Chaves, Rui, Masseron, Thomas, Masters, Karen L., McDermid, Richard M., Medina Peña, Nicolás, Meneses-Goytia, Sofia, Merloni, Andrea, Merrifield, Michael, Meszaros, Szabolcs, Barrera-Ballesteros, Jorge, Minniti, Dante, Minsley, Rebecca, Muna, Demitri, Myers, Adam D., Nair, Preethi, Correa do Nascimento, Janaina, Newman, Jeffrey A., Nitschelm, Christian, Olmstead, Matthew D, Oravetz, Audrey, Bates, Dominic, Oravetz, Daniel, Ortega Minakata, René A., Pace, Zach, Padilla, Nelson, Palicio, Pedro A., Pan, Kaike, Pan, Hsi-An, Parikh, Taniya, Parker, James, Peirani, Sebastien, Bautista, Julian, Penny, Samantha, Percival, Will J., Perez-Fournon, Ismael, Peterken, Thomas, Pinsonneault, Marc H., Prakash, Abhishek, Raddick, M. Jordan, Raichoor, Anand, Riffel, Rogemar A., Riffel, Rogério, Beaton, Rachael L., Rix, Hans-Walter, Robin, Annie C., Roman-Lopes, Alexandre, Rose, Benjamin, Ross, Ashley J., Rossi, Graziano, Rowlands, Kate, Rubin, Kate H. R., Sánchez, Sebastián F., Sánchez-Gallego, José R., Beers, Timothy C., Sayres, Conor, Schaefer, Adam, Schiavon, Ricardo P., Schimoia, Jaderson S., Schlafly, Edward, Schlegel, David, Schneider, Donald P., Schultheis, Mathias, Seo, Hee-Jong, Shamsi, Shoaib J., Belfiore, Francesco, Shao, Zhengyi, Shen, Shiyin, Shetty, Shravan, Simonian, Gregory, Smethurst, Rebecca J., Sobeck, Jennifer, Souter, Barbara J., Spindler, Ashley, Stark, David V., Stassun, Keivan G., Bernardi, Mariangela, Steinmetz, Matthias, Storchi-Bergmann, Thaisa, Stringfellow, Guy S., Suárez, Genaro, Sun, Jing, Taghizadeh-Popp, Manuchehr, Talbot, Michael S., Tayar, Jamie, Thakar, Aniruddha R., Thomas, Daniel, Bershady, Matthew, Tissera, Patricia, Tojeiro, Rita, Troup, Nicholas W., Unda-Sanzana, Eduardo, Valenzuela, Octavio, Vargas-Magaña, Mariana, Antonio Vázquez-Mata, José, Wake, David, Alan Weaver, Benjamin, Weijmans, Anne-Marie, Beutler, Florian, Westfall, Kyle B., Wild, Vivienne, Wilson, John, Woods, Emily, Yan, Renbin, Yang, Meng, Zamora, Olga, Zasowski, Gail, Zhang, Kai, Zheng, Zheng, Bird, Jonathan, Zheng, Zheng, Zhu, Guangtun, Zinn, Joel C., Zou, Hu, Bizyaev, Dmitry, Blanc, Guillermo A., Blanton, Michael R., Blomqvist, Michael, Bolton, Adam S., Boquien, Médéric, Borissova, Jura, Bovy, Jo, Nielsen Brandt, William, Brinkmann, Jonathan, Brownstein, Joel R., Bundy, Kevin, Burgasser, Adam, Byler, Nell, Cano Diaz, Mariana, Cappellari, Michele, Carrera, Ricardo, Cervantes Sodi, Bernardo, Chen, Yanping, Cherinka, Brian, Doohyun Choi, Peter, Chung, Haeun, Coffey, Damien, Comerford, Julia M., Comparat, Johan, Covey, Kevin, da Silva Ilha, Gabriele, da Costa, Luiz, Sophia Dai, Yu, Damke, Guillermo, Darling, Jeremy, Davies, Roger, Dawson, Kyle, de Sainte Agathe, Victoria, Deconto Machado, Alice, Del Moro, Agnese, De Lee, Nathan, Diamond-Stanic, Aleksandar M., Domínguez Sánchez, Helena, Donor, John, Drory, Niv, du Mas des Bourboux, Hélion, Duckworth, Chris, Dwelly, Tom, Ebelke, Garrett, Emsellem, Eric, Escoffier, Stephanie, Fernández-Trincado, José G., Feuillet, Diane, Fischer, Johanna-Laina, Fleming, Scott W., Fraser-McKelvie, Amelia, Freischlad, Gordon, Frinchaboy, Peter M., Fu, Hai, Galbany, Lluís, Garcia-Dias, Rafael, García-Hernández, D. A., Alberto Garma Oehmichen, Luis, Antonio Geimba Maia, Marcio, Gil-Marín, Héctor, Grabowski, Kathleen, Gu, Meng, Guo, Hong, Ha, Jaewon, Harrington, Emily, Hasselquist, Sten, Hayes, Christian R., Hearty, Fred, Hernandez Toledo, Hector, Hicks, Harry, Hogg, David W., Holley-Bockelmann, Kelly, Holtzman, Jon A., Hsieh, Bau-Ching, Hunt, Jason A. S.

Twenty years have passed since first light for the Sloan Digital Sky Survey (SDSS). Here, we release data taken by the fourth phase of SDSS (SDSS-IV) across its first three years of operation (2014 July–2017 July). This is the third data release for SDSS-IV, and the 15th from SDSS (Data Release Fifteen; DR15). New data come from MaNGA—we release 4824 data cubes, as well as the first stellar spectra in the MaNGA Stellar Library (MaStar), the first set of survey-supported analysis products (e.g., stellar and gas kinematics, emission-line and other maps) from the MaNGA Data Analysis Pipeline, and a new data visualization and access tool we call "Marvin." The next data release, DR16, will include new data from both APOGEE-2 and eBOSS; those surveys release no new data here, but we document updates and corrections to their data processing pipelines. The release is cumulative; it also includes the most recent reductions and calibrations of all data taken by SDSS since first light. In this paper, we describe the location and format of the data and tools and cite technical references describing how it was obtained and processed. The SDSS website (www.sdss.org) has also been updated, providing links to data downloads, tutorials, and examples of data use. Although SDSS-IV will continue to collect astronomical data until 2020, and will be followed by SDSS-V (2020–2025), we end this paper by describing plans to ensure the sustainability of the SDSS data archive for many years beyond the collection of data.

2020, Ahumada, Romina, Prieto, Carlos Allende, Almeida, Andrés, Anders, Friedrich, Anderson, Scott F., Andrews, Brett H., Anguiano, Borja, Arcodia, Riccardo, Armengaud, Eric, Aubert, Marie, Avila, Santiago, Garcia, Rafael A., García-Hernández, D.A., Oehmichen, Luis Alberto Garma, Ge, Junqiang, Maia, Marcio Antonio Geimba, Geisler, Doug, Gelfand, Joseph, Goddy, Julian, Gonzalez-Perez, Violeta, Grabowski, Kathleen, Avila-Reese, Vladimir, Green, Paul, Grier, Catherine J., Guo, Hong, Guy, Julien, Harding, Paul, Hasselquist, Sten, Hawken, Adam James, Hayes, Christian R., Hearty, Fred, Hekker, S., Badenes, Carles, Hogg, David W., Holtzman, Jon A., Horta, Danny, Hou, Jiamin, Hsieh, Bau-Ching, Huber, Daniel, Hunt, Jason A. S., Chitham, J. Ider, Imig, Julie, Jaber, Mariana, Balland, Christophe, Angel, Camilo Eduardo Jimenez, Johnson, Jennifer A., Jones, Amy M., Jönsson, Henrik, Jullo, Eric, Kim, Yerim, Kinemuchi, Karen, Kirkpatrick IV, Charles C., Kite, George W., Klaene, Mark, Barger, Kat, Kneib, Jean-Paul, Kollmeier, Juna A., Kong, Hui, Kounkel, Marina, Krishnarao, Dhanesh, Lacerna, Ivan, Lan, Ting-Wen, Lane, Richard R., Law, David R., Le Goff, Jean-Marc, Barrera-Ballesteros, Jorge K., Leung, Henry W., Lewis, Hannah, Li, Cheng, Lian, Jianhui, Lin, Lihwai, Long, Dan, Longa-Peña, Penélope, Lundgren, Britt, Lyke, Brad W., Ted Mackereth, J., Basu, Sarbani, MacLeod, Chelsea L., Majewski, Steven R., Manchado, Arturo, Maraston, Claudia, Martini, Paul, Masseron, Thomas, Masters, Karen L., Mathur, Savita, McDermid, Richard M., Merloni, Andrea, Bautista, Julian, Merrifield, Michael, Mészáros, Szabolcs, Miglio, Andrea, Minniti, Dante, Minsley, Rebecca, Miyaji, Takamitsu, Mohammad, Faizan Gohar, Mosser, Benoit, Mueller, Eva-Maria, Muna, Demitri, Beaton, Rachael L., Muñoz-Gutiérrez, Andrea, Myers, Adam D., Nadathur, Seshadri, Nair, Preethi, Nandra, Kirpal, do Nascimento, Janaina Correa, Nevin, Rebecca Jean, Newman, Jeffrey A., Nidever, David L., Nitschelm, Christian, Beers, Timothy C., Noterdaeme, Pasquier, O’Connell, Julia E., Olmstead, Matthew D., Oravetz, Daniel, Oravetz, Audrey, Osorio, Yeisson, Pace, Zachary J., Padilla, Nelson, Palanque-Delabrouille, Nathalie, Palicio, Pedro A., Benavides, B. Izamar T., Pan, Hsi-An, Pan, Kaike, Parker, James, Paviot, Romain, Peirani, Sebastien, Ramŕez, Karla Peña, Penny, Samantha, Percival, Will J., Perez-Fournon, Ismael, Pérez-Ràfols, Ignasi, Bender, Chad F., Petitjean, Patrick, Pieri, Matthew M., Pinsonneault, Marc, Poovelil, Vijith Jacob, Povick, Joshua Tyler, Prakash, Abhishek, Price-Whelan, Adrian M., Raddick, M. Jordan, Raichoor, Anand, Ray, Amy, Bernardi, Mariangela, Rembold, Sandro Barboza, Rezaie, Mehdi, Riffel, Rogemar A., Riffel, Rogério, Rix, Hans-Walter, Robin, Annie C., Roman-Lopes, A., Román-Zúñiga, Carlos, Rose, Benjamin, Ross, Ashley J., Bershady, Matthew, Rossi, Graziano, Rowlands, Kate, Rubin, Kate H. R., Salvato, Mara, Sánchez, Ariel G., Sánchez-Menguiano, Laura, Sánchez-Gallego, José R., Sayres, Conor, Schaefer, Adam, Schiavon, Ricardo P., Beutler, Florian, Schimoia, Jaderson S., Schlafly, Edward, Schlegel, David, Schneider, Donald P., Schultheis, Mathias, Schwope, Axel, Seo, Hee-Jong, Serenelli, Aldo, Shafieloo, Arman, Shamsi, Shoaib Jamal, Bidin, Christian Moni, Shao, Zhengyi, Shen, Shiyin, Shetrone, Matthew, Shirley, Raphael, Aguirre, Víctor Silva, Simon, Joshua D., Skrutskie, M.F., Slosar, Anže, Smethurst, Rebecca, Sobeck, Jennifer, Bird, Jonathan, Sodi, Bernardo Cervantes, Souto, Diogo, Stark, David V., Stassun, Keivan G., Steinmetz, Matthias, Stello, Dennis, Stermer, Julianna, Storchi-Bergmann, Thaisa, Streblyanska, Alina, Stringfellow, Guy S., Bizyaev, Dmitry, Stutz, Amelia, Suárez, Genaro, Sun, Jing, Taghizadeh-Popp, Manuchehr, Talbot, Michael S., Tayar, Jamie, Thakar, Aniruddha R., Theriault, Riley, Thomas, Daniel, Thomas, Zak C., Blanc, Guillermo A., Tinker, Jeremy, Tojeiro, Rita, Toledo, Hector Hernandez, Tremonti, Christy A., Troup, Nicholas W., Tuttle, Sarah, Unda-Sanzana, Eduardo, Valentini, Marica, Vargas-González, Jaime, Vargas-Magaña, Mariana, Blanton, Michael R., Vázquez-Mata, Jose Antonio, Vivek, M., Wake, David, Wang, Yuting, Weaver, Benjamin Alan, Weijmans, Anne-Marie, Wild, Vivienne, Wilson, John C., Wilson, Robert F., Wolthuis, Nathan, Boquien, Médéric, Wood-Vasey, W. M., Yan, Renbin, Yang, Meng, Yèche, Christophe, Zamora, Olga, Zarrouk, Pauline, Zasowski, Gail, Zhang, Kai, Zhao, Cheng, Zhao, Gongbo, Borissova, Jura, Zheng, Zheng, Zheng, Zheng, Zhu, Guangtun, Zou, Hu, Bovy, Jo, Brandt, W. N., Brinkmann, Jonathan, Brownstein, Joel R., Bundy, Kevin, Bureau, Martin, Burgasser, Adam, Burtin, Etienne, Cano-Díaz, Mariana, Capasso, Raffaella, Cappellari, Michele, Carrera, Ricardo, Chabanier, Solène, Chaplin, William, Chapman, Michael, Cherinka, Brian, Chiappini, Cristina, Doohyun Choi, Peter, Chojnowski, S. Drew, Chung, Haeun, Clerc, Nicolas, Coffey, Damien, Comerford, Julia M., Comparat, Johan, da Costa, Luiz, Cousinou, Marie-Claude, Covey, Kevin, Crane, Jeffrey D., Cunha, Katia, Ilha, Gabriele da Silva, Dai, Yu Sophia, Damsted, Sanna B., Darling, Jeremy, Davidson, James W., Davies, Roger, Dawson, Kyle, De, Nikhil, de la Macorra, Axel, De Lee, Nathan, Queiroz, Anna Bárbara de Andrade, Deconto Machado, Alice, de la Torre, Sylvain, Dell’Agli, Flavia, du Mas des Bourboux, Hélion, Diamond-Stanic, Aleksandar M., Dillon, Sean, Donor, John, Drory, Niv, Duckworth, Chris, Dwelly, Tom, Ebelke, Garrett, Eftekharzadeh, Sarah, Davis Eigenbrot, Arthur, Elsworth, Yvonne P., Eracleous, Mike, Erfanianfar, Ghazaleh, Escoffier, Stephanie, Fan, Xiaohui, Farr, Emily, Fernández-Trincado, José G., Feuillet, Diane, Finoguenov, Alexis, Fofie, Patricia, Fraser-McKelvie, Amelia, Frinchaboy, Peter M., Fromenteau, Sebastien, Fu, Hai, Galbany, Lluís

This paper documents the 16th data release (DR16) from the Sloan Digital Sky Surveys (SDSS), the fourth and penultimate from the fourth phase (SDSS-IV). This is the first release of data from the Southern Hemisphere survey of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2); new data from APOGEE-2 North are also included. DR16 is also notable as the final data release for the main cosmological program of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and all raw and reduced spectra from that project are released here. DR16 also includes all the data from the Time Domain Spectroscopic Survey and new data from the SPectroscopic IDentification of ERosita Survey programs, both of which were co-observed on eBOSS plates. DR16 has no new data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library "MaStar"). We also preview future SDSS-V operations (due to start in 2020), and summarize plans for the final SDSS-IV data release (DR17).

2022, Zeltyn, Grisha, Trakhtenbrot, Benny, Eracleous, Michael, Runnoe, Jessie, Trump, Jonathan R., Stern, Jonathan, Shen, Yue, Hernández-García, Lorena, Bauer, Franz E., Yang, Qian, Dwelly, Tom, Ricci, Claudio, Green, Paul, Anderson, Scott F., Assef, Roberto J., Guolo, Muryel, MacLeod, Chelsea, Davis, Megan C., Fries, Logan, Gezari, Suvi, Grogin, Norman A., Homan, David, Koekemoer, Anton M., Krumpe, Mirko, LaMassa, Stephanie, Liu, Xin, Merloni, Andrea, Martínez-Aldama, Mary Loli, Schneider, Donald P., Temple, Matthew J., Brownstein, Joel R., Ibarra-Medel, Hector, Burke, Jamison, Pellegrino, Craig, Kollmeier, Juna A.

We report the discovery of a new “changing-look” active galactic nucleus (CLAGN) event, in the quasar SDSS J162829.17+432948.5 at z = 0.2603, identified through repeat spectroscopy from the fifth Sloan Digital Sky Survey (SDSS-V). Optical photometry taken during 2020-2021 shows a dramatic dimming of Δg ≈ 1 mag, followed by a rapid recovery on a timescale of several months, with the ≲2 month period of rebrightening captured in new SDSS-V and Las Cumbres Observatory spectroscopy. This is one of the fastest CLAGN transitions observed to date. Archival observations suggest that the object experienced a much more gradual dimming over the period of 2011-2013. Our spectroscopy shows that the photometric changes were accompanied by dramatic variations in the quasar-like continuum and broad-line emission. The excellent agreement between the pre- and postdip photometric and spectroscopic appearances of the source, as well as the fact that the dimmest spectra can be reproduced by applying a single extinction law to the brighter spectral states, favor a variable line-of-sight obscuration as the driver of the observed transitions. Such an interpretation faces several theoretical challenges, and thus an alternative accretion-driven scenario cannot be excluded. The recent events observed in this quasar highlight the importance of spectroscopic monitoring of large active galactic nucleus samples on weeks-to-months timescales, which the SDSS-V is designed to achieve.